Entomopathogenic Fungus Beauveria Research Articles

Pathogenicity of native isolates of entomopathogenic fungi Beauveria and Metharizium genera on Microcerotermes diversus (Blattodea: Termitidae) in the laboratory

Microcerotermes diversus Silvestri (Blattodea: Termitidae) is a worldwide destructive termite whose control by conventional methods is often difficult. Biological control using entomopathogenic fungi could be an alternative management strategy. Two species of entomopathogenic fungi, Metarhizium anisopliae and Beauveria bassiana, isolated from natural habitats of Mashhad and Lahijan regions, Iran. The fungi were characterized based on sequences of ITS gene as well as classic data. Then, the infectivity of both isolates of M. anisopliae and B. bassiana in different concentrations (1 × 104, 1 × 105, 1 × 106, 1 × 107, and 1 × 108 conidia/ml) were evaluated under laboratory conditions by two methods, including spray and pipetting against termite, M. diversus. Both entomopathogenic fungi species were capable of infecting and killing M. divesrus. In the pipetting method, the LC50 value for B. bassiana and M. anisopliae calculated 8.03 × 105 (conidia/ml) and 1.03 × 106 (conidia/ml), respectively. But in the spray method, the effect of M. anisopliae on M. diversus was more than B. bassiana. The LC50 value in the spray method for B. bassiana and M. anisopliae was 3.52 × 107 (conidia/ml) and 1.65 × 106 (conidia/ml). The mortality caused by the fungus was dose-dependent, with the highest mortality recorded at the highest concentration. In the pipetting method, the mortality rate for B. bassiana and M. anisopliae was 0 to 97.5% and 0 to 100% at 8 day post infection. In the spray method, the mortality percentage for B. bassiana was from 2.5 to 72.5% and for M. anisopliae was 0 to100% by 4 days post-infection. The results of this study indicated that B. bassiana and M. anisopliae are potentially useful biological control agents for M. diversus. Future studies with field trails will provide a confident approach toward termite management.

The effects of a myrmecochore-produced chemical on entomopathogenic fungal growth and seed-dispersing ant survival rates and foraging patterns.

Myrmecochory, a type of ant-mediated seed dispersal, is a diffuse, widespread mutualism in which both partners are purported to benefit from the services or rewards of the other. However, ant benefits in this interaction are conflicted and understudied, especially in the context of microbial third parties. Here, we investigate the effect of a myrmecochore plant-produced antimicrobial chemical (sanguinarine) on the growth of a common entomopathogenic fungus (Beauveria bassiana). We then explore whether sanguinarine, through its effect on entomopathogen growth, might influence ant survival and foraging behavior. At high concentrations, sanguinarine increased the growth of B. bassiana, but fungal growth was not affected at concentrations of sanguinarine near natural levels produced in seeds. When ant colonies were exposed to B. bassiana, survival was not affected by a sanguinarine-supplemented diet. Furthermore, ant foraging patterns (preference for or avoidance of food items with sanguinarine) did not change when ants were exposed to the entomopathogen. Though sanguinarine promotes the growth of an entomopathogen at higher concentrations, which might pose an additional risk for ants in myrmecochory, we assert that social immune behavioral defenses (such as grooming or redispersal of seeds after elaiosome consumption) help ants mitigate this risk. By incorporating a microbial third party into this ant-plant interaction, we seek to more fully understand the risks and benefits provided to both partners in this mutualism. We encourage the investigation of third-party influences in reciprocal pairwise interactions to assist in the understanding of the evolution and persistence of mutualisms.

Compatibility of entomopathogenic fungus Beauveria bassiana (Bals.) with selected chemical insecticides

In vitro investigation was carried out to examine the compatibility of Beauveria bassiana (Bals.) (Bb-5a) with ten insecticides through poisoned food technique. The insecticides were tested at three different doses viz., field recommended dose (RD), half of the recommended dose (0.5 × RD) and double the recommended dose (2 × RD). Among all the chemical insecticides tested for their compatibility, only diafenthiuron was not compatible with B. bassiana and it inhibited the growth. While, imidacloprid, thiamethoxam, acetamiprid, clothianidin, acephate, fipronil, buprofezin, flonicamid and azadirachtin were showed compatible at 14th and 30th day after inoculation. Consequences of the present investigation recommended that aside diafenthiuron, rest of the insecticides examined can be safely used along with B. bassiana in integrated pest management.

