Effect of host plant on susceptibility of whitefly Bemisia tabaci (Homoptera: Aleyrodidae) to the entomopathogenic fungus Beauveria bassiana (Ascomycota: Hypocreales)

We determined host plant effect on susceptibility of whitefly Bemisia tabaci to the entomopathogenic fungus Beauveria bassiana under controlled conditions. Insects were reared on cucumber, eggplant, tomato or cabbage. Fungal suspensions of 1×10⁴, 10⁵, 10⁶, 10⁷ and 10⁸ conidia/mL were applied on second-instar nymphs. Nymphal survival significantly differed among different host plant species on which the nymphs were reared. Ten days after inoculation with 1×10⁸ conidia/mL, percent survival was 4.2±0.7, 9.6±0.4, 13.4±0.8, and 24.3±0.9% on cucumber, eggplant, tomato and cabbage, respectively. Average survival times of nymphs were also significantly influenced by host plant species. After inoculation with 1×10⁸ conidia/mL, survival times were 4.8±0.15, 6.0±0.11, 5.7±0.13, and 6.2±0.08 days for nymphs reared on cucumber, eggplant, tomato, and cabbage, respectively. Virulence also differed depending on host plant species; 10 days after inoculation, LC₅₀ values were 4.6×10⁴, 1.6×10⁵, 4.2×10⁵ and 2.1×10⁶ conidia/mL on cucumber, eggplant, tomato and cabbage, respectively. Nymphs on cucumber showed highest susceptibility.     

A tritrophic effect of host plant on susceptibility of western flower thrips to the entomopathogenic fungus Beauveria bassiana

Adult female western flower thrips (Frankliniella occidentalis) were exposed 12-24h to bean (Phaseolus vulgaris) and impatiens (Impatiens wallerana) leaf disks treated with Beauveria bassiana conidia and then transferred to clean bean or impatiens at various times post-treatment. Significantly greater levels of fungal infection were observed when thrips were treated on bean versus impatiens, but exposure to impatiens following treatment had no effect on fungal infection (percent mortality). This result, combined with observations of no inhibition of germination of conidia exposed to intact or macerated impatiens foliage, indicated that the negative effect of the impatiens host plant was not due to plant chemical compounds (antibiosis). Further observations revealed that insects acquired (picked-up) 75% more conidia from treated bean disks than from treated impatiens disks. This difference in dose acquisition was determined to account for the observed difference in percent mortality (15%) following treatment on the two host plants. Median lethal doses (LD(50)) of B. bassiana were not significantly different on the two host plants, but median lethal concentrations were nearly 7-fold greater on impatiens. This difference was explained by disproportionate rates of conidial acquisition at measured rates of conidial deposition (an inverse relationship was observed between application rate expressed as conidia/mm(2) and the number of conidia acquired). The mechanism underlying the differential rates of conidial acquisition from bean versus impatiens was not determined.     

The entomopathogen Beauveria bassiana has epiphytic and endophytic activity against the tomato leaf miner Tuta absoluta

The recent introduction and rapid spread of the tomato leaf miner Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) throughout Europe, Africa and the Middle East poses a severe threat to future cultivation of tomato and other Solanaceae. Among the best practicable means for effective and sustainable control of this invasive insect pest are entomopathogenic fungi, which can either prevent a further spread of this insect to new areas or keep population densities below an economic threshold level. Here, we report on the efficacy of a commercially available mycoinsecticide based on the entomopathogen Beauveria bassiana (Bals.) Vuill. (Ascomycota: Hypocreales) against all four larval stages of T. absoluta. In bioassays, high mortality rates and significantly reduced longevity of larvae were obvious when larvae had fed for a period of around 15 days on leaves with B. bassiana propagules present on the surface as an epiphyte with mortality values corrected for variance in control mortality of 90–100%. In addition, a second mode of action of B. bassiana against T. absoluta larvae was evident in bioassays in the form of an endophytic establishment of this fungus in treated tomato plants. Longevity of T. absoluta L4 larvae was significantly lower in individuals which had fed on surface‐sterilized tomato leaves obtained from plants treated 18 days before the bioassay with a B. bassiana suspension compared to larvae feeding on control plants treated with water. Corrected mortality reached values between 30% and 50% for all larval instars. Growth of tomato plants was not inhibited due to colonization by endophytic B. bassiana and a weak systemic translocation of fungal propagules in non‐treated leaves was evident in the assays. Accordingly, entomopathogenic fungi like B. bassiana express different modes of action again target insect pests, which is of particular relevance for the design of efficient management strategies for invasive pests like T. absoluta.     

