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Abstract
Keller, S. (1997). The genus Neozygites (Zygomycetes, Entomophthorales) with special reference to species found in tropical regions. - Sydowia 49(2): 118-146. Several collections of mites (Acari: Tetranychidae, Phytoseiidae), mealybugs (Homoptera: Pseudococcidae) and aphids (Homoptera: Aphididae, Lachnidae) infected with Entomophthorales mainly from West Africa, South America and the Philippines were examined. All fungi found on Tetranychidae including the green cassava mite, Mononychellus tanajoa, were assigned to N. floridana. Species found on the phytoseiid Euseius citrifolius were identified as N. acaricida comb. nov. and N. cf. acaridis, respectively. All material from mealybugs (Rastrococcus invadens and Coccidohystrix insolita) was identified as N. fumosa. An emended description of this species is given. The fungi from Aphis craccivora and A. fabae were identified as N. fresenii. A new species, N. cinarae attacking the lachnid Cinara pilicornis, is described. The life-cycles of N. floridana and N. fresenii are described and compared. A key to all known species and a short characterisation is provided.
... Neozygites species are important natural enemies that may control arthropod populations under microclimatic conditions favorable for the fungus (Latgé & Papierok 1988;Barta & Cagáň 2003, 2006aKlingen & Westrum 2007;Castro et al. 2013). Generally, most Neozygites species can be divided into two subgroups (Neozygites fresenii-type or Neozygites floridana-type) based on their morphologies and life cycles (Keller 1997(Keller , 2006Delalibera et al. 2004). Their narrow host specificity makes them valuable control agents that present a negligible threat to non-target organisms (Barta 2004). ...
... Brown cadavers filled with vegetative cells and hyphal bodies were incubated at 25 °C in moist chambers (plastic containers and moistened filter paper) to induce external conidiogenesis. Neozygites species were identified based on morphology according to Keller (1991Keller ( , 1997. ...
... & S. Keller (on thrips) and N. lageniformis (on aphids) were observed infecting natural arthropod populations (Aruta et al. 1984, Aruta & Carrillo 1989. Neozygites parvispora is a widespread fungal parasite of various thrips species with a primarily European distribution (Bałazy 1993, Keller 1997. Neozygites lageniformis is rare and incompletely described species from the New World (Thaxter 1888, Aruta & Carrillo 1989, previously observed only twice (in aphids in United States of America and Chile). ...
Three species of Neozygites were recorded during a 2007–13 survey of the occurrence of the genus on aphids in Chile. Neozygites osornensis is known from recent studies, and N. fresenii and N. cinarae are reported as new records for Chile. Neozygites
lageniformis, which was not found during the survey, had been recorded previously in Chile. Morphological descriptions, symptoms on infected insects, host spectrum, and geographical distribution of all four species are presented, and a key to Neozygites species associated with aphids
in Chile is included. These fungi, which are important natural enemies of aphids, may be considered for future aphid pest control.
... According to Humber (2012), an extensive amount of data is still needed to reveal important information about the classification and biology of Neozygites. The species Neozygites floridana (Entomophthoromycota: Neozygitales: Neozygitaceae) belongs to this genus and is pathogenic to several species of mites in the family Tetranychidae (Keller, 1997). For N. floridana, important information about fungal structures, especially the formation of azygospores, still remains to be fully confirmed. ...
... According to Keller (1991Keller ( , 1997 and Keller and Petrini (2005) Neozygites resting spores are dark brown to black, spherical or ellipsoid, smooth or ornamented and binucleate, while resting spores of many other Entomophthoromycota are multinucleate (Keller and Petrini, 2005). Keller (1997Keller ( , 2007 further suggests that a zygospore is developed by budding from a conjugation bridge after a conjugation of two hyphal bodies (Fig. 1). ...
... According to Keller (1991Keller ( , 1997 and Keller and Petrini (2005) Neozygites resting spores are dark brown to black, spherical or ellipsoid, smooth or ornamented and binucleate, while resting spores of many other Entomophthoromycota are multinucleate (Keller and Petrini, 2005). Keller (1997Keller ( , 2007 further suggests that a zygospore is developed by budding from a conjugation bridge after a conjugation of two hyphal bodies (Fig. 1). During the early development of the young zygospore it receives one nucleus from each hyphal body (Keller, 1997;Humber, 1989). ...
Neozygites floridana is an obligate fungal pathogen of mites in the family Tetranychidae and is an important natural enemy of the two-spotted spider mite (Tetranychus urticae). Until now, information about the formation of azygospores remained to be fully confirmed. In this study, we document the formation of azygospores by a Brazilian N. floridana strain and the formation of azygospores and zygospores by a Norwegian N. floridana strain both in the host T. urticae. Evidence of both zygosporogenesis and azygosporogenesis was also found in the same individual in the Norwegian stains. Further we report the presence of immature azygospores with 1-3 nuclei for the Norwegian strains, immature resting spores (probably azygospores) with 1-8 nuclei for the Brazilian strain, and mature resting spores with 2 nuclei for both the Norwegian and the Brazilian strains (azygo- or zygospores). Our observations suggest that the immature resting spore (prespore) of both strains begins in a multinucleate condition but that the nuclear number is reduced during maturation until mature resting spore is binucleate regardless of its origin as a zygospore or azygospore.
... The results of the PCR were sent to Macrogen Inc. for Sanger sequencing. The sequences were processed for purification using the BioEdit (v.7.2.5;1997 program and aligned using the Mega X v. 10.1.8 (1995-2018) program with sequences deposited in GenBank. ...
... Identity of the fungus. Keller (1997) listed the primary structures for the identification of N. floridana as rounded hyphal bodies (or rounded at some end), unbranched conidiophores, oblong or spherical primary conidia with three to eight nuclei, capillary tube capilliconidia, and zygospores ellipsoid or spherical, binucleate, and dark brown in color reaching black. Azygospores are rarely found, and cystidia and rhizoids are absent. ...
Tetranychus urticae (Koch) (Trombidiformes: Tetranychidae) is a cosmopolitan spider mite species that infests more than 900 species of plants, including commercial species. Tetranychus cinnabarinus (Boudreaux) is characterized by a red coloration, in contrast to the green-colored T. urticae. Both are occasionally found coexisting in warm environments, and, for that reason, they are considered by some to be synonyms. In this study, we identified specimens of the two morphospecies using optical and electron microscopy and amplification of a segment of the mitochondrial cytochrome oxidase I (COI) gene. Bioassays determined the level of susceptibility and survival of both morphospecies when they were infected with the entomopathogenic fungus Neozygites floridana (Weiser and Muma). For the evaluation of the susceptibility of these morphospecies to N. floridana, bioassays were conducted under conditions of 25 ± 2°C, 60 ± 5% relative humidity, and a 12:12-h photoperiod regime. From these bioassays, we found that T. cinnabarinus was less susceptible to N. floridana and that there is a higher level of fertility, survival, and development in the T. cinnabarinus than in the T. urticae mites. Within a mass rearing system, T. cinnabarinus appears be a more efficaceous functional food for predatory mites, such as Phytoseiulus persimilis (Athias-Henriot) (Mesostigmata: Phytoseiidae), than T. urticae to support rearing and release of biological agents for integrated pest management.
... The genus Neozygites Witlaczil (1885) includes species with spherical or rod-shaped hyphal bodies; unbranched conidiophores; spherical to obovate primary conidia with 3-8 nuclei; presence of capilliconidia with typically bent capillary tubes; spherical or ellipsoidal, binucleate, dark brown to black zygospores, rarely azygospores; cystidia always absent, rhizoids usually absent (Keller 1997). This genus comprises species with relatively narrow host ranges, all of which have been found in small arthropods such as aphids (Homoptera), thrips (Thysanoptera) and mites (Acari) (Keller 1991, Keller andSteenberg 1997). ...
... The size of hyphal bodies and primary conidia, together with the collembolan host, distinguishes this species from other resembling species. The key by Keller (1997) was used together with subsequent literature to confirm the identification. Senior researcher Tove Steenberg at Aarhus University, Department of Agroecology and coauthor of the species, indicated a possible correct identification of Neozygites sminthuri based on photos of primary conidia, specifying the absolute need of microscopy imaging and measurements of dyed hyphal bodies for verification of the identification. ...
During a field trip outside of Oslo, a springtail of the family Isotomidae was collected and microscopically investigated. We found the specimen to be infected with the fungal species Neozygites sminthuri (Neozygitales: Neozygitaceae). The species is new to Norway and is rarely investigated internationally. Also, it has not been registered on a host species of this family of springtails earlier. The collection is presented with photos and notes on its anatomy, ecology and occurrence in Scandinavia.
... It actively discharges larger non-infective primary conidia. These primary conidia then produce secondary sticky infective conidia on long capillary tubes, so called capilliconidia (Keller 1997). It only takes one capilliconidium to kill a spider mite (Oduor et al. 1995), and one Tetranychus cadaver may throw more than 2000 primary conidia (Wekesa et al. 2010), which germinate into infective secondary capilliconidia. ...
... The primary conidium of N. floridana germinates into an infective sticky capilliconidium on a long capillary that will rise 60-100 µm above the leaf surface (Keller 1997;Trandem et al. 2015). Capilliconidia easily break off and can attach to the body and legs of host and non-host arthropods (Delalibera et al. 2003). ...
We determined how conidia of arthropod-pathogenic fungi on leaves affected the behavior of two predators—Orius majusculus (Hemiptera: Anthocoridae) and Phytoseiulus persimilis (Acari: Phytoseiidae)—when offered a choice between preying on two-spotted spider mites, Tetranychus urticae (Acari: Tetranychidae), in the presence or absence of infective conidia of Metarhizium brunneum (Ascomycota: Hypocreales) and Neozygites floridana (Entomophthoromycota: Neozygitaceae). The results indicate no significant relation between the presence of conidia and predator behavior. The only indication of interference is between the generalists O. majusculus and M. brunneum, with a trend towards more time spent feeding and more prey encounters turning into feeding events on leaf discs without conidia than on leaf discs with conidia. Our results show that the presence of fungal conidia does not alter the preying behavior of the predators, and using predators and fungi together is not limited by any interference between organisms in the short term.
