Article

Infection of Termites by Spodoptera littoralis Nuclear Polyhedrosis Virus

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Abstract

A nuclear polyhedrosis virus isolated from the Egyptian cotton leafworm, Spodoptera littoralis, was found to infect termite castes of Kalotermes flavicollis. Laboratory studies indicated that no specific trend toward mortality responses among the different individuals of termites was noted. All test castes of termites, young, middle-sized, old and reproductive nymphs, and soldiers, were quite equal in their response to the virus infection, regardless of whether the virus concentration was high or low; a concentration of 6.4 × 108 polyhedra/ml, killed only 64% of the treated individuals, while the dosage of 6.4 × 107 polyhedra/ml produced over 90% mortality. Also, thesame trend of response was recorded with the survivors which received challenge doses of NPV suspension each 9 or 10 days. On the other hand, these results revealed that if the NPV is used to control termites, periodic applications would be more efficacious thanone treatment. Virus symptoms were recorded in all affected insects.

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... Wright et al. (2005) reported that a fungal isolate, C4-B, taxonomically identified as M. anisopliae (Metschnikoff) caused rapid mortality in Formosan subterranean termite alates. A nuclear polyhedrosis virus (NPV) isolated from the cotton leaf worm (Spodoptera litoralis) has also been reported to infect termites (Al Fazairy and Hassan 1988). Termites died 2-10 days post-infection and the authors suggested that control of Kalotermes flavicollis with NPV might be feasible. ...
... Gibbs et al. (1970) isolated a virus infecting Coptotermes lacteus (Froggatt) (Rhinotermitidae), which was similar to acute paralysis virus of the honey bee Apis mellifera Linnaeus (Hymenoptera: Apidae). A nuclear polyhedrosis virus, obtained from caterpillars of Spodoptera littoralis Boisduval (Lepidoptera: Noctuidae), was infective to a laboratory colony of K. flavicollis (Fabricius) (Kalotermitidae) (Al Fazairy and Hassan 1988). Termites died 2-10 days post-infection under laboratory conditions and the authors suggested that control of K. flavicollis with NPV might be feasible. ...
Chapter
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Termites are primarily wood-feeding insects, consisting of approximately 2,650 species worldwide. Some of the subterranean termite species are major pests that destroy agricultural crops, live trees, and wooden structures in the houses. Thus, termites cause significant economic losses in tropical and subtropical areas, and the occurrence of termites in cultivable lands is becoming a major threat to crop plants worldwide. Termite control in agricultural crops is usually done by adopting suitable cultural practices or by preventing termite infestations through application of physical and chemical insecticidal barriers. However, due to long persistence of residual chemical insecticides in soil and their possible entry in food chain, recently there is more emphasis on characterization of biocontrol agents for control of termites that are safer and environment friendly. Different pathogens including bacteria, fungi, protozoa, viruses, and nematodes have been found to kill the termites under laboratory as well as under field conditions. These pathogens could be applied as bio-termiticides. The various microorganisms, however, differed substantially in their pathogenicity to termites. The various metabolites responsible for killing of termites could be either the production of toxins, siderophores, proteases, and hydrocyanic acid or through suppression of immune system. Synergistic combination of biocontrol agents with chemical pesticides and cultivation of termite-resistant crops could help in the management of termites under field conditions.
... A report published in 1987 suggested that SpliNPV infected two species of locust (Order Orthoptera): the African migratory locust, Locusta migratoria migratorioides, and the desert locust, Schistocerca gregaria (Bensimon et al., 1987). A report published in 1988 suggested that an uncharacterized SpliNPV isolate from Egypt could infect the wood-dwelling termites (Order Isoptera), Kalotermes flavicollis (Fazairy and Hassan, 1988). Faktor and Raviv (1996), however, were unable to detect the presence of virus in SpliNPV-infected L. migratoria by polymerase chain reaction. ...
... SpliNPV infects larvae of S. littoralis and S. litura and replicates well in cell lines established from S. frugiperda (Sf9 and Sf21) and S. littoralis (CLS79) but does not grow in cell lines derived from T. ni (TN368) or B. mori (BmN) (Maeda et al., 1990). Published reports have suggested that SpliNPV can infect two species of locust (Order: Orthoptera), L. migratoria migratorioides and S. gregaria (Bensimon et al., 1987), as well as species of wood-dwelling termites (Order: Isoptera), K. flavicollis, although the virus detected in that study was not characterized genetically and we have no way of knowing if it was related to the virus with which we are working (Fazairy and Hassan, 1988). Faktor and Raviv (1996) recently reported that they were unable to detect viral DNA after infection in L. migratoria with SpliNPV occlusion bodies. ...
