Laboratory bioassays of entomopathogenic fungi for control of Delia radicum (L.) larvae

Laboratory soil bioassays were performed at economic field rates for in-furrow (3.85 x 10(6)spores/g dry soil) and broadcast (3.85 x 10(5)spores/g dry soil) applications with three isolates of Metarhizium anisopliae (F52, ATCC62176, and ARSEF5520) and one isolate of Beauveria bassiana (GHA). All isolates tested were infective to second instar Delia radicum (L.). The conditionally registered M. anisopliae isolate (F52) performed best killing an average of 85 and 72% of D. radicum larvae at the high and low concentration, respectively. The mean LC50 and LC95 of F52 against second instar D. radicum was 2.7 x 10(6) and 1.8 x 10(8)spores/g dry soil, respectively. The use of F52 in an integrated management program is discussed.     

Pathogenicity of Beauveria bassiana,Metarhizium anisopliae (Deuteromycotina: Hyphomycetes), and other entomopathogenic fungi against Lygus lineolaris (Hemiptera: Miridae)

The pathogenicity of 32 fungal isolates from the genera of Beauveria, Verticillium, Paecilomyces, Metarhizium, Mariannaea, and Hirsutella to second-instar tarnished plant bug, Lygus lineolaris (Palisot de Beauvois), was tested under laboratory conditions. These isolates originated from various insect hosts and substrates from France, Denmark, Austria, Italy, Turkey, Syria, and the United States. A single exposure concentration (1 x 10(7) conidia/ ml) assay for each isolate was first conducted by immersing the insects in 10 ml of a fungal suspension for 5s. These were followed by concentration-mortality assays on five of the most pathogenic isolates using four test concentrations ranging from 2 x 10(4) to 2 x 10(7) conidia/ml. B. bassiana 726 (Bemisia-passaged GHA strain) was used as a standard for comparison in all of the assays. Among the test isolates, three produced mortality not significantly different from the water control. Mortality ranged from 35 to 98% among the other 29 isolates. The LC50 values of the five most pathogenic isolates ranged from 0.8 to 5.0 x 10(5) conidia/ml. The LT50 values for these isolates ranged from 6.0 to 6.9, 3.1 to 5.1, and 2.5 to 4.0 d for concentrations of 2 x 10(5), 2 x 10(6), and 2 x 10(7) conidia/ml, respectively. Two strains of B. bassiana (ARSEF 1394,5665) and one M anisopliae (ARSEF 3540) were more pathogenic to the nymphs than the standard, having significantly lower LC50 and LT50, values. Our results demonstrated that several genera of entomopathogenic fungi have promise as microbial control agents against L. lineolaris.     

Pathogenicity of three formulations of entomopathogenic fungi for control of adult Haematobia irritans (Diptera: Muscidae)

Powder formulations of three species of entomopathogenic fungi were evaluated for their pathogenic effect upon adult horn flies, Hematobia irritans (L.) (Diptera: Muscidae). Flies were treated with conidia and blastospores of the entomopathogenic fungi Beauveria bassiana (Bals.) Vuill. (strain GHA), Metarhizium anisopliae (Metschnikoff) Sorokin (strain ESCI), and Paecilomyces fimosoroseus (Wize) Brown & Smith (strain ARSEF 3581) in the laboratory. At 4 d postexposure, flies treated with B. bassiana had an average of 98.4% mortality versus 43.5% from treatment with M. anisopliae and 13.0% from treatment with P. fiimosoroseus. At 7 d postexposure, flies treated with B. bassiana had an average of 100.0% mortality compared with 73.0% from treatment with M. anisopliae and 33.3% from treatment with P.fumosoroseus. Mean lethal time (LT50) was 2.70, 4.98, and 7.97 d for B. bassiana, M. anisopliae, and P. fiumosoroseus, respectively. Entomopathogenic fungi such as B. bassiana and M. anisopliae may have the potential for controlling populations of horn flies. These studies indicate that B. bassiana and M. anisopliae were not only pathogenic to adult horn flies, but they caused mortality in a short time.     

