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Ecology of the entomopathogenic fungi Beauveria bassiana and Metarhizium anisopliae in temperate agroecosystems: Potential for conservation biological control
Abstract
It is increasingly recognized that the biodiversity in agroecosystems deliver significant ecosystem services to agricultural production such as biological control of pests. Entomopathogenic fungi, specifically the anamorphic taxa Beauveria bassiana and Metarhizium anisopliae, Hypocreales (Ascomycota), are among the natural enemies of pests in agroecosystems and the fungi are candidates for future conservation biological control in temperate regions. Conservation biological control is a biological control strategy in which farming practices and environmental manipulations are adopted to enhance the living conditions for specific natural enemies of pests. However, in order to manipulate the environment for the benefit of populations of the entomopathogens, knowledge of fundamental aspects of the ecology of the fungi considered is necessary. This knowledge is still scarce despite the large bulk of recent research into inoculation and inundation biological control with these fungi. Here, we review the current knowledge of the ecology of indigenous populations of B. bassiana and M. anisopliae in agroecosystems of temperate regions, primarily Europe and North America. We suggest anamorphic life cycles of B. bassiana and M. anisopliae in these regions based on the literature of their natural occurrence and distribution in agroecosystems, population dynamics, and interactions with other organisms, environmental factors, and agronomical practices.
... For example, increasing relative humidity by modifying crop irrigation techniques or regimes or through other crop-management practices can increase fungal activity (Pell, Hannam and Steinkraus, 2010). Regarding soil disturbances, reduced till or no-till practices have been found to favour soil-dwelling entomopathogens in several crops, although this may be mediated by host abundance (Meyling and Eilenberg 2007;Pell, Hannam and Steinkraus, 2010). Burning crop residues is thought to negatively affect microorganisms, both in crop residues and in the soil, while mulching may favour them by increasing organic matter and humidity, and also benefit some soil predators (Stirling, Halpin and Bell, 2011;Timper, 2014). ...
... Options include using selective or specific products, appropriate timing of pesticide application, reducing application rates or areas, using specific formulations or methods, and using pesticides with low persistence (Hajek, 2004;Gurr, Altieri and Wratten, eds., 2004;Torres and Bueno, 2018;Zaviezo et al., 2021). The approach is relevant for arthropod natural enemies, entomopathogens and plant pathogen antagonists, but by far the bulk of research is on the first of these three groups (Mietkiewski, Pell and Clark, 1997;Klingen and Haukeland, 2006;Meyling and Eilenberg, 2007;Pell, Hannam and Steinkraus, 2010;Timper, 2014). ...
... In the case of conservation biological control by entomopathogens, emphasis has been given to aphid control with Entomophthorales fungi (Meyling and Eilenberg 2007). Natural-enemy diversity and biological control have also been studied at the landscape scale (Bianchi, Booij and Tscharntke, 2006;Tscharntke et al., 2008;Shackelford et al., 2013;Grez et al., 2014;Landis, 2017;Perović et al., 2018;Martin et al., 2019). ...
Interest in the use of microbial and invertebrate biological control agents (BCAs) in food and agriculture is increasing. Growing concerns about the impact of pesticide use on biodiversity and human health – and increasing demand for products from biodiversity-friendly production systems, including organic systems – have led to growing interest in alternative methods of pest control, including particularly the use of microbial and invertebrate BCAs.
... The soil environment is an important reservoir of a large diversity of fungal species, with various ecological functions (Shah and Pell 2003;Meyling and Eilenberg 2007). Entomopathogenic fungi (EPF) play an important role in pest insect population regulation, and are generally considered to be promising biological control agents of insect pests (Charnley and St Leger 1991;St Leger et al. 1996;Gilbert and Gill 2010). ...
... Entomopathogenic fungi (EPF) play an important role in pest insect population regulation, and are generally considered to be promising biological control agents of insect pests (Charnley and St Leger 1991;St Leger et al. 1996;Gilbert and Gill 2010). EPF are among the natural enemies that cause epizootics in arthropod species in agroecosystems, by means of inducing lethal infection in their host insects, which helps regulate pest populations (Leger et al. 1992;Roy et al. 2006;Meyling and Eilenberg 2007;Vega et al. 2009;Shahid et al. 2012). ...
... Vuill. (Hypocreales: Cordycipitaceae) and M. anisopliae, which are among the most well-studied fungal species within agroecosystems, have been used to control several insect pests in some countries (Chase et al. 1986;St Leger et al. 1992;Wraight et al. 2000;Meyling and Eilenberg 2007). ...
Entomopathogenic fungi (EPF) are cosmopolitan soil borne pathogens that cause epizootics in various insect orders. EPF isolates of Metarhizium brunneum and M. pinghaense have shown the potential for use as biological agents of important agricultural insect pests. The aim of the current study was to test for the persistence of M. brunneum and M. pinghaense on apple bark over a period of three weeks, under laboratory conditions. Apple bark was sprayed with conidial suspensions of both fungi, at a standard infective conidial concentration of 107 conidia/ml. The persistence, or survival, of the conidia on apple bark was measured using codling moth larvae (CM) (Cydia pomonella) and females of woolly apple aphid (WAA) (Eriosoma lanigerum) as indicator species. The results showed that conidia of M. pinghaense can induce mortality of insect pests through contact with an EPF-treated substrate, with mortality of 39% to 82% for WAA over a period of 10 days post application, and with mortality of 3% to 68% for CM over a period of 7 days, after application to apple bark. Further evaluation showed that the conidia of M. pinghaense persisted longer on apple bark, up to 63%, than did M. brunneum, up to 11%, three weeks post application of the conidial suspensions. The study provides insights into the potential persistence of fungal isolates on apple bark over time post application. Further evaluation of the persistence of the isolates on apple bark under both glasshouse and field conditions should be conducted.
... This may be related to changes in the climatic conditions of geographic areas, agricultural practices, or sampling timing (Ali-Shtayeh et al. 2002). The soil environment is usually the classical isolation zone for EPF species in the Hypocreales, and various EPF species can be found in both arable soils and more natural environments (Meyling and Eilenberg 2007). Keller et al. (2003) reported that M. anisopliae is common in arable soils and meadows with higher density. ...
... While Vänninen (1996) reported that M. anisopliae was isolated more frequently from the southern parts of Finland, and tillage did not adversely affect the isolation of this fungus. Steenberg (1995) suggested that in Danish soil, M. anisopliae is more common in open areas than in shady habitats (Meyling and Eilenberg 2007). Similarly , Bidochka et al. (1998) reported that M. anisopliae is more common in agricultural areas compared to forests in Canada, and B. bassiana is mostly found in shady and natural habitats such as forests. ...
A total of 250 soil samples were taken from the forest, hazelnut, kiwi, vegetable, and meadow-rangeland areas in the coastal regions of Ordu province, Turkey. Entomopathogenic fungi were isolated from these soil samples using the Galleria-bait method. Eighty-five fungal isolates were isolated from these soil samples, after which they were morphologically and molecularly identified. After morphological characterization, 64 out of 85 isolates were identified molecularly. Based on the molecular characterization results, twenty-three out of the 64 isolates were Beauveria bassiana (35.94%), 11 isolates were Metarhizium brunneum (17.19%), 8 isolates were Metarhizium anisopliae (12.5%), 6 isolates were Metarhizium robertsii (9.38%), 4 isolates were Purpureocillium lilacinum (6.25%), 4 isolates were Clonostachys rogersoniana (6.25%), 3 isolates were Fusarium solani (4.69%), 1 isolate was Clonostachys rossmaniae (1.56%), 1 isolate was Aspergillus flavus (1.56%), 1 isolate was Cordyceps cicadae (1.56%), 1 isolate was Cordyceps fumosorosea (1.56%), and 1 isolate was Fusarium oxysporum (1.56%). In the coastal area of Ordu province, the most common entomopathogen fungal genus is Metarhizium followed by Beauveria bassiana.
... For aeration, the 1-l containers were filled with soil samples leaving 10 cm space on top. All soil samples were baited for EPF after collection, and in the case of the soil samples that were dry, distilled water was used to moisten the soil to maintain enough humidity during the baiting process (Meyling and Eilenberg 2007;Goble et al. 2010). Ten larvae of both Galleria mellonella L. (Lepidoptera: Pyralidae) and Tenebrio molitor (Coleoptera: Tenebrionidae) were added to the surface of the soil samples in the plastic containers which were then closed and incubated in the dark at a controlled room temperature of ± 25 °C (Zimmermann 1986;Meyling 2007). ...
... Collected EPF were all hypocrealean fungal species, which are among the well-known EPF species that are common components of the soil environment microbiota with a cosmopolitan distribution (Chandler et al. 1997;Zimmermann 2007). Among the collected EPF isolates were C. fumosorosea, B. bassiana and M. anisopliae species complex isolates, which are well-known to cause mycosis within various taxa of arthropod, and virtually in all insect orders (Chase et al. 1986; Zimmermann 1986; Meyling and Eilenberg 2007). Similar observations to those that were made in the current study were made in a study conducted by Abaajeh and Nchu (2015), in which fungal isolates belonging to six entomopathogenic fungal species were also successfully isolated from soil samples collected in the Western Cape province, using similar baiting techniques, where collected EPF species included both M. robertsii and P. lilacinum. ...
Eriosoma lanigerum (Hausmann) (Hemiptera: Aphididae), woolly apple aphid (WAA) is an important pest on apples globally and a key pest of apple production in South Africa. The aphid has developed some level of resistance against several chemical insecticides. Entomopathogenic fungi (EPF) have been identified as promising biological control agents against a wide array of insect pests. The main aim of this study was to conduct a survey in local apple orchards in the Western Cape province for EPF and to use isolates to test the susceptibility of WAA under optimum laboratory conditions. Soil samples were collected from apple orchards and EPF, baited and isolated using larvae of Galleria mellonella and Tenebrio molitor. Six EPF species: Beauveria bassiana, Cordyceps fumosorosea, Metarhizium brunneum, M. pinghaense, M. robertsii and Purpureocillium lilacinum were identified from the soil samples. The results from bioassays showed that Metarhizium robertsii and M. pinghaense isolates were the most effective with an average percentage mortality of > 90%. Metarhizium brunneum also proved to be effective when used against the insect with an average percentage mortality of > 80%, while B. bassiana and C. fumosorosea were the least effective with average percentage mortality of 52% and 48%, respectively. The LT50 and LT90 of M. robertsii (2.12; 4.19) and M. pinghaense (2.05; 4.45) showed to require similar mortality time in days of E. lanigerum. The results obtained in the study have provided an insight into the diversity of EPF species across apple orchards of the Western Cape and shown the efficacy of the Metarhizium isolates as potential biological control agents of the WAA.
... For aeration, the 1-l containers were filled with soil samples leaving 10 cm space on top. All soil samples were baited for EPF after collection, and in the case of the soil samples that were dry, distilled water was used to moisten the soil to maintain enough humidity during the baiting process (Meyling and Eilenberg 2007;Goble et al. 2010). Ten larvae of both Galleria mellonella L. (Lepidoptera: Pyralidae) and Tenebrio molitor (Coleoptera: Tenebrionidae) were added to the surface of the soil samples in the plastic containers which were then closed and incubated in the dark at a controlled room temperature of ± 25 °C (Zimmermann 1986;Meyling 2007). ...
... Collected EPF were all hypocrealean fungal species, which are among the well-known EPF species that are common components of the soil environment microbiota with a cosmopolitan distribution (Chandler et al. 1997;Zimmermann 2007). Among the collected EPF isolates were C. fumosorosea, B. bassiana and M. anisopliae species complex isolates, which are well-known to cause mycosis within various taxa of arthropod, and virtually in all insect orders (Chase et al. 1986; Zimmermann 1986; Meyling and Eilenberg 2007). Similar observations to those that were made in the current study were made in a study conducted by Abaajeh and Nchu (2015), in which fungal isolates belonging to six entomopathogenic fungal species were also successfully isolated from soil samples collected in the Western Cape province, using similar baiting techniques, where collected EPF species included both M. robertsii and P. lilacinum. ...
Eriosoma lanigerum (Hausmann) (Hemiptera: Aphididae), woolly apple aphid (WAA) is an important pest on apples globally and a key pest of apple production in South Africa. The aphid has developed some level of resistance against several chemical insecticides. Entomopathogenic fungi (EPF) have been identified as promising biological control agents against a wide array of insect pests. The main aim of this study was to conduct a survey in local apple orchards in the Western Cape province for EPF and to use isolates to test the susceptibility of WAA under optimum laboratory conditions. Soil samples were collected from apple orchards and baited using larvae of Galleria mellonella and Tenebrio molitor to isolate EPF. Six EPF species: Beauveria bassiana, Cordyceps fumosorosea, Metarhizium brunneum, M. pinghaense, M. robertsii and Purpureocillium lilacinum were identified from the soil samples. The results from bioassays showed that Metarhizium robertsii and M. pinghaense isolates were the most effective with an average percentage mortality of > 90%. Metarhizium brunneum also proved to be effective when used against the insect with an average percentage mortality of > 80%, while B. bassiana and C. fumosorosea were the least effective with average percentage mortality of 52% and 48%, respectively. The lethal time required to kill 50% and 90% of the colony at a concentration of 107 conidia/ml over five days, LT50 and LT90, of M. robertsii (2.12 and 4.19 days, respectively) and M. pinghaense (2.05 and 4.45 days, respectively) showed to require similar mortality time in days of E. lanigerum. The results obtained in the study have provided an insight into the diversity of EPF species across apple orchards of the Western Cape and shown the efficacy of the Metarhizium isolates as potential biological control agents of the E. lanigerum.