... Research on Neozygites species in natural ecosystems has been limited, particularly in comparison to that reported worldwide for other aphid-specific entomophthoralean species in Pandora, Conidiobolus, Entomophthora, andZoophthora (Barta &Cagáň 2006, Keller 2006 (Keller 1997) and described Neozygites remaudierei S. Keller from Myzocallis coryli (Keller 2006). Barta (2009) reported eighteen species of aphids on woody plants infected by N. fresenii and one species infected by Neozygites cinarae in the Mlyňany arboretum in Slovakia. ...
... The fungus was identified based on morphological characteristics according to Keller (1991Keller ( , 1997 and Humber (2012a). Semi-permanent slide mounts were prepared in lactophenol-aceto-orcein (LPAO) as described by Keller (1987) and deposited in the Forest Insect and Disease Herbarium, Zhejiang Agricultural and Forestry University, Lin'an, China (ZAFU). ...
Neozygites linanensis sp. nov. was identified as infecting the aphid Takecallis taiwanus collected on bamboo plants, Chimonobambusa quadrangularis, in the Lin'an region of southeast China during spring and summer 2014. This is the first record of a Neozygites species on T. taiwanus. The Chinese Neozygites specimen is described, illustrated, and discussed. The phylogenetic relationship among selected Neozygites species is evaluated based on the successful sequence of the SSU rDNA gene from the new fungus.
... Despite using several different taxonomies, some useful general works to identify many entomopathogenic species include MacLeod & Müller-Kögler (1973), Keller (1987Keller ( , 1991Keller ( , 1997Keller ( , 2002, and Ba1azy (1993). After a long and spirited debate about the familial and generic taxonomy of Entomophthorales (summarized in Humber 1981Humber , 1989, the most widely accepted and used current taxonomy for this order recognizes six families in this order (Humber 1989), at least two of which (Neozygitaceae and Entomophthoraceae) are obligatorily pathogenic for arthropods. ...
... c. Main taxonomic literature Keller, 1991Keller, , 1997Keller, , 2007Ba1azy, 1993. 9. Pandora Humber (Figure 6.13) ...
... The major characters traditionally used to classify the Entomophthorales have been thoroughly reviewed (summarized in Humber 1975Humber , 1981Humber , 1982Humber , 1984 and were applied to six families in the last major reclassification of Entomophthorales (Humber 1989); this taxonomy is widely accepted despite a few minor differences in the treatments of some entomopathogenic genera (Bałazy 1993;Keller 1987Keller , 1991Keller , 1997Keller & Petrini 2005). Until now, however, there have not been phylogenetic studies on a sufficiently broad range of their genes and taxa to propose a more contemporary revision. ...
... Distinct differences between neozygitoid fungi and either basidioboloid or entomophthoroid taxa supports the description of three classes in this new phylum: As in basidioboloid fungi, neozygitoid fungi exert strong control in vegetative cells over nuclear number (usually four in Neozygites), have a central mitotic metaphase plate (Butt & Humber 1989), and, perhaps most significantly, a round of mitosis in gametangial cells precedes conjugation and zygosporogenesis while only one nucleus from each gametangium enters each zygospore (Keller 1997). As in entomophthoroid fungi, all neozygitoid taxa are obligate pathogens of insects or mites, and the nuclear membrane remains intact throughout mitosis. ...
One result of the recent phylogenetically based rejection of the phylum Zygomycota was the description of the subphylum Entomophthoromycotina (not assigned to any phylum) for fungi traditionally treated in the order Entomophthorales. More extensive gene-based analyses
of these fungi suggest that they represent a monophyletic lineage distinct from all other fungi that deserves now to be recognized at the level of a new fungal phylum. These molecular data and further analyses of more traditional taxonomic criteria lead to this reclassification that still
treats these fungi in six families but recognizes the new classes Basidiobolomycetes, Neozygitomycetes, and Entomophthoromycetes as well as the new order Neozygitales. Ballocephala and Zygnemomyces are excluded from Entomophthorales (Meristacraceae)
and should be reclassified among the Kickxellomycotina.
... Furthermore, intensive studies on entomophthoroid fungi contribute to the understanding of their epizootiological potential, phenology and management in agricultural crops (Pell et al., 2001). Entomophthoroid fungi often cause epizootics that may dramatically reduce aphid densities (Steinkraus et al., 1995), with approximately 30 species known to cause mycoses in aphid populations (Humber, 1991;Keller, 1991Keller, , 1997Keller, , 2006Bałazy, 1993). Unlike several fungal-cereal aphid associations reported from other countries (Feng et al., 1992;Hatting et al., 1999;Barta & Cagáň, 2003a,b) such associations remain largely unexplored in South America (Lázzari, 1985), with most reports limited to other insect hosts Sosa-Gómez et al., 2010). ...
... Neozygites fresenii has been recorded on all continents (Bałazy, 1993;Keller, 1997) and exhibits a strong tendency to establish epizootics in dense aphid colonies. In agreement with the findings of , N. fresenii was detected only in autumn and, in this study, affected only a single species of aphid except in horticultural rather than cereal crops. ...
The spectrum of entomophthoroid fungal species parasitising aphids on cereal crops and a study of the phenology and prevalence of these pathogens were investigated in Argentina. The studies were conducted at six different sites cultivated with crops of Triticum aestivum (wheat), Avena sativa (oats) and Sorghum bicolor (sorghum) during two consecutive years. Entomopathogenic fungi from the new phylum Entomophthoromycota were recorded from six aphid species on cereals in Argentina: Rhopalosiphum maidis, Rhopalosiphum padi, Rhopalosiphum rufiabdominalis, Schizaphis graminum, Sitobion avenae and Sipha maydis. Three species of entomophthoroid fungi were found infecting these aphid species: Pandora neoaphidis, Zoophthora radicans (Entomophthorales: Entomophthoraceae) and Neozygites fresenii (Neozygitales: Neozygitaceae). Entomophthoroid fungal infections occurred mostly in autumn–winter seasons (March–August), and coincided with periods of high relative humidity and comparatively low temperatures. This study represents the first base-line characterisation of entomophthoroid fungi infecting aphids on cereal crops in Argentina.
... Fungi in this genus attack small arthropods such as mealybugs, aphids, thrips, and mites [2]. Neozygites floridana (Weiser and Muma)Remaudì ere and Keller is pathogenic to several species of plant-feeding spider mites [3] , and it is an important natural enemy of the twospotted spider mite, Tetranychus urticae Koch, and the red tomato spider mite, Tetranychus evansi Baker and Pritchard (Acari: Tetranychidae)456. For many of the fungal species within the Entomophthoromycota , zygospores and azygospores are important for fungal survival during periods of adverse conditions (e.g., winter, dry season, or host absence), and they are therefore called resting spores [7]. ...
... We also included an experiment where mites were coinfected with two strains of the fungus to test the effect of heterothallism on resting spore production. The nature of N. floridana resting spores is still unknown; Humber [24] affirms that there is evidence of heterothallism within the Entomophthoromycota, but Keller [3] suggested that there are indications that Neozygites fresenii might be heterothallic. ...
Neozygites floridana is an obligate mite pathogenic fungus in the Entomophthoromycota. It has been suggested that resting spores of this fungus are produced as a strategy to survive adverse conditions. In the present study, possible mechanisms involved in the regulation of resting spore formation were investigated in the hosts Tetranychus urticae and Tetranychus evansi. Abiotic and biotic factors mimicking conditions that we, based on earlier field studies, thought might induce resting spores in temperate and tropical regions were tested with isolates from Norway and Brazil. A total of 42 combinations of conditions were tested, but only one induced the formation of a high number of resting spores in only one isolate. The Brazilian isolate ESALQ1420 produced a large number of resting spores (51.5%) in T. urticae at a temperature of 11°C, photoperiod of 10L:14D, and light intensity of 42-46 ( μ mol m(-2) s(-1)) on nonsenescent plants (nondiapausing females). Resting spores of the Brazilian N. floridana isolate ESALQ1421 were found at very low levels (up to 1.0%). Small percentages of T. urticae with resting spores (0-5.0%) were found for the Norwegian isolate NCRI271/04 under the conditions tested. The percentages of resting spores found for the Norwegian isolate in our laboratory studies are similar to the prevalence reported in earlier field studies.
... Numerosas publicaciones registran en el mundo la presencia de hongos Entomophthorales infectando insectos plaga de la agricultura (Keller, 1997;Alzugaray et al., 1999;Hatting et al., 1999, Nielsen et al., 2001Sánchez et al., 2001Steinkraus & Boys, 2005). En la Argentina, el conocimiento de los hongos Entomophthorales es escaso y su distribución geográfica es poco conocida (Fresa, 1979;Edelstein & Lecuona, 2003;López Lastra & Scorsetti, 2006;. ...
... Las estructuras fúngicas fueron visualizadas bajo un microscopio óptico con contraste de fases (400x) (Olympus CH30) y fotografiadas con una cámara digital (Sony DSC-P73). Los datos merísticos de las estructuras vegetativas y reproductivas del hongo: conidios (ancho y largo), conidióforos (ancho), hifas (ancho), fiálides (ancho mayor y largo) fueron obtenidos para realizar la identificación y caracterización de la especie fúngicas hallada, comparando las mediciones obtenidas con las claves correspondientes (Balazy, 1993;Keller, 1997). En cada serie fueron medidas 25 unidades como mínimo, obteniendo el promedio de la misma, desvío estándar, medidas mínimas y máximas. ...
First record of Neozygites sp. (Zygomycota: Entomophthorales), pathogen of Tetranychus urticae (Acari: Tetranychidae) in Argentina. In this paper, the presence of the fungi Neozygites cf. floridana (Zygomycota: Zygomycetes: Entomophthorales), as pathogen of the mite Tetranychus urticae (Acari: Tetranychidae), is recorded for first time in Argentina. Samplings were carried out in La Plata, on tomato, pepper, egg-plant, and other horticultural crops. Microscopic slides and mites infected were placed in the Herbarium of the Institute of Botany C. Spegazzini and in the Herbarium of CEPAVE. This work contributes to further expand the distribution and the host range of Neozygites as well as the information of entomopathogenic fungi in Argentina.
