Increased Phenoloxidase Activity Constitutes the Main Defense Strategy of Trichoplusia ni Larvae against Fungal Entomopathogenic Infections.

The cabbage looper Trichoplusia ni is an important agricultural pest worldwide and is frequently used as a model organism for assessing entomopathogenic fungi virulence, though few studies have measured the host response repertoire to fungal biocontrol agents. Here, we quantified the immune response of T. ni larvae following exposure to two entomopathogenic fungal species: Beauveria bassiana and Cordyceps javanica. Results from our study demonstrate that T. ni larvae exposed to fungal entomopathogens had higher total phenoloxidase activity compared to controls, indicating that the melanization cascade is one of the main immune components driving defense against fungal infection and contrasting observations from other insect-fungi interaction studies. We also observed differences in host response depending on the species of entomopathogenic fungi, with significantly higher induction observed during infections with B. bassiana than with C. javanica. Larvae exposed to B. bassiana had an increased expression of genes involved in prophenoloxidase response and the Imd, JNK, and Jak/STAT immune signaling pathways. Our results indicate a notable absence of Toll pathway-related responses, further contrasting results to other insect-fungi pathosystems. Important differences were also observed in the induction of antimicrobial effectors, with B. bassiana infections eliciting three antimicrobial effectors (lysozyme, gloverin, and cecropin), while C. javanica only induced cecropin expression. These results provide insight into the host response strategies employed by T. ni for protection against entomopathogenic fungi and increase our understanding of insect-fungal entomopathogen interactions, aiding in the design of more effective microbial control strategies for this important agricultural pest.

Post-Application Field Persistence and Efficacy of Cordyceps javanica against Bemisia tabaci.

Previously, Cordyceps javanica Wf GA17, a causing agent of whitefly epizootics in southern Georgia, demonstrated superior temperature tolerance and higher virulence against the whitefly Bemisia tabaci than commercial strains in the laboratory. The post-application persistence and efficacy of this fungus against B. tabaci were compared with that of the commercially available C. javanica Apopka97 strain over a two-year field study in cotton and vegetable crops. When blastospores of both strains were applied alone, whitefly populations were not effectively suppressed. Thus, JMS stylet oil was added to fungal treatments for enhancing efficacy and persistence. For 0-day samples, all fungal treatments caused similar but significant levels of immature mortality regardless of fungal strain, propagule form (conidia vs. blastospores), and application method (alone or mixed with JMS). In follow-up samplings, Wf GA17 blastospores + JMS achieved higher control levels than other treatments in some trials, but the efficacy did not last long. The JMS oil alone caused significant mortality and suppressed whiteflies. Over 90% of spores lost viability 24 h after treatment in all fungal treatments. Across evaluation times, there was no difference between the two fungal strains (conidia or blastospores, alone or combined with JMS), but conidia persisted better than blastospores for both strains. Overall, the field persistence and efficacy of C. javanica did not last long; therefore, improved delivery methods and formulations are needed for enhancement.

Potential Biocontrol Agents of Corn Tar Spot Disease Isolated from Overwintered Phyllachora maydis Stromata.

Tar spot disease in corn, caused by Phyllachora maydis, can reduce grain yield by limiting the total photosynthetic area in leaves. Stromata of P. maydis are long-term survival structures that can germinate and release spores in a gelatinous matrix in the spring, which are thought to serve as inoculum in newly planted fields. In this study, overwintered stromata in corn leaves were collected in Central Illinois, surface sterilized, and caged on water agar medium. Fungi and bacteria were collected from the surface of stromata that did not germinate and showed microbial growth. Twenty-two Alternaria isolates and three Cladosporium isolates were collected. Eighteen bacteria, most frequently Pseudomonas and Pantoea species, were also isolated. Spores of Alternaria, Cladosporium, and Gliocladium catenulatum (formulated as a commercial biofungicide) reduced the number of stromata that germinated compared to control untreated stromata. These data suggest that fungi collected from overwintered tar spot stromata can serve as biological control organisms against tar spot disease.

Bioactivity of brassica seed meals and its compounds as ecofriendly larvicides against mosquitoes.

