Dry mycelium preparations of entomopathogenic fungi,Metarhizium anisopliae and Beauveria bassiana

Several different harvesting procedures were used to obtain dry mycelium preparations of the entomopathogenic fungi, Metarhizium anisopliae and Beauveria bassiana. The effects of these procedures on the survival of the fungal preparations and on their conidiation after short periods of storage at room temperature and at 4°C were examined. Harvesting procedures consisted of filtering the mycelium produced in airlift containers from the culture medium, washing with deionized water, spraying with a sugar solution, and incubating for 18 hr at 4°C before drying. Conidial production of treated mycelia stored 1.5 and 4.5 months at 4°C was not significantly different for and procedure. For dry mycelium of M. anisopliae stored 1.5 months at 4°C and then at room temperature for 3 months, maltose- and sucrose-treated preparations produced more conidia than preparations sprayed with dextrose solution, with water only, or not sprayed. B. bassiana preparations dried soon after mat formation were superior to those incubated at 4°C, and maltose-and dextrose-treated mycelia were superior to other treatments when stored at room temperature.     

Susceptibility of Agrilus planipennis (Coleoptera: Buprestidae) to Beauveria bassiana and Metarhizium anisopliae

The susceptibility of Agrilus planipennis Fairmaire (Coleoptera: Buprestidae) to selected strains of the entomopathogenic fungi Beauveria bassiana (Balsamo) Vuillemin and Metarhizium anisopliae (Metschnikoff) Sorokin was evaluated through bioassays with direct immersion or foliar exposure under laboratory conditions. Results showed that A. planipennis adults were susceptible to B. bassiana and M. anisoplae. Significant time-mortality response was found for each isolates. Isolate B. bassiana GHA killed A. planipennis adults at a faster rate compared with other isolates tested, with the lowest average time-to-death values. The LC50 values estimated under direct immersion method ranged from 1.7 x 10(5) to 1.9 x 10(7), 3.5 x 10(4) to 5.3 x 10(5), and 4.1 x 10(3) to 2.9 x 10(5) conidia/ml for B. basissiana and from 3.2 x 10(6) to 1.1 x 10(7), 4.5 x 10(3) to 4.5 x 10(5), and 1.4 x 10(2) to 1.2 x 10(5) conidia/ml for M. anisopliae at 4, 5, and 6 d after treatment, respectively. By days 5 and 6, B. bassiana GHA outperformed all other isolates tested except ARSEF 7234, followed by ARSEF 7152, 6393, and 7180. Significant concentration-mortality response was also observed for two B. bassiana GHA formulations, BotaniGard ES and Mycotrol O, and M. anisopliae F52 when insects were treated through foliar exposure. The LC50 values ranged from 114.5 to 309.6, 18.4 to 797.3, and 345.3 to 362.0 conidia/cm2 for BotaniGard, Mycotrol, and M. anisopliae F52, respectively. Based on the results of these bioassays, the efficacy of both B. bassiana GHA formulations and M. anisopliae F52 were similar against adult A. planipennis. The potential use of entomopathogenic fungi for management of A. planipennis in North America is discussed.     

Characterization of Beauveria bassiana and Metarhizium anisopliae isolates for management of tarnished plant bug,Lygus lineolaris (Hemiptera: Miridae)

Selected morphological and physiological characteristics of four Beauveria bassiana (Balsamo) Vuillemin isolates and one Metarhizium anisopliae (Metschnikoff) Sorokin isolate, which are highly pathogenic to Lygus lineolaris (Palisot de Beauvois) (Hemiptera: Miridae), were determined. There were significant differences in conidial size, viability, spore production, speed of germination, relative hyphal growth, and temperature sensitivity. Spore viability after incubation for 24h at 20 degrees C ranged from 91.4 to 98.6% for the five isolates tested. Spore production on quarter-strength Sabouraud dextrose agar plus 0.25% (w/v) yeast extract after 10 days incubation at 20 degrees C ranged from 1.6x10(6) to 15.5x10(6)conidia/cm(2). One B. bassiana isolate (ARSEF 1394) produced significantly more conidia than the others. Spore germination was temperature-dependant for both B. bassiana and M. anisopliae. The time required for 50% germination (TG(50)) ranged from 25.0 to 30.9, 14.0 to 16.6, and 14.8 to 18.0h at 15, 22, and 28 degrees C, respectively. Only the M. anisopliae isolate (ARSEF 3540) had significant spore germination at 35 degrees C with a TG(50) of 11.8h. A destructive sampling method was used to measure the relative hyphal growth rate among isolates. Exposure to high temperature (40-50 degrees C) for 10min had a negative effect on conidial viability. The importance of these characteristics in selecting fungal isolates for management of L. lineolaris is discussed.     