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.     

Mortality of Delia floralis, Galleria mellonella and Mamestra brassicae treated with insect pathogenic hyphomycetous fungi

Abstract:  The susceptibility of Delia floralis eggs, neonates and larvae and the susceptibility of Galleria mellonella and Mamestra brassicae larvae to seven different Norwegian isolates of the insect pathogenic, hyphomycetous fungi Tolypocladium cylindrosporum , Metarhizium anisopliae and Beauveria bassiana , were investigated. Metarhizium anisopliae isolate ARSEF 5520 was highly virulent to G. mellonella larvae and caused 100% mortality when tested at a concentration of 3.6 × 10⁶ conidia/ml. The same M. anisopliae isolate was not virulent to D. floralis larvae. Isolates of T.cylindrosporum , were equally virulent to G. mellonella and D. floralis causing up to 36.0% mortality of larvae. It is suspected, however, that the use of grated rutabaga as a food source in the D. floralis bioassay reduced the fungal virulence of both M. anisopliae and T. cylindrosporum to D. floralis . Among three T. cylindrosporum isolates tested at a concentration of 1.0 × 10⁷ conidia/ml against eggs of D. floralis none of them reduced the hatching percentage. One isolate, ARSEF 5525 did, however, significantly reduce the longevity of neonates. Beauveria bassiana isolates ARSEF 5510 and ARSEF 5370 tested at a concentration of 1.0 × 10⁷ conidia/ml resulted in M. brassicae mortality levels of 70.0 and 55.0%, respectively. The B. bassiana isolate ARSEF 5557, however, was not virulent to M. brassicae . Among the three isolates tested against M. brassicae the two virulent isolates produced a red pigment, probably oosporein, when cultured in Sabouraud dextrose agar.     

Susceptibility of Sitophilus zeamais (Motsch.) (Coleoptera: Curculionidae) and Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae) to Entomopathogenic Fungi from Ethiopia

The efficacy of 13 isolates of entomopathogenic fungi belonging to Beauveria , Metarhizium or Paecilomyces spp. was assessed against Sitophilus zeamais (Coleoptera: Curculionidae) and Prostephanus truncatus (Coleoptera: Bostrichidae) using a total immersion bioassay technique in the laboratory. Fungi were applied at concentrations of 1 ×10 7 and 1 ×10 8 conidia mL -1 for P. truncatus and S. zeamais , respectively. All isolates tested were virulent to P. truncatus (98-100% mortality, and median survival time (MST) ranged from 2.85-4.05 days). Metarhizium anisopliae and B. bassiana were also virulent to S. zeamais (92-100% mortality, MST ranged from 3.58-6.28 days). The isolate of Paecilomyces sp. was found to be the least virulent against S. zeamais , causing only 26.32 ±4.29% mortality with MST of 10.38 ±0.29 days. P. truncatus proved more susceptible to the entomopathogenic fungi tested than S. zeamais . One M. anisopliae (PPRC-EE) and three B. bassiana isolates (PPRC-HH, PPRC-9609 and PPRC-9614) were selected for further study and dose-mortality relationships were assessed on S. zeamais . The tested concentrations ranged from 1 ×10 4 -1 ×10 7 conidia mL -1 . M. anisopliae (PPRC-EE) showed the lowest LC 50 (3.39 ×10 5 conidia mL -1 ) followed by B. bassiana PPRC-HH (2.04 ×10 6 conidia mL -1 ). PPRC-9609 and PPRC-9614 showed slight differences in LC 50 but not at LC 90 . The results revealed the higher potency of M. anisopliae as compared with the B. bassiana isolates tested. The study suggests that the use of entomopathogenic fungi may hold promise as an alternative method to control pests of stored-products in Ethiopia.     

