Interaction of fungicides with the entomopathogenic fungus Isaria fumosorosea

The effects of eight commonly used fungicides: propamocarb, fenarimol, triadimefon, procimidone, azoxystrobin, carbendazim, cooper oxychloride and Trichoderma harzianum on germination, mycelial growth and virulence of Isaria fumosorosea (Wize) Brown & Smith (Ascomycota: Hypocreales) was studied. The greatest effect on germination was observed by azoxystrobin, followed by carbendazim, triadimefon and procimidone. Propamocarb, fenarimol, cooper oxychloride and T. harzianum did not affect conidial germination with germinations of 95, 93, 79 and 84%, respectively. Virulence was evaluated against early fourth instar nymphs of Trialeurodes vaporariorum (Hemiptera: Aleyrodidae). The mix containing fungal conidial suspensions plus cooper oxychloride or fenarimol presented a significant reduction in the mortality in comparison with spore suspension itself. This study suggests that the most appropriate fungicides for use in Integrated Pest Management Programs against T. vaporariorum in combination with I. fumosorosea are propamocarb and T. harzianum.     

In vitro compatibility of Beauveria bassiana strain ATCC 74040 with copper fungicides

Copper fungicides and mycoinsecticides based on entomopathogenic fungi Beauveria spp. are the most common pesticides used in organic crop production systems. The in vitro effects of the copper fungicides copper oxide, copper hydroxide, copper oxychloride, copper sulphate, dicopper chloride trihydroxide and tribasic copper sulphate were investigated for mycelial growth, sporulation and conidial germination of the ATCC 74040 commercial strain of Beauveria bassiana. Mycelial growth was evaluated on potato dextrose agar plates with 100%, 75%, 50%, 25%, 12.5%, 6.25% and 0% of the recommended application rates of each fungicide at 15 and 25°C. Sporulation and conidial germination were determined at the recommended field doses of each fungicide at 25°C. All copper fungicides had fungistatic or fungicidal effects on B. bassiana that varied according to the dose. Only in two cases, copper oxide at 15°C and copper hydroxide at 25°C, at the lowest concentration of 6.5%, was mycelial growth not statistically significantly inhibited. Inhibition of mycelial growth depended both on the fungicide and its concentration, and partly on temperature. Both sporulation and conidial germination of B. bassiana were significantly inhibited by all fungicides. All fungicides inhibited the sporulation in a similar way (99.8%–100%). With the exception of copper oxychloride (inhibition, 13.6%), the other fungicides showed high detrimental effects on conidial germination (inhibition, 91.7%–100%). The fungus was strongly affected by some fungicides even at the lowest doses. The biological index used for the B. bassiana with copper fungicides ranged from 0.6 (copper sulphate) to 18.1 (copper oxychloride). Therefore, the tested fungicides were classified into the upper half of the highly toxic (T) category and are considered incompatible with the entomopathogenic fungus B. bassiana strain ATCC 74040 under in vivo experimental conditions. These results need to be further verified in vitro under both greenhouse and open-field conditions.     

Biochemical properties of different entomopathogenic fungi and their virulence against Chilo suppressalis (Lepidoptera: Crambidae) larvae

We determined the virulence of Beauveria bassiana, Metarhizium anisopliae, Isaria fumosoroseus and Lecanicilium lecanii against larvae of Chilo suppressalis Walker by bioassay and evaluated several enzymatic and non-enzymatic components. LC₅₀ values of the entomopathogenic fungi revealed 90, 32, 45,000, 4600, 42,000 and 1,540,000 spores/larva for isolates BB1–BB3 of B. bassiana, I. fumosoroseus, M. anisopliae and L. lecanii, respectively. Isolate BB3 and I. fumosoroseus had the highest amounts of total protein and hydrophobin and isolates BB3 and M. anisopliae showed the highest activities of lipases and chitinases. In case of proteases, the highest activities were observed for Pr1 of BB1 and Pr2 of L. lecanii. The highest general esterase activities were obtained in I. fumosoroseus and BB1 when 1-naphtyl acetate and 2-naphtyl acetate were used as substrates. The highest activity of glutathione S-transferase (GST) was observed in I. fumosoroseus by using both reagents but BB1 demonstrated the highest activities of alkaline phosphatase and acid phosphatase. Clustering of the fungi using biochemical enzymes revealed BB2 and BB3 as a separate group of entomopathogenic fungi. In another group, I. fumosoroseus and L. lecanii had the most similarity and were separated from BB1 and M. anisopliae. The fungi exhibited different virulence on larvae of C. suppressalis by producing adhering protein and extracellular enzymes. Overall, results of the bioassays and clustering based on enzymatic activities revealed that isolate BB2 was the most effective fungus against larvae of C. suppressalis.     