Isolation of Beauveria bassiana from the Chagas Disease Vector Triatoma infestans in the Gran Chaco Region of Argentina: Assessment of Gene Expression during Host-Pathogen Interaction.

A native strain of the entomopathogenic fungus Beauveria bassiana (Bb-C001) was isolated from a naturally infected Triatoma infestans, Klug (Hemiptera: Reduviidae) adult cadaver in the Gran Chaco region, Salta province, Argentina. The isolate was both phenotypic and molecularly characterized in a context of fungus-insect interaction, by measuring the expression pattern of toxin genes during infection and immune response of T. infestans. The commercial strain GHA of B. bassiana, which was previously used in field interventions to control these vectors, was used as reference in this study. The phylogenetic trees based on both ribosomal internal transcribed spacer (ITS) and elongation factor 1-alpha (EF1-α) indicated that Bb-C001 fits into a B. bassiana cluster, and the sequence-characterized amplified regions (SCAR) showed that Bb-C001 is different from the GHA strain. There were no differences between both strains regarding viability, radial growth, and conidia production, either in the median survival time or insect mortality. However, Bb-C001 showed a higher expression than GHA of the bassianolide synthetase gene (BbbslS) during infection, and similar levels of the beauvericin synthetase gene (BbbeaS). Immune-related genes of T. infestans nymphs (limpet-2 and defensin-1, -2, and -6) were later expressed and thus insects failed to stop the infection process. These results showed that B. bassiana Bb-C001 is a promised fungal strain to be incorporated in the current biological control programs of T. infestans in Salta province, Argentina.

Transcriptomic analyses reveal comprehensive responses of insect hemocytes to mycopathogen Beauveria bassiana, and fungal virulence-related cell wall protein assists pathogen to evade host cellular defense

ABSTRACT Entomopathogenic fungi naturally infect insect hosts in environment. Fungal invasion and host immune defense are still in the progress of co-evolution. In this study, entomopathogenic fungus Beauveria bassiana and lepidopteran insect Galleria mellonella were used to investigate host cellular immunity and fungal strategy to evade host defense. First of all, genome-wide expression revealed the transcriptomic responses of hemocytes to insect mycopathogen, which dynamically varied during infection process. Enrichment analysis indicated that differentially expressed genes were primarily involved in metabolism, cellular process and immune system. Notably, cellular response involved a series of hydrolytic enzyme and antimicrobial peptide genes which were sorted together in clustering analysis. In B. bassiana, a cell-wall protein gene (BbCwp) contributes to fungal development in host hemocoel and virulence. RT-qPCR analyses indicated that infection by ΔBbCwp mutant strain caused the up-regulated expression of a series of immunity-related genes, including β-1, 3-glucan recognition protein, hydrolytic enzyme and antimicrobial peptide genes. Disruption of BbCwp resulted in a significant change in conidial lectin-binding feature and the enhanced encapsulation by the host hemocytes. After being treated with hydrolytic enzymes, ΔBbCwp mutant displayed a significantly enhanced sensitivity to osmotic and oxidative stresses. In conclusion, fungal invasion initiates comprehensive physiological responses in the host hemocytes. For mycopathogen, cell-wall protein plays an important role in fungal evasion of immunity defense and colonization in host. Our studies provide an initial framework for exploring more mechanistic details about the fungus–host interaction.

Entomopathogenic fungi decrease Rhizoctonia disease in potato in field conditions.

Rhizoctonia potato disease is widespread in the world and causes substantial yield and quality losses in potato. This study aimed to evaluate the efficacy of entomopathogenic fungi Metarhizium robertsii and Beauveria bassiana in the inhibition of potato Rhizoctonia complex disease. The efficacy of the entomopathogenic fungi M. robertsii and B. bassiana in the defense of potato against Rhizoctonia disease (stem cancer, black scrulf and other forms of manifestation on tubers) was estimated under field conditions in Western Siberia. Preplanting treatment of the tubers with B. bassiana decreased Rhizoctonia disease in the stems and stolons. At the same time, treatment with M. robertsii did not cause a decrease in Rhizoctonia disease in these organs. However, both fungi decreased the sclerotium index on the tubers of new crops. We demonstrated two mechanisms of inhibition of Rhizoctonia solani by M. robertsii and B. bassiana, including (1) direct effect, expressed as inhibition of R. solani sclerotium formation in cocultivation assays, and (2) indirect effect, which is associated with increased peroxidase activity in potato roots under the influence of colonization by entomopathogenic fungi. We suggest that the treatment of seed tubers with B. basiana can effectively manage Rhizoctonia disease during the plant vegetative season and that both fungi significantly improve the quality of the new tuber crop.