... De même, à l'étape actuelle des connaissances, l'isolement à partir de R. invadens des six (06) espèces mentionnées dans les résultats de la présente étude devrait être considéré comme nouveau. En effet, les espèces fongiques qui ont été jusque-là isolées à partir de ce ravageur sont Hirsutella cryptosclerotium (Fernandez-Garcia, 1990) et Neozygites fumosa (Keller, 1997). L'identification des espèces isolées a été faite par comparaison de leurs caractéristiques (macroscopiques et microscopiques) à celles décrites dans les travaux antérieurs. ...
Objective: The objective of this study was to identify the entomopathogenic fungi associated with mango mealybug (Rastrococcus invadens), an economically important insect pest in Burkina Faso.
Methodology and results: Dead mealybugs showing symptoms of fungal infection were collected from mango trees and incubated in the laboratory. The pathogenicity of the isolated fungi was tested on R. invadens in the laboratory, using for each species a concentration of 10 8 spores/ml. Six (06) species of fungi were isolated: Aspergillus sp. 1, Aspergillus sp. 2, Alternaria sp., Curvularia sp., Fusarium sp. and Metarhizium sp.. They were all virulent against R. invadens. The species Aspergillus sp. 1 and Metarhizium sp. caused the highest mortality rates (12.31% to 100%) with respective TL50s of 4.89 days and 3.78 days.
Conclusion and application of findings: The species of fungi isolated from dead individuals of R. invadens are all entomopathogenic on this insect pest. In view of the high mortality rates obtained with Aspergillus sp. 1 and Metarhizium sp., these two species of fungi can be more studied in view to develop biopesticides against R. invadens. The fungi strains collected can be tested on fruit flies, which are also a major constraint to mango production in Burkina Faso.
Keywords: Isolate, entomopathogenic fungus, mealybug, biological control, Burkina Faso.
... Despite their many aforementioned advantages, the fungi from Entomophthorales have often been reported to be difficult to grow in vitro (Eilenberg et al., 1992;Hajek et al., 2012;Jaronski, 2014;Latgé, 1981;Papierok & Hajek, 1997;Pell et al., 2001). By their individual requirements for in vitro growth, the different entomophthoralean genera can be categorised into four groups (Keller, 1997;Latgé, 1981;Pell et al., 2001): The first group can be easily grown in classical mycological media, such as Conidiobolus spp. (Latgé et al., 1983(Latgé et al., , 1985. ...
Pandora sp. nov. inedit. (ARSEF13372) is a recently isolated
entomophthoralean fungus with high potential for psyllid pest
control. The use of entomopathogenic fungi as biocontrol agents
in large-scale field application requires biomass production in a
sufficient quantity and quality. This work is the first attempt to
explore the biomass production of the novel entomophthoralean
Pandora species in a liquid medium. This study aims at
establishing a submerged fermentation process with potential for
mass production of the fungus. Three different complex nutrient
sources were evaluated for maximising biomass in a liquid
shaking culture. Pandora sp. nov. grew best in media containing
skimmed milk, but even faster in a mixture of skimmed milk,
yeast extract and a low-cost protein hydrolysate from animal byproducts. Subsequently, the produced biomass can be
encapsulated in biopolymer beads or granules in order to transfer
the fungus into an easily applicable form. Therefore, growth as
finely dispersed mycelium was promoted by increased media
osmolality through the addition of sodium chloride. After the
medium had been transferred to a stirred tank bioreactor with a
working volume of 8 L, a maximum biomass dry weight of
21 g·L−1 was reached after 48 h. These promising results can pave
the way for large-scale fermentation and formulation processes of
this novel Pandora species for biological psyllid pest control.
... Beauveria brongniartii (Saccardo) Petch [Deuteromycotina, Hyphomycetes] is an insect pathogenic fungus, considered the most important pathogen effective against European cockchafer, Melolontha melolontha L. (Coleoptera: Scarabaeidae) (Keller 1997). It is commercially used as a microbial control agent for the management of larvae of M. melolontha in grasslands and orchards. ...
Entomopathogenic fungi form an essential component of the integrated insect-pest management strategies. The insect-pests and their entomopathogenic fungi have co-evolved over centuries and thus established an equilibrium. Species of Metarhizium, Lecanicillium, Nomuraea, Isaria, etc. have been studied extensively, and the commercial products based on Nomuraea rileyi, Lecanicillium (Verticillium) leccanii, Beauveria bassiana and Metarhizium anisopliae are popular among farmers. Several modes of action of these fungi against target pests have been elucidated. Introduction of pesticides has not only undermined the value of these fungi but also disturbed the equilibrium. The entomopathogenic fungi are living organisms formulated and delivered to the farming community for the management of target insect-pests. Due to the lag in realizing the benefit of these biocontrol agents, the farmers started using the pesticides which show their effect immediately. While on one side, indiscriminate use of these pesticides in the last three decades has led to the loss of biodiversity of beneficial organisms, pollinators, other animal and bird species; on the other side, emphasis on organic agriculture has compounded the value of these products. Thus, the interest in these biocontrol agents has re-invigorated. Several commercial formulations are already used by the farming community for the management of insect-pests. In this review, an attempt was made to appraise the status of these entomopathogenic fungi, their commercial exploitation, research gaps and way forward.
... The entomopathogenic fungal genus Neozygites belongs to the order Neozygitales in the class Neozygitomycetes in the phylum Entomophthoromycota [1]. Fungi in this genus infect small arthropods such as mealybugs, aphids, thrips, and mites [2,3]. Natural epizootics of Neozygites floridana have been documented in important mite pests of several major crops [4][5][6][7][8][9][10][11], including the two-spotted spider mite Tetranychus uricae (Acari: Tetranychidae), making the fungus an interesting candidate for conservation biological control [12]. ...
Neozygites floridana is a pathogenic fungus and natural enemy of the two-spotted spider mite, Tetranychus urticae (Acari: Tetranychidae), which is an important polyphagous plant pest. The aim of this study was to reveal and predict what combination of temperature, relative humidity (RH), and time that enables and promotes primary conidia production and capilliconidia formation in N. floridana (Brazilian isolate ESALQ 1420), in both a detached leaf assay mimicking climatic conditions in the leaf boundary layer and in a semi-field experiment. In the detached leaf assay, a significant number of conidia were produced at 90% RH but the highest total number of primary conidia and proportion of capilliconidia was found at 95 and 100% RH at 25 °C. Positive temperature and RH effects were observed and conidia production was highest in the 8 to 12 h interval. The semi-field experiment showed that for a >90% probability of N. floridana sporulation, a minimum of 6 h with RH >90% and 10 h with temperatures >21 °C, or 6 h with temperatures >21 °C and 15 h with RH >90% was needed. Our study identified suitable conditions for primary- and capilliconidia production in this Brazilian N. floridana isolate. This information provides an important base for building models of a Decision Support System (DSS) where this natural enemy may be used as a tool in Integrated Pest Management (IPM) and a base for developing in vivo production systems of N. floridana.
... The fungus was readily identifiable as a Neozygites species based on its morphological characteristics (Keller 1997, Humber 2012 These pathogens have provided natural control of different forestry and agricultural aphid pest without detriment to plants, beneficial arthropods, and vertebrates (Montalva et al. 2014). Neozygites species are not common and are among the most difficult to culture of all entomophthoroid fungi. ...
The woolly poplar aphid, Phloeomyzus passerinii, causes severe damage to poplars in Southern Europe and Asia, where outbreaks of this pest can lead to massive mortality of trees in mature stands. In Chile, this aphid was reported for the first time in 1997 in plantations of Populus nigra. During April 2016 and again in March 2017 (autumn season), several mycosed individuals were found attached to the poplars’ twigs. The fungus was identified as a Neozygites species by its characteristic morphology with subglobose primary conidia, 19.8 ± 0.4 × 16.1 ± 0.4 μm, with a small, flat papilla, produced on the surface of cadavers, and capilliconidia that are almond shaped but rarely observed, 21.7 ± 0.8 × 14.4 ± 0.6 μm. The resting spores were subglobose, 26.3 ± 0.5 × 21.2 ± 0.5 μm, black in mass, with a thick more or less smooth-surfaced wall, and formed inside the aphid. Neozygites comprises a relatively homogeneous group of species exclusively pathogenic to arthropods. Their narrow host ranges make them potentially valuable biocontrol agents. This is the first report worldwide of any Neozygites on P. passerinii.
... The fungus was readily identifiable as a Neozygites species based on its morphological characteristics (Keller 1997, Humber 2012 These pathogens have provided natural control of different forestry and agricultural aphid pest without detriment to plants, beneficial arthropods, and vertebrates (Montalva et al. 2014). Neozygites species are not common and are among the most difficult to culture of all entomophthoroid fungi. ...
... (Humber, 1997;Keller, 1997 ...
An entomopathogenic fungus was isolated from the two-spotted spider mite (Tetranychus urticae) in a rearing house, and identified as Neozygites floridana (Entomophthorales: Neozygitaceae). A high infection rate induced by N. floridana could increase the price of the natural enemy. The body color of mites infected by this fungus changed to red or orange and swelling occurred. Fungal conidia were discharged into the webbing produced by the spider mites, making it relatively easy to infect the mites. Primary conidia were pear shaped and capilliconidia almond shaped. The fungus could not be cultured on solid media (PDA, SDAY, or EYSDA), but could possibly be cultured in liquid media (Grace's insect tissue culture medium + 5% fetal bovine serum). Kidney beans were supplied as food for T. urticae; the mite infection rate in a kidney bean canopy was about 36.1%. The density of infected mites was higher on the underside than on the upper side of leaves. Based on the results of this survey, we need to identify methods of fungal control for natural enemy production and biological control agents for T. urticae for effective crop management.
