Application Of Entomopathogenic Fungi Research Articles

Susceptibility of immature Telenomus remus, an egg parasitoid of Spodoptera frugiperda (J.E. Smith), to entomopathogenic fungi from South Sumatra, Indonesia

BackgroundThe fall armyworm (FAW) Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) is a newly introduced pest that damages maize production in Indonesia. To control this pest in maize fields, better solution is to use the egg parasitoid, such as Telenomus remus Nixon (Hymenoptera: Scelionidae), as another better option to apply topically entomopathogenic fungi (EPF). Therefore, it is necessary to study the effect of the EPF on the egg parasitoid of T. remus. The objective of this research was to evaluate susceptibility of immature T. remus to the EPFs, Beauveria bassiana, Chaetomium sp., Curvularia lunata, Penicillium citrinum, and Metarhizium anisopliae. The EPFs (1 × 106 conidia mL−1) were sprayed topically on one-day-old mummies (immature T. remus) in post-parasitism periods.ResultsThe results showed that the cumulative percentage of T. remus adult emergence from the mummies treated with EPF on 11 days after treatment ranged 54–100% and was non-significantly different than those of control (untreated with EPF) (90.48%). Therefore, the immature stage of T. remus was not susceptible to the EPF topical application. The EPFs were harmless to the immature stage of T. remus. Percentage of aborted mummies (embryonic death) of T. remus after treated with the EPF was also non-significantly different than those of control. However, the EPFs could significantly affect developmental times of immatures stages of T. remus. The EPF also could shorten the adult longevity of the egg parasitoid.ConclusionsThe immature T. remus is less sensitive to the EPFs; B. bassiana, Chaetomium sp., C. lunata, P. citrinum, and M. anisopliae. It can be considered integrating the EPF with T. remus inundation in maize field. However, it is necessary to limit the topical application of the EPF to avoid negative effects on the adult longevity of the egg parasitoid. Thus, it needed to be further investigated that the application of the endophytic EPFs by inoculating the fungi within the plant tissue could be harmless to the egg parasitoids.

Analysis of the virulence, infection process, and extracellular enzyme activities of Aspergillus nomius against the Asian corn borer, Ostrinia furnacalis guenée (Lepidoptera: Crambidae)

ABSTRACT The control of Ostrinia furnacalis, a major pest of maize in Xinjiang, is challenging owing to the occurrence of resistant individuals. Entomopathogenic fungi (EPF) are natural insect regulators used as substitutes for synthetic chemical insecticides. The fungus Aspergillus nomius is highly pathogenic to O. furnacalis; however, its virulence characteristics have not been identified. This study aimed to analyse the lethal efficacy, mode of infection on the cuticle, and extracellular enzyme activity of A. nomius against O. furnacalis. We found that the mortality and mycosis of O. furnacalis were dose-dependent when exposed to A. nomius and varied at different life stages. The egg-hatching and adult emergence rates decreased with an increase in conidial suspension. The highest mortality (83.33%, 7 d post-infection [DPI]) and mycosis (74.33%, 7 DPI) and the lowest mortality response (8.52 × 103 conidia mL−1) and median lethal time (4.91 d) occurred in the 3rd instar larvae of O. furnacalis. Scanning electron microscopy indicated that numerous conidia germination and infection structure formation may have contributed to the high pathogenicity of A. nomius against O. furnacalis. There were significant correlations between O. furnacalis mortality and the activities of extracellular protease, lipase, and chitinase of A. nomius. This study revealed the infection process of the highly pathogenic A. nomius against O. furnacalis, providing a theoretical basis and reference for strain improvement and field application of EPF.

