The Susceptibility of Boophilus annulatus (Ixodidae) Ticks to Entomopathogenic Fungi

The pathogenicity of five species of entomopathogenic fungi (Deuteromycetes, species: Beauveria bassiana, Metarhizium anisopliae, Metarhizium flavoviride, Paecilomyces fumosoroseus and Verticillium lecanii ) to the various developmental stages of Boophilus annulatus ticks was compared under laboratory conditions. M. anisopliae and B. bassiana strains were most virulent to engorged females and caused 85-100% mortality within 7-10 days post-inoculation (PI). The highest mortality of engorged females caused by other fungi reached only 25-60%. All tested fungi prevented or reduced the egg laying capability of the ticks several days before their death. Females surviving after treatment with the most virulent M. anisopliae strain (Ma-7) reached only 7-8% of their egg laying capacity as compared with the control. Other fungi caused a reduction of the weight of laid eggs by 35.4-80.8% as compared with untreated females. Only M. anisopliae and B. bassiana strains caused 70-98% mortality of the treated eggs. Unfed larvae of Boophilus annulatus were sensitive to M. anisopliae and M. flavoviride strains. The Ma-7 strain was most virulent to unfed larvae, with a mortality rate of 80.4% at a concentration of 1 ×107 spores ml -1 and 100% mortality at a concentration of 1 ×108 spores ml -1 .     

Infection of the Coffee Berry Borer Hypothenemus hampei (Coleoptera: Scolytidae) by Brazilian Isolates of the Entomopathogenic Fungi Beauveria bassiana and Metarhizium anisopliae (Deuteromycotina: Hyphomycetes)

The virulence of four fungal isolates (three Beauveria bassiana and one Metarhizium anisopliae ) against adult female coffee berry borers (CBB) was investigated. The most virulent isolate from initial bioassays, B. bassiana LPP1, with a LT 50 of 3.4 days, was further investigated by application to berries prior to infestation and to berries already infested with CBB. At the highest concentration applied to berries (1 ×10 7 conidia mL -1 ), CBB mortality was 83% (berries inoculated prior to infestation) and 62% (berries inoculated after infestation).     

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.     

Pathogenicity of entomopathogenic fungi to different developmental stages of Rhipicephalus sanguineus (Acari: Ixodidae).

The pathogenicity of 4 species of entomopathogenic fungi (Hyphomycetes species: Beauveria bassiana, Metarhizium anisopliae, Metarhizium flavoviride, and Paecilomyces fumosoroseus) to various developmental stages of Rhipicephalus sanguineus (Acari: Ixodidae) ticks was compared under laboratory conditions. The most virulent isolate, M. anisopliae-108, caused 92-96% mortality to unfed larvae and nymphs on day 7 postinfection (PI) and 100% mortality to unfed adults and engorged females on day 21 PI. The pathogenicity of M. anisopliae-108 to engorged larvae and nymphs was lower--82.6 and 60%, respectively. All tested B. bassiana, M. flavoviride, and P. fumosoroseus isolates were significantly less virulent (P < 0.05) or avirulent toward most life stages of R. sanguineus. The M. anisopliae and M. flavoviride isolates also prevented or reduced the ability of the ticks to lay eggs several days before their deaths. Female ticks infected by the fungi achieved only 11.3-60.8% of their egg-laying capacity compared with the controls.     

Beauveria bassiana yeast phase on agar medium and its pathogenicity against Diatraea saccharalis (Lepidoptera: Crambidae) and Tetranychus urticae (Acari: Tetranychidae)

Beauveria bassiana colonizes insect hosts initially through a yeast phase, which is common in some artificial liquid cultures, but not reported on artificial solid media. We describe a yeast-like phase for B. bassiana isolate 447 (ATCC 20872) on MacConkey agar and its virulence toward Diatraea saccharalis and Tetranychus urticae. The yeast-like cells of B. bassiana developed by budding from germinating conidia after 24-h incubation. Cells were typically 5-10 microm and fungal colonies were initially circular and mucoid, but later were covered with mycelia and conidia. Ability to produce yeast-like cells on MacConkey medium was relatively common among different B. bassiana isolates, but growth rate and timing of yeast-like cell production also varied. Metarhizium anisopliae and Paecilomyces spp. isolates did not grow as yeast-like cells on MacConkey medium. Yeast-like cells of B. bassiana 447 were more virulent against D. saccharalis than conidia when 10(7)cells/ml were used. At 10(8)cells/ml, the estimated mean survival time was 5.4 days for the yeast suspension and 7.7 days for the conidial suspension, perhaps due to faster germination. The LC(50) was also lower for yeast than conidial suspensions. Yeast-like cells and conidia had similar virulence against T. urticae; the average mortalities with yeast-like cells and conidia were, respectively, 42.8 and 45.0%, with 10(7)cells/ml, and 77.8 and 74.4%, with 10(8)cells/ml. The estimated mean survival times were 3.6 and 3.9 for yeast and conidial suspensions, respectively. The bioassay results demonstrate the yeast-like structures produced on MacConkey agar are effective as inoculum for B. bassiana applications against arthropod pests, and possibly superior to conidia against some species. Obtaining well-defined yeast phase cultures of entomopathogenic hyphomycetes may be an important step in studies of the biology and nutrition, pathogenesis, and the genetic manipulation of these fungi.     

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.     

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.     

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.     

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.     

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.     

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.     