Behavioral and electrophysiological responses of Coptotermes formosanus Shiraki towards entomopathogenic fungal volatiles

Termites adjust their response to entomopathogenic fungi according to the profile of fungal volatile organic compounds (VOCs). This study demonstrates the pathogenicity of Metarhizium anisopliae, Beauveria bassiana and Isaria fumosorosea (=Paecilomyces fumosoroseus) towards the Formosan subterranean termite, Coptotermes formosanus Shiraki (Isoptera: Rhinotermitidae). Using no-choice assays, M. anisopliae was found to be highly virulent (LT₅₀ 3.10 d) when compared to B. bassiana (LT₅₀ 6.62 d) and I. fumosorosea (LT₅₀ 12.39 d). Also using choice assays, the foraging behavior of C. formosanus was determined in the presence of pathogenic fungi. The highly pathogenic fungi (M. anisopliae) elicited a repellent response, causing most of the termites to forage in a safe zone farthest from the fungal source. This repellency resulted in relatively low mortality similar to the controls. The repellency of M. anisopliae conidia can be used to protect human belongings and timber from termites. While I. fumosorosea cultures were not repellent to C. formosanus workers, the termites were highly susceptible to infection. Electroantennographic responses of workers showed approximately 47% and 78% lower level of response to conidia of B. bassiana and I. fumosorosea, respectively, as compared to M. anisopliae. The VOC profile of repellent cultures of M. anisopliae mainly consisted of paraffins (60.97%), while the major proportion of the I. fumosorosea profile consisted of branched and cyclic alkanes (84.41%). From the above findings, we conclude that the incorporation of I. fumosorosea may increase the control potential of bait.     

Superoxide dismutase production by Isaria fumosorosea on metals and its role in stress tolerance and fungal virulence

Superoxide dismutase (SOD) is an anti-oxidant enzyme which also plays a role in fungal virulence. The present study was conducted to elucidate its role in fungal infection and stress tolerance of entomopathogenic fungi, Isaria fumosorosea. SOD activity of I. fumosorosea conidia differed significantly on the growth medium supplemented with different metal compounds. The use of Cu + Zn proved to be the most active inducer of SOD activity. Cu + Zn treatment enhanced the fungal tolerance to oxidative stress generated by menadione in the medium (0–3 mM) as evaluated by colony growth. The conidial tolerance to UV-B radiation and heat was evaluated by assays of spore germination. Conidia produced on cultures with Cu + Zn were more tolerant to UV-B and thermal stress as well as exhibiting a higher rate of virulence against P. xylostella larvae. Our study highlights that SOD contributes significantly to the virulence and stress tolerance of I. fumosorosea and reveals possible means to improving field persistence and efficacy of a fungal formulation by manipulating the antioxidant enzymes of fungal pathogens.     

Insecticidal activity of entomopathogenic fungi (Hypocreales) for potato psyllid,Bactericera cockerelli (Hemiptera: Triozidae): Development of bioassay techniques,effect of fungal species and stage of the psyllid