Combined effect of entomopathogenic nematode, Heterorhabditis indica with entomopathogenic fungi, Metarhizium pinghaense and M. robertsii against the obscure mealybug, Pseudococcus viburni

In this study, we evaluated the combined application of entomopathogenic nematodes (EPN), Heterorhabditis indica, with entomopathogenic fungi (EPF), Metarhizium pinghaense or M. robertsii, against Pseudococcus viburni (Signoret), in laboratory trials. Three EPF-EPN combinations were used, where P. viburni was either exposed to the EPF and EPN isolates simultaneously or sequentially, at different time intervals. The combined application of H. indica with each of the two EPF isolates resulted in higher mortality of P. viburni, under laboratory conditions, relative to when applied individually. With sequential application, the H. indica and M. robertsii combination was shown to be more effective, resulting in 85 ± 3.1% and 88.8 ± 3.9% mortality after four and three days, respectively. Heterorhabditis indica combined with M. pinghaense was more effective for simultaneous application of the entomopathogens, resulting in 95 ± 6.5% mortality after five days. Insect mortality was mostly due to EPN infection. The single application of H. indica against P. viburni resulted in 76.3 ± 2.9% after 48 h, while M. pinghaense and M. robertsii resulted in 73.8 ± 7.9% and 82.5 ± 3.3% respectively, after a week. Interactions between H. indica and the two EPF isolates were shown to have an additive effect, when used simultaneously and sequentially. The results from the study indicate that the combined application of EPF and EPN could potentially be used as an alternative strategy for management of P. viburni in fruit production areas.

Susceptibility of Egg Stadia of Walang Sangit (Leptocorisa acuta thunb.) To Entomopathogenic Fungi Beauveria Bassiana (bals.) Vuill. and Metarhizium spp. From various rhizosphere

This study aims to determine the pathogenicity of the entomopathogenic fungi Beauveria bassiana (Bals.) Vuill and Metarhizium spp. isolated from various locations. against Walang Sangit (Leptocorisa acuta Thunb.) eggs. In this experiment, the egg group of Leptocorisa acuta and 5 isolates of entomopathogenic fungi were used, namely Bb5a, Bb4b, Bb1e, Met3b, and Met1a. Application of entomopathogenic fungi was carried out by spraying entomopathogenic fungi according to the treatment using hand sprayer in each treatment as much as 2 ml. Conidial concentration of each isolate used for testing was 108 conidia/ml. The variables observed were L. acuta egg mortality, 1st instar L. acuta nymph mortality, and length of 1st instar L. acuta nymph death. Observational data were analyzed statistically by Analysis of Variance (Anova), if it had a significant effect then it was continued with the DNMRT test at 5% level. The results showed that isolates of entomopathogenic fungi Bb4b and Met3b had a significant effect on L. acuta egg mortality, 1 L instar nymph mortality .acuta, and time of death of 1st instar nymph L.acuta.

Integrasi komponen pengendalian hama penggerek ubi jalar (Cylas formicarius Fab.) (Coleoptera: Curculionidae)

Sweetpotato weevil Cylas formicarius Fabricius is major obstacle in increasing of sweet potato production in various countries. Tuber damage due to C. formicarius causes yield loss up to 80%. This study aims to examine the integration control of C. formicarius in entisol, each control combination was composed of various components. The control integration was composed of various components of synthetic insecticide, application of entomopathogenic fungus Beauveria bassiana, weeding, turning of the stems, heap up, and cover mounds using plastic mulch. The study used a randomized block design, each treatment was repeated five times. The research was conducted at Kendalpayak experimental station from May to September 2017. The result showed that P5 with B. bassiana application five times, addition of 3 t/ha organic fertilizer, cover mounds by plastic mulch was most effective in suppressing of C. formicarius in endemic entisol. The tuber weight at control combination (P5) was reached 23 t/ha or 56% higher than control combination of farmer cultivation (P1) was only 10 t/ha. The entisol land with an alluvial structure cracks easily during in the dry season, so that adults to penetrate the base of tubers and lay their eggs. The results of this study indicate that control combination of P5 can be recommended as a innovation control technology of C. formicarius in endemic entisol.

Control of Fusarium and nematodes by entomopathogenic fungi for organic production of Zingiber officinale.