A new bioassay method reveals pathogenicity of Metarhizium anisopliae and Beauveria bassiana against early stages of Capnodis tenebrionis (Coleoptera; Buprestidae)

We used a newly developed bioassay method to demonstrate for the first time the potential of the entomopathogenic fungi Beauveria bassiana and Metarhizium anisopliae to be used for the control of neonate larvae of Capnodis tenebrionis, a major threat to stone-fruit orchards in several countries. Four B. bassiana and four M. anisopliae isolates were all pathogenic for neonate larvae of C. tenebrionis; mortality rates 10 days after inoculation by dipping in a suspension with 10(8)conidia/ml varied from 23.5% to 100%. Three of the four M. anisopliae isolates caused 100% mortality. In most cases, postmortem hyphal growth and sporulation of M. anisopliae or B. bassiana was observed covering the larvae in their galleries. The eight isolates were also evaluated for pathogenicity to C. tenebrionis eggs at the same dosage. Only two B. bassiana isolates caused significant egg hatching reduction of 84.5% and 94.5%. Our results indicate that M. anisopliae and B. bassiana may be considered as promising for a new approach to prevent larval infestations by C. tenebrionis.     

Development of a Spray-drying Technique for Submerged Spores of Entomopathogenic Fungi

The stability of blastospores or submerged conidia of entomopathogenic fungi is one of the key problems associated with the practical use of fungal biopreparations. A spray-drying technique was developed which allows the drying of blastospores and/or submerged conidia, here called submerged spores, without a significant loss of viability and with only a slight delay in eY cacy. The method was tested successfully using the fungal species Metarhizium anisopliae , M. flavoviride, Beauveria bassiana and Paecilomyces fumosoroseus . For all experiments, a laboratory spray dryer was used. The optimum inlet and outlet temperatures were found to be 64 2oC and 48 2oC respectively. The best protective agent for submerged spores was skimmed milk powder at concentrations of 10 or 20%. The addition of sugars, especially 2.5% sugar-beet syrup, slightly improved the viability after spray-drying. Submerged spores of eight isolates of M. anisopliae, M. flavoviride, B. bassiana and P. fumosoroseus were suspended in 20% skimmed milk powder and 2.5% sugar-beet syrup, and spray-dried. Germination rates of about 90% were achieved, which were comparable to those of freshly produced submerged spores. Finally, the virulences of spray-dried submerged spores of M. anisopliae (Ma 97) and M. flavoviride (Mfl 5) were tested in bioassays using third- and fourth-instar nymphs of the African locust, Locusta migratoria . In contrast to M. flavoviride , there was no significant diVerence in the median lethal time between spray-dried and fresh submerged spores of M. anisopliae . The investigations demonstrated that spray-drying is possible to preserve sensitive submerged spores of entomopathogenic fungi.     

Pathogenicity of hyphomycet fungi to aphids Aphis gossypii Glover and Myzus persicae (Sulzer) (Hemiptera: Aphididae)

The aphids Aphis gossypii and Myzus persicae are cosmopolitan, poliphagous and damage cultivated plants. The effects of the entomopathogenic fungi Beauveria bassiana (isolate IBCB 66), Metarhizium anisopliae (isolate IBCB 121), Paecilomyces fumosoroseus (isolate IBCB 141) and Lecanicillium (= Verticillium) lecanii (isolate JAB 02) on third instar nymphs of A. gossypii and M. persicae were evaluated in the laboratory at 25 degrees C, 70 +/- 10% RH and 12h photophase. The aphids were transferred to petri dishes with a foliar disk (cotton or pepper) with a layer of 1 cm tick of agar-water. The fungi were applied in a suspension containing 1.0 x 106 to 1.0 x 108 conidia/ml. In the control treatment 1 ml of sterilized water was added to the foliar disks. The mortality of aphids was evaluated daily. B. bassiana and M. anisopliae caused 100% mortality at the seventh day after inoculation, for both species. L. lecanii was the fungus that provided mortality later in the aphids and M. persicae was more susceptible to both fungi than A. gossypii.     