... Fungi in this genus attack small arthropods such as mealybugs, aphids, thrips, and mites (Keller, 1991). Neozygites floridana is pathogenic to several species of plant-feeding spider mites (Keller, 1997). Natural epizootics of this fungus have been documented in important mite pests in the spider mite family (Tetranychidae) of several major crops (Duarte et al., 2009;Humber et al., 1981;Klubertanz et al., 1991;Nordengen and Klingen, 2006;Klingen et al., 2008;Boykin et al., 1984;Carner and Canerday, 1970;Smitley et al., 1986;Dick and Buschman, 1995;Mietkiewski et al., 1993Mietkiewski et al., , 2000. ...
... Fungi in this genus attack small arthropods such as mealybugs, aphids, thrips, and mites (Keller, 1991). Neozygites floridana is pathogenic to several species of plant-feeding spider mites (Keller, 1997). Natural epizootics of this fungus have been documented in important mite pests in the spider mite family (Tetranychidae) of several major crops (Duarte et al., 2009;Humber et al., 1981;Klubertanz et al., 1991;Nordengen and Klingen, 2006;Klingen et al., 2008;Boykin et al., 1984;Carner and Canerday, 1970;Smitley et al., 1986;Dick and Buschman, 1995;Mietkiewski et al., 1993Mietkiewski et al., , 2000. ...
A controlled climatic chamber microcosm experiment was conducted to examine how light affects the hourly sporulation pattern of the beneficial mite pathogenic fungus Neozygites floridana during a 24 h cyclus over a period of eight consecutive days. This was done by inoculating two-spotted spider mites (Tetranychus urticae) with N. floridana and placing them on strawberry plants for death and sporulation. Spore (primary conidia) discharge was observed by using a spore trap. Two light regimes were tested: Plant growth light of 150 μmol m(-2) s(-1) for 12 h supplied by high pressure sodium lamps (HPS), followed by either; i) 4 h of 50 μmol m(-2) s(-1) light with similar HPS lamps followed by 8 h darkness (full HPS light +reduced HPS light +darkness) or ii) 4 h of 50 μmol m(-2) s(-1) red light followed by 8 h darkness (full HPS light +red light +darkness). A clear difference in hourly primary conidia discharge pattern between the two different light treatments was seen and a significant interaction effect between light treatment and hour in day during the 24 h cycle was observed. The primary conidia discharge peak for treatment ii) that included red light was mainly reached within the red light hours (19:00-23:00) and the dark hours (23:00-07:00). The primary conidia discharge peak for treatment i) with HPS light only was mainly reached within the dark hours (23:00-07:00).
... Fungi of the family Entomophthoraceae (Order Entomophthorales) cause epizootic diseases that often devastate arthropod populations (van der Geest et al., 2000). Fungi of Neozygites sp., Hirsutella sp., Lecanicillium sp. and unidentified fungi were reported infecting phytoseiid mites and the infection may be promoted under high relative humidity (Furtado et al., 1996;Keller, 1997;Schütte et al., 2005;Bałazy et al., 2008). The entomopathogenic fungi used against pest mites may also exert stress on phytoseiid mites. ...
Predatory mites of the family Phytoseiidae are important natural enemies of phytophagous mites and small insects. Phytoseiid mites often experience a variety of stresses brought about by changing or fluctuating environmental factors in the field or laboratory or during their commercial production. These factors include abiotic stressors such as extreme temperature and humidity, ultraviolet radiation, and pesticides, and biotic stressors such as cannibalism, intraguild predation, food shortage, and pathogens, all of which affect the biocontrol potential of phytoseiid mites. The extent to which an environmental stressor may affect the biocontrol efficacy of phytoseiid mites depends on the characteristics of the species and on other concurrent stresses. In this review, we discuss the effects of environmental stressors on various biological and ecological aspects of phytoseiid mites, such as development, survival, reproduction, and predation, and the mites’ adaptation strategies to these stressors.
... The only other Neozygites species known to affect the genus Cinara is Neozygites cinarae (Keller 1997), whose hyphal bodies are 20.5-22 μm in diameter and 4-nucleate; primary conidia are 24-31 × 18.5-21 μm, and the secondary capilliconidia are short almond-shaped, and 32-34.5 × 13.5-17 μm. ...
The genus Neozygites has been known in Brazil until now only on mites, and this is its first report on aphids in Brazil. Tree-dwelling aphids (Cinara sp.) on a cypress tree were regularly monitored for entomopathogenic fungi in the city of Terezópolis de Goiás in Central Brazil between July 2014 and April 2015. During the survey, mycosed aphids were found attached to twigs. The fungus was identified morphologically as Neozygites osornensis. No in vitro cultures were established from infected aphids. The finding reported here suggests that special attention should be paid in the future for the possible occurrences of Neozygites species wherever cinaran aphids occur around the globe.
... Pathogenic fungi play a major role in the natural regulation of spider mite populations. Species of the genus Neozygites Witlaczil have been observed to infect spider mites on various crops (Keller 1997 ;Smitley et al. 2011 ). Weiser and Muma ( 1966 ) described one of the most common species of this genus, Neozygites fl oridana , as a pathogen of the Texas citrus mite, Eutetranychus banksi McGregor, on citrus in Lake Alfred, Florida. ...
An overview of infectious microorganisms associated with pest mites is presented. Many mites are major impediments to the production of food crops either in open fields or under protected environments such as greenhouses and plastic tunnels. Reliance on chemical acaricides for management of these mites is of serious concern due to the development of resistance in mite populations, environmental disturbance and effect on human health. Several pathogens play an important role in the regulation of pest mite populations through natural epizootics. The majority of these are fungi, but other pathogens include viruses, bacteria, protozoa, and nematodes. Several successful examples of pathogens that have been produced in vitro for the control of pest mites are presented. Interaction of the pathogens with beneficial arthropods such as predatory mites is also important for implementing biological control. Prospects for the application of acaropathogens in the management of mites in various agricultural systems are discussed.
... Pathogenic fungi play a major role in the natural regulation of spider mite populations. Species of the genus Neozygites Witlaczil have been observed to infect spider mites on various crops (Keller 1997 ;Smitley et al. 2011 ). Weiser and Muma ( 1966 ) described one of the most common species of this genus, Neozygites fl oridana , as a pathogen of the Texas citrus mite, Eutetranychus banksi McGregor, on citrus in Lake Alfred, Florida. ...
The Mesostigmata is a large mite order corresponding to about 20 % of all known mite species. These are found in different habitats, but are most abundant and diverse in the soil. Several mesostigmatid groups have been little studied, especially for not being abundant or for being difficult to handle, especially those living in the soil. Knowledge about the diversity of soil mites is still very small in most of the world. Considering just the number of described mesostigmatid species (let aside the number of undescribed species), the number of biological and ecological studies is very limited. Available studies most often are restricted to the evaluation of the ability of particular species to feed on pre-determined food sources. A few have received some attention, among which two superfamilies of the infraorder Gamasina, Rhodacaroidea (in the hyporder Dermanyssiae) and Parasitoidea (in the hyporder Parasitiae). This chapter comprises the biological and ecological information regarding the Mesostigmata.
... T. urticae is a well-118 studied species due to its worldwide status as a serious pest of 119 many crops (Greco et al., 2005) and suitability as a model species 120 (Oku, 2014). N. floridana is an obligate pathogen of spider mites 121 (Keller, 1997), developing inside its host as hyphal bodies. After 122 killing the host, which is then called a cadaver, the fungus pene- (Crooker, 1985). ...
Exploring prospective mates can be risky. Males of the spider mite Tetranychus urticae approach and guard immobile (quiescent) female nymphs to increase their chances of fathering offspring, this being a first-male sperm priority species. We investigated the behaviour of male T. urticae towards females killed by the mite pathogenic fungus Neozygites floridana, letting them choose between a fungal killed and a healthy quiescent female. The dead female (called cadaver) was in one of three stages: (1) non-sporulating; (2) sporulating with primary conidia (non-infective); (3) surrounded/partly covered by secondary capilliconidia (infective). When the cadaver was in stage 1 or 2, males were significantly more often observed near the cadaver than near the healthy female. When the cadaver was in stage 3 (infective capilliconidia), males preferred the vicinity of healthy females. The frequency of two male behaviours, touching and guarding, was also recorded. Touching the cadaver tended to decrease as cadaver developed, whereas touching the healthy females increased. Guarding of non-sporulating cadavers and healthy females was equally common, while guarding of sporulating cadavers was only observed once (stage 2) or not at all (stage 3). To differentiate between the effect of fungal infection and sex, we also let males choose between a non-sporulating cadaver of each sex. Males then preferred to approach the female cadaver. Touching behaviour followed the same pattern, and guarding of male cadavers was not observed. Our results indicate that T. urticae males are more attracted to non-infective female cadavers than to healthy females, only detecting their mistake when very close. Moreover, males approach and explore cadavers surrounded by infective conidia. Whether the results of host manipulation by the pathogen or just sensory constraints in the host, this inability to detect unsuitable and indeed infective mates promotes transmission of the pathogen.
... Neozygites floridana has been reported infecting many tetranychid mites including the twospotted spider mite, Tetranychus urticae Koch, the Texas citrus mite, Eutetranychus banksi (McGregor) (Acari: Tetranychidae) (Keller, 1997), but the host range and other characters of isolates from different hosts have rarely been investigated. Recently, Neozygites isolates from CGM in Brazil and Benin, has been named, N. tanajoae (Delalibera et al., in press) separated from N. floridana. ...
The cassava green mite (CGM), Mononychellus tanajoa, a native of South America was accidentally introduced into Africa where it causes serious crop losses. The possibility of introducing classical biological agents from the native home of CGM into Africa was investigated. Thus, we conducted a series of laboratory assays of the native fungal pathogens, Neozygites tanajoae from Brazil and Neozygites floridana from Colombia and Brazil, and compared them with N. tanajoae isolates from Benin. Infectivity of both fungal species, was assayed against the twospotted spider mite, Tetranychus urticae, and against the red mite, Oligonychus gossypii. Pathogenicity against CGM and host range studies were conducted by transferring adult females of each mite species to leaf discs containing sporulated cadavers with a halo of conidia of each fungal isolate. All isolates caused some degree of infectivity to CGM. None of the isolates of N. floridana and N. tanajoae tested were pathogenic to O. gossypii, and only two isolates infected T. urticae. Most isolates from Brazil were highly virulent and infected only CGM. Sixteen N. tanajoae isolates caused more than 89% mortality and more than 62% of the CGM became mummified. A mummified CGM is characteristically a swollen, brown fungus-killed mite that has great potential to produce conidia. However, high mortality was not always associated with high mummification. The median mummification time ranged from 4.4 to 6.7 days. Five Brazilian isolates caused >75% mummification with a median mummification time <5 days. Isolates that cause high mummification in a short period of time would be more likely to cause epizootics and to establish in the new environment. Therefore, these isolates would be the best candidates for introduction to Africa.