Ginger (genus Zingiber) is widely used as a spice and a medicinal herb worldwide and is the major ingredient of traditional local drinks such as jamu in Southeast Asia. Because ginger is frequently consumed, there is an increasing interest in organic ginger production without the use of synthetic agrochemicals. Recent studies have reported that certain kinds of entomopathogenic fungi (EPF) can establish endophytic- or mycorrhiza-like relationships with plants, thereby promoting plant growth and health, in addition to their typical role in crop protection as biological control agents. In this study, we explored the possibility of non-entomopathogenic effects of EPF Beauveria bassiana and Cordyceps fumosorosea on ginger plants (Zingiber officinale) via antagonism with Fusarium oxysporum or the parasitic nematode Meloidogyne incognita. The two EPF negatively affected the growth of F. oxysporum and survival of M. incognita in vitro. The application of EPF did not have any negative effect on the growth of ginger plants. Soil chemical properties were not different between the plots with or without EPF application, while the diversity of soil bacteria was observed to increase on application of EPF. At least C. fumosorosea appeared to persist in soil during the period of ginger cultivation. Thus, these EPF are potentially useful tools for producing chemical-free ginger.

The Toxins of Beauveria bassiana and the Strategies to Improve Their Virulence to Insects.

The long-term and excessive usage of pesticides is an enormous burden on the environment, which also increases pest resistance. To overcome this problem, research and application of entomopathogenic fungi, which are both environmentally friendly and cause lower resistance, have gained great momentum. Entomopathogenic fungi have a wide range of prospects. Apart from Bacillus thuringiensis, Beauveria bassiana is the most studied biopesticide. After invading insect hosts, B. bassiana produces a variety of toxins, which are secondary metabolites such as beauvericin, bassianin, bassianolide, beauverolides, tenellin, oosporein, and oxalic acid. These toxins help B. bassiana to parasitize and kill the hosts. This review unequivocally considers beauveria toxins highly promising and summarizes their attack mechanism(s) on the host insect immune system. Genetic engineering strategies to improve toxin principles, genes, or virulent molecules of B. bassiana have also been discussed. Lastly, we discuss the future perspective of Beauveria toxin research, including newly discovered toxins.

Overview and future research needs for development of effective biocontrol strategies for management of Bactrocera dorsalis Hendel (Diptera: Tephritidae) in sub-Saharan Africa.

Infestation of fruits by native and invasive fruit flies causes significant economic losses. In most cases, incidence of 'regulated' dangerous fruit flies in orchards results in restrictions on export of fruits from such places to international markets. Unfortunately, use of insecticides applied on foliage and fruits does not kill the fruit-to-soil stages of fruit flies. However, diverse biological control agents (BCAs) do so. Thus, prevalence of native and invasive fruit flies in orchards will require that a combination of BCAs is included in integrated pest management (IPM) programmes. In the case of Bactrocera dorsalis Hendel and other economically important fruit flies found in sub-Saharan Africa (SSA), use of classical biocontrol approach involves concomitant releases of two exotic parasitoids (Fopius arisanus Sonan and Diachasmimorpha longicaudata Ashmead). These non-native wasps may have complemented the indigenous parasitoids in combination with application of entomopathogenic fungi (EPFs) and conservation of predatory ants (Oecophylla longinoda Latreille, with O. smaragdina) in fruit fly IPM plans. Consequently, some levels of decline in fruit infestation have been observed. Although interspecific interactions between BCAs against several insect pests have produced varying results, including threatening the survival of other BCAs, the prevalence of B. dorsalis in orchards across SSA requires further research to investigate effects of coalescing biocontrol approaches in IPM strategies. Therefore, future research into combining parasitoids, EPFs and entomopathogenic nematodes, in addition to conservation of predatory ants (O. longinoda, O. smaragdina and others) in IPM plans may improve the effectiveness of currently used strategies for the management of fruit-infesting tephritids. © 2021 Society of Chemical Industry.