Article
We determined that the type B nucleopolyhedrovirus of the Egyptian cottonworm, Spodoptera littoralis (SpliNPV), can infect a cell line derived from a grasshopper. We compared the infectivity of SpliNPV in two lepidopteran cell lines (Sf9 and Md210) and in a cell line (MSE4) derived from the western migratory grasshopper, Melanoplus sanguinipes (Orthoptera: Acrididae). Both Sf9 and MSE4 cells were permissive for SpliNPV replication and supported production of viable progeny. Md210 cells were nonpermissive for SpliNPV, and although the virus entered into these cells, they supported neither viral replication nor production of viable progeny. Infection of MSE4 cells with SpliNPV resulted in cytopathic effects within 48 h post infection and complete destruction of the cells within 5 days. Both virions and polyhedra were detected within virus-infected MSE4 cells by transmission electron microscopy. Extracellular virions were detected in the culture medium and were infectious to Sf9 cells, indicating that the MSE4 cells supported production of viable virus progeny.
... Very less work was done till now on virus activity against termites. Gibbs et al.,(1970) isolated a virus that infects Coptotermes lacteus, similar to the honey bee paralysis virus Apis mellifera L. A nuclear polyhedrosis virus, obtained from Spodoptera littoralis, Boisduval caterpillars, has been infectious to laboratory colony of Kalotermes flavicollis, they died after two days of infection (Al-Fazairy and Hassan, 1988). The principal factor influencing the efficacy of viral pathogens is the nature of the pest to be controlled. ...
Article
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For increased crop production, the role of chemical termiticides cannot be neglected as they have provided the efficient way to achieve green revolution. But the present scenario has forced mankind to search for alternative options. While keeping in mind the concept of sustainable agriculture, pest management including termites and other phyto-diseases etc. needs to be focused. For the achievement of the above stated goal, eco-friendly and cost-effective strategies need to be emphasized. Biopesticidal agents that mainly comprise of herbal and microbial formulations are known to exhibit anti termite activity and have a pivotal role in the production of organic food products. In order to reduce the chemical consumption, the vast area of biological alternatives needs to be explored as they provide us with many beneficial aspects like sustainability, suitable application, biodegradable nature, target specificity etc. Further, the bioactive components of such biological agents can later be used as commercially viable termiticides in the form of formulations. These herbal and microbial termiticides are effective and have immense scope to be used in future for sustainable development.
... To date, however, remarkably little is known about termite viruses, with only a small number of DNA viruses identified: entomopoxvirus [16,17] and nuclear polyhedrosis virus [18] have been identified in Reticulitermes flavipes and Kalotermes flavicollis, Caudovirales bacteriophage were found infecting termite symbionts [8,19,20], and single-stranded DNA viruses from the families Circoviridae, Microviridae, and Genomviridae have been detected in several termite species [8,21]. In marked contrast, there has been no research into the RNA virome of termites. ...
Article
Full-text available
Despite their ecological importance, nothing is known about the diversity and abundance of RNA viruses in termites (Termitoidae). We used a metatranscriptomics approach to determine the RNA virome structure of 50 diverse species of termite that differ in both phylogenetic position and colony composition. From these samples, we identified 67 novel RNA viruses, characterized their genomes, quantified their abundance and inferred their evolutionary history. These viruses were found within or similar to those from the Togaviridae, Iflaviridae, Polycipiviridae, Flaviviridae, Leviviridae, Narnaviridae, Mitoviridae, Lispivirdae, Phasmaviridae, Picobirnaviridae and Partitiviridae. However, all viruses identified were novel and divergent, exhibiting only 20% to 45% amino acid identity to previously identified viruses. Our analysis suggested that 17 of the viruses identified were termite-infecting, with the remainder likely associated with the termite microbiome or diet. Unclassified sobemo-like and bunya-like viruses dominated termite viromes, while most of the phylogenetic diversity was provided by the picobirna-and mitovirus-like viruses. Of note was the identification of a novel flavi-like virus most closely related to those found in marine vertebrates and invertebrates. Notably, the sampling procedure had the strongest association with virome composition, with greater RNA virome diversity in libraries prepared from whole termite bodies than those that only sampled heads.
... Next, Nuclear Polyhedrosis Viruses (NPV) also can act as a biological control agent. This virus can infect the intestine of termite directly with virion as matrix protein called Polyhedral Inclusion Bodies (PIB) (Fazairy and Hassan, 1988). This virus is suggested as a good candidate for biological control of termites because it has the capability to complete its life cycle and spread, before the host dies (Sahayaraj, 2017). ...