The potato psyllid, Bactericera cockerelli (?ulc), is a pest of potato, tomato, and some other solanaceous vegetables and has also been incriminated in the transmission of a bacterial pathogen, Candidatus Liberibacter solanacearum, resulting in a serious disease known as ‘zebra chip’. Although there are several reports of fungal pathogens in psyllids, there are none from B. cockerelli, nor have any fungi been evaluated against it. Five isolates of fungi, one Beauveria bassiana, two Metarhizium anisopliae and two Isaria fumosorosea, were bioassayed against B. cockerelli on potato leaves under ideal conditions for the fungi. All applications were made with a Potter spray tower. With the exception of concentration-effect studies, all other applications were made using 10⁷ conidia/mL in a 2-mL aqueous suspension. All isolates except B. bassiana, produced 95–99% mortality, corrected for control mortality, in adults 2–3 days after application of conidia and 91–99% in nymphs 4 days after application. The corrected mortalities for adults and nymphs treated with B. bassiana were 53 and 78%, respectively, 4 days after application. I. fumosorosea Pfr 97 produced 95% corrected mortality in both first and late third instar nymphs. M. anisopliae (F 52) produced 96% corrected mortality in first and third instar nymphs. Pfr 97 and F 52 were evaluated for insecticidal activity against third instar B. cockerelli using 10⁵, 10⁶, and 10⁷ conidia per mL. Mortality produced by I. fumosorosea Pfr 97 ranged from 83 to 97% and that of M. anisopliae F 52 was 88 to 95% at these concentrations.     

Conidial water affinity is an important characteristic for thermotolerance in entomopathogenic fungi

The interspecific thermotolerance of several species of entomopathogenic fungi was evaluated based on the conidial water affinity. The species were divided between hydrophilic and hydrophobic conidia. The species with hydrophobic conidia were Beauveria bassiana (ARSEF 252), Metarhizium brunneum (ARSEF 1187), Metarhizium robertsii (ARSEF 2575), Isaria fumosorosea (ARSEF 3889) and Metarhizium anisopliae s.l. (ARSEF 5749). The species with hydrophilic conidia were Tolypocladium cylindrosporum (ARSEF 3392), Tolypocladium inflatum (ARSEF 4877), Simplicillium lanosoniveum (ARSEF 6430), Lecanicillium aphanocladii (ARSEF 6433), S. lanosoniveum (ARSEF 6651), Aschersonia placenta (ARSEF 7637) and Aschersonia aleyrodis (ARSEF 10276). The conidial surface tension of each isolate was also studied. Conidial suspensions were exposed to 38, 41 or 45 °C. After exposure, the suspensions were inoculated on media and conidial germination was evaluated. Considerable differences in thermotolerance were found among the 12 entomopathogenic fungal species. Species with hydrophobic conidia were generally more thermotolerant than species with hydrophilic conidia. All isolates with hydrophobic conidia showed higher conidial surface tension than the isolates with hydrophilic conidia.     

Compatability of Metarhizium anisopliae var. anisopliae with chemical pesticides

The effects of various insecticides on the mycelial growth, sporulation and conidial germination of Metarhizium anisopliae var. anisopliae isolate E₉ were studied in the laboratory. Chlorpyrifos was the most toxic organophosphate to mycelial growth and sporulation at all concentrations. Temephos, malathion and leptophos were highly toxic to sporulation while malathion was the most inhibitory to germination. The carbamates, carbofuran, methomyl and oxamyl were moderately toxic to mycelial growth and sporulation while oxamyl had an adverse effect on germination. The pyrethroids (pyrethrin, permethrin and resmethrin) and the insect growth regulators (diflubenzuron and methoprene) were not inhibitory to the various developmental stages of isolate E₉. The chlorinated hydrocarbons (chlordane, lindane and toxaphene) were more deleterious than all other insecticide groups tested. Among the fungicides, benomyl and maneb produced the greatest inhibition.     

西花蓟马高毒力虫生真菌筛选及其生防应用潜力的研究进展

西花蓟马是一种外来入侵的世界性害虫,对农林业危害巨大。查阅国内外相关文献,综述了当前防治西花蓟马的虫生真菌的种类、高毒力菌株的筛选及防治现状。现已知西花蓟马的寄生病原真菌有5种,包括蜡蚧轮枝菌(半知菌:丝孢目)、球孢白僵菌(半知菌:丝孢目)、金龟子绿僵菌(半知菌:丝孢目)、玫烟色棒束孢(半知菌:束梗孢目)和小孢新接霉。其中,球孢白僵菌、金龟子绿僵菌在西花蓟马的生物防治中应用最广,具有良好的开发应用潜力,部分防效好的虫生真菌已申请专利及实现工厂化生产。     

Growth and sporulation of Beauveria bassiana and Metarrhizium anisopliae on media containing various amino acids