Effect of Beauveria bassiana (Bals.-Criv.) on immunity of Sesamia cretica Lederer larvae

The aim of the present research was study of entomopathogenic fungus Beauveria bassiana (Bals.-Criv.) effects on Sesamia cretica Lederer cellular immune response. When a pathogen enters into insect hemocoel, hemocytes are engaged in removing non-self-target. Prohemocytes, granulocytes, plasmatocytes and oenocytoids are known as the main circulating hemocytes in the hemolymph of larvae. The highest number of total hemocytes, plasmatocyte and granulocyte were observed at 24 h post-inoculation of B. bassiana spore suspension while, maximum number of nodules were observed at 48 h post- inoculation. The highest level of spore phenol-oxidase activity was observed at 72 h post spore inoculation. Our finding opens new insights in immune response of S. cretica in infection by B. bassiana.

Virulence Screen of Beauveria Bassiana Isolates for Australian Carpophilus (Coleoptera: Nitidulidae) Beetle Biocontrol

Carpophilus beetles are serious pests of Australian fruit and nut crops, causing significant damage through adult and larval feeding and vectoring plant diseases. Six strains of the entomopathogenic fungus Beauveria bassiana ((Balsamo) Vuillemin; Hypocreales: Cordycipitaceae), isolated from a range of hosts in Australia, together with one commercial strain, were screened for virulence to adult and larval stages of Carpophilus attacking stone fruits (C. davidsoni (Dobson)) and almonds (C. truncatus (Murray)) under laboratory conditions. The two species differed significantly in their susceptibility to the B. bassiana isolates. In the adult beetle assay, C. truncatus had a maximum Abbott’s control corrected mortality of 19% when treated with the most effective isolate, B54, compared to 52% for C.davidsoni. In larval bioassays, mortality rates for the two species were generally higher than adults: four isolates caused greater than 80% mortality in C. davidsoni; while only one isolate was considered effective against C. truncatus (causing 73% mortality), all other isolates caused less than 40% mortality. The results indicate promising potential for B. bassiana to be applied as a biopesticide as part of an integrated pest management strategy, which might take the form of a soil application against larvae or an autodissemination program using adult beetles.

Herbivore insects and predatory arthropods in freshwater swamp rice field in South Sumatra, Indonesia sprayed with bioinsecticides of entomopathogenic fungi and abamectin

Abstract. Herlinda S, Prabawati G, Pujiastuti Y, Susilawati, Karenia T, Hasbi, Irsan C. 2020. Herbivore insects and predatory arthropods in freshwater swamp rice field in South Sumatra, Indonesia sprayed with bioinsecticides of entomopathogenic fungi and abamectin. Biodiversitas 21: 3755-3768. Herbivore insect population and predatory arthropods in rice field may be effected by the application entomopathogenic fungi or synthetic insecticide. The objective of this research was to analyze individual quantity of herbivore insects and predatory arthropod inhabiting freshwater swamp rice fields treated with bioinsecticides and abamectin (commercial insecticide). This research was conducted in the freshwater swamp rice field located in Village Pelabuhan Dalam, Sub District Pemulutan, District Ogan Ilir, and South Sumatra. The experiment was arranged in a Completely Randomized Block Design consisted of four plots of treatment. The research used the bioinsecticides made from entomopathogenic fungi (Beauveria bassiana, Metarhizium anisopliae, and Cordyceps military), and abamectin. Sampling to collect arthropods inhabiting rice canopy was also conducted using an entomological net in the study locations. This research found 12 families of herbivore insects with 22 species dominated by Nilaparvata lugens and Leptocorisa acuta and 32 species of spider belonged to eight families dominated by Tetragnatha virescens and Oxyopes matiensis. The species diversity of spider was higher in the plots of the bioinsecticide compared to that of the abamectin. Predatory insects found belonged to 14 species belonged to eight families dominated by species of Ophionea nigrofasciata, Verania discolor, and Paedorus fuscipe. The abundance of predatory insects in plots sprayed with the bioinsecticides was higher compared to that of the abamectin plot. The abundance and species diversity of predatory arthropod sprayed with bioinsecticide of B. bassiana, M. anisopliae, and C. militaris did not decrease, while the population of herbivore insect tended to decrease.