... Neozygites floridana has been reported infecting many tetranychid mites including the twospotted spider mite, Tetranychus urticae Koch, the Texas citrus mite, Eutetranychus banksi (McGregor) (Acari: Tetranychidae) (Keller, 1997), but the host range and other characters of isolates from different hosts have rarely been investigated. Recently, Neozygites isolates from CGM in Brazil and Benin, has been named, N. tanajoae (Delalibera et al., in press) separated from N. floridana. ...
The cassava green mite (CGM), Mononychellus tanajoa, a native of South America was accidentally introduced into Africa where it causes serious crop losses. The possibility of introducing classical biological agents from the native home of CGM into Africa was investigated. Thus, we conducted a series of laboratory assays of the native fungal pathogens, Neozygites tanajoae from Brazil and Neozygites floridana from Colombia and Brazil, and compared them with N. tanajoae isolates from Benin. Infectivity of both fungal species, was assayed against the twospotted spider mite, Tetranychus urticae, and against the red mite, Oligonychus gossypii. Pathogenicity against CGM and host range studies were conducted by transferring adult females of each mite species to leaf discs containing sporulated cadavers with a halo of conidia of each fungal isolate. All isolates caused some degree of infectivity to CGM. None of the isolates of N. floridana and N. tanajoae tested were pathogenic to O. gossypii, and only two isolates infected T. urticae. Most isolates from Brazil were highly virulent and infected only CGM. Sixteen N. tanajoae isolates caused more than 89% mortality and more than 62% of the CGM became mummified. A mummified CGM is characteristically a swollen, brown fungus-killed mite that has great potential to produce conidia. However, high mortality was not always associated with high mummification. The median mummification time ranged from 4.4 to 6.7 days. Five Brazilian isolates caused >75% mummification with a median mummification time <5 days. Isolates that cause high mummification in a short period of time would be more likely to cause epizootics and to establish in the new environment. Therefore, these isolates would be the best candidates for introduction to Africa.
... Numerosas publicaciones registran la presencia de hongos Entomophthorales infectando insectos plaga de la agricultura en Europa (Balazy, 1993;Santamaria & Girbal, 1996;Nielsen et al., 2001), en Asia (Humber, 1992;Keller, 1997), en África (Hatting et al., 1999), en Estados Unidos (Feng et al., 1990;Steinkraus & Boys, 2005) y en América del Sur (Aruta et al, 1974;Aruta et al. 1984;Alzugaray et al. 1999;ISSN 0373-580 X Bol. Soc. ...
Review of Entomophthorales (Zygomycota: Zygomycetes) fungal pathogens of insects from Argentina. Entomophthoralean fungi are entomopathogens that cause death of their insect hosts, they usually are very specific and however some of them are able to be in vitro cultivated, some species are hardly possible or not able to be isolated in axenic cultures. The Entomophthorales (Zygomycota: Zygomycetes) are the most predominant insect pathogenic fungi which are poorly known in South America and they are scarce reported in Argentina. The overall purpose of the present paper is to update the knowledge of the reports and research done about this fungal group in our country and to include a checklist of fungal species, distribution and insect hosts to further extent about its biodiversity. Resumen: Los hongos Entomophthorales son entomopatógenos que causan la muerte de los insectos hospedadores, son usualmente muy específicos y aún cuando algunos son posibles de cultivar in vitro, la mayoría son difíciles de aislar en cultivos axénicos. En trabajos previos en la República Argentina se ha dado a conocer la presencia de hongos entomopatógenos. Los Entomophthorales (Zygomycota: Zygomycetes) son los hongos patógenicos de insectos más predominantes poco conocidos en América del Sur y raramente encontrados en la Argentina. El principal objetivo de este trabajo fue realizar una puesta al día y estado de avance del conocimiento sobre este grupo de hongos en nuestro país, incluyendo un listado de especies citadas, su distribución e insectos hospedantes, con el propósito de ampliar el conocimiento de su biodiversidad.
... However, the impact of this fungus on T. evansi populations is unknown. Neozygites floridana (Weiser and Muma, 1966) is an obligate pathogen with a restricted host range, pathogenic only to species of spider mites (Keller, 1997). Mites infected with this fungus only die at late stage of infection as opposed to other entomopathogenic fungi (Deuteromycetes) which produce toxins that cause host death before the fungus completes colonization of the host. ...
The tomato red spider mite, Tetranychus evansi (Acari: Tetranychidae) was recently introduced in Africa and Europe, where there is an increasing interest in using natural enemies to control this pest on solanaceous crops. Two promising candidates for the control of T. evansi were identified in South America, the fungal pathogen, Neozygites floridana and the predatory mite Phytoseiulus longipes. In this study, population dynamics of T. evansi and its natural enemies together with the influence of environmental conditions on these organisms were evaluated during four crop cycles in the field and in a protected environment on nightshade and tomato plants with and without application of chemical pesticides. N. floridana was the only natural enemy found associated with T. evansi in the four crop cycles under protected environment but only in the last crop cycle in the field. In the treatments where the fungus appeared, reduction of mite populations was drastic. N. floridana appeared in tomato plants even when the population density of T. evansi was relatively low (less than 10 mites/3.14cm2 of leaf area) and even at this low population density, the fungus maintained infection rates greater than 50%. The application of pesticides directly affected the fungus by delaying epizootic initiation and contributing to lower infection rates than unsprayed treatments. Rainfalls did not have an apparent impact on mite populations. These results indicate that the pathogenic fungus, N. floridana can play a significant role in the population dynamics of T. evansi, especially under protected environment, and has the potential to control this pest in classical biological control programs.
... In our study, we never documented E. chromaphidis before late in the season (7Ð14 September 2004), and in all Þelds surveyed throughout the season in 2004, P. neoaphidis was always the Þrst aphid pathogenic fungus found. N. fresenii has for some time been regarded as a species especially adapted to hot, humid, and even tropical conditions (Keller 1997, Steinkraus 1998) but recently was also found causing epizootics in the subarctic (Nielsen et al. 2001b). In this study, this fungal species was documented more frequently toward autumn than during midsummer. ...
This study evaluated the diversity and abundance of existing natural enemies of soybean aphid, Aphis glycines L., under field conditions in New York State, with emphasis on entomopathogenic fungi. In 2003, five soybean fields were occasionally sampled to estimate abundance and species composition of entomopathogenic fungi. During 2004, five soybean fields and adjacent buckthorn were sampled weekly. Seven species of aphid pathogenic fungi were found, including Pandora neoaphidis (Remaud. et Henn.) Humber, Conidiobolus thromboides Drechsler, Entomophthora chromaphidis Burger et Swain, Pandora sp., Zoophthora occidentalis (Thaxter) Batko, Neozygites fresenii (Now.) Remaud. et Keller, and Lecanicillium lecanii, (Zimm.) Gams et Zare. P. neoaphidis was the most abundant species, causing 84% infection in an outbreak aphid population in 2003, after which the aphid population crashed. In 2004, we found the first aphids with fungal infections in late June to midJuly. Mycosis was strongly associated with aphid density, especially during increasing aphid populations. In agreement, epizootic levels of infection were associated with subsequent declines in aphid populations. There was variability among fields; in three of five fields sampled in 2004, the chances for infection were more than five times higher than in the other two fields. High infection levels were found on aphids on buckthorn over 3 wk in autumn. Three species of aphidiid parasitoids from A. glycines were documented: Aphidius sp. and two Praon species. Both genera were the first records from A. glycines in the United States. Coccinellids were the most abundant predator, followed by syrphids and cecidomyiids, whereas anthocorids and chrysopids were less common.
Genera Batkoa, Entomophaga, Entomophthora, Pandora, and Zoophthora (family Entomophthoracaeae), Conidiobolus (family Ancylistaceae), and Neozygites (family Neozygitaceae) are agriculturally important entomophthoroid genera. Unlike some hypocrealean fungi that can be mass produced and formulated as biopesticides, entomophthoroid fungi do not have the biopesticide potential due to their fastidious nature, but they are important mortality factors in many agricultural systems, causing significant pest population reductions through natural epizootics. Taxonomic aspects of key entomophthoroid genera, techniques for their isolation and propagation, their microbial control potential through natural epizootics or artificial introductions with several examples, and factors influencing entomophthoroid fungal epizootics are discussed.
The fungus Neozygites floridana is a pathogen commonly associated with the cassava green mite (CGM), Mononychellus tanajoa, and the two-spotted spider mite (TSM), Tetranychus urticae, in South America. Difficulty in culturing N. floridana in vitro has hampered its development as a bioacaricide. A Colombian isolate from TSM was multiplied in TSM and hyphal bodies from infected specimens were inoculated into 18 mycological and tissue culture media. Grace's insect tissue culture medium plus 0.33% lactalbumin hydrolysate and 0.33% yeastolate (GS) afforded vigorous multiplication of hyphal bodies (over 10⁶ /mL). The number of hyphal bodies increased with aeration. Final concentration of hyphal bodies was not affected by fetal bovine serum (FBS), but growth was somewhat enhanced. Hyphal bodies produced germ tubes when transferred from GS medium to Grace's medium plus 10% FBS and shaken at 200 rpm for 24 h. The germinated hyphal bodies, when placed on water agar, produced primary conidia from which capilliconidia were produced. These capilliconidia were infective to both TSM and CGM.