Natural isolates of two entomogenous fungi, Beauveria bassiana and Metarrhizium anisopliae, were cultured in liquid culture media containing 24 amino acids and KNO₃ to determine their effect on growth and sporulation. In addition, the growth and medium pH changes for each isolate grown on an asparagine-containing medium were compared. Tryptophan and alanine were most effective for growth and sporulation of B. bassiana, although glutamine and KNO₃ also produced large numbers of regularly shaped spores. Tryptophan, glutamic acid, and histidine were all well utilized for both growth and sporulation of M. anisopliae. Nitrogen sources containing sulfur were poorly utilized for sporulation by M. anisopliae. In general, B. bassiana produces greater mycelial mass and much larger numbers of spores than M. anisopliae. Both fungi attained nearly the same growth maximum on asparagine medium though B. bassiana exhibited an initially more rapid growth rate. In both fungi this rapid growth phase was accompanied by a decline in medium pH followed by a rise in pH during the decline phase of growth.     

Pathogenicity of fungal isolates (Ascomycota: Hypocreales) against Peregrinus maidis, Delphacodes kuscheli (Hemiptera: Delphacidae), and Dalbulus maidis (Hemiptera: Cicadellidae), vectors of corn diseases

Preliminary screening assays were carried out on 17 isolates from five fungal species Beauveria bassiana, Lecanicillium muscarium, Metarhizium anisopliae, Isaria farinosa, and I. fumosorosea. The three most effective isolates against Peregrinus maidis (Hemiptera: Delphacidae) were B. bassiana CEP 147, CEP 150, and CEP 189. There were no consistent differences found in males and females regarding fungal susceptibility. However, more females than males were proportionally infected. There was not a correlation between the percentage of conidial germination and the percentage of mortality caused by fungal infection in any of the treatments. Only B. bassiana CEP 147, which caused a cumulative mortality of 69.8 ± 6.4% after 7 days post-inoculation, was selected to be assayed against adults of P. maidis, Delphacodes kuscheli (Hemiptera: Delphacidae), and Dalbulus maidis (Hemiptera: Cicadellidae). In pathogenicity tests significant differences were observed among treatments. After 2 weeks post-inoculation, both D. kuscheli (cumulative mortality of 73.3 ± 9.0%) and P. maidis (cumulative mortality of 68.6 ± 6.7%) were significantly more susceptible than D. maidis (cumulative mortality of 49.9 ± 9.7%) to the selected isolate.     

Virulence of Hypocreales fungi to pecan aphids (Hemiptera: Aphididae) in the laboratory

There is need for efficacious biocontrol agents for aphids in commercial orchards. As a preliminary step to this end we determined the virulence of several Hypocreales fungi to pecan aphids. In the first experiment we tested the virulence of Isaria fumosorosea (ARSEF 3581) blastospores to three pecan aphids Monellia caryella, Melanocallis caryaefoliae, and Monelliopsis pecanis under laboratory conditions. Rates of 1 × 10⁷ or 1 × 10⁸ spores per ml were applied in 2 ml via a spray tower to 90 mm Petri dishes containing 10 aphids each. Mortality and mycosis were determined after 24, 48 and 72 h. Treatment effects were observed by 48 h post-application, and by 72 h the higher application rate caused >90% mortality and mycosis in M. caryella and M. caryaefoliae, whereas <70% was observed in M. pecanis.We conducted two subsequent experiments (Experiments 2 and 3), using the same methodology, to compare the virulence of several Hypocreales species and strains against the aphid of primary economic concern to most pecan growers, M. caryaefoliae. In Experiment 2, we compared blastospores and conidia of two I. fumosorosea strains (ARSEF 3581 and ATCC 20874 [= strain 97]). The blastospores of ARSEF 3581 and conidia of ATCC 20874 showed higher virulence than other treatments and thus were included in Experiment 3, which also compared the virulence of conidia of Beauveria bassiana (GHA strain) and Metarhizium anisopliae (F52 strain). Results in Experiment 3 indicated the highest virulence in I. fumosorosea 3581 blastospores and M. anisopliae (F52) followed by I. fumosorosea (20874) conidia. The detection of pathogenicity to pecan aphids establishes the potential for commercial usage and additional study. Results reported here will narrow treatments to test in future greenhouse and field trials.     