Efficacy of entomopathogenic fungi Beauveria bassiana and Metarhizium anisopliae against Thaumetopoea pityocampa Shiff. (Lepidoptera: Thaumatopoeidae)

Abstract

In this study, Metarhizium anisopliae TR 106 and Beauveria bassiana TR 217 was tested against fourth instar larvae of Thaumetopoea pityocampa. The LT₅₀ and LT₉₀ of 1?×?10⁶ concentration of M. anisopliae against T. pityocampa were 3.60 and 4.11 for direct application, while these were 2.87 and 3.60?days, respectively in leaves application. The LT₅₀ and LT₉₀ of the 1?×?10⁸ concentration of the same isolate were 2.50 and 2.95?days for direct application, and 2.98 and 3.74?days for leaves application. The LT₅₀ of insect and leaves application for 1?×?10⁶ of B. bassiana were 3.75 and 3.49?days, respectively. The LT₉₀ of same concentration for insect application was 4.48?days, while LT₉₀ for leaves application was 4.63?days. Similarly, LT₅₀ of insect and leaves application for 1?×?10⁸ of B. bassiana were 3.03 and 3.31?days, while LT₉₀ were 3.68 and 4.29?days, respectively. Approximate 100% mycosis was observed in all treatments.     

Isolation of Beauveria bassiana and Metarhizium anisopliae var. anisopliae from Boophilus microplus tick (Canestrini, 1887), in Rio de Janeiro State,Brazil

The objective of this work were to isolate and identify strains of entomopathogenic fungi from ingurgitated female Boophilus microplus ticks, collected from the soil in the municipality of Paracambi, Rio de Janeiro State, Brazil. The ingurgitated females were inoculated in the selective medium oat dodine agar (oda), where 49 colonies of Beauveria bassiana (71%) and 20 of Metarhizium anisopliae var. anisopliae (29%) were isolated. These isolated strains characterize for the first time in Brazil the natural occurrence of these species of fungi in this tick, and will be used to conduct bioassays to evaluate the pathogenicity and virulence of these strains for ticks of the genus Boophilus microplus. This revised version was published online in June 2006 with corrections to the Cover Date.     

Virulence of entomopathogenic fungi Beauveria bassiana and Metarhizium anisopliae against red palm weevil,Rhynchophorus ferrugineus (Olivier)

Nineteen different isolates of the entomopathogenic fungi Beauveria bassiana sensu lato (s.l.) and Metarhizium anisopliae s.l. (Ascomycota: Hypocreales), recovered from different soil samples (field crops, fruit orchards, vegetable fields and forests) and insect cadavers were tested against Rhynchophorus ferrugineus (Olivier) (Coleoptera: Curculionidae) at two different spore concentrations (1 × 10⁷ and 1 × 10⁸ conidia mL^?1). Three isolates of B. bassiana and two of M. anisopliae gave >88 % larval and >75 % adult mortality of R. ferrugineus on their highest dose rate respectively. More sporulating cadavers (mycosis) resulted from a high dose rate compared to low dose on both life stages of R. ferrugineus. The current study confirmed the lethal action of B. bassiana and M. anisopliae isolates with mortality levels usually directly proportional to the conidial concentration. This study further confirmed that the isolates recovered from R. ferrugineus dead cadavers gave more mortality compared to the other sources. In the virulence assay two isolates of B. bassiana caused the highest percentage of both larval and adult mortality at all exposure intervals which suggest that they may be the most promising for use in sustainable management programs aimed at microbial control in date palm orchards.     