The coffee agroecosystem: bio-economic analysis of coffee berry borer control (Hypothenemus hampei)

Coffee, after petroleum, is the most valuable commodity globally in terms of total value (harvest to coffee cup). Here, our bioeconomic analysis considers the multitude of factors that influence coffee production. The system model used in the analysis incorporates realistic field models based on considerable new field data and models for coffee plant growth and development, the coffee/coffee berry borer (CBB) dynamics in response to coffee berry production and the role of the CBB parasitoids and their interactions in control of CBB. Cultural control of CBB by harvesting, cleanup of abscised fruits, and chemical sprays previously considered are reexamined here to include biopesticides for control of CBB such as entomopathogenic fungi (Beauveria bassiana, Metarhizium anisopliae) and entomopathogenic nematodes (Steinernema sp., Heterorhabditis). The bioeconomic analysis estimates the potential of each control tactic singly and in combination for control of CBB. The analysis explains why frequent intensive harvesting of coffee is by far the most effective and economically viable control practice for reducing CBB infestations in Colombia and Brazil.

Pathogens Causing Anthracnose and Fruit Rots of Coffee Associated with the Coffee Berry Borer and the Entomopathogenic Fungus Beauveria bassiana in Puerto Rico.

Fruit rots reduce coffee production worldwide. Eight Colletotrichum species have been reported to cause coffee fruit rots; the most important is C. kahawae, the cause of coffee berry disease (CBD) in Africa. It is unknown whether these fruit rot pathogens can be dispersed by the coffee berry borer (CBB, Hypothenemus hampei) or whether Beauveria bassiana (a natural enemy of CBB) might reduce coffee fruit rots. We identified pathogens causing coffee fruits rots in Puerto Rico and evaluated whether B. bassiana reduced fruit rot and whether CBB could disperse pathogens. A total of 2,333 coffee fruit with CBB damage were collected; of these, 1,197 had visible growth of B. bassiana. C. fructicola, C. siamense, C. theobromicola, and C. tropicale were isolated and identified from the fruit using morphological traits and phylogeny of three nuclear genes. All four species caused internal and external rot after inoculation of healthy green coffee fruit. Coffee fruit treated with B. bassiana had significantly less fruit rot than untreated fruit, suggesting B. bassiana can protect against fruit rot. To test whether B. bassiana had a protective effect, B. bassiana and Colletotrichum were coinoculated on coffee fruit. Fruit inoculated with both B. bassiana and Colletotrichum had significantly less rot than fruit inoculated with Colletotrichum alone. To test if CBBs dispersed the pathogens, CBBs were exposed to Colletotrichum conidia and placed on green fruit, which resulted in fruit rot. This study identifies new pathogens causing coffee fruit rot, shows that C. kahawae is not the only Colletotrichum that attacks green fruits, suggests a role for B. bassiana in disease management and demonstrates CBB can disperse the pathogens.

Selection of Beauveria bassiana (Hypocreales: Cordycipitaceae) strains to control Xyleborus affinis (Curculionidae: Scolytinae) females.

BackgroundXyleborus affinis Eichhoff (Coleoptera: Curculionidae) is an ambrosia beetle reported to affect avocado trees (Persea americana Mill.). The use of the entomopathogenic fungus (EPF) Beauveria bassiana (Bals.-Criv.) Vuill. for ambrosia beetle control represents an alternative to insecticides.MethodsThis study was designed in two stages to select B. bassiana strains with potential to control X. affinis females. In the first stage, 19 B. bassiana Mexican strains from EPF collection, isolated from Coleoptera (CHE-CNRCB, http://www.gob.mx/senasica/documentos/coleccion-de-hongos-entomopatogenos), were tested. Analyses included radial growth rate, conidial yield, spore germination, and germ tube length. Results were analysed by Principal Component Analysis (PCA) to identify clusters within favourable growth phenotypes. For the second stage, 10 selected strains were re-analysed for virulence-related metabolic characteristic, including cell wall-bound cuticle-degrading enzymes–Pr1-like proteases and β-N-acetyl glucosaminidases (NAGase) chitinases, conidial hydrophobicity and monopolar germination parameters. A second PCA analysis was run for those virulence parameters analysed, and upon results strains CHE-CNRCB 44, 171, 431 and 485 were selected and tested against X. affinis females. Females were treated with a 1 × 108 conidia mL−1 suspension (recommended rate), using a Potter Tower.ResultsAll strains showed insecticidal activity, inducing up to 58% mortality; about 30% dead beetles developed aerial mycelia (CHE-CNRCB 485) and the fastest mortality rate was t0 = 1.95 (CHE-CNRCB 44).ConclusionSince all selected strains showed virulence against X. affinis females, results indicated the possibility of selecting B. bassiana strains based on multiple metabolic attributes, as a preliminary test to perform bioassays against order-related target insects.