Impact of fungicides on Metarhizium anisopliae in the rhizosphere, bulk soil and in vitro

The entomopathogenic fungus Metarhizium anisopliae (Metchnikoff) Sorokin (Hypocreales: Clavicipitaceae) is registered in the United States and The Netherlands for black vine weevil, Otiorhynchus sulcatus (Coleoptera: Curculionidae) control in container-grown ornamentals. These studies were conducted to determine the compatibility of M. anisopliae (F52) with a wide range of fungicides commonly applied to container-grown ornamentals for the management of soil-borne plant pathogens. The impact of fungicides on spore germination and mycelial growth were determined in vitro. In addition, M. anisopliae persistence in bulk and rhizosphere soil was determined 30 days following dual application of each fungicide at 7–28 days intervals as prescribed. A number of fungicides (thiophanate-methyl, dimethomorph, captan, triflumizole, triflozystrobin, pyraclostrobin, azoxystrobin) inhibited spore germination in vitro. A larger number of fungicides (fosetyl-AI, thiophanate-methyl, dimethomorph, captan, quintozene, triflumizole, fludioxanil, triflozystrobin, pyraclostrobin, fludiox-mefanox, iprodione, azoxystrobin, phosphorus acid/K-salts) inhibited mycelial growth in vitro. Only three fungicides (etridiazole, propamocard and mafanoxam) had no significant impact in vitro on spore germination or mycelial growth. While a number of fungicides had a detrimental impact in vitro, there was no impact on M. anisopliae populations in bulk soil following dual application of any fungicide. However, the fungicides captan and triflumizolet, which have a short reapplication interval, had a detrimental impact on M. anisopliae populations in the rhizosphere. As researchers develop rhizosphere competence as an alternative management strategy for black vine weevil, the fungicides captan and triflumizole should be avoided.     

Growth and sporulation of entomopathogenic Beauveria bassiana,Metarhizium anisopliae,Isaria farinosa and Isaria fumosorosea strains in relation to water activity and temperature interactions

This study examined six strains of Beauveria bassiana s.l. and Isaria farinosa, one strain of Isaria fumosorosea and five strains of Metarhizium anisopliae s.l. to identify the ability for (1) growth and (2) sporulation under interacting environmental factors of water activity (a_w) and temperature stress. Growth on Sabouraud Dextrose Agar (SDA; water activity, a_w = 0.995) or SDA modified with glycerol to 0.98, 0.96 and 0.94 a_w was measured at four different temperatures (25, 30, 35 and 37°C). All M. anisopliae strains grew at 25–35°C and 0.995 a_w while only two strains tolerated extreme water stress at 0.94 a_w.Three strains of B. bassiana were able to grow at 25–37°C and 0.995 a_w. Only one strain of I. farinosa was able to grow at 25–37°C and 0.995 a_w. A_w and temperature interactions resulted in different strain-dependent responses, in terms of growth and sporulation. Only one strain of I. farinosa and three of M. anisopliae grew at 0.94 a_w and none of the B. bassiana strains tolerated such water stress. At 0.96 and 0.94 a_w and 35–37°C, sporulation by all the strains of the three species were significantly affected. Under elevated temperatures and drought stress, very few of these strains of entomopathogenic fungi are able to grow and sporulate. Indeed, the B. bassiana strains were unable to tolerate the extreme conditions examined. Resilience to such abiotic interactions is critical for selecting strains for formulations. Tolerance to water and temperature stress could be good criteria for selection of strains with secondary spread potential for use as part of an integrated pest management system where secondary cycling may be important, especially in sub-tropical and tropical environments.     

The effect of insecticides on growth,germination and cuticle-degrading enzyme production by Isaria fumosorosea

The influence of six chemical insecticides on growth, sporulation, conidial germination and cuticle-degrading enzyme production by Isaria fumosorosea were investigated under laboratory conditions. Maximum reduction in vegetative growth, sporulation and conidial germination in relation to the control treatment was observed for Chloranthraniliprole whereas Indoxacarb proved to be the safest insecticide causing lowest reduction in these parameters. Chloranthraniliprole, Chlorpyrifos and Chlorfenapyr caused higher reduction in enzyme activities (chitinase, Pr1, Pr2 and lipase) at all three concentrations whereas very low reduction in enzyme activities was caused by Hubendamide+ Avermectin and Indoxacarb when used at 10 µg/ml. The data presented can be used for future recommendations of these insecticides in IPM programmes where I. fumosorosea is an important control agent.     