... In its native area, e.g., Mexico, FAW has been found infected naturally by EPFs (Cruz-Avalos et al. 2019). In agroecosystems, EPFs, especially the anamorphic taxa Beauveria bassiana and Metarhizium anisopliae (Ascomycota: Hypocreales), are among the natural enemies of several insect pests that have been potential candidates for conservation biological control (Meyling and Eilenberg 2007). ...
... This was observed in this study when building phylograms where the 1969 isolate of B. bassiana was found in the same group as the other species of the genus Beauveria. According to Meyling and Eilenberg (2007), the existence of two unrelated clades may partly explain the high genetic diversity within B. bassiana. This entomopathogenic species is not a specific host but an opportunist one capable of attacking a wide range of insects belonging to diverse taxa (Rehner and Buckley 2005). ...
Background The fall armyworm (FAW), Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae), poses a threat to the food security of populations in sub-Saharan Africa because of its damage to maize crops. As alternative to the use of hazardous pesticides, microbial control is one of the most promising sustainable approaches adopted to limit the damages caused by S. frugiperda. The sampling targeted mainly larvae of S. frugiperda; however, during the survey, cadavers of earwig found on the same sampling sites were also collected and involved in the study. Cadavers of targeted insects, with and without sign of fungal infection, were sampled from 3 localities in eastern DR Congo. Culture of fungal isolates was performed in selective Sabouraud dextrose agar media.
Results Morphological study of fungal features such as conidia (shape and size) and conidiophores showed that the isolates were from the genus Beauveria. Conidial measurements were highly variable and ranged from 2.4 to 3.6 μm in length and from 1.75 to 3.0 μm in width. Molecular characterization and phylogenetic analysis of the 2 Beauveria isolates based on DNA sequencing of ITS-5.8S region confirmed that both isolates belong to Beauveria bassiana. The 2 isolates of B. bassiana P5E (OP419735.1) and KA14 (OP419734.1) were isolated from cadavers of FAW and earwig, respectively. The alignment with different sequences of B. bassiana from different continent showed that P5E belonged to the same clade of previous isolates reported from Iran and Mexico, while KA14 was with the same clade as isolates from Kenya and China.
Conclusion To our knowledge, this is the first study reporting the occurrence of B. bassiana infecting FAW and earwig in eastern DR Congo and in Africa.
Keywords Spodoptera frugiperda, Beauveria bassiana, Epizooty, Earwig, Molecular characterization
... One of the important factors that can affect the diversity and distribution of the entomopathogenic fungal species is the type of crop or vegetation where the insect is present (Leger 2008, Schneider et al. 2012. Meyling & Eilenberg (2007) noted that the plant diversity is positively correlated with the natural occurrence of entomopathogenic fungi. ...
Fungal diversity associated with Bemisia tabaci (Hemip-tera: Aleyrodidae) on cucumber and comparative effectiveness of bioassay methods in identifying the most virulent entomopath-ogenic fungi.-Sydowia 75: 269-282. Bemisia tabaci is a serious pest of cucumber, in Iraq, that reduces the income of farmers by high losses in yield. This study aimed to identify entomopathogenic fungi from whitefly cadavers and to evaluate their relative frequency and various structural attributes. The suitability of two bioassay methods and the virulence of two entomopathogenic fungal species were evaluated for management of B. tabaci under greenhouse condition. Out of the 16 fungal species isolated from the whitefly cadavers, only two species were confirmed microscopically as known entomopathogenic species: Mucor sp. and Purpureocillium lilacinum with a relative frequency of 8.65 and 5.82 %, respectively. Results of the principle component analysis indicated that the first two PCs explained 99.30 %. Three factors had a significant positive correlation with relative frequency of the fungal species which are species diversity (r= 0.983), Simpson's concentration of dominance (r= 0.951) and equitability of evenness (r= 0.996). The greatest mortality effect on B. tabaci nymphs and adults due to P. lilacinum and Mucor sp. was recorded on the 7thday after inoculation, with an average mortality more than 60 % (with concentration of 106 conidia/ml). P. lilacinum and Mucor sp. were significantly twice as virulent to nymphs than to adults. However, no significant differences were observed between mortality rates of the two methods. To control B. tabaci nymphs and adults in the field within IPM strategies, we recommend more trials in order to analyze the real efficacy of P. lilacinum and Mucor sp. under field conditions.
... Isolating different APF might offer potential for their use in biotechnology for their medicinal properties [5,38] and in agriculture, given their virulence and specificity in pristine forests. However, it should be noted that these fungi may be more sensitive to changes in humidity, temperature and UV light in open agroecosystems [39]. ...
The ecological role and potential management of arthropod-pathogenic fungi (APF) in neotropical forests are of great importance, but they are still little studied. The present study achieves a first estimation of diversity patterns, structure and local ecology of APF in the Amazonian forests of the Cusco and Madre de Dios regions in southern Peru. We sampled 39 localities in five basins, examining 277 specimens, four families and 20 genera with 82 species (40% morphospecies). The most diverse families were Cordycipitaceae with 51 species and Ophiocordicipitaceae (22). Cusco obtained a greater diversity: four families, 18 genera and 58 morphospecies, with the Urubamba and Amarumayu basins having greater diversity (31 and 20 species); for the Madre de Dios basin, there was 28 species. In both regions, the richness values were corroborated by Fisher’s Alpha and Chao-1 indexes, the latter identifies Amarumayu and Araza with maximum values. The NMDS analysis showed a good pattern of separation of the two APF communities, although an important group was shared. Elevation was identified as the environmental variable with the strongest influence on diversity and structure. The dominance analysis identified Ophiocordyceps australis and Paraisaria amazonica as hyperdominant, due to their density and distribution. The local ecological patterns in Pongo de Qoñec show that the richness of entomopathogens is largely favored by low understory light, associated with pristine or little-impacted habitats. We conclude that this first approximation of the knowledge of the high diversity of APF in southern Peru is still insufficient, but it demonstrates the importance of their conservation and represents enormous potential for sustainable management.
... Entomopathogenic fungus are important components for pest regulation in ecosystem, mostly to control arthropod population (Meyling & Eilenberg, 2007). Some studies revealed the entomopathogenic fungi roles as insect population regulators and other arthropod pests including grasshoppers, locusts, and other hemipterans (Roberts & St. Leger, 2004;Zimmermann, 2007). ...
Entomopathogenic fungi are important component for regulation of pests in ecosystem. Isaria fumosorosea, as one of the entomopathogenic fungi, was reported to successfully controlled the outbreaks of forest defoliators attacked larch (Larix kaempferi) plantation in Furano, Japan and beech (Fagus crenata) forest in Hachimantai, Japan. Instead of semi-cultured method, in this paper, a culture-independent method based on DNA using qPCR was developed for specific detection and quantification of I. fumosorosea directly from soil DNA extract using specific primer. The primer IFU5821F/IFU6061R was designed and found to be the best primer pair for I. fumosorosea. Standard soil DNA was obtained with strong relationship and good fitting with five levels (R2= 0.989, E = 0.58). I. fumosorosea could not be detected from all soil samples which was possibility caused by low density of the fungi. The qPCR was likely a rapid and specific method to detect the fungus from soil.
... Microbial control (MC) using entomopathogenic fungus is an ecologically favorable, human innocuous, and long-term pest control strategy (Zimmermann, 2007). Entomopathogenic fungi are a viable pest management strategy in organic and conventional farming systems (Lomer et al., 2001;Meyling & Eilenberg, 2007;Flores et al., 2013). ...
... The virulence of an entomopathogenic fungus can be determined by the LT50, the average lethal time from exposure to the pathogen to the death of an infected insect (FAO/IAEA 2019). The virulence of each entomopathogenic fungus species depends on the host from which the fungus is isolated and the susceptibility of the target for which it is evaluated (Hajek and St. Leger 1994;De la Rosa et al. 2002;Roberts and Leger 2004;Rehner 2005;Meyling and Eilenberg 2007;Zélé et al. 2020). Differences between entomopathogenic fungal strains and their effects on pest species may result from host-pathogen relationships (Lecuona 1996;FAO/IAEA 2019). ...
Tetranychus urticae is an important pest worldwide. The auto-dissemination of spores of entomopathogenic fungi from an infected individual to conspecifics may be important for controlling pests that can build high populations. The current study was carried out to determine the auto-dissemination of the entomopathogenic fungus Cordyceps fumosorosea strain PFs-1 (Priority®) between T. urticae females. The study consisted of four experiments. First, the efficacy of entomopathogenic fungus bioassays was assessed in Petri dishes (experiment 1) and on potted bean plants (experiment 2). In the auto-dissemination trials (experiments 3 and 4, in Petri dishes and on potted plants, respectively), contaminated adult females (1–5) were released among uncontaminated females (10 individuals). All experiments were carried out separately, and observations were made on days 3, 5, and 7. In exp. 1, the control was different from Priority on all observation days. In exp. 2, the average number of surviving individuals in the control was significantly higher than in the Priority treatment. In the auto-dissemination experiments, as the number of contaminated individuals increased, the mortality rate of uncontaminated individuals also increased, in exp. 3 (Petri dishes) on all observation days, and in exp. 4 (potted plants) only on days 5 and 7. The median lethal time (LT50) decreased as the number of individuals contaminated with Priority increased in both Petri dish and pot trials. Consequently, the effectiveness of biological control may increase with the occurrence of indirect contamination from infected to uncontaminated individuals.
... These microorganisms have attracted remarkable attention for their usage in biological control programs of insect pests in both agriculture and forestry as environmentally safe agents (Lacey et al., 2015;Strasser et al., 2010). Among these fungi, Beauveria bassiana (Balsamo) Vuillemin and Metarhizium anisopliae (Metschn) Sorokin are the most studied fungi in terms of commercial production (Goettel et al., 2005;Meyling and Eilenberg, 2007). ...
Biological control potential of Beauveria bassiana and Paecilomyces species against Culex quinquefasciatus was investigated. The two fungi have been reported to exhibit insecticidal activity against mosquito and other insects. Beauveria bassiana and Paecilomyces spp was isolated from soil using soil suspension method with selective isolation media procedures. Bioassay was made to determine their efficacy against 4th instar larvae of C. quinquefasciatus. Three different concentrations; 1x10 7 , 1x10 6 and 1x10 5 conidia/ml were made and tested. Results showed that mortality increased with increase in conidia concentration and exposure time. The mortality recorded in lowest dose of 10 5 conidia/ml was 70% and 50% in Beauveria bassiana and Paecilomyces spp respectively, and again 80% and 60% mortality were recorded at dose of 10 6 conidia/ml. The highest dose level of 10 7 conidia/ml of Beauveria bassiana and Paecilomyces spp isolate caused high mortality up to 90% and 80% respectively. The lethal concentration causing 50% mortality (LC50) of 4 th instars larvae of C. quinquefasciatus was also varied according to concentration of spores and duration of exposure. The result showed that LC50 values of Beauveria bassiana isolate after 24-, 48-, 72-and 96-Hours exposure time were 3.9 ×10 8 , 2.6 x 10 6 , 2.0 x 10 4 and 1.6x10 6 conidia/ml. Similarly, LC50 values Paecilomyces spp isolate after 24,46,72,96-Hours exposure were 6.3×10 8 , 4.8 x 10 7 , 3.0 x 10 4 and 2.3 x 10 6 conidia/ml respectively. These results indicated that B. bassiana and Paecilomyces spp isolated is pathogenic to immature stage of C. quinquefasciatus and although not as efficient as chemical larvicides and could be suggested for development as a biological control for mosquito management so as to avoid concerns associated with chemical larvicides
... To test this hypothesis, experiments were performed using sweet pepper (Capsicum annuum L.; Solanaceae) and the fungal strains Beauveria bassiana ARSEF 3097 (Hypocreales: Cordycipitaceae) and Trichoderma harzianum T22 (Hypocreales: Hypocreaceae). While Trichoderma constitutes a well-documented soilborne plant-beneficial organism (Kubheka and Ziena 2022;Woo et al. 2022), the beneficial effects of endophytic colonization by soildwelling entomopathogenic fungi like B. bassiana (Meyling and Eilenberg 2007; Quesada Moraga 2020) on plant performance have only been demonstrated more recently (Gange et al. 2019;Jaber and Ownley 2018;Vega 2018). Further, the southern green stink bug Nezara viridula L. (Heteroptera: Pentatomidae) was used as study species. ...