Article
Full-text available
Termites are perceived as decomposers and as pests in an ecosystem. A study on the species composition of termites in different soil types (i.e. clay, sand and peat) in oil palm plantations was conducted between 6 April 2015 and 10 December 2015 in nine selected localities in Johor (Malaysia) and Riau (Indonesia). Sampling of termites was conducted using belt transects of 100 m in length and 4 m in width in the oil palm plantation. A total of three replicates for each soil types were done from the nine transects for each location. A total of 41 species from five subfamilies (i.e. Coptotermitinae, Rhinotermitinae, Termitinae, Macrotermitinae and Nasutitemitinae) and two families (i.e. Rhinotermitidae and Termitidae) of termite species were successfully sampled and recorded. Sand soil (81 colonies: 12 species; four subfamilies; two families) recorded the highest colonies, followed by peat soil (62 colonies; 12 species; five subfamilies; two families), and clay soil (47 colonies consisting; nine species, four subfamilies and two families). There was a significant difference (χ2 = 618,886 df = 328, p<0.005) between soil types and termite species composition that were found in the oil palm plantation. This study identified that the diversity and abundance of termites differed between soil types in different oil palm plantations.
... Next, Nuclear Polyhedrosis Viruses (NPV) also can act as a biological control agent. This virus can infect the intestine of termite directly with virion as matrix protein called Polyhedral Inclusion Bodies (PIB) (Fazairy and Hassan, 1988). This virus is suggested as a good candidate for biological control of termites because it has the capability to complete its life cycle and spread, before the host dies (Sahayaraj, 2017). ...
Article
Full-text available
Termites are perceived as decomposers and as pests in an ecosystem. A study on the species composition of termites in different soil types (i.e. clay, sand and peat) in oil palm plantations was conducted between 6 April 2015 and 10 December 2015 in nine selected localities in Johor (Malaysia) and Riau (Indonesia). Sampling of termites was conducted using belt transects of 100 m in length and 4 m in width in the oil palm plantation. A total of three replicates for each soil types were done from the nine transects for each location. A total of 41 species from five subfamilies (i.e. Coptotermitinae, Rhinotermitinae, Termitinae, Macrotermitinae and Nasutitemitinae) and two families (i.e. Rhinotermitidae and Termitidae) of termite species were successfully sampled and recorded. Sand soil (81 colonies: 12 species; four subfamilies; two families) recorded the highest colonies, followed by peat soil (62 colonies; 12 species; five subfamilies; two families), and clay soil (47 colonies consisting; nine species, four subfamilies and two families). There was a significant difference (χ 2 = 618 886 df = 328, p<0.005) between soil types and termite species composition that were found in the oil palm plantation. This study identified that the diversity and abundance of termites differed between soil types in different oil palm plantations.
... Gibbs et al. (1970) isolated a virus infecting Coptotermes lacteus (Froggatt) (Rhinotermitidae), which was similar to acute paralysis virus of the honey bee Apis mellifera Linnaeus (Hymenoptera: Apidae). A nuclear polyhedrosis virus, obtained from caterpillars of Spodoptera littoralis Boisduval (Lepidoptera: Noctuidae), was infective to a laboratory colony of Kalotermes flavicollis (Fabricius) (Kalotermitidae) (Al Fazairy and Hassan 1988). Termites died 2-10 days postinfection of viruses under laboratory conditions. ...
Book
This book presents a comprehensive collection of articles illustrating the importance of microbial community structure and function for ecosystem sustainability and environmental reclamation. It addresses a diverse range of topics, including microbial diversity, physiology, genomics, ecosystem function, interaction, metabolism, and the fruitful use of microbial communities for crop productivity and environmental remediation. In addition, the book explores issues ranging from general concepts on the diversity of microorganisms in soil, and ecosystem function, to the evolution and taxonomy of soil microbiota, with future prospects. It covers cutting-edge methods in soil microbial ecological studies, rhizosphere microflora, the role of organic matter in plant productivity, biological nitrogen fixation and its genetics, microbial transformation of plant nutrients in soil, plant-growth-promoting rhizobacteria, and organic matter transformation. The book also discusses the application of microbes in biodegradation of xenobiotic contaminants. It covers bio-fertilizers and their role in sustainable agriculture and soil health, biological control of insect pests and plant pathogens, and the latest tools of omics in soil microbiology, i.e. genomics, proteomics, transcriptomics and metabolomics, which offer pioneering approaches to the exploration of microbial structure and function.