Selection of entomopathogenic fungi for the control of the western corn rootworm Diabrotica virgifera virgifera

Abstract:  The western corn rootworm Diabrotica virgifera virgifera Le Conte (Col., Chrysomelidae), a serious pest of maize, has been recently introduced into Europe. Several approaches for its control are presently under investigation including microbial agents. During a field survey in Hungary in 2005, naturally occurring entomopathogenic fungi were found to attack this pest. These novel isolates together with standard isolates were tested for virulence against D. v. virgifera larvae and adults. Twenty strains of Metarhizium anisopliae , Beauveria bassiana and Beauveria brongniartii were used in bioassays in the laboratory. Larvae and adults were dipped into a spore suspension with a concentration of 1 × 10⁷ conidia (con.)/ml. They were kept for 14 days at 22°C (±2°C) and 70% relative humidity. The number of infected larvae and adults were counted and infection rates were calculated. Adults were significantly more susceptible to entomopathogenic fungi than larvae. The most virulent isolate infected about 47% of larvae ( M. anisopliae Ma2277), whereas the infection rate in adults was up to 97% ( M. anisopliae Ma2275). Isolates of M. anisopliae caused significantly higher mortalities than isolates of B. brongniartii and B. bassiana . Most of the adult beetles were killed within 12 days. Isolates from D. v. virgifera were more virulent than those from other hosts.     

Selection of Beauveria bassiana (Bals.) Vuill. and Metarhizium anisopliae (Metsch.) Sorok. isolates against Alphitobius diaperinus (Panzer) (Coleoptera: Tenebrionidae)

This study was carried out to evaluate entomopathogenic fungi isolates as microbial control agents ofthe lesser mealworm, Alphitobius diaperinus (Panzer). Larvae and adults were inoculated with conidial suspension of 99 isolates of Beauveria bassiana (Bals.) Vuill. and Metarhizium anisopliae (Metsch.) Sorok. (10(5) to 10(9) conidia/ml). Vegetative growth on culture media and sporulation on culture media, cooked rice and lesser mealworm cadavers were also evaluated. Isolates of B. bassiana were more effective than the M. anisopliae isolates and larvae were more susceptible than adults. The isolates UNIOESTE 04 and UNIOESTE 02 were originally obtained from adults of the lesser mealworm and were the most efficient isolates. In addition, UNIOESTE 04 showed high level of sporulation on different culture media and is considered a potential useful tool to lesser mealworm control.     

Effect of temperature and poultry litter in Beauveria bassiana (bals.) Vuill. and Metarhizium anisopliae (Metsch) virulence against the lesser mealworm Alphitobius diaperinus (Panzer) (Coleoptera: Tenebrionidae)

This study was carried out to evaluate the influence of temperature and poultry litter on germination vegetative growth virulence and conidial production of Beauveria bassiana (Bals.) Vuill. and Metarhizium anisopliae (Metsch.) isolates on larvae and adults of the lesser mealworm (Alphitobius diaperinus) (Panzer). The vegetative growth and conidial production were evaluated on culture media. Virulence was studied submerging larvae and adults in a conidial suspension (1 x 10(8) conidia/ml). All the experiments were carried out in growth chamber (26 degrees C and 32 degrees C and 14h photophase). Fungus-killed insects were daily collected and used for microscopic conidial counts. The poultry litter effect was evaluated by submerging the insects in a fungal suspension (10(8) conidia/ml) and then transferring them to cups containing poultry litter (new and used). B. bassiana isolates were more sensitive than M. anisopliae to high temperature because conidia viability, vegetative growth and virulence were negatively affected (P < 0.05). The conidial production was higher to B. bassiana in 26 degrees C (7 to 11 x 10(8) conidia/larval cadaver and 8 x 10(8) conidia/adult cadaver) (P < 0,05). Larval stage was about 10 times more sensitive to M. anisopliae at 26 degrees C than adults stage. Regarding B. bassiana, differences on sensitivity between larval stages and adults were not observed at this temperature. However, at 32 degrees C, larval stage was more sensitive for CB116 and UEL50 isolates. Mortality was higher when larvae and adults (15.7 and 66.7% respectively) were treated by B. bassiana and maintained on new poultry litter at 26 degrees C) (P < 0.05).     