AimsPlant-beneficial fungi play an important role in enhancing plant growth and protecting plants from biotic and abiotic stresses. However, context-dependency of such effects and differences among fungi often lead to inconsistent results that hamper their widespread use. Here, we investigated the effect of plant-beneficial fungi on plant growth and herbivore resistance, and how effects are mediated by fertilization.Methods
Sweet pepper (Capsicum annuum L.) plants were root-inoculated with the plant-beneficial fungi Beauveria bassiana ARSEF 3097 and Trichoderma harzianum T22 and grown in a low-nutrient potting mix, with or without additional nutrients. Plant growth and herbivore resistance against the southern green stink bug (Nezara viridula L.) were compared between fungal treatments and fertilization levels by measuring several growth traits and quantifying feeding damage and plant defense-related gene expression.ResultsFertilization significantly increased plant growth, but at the same time made plants more susceptible to herbivory. Irrespective of fertilization, T. harzianum stimulated growth and reduced feeding damage (number of leaf punctures), while B. bassiana only enhanced growth. For both strains, fungal inoculation generally increased the expression of marker genes involved in salicylic acid- and jasmonic acid-dependent defense responses upon herbivory, but this was less pronounced for salicylic acid-dependent defense signaling under fertilization.Conclusions
We conclude that fungal inoculation improved plant growth and generally elicited a stronger defense response to stink bug feeding. Accordingly, plant damage was reduced by T. harzianum. Overall these results show that plant-beneficial fungi have the potential to promote plant growth and reduce feeding damage, irrespective of fertilization.
... However, it cannot be understated the impact that cleaner control methods will have on improving safety and sustainability standards for agricultural productivity, the effects of which would be even more profound for small PICs. Biodiversity plays a significant role in agricultural production systems with services such as pollination and biological control sometimes dependent on how healthy a system surrounding production systems are (Meyling and Eilenberg, 2007). However, modern production systems rely on mono clonal propagation methodologies that aim to reduce complexities and simplify the growing process resulting in an almost complete loss of biodiversity (Gauthier et al., 1981). ...
Global population is slated to hit 9 billion by then turn of the mid-century and continue on an upward trajectory until the end. Modern agriculture has allowed for sustenance of large numbers of people with the use of chemical control methods and fertilizers driven by the developments of the green revolution. However, many experts now believe that gains from the green revolution have run their course and new methodologies in sustainable production must be applied. The strain on agricultural productivity is further exacerbated as a result of climate change. The Pacific is home to some countries most at risk by this phenomenon. Limited arable land resources coupled with rising input costs and the unsustainable effect of these synthetic inputs on limited land resources necessitates the development and use of organic alternatives. Climate change facilitates an increase in the spread of pests and diseases while modern travel and logistics efforts mean a higher probability of an organism slipping through biosecurity checks on borders. Pacific agriculture has yet to truly embrace an organic approach to pest and disease control in a commercial setting and this may also be attributed to a lack of distinct studies on feasibility. This paper attempts to provide some insight into the place that Biocontrol agents (BCAs) can have in a sustainable Pacific production system.
... We used a strain of Metharizium anisopliae to infect colonies of C. mauritanica. This generalist fungal entomopathogen is globally distributed and known to be pathogenic to various insects worldwide, including many ant species Meyling and Eilenberg 2007). Fungus was cultured on a Malt Extract Agar medium (MEA; Sigma-Aldrich 70,145) for six days at 25 °C. ...
Group genetic diversity is usually associated with a reduced risk of disease outbreak and a slower rate of pathogen transmission. In social insects, multiple mating by queens (polyandry) evolved several times albeit reducing worker’s inclusive fitness. One major hypothesis suggests that polyandry has been selected for to mitigate the risk of outbreak thanks to increased genetic diversity within colonies. We investigated this hypothesis in the ant Cataglyphis mauritanica, in which nestmate workers are produced by several clonal, single-mated queens. Using natural colonies, we correlated genetic diversity with worker survival to a fungal entomopathogen. We further tested whether workers from different paternal lineages (but a common maternal genome) show differential resistance in experimentally single- or multiple-patriline groups, and whether an increased number of patrilines in a group improved disease resistance. We show that workers from distinct patrilines vary in their resistance to a pathogen in single-patriline colonies, but the difference among patrilines disappears when they are mixed in multiple-patriline colonies. Furthermore, pathogen resistance was affected by the number of patrilines in a group, with two- and three-patriline groups being more resistant than single-patriline groups. However, resistance did not differ between groups made of two and three patrilines; similarly, it was not associated with genetic diversity in natural colonies. Overall, our results suggest that collective disease defenses might homogenize workers’ resistance from different patrilines and, thereby, stabilize colony resistance.
Significance Statement
The occurrence of multiple breeders in insect societies has been hypothesized to be selected for because increased within-colony genetic diversity reduces the risk of severe outbreaks. We show that nestmate workers from distinct paternal lineages vary in their resistance to pathogens when reared in single-patriline groups. However, this difference disappears when workers are mixed in multiple-patriline groups. These results suggest that multiple mating by queens dilutes the deleterious consequences of a single patriline producing only susceptible offspring, rather than directly enhancing pathogen resistance.
... and Beauveria spp. in Shoa. Ayele et al. (2020) distributions of entomopathogens are influenced by environmental factors such as geographic location, climatic conditions, habitat type, cropping system, and soil properties (Meyling and Eilenberg 2007;Quezada-Moraga et al. 2007;Sookar et al. 2008). ...
A field survey was conducted to determine the distribution and intensity of major faba bean diseases, and
association of faba bean gall (FBG) epidemics with different biophysical factors in Amhara region,
Ethiopia during the 2019 and 2020 main growing seasons. Three Zones were selected based on their
production potential and accessibility. Five hundred forty three faba bean fields were inspected.
Chocolate spot, aschochyta blight and FBG were 100% prevalent though there were variations in mean
incidence and percent severity index (PSI) across districts. Maximum FBG PSI was recorded at Bassona
Werena (33.4%) district whereas the lowest was from Moretina Jiru (9.41%) district. On the other hand,
Farta (36.25 and 19.95)% showed maximum chocolate spot and ascochyta blight PSI, respectively.
Logistic regression was used to analyse the association of FBG intensity with biophysical factors. High
(>40%) FBG incidence and PSI were strongly associated with 2020 main growing season, North Shoa
Zone, Lay Gayint, Tache Gayint, Farta and Desse Zuria districts, high altitude, large farm size, podding
growth stage, low to medium plant population, di-coat weed type, high to medium weed population,
vertisol and cambisol soil types, fields without fertilizer application, cultivating barley, potato, wheat and
triticale as a precursor crop, highly sloppy fields and sole cropping system. Chocolate spot, ascochyta
blight and FBG were highly important diseases identified. The study revealed the need of designing cost
effective integrated management practices targeting important biophysical factors showing a strong
association with FBG disease.
... and Beauveria spp. in Shoa. Ayele et al. (2020) distributions of entomopathogens are influenced by environmental factors such as geographic location, climatic conditions, habitat type, cropping system, and soil properties (Meyling and Eilenberg 2007;Quezada-Moraga et al. 2007;Sookar et al. 2008). ...
Potato is the most important crop and Potato late blight disease is the major constraint of potato production in Ethiopia. Field experiment was conducted at Meket and Wadla during the 2018 and 2019 cropping season to evaluate salts for the management of potato late blight and to select cost effective management options. The experiment had seven treatments; Sodium bicarbonate, Sodium benzoate, Sodium carbonate, Potassium Chloride, Calcium chloride, Ridomil and control. The treatments were arranged in randomized complete block design with three replications. Significant differences were observed among treatments on disease, yield and yield components. Foliar application of salts and Ridomil fungicide treatments reduced late blight disease, with a corresponding increase in tuber yields of potatoes. Among salts, the highest total tuber yield (23.59 and 22.02 t ha-1) was recorded from sodium bicarbonate and the lowest (13.9 and 14.1 t ha-1) was recorded from unsprayed treatment at Meket and Wadla in 2019 respectively. The highest marginal rate of return (2852.08%) was obtained from Ridomil, followed by 2634.33% by sodium bicarbonate. Therefore, in addition to synthetic fungicides sodium bicarbonate was used as a foliar spray that can reduce the disease pressure and is recommended to protect potatoes from late blight disease.
... The infective structures of EPF belonging to the Hypocreales order are passively dispersed to the environment via dead insects. This distribution occurs with factors such as wind and rain (Meyling & Eilenberg, 2007). The spores of fungi of the Entomophthoralean order are actively released under hydrostatic pressure and spread with the wind. ...
Chemical control methods are mostly preferred in the control of pests that cause qualitative and quantitative losses in stored products instead of physical or biological control applications. The increasing consumer response to pesticide use and the insect resistance to many pesticides have reversed this situation and interest in biological control has increased. Entomopathogenic fungi (EPF) are biological control agents that are safer than synthetic pesticides. EPF play major roles in the natural regulation of many insect and mite species. Sustainable Biological Control with EPF could make a substantial contribution to the control of storage pests. When storage pests’ interactions are complex with EPF, we can notice both positive and negative impacts. EPF disrupts the host cuticle and proliferates as hyphae in the hemolymph, secreting toxins responsible for the death of host insects. Subsequent saprophytic growth leads to the production of fungal spores that can reinfect other hosts. For a successful infection, the fungus must be effective on the host's defense system. In order to determine the optimum conditions of myco-insecticides in biological control programs, specific research is required to understand the interaction between EPF, host insects, crops, and their environment. This review includes an overview of EPF, its host defense mechanism, pathogenicity, infection occurrence, the potential for use, and prospects. Furthermore, this review extensively investigates the contribution of EPF to biological control in sustainable agricultural practices.
... The use of synthetic chemical insecticides with a high control efficacy of A. ipsilon has a negative influence on human health, agriculture, and natural enemies because of chemical residue, environmental pollution, and the development of insect resistance to these chemical insecticides (Batta, 2016;Fernandes et al., 2010). It is now commonly recognised that the biodiversity of agroecosystems contributes significant ecosystem services to agricultural productivity, such as biological pest management (Entomopathogenic fungus, Beauveria bassiana), (Meyling and Eilenberg, 2007). ...
... and Beauveria spp. in Shoa. Ayele et al. (2020) distributions of entomopathogens are influenced by environmental factors such as geographic location, climatic conditions, habitat type, cropping system, and soil properties (Meyling and Eilenberg 2007;Quezada-Moraga et al. 2007;Sookar et al. 2008). ...
Participatory variety selection followed by pre scaling up of the preferred varieties has been recognized as an alternative approach to increase varietal adoption. On farm researcher managed participatory variety selection was conducted with nine improved and one local varieties using randomized complete block design with three replications in Bure zuria district in 2017 and 2018. The combined analysis of variance showed significant variation among the tested varieties in grain yield and other measured parameters. “Estub” gave the highest yield (2.1 t ha-1) followed by “Dagem” (1.81 t ha-1) with 91% and 70% yield advantage over the local variety , respectively. These varieties also got the highest farmers’ preference score indicating they fulfilled farmers’ varietal selection criteria in the study area. The farmers’ varietal selection criterion were uniform maturity, high grain and biomass yield, best adaptability, long panicle, high tillering capacity, white seed color, medium maturity, and soft injera making quality. The correlation between farmers’ preference and breeders’ selection was positive but low in magnitude indicating the difference the groups in traits of preference used for variety selection. Farmers’ preferred varieties were prescaled up in 2019 and 2020. The wide dissemination of the two selected varieties in the district indicated that the varieties met farmers’ traits of preference and the effectiveness of participatory variety selection approach for varietal adoption. In conclusion, farmers’ participatory variety selection in each agro ecology is a pre-requisite for adoption and scaling up of the released varieties.
... and Beauveria spp. in Shoa. Ayele et al. (2020) distributions of entomopathogens are influenced by environmental factors such as geographic location, climatic conditions, habitat type, cropping system, and soil properties (Meyling and Eilenberg 2007;Quezada-Moraga et al. 2007;Sookar et al. 2008). ...
Tef is one of the most important staple food crops in the Amhara Region. It takes the largest share in annual area coverage. However, the productivity of the crop is far below its genetic potential. Limited availability of stable and high yielding improved varieties and wider use of low yielding farmers’ cultivars are the major factors constraining tef productivity. A regional variety trial was conducted to identify and release stable and high yielding tef genotypes with desirable agronomic and morphological traits. Eighteen tef recombinant inbred lines (RIL) along with standard (Abay) and local checks were evaluated at Adet, Mota, Bichena, Takusa and Alem Ketema districts in Amhara region during the 2018 and 2019 main rainy cropping seasons using randomized complete block design with three replications. Data on grain yield and yield related traits were collected. Combined analysis of variance was carried out. The yield data was also graphically visualized for interpreting genotype by environment interaction (GEI) using GGE biplot analysis. The combined analysis of variance across 10 environments (E) showed highly significant variation for all measured traits. The highest mean grain yield (2.21 t ha-1) was recorded by G-14 which excelled the standard check by 10%. GEI showed significant variations for most of the traits examined, IPC1 and IPC2 accounted for 34.52 % and 19.58%, respectively. The polygon tool of the biplot suggested the existence of six winning genotypes (G), (G-5,G-14, G-19,G-20,G-1,G-11) and three mega environments. However multiple years and locations’ data are required to validate the existence of mega environments in the major tef growing areas of Amhara region. The environment relationship biplot indicated that E4 (Takusa-2018) and E9(Takusa-1019) were highly discriminating environments meaning they provide information about the genotypes. G-14 was the winning genotype in the sector where 80% of the total test environments fall and it was also found closer to the ideal genotype. In conclusion, the combined analysis for all measured parameters and GGE biplot analysis for grain yield indicated that G-14 (DZ-01-974 X GA-10-3(RILL-104) was found high yielding and stable as compared to the other genotypes included in the study. It also showed moderate tolerance to lodging and has white seeded grain that can fetch high market prices. Taking the merits of the genotype into consideration, it has been officially released with a local name “Takusa” for major tef growing areas of the Amhara region and similar agroecologies in the country.