Multigene phylogeny of the family Cordycipitaceae (Hypocreales): new taxa and the new systematic position of the Chinese cordycipitoid fungus Paecilomyces hepiali

The phylogeny and systematics of cordycipitoid fungi have been extensively studied in the last two decades. However, systematic positions of some taxa in the family Cordycipitaceae have not yet been thoroughly resolved. In this study, a new phylogenetic framework of Cordycipitaceae is reconstructed using multigene (nrSSU, nrLSU, tef-1α, rpb1 and rpb2) sequence data with large-scale taxon sampling. In addition, ITS sequence data of species belonging to the Lecanicillium lineage in the family Cordycipitaceae are used to further determine their phylogenetic placements. Based on molecular phylogenetic data together with morphological evidence, two new genera (Flavocillium and Liangia), 16 new species and four new combinations are introduced. In the new genus Flavocillium, one new species F. bifurcatum and three new combinations previously described as Lecanicillium, namely F. acerosium, F. primulinium and F. subprimulinium, are proposed. The genus Liangia is built by the new species Lia. sinensis with Lecanicillium-like asexual morph, isolated from an entomopathogenic fungus Beauveria yunnanensis. Due to the absence of Paecilomyces hepiali, an economically and medically significant fungus, in the earlier phylogenetic analyses, its systematic position has been puzzling in both business and academic communities for a long time. Here, P. hepiali is recharacterized using the holotype material along with seven additional samples. It is assigned to the genus Samsoniella (Cordycipitaceae, Hypocreales) possessing Cordyceps-like sexual morph and Isaria-like asexual morph, and thus a new combination, namely S. hepiali is proposed. An additional nine new species in Samsoniella are described: S. alpina, S. antleroides, S. cardinalis, S. cristata, S. lanmaoa, S. kunmingensis, S. ramosa, S. tortricidae and S. yunnanensis. Four new species in Cordyceps are described: C. chaetoclavata, C. cocoonihabita, C. shuifuensis and C. subtenuipes. Simplicillium yunnanense, isolated from synnemata of Akanthomyces waltergamsii, is described as a new species.

Effects of entomopathogenic nematodes and/or fungus on the red palm weevil, Rhynchophorus ferrugineus (Curculionidae: Coleoptera)

Summary The invasive red palm weevil (RPW) (Rhynchophorus ferrugineus) (Coleoptera: Curculionidae) is one of the most destructive palm pests in the world. More options are needed for its management, including optimised use of microbial entomopathogens (EP). The sub-lethal effects of an entomopathogenic fungus (EPF) Beauveria bassiana (isolate WG-11) (Ascomycota: Hypocreales) (at 1 × 104 spores ml−1) and two entomopathogenic nematode (EPN) species, Heterorhabditis bacteriophora (at 100 infective juveniles (IJ) ml−1) and Steinernema carpocapsae (at 50 IJ ml−1) were evaluated in various combinations against laboratory-reared 3rd, 5th and 8th instar larvae of RPW in bioassays. Individual and combined effects of both EP were observed after the pre-application of B. bassiana fungus at 0-, 1- and 2-week intervals. Combined treatments were tested for antagonistic, additive and synergistic effects. Additive and synergistic effects were observed in B. bassiana/S. carpocapsae and in B. bassiana/H. bacteriophora combined treatments. Early instar larvae of RPW were more susceptible than older instars. Sole and combined EP treatments decreased pupation, subsequent emergence of RPW adults and hatching. Sub-lethal effects of EP were observed in R. ferrugineus following application at the above-mentioned rates to 3rd, 5th and 8th instar larvae, including reduced larval weights, increased larval, pre-pupal and pupal durations, reduced adult weights and life spans. Simultaneous combined applications of B. bassiana/S. carpocapsae and B. bassiana/H. bacteriophora at the above-mentioned rates against last instar (9th) larvae of R. ferrugineus reduced food consumption, frass production and affected weight gains.