... Over 40 species of fungi have been found associated with a single termite species (Zoberi and Grace 1990). In addition, some pathogenic viruses, for example, Entomopoxvirinae and the nuclear polyhedrosis virus, are known to infect the colonies (Al-Fazairy and Hassan 2011;Chouvenc et al. 2013). Also, a total of 118 actinobacterial isolates were collected (Sujada et al. 2014) from the three types of nests (mound, carton, and subterranean nests). ...
Chapter
Full-text available
Termites show a structured social life, provisioned with work-based divisions, i.e., king, queen, workers, and soldiers. Ecologically, termites interact with living and nonliving surroundings and deliver a wide range of behaviors. They ensure the survival of colony members by harvesting food, constructing shelters, defending the external and internal threats, and nourishing the new borne progeny in a systematic manner. The termites are equipped with complex characteristics such as chemical communication, morphological and chemical defense, and brood care that enable their successful survival. Besides their usefulness, these tiny insects are a center of attraction because they damage the human economy as wood pests. In this chapter, the ecological role of termites is examined and explored.
... Gibbs et al. (1970) isolated a virus infecting Coptotermes lacteus (Froggatt) (Rhinotermitidae), which was similar to acute paralysis virus of the honey bee Apis mellifera Linnaeus (Hymenoptera: Apidae). A nuclear polyhedrosis virus, obtained from caterpillars of Spodoptera littoralis Boisduval (Lepidoptera: Noctuidae), was infective to a laboratory colony of Kalotermes flavicollis (Fabricius) (Kalotermitidae) (Al Fazairy and Hassan 1988). Termites died 2-10 days postinfection of viruses under laboratory conditions. ...
Book
This book presents a comprehensive collection of articles illustrating the importance of microbial community structure and function for ecosystem sustainability and environmental reclamation. It addresses a diverse range of topics, including microbial diversity, physiology, genomics, ecosystem function, interaction, metabolism, and the fruitful use of microbial communities for crop productivity and environmental remediation. In addition, the book explores issues ranging from general concepts on the diversity of microorganisms in soil, and ecosystem function, to the evolution and taxonomy of soil microbiota, with future prospects. It covers cutting-edge methods in soil microbial ecological studies, rhizosphere microflora, the role of organic matter in plant productivity, biological nitrogen fixation and its genetics, microbial transformation of plant nutrients in soil, plant-growth-promoting rhizobacteria, and organic matter transformation. The book also discusses the application of microbes in biodegradation of xenobiotic contaminants. It covers bio-fertilizers and their role in sustainable agriculture and soil health, biological control of insect pests and plant pathogens, and the latest tools of omics in soil microbiology, i.e. genomics, proteomics, transcriptomics and metabolomics, which offer pioneering approaches to the exploration of microbial structure and function. Keywords Biofertilizer Biogeochemical Cycle Microbial Diversity Microbial Interaction Soil Microbial Ecology
... So far, there have been very limited data on viruses capable of infecting termites (Al Fazairy and Hassan, 1988). It has been suggested that a virus infecting termites would be an ideal candidate for biological control (Chouvenc et al., 2011). ...
Article
Full-text available
The Formosan subterranean termite; Coptotermes formosanus is nutritionally dependent on the complex and diverse community of bacteria and protozoa in their gut. Although, there have been many studies to decipher the taxonomic and functional diversity of bacterial communities in the guts of termites, their bacteriophages remain unstudied. We sequenced the metavirome of the guts of Formosan subterranean termite workers to study the diversity of bacteriophages and other associated viruses. Results showed that the termites harbor a virome in their gut comprised of varied and previously unknown bacteriophages. Between 87–90% of the predicted dsDNA virus genes by Metavir showed similarity to the tailed bacteriophages (Caudovirales). Many predicted genes from the virome matched to bacterial prophage regions. These data are suggestive of a virome dominated by temperate bacteriophages. We predicted the genomes of seven novel Caudovirales bacteriophages from the termite gut. Three of these predicted bacteriophage genomes were found in high proportions in all the three termite colonies tested. Two bacteriophages are predicted to infect endosymbiotic bacteria of the gut protozoa. The presence of these putative bacteriophages infecting endosymbionts of the gut protozoa, suggests a quadripartite relationship between the termites their symbiotic protozoa, endosymbiotic bacteria of the protozoa and their bacteriophages. Other than Caudovirales, ss-DNA virus related genes were also present in the termite gut. We predicted the genomes of 12 novel Microviridae phages from the termite gut and seven of those possibly represent a new proposed subfamily. Circovirus like genomes were also assembled from the termite gut at lower relative abundance. We predicted 10 novel circovirus genomes in this study. Whether these circoviruses infect the termites remains elusive at the moment. The functional and taxonomical annotations suggest that the termites may harbor a core virome comprised of the bacteriophages infecting endosymbionts of the gut protozoa.