... Entomopathogenic fungi (EPF) in the genera Beauveria and Metarhizium, order Hypocreales (Ascomycota), class Hyphomycetes, have been well researched and used against several pest insects in agriculture (Inglis et al. 2012;Meyling & Eilenberg 2007). Using EPF for insect control is an important tool in terms of organic agriculture and the integrated control of pests, including Coleoptera, Hemiptera and Lepidoptera, which attack economically important crops (Rodrigues et al. 2016). ...
Entomopathogenic fungi (EPF) are effective and environment-friendly insect biological control agents. Ultraviolet (UV) light is known to have an effect on the survival of fungal conidia, and natural sunlight is potentially one of the most damaging factors undermining EPF persistence and pathogenicity. This study aimed to test the infection potential of an isolate of Beauveria bassiana and five Metarhizium species after exposure to different light treatments, on soil and leaf surfaces under laboratory and field conditions, using Thaumatotibia leucotreta (Lepidoptera: Tortricidae) as the test host. Conidia were exposed either to growth light alone, which emits the same visible light as the sun, but excluding UV light, or directly exposed to UV light for 12 h. The results indicated no negative effect on the infection potential of the conidia of most species tested. The conidia of the two Metarhizium pinghaense (5HEID and TH149) isolates showed the greatest tolerance to visible light and UV radiation exposure on both soil and leaf surfaces. Exposure of M. pinghaense isolates to visible light on soil surfaces showed pathogenicity of > 80% for both isolates, and of between 58% and 88% after exposure to UV light. On leaf surfaces, three Metarhizium isolates, M. pinghaense (5HEID and TH149) and M. majus (TH153) had > 90% pathogenicity following exposure to UV light, and M. pinghaense (TH149) and M. robertsii (6EIKEN) showed greater tolerance of > 70%, under laboratory conditions. However, the pathogenicity of the EPF isolates was very low in field trials, indicating that further trials on the use of formulations and adjuvants with the isolates are needed to improve long-term persistence and efficacy under field conditions.
... In addition to their broad host range, these fungi are also known for their high virulence and ability to persist in the environment. They have been shown to provide long-term control of insect populations, making them effective alternatives to chemical insecticides [30][31][32]. ...
The Green Revolution led to an increased use of synthetic pesticides, causing environmental pollution. As an alternative, biopesticides made from entomopathogenic agents such as fungi have been sought. This study aimed to design and evaluate the performance of a harvester machine for efficiently collecting entomopathogenic spores of Metarhizium anisopliae and Beauveria bassiana grown on rice and corn substrates. The spore yield was estimated, and a spore count and a colony-forming unit (CFU) count were performed. Statistical analysis was conducted to compare the mean values of spores obtained from different combinations of solid substrate and fungi. The Corn-Metarhizium combination produced 34.15 g of spores per kg of substrate and 1.51 × 109 CFUs mL−1. Similarly, the Rice-Metarhizium combination produced 57.35 g per kg and 1.59 × 109 CFUs mL−1. Meanwhile, the Corn-Beauveria combination yielded 35.47 g per kg and 1.00 × 109 CFUs mL−1, while the Rice-Beauveria combination had a yield of 38.26 g per kg and 4.50 × 108 CFUs mL−1. Based on the reported results, the Rice-Metarhizium combination appears to be the most effective, yielding the highest number of harvested spores per kg of substrate. The study estimated a total cost of approximately $409.31 for manufacturing the harvester, considering only the cost of the materials. These results could potentially increase the availability and affordability of entomopathogenic fungi in integrated pest management.
... All Beauveria isolates infecting SLF collected in Pennsylvania from 2017 to 2020 were identified as B. bassiana. Beauveria bassiana is also known to infect SLF in China (42), where this invasive host is native. Beauveria bassiana was also a major (13) and infecting emerald ash borers in Michigan and southwestern Canada (14). ...
The entomopathogenic fungus Beauveria bassiana is cosmopolitan and known to infect a variety of sap-sucking pests like aphids, mealybugs, and scales in the order of Hemiptera. In Fall 2017, spotted lanternfly (SLF) adults killed by the fungal entomopathogen B. bassiana were found in Berks County, Pennsylvania. In 2018-2020 we collected SLF and nearby non-target insects killed by Beauveria spp. from 18 field sites in southeastern Pennsylvania. We identified 159 Beauveria isolates from SLF and six isolates from non-targets. Five isolates of B. bassiana and one isolate of B. brongniartii were identified from the non-targets. Based on sequence data from the nuclear B locus (Bloc) intergenic region, all the isolates from SLF were identified as B. bassiana, but there were 20 different strains within this species, grouped into two clades. Three B. bassiana strains (A, B, and L) were found in most field sites and were the most prevalent. Representative isolates for these three strains were used in laboratory bioassays and were compared to a commercial B. bassiana strain (GHA). Strain B was inferior to A, L, and GHA against nymphs; strains A and L had greater efficacy than B and GHA against adults. We also quantified conidial production on SLF cadavers. This paper discusses the diversity of these B. bassiana strains in SLF populations and implications for biological control of this abundant invasive.
... En el caso del género Beauveria, no se registró en el área de estudio, posiblemente su ausencia se debe a que es menos común en suelos agrícolas (Barker & Barker, 1998), donde la presencia de B. bassiana se ve disminuida por la aplicación de plaguicidas (Muñiz-Reyes et al., 2014), confirmando que la diversidad de especies está inversamente relacionada con el grado de disturbio humano (Aung et al., 2008;Garrido-Jurado et al., 2015). Por el contrario, se ha indicado que Metarhizium es un género que resiste a las perturbaciones provocadas por la agricultura, además de ser el más común encontrado en suelos cultivados (Meyling & Eilenberg, 2007;Quesada-Moraga et al., 2007;Jabbour & Barbercheck, 2009;Keyser et al., 2015;Hernández-Domínguez et al., 2016;Uzman et al., 2019), esto debido a que sus conidios pueden sobrevivir por más tiempo aún sin hospederos (Vänninen, 1996), incluso, algunas especies del género Metarhizium pueden ser endófitas facultativas (Deaver et al., 2019), lo que les permite sobrevivir en las proximidades de las raíces de las plantas sin llegar a colonizarlas (Moonjely & Bidochka, 2019). La predominancia del género Metarhizium en el suelo del cultivo del aguacate, puede deberse a su capacidad para colonizar fácilmente la rizosfera de las plantas, formando asociaciones endofíticas (Behie et al., 2015), incluso, se ha reportado que especies como M. robertsii puede transferir nitrógeno derivado de insectos a las plantas (Botelho et al., 2019;Barelli et al., 2020). ...
Avocado (Persea americana Mill.) has become one of the most important fruits in the world, being Mexico the main producer and exporter worldwide, it has led to an accelerated growth in the establishment of monoculture avocado plantations, promoting the increase of insect and mite pests, which has led to the need for biological control strategies for integrated pest management. The objective of this study was to isolate entomopathogenic fungi from the soil of a conventional avocado orchard and identify them by translation elongation factor 1-α (5’TEF). During the sampling, a total of 34 isolates were obtained, belonging to the genus Metarhizium, 23 isolates identified as Metarhizium robertsii and 11 as Metarhizium guizhouense. These results show the low diversity of entomopathogenic fungi species associated with the rhizosphere of the avocado crop and suggest that their occurrence could be associated with their ability to survive agronomic practices that induce their endophytic activity. It is necessary to understand the role of Metarhizium in the rhizosphere, this will allow the development of biological control programs specific for each crop, and thus guarantee its success in pest control.
... Different isolates have been identified to attack a wide range of insects (707 species belonging to 15 orders) and mites (13 species) [14][15][16]. According to [17], almost all major taxa of intensively harvested insects are likely considered natural hosts for B. bassiana in temperate regions. ...
The chestnut moth (Cydia splendana Hübner) and the chestnut weevil (Curculio elephas Gyllenhal) cause serious damage to European producers and companies that transform and market the chestnut. The objective of the present work was to evaluate, under field conditions, the possibilities of Beauveria bassiana (Bals.-Criv.) Vuill. to infect and kill the larvae of the two main carpophagous pests of European chestnut, in treatments directed at the soil. For this purpose, the surfaces of vases were sprayed with two concentrations of conidia/mL 5 × 107 (T1) and 1 × 108 (T2). The control (T0) was sprayed with distilled water. Larval mortality and infection were evaluated on five dates (D8 to D220). Confirmation of the fungus present in the larva was performed by molecular analysis. The results obtained are promising for the use of B. bassiana as a biological control agent against these key pests of the chestnut crop. There were no significant differences in mortality between the T1 and T2 modalities, however, they were significantly higher than the control. In the case of total mortality (dead and infected larvae), no significant differences were observed for C. elephas either. In the case of C. splendana, the T2 modality obtained better results in terms of total mortality.
... The fungal genera Beauveria and Metarhizium are two important entomopathogenic agents employed in controlling agricultural and forestry pest insects because of their wide host ranges (Meyling and Eilenberg 2007). Also, some strains of the genus Fusarium have been reported as efficient in controlling pest insects, exhibiting some of the characteristics desirable for an agent of agricultural and forestry biological control, such as delivering high mortality rates and presenting abundant sporulation capacity. ...
Fusarium concentricum Nirenberg & O' Donnell (Ascomycota: Hypocreales) is a fungal species known to infect plants, but never reported as entomopathogenic. Polychrosis cunninhamiacola Liu et Pei (Lepidoptera: Tortricidae: Olethreutinae) is a major and widespread insect pest causing economic losses to cultivated Chinese fir Cunninghamia lanceolata (Lamb.) Hook. It is routinely controlled by extensive use of chemical insecticides, which is perceived as environmentally unsustainable. During March and April of 2019-2020, muscardine cadavers of larvae and pupae of P. cunninhamiacola infected with growing fungus were collected in a fir forest in northern Guangdong Province, China. Conidia were isolated and cultured on PDA medium, from which the fungal strain was identified as F. concentricum FCPC-L01 by morphology and by sequence alignment match with Tef-1α gene. Pathogenicity bioassays at the conidial concentration 1 × 107 revealed P. cunninhamiacola adults and Danaus chrysippus (L.) (Lepidoptera: Nymphalidae) larvae are sensitive to the fungal infection, but not the fire ant Solenopsis invicta Buren (Hymenoptera: Formicidae). We believe results indicate this fungal strain might be applicable against specific target insect pests. As this is the first record of a natural infection caused by F. concentricum in insects, we propose host specificity tests should be done to evaluate its potential as a biocontrol agent.
... One of the biological control agents is entomopathogenic fungi including Metarhizium sp and Beauveria bassiana (Grijalba et al., 2018). B. bassiana is cosmopolitan and able to survive in endophytic land (Meyling & Eilenberg, 2007). The potential ability of B. bassiana to control fall armyworms needs to be compared to effectiveness of chemical insecticides. ...
Fall armyworm or Spodoptera frugiperda is one of the main pests of corn. It can caused up to 28.08% yield loss. Pest control efforts with broad-spectrum insecticides can cause negative impacts that disrupt ecosystems, non-target biotic factors and the surrounding environment. Beauveria bassiana is an alternative biological control agent that is target-specific. This study was conducted to determine toxic and antifeedant activities of B. bassiana application on third to fifth-instar S. frugiperda larvae. B. bassiana isolates were propagated using corn flakes media and resulted in colonies with conidia density of 1.1×108conidia.g-1. This study used a completely randomized design with 5 treatments and 5 replications. Treatments consisted of P1 namely B. bassiana propagation with a concentration of 60 g.L-1, P2 = 70 g.L-1, and P3 = 80 g.L-1. P0 was a negative control (untreated with B. bassiana) and P4 was a positive control (diazinon with concentrations of 2 ml.L-1). The variables observed were mortality and weight of the leftover feed. The results showed that the formulation of B. bassiana with concentrations of 80 g.L-1 was able to infect armyworms with a mortality percentage of 53.5% which was statistically similar as the effect of chemical insecticides. In addition, inhibition of feeding activity due to treatment could prevent leaf damage up to 68.21%.
... The most commonly applied EPF species are Metarhizium anisopliae (Ma) and Beauveria bassiana (Bb) (van Lenteren et al., 2018). Both Hypocrealean EPF rely on multiple exoproducts to overcome the insect's defence mechanisms and kill it, such as proteases, chitinases, lipases, immunomodulation and transcription factors, as well as beauvericin, bassianin and oosporein for Bb, and cyclosporine and destruxin for Ma (Barelli et al., 2016;Butt et al., 2016;Meyling and Eilenberg, 2007;Schrank and Vainstein, 2010). EPN are associated with specific bacteria (nematode-associated bacteria, NB) that play the most important part in killing the insect, e.g. ...