Characterization and virulence of Beauveria spp. recovered from emerald ash borer in southwestern Ontario, Canada

The emerald ash borer (EAB), Agrilus planipennis (Coleoptera: Buprestidae), is an invasive wood boring beetle that is decimating North America's ash trees (Fraxinus spp.). To find effective and safe indigenous biocontrol agents to manage EAB, we conducted a survey in 2008-2009 of entomopathogenic fungi (EPF) infecting EAB in five outbreak sites in southwestern Ontario, Canada. A total of 78 Beauveria spp. isolates were retrieved from dead and mycosed EAB cadavers residing in the phloem tissues of dead ash barks, larval frass extracted from feeding galleries under the bark of dead trees. Molecular characterization using sequences of the ITS, 5' end of EF1-α and intergenic Bloc region fragments revealed that Beauveria bassiana and Beauveria pseudobassiana were commonly associated with EAB in the sampled sites. Based on phylogenetic analysis inferred from ITS sequences, 17 of these isolates clustered with B. bassiana, which further grouped into three different sub-clades. However, the combined EF1-α and Bloc sequences detected five genotypes among the three sub-clades. The remaining 61 isolates clustered with B. pseudobassiana, which had identical ITS sequences but were further subdivided into two genotypes by variation in the EF1-α and Bloc regions. Initial virulence screening against EAB adults of 23 isolates representing the different clades yielded 8 that produced more than 90% mortality in a single concentration assay. These isolates differed in virulence based on LC(50) values estimated from multiple concentration bioassay and based on mean survival times at a conidia concentration of 2×10(6) conidia/ml. B. bassiana isolate L49-1AA was significantly more virulent and produced more conidia on EAB cadavers compared to the other indigenous isolates and the commercial strain B. bassiana GHA suggesting that L49-1AA may have potential as a microbiological control agent against EAB.     

Susceptibility of adult Aethina tumida (Coleoptera: Nitidulidae) to entomopathogenic fungi

Aethina tumida Murray (Coleoptera: Nitidulidae) is an invasive parasite species in populations of honey bees, Apis mellifera L. Aiming toward substitution of chemical control, we here identified a naturally occurring fungal pathogen of adult A. tumida from its endemic range in South Africa [Metarhizium anisopliae (Metschnikoff) Sorokin variety anisopliae strain FI-203]. The susceptibility of adult beetles (n = 400) to this fungus and to three other generalist entomopathogenic fungal isolates [Metarhizium anisopliae, Beauveria bassiana (Balsamo) Vuillemin, and Hirsutella illustris Minter & Brady] was assessed using spore suspension bioassays. The data revealed significantly increased mortality in the B. bassiana (74.00 +/- 8.94%) and M. anisopliae variety anisopliae (28.00 +/- 16.43%) tests but not in the H. illustris (2.00 +/- 4.47%) and M. anisopliae (12.00 +/- 8.37%) groups. The results indicate a potential for entomopathogenic fungi as an alternative control of A. tumida.     

Selection of Beauveria bassiana sensu lato and Metarhizium anisopliae sensu lato isolates as microbial control agents against the boll weevil (Anthonomus grandis) in Argentina

The boll weevil (Anthonomus grandis) is the main pest of cotton in the Americas. The aim of this work was to evaluate isolates of the entomopathogenic fungi Beauveria bassiana sensu lato and Metarhizium anisopliae sensu lato virulent against A. grandis. Screening was performed to evaluate the pathogenicity of 28 isolates of M. anisopliae s.l. and 66 isolates of B. bassiana s.l. against boll weevil adults. To select the isolates, LC(50) values of the most virulent isolates were calculated, and compatibility between the fungi and insecticides was studied. In addition, the effects of these isolates on the feeding behavior of the adults were evaluated. Isolates Ma 50 and Ma 20 were the most virulent against A. grandis and their LC(50) values were 1.13×10(7) and 1.20×10(7) conidia/ml, respectively. In addition, these isolates were compatible with pyrethroid insecticides, but none with endosulfan. On the other hand, infected females reduced the damage caused by feeding on the cotton squares and their weight gain. This shows that entomopathogenic fungi cause mortality in the insects, but also these fungi could influence the feeding behavior of the females. In summary, these results indicate the possibility of the use of M. anisopliae s.l. as a microbiological control agent against boll weevils. Also, this species could be included in an Integrated Pest Management program.     