Strategic, sustainable, and ecofriendly alternatives to chemical pesticides are needed to effectively control mosquitoes and reduce the incidence of their vectored diseases. We evaluated several Brassicaceae (mustard family) seed meals as sources of plant derived isothiocyanates produced from the enzymatic hydrolysis of biologically inactive glucosinolates for the control of Aedes aegypti (L., 1762). Five defatted seed meals (Brassica juncea (L) Czern., 1859, Lepidium sativum L., 1753, Sinapis alba L., 1753, Thlaspi arvense L., 1753, and Thlaspi arvense-heat inactivated and three major chemical products of enzymatic degradation (allyl isothiocyanate, benzyl isothiocyanate and 4-hydroxybenzyl isothiocyanate) were assayed to determine toxicity (LC50) to Ae. aegypti larvae. All seed meals except the heat inactivated T. arvense were toxic to mosquito larvae. L. sativum seed meal was the most toxic treatment to larvae (LC50 = 0.04 g/120 mL dH2O) at the 24-h exposure. At the 72-h evaluation, the LC50 values for B. juncea, S. alba and T. arvense seed meals were 0.05, 0.08 and 0.1 g/120 mL dH2O, respectively. Synthetic benzyl isothiocyanate was more toxic to larvae 24-h post treatment (LC50 = 5.29 ppm) compared with allyl isothiocyanate (LC50 = 19.35 ppm) and 4-hydroxybenzyl isothiocyanate (LC50 = 55.41 ppm). These results were consistent with the higher performance of the benzyl isothiocyanate producing L. sativum seed meal. Isothiocyanates produced from seed meals were more effective than the pure chemical compounds, based on calculated LC50 rates. Using seed meal may provide an effective method of delivery for mosquito control. This is the first report evaluating the efficacy of five Brassicaceae seed meals and their major chemical constituent against mosquito larvae and demonstrates how natural compounds from Brassicaceae seed meals can serve as a promising ecofriendly larvicides to control mosquitoes.

Comparing Production and Efficacy of Cordyceps javanica With Cordyceps fumosorosea.

A newly discovered entomopathogenic fungus Cordyceps javanica (Friedrichs & Bally) Samson & Hywel-Jones (Hypocreales: Cordycipitaceae) strain Wf GA17 was compared with the commercial Cordyceps fumosorosea Wize (Hypocreales: Cordycipitaceae) Apopka 97 strain for liquid-culture production, formulation, insecticidal efficacy, and storage stability under laboratory conditions. We compared culture media with carbon:nitrogen (C:N) ratios of 10:1, 30:1, and 50:1 for these two isolates. A third strain, C. fumosorosea strain ARSEF 3581, had previously been optimized for liquid-culture production of blastospores at 10:1 C:N served as an added control. These seven cultures were processed by spray drying with skim milk powder, stored at 25oC to evaluate storage stability, and assayed for insecticidal activity against Trichoplusia ni (Hübner) (Lepidoptera: Noctuidae) neonates. Final blastospore concentrations were not significantly different among cultures, ranging from 4.47 to 9.88 × 108 spores/ml. Fungal biomass decreased and final glucose concentrations increased with increasing C:N ratios, indicating better fungal growth with higher nitrogen concentrations. Product yields from the spray dryer (grams per liter culture) increased with increased C:N ratios while spore concentrations decreased, ranging from 2.27 to 7.17 × 109 spores/g. There were no significant differences for insecticidal efficacy among the seven treatments. Spores produced in 10:1 C:N ratio media retained viability longer than spores produced in other media. Cost of ingredients decreased with increasing C:N ratios, such that the 30:1 media may yield the most economical product. The raw material cost needed for application was 1.4× greater for Wf GA17 compared with Apopka 97, a difference that could be erased by optimization of culture conditions.

Repellency and toxicity of a CO2-derived cedarwood oil on hard tick species (Ixodidae).