Below-ground insect pests are challenging to control because they are hard to target with control measures. Moreover, broad spectrum insecticides are or will soon be banned due to their negative effects on non-target organisms. In this study, we have developed a biological control method for the cabbage maggot Delia radi-cum (Diptera: Anthomyiidae), a significant pest of Brassicacean crops, based on a consortium of three biocontrol agents (BCAs). We chose the bacterium Pseudomonas chlororaphis because it can be used in a dual strategy against insect pests and fungal plant diseases, and combined it with the nematode Steinernema feltiae and the fungus Metarhizium brunneum that have a long history of commercial use against different pest insects. Our aim was to combine BCAs with different modes of action in order to achieve a stable and reliable biocontrol effect. We first tested double combinations of the bacterium with either the nematode or the fungus for improved potential to kill D. radicum in laboratory assays. We then evaluated the effect of double and triple combinations on D. radicum development and maggot-induced damage on radish bulbs in a series of pot experiments with artificial cabbage maggot infection performed in the greenhouse and outdoors and finally in a field trial with a natural infestation. Our results show that i) insecticidal pseudomonads are highly efficient in D. radicum control, ii) the three BCAs are compatible and neither inhibit each other's infectiousness nor survival in the soil or on the roots, iii) syn-ergistic effects of Pseudomonas-nematode and Pseudomonas-fungus combinations on maggot killing are possible, and iv) the triple combination reduced both pest survival in greenhouse experiments and maggot-induced damage on radish bulbs in the field by 50% each. The strategy we present here is a promising step forward to a reliable and efficient environmentally friendly biological control method for the cabbage maggot, which can also be adapted to other problematic below-ground pests.
... When resources are used up after several cycles of nematode reproduction, the nematodes take up bacteria and form a free-living infective juvenile (IJ) stage to hunt for a new host [18]. Finally, the EPF member of the consortium is Metarhizium brunneum, a common organism in agricultural soils especially in temperate regions [21]. M. brunneum infects and kills insects by attaching to and breaching through the cuticle, colonizing the insect hemolymph, and producing different proteases, toxins, and exoproducts during the whole process [22,23]. ...
Combining different biocontrol agents (BCA) is an approach to increase efficacy and reliability of biological control. If several BCA are applied together, they have to be compatible and ideally work together. We studied the interaction of a previously selected BCA consortium of entomopathogenic pseudomonads (Pseudomonas chlororaphis), nematodes (Steinernema feltiae associated with Xenorhabdus bovienii), and fungi (Metarhizium brunneum). We monitored the infection course in a leaf- (Pieris brassicae) and a root-feeding (Diabrotica balteata) pest insect after simultaneous application of the three BCA as well as their interactions inside the larvae in a laboratory setting. The triple combination caused the highest mortality and increased killing speed compared to single applications against both pests. Improved efficacy against P. brassicae was mainly caused by the pseudomonad-nematode combination, whereas the nematode-fungus combination accelerated killing of D. balteata. Co-monitoring of the three BCA and the nematode-associated Xenorhabdus symbionts revealed that the four organisms are able to co-infect the same larva. However, with advancing decay of the cadaver there is increasing competition and cadaver colonization is clearly dominated by the pseudomonads, which are known for their high competitivity in the plant rhizosphere. Altogether, the combination of the three BCA increased killing efficacy against a Coleopteran and a Lepidopteran pest which indicates that this consortium could be applied successfully against a variety of insect pests.
Graphical Abstract
... It has a wide host range of over 17 arthropod orders which includes spiders (Shrestha et al., 2019;Zimmermann, 2007), although infections have seldom been documented (Meyling & Eilenberg, 2007 writing -original draft (supporting); writing -review and editing (supporting). ...
Abstract Earth systems are nearing a global tipping point, beyond which the dynamics of biological communities will become unstable. One major driver of instability is species invasion, especially by organisms that act as “ecosystem engineers” through their modification of abiotic and biotic factors. To understand how native organisms respond to modified habitat, it is essential to examine biological communities within invaded and non‐invaded habitat, identifying compositional shifts in native and non‐native taxa as well as measuring how modification by ecosystem engineers has affected interactions among community members. Using dietary metabarcoding, our study examines the response of a native Hawaiian generalist predator (Araneae: Pagiopalus spp.) to habitat modification by comparing biotic interactions across metapopulations of spiders collected in native forest and sites invaded by kāhili ginger. Our study shows that, although there are shared components of the dietary community, spiders in invaded habitat are eating a less consistent and more diverse diet consisting of more non‐native arthropods which are rarely or entirely undetected in spiders collected from native forest. Additionally, the frequency of novel interactions with parasites was significantly higher in invaded sites, reflected by the frequency and diversity of non‐native Hymenoptera parasites and entomopathogenic fungi. The study highlights the role of habitat modification driven by an invasive plant in altering community structure and biotic interactions, threatening the stability of the ecosystem through significant changes to the biotic community.
... Secondary metabolites secreted from the insect pathogenic fungus Metarhizium anisopliae and Beauveria bassiana are important microbial control agents against mosquito larvae, pupae, and adults (Meyling and Eilenberg 2007; for more information see Vivekanandhan et al. 2020b). Verticillium lecanii (Vivekanandhan et al. 2020a), Fusarium oxysporum (Vivekanandhan et al. 2018b), Metarhizium anisopliae (Scholte et al. 2007), and Beauveria bassiana have mostly been found to have biological control potential against a variety of insect pests (Vivekanandhan et al. 2018c). ...
Synthetic pesticides are a considerable issue in both terrestrial and aquatic habitats. Green pesticides derived from fungi, provide an efficient tools and alternative to chemicals. Secondary metabolites from Metarhizium anisopliae were tested against major disease mosquitos such as, Anopheles stephensi, Aedes aegypti, and Culex quinquefasciatus, as well as two non-target species, Eudrilus eugeniae and Artemia nauplii. After 24 h of treatment, M. anisopliae derived chemical constituent produced low LC50 values, 54.678, 92.819, and 93.792 µg/ml on Aedes aegypti, for Anopheles stephensi, 80.933, 116.990 and 130.173 µg/ml, for Culex quinquefasciatus, 109.733, 196.540, 182.853 µg/ml in larvae, pupae, and adult, respectively. On the contrary, fungal metabolites are not hazardous to non-target species.. Midgut histology investigations revealed that M. anisopliae metabolites were less harmful to earthworms than chemical pesticides (Permethrin). The treatment of fungal crude extract exhibited minimal toxicity effects on gut tissues, normal epidermis, circular muscle, setae, mitochondrion, and intestinal lumen tissues. M. anisopliae crude metabolites showed a lower toxicity against the non-target species A. nauplii. Our results clearly shows minimal mortality rates were produced by the M. anisopliae derived chemical constituents, LC50 and LC90 values were, 455.947, 5098.233 μg/mL−1. No behavioral changes were observed during the treatment. The primary components of M.anisopliae crude extract identified by GC–MS studies were aucubin (14.356%) and 9, 12-Octadecadienoic acid (z,z)-(75.009%). The presence of key functional groups such as carboxylic acid, amides, and phenol groups was revealed by FT-IR spectral studies, which may be involved in mosquitocidal activity.
... However, even if such bottom-up effects are assumed to be more efficient on pests with good sensory abilities, such as lepidopterans and coleopterans, our literature survey shows that companion plants are also used against pests with low dispersal and host detection ability, such as hemipterans (Potting et al. 2005). Microorganisms, on the other hand, which can also use chemical cues to locate hosts, might be highly influenced by their limited dispersal ability, thus diminishing the chances of locating suitable prey/hosts (Meyling and Eilenberg 2007;Pell et al. 2010). Microorganisms are therefore mainly used as bioprotection agent with crop temporal diversification and soil management targeting soil microorganism pests. ...
The heavy use of synthetic pesticides in agriculture has been responsible for detrimental effects on human and environmental health, making it necessary to develop more sustainable pest management strategies. A promising approach consists in the integration within cropping systems of agricultural techniques producing bottom-up effects or supporting top-down regulation of crop pests. However, there is still a lack of information on the extent to which this approach is currently being developed. In this paper, we review the last 10 years of published literature on the use in annual cash crops of three agricultural techniques: (i) crop spatial diversification, (ii) crop temporal diversification, and (iii) soil management influencing crop pests either through bottom-up effects or by supporting the top-down regulation of four categories of bioprotection agents: (i) macro-and (ii) microorganisms , (iii) semiochemicals, and (iv) natural substances. We found that each agricultural technique is adopted to support a specific bioprotection category and to control a specific pest taxon. Crop spatial diversification was generally found to target herbivorous insects and to support macro-organism bioprotection agents. Crop temporal diversification and soil management mainly targeted pathogenic fungi and supported microorganism bioprotection agents. Despite the widespread idea that semio-chemicals and natural substances are promising agents for pest regulation, their adoption remains largely unexplored. We also found that agricultural techniques are mostly adopted to support bioprotection in a conservation biological control approach while ignoring augmented bioprotection. In addition, the top-down regulation by means of bioprotection supported by agricultural techniques is just as effective against crop pests as the bottom-up effect produced by the agricultural techniques alone. We argue that a concerted effort to integrate bioprotection with agricultural techniques would open new research opportunities to reduce synthetic pesticide inputs fostering the transition from a conventional agriculture towards sustainable agroecosystems.
... Entomopathogenic fungi have been well studied and developed into biopesticides, due to their high virulence towards a wide range of insect pests, their ability to form resistant structures and persist in the environment, and their innocuity to the environment and human health (Zimmermann, 2007). The most studied entomopathogenic fungi belong to the genus Metarhizium (Meyling and Eilenberg, 2007;Zimmermann, 2007). Metarhizium anisopliae has been isolated from insect cadavers, soil, and roots. ...
Entomopathogenic fungi are key components of biological pest control programs. Among these, Metarhizium anisopliae is one of the best-studied and has been demonstrated to be particularly effective against coleopterans. The native M. anisopliae CPMa1502, previously selected for its insecticidal activity against Demotispa neivai (oil palm fruit scraper), was studied to establish its growth parameters under several culture conditions and its virulence on different stages of D. neivai. Considerable conidia production of CPMa1502 on MAYP (Maltose Agar Yeast with Potato Extract) and SMAYR (Sabouraud Maltose Agar with yeast extract and rice extract) agar was observed (1×109 conidia cm–2 at 14 days). The isolate was highly tolerant to a wide range of pH (5-9; germination >90%; radial growth rate: 0.95-1.02 mm day–1) but moderately tolerant to high temperatures (>35°C). Additionally, the adhesion capacity to D. neivai cuticle and conidial hydrophobicity was strong (114 conidia mm–2: 72%). Finally, the insecticidal activity of CPMa1502 was greater on larvae than on adults, with a mean lethal concentration (LC50) of 1.8×104 conidia mL–1 and a mean lethal time (LT50) of 4.3 days, than on adults. These findings show that CPMa1502 is a promising candidate for further development as a biopesticide against D. neivai.
In the germplasm bank of 22 varieties of avocado (Persea Americana Mill.) belonging to the Fruit Horticultural Institute Investigation, HermilioValdizan National University (UNHEVAL)-Peru, it is common to observe a high population of the species Oligonychusyothersi, a phytophagous mite harmful to the crop. Controls with commercial acaricides are restricted in place, due to the presence of beehives installed in adjacent plots. The objective of this study was to evaluate the effect of four commercial formulations containing strains of Metarhiziumanisopliae and Beauveria bassiana and the toxins of Bacillussubtilis, Bacillus thuringiensis var.kurstaki (Btk) for the control of O. yothersi. The entomopathogenic products were evaluated in the field applying a randomized complete block design with five treatments and three replicates. In the laboratory, 500 adult mites were selected, placing 100 mites per Petri dish with three repetitions per treatment. It was found that the formulation Bacillus thuringiensis var.kurstaki under field conditions reduced the population incidence of mites by up to 98.07% in 49 days. In the laboratory, the B. subtilis and M. anisopliae formulations caused 100% mortality six days after application proving to be efficient control alternatives.
Biological control using natural enemies such as predatory insects and parasitoids has become an important alternative way of pest management and represents a crucial component in Integrated Pest Management (IPM). Although parasitoids are commonly used as biocontrol agents, their efficacy is not always sufficient to reduce pest populations to acceptable densities. Given that parasitoids can be attracted towards plants inoculated with entomopathogenic fungi, a combination of endophytic entomopathogenic fungi and parasitoids may lead to enhanced biocontrol efficacy, but information in this regard is scarce. Here, we used sweet pepper (Capsicum annuum L.), the entomopathogenic fungus Akanthomyces muscarius ARSEF 5128, the tobacco peach aphid Myzus persicae var. nicotianae and the aphid parasitoid Aphidius ervi to assess whether root inoculation with an entomopathogenic fungus has the potential to increase the biocontrol efficacy of an arthropod biological control agent. Results obtained over a five-weeks period revealed that a combination of the fungus and the parasitoid significantly improved biocontrol efficacy compared to the separate applications of the biocontrol agents, specifically by enhancing short-term parasitoid effectiveness. In greenhouse cages with A. muscarius and A. ervi, the aphid population was not able to produce progeny, and aphids were parasitized fast and efficiently. In cages with control plants and A. ervi, parasitism efficiency was significantly lower and the aphid population was able to increase by several generations. In these cages, the parasitoids could effectively control the aphid infestation after repeated parasitoid releases. We conclude that fungal inoculation improved parasitoid biocontrol efficacy, providing new opportunities for pest control.