Laboratory evaluation of entomopathogenic fungi against larvae and adults of onion maggot (Diptera: Anthomyiidae)

Laboratory experiments were done to measure the susceptibility of larvae and adults of the onion maggot, Delia antiqua (Meigen) (Diptera: Muscidae: Anthomyiidae) to 27 isolates of entomopathogenic fungi from four genera [Beauveria Vuillemin, Lecanicillium (Petch) Zare & W. Gams, Metarhizium Sorokin, and Paecilomyces Bainier]. A novel bioassay was developed for D. antiqua larvae by using a diet based on mixed vegetable powder. When evaluated in a virulence screen, the fungal isolates caused less mortality of D. antiqua larvae than adults. Only three isolates caused > 50% mortality of larvae, whereas 12 isolates caused > 50% mortality of adults. Fungal species was a statistically significant factor affecting the mortality of larvae but not of adults. The fungal isolates causing the most mortality of larvae tended to belong to Metarhizium anisopliae (Metschnikoff) Sorokin. Two M. anisopliae isolates (389.93 and 392.93) were evaluated in dose-response bioassays. The median lethal concentrations of the isolates against larvae were 6.1 x 10(7) conidia ml(-1) for isolate 389.93 and 7.6 x 10(7) conidia ml(-1) for isolate 392.93. The emergence of adult flies from pupae was reduced at high concentrations of conidia (3.0 x 10(8) and 1.0 x 10(8) conidia ml(-1)). The median lethal concentrations of the isolates against adults were 1.7 x 10(7) and 4.0 x 10(7) conidia ml(-1), respectively. Some of the fungal isolates examined may have potential as biological control agents of larvae of D. antiqua and related species.     

A Proposed Role for the Cuticular Fatty Amides of Liposcelis bostrychophila (Psocoptera: Liposcelidae) in Preventing Adhesion of Entomopathogenic Fungi with Dry-conidia

Maximum challenge exposure of Liposcelis bostrychophila to Beauveria bassiana, Paecilomyces fumosoroseus, Aspergillus parasiticus or Metarhizium anisopliae resulted in no more than 16% mortality. We investigated several of L. bostrychophila's cuticular lipids for possible contributions to its tolerance for entomopathogenic fungi. Saturated C14 and C16 fatty acids did not reduce the germination rates of B. bassiana or M. anisopliae conidia. Saturated C6 to C12 fatty acids that have not been identified in L. bostrychophila cuticular extracts significantly reduced germination, but the reduction was mitigated by the presence of stearamide. Cis-6-hexadecenal did not affect germination rates. Mycelial growth of either fungal species did not occur in the presence of caprylic acid, was reduced by the presence of lauric acid, and was not significantly affected by palmitic acid. Liposcelis bostrychophila is the only insect for which fatty acid amides have been identified as cuticular components. Stearamide, its major fatty amide, did not reduce germination of B. bassiana or M. anisopliae conidia or growth of their mycelia. Adhesion of conidia to stearamide preparations did not differ significantly from adhesion to the cuticle of L. bostrychophila. Pretreatment of a beetle known to be fungus-susceptible, larval Oryzaephilus surinamensis, with stearamide significantly decreased adhesion of B. bassiana or M. anisopliae conidia to their cuticles. This evidence indicates that cuticular fatty amides may contribute to L. bostrychophila's tolerance for entomopathogenic fungi by decreasing hydrophobicity and static charge, thereby reducing conidial adhesion.     