Mitochondrial evolution in the entomopathogenic fungal genus Beauveria

Species in the fungal genus Beauveria are pathogens of invertebrates and have been commonly used as the active agent in biopesticides. After many decades with few species described, recent molecular approaches to classification have led to over 25 species now delimited. Little attention has been given to the mitochondrial genomes of Beauveria but better understanding may led to insights into the nature of species and evolution in this important genus. In this study, we sequenced the mitochondrial genomes of four new strains belonging to Beauveria bassiana, Beauveria caledonica and Beauveria malawiensis, and compared them to existing mitochondrial sequences of related fungi. The mitochondrial genomes of Beauveria ranged widely from 28,806 to 44,135 base pairs, with intron insertions accounting for most size variation and up to 39% (B. malawiensis) of the mitochondrial length due to introns in genes. Gene order of the common mitochondrial genes did not vary among the Beauveria sequences, but variation was observed in the number of transfer ribonucleic acid genes. Although phylogenetic analysis using whole mitochondrial genomes showed, unsurprisingly, that B. bassiana isolates were the most closely related to each other, mitochondrial codon usage suggested that some B. bassiana isolates were more similar to B. malawiensis and B. caledonica than the other B. bassiana isolates analyzed.     

Production,formulation and application of the entomopathogenic fungus Beauveria bassiana for insect control: current status

This review summarizes the progress and achievements made in the last decade in mass production formulation and application technology of the entomopathogenic fungus Beauveria bassiana. Reports published on relevant research from Belgium, Canada, China, Cuba, Czechoslovakia (former), France, Germany, Great Britain, Philippines, Poland, Switzerland, USA and USSR (former) regarding this topic have been covered. Much of the non‐English language literature, particularly that from Eastern European and Chinese sources, has not been translated and is inaccessible to most English or other western language readers. We have done this translation and through this review provide technological details about mass production of B. bassiana in China. Various aspects of B. bassiana growth, substrate use, production of mycelia, conidiospore and blastospores, process technologies associated with separation, drying and milling, formulation, storage and ‘shelf‐life’, and field efficacy are reviewed. Data are presented on: a modified diphasic production technology developed in China during the 1980s; comparisons between submerged fermentation, which usually produces blastospores, and those producing conidia; the use of mycelial preparations pelletized with alginate or gelatinized with cornstarch or cornstarch‐oil; and data on low or ultra‐low volume sprays of emulsifiable or oil conidial suspensions and dust formulations. B. bassiana has proved to be competitive with chemical insecticides for the annual protection of 0.8–1.3 million hectares against forest and farm insect pests in China. It is hoped that this review will help to bridge the language gap between eastern and western scientists in microbial control using B. bassiana.     

Host plant influences pathogenicity of Beauveria bassiana to Bemisia tabaci and its sporulation on cadavers

Laboratory bioassays were conducted to determine host plant effect on pathogenicity of the entomopathogenic fungus Beauveria bassiana (Balsamo) Vuill. (Ascomycota: Hypocreales) to the sweetpotato whitefly, Bemisia tabaci (Gennadius) (Homoptera: Aleyrodidae). Fourth instar B. tabaci reared on cucumber, tomato, melon, green pepper, potato, eggplant, marrow, cabbage, bean or cotton, were treated with 1 × 10⁷ conidia/ml B. bassiana EABb 93/14-Tp isolate. Mortality caused by B. bassiana significantly increased with time and it was significantly affected by the host plant on which the nymphs were reared. Mean mortality of nymphs 8 days after inoculation ranged between 52.3±7.3 for nymphs reared on cotton and 91.8±5.8 for nymphs reared on cucumber. Average survival times of nymphs treated with the fungal suspensions were also significantly influenced by the host plant, with a mean of 4.7±0.1 days for nymphs reared on cucumber, 6.6±0.2 days for cotton and 6.9±0.1 days for green pepper. The production of newly formed conidia was also affected by host plant and varied from 111000±8600 conidia/cadaver for nymphs reared on cotton to 597000±28000 conidia/cadaver for those reared on melon.     