Introduction
Entomogenous fungi include a wide range of species that are ecologically very diverse. Many of them are pathogenic to insects and mostly show host specificity. Isolation and identification of native entomogenous fungi, especially pathogenic species, and their use as a source of biological control agents is an important safe, environmentally-friendly pest control approach. This survey isolated and characterized entomogenous fungi that naturally occur in soil. Post-harvest infestations cause considerable losses in cereal production. Stored-product insect control is mainly accomplished by chemical means; however, pesticides can affect non-target species, such as plants, animals, and humans. Pesticides increase pest resistance. Another possible negative effect of pesticides is their ability to bioaccumulate and biological magnification. Therefore, alternative agents are needed for managing stored-product insect pests. Biological control of stored-product insects with entomopathogenic fungi is a successful, sustainable alternative to chemical insecticides. Mediterranean flour moth, Ephestia kuehniella, is one of the most important insect pests infesting stored grain of cereals worldwide. This study isolated and determined some entomopathogenic fungi's efficacy in flour moth biocontrol, E. kuehniella.
Materials and Methods
Different strains of entomopathogenic fungi were isolated from the soils of various districts of Azarbaijan province in the Northwest of Iran. Their virulence against E. kuehniella larvae was evaluated. Isolates of various entomopathogenic fungi were isolated and purified using a soil trap from twenty distinct soil specimens. The immersion technique evaluated their pathogenicity against E. kuehniella in three replicates. This was done at 104, 105, 106, 107, and 108 conidia/mL concentrations. All selected fungal isolates were identified based on morphological features and mycological parameters.
Results
Four isolates of B. bassiana (BVA, BVB, BVE, and BVF) and two of L. lecanii (LCA and LC) from fourteen isolates were isolated. Six fungal species, namely Lecanicillium lecanii and Beauveria bassiana, were identified among the fourteen isolates collected. The bioassay assessment revealed that E. kuehniella fourth-instar larvae were susceptible to all isolates and that the larval death rate increased with rising conidial concentration. The BVA and BVB isolates of B. bassiana showed the maximum virulence, with nearly 2.5×105 and 2.8×105 (conidia/mL) LC50, while the BVF isolate of B. bassiana had the least virulence among the other isolates evaluated, with nearly 2.2×107 (conidia/mL) LC50 on E. kuehniella. The lowest LT50 value (3.72 days) using a 108 conidia/ml concentration on E. kuehniella larvae was shown on the BVA isolate.
Discussion
A comparison of the means and grouping of isolates showed a significant difference between isolates and the effectiveness of different concentrations. Also, the BVA isolate of B. bassiana had greater efficiency than the other isolates, and therefore, they will be more suitable for use in plant pest biological control programs.
Various techniques used by crop plants to evade insect pests and pathogen attacks have been documented. Among these, plant defense strategies induced by endophytic insect pathogenic fungi are arguably one of the most discussed. Endophytic fungi frequently colonize plants and inhabit their internal tissues for a portion of their lifespan without producing visible symptoms of the disease. This phenomenon is widespread and diverse in both natural and agricultural ecosystems, and is present in almost all plant organs. Many fungi can obtain nutrients by infecting and killing insects, and this ability has been developed numerous times in different fungal lineages. These species mainly consist of those in the order Hypocreales (Ascomycota), where the generalist insect pathogens, Beauveria sp. (Cordycipitaceae) and Metarhizium sp. (Clavicipitaceae) are two of the most studied endophytic entomopathogenic fungal genera. However, most fungi that kill insects do not survive in the tissues of living plants. The data published thus far show a high degree of variability and do not provide consistent explanations for the underlying mechanisms that may be responsible for these effects. This implies that available knowledge regarding the colonization of plant tissues by endophytic insect pathogenic fungi, the effects of colonization on plant metabolism, and how this contributes to a decrease in herbivore and pathogens damage is limited. To adequately utilize fungal-based products as biological control agents, these products must be effective and the reduction of pests and infection must be consistent and similar to that of chemical insecticides after application. This article discusses this possibility and highlights the benefits and the specific techniques utilized by endophytically challenged plants in invading insect pests and disease pathogens.
This study aims to isolate and identify certain bactеrial and fungal pathogеns from silkworm, Bombyx mori L. such as promising chitosan, plus silvеr nanoparticlеs as its antimicrobial activity undеr laboratory condition. Silkworm, B. mori (H1xKKxG2xV2-Bolgaria) eggs werе attained from Sеriculture Rеsearch Cеntеr from Giza Governorate, Egypt. Chitosan and silvеr nanoparticlеs matеrials were assembled at the laboratory of Biochеmistry Departmеnt, Faculty of Agriculturе, Al-Azhar University, Cairo, Egypt. Herein total of 7 bactеrial and 5 fungal were isolatеd from the еxtеrnal and internal silkworm larvae. As a result, the mean percentage decrease in weight was elevated in diseased fifth instars (88%) compared to fourth diseased instars (62%). In addition, two bactеrial spеcies isolatеd from the infectеd larvae were identified as follows: Staphylococcus aurеus and Enterococcus faеcalis, whereas thrее fungal spеcies were isolatеd as follows: Aspergillus flavus, Aspergillus tamarii and Beauveria bassiana. Transmission elеctron microscopе imaging demonstrated the morphological propеrties and surfacе appеarance of silvеr and chitosan nanoparticlеs which havе a nеarly sphеrical shapе and smooth surfacе. The avеrage particlе size of 18.7-26.0 nm and 18.8 to 21.8 nm of silvеr and chitosan nanoparticles were recordеd. Furthermore, the highеst activity among nanoparticlеs tested against all pathogеnic bacteria and fungi isolatеd and idеntified in our study was rеcordеd by chitosan at 100 µg/ml in sеries, whilst silvеr nanoparticle еxhibitеd modеrate antibacterial and antifungal activity.
Metarizhium anisopliae (Metsch.) is an entomopathogenic fungus that attacks Oryctes rhinoceros (Linnaeus). This fungus is one of the potential bioagents that is environmentally friendly. The purpose of this study was to isolate the fungus M. anisopliae from various oil palm plantation soil samples and to see its genetic diversity based on RAPD markers. The method used in this research is the morphological and the molecular identification of M. anisopliae (ITS), and genetic diversity testing using RAPD markers. Fifteen isolates of M. anisopliae isolated from 15 oil palm plantation sites in North Sumatra were examined for their molecular diversity. On the basis of morphological characteristics, all isolates were identified as M. anisopliae. The result of sequencing with the ITS primer showed that all isolates of M. anisopliae isolated from soil had a 85–99% homology of with M. anisopliae and M. brunneum reference strains from gen bank database National Center Biotechnology Information (NCBI). Eight RAPD primers generated 39 scorable bands which 38 (98,44%) of them were polymorphic. Clustering analysis was performed based on RAPD profiles using Neighbour-Joining Tree method that formed 3 groups. Key words: entomopathogenic fungi, genetic diversity, ITS sequencing, RAPD
Background: Entomopathogenic fungi (EF) play a key role in the regulation of arthropod populations and
biotransformation in natural systems, as well as biological pest control agents in different agroecosystems, including
avocado cultivation (Persea americana Mill.), where Mexico is a leader in production and export worldwide.
Objective: Determine the presence of EF in soil in commercial avocado orchards in the state of Colima, Mexico.
Methodology: Sampling was carried out in three avocado orchards (Piedra rajada, El Guardián, and Montitlán) located
in Comala and Cuauhtémoc in the state of Colima, Mexico, from July 2016 to June 2017. Soil samples were collected
around avocado trees. Isolation of entomopathogenic fungi was performed using the Galleria mellonella Linnaeus
insect trap technique. The isolates were identified considering their micro- and macroscopic characteristics with the
taxonomic keys of Humber (2012). Results: A total of 108 samples were collected, of those, 120 isolates were obtained,
of which 112 belong to the genus Metarhizium and eight to Beauveria. Implications: The recovered fungi have a great
value for the avocado-growing areas of the state of Colima, either for the conservation of natural enemies of soil pests
or for their potential use as an alternative to synthetic insecticides. Conclusion: Knowing the native micro-biota of the
soil should be considered within biological pest control strategies, since it allows selecting the best adapted species,
and including sustainable alternatives for the environment.
تهدف الدراسة الى استخدام الفطر الغير ضار Trichoderma harzianuim في مكافحة الاطوار اليرقية وبالغات خنفساء الدقيق المتشابهة Tribolium confusum كنوع من االمكافحة الحيوية . واظهرت نتائج الدراسة ان نسبة الموت في اليرقات كانت اعلى من نسبة موت البالغات بمتوسط (7.54 , 3.57) على التوالي. كما لوحظ ان للزمن تأثير معنوي على متوسط عدد الحشرات البالغة الميتة حيث زادت نسبة الموت بعد معاملتها بالفطر T. harzianuin كلما زادت الفترة الزمنية حيث وصلت نسبة الموت اعلاها بعد 72 ولم يكن للزمن تأثير معنوي على اليرقات حيث كانت اقل مقاومة للفطر. كما بينت النتائج وعند استخدام التراكيز( 2.8×106, 2.8×104, 2.8×102) على اليرقات والبالغات ان عدد اليرقات الميتة كان يقل مع زيادة تركيز الفطر بينما عدد البالغات الميتة يزيد مع تركيز الفطر .
Unlike mammals, most invertebrates provide no direct parental care for their progeny, which makes a well-selected oviposition site crucial. However, little is known about the female evaluation of opportunities and threats during host selection. Leveraging the wide range of host plants used by the polyphagous pest, Spodoptera littoralis, we investigate oviposition choice between two plants of different nutritional quality. Females prefer to lay their eggs on the host plant, which has inferior larval development and more natural enemies but provides lower predation rates. On the superior host plant, a major predator shows more successful search behavior and is more attracted to herbivore-induced volatiles. Our findings show that predator efficacy and odor-guided attraction, rather than predator abundance, determine enemy free space. We postulate that predators' behaviors contribute to the weak correlation between preference and performance during host plant selection in S. littoralis and in polyphagous insects in general.
The natural occurrence of entomopathogenic fungi (EPF) was investigated along the Ticino River (Ticino River Natural Park, Novara Province, Piedmont, Italy), at the center of the area of the first settlement of the invasive alien pest Popillia japonica. Using Zimmermann's "Galleria bait method", EPF were successfully isolated from 83 out of 155 soil samples from different habitats (perennial, cultivated, or uncultivated meadows, woodlands, and riverbanks). Sequencing of the 5' end of the Translation Elongation Factor 1 alfa (5'-TEF) region allowed the assignment of 94% of the isolates to Metarhizium spp., while 8% and 7% were assigned to Beauveria spp. and Paecilomyces spp., respectively. Four Metarhizium species were identified: Metarhizium robertsii was the most common one (61.5% of the isolates), followed by M. brunneum (24.4%), M. lepidiotae (9%), and M. guizhouense (5.1%). Microsatellite marker analysis of the Metarhizium isolates revealed the presence of 27 different genotypes, i.e., 10 genotypes among M. robertsii, 8 among M. brunneum, 5 among M. lepidiotae, and 4 among M. guizhouense. Metarhizium brunneum appeared to be associated with woodlands and more acid soils, while the other species showed no clear association with a particular habitat. Laboratory virulence tests against P. japonica 3rd instar larvae allowed the identification of one M. robertsii isolate that showed efficacy as high as 80.3%. The importance of this kind of study in the frame of eco-friendly microbiological control is discussed.
This book presents topics on the development, improvement and commercialization of fungi for the biological control of pests, weeds and diseases which are of economic importance. Common themes such as production, formulation and application of technologies, biosafety, risk assessment and registration requirements are all covered. The book attempts to bring together scientists, industry and government agencies involved in all aspects of fungal biological control agents for the first time.
Effects of temperature on growth on a semisynthetic medium of 65 isolates of Beauveria bassiana from different geoclimatic and host origins were determined. The isolates were grouped according to the climate of their geographic origin, distinguishing between cool and warm regions; according to their host origin, distinguishing between isolates from acridids or from soil associated with acridid populations; and according to host order. In general, B. bassiana grew at a wide temperature range from 8 to 35 C. A well defined maximum thermal threshold occurred at temperatures of >35-37 C for 50 isolates; >32-35 C for 12; and >30-32 C for 1 isolate. The lower temperature threshold for all isolates tested was below 8 C. Relative growth rate, calculated from the maximum growth rate for each isolate, was significantly affected by temperature and isolate. Optimal temperatures were generally between 25 and 28 C with several isolates exhibiting optimal growth at temperatures as low as 20 or as high as 30 C. Relative growth rates were not very useful in distinguishing differences among many of the isolates at the near-optimal temperatures. In contrast, the ability to distinguish differences in relative growth rates among isolates increased progressively as temperatures increased above 28 C or decreased below 20 C. There were no apparent relationships between relative growth rates and climatic origin. In comparisons of acridid-associated isolates, relative growth rates were higher for the insect isolates at 8 C and for the, African soil isolates at 35 C. At the other temperatures, no clear relationships were apparent. When comparisons were made according to host order, there were significant differences in relative growth rates according to host order at 8, 11, 30, and 32 C but not at the other temperatures. Since temperature growth responses varied considerably among isolates, with some having wide ranges of temperature optima while others were much more restricted, strain selection according to thermal requirements may be warranted when choosing a strain for development as a microbial control agent.