The repellency and toxicity of a CO2-derived cedarwood oil (CWO) was evaluated against actively questing unfed nymphs of four species of hard ticks: Amblyomma americanum (L.), Dermacentor variabilis (Say), Ixodes scapularis Say, and Rhipicephalus sanguineus (Latreille). Using a vertical climb bioassay for repellency, nymphs of these species avoided a CWO-treated filter paper in proportional responses to treatment concentrations. At 60 min of exposure, I. scapularis nymphs were most sensitive with 50% repellency concentration (RC50) of 19.8 µg cm-2, compared with RC50 of 30.8, 83.8 and 89.6 µg cm-2 for R. sanguineus, D. variabilis and A. americanum, respectively. Bioassays determined the lethal concentration for 50% (LC50) and 90% (LC90) mortality of nymphs exposed to CWO in treated vials after 24- and 48-h exposure. After 24 h exposure, the LC50 values were 1.25, 3.45 and 1.42 µg cm-2 and LC90 values were 2.39, 7.59 and 4.14 µg cm-2 for D. variabilis, I. scapularis and R. sanguineus, respectively, but had minimal effect on A. americanum. After 48 h exposure, the LC50 values were 4.14, 0.78, 0.79 and 0.52 µg cm-2, and LC90 values were 8.06, 1.48, 1.54 and 1.22 µg cm-2 for A. americanum, D. variabilis, I. scapularis and R. sanguineus, respectively. The repellency of CWO on tick species decreased with time. The repellency and toxicity bioassays demonstrated concentration-dependent responses of tick nymphs to the oil, indicating the potential of the CO2-derived cedarwood oil be developed as an eco-friendly repellent and/or acaricide.

Active and Covert Infections of Cricket Iridovirus and Acheta domesticus Densovirus in Reared Gryllodes sigillatus Crickets.

Interest in developing food, feed, and other useful products from farmed insects has gained remarkable momentum in the past decade. Crickets are an especially popular group of farmed insects due to their nutritional quality, ease of rearing, and utility. However, production of crickets as an emerging commodity has been severely impacted by entomopathogenic infections, about which we know little. Here, we identified and characterized an unknown entomopathogen causing mass mortality in a lab-reared population of Gryllodes sigillatus crickets, a species used as an alternative to the popular Acheta domesticus due to its claimed tolerance to prevalent entomopathogenic viruses. Microdissection of sick and healthy crickets coupled with metagenomics-based identification and real-time qPCR viral quantification indicated high levels of cricket iridovirus (CrIV) in a symptomatic population, and evidence of covert CrIV infections in a healthy population. Our study also identified covert infections of Acheta domesticus densovirus (AdDNV) in both populations of G. sigillatus. These results add to the foundational research needed to better understand the pathology of mass-reared insects and ultimately develop the prevention, mitigation, and intervention strategies needed for economical production of insects as a commodity.

Emergence of Walnut Husk Maggot Adults in Central Illinois and Potential for Control with Metarhizium brunneum.

The walnut husk maggot, Rhagoletis sauvis (Loew) (Diptera: Tephritidae), causes damage to walnuts when maggots feed inside the husk. September applications of the entomopathogenic fungi Metarhizium brunneum F52 as microsclerotia laced granules to the soil in Illinois were evaluated for pest control based on adult emergence during the following summer. Over 3 yr in central Illinois, adult emergence began near 1 July, peaked before 23 July, and emergence extended as late as 23 August. One summer application of fungus (30 June) when pupae were present, did not reduce fly emergence. Of two September applications that targeted maggots as they move to the soil to pupate, one significantly reduced the number of flies emerging from treated plots when compared with untreated plots for one 7-d sample collected 29 July 2020. Emergence trap data show a defined peak adult emergence in July for central Illinois while September applications of granules containing Metarhizium brunneum (Petch) (Hypocreales: Clavicipitaceae) show shows potential to reduced subsequent fly emergence.

Environmental Tolerance of Entomopathogenic Fungi: A New Strain of Cordyceps javanica Isolated from a Whitefly Epizootic Versus Commercial Fungal Strains.