Exchange of Inoculum of Beauveria bassiana (Bals.) Vuill. (Hyphomycetes) Between Adult Flies of the Cabbage Maggot Delia radicum L. (Diptera: Anthomyiidae)

Adult cabbage maggots ( Delia radicum L.) were exposed to dry conidia of isolates of several hyphomycetous fungi by placing them in a centrifuge tube containing conidia, then releasing them into small screened plastic cages. Mortality was assessed after 48, 120 and 160 h. A Beauveria bassiana isolate (P89 from Musca domestica ) caused the highest mortality after 48 h, resulting in 100% mortality and 100% infection. Isolate L90 ( B. bassiana ) and one Metarhizium anisopliae isolate (ARSEF 2521) also caused fatal infection in more than 50% of the flies. To investigate exchange of inoculum, flies were placed in a small container with a dry powder formulation containing B. bassiana (Mycotrol ® ) on the bottom. The flies were removed to small screened cages containing untreated flies. This experiment confirmed the ability of flies to pass inoculum to other flies. In a similar experiment, one treated fly was placed in each cage with one untreated fly. When each fly died, one untreated fly was added to each cage after the dead fly was removed. This study showed that fly to fly transfer of fatal doses of inoculum was possible for a series of at least six flies. When female flies were exposed to the inoculum, then transferred to small cages containing males and an oviposition substrate, no eggs were laid. Further studies are being conducted to develop a system where flies attracted to a trap will be inoculated with the fungus and spread it to a field population.     

Fungal pathogens for arthropod pest control in orchard systems: mycoinsecticidal approach for pear psylla control

This paper reviews the research on entomopathogenic fungi in orchard systems and presents research on a mycoinsecticidal approach to an important pest of pear, the pear psylla. The review identifies the host-pathogen relationships that have been examined to date, the microbial formulation and application strategies that have been used, and the results that were obtained. The mycoinsecticides used in the pear psylla research were based on conidia of Beauveria bassiana (ARSEF #2860) and Paecilomyces fumosoroseus (ARSEF #2658). These were formulated into sprayable solutions containing water, 0.1% or 0.5% Ultrafine Sunspray oil (paraffinic oil) in water, or 0.1% acrylic polymer (Stressguard^TM) in water. Final spray solutions that contained 6 × 10⁶ conidiospores/ml were applied to psylla nymph infested trees at a rate of 5.39 × 10¹³ conidiospores/ha during the 1993--1995 seasons. In addition, two commercial formulations of B. bassiana, GHA from Mycotech and Naturalis L from Fermone Corp., were mixed in water at the same conidiospore application rates as the other fungal isolates. Single applications of the ARSEF fungal strain/formulation combinations produced psylla nymphal mortalities that ranged from 18.2--37.1%, but the results varied with formulation. Conidia formulated with acrylic polymers in water caused significantly higher mortalities several days earlier than either the water or water and oil combination in 1993. However, no significant differences among pathogen/formulation combinations occurred in 1994 or 1995. The performance of Naturalis L was comparable to the ARSEF fungal strain/formulation combinations with peak nymphal mortalities of 34.1%, while GHA produced a significantly lower peak mortality of only 10.8%. However, because of the low conidiospore concentrations in the Naturalis L formulation, final spray solutions contained nearly 25% of the oil-like carrier. Thus, psylla mortalities may not have been entirely attributed to mycosis. Based on the results from the ARSEF fungal formulations, a mycoinsecticidal approach to pear psylla management could be a useful component in an integrated pest management program for pear.     

Effects of nutrient medium composition and temperature on the germination of conidia and the entomopathogenic activity of the fungi

The effects of nutrient medium composition and temperature on the germination of conidia of the fungi Beauveria bassiana (strain AlG) and Metarhizium anisopliae (strain M-99) and their entomopathogenic activity have been studied. It was demonstrated that the presence of carbohydrates alone was sufficient for the spores of M. anisopliae M-99 to germinate, whereas the germination of B. bassiana AlG spores was inhibited by carbohydrates. Addition of KJ, ZnSO4, or KBr into the Czapek medium increased the entomopathogenic activity of B. bassiana. The optimum temperature for spore germination was 20-35 degrees C in both fungal species.