The influence of rain on removal of Beauveria bassiana conidia from potato (Solanum tuberosum) leaves and Colorado potato beetle (Leptinotarsa decemlineata) larvae was investigated. In the first experiment, substrates were exposed to simulated rain of varying intensities (25, 77, and 89 mm/h) and durations (0, 15, 30, 45, and 60 min). Substantial numbers of colony-forming units (CFU) were removed from leaves (89 to 95%) and from larvae (34 to 70%) by rain exposure, and the majority of CFU were removed within the first 15 min of exposure. Rain intensity had a minimal effect on conidial persistence on both leaves and larvae, but more CFU were removed from larvae exposed to the highest rain intensity treatment. Conspicuous clumping of conidia was observed on the cuticles of both leaves and larvae following application. After rain exposure, conidial clumping was less conspicuous. In a second experiment, the influence of six formulations on the persistence of conidia exposed to rain was investigated. Treatments consisted of a water control, sunflower oil, a wettable powder, and four oil emulsions applied at two rates. Formulation significantly affected removal of CFU from potato leaves but not Colorado potato beetle larvae. Conidia applied in sunflower oil were not removed from potato leaves by exposure to 39 mm of rain in 30 min. In contrast, conidial persistence during this period was substantially reduced for conidia applied in water, a wettable powder containing clay, and an oil emulsion formulation applied at a low volume rate (2.3 liters of oil in 281 liters of water/ha). Although simulated rain removed substantial quantities of B. bassiana CFU from leaves and to a lesser extent from Colorado potato beetle larvae, a substantial number of the conidia applied in water remained after exposure to relatively high intensity rains. Evidence suggested that conidia in direct contact with the cuticle of leaves and larvae were less prone to be removed by rain than conidia in aggregates and thus not in contact with the cuticle, and emulsifiable oil formulations may be used to enhance conidial retention on foilage.
▪ Abstract Endophytic fungi living asymptomatically within plant tissues have been found in virtually all plant species. Endophytes are considered plant mutualists: They receive nutrition and protection from the host plant while the host plant may benefit from enhanced competitive abilities and increased resistance to herbivores, pathogens, and various abiotic stresses. Limited evidence also indicates that endophytes may influence population dynamics, plant community diversity, and ecosystem function. However, most of the empirical evidence for this mutualism and its ecological consequences has been based on a few agronomic grass endophytes. More recent studies suggest that endophyte-host plant interactions are variable and range from antagonistic to mutualistic. A more comprehensive view of the ecology and evolution of endophytes and host plants is needed. This article discusses how life history traits—such as fungal reproduction and pattern of infections and genotypic variation and ecological factors—in...
The clavicipitalean fungi are parasitic and biotrophic symbionts of plants, insects, and fungi. Their associations with and their ecological impacts on symbiotic partners were examined. Particular emphasis is placed on the trend toward plant parasitism and acquisition of the endophytic habit. The effects that clavicipitalean fungi have on the structure or physiology of host species are discussed.
Conidia release by Beauveria bassiana and Metarhizium anisopliae from diseased adult pecan weevils was studied under controlled conditions of relative humidity (RH), temperature, vegetative wetness (VW), and red-infrared radiation (lR). Decreasing RH, from near saturation to 50%, induced only minimal conidia release by both fungi; further lowering of RH below 50% stimulated considerable release. Under conditions of low RH, conidia release by B. bassiana was further enhanced by exposure of specimens to IR, whereas IR had an inconsistent effect on conidia release by M. anisopliae. Sustained periods of constant RH <40% also favored some conidia release but always less than that accompanying RH changes. Conidia release was only recorded during periods of low VW (<5%). Vibration triggered massive conidia release by both fungi which was further enhanced at lower RH levels and by darkness. B. bassiana consistently released 10 to 200 times more conidia than M. anisopliae from an equivalent number of infected weevils.
Curculio caryae larvae exposed to Beauveria bassiana or Metarhizium anisopliae were held in soil cages for 14 months. After weevil larvae were colonized by B. bassiana, hyphae from the weevil cadavers spread through the surrounding soil and formed colonies up to 8.55 cm in diameter (soil volume, 327.26 cm3). M. anisopliae colonies were restricted to larval cadavers and to the inside of larval soil cells. Adjacent, untreated weevil larvae were sometimes infected and killed by B. bassiana that spread through the soil. B. bassiana colonies reached maximum diameter and threatened adjacent weevil larvae 90 to 120 days after primary larvae were infected.
Populations of endemic soil entomopathogens (nematodes and fungi) were monitored in vegetable production systems incorporating varying degrees of sustainable practices in Fletcher, NC. Two tillage types (conventional plow and disk versus conservation tillage), two input approaches (chemically versus biologically based), and two cropping schedules (continuous tomato versus 3-yr rotation of corn, cucumber, cabbage, and tomato) were employed in large plots from 1995 to 1998. A Galleria mellonella (L.) trap bioassay was used to identify and monitor activity of Steinernema carpocapsae, Heterorhabditis bacteriophora, Beauveria bassiana, and Metarhizium anisopliae populations during the vegetable growing season (April-September). Seasonal detection of entomopathogens was significantly higher in conservation compared with conventional tillage systems. The strip-till operation did not affect levels of detection of S. carpocapsae. Pesticide use significantly reduced detection of entomopathogenic fungi. Type of ground cover significantly affected temperature in the upper 12 cm of soil; highest soil temperatures were observed under black plastic mulch and bare ground, whereas lowest temperatures were observed under rye mulch and clover intercrop. The high soil temperatures associated with certain ground covers may have reduced entomopathogen detection or survival. Although type of tillage appeared to be the primary factor affecting survival of endemic soil entomopathogens in our system, other factors, such as pesticide use and type of ground cover, can negate the positive effects of strip-tillage.
The effect of simulated rain at two intensities (26.7 or 112.7 mm h-1) and durations (30 or 60 min) on the persistence of Beauveria bassiana conidia applied in water on leaves of alfalfa leaves of alfalfa (Medicago sativa) or wheat (Triticum aestivum) was investigated. Initial populations of conidia on the leaves of both crops were similar, and ranged from 1.7 105 to 3.5 105 colony-forming units cm-2. The simulated rain reduced the concentration of conidia on leaves by 28-61%. Although there was a slight effect due to rain intensity for alfalfa, there was no influence of either rain duration or crop type on the retention of B. bassiana conidia.
The effects of mulching with organic materials on yield and damage by brassica root maggots (Delia floralis and D. radicum) in cauliflower, were studied in field experiments for 3 years. Mulching with grass‐clippings consistently resulted in increased yield and reduced damage by root maggots, as measured by wilting symptoms and root damage. During one of these years, the effects of mulching with grass‐clippings on root fly population dynamics was also studied. Mulching did not reduce egg‐laying but resulted in increased egg‐predation. The number of D. floralis pupae per plant was not reduced by mulching, probably because of higher larval mortality owing to competition in unmulched plots. Mulching decreased the rate of parasitization by Aleochara bilineata (Staphylinidae), resulting in a higher number of healthy pupae per plant in grass‐mulched plots, and these healthy pupae were heavier. All these effects were most pronounced when the mulch material completely covered the ground, even close to the stems of the plants.
The encyclopaedia of simple disease models.
Most agricultural landscapes are a mosaic of farmers' fields, semi-natural habitats, human infrastructures (e.g. roads) and occasional natural habitats. Within such landscapes, linear semi-natural habitats often define the edges of agricultural fields. This paper reviews the role and interactions within and between the flora of these elements. In temperate, intensive agriculture, such field margin habitats, which historically had true agricultural functions, now are important refugia for biodiversity. As manmade habitats, field margins may also have important cultural roles as part of our landscape heritage, e.g. hedges in Britain. Whilst field margins are not usually specific habitat types, they contain a variety of plant communities in a variety of structures. These may range from aquatic elements to ruderal and woodland communities. Studies demonstrate a variety of interactions between fields and their margins. Agricultural operations, such as fertiliser and pesticide application, have effects on the flora. Some margin flora may spread into crops, becoming field weeds. Margins also have a range of associated fauna, some of which may be pest species, while many are beneficial, either as crop pollinators or as pest predators. The biodiversity of the margin may be of particular importance for the maintenance of species at higher trophic levels, notably farmland birds, at the landscape scale. Margins contribute to the sustainability of production, by enhancing beneficial species within crops and reducing pesticide use. In northwestern Europe, a variety of methods to enhance diversity at field edges have been introduced, including sown grass and flower strips. The impact of these on weed flora and arthropods indicate mostly beneficial effects though conflicts exist, notably for the conservation of rare arable weed species. © 2002 Elsevier Science B.V. All rights reserved.
This paper gives suggestions forunifying the terminology in biological controlacross different research disciplines, such asbiological control of arthropods, weeds andplant pathogens. It is suggested that use ofthe term `biological control' is restricted tothe use of living organisms. Four strategiesof biological control are outlined anddefined: (1) Classical biological control, (2) Inoculation biological control, (3) Inundationbiological control, and (4) Conservationbiological control. It is proposed to usethese four terms as defined, and avoid usageof the term `augmentation'. Terms for specificprocesses and modes of action (for example,`parasitoid' and `competitor') can be definedby usage within the different biologicalcontrol disciplines. Microbial control usuallyindicates biological control of invertebratesusing microbes and, as such, is a subdivisionof biological control. Use of additionalauxiliary terms such as biopesticide isdiscussed.
Numerous studies have examined the responses of pest and beneficial arthropods to plant diversification in ephemeral cropping habitats. Cruciferous crops, mainly cabbage and broccoli, are probably the most studied plants with respect to evaluating the impact of plant mixtures on insect population dynamics. This review examines the mechanisms influencing arthropod responses to floral diversification, specifically focusing on cruciferous crops. In many instances, mechanisms accounting for herbivores and natural enemy responses to plant mixtures are not thoroughly tested. Biological parameters of herbivores impacted by crop diversification were mainly related to the behavior of the insects studied. Mechanisms accounting for herbivore responses to plant mixtures include reduced colonization, reduced adult tenure time in the marketable crop, and oviposition interference. Tactics used for choosing companion plants, and the future perspective for mixed-crucifer crops usage are discussed. Manipulative studies involving cruciferous crops provide some evidence that habitat manipulation techniques (e.g., intercropping, undersown nonhost plants, vegetation borders) impact crop growth. However, the indirect role habitat manipulation plays in the population dynamics of insect pests and natural enemies still remains unclear in many systems. Quantitative data are needed to determine the level of change in plant quality brought about by companion planting that alters arthropod behavior.
The occurrence of deuteromycetous entomopathogenic fungi was examined in 266 soil samples representing 86 locations across temperate and near northern habitats in Ontario, Canada. Entomopathogenic fungi were isolated by baiting the soil with waxworm larvae, Galleria mellonella L., and incubating at 8, 15, or 25 degrees C. Entomopathogenic fungi were isolated from 91% of the locations sampled across Ontario. The most abundant species were Metarhizium anisopliae (Metschn.) Sorok. (357 isolates) and Beauveria bassiana (Bals.) Vuill. (187 isolates). Thirteen isolates of Paecilomyces spp. were also found. Beauveria bassiana was isolated more frequently in soils from near northern locations, relative to M. anisopliae. Beauveria bassiana was isolated more frequently from larvae baited in soils incubated at 8 and 15 degrees C, while M. anisopliae was isolated most frequently at 25 degrees C. Thus, B. bassiana is more psychrophilic than M. anisopliae. From 47 of the locations in a temperate area (southern Ontario and the Kawartha Lakes region), two sites, one from an agricultural habitat and one from a natural habitat, were sampled within 1 km of each other. In these locations, B. bassiana was predominantly recovered more often from soils of natural habitats, while M. anisopliae was recovered more often in agricultural habitats. The occurrence of M. anisopliae and B. bassiana was not related to soil type or pH.
The suppression of agricultural pests has often been proposed as an important service of natural enemy diversity, but few experiments have tested this assertion. In this study we present empirical evidence that increasing the richness of a particular guild of natural enemies can reduce the density of a widespread group of herbivorous pests and, in turn, increase the yield of an economically important crop. We performed an experiment in large field enclosures where we manipulated the presence/absence of three of the most important natural enemies (the coccinellid beetle Harmonia axyridis, the damsel bug Nabis sp., and the parasitic wasp Aphidius ervi) of pea aphids (Acyrthosiphon pisum) that feed on alfalfa (Medicago sativa). When all three enemy species were together, the population density of the pea aphid was suppressed more than could be predicted from the summed impact of each enemy species alone. As crop yield was negatively related to pea aphid density, there was a concomitant non-additive increase in the production of alfalfa in enclosures containing the more diverse enemy guild. This trophic cascade appeared to be influenced by an indirect interaction involving a second herbivore inhabiting the system – the cowpea aphid, Aphis craccivora. Data suggest that high relative densities of cowpea aphids inhibited parasitism of pea aphids by the specialist parasitoid, A. ervi. Therefore, when natural enemies were together and densities of cowpea aphids were reduced by generalist predators, parasitism of pea aphids increased. This interaction modification is similar to other types of indirect interactions among enemy species (e.g. predator–predator facilitation) that can enhance the suppression of agricultural pests. Results of our study, and those of others performed in agroecosystems, complement the broader debate over how biodiversity influences ecosystem functioning by specifically focusing on systems that produce goods of immediate relevance to human society.