A new strain of Cordyceps javanica (wf GA17) was observed causing widespread epizootics among whiteflies in Southern Georgia in 2017. The tolerance of conidia to environmental factors including variable temperature and ultraviolet (UV) light was compared between this strain and three commercial strains of entomopathogenic fungi (Metarhizium brunneum F52, Cordyceps fumosorosea Apopka97, and Beauveria bassiana GHA). Under 10-30 °C, C. javanica wf GA17 responded similarly to other fungi, with the highest virulence against Galleria mellonella at 25 °C, followed by 20, 30, and 15 °C; lowest virulence was observed at 10 °C. At 35 °C and 40 °C, C. javanica wf GA17 had lower tolerance than M. brunneum F52 and B. bassiana GHA, but was superior to C. fumosorosea Apopka97 in conidia viability and post-treatment virulence. After exposure to -20 °C for 56 d, C. javanica wf GA17 exhibited lower germination than M. brunneum F52 and lower virulence than M. brunneum F52 and B. bassiana GHA, but higher germination and virulence than C. fumosorosea Apopka97. Following exposure to strong UV light, viability and virulence of all fungi were reduced with increasing exposure periods. Increased environmental tolerance of C. javanica wf GA17 over C. fumosorosea Apopka97 suggests that the new strain could have applicability for commercial pest management.

Optimizing Application Rates of Metarhizium brunneum (Hypocreales: Clavicipitaceae) Microsclerotia for Infecting the Invasive Asian Longhorned Beetle (Coleoptera: Cerambycidae).

The Asian longhorned beetle (Anoplophora glabripennis [Motschulsky]) is an invasive wood-boring beetle that threatens urban trees and forests in North America and Europe. The entomopathogenic fungus Metarhizium brunneum Petch strain F52 can infect and kill A. glabripennis adults. Products containing this fungus were available for commercial use in the United States but not registered for Asian longhorned beetle. This study tested different formulations and application rates of M. brunneum F52 microsclerotial granules for their potential development for management of A. glabripennis adults. Three application rates of M. brunneum microsclerotial granules relative to a 1× formulation from previous experiments (0.03 g/cm2; 2× = 0.06 g/cm2 and 3× = 0.09 g/cm2) were exposed on tree trunks for 4-wk periods during May-September. Increased application rates had better retention (% of initial g applied) than the 1× rate, rather than greater weathering loss. Microsclerotia at the 2× application produced 5.05 × 106 conidia/cm2, which was 18 times more conidia than the 1× application. Since A. glabripennis is under active eradication, bioassays with adult beetles were carried out in a quarantine laboratory, using the formulation samples from field exposures. The 2× application resulted in faster beetle mortality. The 3× and 2× rates were not significantly different in retention of the formulation, conidial production, or mortality, but 2× produced the most conidia per gram applied (3.92 × 109 conidia/g). An augmented formulation containing 70% M. brunneum by weight, rather than 50%, produced significantly more conidia and faster beetle mortality than the 50% formulation.

Biopesticide synergy when combining plant flavonoids and entomopathogenic baculovirus.

Four crop plants known to be hosts for the lepidopteran Trichoplusia ni (soybean, green bean, cotton, and cabbage) were treated with the biopesticide AfMNPV baculovirus in a dosage response assay. Treated soybean had, on average, a 6-fold increase in virus activity compared with the other crops. Leaf trichomes on soybeans were not found to be responsible for the observed increase of insecticidal activity. Three flavonoid compounds (daidzein, genistein, and kaempferol) were uniquely found only in the soybean crop, and were not detected in cotton, cabbage, or green bean plant matter. The individual flavonoid compounds did not cause T ni. mortality in no-virus assays when incorporated into artificial insect diet. The combination of the three flavonoid compounds at leaf level concentrations significantly increased baculovirus activity in diet incorporation assays. When the daidzein, genistein, and kaempferol were added to artificial diet, at 3.5-6.5 × leaf level concentrations, virus activity increased 1.5, 2.3, and 4.2-fold for each respective flavonoid. The soybean flavonoid compounds were found to synergistically improve baculovirus activity against T. ni.

Amylose Inclusion Complexes as Emulsifiers for Garlic and Asafoetida Essential Oils for Mosquito Control.