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.     

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.     

A study of host specificity in the entomopathogenic fungus Beauveria bassiana (Hypocreales,Clavicipitaceae)

Beauveria bassiana (Balsamo – Crivelli) Vuillemin based mycoinsecticides are used against agricultural, veterinary and medical insect pests. The fungus has a very diverse and extensive host range. Variation in virulence among isolates of B. bassiana to different insect species has been abundantly documented. Given the effect of multiple factors on virulence, it is not certain whether the observed difference in virulence can be labelled as host specificity. Environmental conditions and susceptibility of the insect population are two main factors that affect successful fungal infection. Keeping the environmental factors constant, if virulence of an isolate to different insect species and different populations within an insect species is compared, the scale of difference between the two responses can be estimated. If differences in virulence of an isolate to different insect species are greater than the difference in virulence to different insect populations within an insect species, then, the isolate can be considered as exhibiting specific preference to those insect species towards which it exhibits high virulence. To examine this feature, a worldwide sample of B. bassiana was bioassayed on nine insect species and two different populations within two insect species. Laboratory bioassays were done on: Bombyx mori (Lepidoptera), Spodoptera litura (Lepidoptera), Chilo partellus (Lepidoptera), Helicoverpa armigera (Lepidoptera), Epilachna vigintioctopunctata (Coleoptera), Mylabris pustulata (Coleoptera), Aphis craccivora (Homoptera), Maconellicoccus hirsutus (Hemiptera) and Oecophylla smaragdina (Hymenoptera). The range of variation in virulence of a B. bassiana isolate to different insect species was not more than that observed with different populations within a single insect species. B. bassiana is thus a generalist with no strict host preference. B. bassiana based biopesticide can be used as a broad spectrum insecticide against a myriad of insect pests.     

Infection sites of the entomopathogenic fungus Beauveria bassiana in the larvae of the mosquito Aedes aegypti

A series of experiments were conducted to determine the infection sites of the entomopathogenic fungus Beauveria bassiana after ingestion by the larvae of Aedes aegypti. The timing of the host death in relation to larval molting, the principle sites of fungal infection and development in host tissues were studied. Fungal conidiospores (CS) and blastospores (BS) were used separately for treatment of mosquito larvae. Although in most instances CS germinated and developed within the host, in others there was a premature abortion of the fungal development cycle. On the other hand, BS ingested by the larvae showed differences in the fungal development stages in the larval tissues. While the two primary infection sites were the head and the anal region, the most preferred site for fungal development was the larval gut. No more than two cycles of fungal development can occur in the host. Although both CS and BS are effective as larvicides, BS is far more pathogenic.

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Résumé Une série d'expériences a été menée afin de déterminer les emplacements d'infection du fongus entomopathogénique Beauveria bassiana (souche GK 2016) lequel avait été ingesté des larves d'Aedes aegypti. On a étudié le moment de la mort des hôtes en relation des mues des larves, les emplacements principaux où se conduit l'infection fongale et le développement du fongus dans des tissus divers d'hôte. On a utilisé les conidiospores (CS) et les blastospores (BS) séparément pour traitement des larves des moustiques. Bien que dans la plupart des cas CS ait germiné et se soit développé chez l'hôte, en d'autres cas, CS a germiné mais n'avait pas produit du BS évidemment grâce à l'avortement prématuré du cycle de développement des fongus chez l'hôte. Le BS qui avait été ingesté dans les larves présentait des stages différents de développement du fongus dans les tissus des larves. Quoique les deux emplacements placements principaux étaient la tête et la région anale, l'emplacement préféré pour le développement du fongus était l'intestin des larves. Nous montrons qu'il n'y a plus de deux cycles de développement du fongus chez l'hôte. Bien que CS et BS soient efficaces comme larvicides, BS est de loin plus pathogène.