Transformants of Metarhizium anisopliae sf. anisopliae overexpressing chitinase from Metarhizium anisopliae sf. acridum show early induction of native chitinase but are not altered in pathogenicity to Manduca sexta

Extracellular chitinase activity has been implicated in the pathogenesis of several fungal infections. Following induction with chitin, the insect pathogens Metarhizium anisopliae sf. acridum ARSEF strain 324 and Metarhizium anisopliae sf. anisopliae ARSEF strain 2575 secrete 44-kDa basic and acidic isoforms of endochitinase, respectively. The gene from strain 324 (Chit1) was cloned and inserted into the genome of strain 2575 under the control of Aspergillus regulatory elements such that transgenic 2575 (2575-Chit(+)) expressed CHIT1 in a noninducing medium (i.e., not containing chitin). Isoelectric focusing followed by a zymogram technique revealed that neither wild-type 2575 nor 2575-Chit(+) produced significant amounts of the native 2575 acidic chitinase in a noninducing medium. However, in a chitin-containing medium, 2575-Chit(+) produced the native chitinase earlier than strain 2575, soon after secretion of CHIT1. We hypothesize that this is due to the production of soluble inducers following chitin hydrolysis by CHIT1 and that M. anisopliae uses enzymes expressed at low levels to sense the nature of the polymeric nutrient present in the immediate environment. However, the chitinase overproducers did not show altered virulence to caterpillars (Manduca sexta) compared to the wild-type fungus, suggesting that wild-type levels of chitinase are not limiting for cuticle penetration.     

Persistence of Beauveria bassiana sensu lato and Metarhizium anisopliae sensu lato in Vermont (USA) forest soil

Persistence of granular formulations of Beauveria bassiana sensu lato, strains GHA726 and ERL1170, and Metarhizium anisopliae sensu lato, strains ERL824 and ERL701, applied to forest soil was documented. One formulation was prepared by producing fungi on millet and at application adding cooked, dried millet to provide additional nutrients for fungal growth. The other was made by producing fungi on corn starch ‘packing peanuts’, a biodegradable packaging material, adding additional packing peanuts as a nutrient base. The trial was conducted in three sites in a forest predominating in sugar maple (Acer saccharum) in Underhill, VT, USA. In each site, 33 dominant sugar maples were randomly selected. A 1-m² plot located 1 m from the bole of the tree was established. Soil samples were collected before application, and 1 h, 2, 4, 8, 12 and 16 wk post-application. Fungal levels were estimated based on number of colony-forming units (CFUs). A significant increase in CFUs was observed 2 wk post-application in plots treated with isolates GHA726, ERL1170 and ERL824 as a result of fungal reproduction on nutrients in the formulations. Evidence of greater persistence for the B. bassiana than the M. anisopliae isolates was observed, based on CFU levels over time. Isolates formulated with millet proliferated more than those on packing peanuts. Use of entomopathogenic fungi in forest soil has potential for managing soil-dwelling insect pests such as pear thrips, Taeniothrips inconsequens, and the black vine weevil, Otiorhynchus sulcatus, though the type of formulation and the specific isolate used must be selected carefully.     

Evaluation of Beauveria bassiana and Metarhizium anisopliae for Controlling Chilo partellus (Lepidoptera: Crambidae) in Maize

Maize (variety Katumani) was planted in a greenhouse and plants were infested with 20 Chilo partellus second instar larvae 3 and 4 weeks after plant emergence. One isolate of Beauveria bassiana (BB-01) and four isolates of Metarhizium anisopliae (PPRC-4, PPRC-19, PPRC-61 and EE-01) were sprayed onto the leaf whorl at 2×10⁸ conidia/mL 24 h after infestation. Leaf damage by the larvae was greatly reduced by the treatments. The mean daily temperature and relative humidity in the greenhouse ranged from 10 to 35°C and 30 to 90%, respectively. The growth of infested unsprayed plants was less than that of fungi treated plants. Stem tunneling (1-5%), deadheart (0-33%), number of attacked nodes (0.3-2.5) and holes (0.2-3.3) were also reduced in plants sprayed with conidial suspensions. Isolates PPRC-4, PPRC-19 and PPRC-61 seemed to be the best candidates for further development.     

Effect of temperature on vegetative growth among isolates of Metarhizium anisopliae and M. flavoviride

Effects of temperature on vegetative growth on a semi-synthetic medium of 22 isolates of Metarhizium anisopliae and 14 isolates of M. flavoviride were determined. The majority of isolates of both species grew between 11 and 32°C; several isolates grew at 8 and 37 °C. None of the isolates grew at 40 °C. Relative growth rate, calculated from the maximum growth rate for each isolate, was significantly affected by temperature and isolate, with significant isolate * temperature interactions. The maximum absolute growth rates among the isolates ranged from 2.5 mm to 5.9 mm/day. Optimal temperatures were generally between 25 and 32 °C with several isolates exhibiting optimal growth at temperatures as high as 32 °C. Overall, relative growth rates were greater in isolates of M. anisopliae than M. flavoviride at temperatures of 25 °C or lower; conversely mean relative growth rates were greater in M. flavoviride than M. anisopliae at temperatures higher than 25 °C. However, the two most cold tolerant isolates at 8 °C were M. flavoviride and the three most heat tolerant at 35 °C were M. anisopliae. Since temperature growth responses varied considerably between isolates, strain selection according to thermal tolerance may be warranted when choosing a strain for development as a microbial control agent.This revised version was published online in October 2005 with corrections to the Cover Date.     