The effects of mulching with organic materials on yield and damage by brassica root maggots (Delia floralis and D. radicum) in cauliflower, were studied in field experiments for 3 years. Mulching with grass-clippings consistently resulted in increased yield and reduced damage by root maggots, as measured by wilting symptoms and root damage. During one of these years, the effects of mulching with grass-clippings on root fly population dynamics was also studied. Mulching did not reduce egg-laying but resulted in increased egg-predation. The number of D. floralis pupae per plant was not reduced by mulching, probably because of higher larval mortality owing to competition in unmulched plots. Mulching decreased the rate of parasitization by Aleochara bilineata (Staphylinidae), resulting in a higher number of healthy pupae per plant in grass-mulched plots, and these healthy pupae were heavier. All these effects were most pronounced when the mulch material completely covered the ground, even close to the stems of the plants.
The chapter discusses the ecological/epizootiological basis for environmental manipulations, reviews research on this approach and the criteria to choose insect/entomopathogen systems for research and implementation. Research on environmental manipulation is focused on four areas. The first is improved transport from the pathogen reservoir, usually the soil, to a site such as a leaf surface where the insect host can come into contact with the entomopathogen. The second area is improvement in persistence of the entomopathogen at the site where it contacts the insect host. The third area is overall growth of the entomopathogen population, which depends on transmission and persistence as well as other factors. The fourth area is activation of latent infections. Many resource (crop)/pest systems include one or more entomopathogens that occur naturally and occasionally cause epizootics. Environmental manipulation has certain advantages over the approaches to microbial control that require environmental release of pathogen units because certain requirements for those approaches have caused major problems in implementation. The requirements for other approaches that are of little or no concern in environmental manipulation include market size (host specificity), cost of pathogen production, patentability, registration, persistence in storage, formulation, screening for efficacious species or strains, and habitat stability.
Aspects of the phenology and growth characteristics of stinging nettle are described which could be important for insects. Six habitat categories were contrasted by selecting nettle patches in shaded and unshaded conditions on clay, peat and sandy soils. The efficiency of suction sampling for Hemiptera (except aphids) and Coleoptera was examined and compared with the searching of cut-stem samples. Suction sampling was used to build up a general phenological picture of adult insects in preparation for an intensive study of one site and a comparison of nineteen sites in contrasting habitats. The life histories and habitat preferences of fourteen Heteroptera, five Homoptera and seven Coleoptera are described, including monophagous and polyphagous plant feeders and a few predatory species common on nettle in East Anglia. Several gaps in the information still remain and these are pointed out. The repuirements of the phytophagous species are discussed in relation to the successful exploitation of nettle by so many species. The comparison of insect faunas in different habitats in this study provides a basis for comparing other sites with respect to regional, climatic and biotic factors.
This paper reviews two aspects of agricultural biodiversity. 1. The ways in which agricultural biodiversity may be increased to favour pest management are examined. At the simplest level, the structure within a monoculture may be altered by changing management practices to benefit natural enemies. At the other extreme, annual and perennial non-crop vegetation may be integrated with cropping, and biodiversity increased at the landscape level. 2. The existence of a hierarchy for the types of benefits of increased biodiversity is discussed. Vegetational diversity can lead to suppression of pests via 'top-down' enhancement of natural enemy populations and by resource concentration and other 'bottom-up' effects acting directly on pests. Whilst such low-input pest management mechanisms are attractive in their own right, other (non-pest management related) benefits may simultaneously apply. These range from short-term benefits in crop yield or quality, longer term benefits for sustainability of the farming system and, ultimately, broad societal benefits including aesthetics, recreation and the conservation of flora and fauna. Examples are given of such multi-function agricultural biodiversity.
The influence of three formulations (water, oil, and a 5% oil emulsion) and two canopy positions (top and middle) on the persistence of conidia of Beauveria bassiana on phylloplanes of alfalfa (Medicago sativa) and crested wheatgrass (Agropyron cristatum) was investigated. Penetration into the canopy and coverage of leaves by conidia in oil applied with an ultralow volume (ULV) applicator was equal to that of conidia formulated in water-Tween or the oil emulsion applied at high volumes. Numbers of B. bassiana recovered from the top of the canopy immediately following application ranged from 8.3 × 103 to 1.2 × 105 colony-forming units (cfu)/cm2 for alfalfa and 5.1 × 103 to 3.5 × 104 cfu/cm3 for wheatgrass. In alfalfa, but not wheatgrass, the canopy influenced penetration of conidia as evidenced by the significant effect of sampling height. Conidia were relatively short lived on leaves at the top of the canopy in both crops and, by 4 days, conidial populations were reduced by more than 75%. At the middle of the canopy, conidia persisted longer on phylloplanes of both crops. This observation was more pronounced in alfalfa than in wheatgrass; at 16 days populations were reduced by more than 99% on wheatgrass leaves and by 28 to 85% on alfalfa leaves. Formulation had no obvious effect on the persistence of conidia. Mortality of grasshopper nymphs (Melanoplus sanguinipes) fed leaves sprayed with conidia from the top of the canopy corresponded to the conidial population data. Immediately after application of conidia, nymph mortality attributed to B. bassiana ranged from 31 to 58%, whereas mortality of nymphs fed leaves 2 days postapplication of conidia ranged from 0 to 5.5%. Methods to increase the persistence of conidia are required if plant surfaces are targeted in a strategy to control grasshoppers with B.bassiana.
By baiting soil samples with larvae of Galleria mellonella detailed surveys of the occurrences of entomopathogenic fungi were conducted over two consecutive years in the soil of an organically farmed field (17.1ha) and the associated hedgerow. Samples were collected at specific points (at distances of 25m) based on Geographical Information Systems (GIS) and sample point coordinates were relocated by Global Positioning System (GPS). In the agricultural field soil Beauveria bassiana was the most common fungus while Paecilomyces fumosoroseus was most common in soil from the hedgerow. Significant clustering of B. bassiana in the agricultural field was found in one of the two years. High and low densities of B. bassiana were subsequently confirmed within selected areas by reducing distances between sample points. The results demonstrated the suitability of the sampling method for identifying distribution patterns of soil borne entomopathogenic fungi and the importance of large sample sizes to describe local biodiversity of the fungi in the soil environment.
1 Pandora neoaphidis is an important aphid‐specific fungal pathogen in temperate agroecosystems. Laboratory studies were carried out to obtain baseline data on factors that may affect its performance in conservation biological control.
2 Virulence of P. neoaphidis was assessed in dose–response bioassays against Microlophium carnosum on nettle, Uroleucon jaceae on knapweed, Acyrthosiphon pisum on bean and bird's‐foot trefoil Lotus corniculatus , and Metopolophium dirhodum on barley and Yorkshire fog Holcus lanatus . The most susceptible aphid was A. pisum feeding on bean with an LD 50 of 19 conidia per mm ² , whereas U. jaceae had an LD 50 of 104 conidia per mm ² and was least susceptible to infection.
3 The presence of foraging adult ladybirds, Coccinella septempunctata , increased transmission of P. neoaphidis from infected cadavers to apterae of M. carnosum, U. jacea, and A. pisum by 7–30% at the largest cadaver density tested. Adult coccinellids that had previously foraged on nettle, knapweed, bean or bird's‐foot trefoil transfered conidia to A. pisum on bean and induced infections in 2–13% of aphids.
4 Conidia of P. neoaphidis dispersed passively in the airstream from sporulating M. carnosum cadavers on nettle plants and initiated infections in A. pisum colonies feeding on bean (4–33%) or M. dirhodum on barley (3%) located within 1.0 m of the nettle source.
5 The results suggest that M. carnosum and A. pisum may be more useful as reservoirs for P. neoaphidis in noncrop and crop areas than U. jaceae or M. dirhodum , and infection and dispersal between habitats could be enhanced in the presence of coccinellids.
When Spodoptera exigua pupae were buried for 10 days at 24°C in nonsterile soil inoculated with Beauveria bassiana conidia, 1 × 107 conidia/cm3 of soil was the lowest conidial density to produce disease in pupae and adults. At water potentials of −37 and −200 bars (24°C), adult emergence was reduced when 3.2 × 107 or 1 × 108 conidia/cm3 was used in Yolo fine sandy loam (YFSL) and Staten peaty muck (peat). In these dry soils, adult emergence was as low as 6% at 1 × 108 conidia/cm3. At water potentials of −0.3, −2, and −15 bars, a concentration of 1 × 108 conidia/cm3 was necessary to reduce adult emergence. In these treatments, 18 to 62% of the pupae eclosed to the adult stage. Thus, adult emergence was greater at water potentials from −0.3 to −15 bars that at −37 and −200 bars. Also at −0.3 and −2 bars, adult emergence was greater in peat than in YFSL. Uninoculated control soils had 85–94% adult emergence. Adult emergence increased as the temperature decreased from 25° to 8°C. At 8°C, adult emergence was the same in inoculated and uninoculated soil. Clay-coating of conidia, to increase conidial longevity, did not influence S. exigua mortality.
A method for baiting soil samples with Delia floralis larvae was developed, and a systematic survey was conducted on soils from northern Norway for insect pathogenic fungi, using D. floralis and Galleria mellonella larvae as bait. The occurrence of insect pathogenic fungi in soils from arable fields and adjacent field margins of conventionally and organically managed farms was compared. The study showed a significantly higher occurrence of insect pathogenic fungi in soils from arable fields of organically managed farms. No significant differences in the occurrence of insect pathogenic fungi were, however, found between the field margins of the two cropping systems. Fungal species identified in the study were Beauveria bassiana, Fusarium merismoides, Metarhizium anisopliae and Tolypocladium cylindrosporum.T. cylindrosporum was found more frequently when using D. floralis as the bait insect than when using G. mellonella.
The occurrence of entomopathogenic fungi and nematodes was measured in samples of soil collected from cultivated and uncultivated habitats in Warwickshire, UK. Fungi and nematodes were isolated from the samples of soil by “baiting” with larvae of the wax moth, Galleria mellonella (Lepidoptera: Pyralidae). Following two pilot experiments, a main study was done using soil collected from an arable field, a network of hawthorn hedges and four mature woodlands. 70 isolates of entomopathogenic fungi were obtained from 400 samples of soil. Hyphomycete fungi (15.8% occurrence) were isolated from significantly more samples of soil than entomophthoralean fungi (1.8% occurrence, P < 0.01). The two more common species of fungi were Beauueria bassiana (6.0% occurrence) and Paecilomyces farinosus (5.0% occurrence). Entomopathogenic fungi were isolated from significantly more samples of soil from the woodland and hedgerow habitats than from the arable field (P < 0.01). There was also a significant difference in the occurrence of entomopathogenic fungi between the four woodlands (P < 0.05). 17 isolates of entomopathogenic nematodes (4.3% occurrence) were identified by RFLP analysis, including two species of Steinernema: S. feltiae and an unnamed species designated Steinernema sp. C1. Overall, nematodes were isolated from significantly more samples of soil from hedgerow and woodland than from the arable field (P < 0.01).
Fungal pathogens are capable of causing sensational levels of mortality in insect populations. As early as about 1000 AD, sericulturists in Asia reported Beauveria bassiana infections in silkworms (Steinhaus, 1956). The “germ theory of disease,” the concept that microbes can cause disease, was first experimentally proven by Agostino Bassi in 1834 working with B. bassiana and silkworms. From the late 1800s through 1925, research on the potential use of fungi for insect control was conducted. In recent years, largely due to our present knowledge of the hazards and inefficiencies of dependence on synthetic chemical pesticides for insect control, interest in developing fungal pathogens for control purposes has increased dramatically (Roberts and Hajek, 1992; Vandenberg, 1993). Although abundant research on use of entomopathogenic fungi for control has been conducted, there are major gaps in our understanding of the basic ecology of these fungal species, in part due to the complexity of host/pathogen/environment interactions and the diversity of host/pathogen systems to be studied. Lack of successful control in some systems and difficulties in adapting some species for typical control practices has promoted a shift in research emphasis. At present, some research efforts are directed toward understanding the factors leading to fungal infection in insects in order to investigate the potential for manipulating these systems to enhance levels of infection and promote development of epizootics (disease outbreaks).
The potential of adult and larval C. septempunctata to vector the aphid-specific entomopathogenic fungus E. neoaphidis was assessed through a series of laboratory and field experiments. The ability of coccinellids to vector conidia from a colony of E. neoaphidis -infected pea aphids, Acyrthosiphon pisum, to a colony of uninfected A. pisum was demonstrated in a laboratory study. Adult coccinellids which had previously foraged on plants infested with different densities of sporulating cadavers (1, 5, 15, 30 cadavers per plant) initiated infection in a proportion of uninfected pea aphids (4, 0, 2 and 8%, respectively) when subsequently allowed to forage on A. pisu