Whitefly-induced tomato volatiles enhance the virulence of Lecanicillium lecanii

Entomopathogenic fungi (EPF) are a group of microorganisms that have potential for replacing synthetic chemical pesticides. However, EPF virulence is often insufficient, and therefore adoption of EPF biopesticides has been relatively limited. Previous studies have shown that herbivore-induced plant volatiles (HIPVs) promoted the virulence of Lecanicillium lecanii, and that extracellular proteases and chitinases are important virulence factors of entomopathogenic fungi. We therefore put forward the hypothesis that HIPVs promote L. lecanii virulence by inducing extracellular protease or/and chitinase activity. Lecanicillium lecanii was treated with tomato HIPVs induced by various numbers/densities of Bemisia tabaci, the effect of HIPVs on L. lecanii virulence and activities of virulence-related enzymes (extracellular proteases and chitinases) was analyzed. Changes in enzyme activities were confirmed by measuring the variations in Pr1 and Chit II genes expression of virulence-related enzymes under the influence of HIPVs. Finally, the correlation between virulence and virulence-related enzymes or genes was analyzed to explore the mechanism of promoting HIPVs in L. lecanii virulence enhancement. The results showed that volatiles produced by the tomato plants induced by 50 B. tabaci adults (50-HIPVs) significantly enhanced the virulence of L. lecanii. When exposed to both 50-HIPVs and L. lecanii, the mortality rate of B. tabaci reached 79.0% within 7 days compared to 28.87% in the control group. Additionally, 50-HIPVs significantly promoted the activity of chitinase and the relative expression of Chit II genes, which consequently increased by 62.74% and 48.55%, respectively. However, each group of HIPVs had no promoting effect on extracellular protease and Pr1 gene expression. Correlation analysis results showed that the virulence of L. lecanii is significantly correlated with the activity of chitinase and relative expression of Chit II genes. Thus, HIPVs induced virulence of L. lecanii by increasing chitinase activity. This study demonstrates important methods to enhance the virulence of L. lecanii. Moreover, from the perspective of chemical ecology, the findings provide theoretical support for field application of EPF, and also reveal the impact of HIPVs on EPF from a biochemical perspective.

Seed inoculations with entomopathogenic fungi affect aphid populations coinciding with modulation of plant secondary metabolite profiles across plant families.

Entomopathogenic fungi (EPF) can display a plant-associated lifestyle as endophytes. Seed application of EPF can affect insect herbivory above ground, but the mechanisms behind this are not documented. Here we applied three EPF isolates, Beauveria bassiana, Metarhizium brunneum and M.robertsii, as seed inoculation of wheat and bean, and evaluated the effects on population growth of aphids, Rhopalosiphum padi and Aphis fabae, respectively. In wheat and bean leaves, we quantified benzoxazinoids and flavonoids, respectively, in response to EPF inoculation and aphid infestation to elucidate the role of specific plant secondary metabolites (PSMs) in plant-fungus-herbivore interactions. Inoculations of wheat and bean with M.robertsii and B.bassiana reduced aphid populations compared with control treatments, whereas M.brunneum unexpectedly increased the populations of both aphids. Concentrations of the majority of PSMs were differentially altered in EPF-treated plants infested with aphids. Changes in aphid numbers were associated with PSMs regulation rather than EPF endophytic colonisation capacity. This study links the effects of EPF seed inoculations against aphids with unique PSM accumulation patterns in planta. The understanding of PSM regulation in tri-trophic interactions is important for the future development of EPF for pest management.