Resting spores of Neozygites parvispora, an obligate pathogen of thrips, were found in washes from seed of cultivated annual ryegrass (Lolium multiflorum) from Oregon. Similar spores were found in washes from seed samples of annual ryegrass from Tennessee, wheat from Arizona and wild tall fescue (Festuca arundinacea) from New Zealand. In the Oregon specimens, the resting spores were formed inside the bodies of thrips (Limothrips sp.) wedged between the palea and seed in ryegrass. The resting spores germinated directly to produce a germ conidium on a short conidiophore. This is the first report of resting spore germination in N. parvispora, and the first report of the species outside of Europe.
The Zygomycota is an ecologically heterogenous assemblage of nonzoosporic fungi comprising two classes, Zygomycetes and Trichomycetes. Phylogenetic analyses have suggested that the phylum is polyphyletic; two of four orders of Trichomycetes are related to the Mesomycetozoa (protists) that diverged near the fungal/animal split. Current circumscription of the Zygomycota includes only orders with representatives that produce zygospores. We present a molecular-based phylogeny including recognized representatives of the Zygomycetes and Trichomycetes with a combined dataset for nuclear rRNA 18S (SSU), 5.8S and 28S (LSU) genes. Tree reconstruction by Bayesian analyses suggests the Zygomycota is paraphyletic. Although 12 clades were identified only some of these correspond to the nine orders of Zygomycota currently recognized. A large superordinal clade, comprising the Dimargaritales, Harpellales, Kickxellales and Zoopagales, grouping together many symbiotic fungi, also is identified in part by a unique septal structure. Although Harpellales and Kickxellales are not monophyletic, these lineages are distinct from the Mucorales, Endogonales and Mortierellales, which appear more closely related to the Ascomycota + Basidiomycota + Glomeromycota. The final major group, the insect-associated Entomophthorales, appears to be polyphyletic. In the present analyses Basidiobolus and Neozygites group within Zygomycota but not with the Entomophthorales. Clades are discussed with special reference to traditional classifications, mapping morphological characters and ecology, where possible, as a snapshot of our current phylogenetic perspective of the Zygomycota.
The fungal pathogen Neozygites tanajoae Delalibera Jr., Humber & Hajek sp. nov. (Zygomycetes: Entomophthorales) is being used in Africa as a biological control agent against the introduced cassava green mite (CGM), Mononychellus tanajoa (Bondar) (Acari: Tetranychidae). This fungus is specific to CGM and has been referred to as N. floridana (Weiser & Muma) Remaud. & Keller, a common pathogen of many tetranychid mites. In the present study N. tanajoae is investigated at the morphological and molecular levels and physiological attributes of N. tanajoae and N. floridana are compared. Morphological observations of N. tanajoae isolates generally correspond to N. floridana and to other mite pathogenic species of Neozygites. However, this fungus readily can be distinguished from N. floridana based on 18S rDNA sequences, host ranges, nutritional requirements for growth in vitro, tolerances to cold (4 C) and abilities to withstand specific cryopreservation techniques. N. tanajoae isolates from Brazil and Africa have identical 18S rDNA sequences but they presented 5.7 and 9.94% pairwise distance from N. floridana isolates. N. tanajoae proved to differ sufficiently from other mite-pathogenic fungi referred to as N. floridana to justify the description of a new species.
Adverse effects of chemical pesticides on nontarget organisms, food safety, and development of insect resistance have forced the scientific communities to focus on the development of alternative eco-friendly measures. The biological plant protection with entomopathogenic fungi has a key role in a sustainable pest management program. The entomopathogens are generally ubiquitous and belong mostly to the phyla Chytridiomycota, Zygomycota, Oomycota, Ascomycota, and Deuteromycota. In order to manipulate the environment to enhance the population of entomopathogens, knowledge about the fundamental aspects of ecology of mycopesticides is necessary. Most of the insect-infecting fungi have a contact mode of action. The adaptive response in entomopathogens includes formation of infective structures, extracellular enzymes (protease and lipase), production of toxins, etc., which ultimately kill the insects. On the other hand, insects have evolved a number of mechanisms to keep the pathogen at bay. At present improved fungal mass production and formulations are commercially available. Modern techniques in genetic engineering and biotechnology are extremely helpful in manipulating the desired traits of entomopathogenic fungi, which can further improve its bioactivity. This review updates about the recent progress in the field of myco-biocontrol of insect pests.
Background
The beneficial fungus Neozygites floridana kills the two-spotted spider mite Tetranychus urticae, which is a serious polyphagous plant pest worldwide. Outbreaks of spider mites in strawberry and soybean have been associated with pesticide applications. Pesticides may affect N. floridana, and, consequently, the natural control of T. urticae. N. floridana is a fungus difficult to grow in artificial media; for these reasons, very few studies have been conducted with this fungus, especially regarding the impact of pesticides. The aim of this study was to conduct a laboratory experiment to evaluate the effect of pesticides used in strawberry and soybean crops on N. floridana.
Results
Among the pesticides used in strawberry, the fungicides sulfur and cyprodinil + fludioxonil completely inhibited both the sporulation and conidia germination of N. floridana. The fungicide fluazinam affected N. floridana drastically. The application of the fungicide tebuconazole and the insecticides fenpropathrin and abamectin resulted in a less pronounced negative effect on N. floridana. Except for epoxiconazole and cyproconazole, all tested fungicides used in soybean resulted in a complete inhibition of N. floridana. Among the three insecticides used in soybean, lambda-cyhalothrin and deltamethrin resulted in a significant inhibition of N. floridana.
Conclusion
The insecticides abamectin / lambda-cyhalothrin at half concentrations and fenpropathrin / permethrin and the fungicide tebuconazole at the recommended concentrations resulted in the lowest impact on N. floridana. The sulfur fungicides, cyprodinil + fludioxonil, azoxystrobin, azoxystrobin + cyproconazole, trifloxystrobin + tebuconazole and pyraclostrobin + epoxiconazole negatively affected N. floridana.
The Zygomycota may be one of the most diverse and the least-studied of the fungal phyla, and as presently classified, appears to be polyphyletic. Zygomycota is one of the four divisions of the Fungi accepted by Barr (1992), and consists of Trichomycetes and Zygomycetes. Zygomycetes are saprobes or haustorial or nonhaustorial parasites of animals, plants, or fungi. Trichomycetes are symbionts in the gut, or less commonly around the anal region, of arthopods, including insects and their larvae; they attach to the host via a cellular or noncellular holdfast (Lichtwardt 1986). Because of their unique characteristics Trichomycetes will be discussed in the following chapter (Benny, Chap. 7, this Vol.).
Scale insects (Hemiptera: Coccoidea) compose a group of important plant pests of agricultural crops, forest plants, ornamental plants and fruit trees. The history of the study of entomopathogenic fungi as a biological insecticide is reviewed according to the three developmental stages: the pioneering stage, the slow development stage, and the prosperity stage. Additionally, the status of this field in China was discussed. A list including approximately 140 species within 55 genera of the recorded fungal pathogens of scale insects in the world was provided. Finally, we provide four suggestions for the development of entomopathogenic fungi in the future.
In Slovakia colonies of various aphid species were investigated in order to determine a spectrum of entomophthoralean fungi parasiting aphids. 70 different localities were visited throughout the country during 1999-2002. The survey was focused on aphid fauna of agricultural crops and non-production sites. Altogether 14 different entomophthoralean species out of three families were identified from aphids; £rynia neoaphidis, Erynia nouryi, Erynia erinacea, Entomophthora plallchoniana, ZoophtllOra aphidis, Zoophthora radicans, Zoophthora phalloides, Zoophthora occidentalis (Entomophthoraceae); Neozygites jresenii, Neozygites microiophii, Neozygites cinarae, Neozygites turbinata (Neozygitaceae); Conidiobolus obscurns, Conidiobolus thromboides (Ancylista-ceac). The fungal species were recorded from 69 aphid species belonging to three families (Aphididae, Drcpanosiphidae and Anpecidae). Out of the 14 fungal species 10 are the first record from Slovakia. E. neoaphidis was a dominant fungal species and caused. epizootics in aphid colonies. E. planchoniana was the second most frequent pathogen but no epizootics were recorded. Conversely, N. jresenii had a strong tendency to establish epizootics in dense aphid colonies, especially in those of Aphis labae. Species E. nOllryi, E. erinacea, Z. phalloides, Z. occidenlalis, C. thromboides were identified from single aphid species despite they are known to have a broader host spectrum. N. microiophii and N. cinarae are probably monophagous species.
The objective of this work was to verify the occurrence of predatory mites and the fungus Neozygites floridana, associated with spider mites in soybean (Glycine max L.), in Rio Grande do Sul, Brazil. From 2003 to 2005, samples of soybean leaves from the most important soybean producing regions of the state were evaluated. These samples were collected from different positions of the plant and randomly in the field. The predatory mite species found were Neoseiulus anonymus, N. californicus, Phytoseiulus fragariae, P. macropilis, Proprioseiopsis cannaensis, and Galendromus annectens. The fungus N. floridana was widely distributed and occurred in all the spider mite species found: Mononychellus planki, Tetranychus desertorum, T. gigas, T. ludeni and T. urticae.
Neozygites osornensis is a recently described aphid pathogen characterized by morphological criteria and compared with two morphologically close taxa, Neozygites cinarae and Neozygites turbinata. Neozygites species are traditionally classified based on morphological characteristics and molecular data that would confirm these taxa and permit investigation of their phylogenetic relationships are scarce. In this study, we successfully evaluated a genetic variation within partial 18S rDNA sequences among the three Neozygites species and supported the recent erection of N. osornensis as a new species. A phylogenic analysis was also included to support our results.