Pathogenicity of Beauveria bassiana,Metarhizium anisopliae and Serratia marcescens to the banana weevil Cosmopolites sordidus

Two exotic fungal isolates, one of Beauveria bassiana (268–86) and another of Metarhizium anisopliae (100–82), three local isolates of B. bassiana (isolates I, II, III) and one of the entomogenous bacteria Serratia marcescens, were tested for pathogenicity against the banana weevil Cosmopolites sordidus. All four isolates of B. bassiana and the one of M. anisopliae were found to be pathogenic to third—instar larvae of C. sordidus, causing mortalities of 98–100% by 9 days post—exposure to dry fungal spores. M. anisopliae was the least pathogenic to larvae with LT₅₀ of 4.2 days, compared to 3.5, 3.3, 3.6 and 4.0 respectively for isolates I, II, III and 268–86. B. bassiana was also pathogenic to adult C. sordidus, causing mortalities varying from 63–97% by 35 days post—exposure depending on isolate. As for larvae M. anisopliae exhibited low pathogenicity for the adult C. sordidus. In general, all the fungi tested were less pathogenic to adult weevils (LT₅₀ = 17.5; 12.5; 8.0 and 22.0 days) for isolates I, II, III and 268–86 respectively, while isolate 100–82 failed to kill 50% of adults even by 35 days post—exposure. Incubation of dead weevils in a moist environment led to development of surface mycelia starting from intersegmental junctions. Histopathology revealed extensive destruction of internal organs by hyphae which invaded most of the organs. The LT₅₀ for S. marcescens against C. sordidus larvae was 2.8 days. However, the bacterium did not kill adult C. sordidus even at 10 times the concentration applied on larvae.     

Trehalose-hydrolysing enzymes of Metarhizium anisopliae and their role in pathogenesis of the tobacco hornworm,Manduca sexta

Trehalose is the main haemolymph sugar in most insects including the tobacco hornworm, Manduca sexta, and is potentially a prime target for an invading pathogenic fungus. There was considerably more trehalose-hydrolysing activity in the haemolymph of caterpillars infected with Metarhizium anisopliae than in controls. This appeared to be due primarily to additional isoforms; one of which could also hydrolyse maltose and was designated an alpha-glucosidase. A comparable isoform was identified in in vitro culture of the fungus, supporting a fungal origin for the in vivo enzyme. The in vitro fungal enzyme, alpha-glucosidase-1 (alpha-gluc-1), was purified to homogeneity and partially characterised. A study with the trehalase inhibitor trehazolin and C14 trehalose suggested that extracellular hydrolysis is important for fungal mobilisation of trehalose. Haemolymph glucose increases significantly during mycosis of tobacco hornworm larvae by M. anisopliae, consistent with the hydrolysis of trehalose by extracellular fungal enzymes. The implications for the host insect are discussed.     

Effects of Beauveria bassiana and Metarhizium anisopliae on mortality, fecundity and egg fertility of Tetranychus evansi

Abstract:  The susceptibility of various developmental stages of Tetranychus evansi Baker & Pritchard (eggs, larvae, protonymphs, deutonymphs and adults) to the entomopathogenic fungi Metarhizium anisopliae (Metschnikoff) Sorokin and Beauveria bassiana (Balsamo) Vuillemin was evaluated under laboratory conditions. Three concentrations (3.0 × 10⁶, 1.0 × 10⁷ and 1.0 × 10⁸ conidia/ml) of both fungi were used for each stage. The effect of fungal infection on fecundity and egg fertility was also investigated using both fungal species. Deutonymphs that survived the infection and developed into adult females were allowed to oviposit. Adults and deutonymphs were more susceptible to fungal infection than larval and protonymphal stages at all the concentrations. Nevertheless, the concentration level influenced the mortality of the different mite stages. Eggs were also susceptible to fungal infection and mortality was dose-dependent. Fungus-treated female mites laid fewer eggs than the controls but there was no significant difference in egg hatchability between the treatments.     