     

Bioassay method for assessing the virulence of Beauveria bassiana against tarnished plant bug, Lygus lineolaris (Hem., Miridae)

A standard bioassay method for assessing the pathogenicity of Beauveria bassiana (Balsamo) Vuillemin (GHA strain) against second instar tarnished plant bug, Lygus lineolaris (Palisot de Beauvois) (Hem., Miridae) was developed. Several types of inoculation methods, assay containers and incubation times were tested. Our goal was to minimize control mortality and maximize treatment mortality. Five inoculation methods (immersing broccoli florets or bean pods, spraying broccoli florets or bean pods, and immersing insects) and four types of plastic containers (114‐, 171‐, 228‐ and 455‐ml) were tested. Immersing insects directly in a fungal suspension was the most effective inoculation method, which resulted in a treatment mortality of 70–81.3% at a concentration of 1 × 10⁷ conidia/ml. The 114‐ml plastic container was the most suitable assay container when 10 tarnished plant bug nymphs were treated together, resulting in a control mortality of only 6% 12 days after treatment. Within the first 6 days after treatment, 71.1% of the insects were killed, compared with a total mortality of 81.3% after 12 days. Nymphs infected with the test fungus changed colour from green to black. Mycelial outgrowth and sporulation on the cadavers demonstrated that most nymphs died of fungal infection. A total of 61.1 and 80.5% of the cadavers showed signs of mycelial outgrowth 9 days after death among those that were surface sterilized and those that were not, respectively.     

Virulence of Metarhizium anisopliae and Beauveria bassiana isolates and the effects of fungal infection on the reproduction potential of Rhiphicephalus microplus engorged females

The aim of the study was to assess the virulence of five Metarhizium anisopliae (Ma) and three of Beauveria bassiana (Bb) isolates, and the effect of the fungal infection to the reproduction of engorged females from two colonies of Rhiphicephalus microplus; one colony was collected from naturally infested cattle (Native) and the other one from a laboratory colony (Media Joya). Virulence was evaluated using the immersion technique at a concentration of 1?×?10⁸ conidia/ml; control groups received a water suspension with Tween 80 (0.1%). The Reproductive Efficiency Index ‘REI’ (eggs laid/engorged female weight) and the Reproductive Aptitude Index ‘RAI’ (eggs hatched as larvae/engorged female weight) were calculated for both groups. This experiment shows that two entomopathogenic fungal isolates, Bb115 and Ma136, caused high mortality from 5 days post-treatment (PT), reaching mortality rates of 99–100% at 15 days PT in both R. microplus colonies. The Bb115 isolate caused 98 and 79% reduction in egg oviposition in the field and laboratory colonies, respectively, while the reduction in egg hatchability was 98 and 89% in the field and laboratories colonies, respectively. In the case of Ma136, the egg oviposition was reduced in 73% in the field colony and 64% in laboratory colony, while in the field and laboratory colonies, with a reduction in egg hatchability of 73% and 86%, respectively. These results indicate the potential of Bb115 and Ma136 isolates as possible biological control agents of R. microplus.     

Introduction of Beauveria bassiana as a biological control agent for Tribolium castaneum in Kerman province

Barley, Hordeum vulgare, one of the important crops in the word, is used in malting, feed and food industries. The red flour beetle, Tribolium castaneum, was found wherever grains or other dried foods are stored. Disinfestations of barley using chemical methods to kill insects, in this research, for the first time we isolated the pathogenic KB512 of entomopathogenic fungi Beauveria bassiana from soil and insects, which produced aerial and submerged conidia and blastospores in laboratory conditions. We investigated the best conditions for the production and utilisation of spore suspension to spray the larvae of T. castaneum, which is one of the important pests in Kerman province (Iran). One hundred and eighty isolates that naturally infected by T. castaneum were reared during spring and summer seasons 2010–2011. The pathogenicity test was carried out with direct spray. To bioassay the isolates, three concentrations of the spore suspension were prepared as follows: 1?×?10⁶ and 1?×?10⁸ conidia/ml. The pests were sprayed by aerial conidial suspension, which was prepared by 0.01% Tween 80 in distilled water, and the controls were sprayed by 0.01% Tween 80 in distilled water. After spraying the pests, the plates were incubated at 25?±?1?°C and 80% of relative humidity. Then, the treated pests were monitored every day for the fungal growth and mortality.     