Neozygites parvispora was isolated from Tbrips tabaci infesting leek plants. In vitro cultivation of two isolates was achieved using supplemented Grace's insect tissue culture medium complemented with fetal bovine serum (FBS) and pre-treated lepidopteran hemolymph. This medium composition enabled exponential cell growth as rod-shaped hyphal bodies with a length over diameter ratio of 4.5-5.0. Both FBS and hemolymph were mandatory for sustained growth. The growth requirements indicate the presence of one or several growth factors in both the hemolymph and FBS. Absence of FBS resulted in growth arrest with subsequent cell lysis. Omission of hemolymph led to rounding and size decrease of the hyphal bodies, some of which formed septated germ tubes in a later stage. Eventually, cell death occurred under such conditions. Hyphal bodies from in vitro culture were capable of capilliconidia formation after entrapment in alginate pellets. This suggests the requirement of a liquid/air interface, which triggers primary sporulation and subsequent capilliconidium formation.
Halotydeus destructor (Tucker) (Acari: Penthaleidae) is a major pest of pastures, crops and vegetables, in regions of Australia, South Africa and New Zealand, with cool wet winters and hot dry summers. The taxonomy, distribution, biology, ecology and control of H. destructor are reviewed. Halotydeus destructoris essentially a soil mite, spending 90% of its time on or near the soil surface and moving up onto plants only to feed. After penetrating the epidermis, the cell contents are sucked up. Other mites are attracted to volatiles released from the leaves damaged by feeding mites and they usually feed in aggregations. Although they feed on a wide range of plant species, their reproductive success varies considerably on different plant species. Mites are more abundant and more eggs are laid on an annual pasture at a site with high rainfall than one with lower rainfall. The rate of oviposition is probably resource limited. When pasture is grazed short, the mites are less abundant, but the same number of eggs are laid. Halotydeus destructorrequires a high relative humidity and the active mite mortality is probably greater at low relative humidities in short pasture. Halotydeus destructor completes three generations a year. The summer is passed as a diapausing egg in the cadaver of an adult female mite on the soil surface. Long-distance passive dispersal probably occurs when these female cadavers are blown by the wind. Plant varieties with resistance to H. destructor are being developed in subclovers (subterranean clover, Trifolium subterraneum L.), medics (Medicago spp.) and canola (Brassica napus), to reduce the considerable economic losses caused by the mites. Mechanisms of resistance have been identified in subclover seedlings. It appears to be more beneficial to control H. destructor in spring than in autumn, particularly in a pasture before a crop. The future management of this pest will require the integration of plant resistance with other control methods.
The objective of this study was to characterize epizootics of Neozygites sp. by investigating the relationship between the pathogen, the host, Mononychellus tanajoa (Bondar) (Cassava green mite = CGM), and climatic factors. Epizootics were studied from March through October 1994 in nine cassava fields at Piritiba, state of Bahia, Brazil. In all fields the pathogen appeared when CGM density was moderate to high. Infected CGM were first detected in northwestern fields, with an apparent progression to the southeast. The onset of the epizootic in the earliest field was observed 23 days prior to the onset of the epizootic in the latest field. During the epizootic phase of most fields (late May to late June), daily mean RH ranged from 70% to 79% and daily mean temperature ranged between 21.1°C and 24.3°C. Disease progression within CGM populations was documented in two of the nine fields. In the field where the slower spread of the pathogen was observed, the proportion of area with infected CGM increased from 14% to 100% in 14 days. Neozygites sp. was detected in higher proportions in plots with the highest levels of CGM and in greater abundance on mites collected from apical leaves as compared with median leaves. Resting spores of Neozygites sp. were recovered during June and July, but during the remaining period, infected mites contained only hyphal bodies.
An entomophthoralean fungus causing epizootics in populations of the cypress aphid, Cinara cupressi Buckton, in Chile is described as a new species, Neozygites osornensis Montalva et Barta. The aphid pathogen is described based on morphological characters. An exhaustive description, illustrations and a comparison with closely related species are provided. The fungus differs from similar Neozygites species by smaller hyphal bodies, nuclei, primary conidia, capilliconidia and capilliphores and by noticeably different shape of capilliconidia. A key to aphid-pathogenic species of Neozygites is also included.
Uniquement connue au Sud des Etats-Unis d'Amérique, l'Entomophthorale #Neozygites fumosa$ (Speare) Remaudière et Keller a été retrouvée en République Populaire du Congo, où elle attaque la cochenille du manioc, #Phenacoccus manihoti$ Matile-Ferrero (Hom. : #Coccoidea Pseudococcidae$). De légères variations d'ordre biométrique sont mises en évidence au sein de l'espèce fongique. A ce jour, parmi les Entomophthorales mentionnées dans la littérature comme pathogènes de cochenilles, seules deux espèces peuvent être retenues avec certitude : #Neozygites fumosa$ et #Conidiobolus pseudococci$ Speare (Tyrrell and MacLeod), toutes deux pathogènes de #Pseudococcidae$. (Résumé d'auteur)
This paper gives results obtained in the Congo in 1987 on previously unstudied aspects of the epizootiology ofNeozygites fumosa (Speare) Remaudière et Keller (Entomophthorales), a pathogen of the cassava mealybug,Phenacoccus manihoti Matile-Ferrero (Hom.: Pseudococcidae).
The disease spreads very rapidly, in 2 distinct phases: an initial, implantation, phase, strongly correlated with the size and structure of the host colonies and a 2nd phase (the epizootic phase in the strict sense), which is independant of these factors. The development of the epizootic appears to be more closely related to the frequency of rainfall than with total rainfall. Conditions are highly favourable when the air humidity is greater than 90% for at least 5 hours per day, consistently. The significance of the time during which the canopy remains wet is demonstrated for the first time. The density of conidia in the air is positively correlated with the level of infection in theP. manihoti population.
Neozygites sminthuri is described as a new species. The spherical hyphal bodies measure 12.1-14.6 μm and contain 4, rarely 3 nuclei. The conidiophores are unbranched and produce a single conidium. The primary conidia measure 13.2-14.5 × 8.2-10.0 μm. Secondary conidia resembling the primary ones are produced on short, thick secondary conidiophores. Capilliconidia and resting spores were not found, but the fungal structures observed allow the inclusion of this species in the genus Neozygites.
An entomophthoraceous fungus, Entomophthora floridana, attacked the Sugi spider mite, Oligonychus hondoensis, in a plantation of Japanese cedar, Cryptomeria japonica, in the Kyushu District of Japan. The fungus infected mainly the adult mite. It formed primary conidia and two types of secondary conidia. The mites were infected by one of the secondary types of conidia (anadhesive spores). Only resting spores occurred in the dead mummified mites during winter. © 1975, JAPANESE SOCIETY OF APPLIED ENTOMOLOGY AND ZOOLOGY. All rights reserved.
Recently, Selhime and Muma (1966) studied the biology of an entomophthoraceous fungus attacking the Texas citrus mite, Eutetranychus banksi (McGregor). This study and a series of earlier publications including Fisher (1954), Muma (1955 and 1958) and Muma et al. (1961) have indicated the unusual frequency of the fungus in the field and its potential importance in the biological control of the Texas Citrus mite. This fungus, described in the present paper, is not the only Entomophthora known to infect Acarina. Petch (1940) described Entomophthorct acaricida from Halotydems destructor Tucker and later, Petch (1944) described E. acaridis from other infected Acarina. Recently, Batko (1965) recorded Conidiobolus brefeldianus Couch from Tyrophagus perniciosus Zachvatkin and other tyroglyphid mites. METHODS
A fungal pathogen from the Entomophthorales (Zygomycetes) was discovered in populations of the lucerne fleaSminthurus viridis(Collembola) collected from grassland and leguminous crops in Denmark during July to October. The morphology of the fungus was studied in springtails, collected live, which succumbed to fungal disease following incubation in the laboratory. Based on these preliminary morphological studies the fungus appears to be an undescribed species ofNeozygites.Field studies showed the fungus to be enzootic with a widespread geographical distribution in Denmark. At one location fungus prevalence inS. viridisreached a maximum of approximately 12% infected individuals. No fungus-killed cadavers were observed in the field. This is the first well-documented report of an entomophthoralean fungus infecting an apterygote insect. A single individual was infected by the entomophthoralean fungusConidiobolus coronatus. Verticillium lecaniiandBeauveria bassiana(Deuteromycotina:Hyphomycetes) were also isolated fromS. viridis.
Empusa acaridis is redescribed from the mite, Macrocheles peregrinus. Infected mites presented a striking appearance, with white fungal outgrowth appearing as a band between the dorsal and ventral shields mainly on the posterior end of the body. The paucinucleate, unitunicate conidia measured 19.8 x 15.4 μm and were formed on simple conidiophores. The verrucose resting spores were darkly pigmented, measuring 16.7μm diam, and appear to form by budding from two spherical hyphal bodies. The taxonomic position of the fungus is discussed and the new combination Neozygites acaridis (Petch) Milner is proposed.
The fungus Triplosporium floridanum is common in various regions of Israel, attacking green and red forms of the two-spotted spider mite, Tetranychus telarius sensu lato. No resting spores have been found in this species in Israel.With dried, mummified, infected mites from the field, kept in vials for 6 weeks at 4°C, sporulation of associated T. floridanum was effected in moist chambers; after the dried mummies had been held for another 9.5 months at room temperature, the number of mites showing sporulating fungi in moist chambers remained very high. The fungus sporulated within an extremely wide temperature range, 4–37°C. Primary conidia were produced in less than a day at 6, 18, 27, 30, and 37°C, and anadhesive spores at 18, 27, and 30°C. After 2 days, anadhesive spores formed at 6°C as well. Heaviest sporulation occurred at 27† and 30°C. The longevity of the normal-appearing hyphal bodies within the mites after prolonged desiccation is considered to be a possible mechanism for tiding the fungus over periods during which the host is rare in the field.
Entomophthora sp. killed its host, Tetranychus urticae, in 3.38 days at 25°C and in 11.02 days at 15°C. Development of hyphal bodies within the mite was studied with a light microscope, and a scanning electron microscope was used to examine spore development and structure. A comparison of this fungus with other mite-infecting fungi revealed that it is more closely related to E. floridana than to E. tetranychi, and should be called Entomophthora sp. near floridana until a more detailed study of E. floridana can be made.