... They are highly specifi c in their host range, usually limited to a single type of insect. Al-Fazairy andHassan ( 1988Hassan ( , 1993) reported that nuclear polyhedrosis virus isolated from Spodoptera littoralis infects termite castes of Kalotermes fl avicollis. They mentioned that all tested castes of termites were quite equal in their response to the virus infection and produced over 90 % mortality at 6.4 × 10 7 polyhedra/ml concentration. ...
Chapter
Full-text available
Termites cause economic losses by directly injuring and destroying both living and dead vegetation. They can damage right from sowing the crops till harvest. Billions of dollars are spent annually throughout the world to control and prevent termite infestation. Many bacteria, fungi, and nematodes occurring naturally in soils are known to suppress termite activity. Entomopathogenic nematodes (EPNs) and their associated bacterial symbionts are highly specific in their host range and compatible with many pesticides. EPNs, also called beneficial nematodes, are commercially used to control insect pests. These nematodes offer an environmentally safe alternative to chemical insecticides, and a wide range of EPNs are effective against various termite species. Only a limited number of field studies have been conducted using EPNs as control agents for termites. New isolates of EPNs may prove potential against termite pests in the field. This chapter outlines the potentials of entomopathogenic nematodes in termite management.
... The microbial higher taxa should not be regarded as definitive, as there are currently no completely agreed upon classifications for any of these groups. Little work on termite virology is known to us, and only one study is cited in the book (Ahlam et al. 1988). ...
Article
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Biology of Termites: A Modern Synthesis (Bignell DE, Roisin Y, Lo N, (Editors), Springer, Dordrecht, 576pp, ISBN 978-90-481-3976-7, e-ISBN 978-90-481-3977-4, DOI 10.1007/978-90-481-3977-4) was published in 2011. With the agreement of the publishers, we give a taxonomic index of the book comprising 494 termite entries, 103 entries of other multicellular animal species mentioned as associates or predators of termites, with 9 fungal, 60 protist, and 64 prokaryote identities, which are listed as termite symbionts (sensu stricto). In addition, we add descriptive authorities for living (and some fossil) termite genera and species. Higher taxonomic groupings for termites are indicated by 25 code numbers. Microorganisms (prokaryotes, protists, and fungi) are listed separately, using broad modern taxonomic affiliations from the contemporary literature of bacteriology, protozoology, and mycology.
... Twenty-four species of Lepidoptera were tested. Additionally, one species of termite was inoculated with either virus to investigate claims that a NPV isolated from S. littoralis infected a termite, Kalotermes Xavicollis (Fabricius) (Al-Fazairy and Hassan, 1988). A group of 35 termites was fed on three sterilized wood slices (8 £ 8 £ 1 mm) that had been dipped in a concentration of 10 9.5 OBs/ml of viral suspension. ...
Article
Twenty-two lepidopteran and one termite nontarget species were challenged with the in vivo-cloned Spodoptera littoralis multicapsid nucleopolyhedrovirus (SpliMNPV) or Spodoptera litura multicapsid NPV (SpltMNPV). S. litura larvae were used as controls to verify the infectivity of the NPV. We demonstrated that three species of Lepidoptera, S. litura and Spodoptera exigua belonging to the family Noctuidae, and Arna pseudoconspersa belonging to the family Lymantriidae, died of NPV infection. These insects contained occlusion bodies in visual analyses under phase contrast microscopy. However, dot-blot hybridization analyses of the viral DNA indicated that only progeny viruses produced in S. litura and S. exigua had high degree of homology with the inoculated viruses, whereas hybridization signals were not detected in the analysis of viral DNA from A. pseudoconspersa. Restriction endonuclease analyses revealed that the progeny viruses in S. litura and S. exigua were identical to the inoculated viruses, confirming true infection of S. litura and S. exigua with the virus strains. Further bioassays indicated that strains of SpliMNPV and SpltMNPV were equally virulent to second-stadium larvae of S. litura, but SpliMNPV was more virulent to second-stadium larvae of S. exigua. S. exigua larvae killed by the SpliMNPV strain liquefied soon after death, but those killed by the SpltMNPV strain did not. Our results indicate that the application of NPV may have impact on nontarget Lepidoptera with latent viral infections.
... Also, whereas many prospective termite pathogens have been tested in the laboratory, relatively few have been given field trials. (I<alotermitidae) (Al Fazairy &: Hassan, 1988). Termites died 2-10 days post infection, and, based only on the laboratory results, the authors suggested that control of K. fla'Vicollis with. ...