Role of cuticle-degrading enzymes of Beauveria bassiana and Metarhizium anisopliae in virulence on Plodia interpunctella (Lepidoptera,Pyralidae) larvae

Entomopathogenic fungi (EPF) are important biological control agents in pest management programs in agroecosystems against insect pests. EPF such as Beauveria bassiana (Bals.) Vuillemin and Metarhizium anisopliae (Metchn.) Sorokin produce a wide range of extracellular enzymes involved in disturbance of the first barrier in the insect cuticle comprising proteins, chitin, and lipids. Realizing relationships between the expression of these enzymes and fungal virulence might aid in development of effective mycoinsecticides. The virulence of B. bassiana (isolates TV and OZ1) and M. anisopliae (isolate CS1) were investigated on Plodia interpunctella (Hübner) larvae in this study. The third instar larvae were immersed in a suspension containing 1 × 10⁸ conidia mL^?1 of fungal conidial inoculum. The results revealed that all three fungal isolates caused mortality in larvae, but there was a considerable variation in their virulence. Total proteinase, exochitinase and lipase assays were done for these isolates. The TV isolate with the highest mortality with 41.7%, had the highest level of specific activity of exochitinase, protease, and lipase with 0.148, 0.654, and 0.190 U. mg^?1 protein, respectively. In the current study, a positive correlation was determined between the virulence of fungal isolates and the activities of protease and lipase, but this link was not significant for exochitinase. Our results demonstrated that extracellular enzymes, particularly protease and lipase, may play a crucial role in the virulence of these fungal isolates against P. interpunctella larvae.     

Potential of Metarhizium anisopliae and Beauveria bassiana to control Dinoderus porcellus (Coleoptera: Bostrychidae) infesting yam chips

The beetle Dinoderus porcellus Lesne is a serious storage insect pest that causes important losses by destroying stocks of yam chips. In the aim to found an alternative control method to the use of synthetic insecticides for its management, the virulence of the entomopathogenic fungi Beauveria bassiana (Balsamo) Vuillemin (isolate Bb115) and Metarhizium anisopliae (Metschnikoff) Sorokin (isolate Met 31) against adults of D. porcellus was evaluated under laboratory conditions (25 ± 2 °C and 70 ± 5% RH). Then, the effectiveness of the most virulent entomopathogenic fungus as biological agent against D. porcellus was assessed under farmer storage conditions. For each entomopathogenic fungus isolate, four conidial concentration (0, 10⁵, 10⁷, and 10⁹ conidia/mL) at the dose of 1 µL were inoculated topically on D. porcellus adults (3–5 days old). Observations focused on insect mortality, cadaver sporulation and weight loss of yam chips. Lethal dose and lethal time values were estimated using probit analysis. Both fungal isolates at all conidial dose caused more than 50% mortality on day 7, with the highest mortality (94.44%) achieved using B. bassiana at the 10⁹ conidia/mL. LT₅₀ values for B. bassiana and M. anisopliae isolates were 2.63 and 3.35 days, respectively, while their LT₉₀ values were 6.15 and 9.87 days, respectively. Yielding the lower LD₉₀ values and the highest rates of cadaver sporulation, B. bassiana isolate appeared as the most virulent against D. porcellus. After 3 months of storage, comparatively to the control, the B. bassiana isolate at the highest conidial dose (10⁹ conidia/mL) significantly reduced D. porcellus populations, and weight loss of yam chips. This study revealed the potential of B. bassiana and M. anisoplae isolates as biological control agent against D. porcellus for yam chips protection.     

Influence of whey permeate and millet as substrates on thermotolerance of Beauveria bassiana and Metarhizium anisopliae conidia during storage

Conidia from Beauveria bassiana and Metarhizium anisopliae, produced in quarter-strength Sabouraud dextrose agar amended with yeast extract, whey permeate, and millet agar, were exposed to 45°C for 90 min prior to and at 30 d post-storage at 25°C. B. bassiana produced in whey permeate or millet had better thermotolerance than the other treatments after the storage.     