Although the insecticidal properties of some plant essential oils are well-documented, their use in integrated pest and vector management is complicated by their high volatility, low thermal stability, high sensitivity to oxidation, and low solubility in water. We investigated the use of bio-based N-1-hexadecylammonium chloride and sodium palmitate amylose inclusion complexes as emulsifiers for two essential oils, garlic and asafoetida, known to be highly toxic to mosquito larvae. Four emulsions of each essential oil based on amylose hexadecylammonium chloride and amylose sodium palmitate inclusion complexes were evaluated for their toxicity against Aedes aegypti L. larvae relative to bulk essential oils. All emulsions were significantly more toxic than the bulk essential oil with the lethal dosage ratios ranging from 1.09-1.30 relative to bulk essential oil. Droplet numbers ranged from 1.11 × 109 to 9.55 × 109 per mL and did not change significantly after a 6-month storage period. These findings demonstrated that amylose inclusion complexes enhanced the toxicity of essential oils and could be used to develop new essential oil based larvicides for use in integrated vector management.

Asian longhorned beetle bioassays to evaluate formulation and dose-response effects of Metarhizium microsclerotia.

Asian longhorned beetles (ALB; Anoplophora glabripennis), are invasive wood borers susceptible to Metarhizium brunneum. This fungus can be prepared as dried microsclerotia which, after rehydration, produce infective conidia within weeks. Wood samples coated with formulated microsclerotia were attached to trees in the Ohio USA ALB-eradication zone and collected after 4-week periods. Adult ALB exposed to these samples had 100% mortality. In an experiment comparing formulations with or without humectant hydrogel, hydrogel did not significantly increase mortality of exposed ALB. In a dose-response experiment with 5 application rates, ALB survival decreased with increasing application rate and conidial density.

In Vivo Production of Agrotis ipsilon Nucleopolyhedrovirus for Quantity and Quality.

The black cutworm, Agrotis ipsilon (Hüfnagel) (Lepidoptera: Noctuidae), is a pest causing damage to a variety of plants including turf and row crops. A recently discovered baculovirus has the potential to be developed as a microbial-based biological pesticide to provide targeted control of this insect pest. In an effort to develop this baculovirus as a biological pesticide, experiments were conducted to determine parameters necessary to maximize in vivo production using cutworm larvae. Treatment combinations including three larval diets, larval age at infection (6- to 10-d old), and dosage of virus exposure (1 × 105 to 1 × 108 occlusion bodies [OBs]/ml) were evaluated. Production quantity and quality were measured as number of OBs produced and insecticidal activity of the virus, respectively. Generally speaking, insect diets that maximized larval growth resulted in a greater quantity of virus OBs. Less virus was produced when younger (small) larvae were exposed to higher dosages of virus resulting in rapid mortality and when older (large) larvae were exposed to low dosages of virus resulting in low levels of infection. Virus quality was measured as insecticidal activity (low LC50 representing high activity) and was highest for larger larvae exposed to minimal virus concentrations needed to initiate infections. When considering both quantity and quality measurements, maximum production was achieved for 8- to 9-d-old larvae fed a general purpose lepidoptera diet. These results will support the development of this baculovirus as an additional tool for the integrated control of the black cutworm.

Characterization of Tolypocladium cylindrosporum (Hypocreales: Ophiocordycipitaceae) and Its Impact Against Aedes aegypti and Aedes albopictus Eggs at Low Temperature.