Article
Full-text available
Costs associated with subterranean termite damage and control are estimated to approach $2 billion annually in the United States alone. The Formosan subterranean termite, Coptotermes formosanus Shiraki, is one of the more economically important subterranean species. In recent years, the shortcomings associated with conventional chemical control methods have prompted policymakers and scientists to evaluate the potential for biological control of subterranean termites (C. formosanus in particular), that is, to determine the potential for natural enemies - predators, parasitoids and pathogens - to suppress termite populations. Ants are the greatest predators of termites, and may have a considerable local impact on termite populations in some areas of the world. A few parasitoids of termites are known, but their potential for regulating termite populations seems negligible. Characteristics of the colony, such as a protected, underground location (and, for the C. formosanus nest, its modular and dispersed nature), are likely to limit the impact predators and parasitoids have on subterranean termites. Thus, there seems little potential for use of these agents for subterranean termite control. For various reasons, pathogenic organisms, such as viruses, bacteria, Protozoa, nematodes and most fungi, have shown little promise for use in biological termite control. However, research suggests that strains of two well-studied, endoparasitic fungi, Beauveria bassiana and Metarhizium anisopliae, when employed in baiting schemes, may offer the potential for at least some measure of subterranean termite control, although their successful use is compromised by a number of inherent biological limitations and logistical problems that have yet to be solved. Although not strictly in the realm of classical biological control, recent studies suggest that natural products, such as ant semiochemicals and fungal metabolites (siderophores), or their synthetic analogues, eventually might find a use in termite control programmes as repellents or insecticides in wood treatments or soil applications if stable formulations can be developed.
Chapter
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Various viable options in termite management are termite baits (novaluron, hexaflumuron), the use of synthetic pesticides/insecticides/termiticides (bifenthrin, chlorpyrifos, cypermethrin, fenvalerate, Imidachloprid, permethrin, dexamethasone, ibuprofen, aldrin, Dieldrin, etc.), chemicals (boric acid, ibuprofen sodium salt), or botanicals (Withania somnifera, Croton tiglium, Hygrophila auriculata, Trachyspermum ammi, Pimenta dioica, Carum carvi, Anethum graveolens, Pelargonium graveolens, Litsea cubeba, Croton urucurana, Melia azedarach, Crotalaria burhia, and Anacardium occidentale). Further, natural enemies include mammals, birds, insects (ants, reduviids), Araneae (spiders), microbes–bacteria [Bacillus thuringiensis], fungi [Conidiobolus sp., Aspergillus flavus, Metarhizium anisopliae, Beauveria bassiana, B. pseudobassiana, and Isaria fumosorosea), and nematodes (Heterorhabditis sp., Steinernema sp.). Other methods such as dug trench are also available for termite management. In addition, many commercial products are available in the market (e.g., Bioblast). No one has integrated more than two or three individual components for termite control that are environmentally safe and effective. Here we discuss how to utilize many integrated pest management components, to save crops and environment.
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The use of pathogens as biological control agents has long been considered a promising technology for termite control. Over the past five decades, there has been a large accumulation of scientific literature on the development of control methods using various pathogens. However, despite the evidence that biological control has essentially failed, or failed to be developed, as a method for commercial termite control, this field of research remains very active. In this study, we examined 50years of research on the microbial control of termites in order to understand why commercial products have failed to be developed and why this field of research remains so active. All (to the extent of our knowledge) of the literature published between 1960 and 2011 was evaluated to investigate any publication bias and to detect false positives in the form of overly optimistic conclusions. This re-interpretation supports the idea that the conclusions frequently expressed have been misleading to some extent, or at least overly optimistic, about the potential for application of biological control to termites. Many results obtained from bioassays with poor biological relevancy have been interpreted as promising, while few results actually support practical application. We also suggest that the failure of termite biological control and the continued research emphasis in this area resulted in part from unrealistic optimism about the potential for development of environmentally friendly methods to control termites, publication bias, and poor understanding of termite biology.
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While pest species of termites are thought to belong predominantly to four families comprising the lower termites, the species causing the most damage to tropical agriculture belong to three of the four subfamilies of higher termites, lacking protist symbionts. A wide range of crops are affected, including trees in plantations and orchards, coconuts, palms, sugar cane, rice, maize, wheat, sorghum, groundnuts, coffee, tea, cocoa, yam, cassava and cotton. Market gardens and pastures can also be damaged. Organochlorine and organophosphate insecticides, once very effective agents of chemical control, are now prohibited or restricted, owing to their several toxicities, but alternatives of comparable efficacy in cropping systems are yet to be found. Integrated control strategies, combining improved cultural practices, attempts to increase plant vigour, and the introduction of biological agents to reduce termite populations may hold some hope for the future. Among the biological agents, entomopathogenic fungi and nematodes seem the most suitable for research and development.