Side effects of the entomopathogenic fungus Beauveria bassiana on the predator Coccinella undecimpunctata

The effect on predators of the biopesticide based on Beauveria bassiana spores was studied. A high concentration of the pathogen showed adverse effects on the predator (Coccinella undecimpunctata) and its biological aspects: 2, 4 and 8 g/L eliminated egg deposition in treated females. Spores at 4 g/L affected significantly the longevity of adults, duration of larvae and pupal period.     

桃蚜脱皮对球孢白僵菌毒力的影响

室内测定了球孢白僵菌Beauveria bassiana BBSG8702菌株对桃蚜Myzus persicae 若蚜的毒力,并分析了若蚜脱皮与白僵菌有效侵染之间的关系。在21℃、1×10⁶/mL孢子浓度下, 1～4龄若蚜感菌后的累积死亡率分别为10.1%、2.1%、3.1%和40.2%,明显低于同样条件下成蚜的感菌死亡率(98.4%)。在若蚜各龄感菌死亡的个体中,1～4龄中分别有8.1%、50.0%、44.4%和98.0%的若蚜在死亡前发育到成蚜,且都能产下正常发育的后代。若蚜的感菌死亡率与接菌后到第一次脱皮的时间密切相关,脱皮早则感菌死亡率低,反之亦然。但试验中也发现有部分若蚜特别是低龄若蚜感菌后未完成第一次脱皮便死亡。观察了桃蚜在1、4龄早期感染球孢白僵菌后的发育、存活和生殖情况,结果表明：1、4龄早期若蚜接菌后第一次脱皮的时间早于未接菌若蚜,但提前幅度少于5%,在羽化为成蚜之前被致死的概率分别只有4.1%和0,在羽化为成蚜后8天内的生殖率与未接菌蚜虫的无明显差异。这些结果表明,若蚜的脱皮,尤其当蚜虫在低龄若蚜时受感染后的多次脱皮,可有效地摆脱球孢白僵菌分生孢子的侵染,降低该菌的毒力。     

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.     

Host plant effects on activity of the mitosporic fungi Beauveria bassiana and Paecilomyces fumosoroseus against two populations of Bemisia whiteflies (Homoptera: Aleyrodidae)

Laboratory bioassays were conducted to determine the effect of host plant on mycosis in two geographically distinct populations of early 2nd-instar nymphs of Bemisia argentifolii Bellows & Perring from the entomopathogenic fungi Beauveria bassiana (Balsamo) Vuillemin and Paecilomyces fumosoroseus (Wize) Brown & Smith. Mycosis in B. argentifolii nymphs varied according to the host plant on which the nymphs were reared but not according to the population. Both populations of whiteflies reared on cotton were consistently significantly less susceptible to infection by either fungus than when reared on melon. We hypothesized that the cotton plant produced a fungal inhibitor that may confer protection on whiteflies feeding (and possibly sequestering) upon it. Germination of conidia of both fungi was strongly inhibited (below 12% germination) on the cuticle of nymphs reared on cotton but was over 95% on the cuticle of nymphs reared on melon. We further hypothesized that the terpenoid gossypol, produced by many cultivars of cotton, might have been involved in antibiosis. Gossypol mixed with Noble agar at five concentrations was tested for its effects on germination of conidia of both fungi. P. fumosoroseus was highly tolerant of gossypol, even at the relatively high concentration of 1000 ppm, while B. bassiana tolerated gossypol at concentrations up to 500 ppm and strong inhibition only occurred in presence of gossypol at 1000 ppm. Our in vivo findings on cotton and on the insect's cuticle pointed at a potential host plant-mediated antibiosis. The in vitro tolerance of P. fumosoroseus and partial tolerance of B. bassiana to gossypol disagreed with our in vivo data. Gossypol concentrations higher than 1000 ppm might have increased the sensitivity of the fungi in our in vitro tests. Sequestered gossypol (and/or other cotton plant allelochemicals) by B. argentifolii nymphs would explain, at least partially, the insect's defense against the pathogens.This revised version was published online in October 2005 with corrections to the Cover Date.     