We examined the growth characteristics of Tolypocladium cylindrosporum IBT 41712 and its potential to infect eggs of Aedes aegypti and Ae. albopictus at a low temperature (15°C). When grown on Sabouraud dextrose agar supplemented with yeast extract, the IBT 41712 formed white colonies turning to a slightly darker, off-white color when mature. The mycelia bore swollen conidiophores producing smooth-walled, oblong to cylindrical conidia with varying sizes, ranging from 1.5 to 3.5 µm long. To determine the optimum temperature for the fungus, we cultured the fungus at eight temperatures (4°C, 12°C, 15°C, 21°C, 28°C, 33°C, 37°C, and 40°C) and measured the diametric growth. The optimum temperature for growth was 28°C since it had the highest diametric growth rate (2.1 ± 0.05 mm/day) and the fastest sporulation period (within 8-10 days of incubation). There was no fungal growth at the 3 highest temperatures (33°C, 37°C, and 40°C) but plates incubated at 33°C, when shifted to optimal temperature (28°C), showed visible growth indicating that following incubation at 33°C, the fungus remained viable. The IBT 41712 successfully infected mosquito eggs at 15°C. Fungal treatment induced egg hatch on moist seed-germination paper and this effect was more pronounced in Ae. aegypti compared to Ae. albopictus. When treated eggs were immersed in dH2O 21 days posttreatment, larval hatch of both Ae. aegypti (control = 91%, 1 × 107 conidia/ml, fungal treatment = 0%) and Ae. albopictus (control = 85%, fungal treatment = 28%) was significantly lower in fungal treatment compared to the controls. The ability of the strain to grow in a wide temperature range, and effectively infect mosquito eggs and induce egg hatch at a low temperature warrants further investigation for its potential as a mosquito control agent targeting eggs that overwinter or undergo long diapause.

Effect of spray drying on the properties of amylose-hexadecylammonium chloride inclusion complexes.

Water soluble amylose-hexadecyl ammonium chloride complexes were prepared from high amylose corn starch and hexadecyl ammonium chloride by excess steam jet cooking. Amylose inclusion complexes were spray dried to determine the viability of spray drying as a production method. The variables tested in the spray drying process were the% solids of the amylose-hexadecyl ammonium chloride complex being fed into the spray dryer, feed rate and the spray dryer outlet temperature. The amylose-inclusion complexes remained intact in all spray drying conditions tested as determined by X-ray diffraction. The rheological properties of solutions of the spray dried amylose-complexes remained unchanged when compared with the freeze dried control. Particle density and moisture content decreased with increased outlet temperature while particle size increased. X-ray diffraction and DSC analysis confirmed the formation of type II amylose inclusion complexes. Spray drying is a high throughput, low cost continuous commercial production method, which when coupled with excess steam jet cooking allows for the industrial scale production of cationic amylose-hexadecyl ammonium chloride complexes which may have value as flocculating and filtration enhancing agents and other aspects of paper production.

Dosage Response Mortality of Japanese Beetle, Masked Chafer, and June Beetle (Coleoptera: Scarabaeidae) Adults When Exposed to Experimental and Commercially Available Granules Containing Metarhizium brunneum.

Field-collected adults of three genera of turf-infesting scarabs, Japanese beetle ( Popillia japonica Newman), June beetles ( Phyllophaga spp.), and masked chafers ( Cyclocephala spp.), were exposed to experimental and commercial granule formulations of the entomopathogenic fungus Metarhizium brunneum (Petch) strain F52 to determine their relative susceptibility. Experimental granules contained microsclerotia produced by liquid fermentation with the ability to produce fresh conidia when rehydrated and commercial granules were Met 52 granular bioinsecticide. All three groups of scarab adults showed a positive dosage response to the fungus when exposed in cups of potting mix treated with the granules. LC 50 values for microsclerotia granules were 1.9 × 10 7 , 7.1 × 10 6 , and 3.2 × 10 6 conidia cup -1 for P. japonica , Phyllophaga spp., and Cyclocephala spp., respectively. LC 50 values for Met 52 granules were 5.9 × 10 7 , 5.1 × 10 7 , and 7.6 × 10 6 conidia cup -1 , respectively. The experimental granules containing microsclerotia show promise as a viable commercial control agent. They can be produced using lower cost fermentation methods and applied at lower dosages (97 g for 100 m 2 as opposed to 489 g per 100 m 2 for Met 52). If M. brunneum is applied to control the aforementioned white grubs, our data indicate the potential for the adult beetles to also be infected as they enter the soil to lay eggs.

Improved shelf life of dried Beauveria bassiana blastospores using convective drying and active packaging processes.