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The assessment of environmental risks associated with genetically engineered baculovirus pesticides depends on an accurate knowledge of the host range of each virus. However, studies of baculovirus host ranges based solely on symptomology may misidentify as nonhosts any species with symptomless infections. This project used recombinant viruses that allowed detection of symptomless as well as pathogenic virus infections. Seven recombinant isolates ofAutographa californicanuclear polyhedrosis virus (AcMNPV),Bombyx morinuclear polyhedrosis virus,Lymantria disparnuclear polyhedrosis virus (LdMNPV), andOrgyia pseudotsugatanuclear polyhedrosis virus were tested by either hemocoelic injection orper osinoculation for their potential replication in 23 insect species from eight orders and 17 families. The recombinant viruses contained genes coding for β-galactosidase, secreted alkaline phosphatase (SEAP), or luciferase under the transcriptional control of either the polyhedrin or ETL promoter. Replication was initially assessed based on detection of the reporter gene products. Results obtained with β-galactosidase or SEAP as indicators were more consistent but less sensitive than those with luciferase. With all insects tested, much higher reporter enzyme activities were found with the β-galactosidase reporter gene placed under the polyhedrin promoter than under the ETL promoter. As indicated by reporter enzyme activity after injection with the budded virus particles, the AcMNPV replicated in more species than did the other viruses, and the LdMNPV was the most host specific. Most of the insect species tested did not support detectable replication of any of the viruses. While an observation of symptoms of viral infection was usually concurrent with detection of reporter gene activities, with certain insect/virus combinations, little or no reporter gene activity was detected even though the feeding activity and growth rates were significantly reduced relative to those of the sham-injected controls. The results of this project provide a database for the establishment of future environmental risk assessment protocols and guidelines with baculovirus pesticides.
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Non-chemical control of termites in agriculture and forestry is attracting renewed interest following increasing restrictions on the use of persistent organochlorine (cyclodiene) insecticides. Non-chemical control involves methods which attempt, without using commercial pesticides, to (i) prevent termite access to the plants, (ii) reduce termite numbers in the vicinity of the plants or (iii) reduce susceptibility/increase resistance of the plants themselves. There have been few adequate trials of any of these methods. Numerous cultural procedures have been suggested, including measures to enhance plant vigour, to manipulate termite numbers and behaviour, and others whose mode of action is unclear. Many are simply part of good agricultural/silvicultural practice and to be recommended. Biological control by predators or pathogens is unlikely to be successful due to the termites' social structure and behavioural responses to infected individuals and to loss of individuals to predators. The use of ‘natural’ insecticides from locally available plant products may be effective in some cases but, as they are not subject to the same rigorous safety and environmental evaluation as commercial pesticides, their use cannot be sanctioned unconditionally. Other locally available products, e.g. wood ash, have not been adequately evaluated. Removal of reproductives from the nest and construction of physical barriers may have limited applications, but resistant species and varieties, combined with appropriate cultural methods and, perhaps, minimal use of modern pesticides in an integrated approach, offer the greatest potential for a long term solution. The lack of critical scientific evaluation of non-chemical control makes it a field wide open for research.
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The host range of a multiply enveloped nuclear polyhedrosis virus (NPV) (Baculoviridae) isolated from the cabbage moth, Mamestra brassicae (Lepidoptera: Noctuidae), was determined by challenging a wide range of insect species with high (10 polyhedral inclusion bodies) and low (10 polyhedral inclusion bodies) doses of the virus. The identity of the progeny virus was confirmed by dot blotting. Analysis of 50% lethal dose was carried out on selected species, and the progeny virus was identified by using restriction enzyme analysis and Southern blotting. Other than the Lepidoptera, none of the species tested was susceptible to M. brassicae NPV. Within the Lepidoptera, M. brassicae NPV was infective to members of four families (Noctuidae, Geometridae, Yponomeutidae, and Nymphalidae). Of 66 lepidopterous species tested, M. brassicae NPV was cross-infective to 32 of them; however, 91% of the susceptible species were in the Noctuidae. The relevance of host range data in risk assessment studies is discussed.