Susceptibility of the cattle tick Boophilus microplus (Acari: Ixodidae) to isolates of the fungus Beauveria bassiana

The susceptibility of the tick Boophilus microplus to Beauveria bassiana was evaluated by inoculating eggs, larvae and engorged females of the tick with five fungal isolates at concentrations of 10⁶, 10⁷ and 10⁸ conidia/ml. Tick eggs (0.25 g) were immersed in 1 ml of a suspension of the different conidial concentrations for 1 min. Similar exposure was performed by immersion of 2000 larvae and homogeneous groups of nine engorged females in 2 and 20 ml of conidial suspension, respectively. Treated eggs, larvae and adults were placed in an incubator at 27 ± 1 °C and relative humidity above 80% for evaluation of the fungal action. All fungal isolates applied at all conidial concentrations reduced the hatching rate of larvae from treated eggs by 1.36–65.58% and increased the mortality rate of inoculated larvae by 0.8–70.49%. In the bioassay with engorged females, oviposition period was reduced by 9.69–47.80%, egg mass weight by 4.71–53.87%, estimated reproduction by 8.3–60.62%, egg production index by 5.03–54.20%, percent larval hatching by 0.27–13.96%, and the mortality rate of treated females was increased by 96.60–100%. The reduction of the estimated reproduction obtained for the treated groups ranged from 8.37 to 64.52%. The sporulation of the pathogen on dead females ranged from 3.70 to 88.88% depending on the isolate and concentration used. Isolates AM 09, CB 7 and JAB 07 were the most effective and effectiveness increased with increasing concentrations of conidia in the suspensions.     

Variability in virulence of Beauveria spp. soil isolates against Ostrinia nubilalis

European corn borer (Ostrinia nubilalis) is an important maize pest which is treated mainly by synthetic pesticides with many negative effects for ecosystem and human health. Soil borne entomopathogenic fungi of species belonging to Beauveria genus may provide an alternative strategy for biological control of this pest. In this article, we report results of virulence testing of 46 soil isolates of Beauveria spp. against O. nubilalis in relation to isolates origin and haplotype. All strains were collected from soil using Galleria mellonella bait method. Conidia suspension with concentration 10⁷ conidia in ml was used for virulence test against 4th instar larvae of O. nubilalis at temperature 25°C. After 14 days, mortality of larvae was in the range 34%–96%. Median lethal time LT50 was estimated to 5.5–21.3 days. Mortality was not in relation to habitat or any other environmental parameter of sites where isolates came from. Differences among species were insignificant. Isolates were divided into 8 genetic lineages and 14 haplotypes using sequencing of ITS and Bloc nuclear regions. None of the lineages showed higher mortality than others. Despite more or less virulent isolates being found in each lineage, the three most virulent isolates belonged to the same lineage Beauveria bassiana A3. The four most virulent isolates were compared to commercial isolate GHA to assess medium lethal concentration. LC50 were estimated in range 7.5 × 10⁴ to 9.5 × 10⁵. Three of the four isolates showed equal or greater efficiency than strain GHA.     

Susceptibility of apple clearwing moth larvae,Synanthedon myopaeformis (Lepidoptera: Sesiidae) to Beauveria bassiana and Metarhizium brunneum

Apple clearwing moth larvae, Synanthedon myopaeformis (Lepidoptera: Sesiidae) were found to be susceptible to infection by two entomopathogenic fungi: an indigenous fungus isolated from S. myopaeformis cadavers and identified as Metarhizium brunneum (Petch); and Beauveria bassiana isolate GHA. In laboratory bioassays, larvae exhibited dose related mortality after exposure to both the M. brunneum and Beauveria bassiana with 7 day LC₅₀'s of 2.9×10⁵ and 3.4×10⁵ spores/mL, respectively. Larval mortalities caused by the two isolates at 1×10⁶ spores/mL were not significantly different and 73% of the M. brunneum-treated, and 76% of the B. bassiana-treated larvae were dead 7 days post treatment, with LT₅₀'s of 5.5 and 5.1 days, respectively.