Combined effect of entomopathogenic fungi and Steinernema yirgalemense against the banded fruit weevil, Phlyctinus callosus (Coleoptera: Curculionidae)

ABSTRACT Phlyctinus callosus (Schönherr) (Coleoptera: Curculionidae), or the banded fruit weevil (BFW), causes damage to the fruits, leaves and roots of deciduous fruits and grapevines in the Western Cape province. The control of the BFW can be improved by means of combining entomopathogenic fungi (EPF) and entomopathogenic nematodes (EPNs). The combination of commercial isolates of Beauveria bassiana (Bb1), B. bassiana (Bb2), Metarhizium anisopliae (Ma1) and a South African isolate M. anisopliae (MaEA2), with Steinernema yirgalemense against BFW adults and larvae were evaluated in laboratory trials. Four treatment regimens were used where BFW were exposed to the EPF and the EPN separately, and to a combination of EPF and S. yirgalemense either immediately, 1 week or 2 weeks apart. The combined application of the different EPF isolates with S. yirgalemense resulted in higher mortality of BFW in the laboratory. With the application of S. yirgalemense 7 or 14 days after application of Bb2 and Bb1, 100% mortality for both larvae and adults, was obtained. Synergy was noted with Bb1, Bb2, Ma1 and MaEA2 when each was combined with S. yirgalemense, when applied 7 or 14 days after application of the EPF. Interactions showed that the EPF and S. yirgalemense have an additive effect when applied simultaneously, and a synergistic effect was obtained when applied 7 or 14 days after the application of the different EPF. The results indicate that the combination of EPF and an EPN show potential as an economically viable control strategy.

Research and Application of Entomopathogenic Fungi as Pest Management Option: A Review

Entomopathogenic fungi are myco-biocontrol, potentially the most versatile biological control agents with a wide host range and are an environmentally sound and effective means of reducing insect-pests. The use of microbial control agents particularly entomopathogenic fungi, have been investigated for the control of a wide range of orchard and field crop pests and are a widespread component of most terrestrial ecosystems. Entomopathogenic fungi are a major component of integrated pest management techniques as biological control agents against insect pests and other arthropods in horticulture, forestry and agriculture and are found in the divisions of Zygomycota, Ascomycota, Deuteromycota, Chytridiomycota and Oomycota, which were previously classified within fungi. Insect control using entomopathogenic fungi is achieved when sufficient infective propagules, conidia contact a susceptible host and conditions are suitable for a lethal mycosis to develop. A wide range of fungi occur in the soil environment and they have various ecological functions. Most of these fungi, along with a range of bacteria, can grow on artificial media in vitro . Several methods have been used to describe the variation within a species of entomopathogenic and mycoparasitic fungi including morphological characteristics of spores and colonies, extracellular protein profiles, pathogenecity, growth and nutrient requirements. Furthermore, immune taxonomic and chemotaxonomic methods have been used, though only with limited success. Taxonomic procedures are becoming more and more complex and it is generally accepted that some forms of molecular identification techniques are needed in addition to the traditional morphological characteristics formally used to classify fungal species. During the last four decades, over 80 companies worldwide have developed 171 mycoinsecticides and myco-acaricides. Use of mycoinsecticdes is likely to rise if research is focus on; improving its performance under challenging environmental conditions, formulations that will increase persistence, longer shelf life, ease of application, pathogen virulence and wider spectrum of action. Keywords: Eco-friendliness, fungi , insect pest , myco-acaricides, mycoinsecticdes DOI: 10.7176/JEES/10-3-03 Publication date: March 31 st 2020

Endophytic Entomopathogenic Fungi: A Valuable Biological Control Tool against Plant Pests

Among the non-chemical insect control methods, biological control is one of the most effective human and environmentally friendly alternatives. One of the main biological control methods is the application of entomopathogenic fungi (EPF). Today, biological crop protection with EPF plays a key role in projects for the sustainable management of insect pests. EPF have several advantages over conventional insecticides, including cost-effectiveness, high yield, absence of harmful side-effects for beneficial organisms, fewer chemical residues in the environment and increased biodiversity in ecosystems. Apart from direct application as contact bioinsecticides, EPF are able to colonize plants as endophytes acting not only as pest and disease control agents but also as plant growth promoters. The present paper presents an outline of the biocontrol potential of several EPF, which could be harnessed for the development of new integrated pest Management (IPM) strategies. Emphasis is given on benefits of endophytic EPF, on issues for practical application and in fields in need of further research. Our findings are discussed in the context of highlighting the value of entomopathogenic fungal endophytes as an integral part of pest management programs for the optimization of crop production.