The yeast form (blastospore) of the dimorphic insect-pathogenic fungus Beauveria bassiana can be rapidly produced using liquid fermentation methods but is generally unable to survive rapid dehydration processes or storage under non-refrigerated conditions. In this study, we evaluated the influence of two convective drying methods, various modified atmosphere packaging systems, and storage temperatures on the desiccation tolerance, storage stability, and virulence of blastospores of B. bassiana ESALQ 1432. All blastospore formulations were dried to <5 % water content equivalent to aw < 0.3. The viability of B. bassiana blastospores after air drying and spray drying was greater than 80 %. Vacuum-packaged blastospores remained viable longer when stored at 4 °C compared with 28 °C with virtually no loss in viability over 9 months regardless the drying method. When both oxygen and moisture scavengers were added to sealed packages of dried blastospore formulations stored at 28 °C, viability was significantly prolonged for both air- and spray-dried blastospores. The addition of ascorbic acid during spray drying did not improve desiccation tolerance but enhanced cell stability (∼twofold higher half-life) when stored at 28 °C. After storage for 4 months at 28 °C, air-dried blastospores produced a lower LC80 and resulted in higher mortality to whitefly nymphs (Bemisia tabaci) when compared with spray-dried blastospores. These studies identified key storage conditions (low aw and oxygen availability) that improved blastospore storage stability at 28 °C and will facilitate the commercial development of blastospores-based bioinsecticides.

Evaluation of Metarhizium brunneum F52 (Hypocreales: Clavicipitaceae) for Control of Japanese Beetle Larvae in Turfgrass.

Experimental and commercial preparations of Metarhizium brunneum (Petch) strain F52 were evaluated for control of Japanese beetle, Popillia japonica Newman (Coleoptera: Scarbaeidae), larvae (white grubs) in the laboratory and under field conditions. Experimental preparations consisted of granule and liquid formulations made using in vitro produced microsclerotia, which are intended to produce infective conidial spores after application. These formulations were compared against commercial insecticides (imidacloprid and trichlorfon), and commercial formulations of M. brunneum F52 (Met 52) containing only conidia. Field-collected grubs were susceptible to infection in a dosage-dependent relationship when exposed to potting soil treated with experimental microsclerotia granules in the laboratory. The LC(50) for field-collected larvae was 14.2 mg of granules per cup (∼15 g granules/m(2)). Field plots treated with experimental and commercial formulations of M. brunneum F52 after 10 September (targeting second and third instar grubs) had significantly lower grub densities compared with untreated plots, providing 38.6-69.2% control, which sometimes equaled levels of control with chemical insecticides. Fungal treatments made prior to 21 August provided 14.3-69.3% control, although grub densities resulting from these treatments were often not significantly lower than those in untreated control plots. By comparison, chemical insecticide treatments provide 68-100% grub control, often providing better control when applied earlier in the season. In conclusion, P. japonica larvae are susceptible to infection by M. brunneum, and grub densities were reduced most consistently by fall applications targeting later instars.

Glucose concentration alters dissolved oxygen levels in liquid cultures of Beauveria bassiana and affects formation and bioefficacy of blastospores.

The filamentous fungus Beauveria bassiana is an economically important pathogen of numerous arthropod pests and is able to grow in submerged culture as filaments (mycelia) or as budding yeast-like blastospores. In this study, we evaluated the effect of dissolved oxygen and high glucose concentrations on blastospore production by submerged cultures of two isolates of B. bassiana, ESALQ1432 and GHA. Results showed that maintaining adequate dissolved oxygen levels coupled with high glucose concentrations enhanced blastospore yields by both isolates. High glucose concentrations increased the osmotic pressure of the media and coincided with higher dissolved oxygen levels and increased production of significantly smaller blastospores compared with blastospores produced in media with lower concentrations of glucose. The desiccation tolerance of blastospores dried to less than 2.6 % moisture was not affected by the glucose concentration of the medium but was isolate dependent. Blastospores of isolate ESALQ1432 produced in media containing 140 g glucose L(-1) showed greater virulence toward whitefly nymphs (Bemisia tabaci) as compared with blastospores produced in media containing 40 g glucose L(-1). These results suggest a synergistic effect between glucose concentration and oxygen availability on changing morphology and enhancing the yield and efficacy of blastospores of B. bassiana, thereby facilitating the development of a cost-effective production method for this blastospore-based bioinsecticide.