球孢白僵菌和金龟子绿僵菌不同菌株对黑足角胸叶甲成虫的致病力评价

本研究在测定不同球孢白僵菌Beauveria bassiana和金龟子绿僵菌Metarhizium anisopliae菌株的生长速率与产孢量的基础上, 采用孢悬液浸渍法进行了对油茶新害虫--黑足角胸叶甲Basilepta melanopus成虫的生物测定, 旨在筛选出感染该成虫的高致病力菌株, 为防治该虫提供新的生物资源。结果表明： 不同菌株生长速率和产孢量间存在显著差异, MaYTTR-04, BbFZ-17, MaZPTR-01和BbTK-01生长速率和产孢量均显著高于其他菌株。接种后, 叶甲成虫累积死亡率随时间的增加而逐渐增高, 接种白僵菌7 d后, 成虫校正死亡率全部达到100%; 接种MaZPTR-01和MaYTTR-04两个绿僵菌菌株14 d后, 成虫死亡率分别为80.3%和78.8%。而且接种白僵菌后, 叶甲成虫的僵虫率显著较绿僵菌高, 尤其以BbTK-01和BbFZ-17两个菌株较好, 分别达到85.7%和75.8%。BbXJ-01, BbFZ-17和BbTK-01 3个白僵菌菌株的LT₅₀最小, 分别为3.0, 3.3和3.4 d; MaYTTR-04和MaZPTR-01两个绿僵菌的LT₅₀分别为6.0和6.2 d。结果说明, 白僵菌对叶甲成虫的致病力较强, 尤其是BbTK-01和BbFZ-17两个菌株, 不仅致死率高, 且致死速度快, 僵虫率高, 同时这2个菌株生长速度快、 产孢量大, 具有优良的生产特性, 在黑足角胸叶甲的生物防治中将有重要的应用价值。     

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.     

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.     

Entomopathogenic Fungi Associated with Natural Populations of the Moroccan Locust Dociostaurus maroccanus (Thunberg) (Orthoptera: Gomphocerinae) and Other Acridoidea in Spain

The entomopathogenic fungi Beauveria bassiana Vuill . and Metarhizium anisopliae (Metschnikoff) have been found in natural populations of the Moroccan locust Dociostaurus maroccanus (Thunberg) and other species of acridoids that cohabit the same locust breeding areas in southern Spain . Infection levels of B. bassiana on insects collected in the field and maintained under laboratory conditions were relatively high (1 . 6 - 20 . 5%) . The prevalence of the disease extended from spring to summer in the three consecutive years monitored . A local isolate of this fungus demonstrated high virulence (LD = 440 conidia / insect) against the 50 locust D. maroccanus in the laboratory bioassay . The relatively wide host range of B. bassiana and its adaptation to the dry and hot conditions dominating the locust breeding area suggest that this isolate could be considered in the development of a biological control programme against D. maroccanus.     

Food consumption by Chilo partellus (Lepidoptera: Pyralidae) larvae infected with Beauveria bassiana and Metarhizium anisopliae and effects of feeding natural versus artificial diets on mortality and mycosis

Second and third instar Chilo partellus larvae were infected with Beauveria bassiana and Metarhizium anisopliae (both at 1x10(8)conidia/ml) and daily consumption of maize leaves was measured. Infection by the fungi was associated with reduced mean daily food consumption. Reduction in food consumption became evident 3-4 days after treatment with the fungi for second instar larvae and 4-5 days for third instar larvae. Four conidial concentrations, 1x10(5), 1x10(6), 1x10(7), and 1x10(8)conidia/ml, were tested against second instar larvae. Food consumption dropped by 70-85% when the second instar larvae were treated with the fungi at 1x10(8)conidia/ml. Reduction in food consumption by C. partellus larvae infected with B. bassiana and M. anisopliae may offset the slow speed of kill of the fungi. The effect of artificial versus natural diets on mortality and mycoses of second instar larvae treated with the fungi at 1x10(8)conidia/ml was determined. Larvae provided with artificial diet suffered little mortality and mycoses than larvae provided with maize leaves. The LT(50) was longer for larvae provided with artificial diet.     

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.     

黄绿绿僵菌Mf82菌株对不同虫态褐飞虱的毒力

对水稻重要害虫褐飞虱Nilaparvata lugens目前市场上尚无一种理想的微生物杀虫剂。昆虫病原真菌具有从体壁侵入的能力因而对刺吸性害虫的防治具有优势。为此, 本研究选用不同原寄主和来源地的3种昆虫病原真菌（金龟子绿僵菌Metarhizium anisopliae、 黄绿绿僵菌Metarhizium flavoviride和球孢白僵菌Beauveria bassiana）的12个不同菌株, 以1 100孢子/mm²孢子悬浮液进行室内毒力测定。结果表明： 在参试的不同菌种12个菌株中, 黄绿绿僵菌Mf82菌株对褐飞虱成虫致病力最高, 10 d累计校正死亡率为83.5%, 致死中时（LT₅₀）为4.6 d。其不同浓度孢子液对褐飞虱3个发育阶段有不同程度的致病力, 毒力大小顺序为成虫>高龄若虫>低龄若虫。黄绿绿僵菌孢子液对各处理稻株褐飞虱产卵痕部位、 卵粒均有侵染作用, 10 d侵染率分别为66.7%和51.2%, 卵龄越低, 侵染效果越好, 卵龄为0.5 d时侵染率最高。本研究表明黄绿绿僵菌Mf82菌株对褐飞虱成虫、 若虫和卵均有较强的致病性, 是一株极具应用潜力的生防真菌。     

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.     

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).