Evaluate the Effects of Entomopathogenic Fungi Isolates on Wheat Aphid, Schizaphis graminum (Rondani) (Hemiptera: Aphididae)

Four native isolates of entomopathogenic fungi (EPF) Beauveria bassiana (B1and B2), Metarhizium anisopliae (M1 and M2 ) were isolated and evaluated against wheat aphid, Schizaphis graminum (Rondani). Three concentrations of spores suspension from each of the four fungal isolates (1×106, 1×107 and 1×108conidia) were used against adult aphid (one day old). The results showed that (B1) was the most effective according to LC50. Whereas, when testing the toxicity of crude metabolites of fungal isolates in four concentrations for each isolate, it was found that the highest effective toxin was (M1) followed by (B1), (M2) and (B2). Scanning electron microscope photographs (SEM) showed the mode of action of entomopathogenic fungi and its ability to colonize and how it infects aphid.

Benefits of living underground: the case of parasite release in the antlion Myrmeleon timidus

AbstractThe omnipresence of pathogens makes them a strong selective pressure for most organisms, generating a variety of defensive responses to fight them. One mechanism by which organisms can release this pressure is avoidance of the pathogens in a spatial or temporal context. To date, only a few biological systems provide evidence that habitat selection can favour an escape from pathogens. An abiotic factor that varies across habitats and influences the evolution of host life history is humidity, which correlates positively with pathogen levels in the environment. Entomopathogenic fungi are abundant in soils and are obligate killers that require humidity for host infection. Antlions (Neuroptera: Myrmeleontidae) are typical soil‐dwelling insects that can live several years as larvae, buried in dry and fine substrates where they build their traps. This lifestyle may release them from selective pressure by entomopathogenic fungi. Here, we investigated whether living underground provides protection against the generalist entomopathogenic fungus Beauveria bassiana (Bals.‐Criv.) Vuill. in the antlion Myrmeleon timidus Gerstaecker under low or high humidity in the environment. Individuals that were inoculated with the fungus showed greater survival rates when buried in dry sand compared to individuals that were kept half‐buried or without sand, with similar outcomes across humidity levels. Given that the diversity of antlions is higher in arid environments, this benefit obtained from pit‐building behaviour seems to be a coincidental by‐product of this foraging strategy, which would be particularly beneficial in environments where fungal pathogens are common.

Application of Beauveria bassiana (Bals.) Vuil. (Hypocreales: Cordycipitaceae) in rice seed and its effect on mortality of green leaf hopper, Nephotettix virescens (Distant) (Homoptera: Cicadellidae)

The use of synthetic chemical insecticides in controlling rice pest insects has various negative impacts. Chemical insecticides can stimulate pest resistance, the emergence of secondary pests, killing of useful organisms and natural enemies, and contamination of residues in food, soil and water. Another potential effective control alternative is the use of entomopathogenic fungus Beauveria bassiana (Bals.) Vuil. (Hypocreales: Cordycipitaceae). The effectiveness of B. bassiana application by spraying on plants or pests directly, can decrease due to the influence of high temperatures, low humidity, and exposure to ultra violet light. The study of the application of B. bassiana by treatment of rice seeds was carried out to determine the cumulative mortality of green leaf hopper, which was carried out in two-time periods at the Bioecology Laboratory for Natural Pests and Enemies, Department of Plant Pests and Diseases, Faculty of Agriculture, Hasanuddin University. The first series of studies used B. bassiana collection culture of Bioecology Laboratory, and the second series used the commercially available B. bassiana formulation. Completely Randomized Design (CRD), with each of the 4 treatments and 5 replications was used in this study. The results showed that, coating or soaking rice seeds with entomopathogenic fungi B. bassiana was able to cause mortality to green leafhoppers. Although the mortality is lower than spraying on rice plants or penetrating the body of green leafhoppers, however, with the covering or soaking rice seeds, the mortality of green leafhoppers is significantly higher than control without the application of B. bassiana. This indicates basic potential that requires a study for development of rice seed coating and immersion techniques to increase its effectiveness in controlling green leafhoppers.

Assessment of Lethal, Sublethal, and Transgenerational Effects of Beauveria Bassiana on the Demography of Aedes Albopictus (Culicidae: Diptera).