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A nuclear polyhedrosis virus isolated from the alfalfa looper, Autographa californica, infected larvae of the pink bollworm, Pectinophora gossypiella. Transmission was confirmed by light and electron microscopy and by feeding polyhedra obtained from pink bollworm cadavers to larvae of the cabbage looper, Trichoplusia ni.Preliminary studies were made of the infectivity, symptomatology, and histopathology of the virus in pink bollworm larvae.
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A histological and ultrastructural study of a nuclear polyhedrosis virus in the webbing clothes moth, Tineola bisselliella, was conducted. Polyhedral development was observed in nuclei of cells of the foregut, cardiac valve, midgut, pyloric valve, hindgut, Malpighian tubules, ganglia of the ventral nerve cord, muscle, tracheae, fat, and hypodermis. Observations made with the electron microscope suggest that virions from the gut lumen are transported in vesicles through the cytoplasm into the nuclei of the columnar cells. Here they are released, replicate, take on membrane, and ultimately become multiply occluded in polyhedral protein. Polyhedra observed in nuclei of other tissues appeared identical to those in the gut.
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Adults of Heliothis virescens infected with a cytoplasmic polyhedrosis virus (CPV) produced healthy offspring when their eggs were surface sterilized with either 15% formaldehyde or 0.2% sodium hypochlorite solution. Larvae from infected parents (1) cultured on a vitamin-deficient medium, (2) exposed to cold treatment (5°C, 24 hr), or (3) as progeny of adults from diapaused infected pupae, produced the same number of infected individuals as larvae reared in the customary way. Field studies indicated that the percent of CPV infection in larvae originating from virus-infected parents was density dependent.
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A nuclear polyhedrosis virus isolated from the alfalfa looper, Autographa californica, was found to infect several species of caterpillars including the cabbage looper, Trichoplusia ni; the beet armyworm, Spodoptera exigua; and the saltmarsh caterpillar, Estigmene acrea. Studies were therefore conducted to determine the quantitative effects of passage through the alternate hosts, S. exigua and E. acrea, on the infectivity of this virus to newly hatched first-instar cabbage looper larvae. When 11 preparations of polyhedra obtained from a like number of primary passages through the original or alternate hosts were assayed and the mortality at 7-, 10-, and 14-day intervals were subjected to probit analysis, the LD50s for the three intervals differed but those for the preparations at any given interval did not. Therefore, any of the three hosts could be used to propagate the virus, and whichever proves the easiest to rear and provides the highest yields of polyhedra can be selected.
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A nonoccluded virus was isolated from larvae of the army cutworm, Euxoa auxiliaris. Infected larvae became lethargic and shrunken, and death usually occurred 12–20 days after infection. The primary site of viral infection and replication appeared to be the nuclei of midgut epithelial cells; however, virus replication also occurred in cells of the tracheal matrix and in muscle. Nuclei in early stages of the infection contained large granular areas with the chromatin scattered near the nuclear membrane. These areas differentiated into viral particles that measured 24 nm and formed crystalline arrays, occasionally 10 μm long. Disruption of the nuclear membrane liberated these arrays of particles into the cytoplasm. Fluorescence microscopy studies indicated that the viral particles contained DNA. The crystalline arrays were Feulgen positive. The virus also infected larvae of the armyworm, Pseudaletia unipuncta, and corn carworm, Heliothis zea, in laboratory tests.
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The pathogenicity of an American isolate of the nucleopolyhedrosis virus of Porthetria dispar was studied. Laboratory data on third-instar larvae showed that mortality was directly related to virus concentration. The computed LD50 was 1,729 PIBs/larva or 72 PIBs/mg larval body weight. The LT50's for 2.5 × 106, 2.5 × 105, 2.5 × 104, 5 × 103, and 2.5 × 103 PIBs/larva were 8.1, 9.9, 11.3, 12.2, and 13.1 days, respectively. Approximately 37 and 60% of the total larval mortality occurred during the third- and fourth-instar, respectively. The periods to pupation and the pupal weights of survivors apparently were not affected by virus concentration. Moth emergence from surviving pupae was not reduced.
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The pathology of a Baculovirus (BV) in Aedes triseriatus was studied. The virus infected the cardia, gastric caeca, and the entire stomach of larval midgut epithelium. The progression of the disease was similar to that of other Baculoviruses of the nuclear polyhedrosis virus (NPV) type. Rodshaped nucleocapsids were formed within a Feulgen-positive virogenic stroma and along the nuclear envelope. These nucleocapsids were enveloped by a membranous material and occluded randomly in small irregular and polyhedral proteinic inclusions. The disease differed from other BVs of the NPV type in that the small proteinic inclusions gradually coalesced as they grew, forming large fusiform inclusions.Preliminary mortality studies indicated that early-instar larvae were the most susceptible to the virus.