Pathogenicity of Three Different Entomopathogenic Fungi, Metarhizium anisopliae IRAN 2252, Nomuraea rileyi IRAN 1020C and Paecilomyces tenuipes IRAN 1026C Against the Potato Tuber Moth, Phthorimaea operculella Zeller (Lepidoptera: Gelechiidae)

The potato tuber moth (PTM), Phthorimaea operculella Zeller, is a prominent pest of potato in many potato cultivation areas such as Iran. Since the potato is one of the most important sources of human food, non-chemical control of the pest is essential. Application of entomopathogenic fungi is a low-risk alternative method to synthetic chemical insecticides. Therefore, we examined the efficacy of Metarhizium anisopliae IRAN 2252, Nomuraea rileyi IRAN 1020C and Paecilomyces tenuipes IRAN 1026C against neonate larvae and eggs of P. operculella under laboratory (26 ± 1 °C, 60 ± 5% relative humidity (RH) and a photoperiod of 16-h light: 8-h dark (L:D)) and greenhouse (26 ± 2 °C, 55 ± 5% RH and a photoperiod of 14-h L: 10-h D) conditions. Probit analysis of toxicity showed that N. rileyi was the most effective fungus against neonate larval penetration into potato tuber with a lethal concentration resulting in 50% mortality (LC50) equivalent to 1 × 103 conidia/ml. Moreover, adult emergence and first generation progenies of PTM were reduced when the LC25 value of each fungus was used. N. rileyi showed the highest toxicity against neonate larvae, pupae and adult emergence of PTM under laboratory and greenhouse conditions with LC50 values equivalent to 2.6 × 102 and 4.2 × 103 conidia/ml, respectively. N. rileyi caused significant egg hatching reduction (LC50 = 4.8 × 104). The results indicated that these entomopathogenic fungi had ovicidal and larvicidal activities against P. operculella and can be used in integrated pest management (IPM) programmes.

Bahasa Indonesia

Spiders are the main predators in paddy ecosystem. Application of entomopathogenic fungus, such as Beauveria bassiana (Balsamo) is not expected to have any negative effect on spiders in the paddy field. This research was aimed to compare species composition, abundance, and species richness of spiders in ratoon paddy. The research was done on three hectares of rice fields that were treated with the following treatment, (i) 2 L/ha/application of liquid B. bassiana, (ii) 2 L/ha/application compost extract (without liquid B. bassiana), and (iii) a combination of liquid B. bassiana and compost extract with each using the same 2L/ha/application dose. The result of this research showed that B. bassiana bioinsecticide application did not affect the abundance and species richness of spiders in ratoon paddy. The treatments did not significantly affect species richness and abundance of the canopy-inhabiting spiders. The species richness and abundance of the soil-dwelling spiders on the paddy field applied by the bioinsecticide was not different from those without the bioinsecticide. The treatments did not effect species composition of the canopy-inhabiting and the soil-dwelling spiders. Application of B. bassiana bioinsecticide was not harmful for the spiders in the rice field.

Effect of Beauveria bassiana and Metarhizium anisopliae on the Trialeurodes vaporariorum-Encarsia formosa system

The virulence of three strains of Beauveria bassiana and one of Metarhizium anisopliae was tested against Trialeurodes vaporariorum and its parasitoid Encarsia formosa in laboratory assays. These strains were previously selected for their virulence against Galleria mellonella and Tenebrio molitor. The commercial B. bassiana strain ATCC 74040, both as pure fungal culture and formulated myco-insecticide (Naturalis), was included in the assays as positive control. First, the entomopathogenic fungal strains were tested for their virulence against T. vaporariorum nymphs on tomato leaf disks. Then, the E. formosa development was evaluated under treatment with the entomopathogenic fungal strains at five different time points from the parasitization of T. vaporariorum nymphs. The virulence of our entomopathogenic fungal strains was superior to that of ATCC 74040, although not significantly, resulting in a cumulative mortality (CM) of T. vaporariorum nymphs 7 days after inoculation (DAI) greater than 86 %. Our M. anisopliae strain CIST8 was the most effective (96.6 % CM 7 DAI), even superior to the myco-insecticide Naturalis (94.2 %), which was more effective than the ATCC 74040 pure strain (85.6 %). The entomopathogenic fungal strains, and especially Naturalis, negatively affected E. formosa development and its parasitization activity of T. vaporariorum nymphs. This effect was more pronounced when the fungal strains were applied before parasitization. Results suggest that the application of entomopathogenic fungi is incompatible with E. formosa release on crops.