Optimised fermentation conditions and improved collection efficiency using dual cyclone equipment to enhance fungal conidia production

Methods for enhancing conidial yield and for harvesting pure fungal conidia of entomopathogenic fungi were investigated. Fermentation conditions (liquid-to-solid ratio, MgSO₄·7H₂O, incubation temperature, inoculum sizes, KNO₃ and relative humidity) of Beauveria bassiana s.l. and Metarhizium anisopliae s.l. were optimised to increase the conidial yields that reached 11.2 mg/g and 24.5 mg/g, increases of 72% and 52% compared to the unoptimised yields of 6.5 mg/g and 16.1 mg/g, respectively. Three methods were compared for harvesting pure conidia of B. bassiana: dual cyclone equipment (DCE), sieving 200 and elution with 0.02% Tween-80 suspension. DCE performed the best, giving a conidial yield of 12.6 mg/g and 1.8 × 10¹⁰ conidia·g^–1. To further enhance the harvest efficiency, response surface methodology combined with a Box–Behnken design was employed, and the conidial yield of B. bassiana reached 20.9 mg/g, a total increase of 221% compared to the original conditions. Under these optimised harvest parameters, the conidial yield of M. anisopliae rose to 42.2 mg/g, an increase of 162%. The conidia of B. bassiana and M. anisopliae harvested in this way were pure, with no mycelial fragments or substrate visible in microscopic images.     

Conidiation under illumination enhances conidial tolerance of insect-pathogenic fungi to environmental stresses

Light is an important signal for fungi in the environment and induces many genes with roles in stress and virulence responses. Conidia of the entomopathogenic fungi Aschersonia aleyrodis, Beauveria bassiana, Cordyceps fumosorosea, Lecanicillium aphanocladii, Metarhizium anisopliae, Metarhizium brunneum, Metarhizium robertsii, Simplicillium lanosoniveum, Tolypocladium cylindrosporum, and Tolypocladium inflatum were produced on potato dextrose agar (PDA) medium under continuous white light, on PDA medium in the dark, or under nutritional stress (= Czapek medium without sucrose = MM) in the dark. The conidial tolerance of these species produced under these different conditions were evaluated in relation to heat stress, oxidative stress (menadione), osmotic stress (KCl), UV radiation, and genotoxic stress caused by 4-nitroquinoline 1-oxide (4-NQO). Several fungal species demonstrated greater stress tolerance when conidia were produced under white light than in the dark; for instance white light induced higher tolerance of A. aleyrodis to KCl and 4-NQO; B. bassiana to KCl and 4-NQO; C. fumosorosea to UV radiation; M. anisopliae to heat and menadione; M. brunneum to menadione, KCl, UV radiation, and 4-NQO; M. robertsii to heat, menadione, KCl, and UV radiation; and T. cylindrosporum to menadione and KCl. However, conidia of L. aphanocladii, S. lanosoniveum, and T. inflatum produced under white light exhibited similar tolerance as conidia produced in the dark. When conidia were produced on MM, a much stronger stress tolerance was found for B. bassiana to menadione, KCl, UV radiation, and 4-NQO; C. fumosorosea to KCl and 4-NQO; Metarhizium species to heat, menadione, KCl, and UV radiation; T. cylindrosporum to menadione and UV radiation; and T. inflatum to heat and UV radiation. Again, conidia of L. aphanocladii and S. lanosoniveum produced on MM had similar tolerance to conidia produced on PDA medium in the dark. Therefore, white light is an important factor that induces higher stress tolerance in some insect-pathogenic fungi, but growth in nutritional stress always provides in conidia with stronger stress tolerance than conidia produced under white light.     