Entomophthora aphidis Hoffmann and E. thaxteriana (Petch) Hall & Bell on Acyrthosiphon pisum Harris, and E. fresenii (Nowakowski) Gustafsson and E. planchoniana Cornu on Aphis fabae Scopoli penetrate the cuticle at any point, probably by enzymic and mechanical processes. Only E. fresenii forms an appressorium. Hyphae or hyphal bodies of each fungus first invade the haemocoel where individual blood cells appear to engulf some but do not agglomerate and encapsulate them; each species invades the solid tissues sequentially, with slight differences between fungal species, but all invade sclerotized tissues and embryos last, often after the host dies. Each pseudocystidium of E. aphidis develops from a swollen hyphal body and breaches the aphid cuticle allowing the surrounding conidiophores to emerge. These, and the conidiophores of E. planchoniana and E. thaxteriana, begin to emerge in groups, but eventually those of all species cover the cuticle in an even layer. Weakly differentiated rhizoids sometimes develop around the mouthparts of aphids killed by E. thaxteriana; rhizoids of E. aphidis develop from greatly swollen hyphal bodies, and the compound ones of E. planchoniana develop from bundles of elongated hyphal bodies in the thorax and abdomen of the host; rhizoids of both of these species sometimes emerge before the aphid dies.
Mitosis in a mite-pathogenic species ofNeozygites (Zygomycetes: Entomophthorales) was investigated by indirect immunofluorescence microscopy using an antibody against -tubulin for visualization of microtubules (MTs). DAPI and rhodamine-conjugated phalloidin were used to stain chromatin and actin, respectively. Salient features of mitosis inNeozygites sp. are (1) a strong tendency for mitotic synchrony in any given cell, (2) conical protrusions at the poles of metaphase and anaphase nuclei revealed by actin staining, (3) absence of astral and other cytoplasmic MTs, (4) a spindle that occupies most of the nuclear volume at metaphase, (5) a spindle that remains symmetrical throughout most of mitosis, (6) kinetochore MTs that shorten during anaphase A, (7) a central spindle that elongates during anaphase B, pushing the daughter nuclei into the cell apices, and (8) interpolar MTs that continue to elongate even after separation of the daughter nuclei. Cortical cytoplasmic MTs are present in a few interphasic and post-cytokinetic cells. The data presented show thatNeozygites possesses features unique to this genus and support the erection of theNeozygitaceae as a separate family in theEntomophthorales.
Entomophthora parvispora sp. nov., pathogenic forThrips species, (principallyT. tabaci
Lind.), is described. The fungus is characterized by its very small conidia and resting spores, anadhesive spores with a characteristically-shaped
fixture at their apex, and the mode of resting spore development. The records suggest that the pathogen is widespread and
probably occurs throughout central and southern Europe.
Entomophthora parvispora sp. nov. pathogène pour des espèces deThrips, notammentT. tabaci
Lind., est décrit. Ce champignon est caractérisé par ses conidies et spores durables très petites, par des spores non adhérentes
présentant à leur apex une excroissance de forme caractéristique, ainsi que par le mode de développement des spores durables.
Les observations montrent que cet agent pathogène est largement répandu et se trouve probablement dans toute l'Europe centrale
et méridionale.
La morphologie deNeozygites paravispora, deThrips tabaci Lind. et deN. cf.adjarica deTetranychus urticae Koch est décrite en détail, celle deN. fresenii est limitée à la description des spores de résistance. Les 3 espèces forment en général des spores de résistance brunes à
noires, occasionnellement des spores hyalines qui, cependant, apparaissent non viables. Les conidiophores des capilloconidies
de ces 3 espèces sont caractérisés par un coude, quelques microns avant la terminaison distale. Ce caractère les distingue
des espèces deZoophthora. N. cf.adjarica forme fréquemment des rhizoïdes qui fixent les acariens contenant des spores de résistance à la plante.
The morphology ofN. parvispora fromThrips tabaci Lind. and ofN. cf.adjarica fromTetranychus urticae Koch is described in detail; that ofN. fresenii is limited to a description of the resting spores. In addition to producing typical dark resting spores, the 3 species occasionally
from hyaline ones which, however, appear to be non viable. The conidiophores of the capilliconidia of these species are characterised
by a distinct curvature near the distal end, which distinguishes them from the capilliconiophores ofZoophthora species.N. cf.adjarica frequently formed rhizoids, fixing mites containing resting spores to the leaf surface.
In field plots in which populations of predaceous species were suppressed using carbaryl, populations of the twospotted spider mite, Tetranychus urticae Koch, on field corn declined in association with aerial dispersal of the mites or with epizootics of the entomogenous fungus, Neozygites floridana Weiser & Muma. The relative importance of these two factors varied from year to year depending on environmental conditions. When moist weather conditions induced epizootics of N. floridana before corn plants became heavily infested with mites, the pathogen appeared to be the major factor causing mite population declines. When dry weather conditions allowed mite populations to expand unchecked until corn plants became entirely infested, mite aerial dispersal was the major factor associated with mite population declines. In every field in which there was an epizootic of N. floridana, routine applications of the fungicide maneb delayed epizootics and reduced or delayed the impact of the pathogen on mite populations. The total number of Neozygites-infected mites produced in maneb-treated plots throughout the test period was significantly greater than that in untreated plots when epizootics were initiated during periods of mite population growth. Fewer total infected mites were produced in maneb-treated plots compared to untreated plots when epizootics were initiated during periods of mite population decline.
Influence du champignon entomophage, Neozygites floridana, sur le déclin dans des champs de maïs des populations de l'acarien, Tetranychus urticae
Dans des parcelles de maïs dont les populations d'espèces prédatrices avaient été éliminées par du carbaryl, des populations de T. urticae ont régressé en fonction de la dispersion aérienne des acariens ou d'épizooties provoquées par N. floridana. L'importance relative de ces deux causes varie d'année suivant les conditions écologiques. Le pathogène paraissait la principale cause de déclin des populations quand le temps humide a induit les épizooties par N. floridana avant que le maïs n'ait été largement contaminé par les acariens. Quand le temps sec a permis aux populations d'acariens de se développer sans frein jusqu'à contamination totale du maïs, la dispersion aérienne des acariens était la principale cause de déclin des populations d'acariens. Dans tous les champs où il y avait eu épizootie de N. floridana, des traitements de routine avec le fongicide meneb ont retardé les épizooties et réduit ou retardé l'impact du pathogène sur les populations d'acariens. Pendant toute la période d'étude, le nombre total d'acariens infestés par Neozygites était significativement plus élevé dans les parcelles traitées au maneb que dans les parcelles non traitées, lorsque les épizooties étaient provoquées pendant la période de croissance des populations d'acariens. Quand les épizooties ont été déclenchées pendant la période de déclin des populations d'acariens, un nombre plus faible d'acariens infestés était observé dans les parcelles traitées au maneb que dans les parcelles sans traitement.
The role of entomophthorosis in the dynamics of aphid populations infesting natural vegetation in northern littoral France (Basse-Normandie) and in northeastern continental France (Vosges) is compared. In Basse-Normandie, anholocyclic behavior of numerous aphid species contributes to the permanent presence of aphid populations and consequently, the persistence of mycosis.
In the Vosges, severe winter, conditions result in holocyclic development whereby aphid colonies are present for only 6 to 7 months; during 1974 diseased specimens appeared when aphid populations were maximum, subsequent epizootic development caused a rapid decline of populations.
In the 2 regions,Erynia neoaphidis
Remaud. & Henn.,Entomophthora planchoniana
Cornu,Neozygites fresenii
(Nowak). Remaud. & Kell. andConidiobolus obscurus
(Hall & Dunn) Remaud. & Kell. are most common. The frequent occurrence ofZoophthora phalloides
Batko in littoral Normandy contrasts with an apparent rarity in the Vosges.Conidiobolus osmodes
Drechsler is occasionally encountered in Normandy, but is not found in the Vosges.E. neoaphidis andE. planchoniana are present throughout the year. The former is most abundant in the spring, the latter in the autumn.C. obscurus andZ. phalloides seem better adapted to cooler spring and fall conditions as their occurrence is exceedingly rare during the host summer period. In contrast,N. fresenii is found in the summer whileC. osmodes almost always occurs in the winter.Z. phalloides appears to prefer such asMyzus ascalonicus
Donc. andTubaphis ranunculina
Wlk.;E. planchoniana prefersCavariella spp. Dynamic profiles of the various pathogens of the most common aphids at different times of the year are given; ecological features of each pathogen are described; epizootics only occur in high aphid populations. All species act as good regulating factor and, with the exception ofN. fresenii, persist in very low aphid populations.
Four new species of Entomophthorales attacking the leucaena psyllid, Heteropsylla cubana, in the Philippines are described: Neozygites heteropsyllae, Erynia triangularis, Entomophaga bukidnonensis and Entomophthora philippinensis. Epizootics due mainly to N. heteropsyllae occur commonly in moist areas when populations of the host are dense. The fungi offer potential as agents of control of this important pest.
We have analyzed the behavior of nuclei and actin during the cell cycle of Neozygites sp. with mithramycin and rhodamine-labeled phalloidin. This fungus is an entomophagous zygomycete which grows as a rod-shaped fission yeast containing 2 to 12, mostly 3 to 4, nuclei per cell. The cell cycle is regulated such that there is not a constant nucleus-to-cytoplasmic volume ratio, and mitosis is initiated slightly asynchronously from one end of the cell. During interphase, detected actin occurs exclusively as peripheral plaques, which are most abundant at growing cell tips, and as perinuclear shells. Because the shells disperse and reform concomitantly with the formation and breakdown of a new septum-associated actin array, we infer that they are a novel form of actin storage. Intranuclear mitosis occurs in the absence of detectable spindle actin which suggests that actin is not a universal feature of mitotic systems and may be a cytoplasmic contaminant in open spindles of plant cells. Actin is involved in septum synthesis in previously unreported ways. Prior to morphologically detectable septum initiation, a peripheral equatorial band of longitudinal actin filaments assembles and then shortens to a transverse belt at the future site of septum synthesis. We suggest that this actin array recruits and organizes cell wall synthetic complexes for subsequent septum growth. During detectable septum synthesis, the invaginating plasmalemma bears plaques at a similar concentration to those at growing cellular tips.