Dengue fever is one of the most rapidly spreading arthropod-borne diseases. Diurnal vectorial properties of Aedes albopictus contribute to the dispersion of the dengue viruses. Frequent and injudicious use of synthetic insecticides led to the evolution of resistant phenotypes in Ae. albopictus which necessitates the search for an alternative of current control strategies. Developing a long-lasting and environmentally safe tactic based on knowledge of ecology and population dynamics of Ae. albopictus is critical. Therefore, with a view towards biological control and ecology, the effect of entomopathogenic fungi (EPF) Beauveria bassiana on filial and first filial generations of Ae. albopictus were studied. Investigations showed 87.5% adulticidal activity leading to altered fecundity and adult longevity in a filial generation. The lethal (LC50) and sublethal (LC20) concentrations of B. bassiana were applied to filial generation (F0) to study demographic parameters in the first filial generation (F1). Results showed reduced net reproductive rates (Ro) intrinsic rate of increase (r), and mean generation time (T) compared to uninfected controls. Prolonged larval and pupal duration were observed followed by reduced longevity of male and female adults. Fecundity in the first filial generation was significantly changed with the lethal and sublethal concentrations of B. bassiana. Thus, it is concluded that B. bassiana has the potential to play a vital role in integrated mosquito management strategies.

Fluctuating temperatures influence the susceptibility of pest insects to biological control agents

Despite the fact that temperatures fluctuate on a daily basis in the field, the effect of fluctuating temperature on the susceptibility of pest insects to agricultural management tactics are lacking. We thus tested how the development of Spodoptera littoralis and Heliothis virescens (Lepidoptera: Noctuidae) is influenced by exposure to an insecticidal genetically engineered pulverized powder of, Bollgard II cotton producing the Bt proteins Cry1Ac and Cry2Ab, or an entomopathogenic fungus (Beauveria bassiana) under fluctuating temperatures in comparison with constant temperature. When temperature fluctuated symmetrically around 25 °C either in small range (± 5 °C) or in a large range (± 10 °C) on daily basis, development of both lepidopteran species was positively or not influenced in absence of additional stressors. Both species were affected by Bt-cotton when added at low concentrations to the artificial diet, but their reaction to Bt-cotton did not differ between fluctuating temperatures compared to a constant 25 °C. When H. virescens larvae were dipped into spore suspension of B. bassiana, all larvae reared at constant 25 °C died before pupation, while no detrimental effect of the fungus was visible in the fluctuating temperature regimes. In contrast, S. littoralis was not affected by the fungus in any treatment. Since fungal growth was reduced at fluctuating temperatures, this might have affected the infection rate in H. virescens. The results of this study indicate that fluctuating, compared to constant temperatures, can influence the susceptibility of pest insects to biological control agents, while temperature regimes seem to be less important for the efficacy of insecticidal genetically engineered crops.

Improving the efficiency of Beauveria bassiana applications for sustainable management of Plutella xylostella (Lepidoptera: Plutellidae) in West Africa

The effectiveness of the entomopathogenic fungus Beauveria bassiana (Balsamo) Vuillemin isolates Bb11, Bb115, Bb116 and Bb362 against the diamondback moth (DBM), Plutella xylostella (L.) population from Cotonou, Benin, was investigated in the laboratory and on station. In the laboratory, six concentrations, 104, 105, 106, 107, 108 and 109 conidia/ml of each isolate were used to assess B. bassiana virulence. Third instar DBM larvae were inoculated with 2 µl of each isolate’s concentrations by topical application method. Control larvae were inoculated with sterilized Tween 80 solution (0.05%). Compared with other isolates, Bb11 was more virulent against DBM with LD50 value estimated to 4.96 × 106 conidia/ml and the highest rates of cadaver sporulation. The effectiveness of Bb11 against DBM on cabbage was subsequently assessed on station and on farm in Benin and Togo, at a low doses of 53 g/ha once or twice a week and a high dose of 315 g/ha weekly. Compared with unsprayed control and deltamethrin treatments, the dose of 53 g/ha of Bb11 applied twice a week at intervals of 4 days was able to reduce on farm the density of DBM by 83% and 93%, respectively. Also, the marketable cabbage yield obtained on farm with this dose was significantly higher compared with the other treatments, with a 199% and 452% increase in Danyi and Cotonou over the unsprayed control, respectively. These results confirm the better performance of Bb11 over other isolates, and also indicate that the newly investigated application dosage and frequency of Bb11 could be an efficient management option to control DBM in Benin and Togo.