Susceptibility of the cactus weevil Metamasius spinolae to Beauveria bassiana and Metarhizium anisopliae under laboratory and field conditions

Aims: To evaluate different entomopathogenic fungal isolates against the cactus weevil Metamasius spinolae under laboratory and field conditions, and select an isolate to be used as a tool in the management of this insect pest. Methods and Results: Four experiments were carried out. The effect of temperature on the in vitro growth of eight isolates of entomopathogenic fungi (two Metarhizium anisopliae and six Beauveria bassiana) was assessed. The susceptibility of adult M. spinolae to the same isolates was evaluated. Using three selected isolates, the interaction between susceptibility and sex of the insect was studied. Finally, a field experiment was carried out to evaluate infection of adult M. spinolae by the same three isolates under natural abiotic conditions. Overall, growth rate was greatest at 25°C for all the isolates. In vitro growth of M. anisopliae was greater than B. bassiana. Mortality of adult M. spinolae was greater when inoculated with B. bassiana compared with isolates of M. anisopliae. Susceptibility had no interaction with the sex of the insect. The proportion of insects succumbing to infection was smaller when incubated under field conditions than when incubated under laboratory conditions. Conclusions: The experiments described here showed a complex interaction between entomopathogenic fungi and M. spinolae, and these data allows us to select isolate Bb107 as a first step towards its use in the management of this pest insect. Significance and Impact of the Study: Our results showed that entomopathogenic fungi can be used for the control of M. spinolae, which may help reduce the use of chemical insecticides and, therefore, the exposure of Opuntia ficus‐indica producers to pesticides.     

Carbon Requirements of Some Nematophagous, Entomopathogenic and Mycoparasitic Hyphomycetes as Fungal Biocontrol Agents

Thirty-three carbon sources were evaluated for their effects on spore germination, hyphal growth and sporulation of 11 fungal biocontrol agents, i.e. the nematophagous fungi Paecilomyces lilacinus, Pochonia chlamydosporia, Hirsutella rhossiliensis, H. minnesotensis and Arkansas Fungus 18, the entomopathogenic fungi Lecanicillium lecanii, Beauveria bassiana and Metarhizium anisopliae, and the mycoparasitic fungus Trichoderma viride. Variations in carbon requirements were found among the fungal species or strains tested. All strains studied except for T. viride grew on most carbon sources, although B. bassiana had more fastidious requirements for spore germination. Monosaccharides and disaccharides were suitable for fungal growth. For most isolates, d-glucose, d-mannose, sucrose and trehalose were superior to pectin and soluble starch among the polysaccharides and lactic acid among the organic acids. Both ethanol and methanol could accelerate growth of most isolates but not biomass. d-mannose, d-fructose and d-xylose were excellent carbon sources for sporulation, while d-glucose, sucrose, cellobiose, trehalose, chitin, dextrin, gelatin and lactic acid were better for some isolates. Neither sorbic acid nor linoleic acid could be utilized as a single carbon source. These findings provided a better understanding of the nutritional requirements of different fungal biocontrol agents that can benefit the mass production process.     

Soil management effects on entomopathogenic fungi during the transition to organic agriculture in a feed grain rotation

The growing demand for organic products creates opportunities for farmers. Information on the consequences of management practices can help farmers transition to organic and take advantage of these prospects. We examined the interaction between soil disturbance and initial cover crop on naturally occurring entomopathogenic fungi (EPF) during the 3-year transition to organic production in a feed grain rotation in central Pennsylvania. Our experiment included four systems comprised of a factorial combination of two levels of primary tillage (full vs. reduced) and two types of initial cover crop (timothy/clover vs. rye/vetch). The cropping sequence consisted of an initial cover crop, followed by soybean, and finally, maize. The entire experiment was replicated in time, with the initiation lagged by 1 year. We detected four species of EPF (Metarhizium anisopliae, Beauveria bassiana, Isaria fumosorosea, and Isaria farinosa) by bioassay of soil samples collected four times during each field season. The latter three species were detected infrequently; therefore, we focused statistical analysis on M. anisopliae. Detection of M. anisopliae varied across sampling date, year in crop sequence, and experimental start, with no consistent trend across the 3-year transition period. M. anisopliae was isolated more frequently in the systems initiated with timothy/clover cover crops and utilizing full tillage; however, we only observed a tillage effect in one temporal replicate. M. anisopliae detection was negatively associated with soil moisture, organic matter, and zinc, sulfur, and copper concentrations in the soil. This study helps to inform farmers about management effects on soil function, specifically conservation biological control.