Cosmopolites sordidus (Germar) susceptibility to indigenous Cameroonian Beauveria bassiana (Bals.) Vuill. and Metarhizium anisopliae (Metsch.) isolates

Management of the banana root borer (BRB), Cosmopolites sordidus (Germar; Coleoptera: Curculionidae), remains a challenge in banana and plantain production worldwide. Synthetic pesticides remain the most widely used solution while mycoinsecticides are increasingly being recommended. In this study, we selected indigenous isolates of Beauveria bassiana and Metarhizium anisopliae collected from plantain fields in Cameroon, and tested them in the laboratory for their viability, pathogenicity and virulence against all C. sordidus life stages. Of 13 isolates initially screened for spore germination and pathogenicity to adult weevils in conidial suspension of 3.2 × 10⁸ conidia/ml, eight isolates with high to moderate germination and highest weevil mortality were selected for dose–response bioassays with four concentrations per isolate: 3.2 × 10², 3.2 × 10⁴, 3.2 × 10⁶ and 3.2 × 10⁸ conidia/ml. The virulent isolates from adult bioassays were tested with eggs, larva and pupae in conidial suspension of 3.2 × 10⁸ conidia/ml. Isolates performance depended on insect life stage with significantly high pathogenicity and virulence against larval, pupa and adult stages. The Beauveria isolate BIITAC6.2.2 caused the highest mortality rates followed by MIITAC1.1.5. Lethal times and lethal concentrations were relatively low for the three M. anisopliae isolates and three B. bassiana isolates which were the best isolates in almost all insect life stages. Apart from being effective in multiple life stages, these isolates were transmitted horizontally from one stage to another when eggs and pupae were treated. The implication of these findings for integrated management of the BRB, and potential biopesticides development and commercialization are discussed.     

Lethal effects of Gliocladium virens,Beauveria bassiana and Metarhizium anisopliae on the malaria vector Anopheles albimanus (Diptera: Culicidae)

Control of Anopheles albimanus, the main vector of malaria on the coast of the State of Chiapas, is based mainly on application of chemical insecticides, which has resulted in resistance to most registered insecticides. Strategies for biological control may provide sustainable alternatives. We report on the lethal effects of a native isolate of Gliocladium virens on An. albimanus larvae and adults, compared to that of strains of Beauveria bassiana and Metarhizium anisopliae. Conidial suspensions of G. virens, B. bassiana and M. anisopliae cultured on Sabouraud agar were tested in bioassays with An. albimanus larvae and adults. Mosquito larvae were more susceptible to all fungi, compared to adults. On early and late instar larvae, M. anisopliae showed the most pathogenic effect (LC₅₀ of 1.4×10⁵ conidia/mL in early instars; 1.1×10⁵ conidia/mL in late instars), followed by G. virens (LC₅₀ of 3.3×10⁵ conidia/mL in early instars and 3.5×10⁶ conidia/mL in late instars). Metarhizium anisopliae sensu lato and the native G. virens could be considered good choices for An. albimanus control in southern Mexico.     

Effect of Beauveria bassiana and Metarhizium anisopliae (Deuteromycetes) upon the coffee berry borer (Coleoptera: Scolytidae) under field conditions

The effect of three strains of the fungus Beauveria bassiana (Balsamo) Vuillemin and two strains of Metarhizium anisopliae (Metschnikoff) Sorokin upon the coffee berry borer, Hypothenemus hampei (Ferrari), was studied in three coffee farms at different altitudes (450-1,100 m above sea level) in Soconusco, Chiapas, Mexico. The maximum average percentage mycosis varied according to altitude. At 450 m asl (El Rincon) mycosis was 14.3% for B. bassiana and 6.3% for M. anisopliae; at 880 m asl (Santa Anita) mycosis was 40.6% for B. bassiana and 12.6% for M. anisopliae, and at 1,100 m asl (Alpujarras) 33.9% for B. bassiana and 22. 1% for M. anisopliae. The effect of fungal mycosis through time was not significant (P > 0.01) in any of the farms, but there was a significant difference between the strains of the fungus (P < 0.01); the best strains being Bb25 and Ma4 at the lower altitude, Bb26 and Ma4 for the middle altitude and Bb26 and Ma4 at the higher altitude. Environmental factors such as temperature, relative humidity and rain were not correlated with the percentage mycosis caused by B. bassiana and M. anisopliae. However, in the case of B. bassiana there was a significant, positive correlation (P < 0.01) between the infestation levels of the pest and the mycosis response of the entomopathogen.