Efficiency of commercial entomopathogenic fungal species against different members of the genus Otiorhynchus (Coleoptera: Curculionidae) under laboratory and semi-field conditions

The application of entomopathogenic fungi against weevils of the genus Otiorhynchus spp. might represent an environmentally friendly management option for biological control of these insects, which have recently increased in their importance as pests in a variety of horticultural plants. As only little information is available on the susceptibility of different weevils of this genus towards various fungal species, laboratory experiments were conducted to evaluate the control potential of three different commercially available entomopathogenic fungi (Beauveria bassiana, Isaria fumosorosea, Metarhizium anisopliae) against adults of O. sulcatus, O. raucus, O. dieckmanni, O. rugosostriatus and O. crataegi. Mortality rates were dependent on fungal and weevil species, respectively. Application of Naturalis® containing B. bassiana as the active ingredient caused a significantly higher mortality rate than evident in control groups in four of the five Otiorhynchus species assessed. Adults of O. rugosostriatus were apparently not susceptible to any of the fungi tested. Efficacy of a single application of Naturalis® against adult O. sulcatus was also assessed in three independent semi-field experiments. Weevils got infected during the first 14 days after application, but mortality rates did not substantially increase until 2 months after application. Even 6 months after application, mortality of weevils was caused by the respective applied B. bassiana strain, which was confirmed via an amplification of isolate-specific microsatellite markers. Thus, a single application of a B. bassiana-based product in the field could have long-term effects on population densities of respective weevils.

022 Manipulation of the Greenhouse Microclimate to Improve the Efficacy of Entomopathogens for Control of Greenhouse Pests

Application of entomopathogenic fungi by inundative releases has been attempted for control of a wide range of insect pests, with generally poor results. This is largely because entomopathogens are often treated as direct substitutes for chemical insecticides and applied without an adequate knowledge of their interactions with the local environment. Humidity of greater than 90% RH has long been regarded as the a critical condition for germination and infection by the spores. With both temperature and humidity controlled, greenhouse crops offer an excellent potential for pest control using entomopathogens. The long-term maintenance of >90% RH, however, is not standard practice in greenhouse production. This study explored the possibility of improving the efficacy of the fungi by temporarily changing greenhouse humidity without adversely affecting crop growth. The study included laboratory and greenhouse trials. In laboratory trials, four humidity levels of 75%, 80%, 89%, and 97.5% RH were evaluated over a 48-h period. Three commercial products of Beauveria bassiana were evaluated (Naturalis-O, Botanigard 22 WP, and Botanigard ES). Greenhouse pests of green peach aphid, melon aphid, western flower thrips, whitefly, and two-spotted spider mite were used as target insects. The infection rate of B. bassiana was found to increase when the sprayed adult insects were exposed to higher humidity levels with the maximum infection obtained at 97.5% RH. Percent infection and difference between humidity levels, however, were formulation- and host-dependent. The highest overall control efficacy was obtained by using Botanigard ES. Botanigard ES was highly effective to adult green peach aphid, melon aphid, and greenhouse whitefly at high humidities. Effects of B. bassiana against biological control agents for greenhouse vegetable crops were also evaluated. Greenhouse trials were conducted in two adjacent greenhouse compartment with high and low humidity conditions for 48 h, respectively, for selected pest insects to valid laboratory results.