Effects of virulence,sporulation, and temperature on Metarhizium anisopliae and Beauveria bassiana laboratory transmission in Coptotermes formosanus

Sporulation characteristics and virulence of Metarhizium anisopliae and Beauveria bassiana were examined in relation to laboratory transmission in Coptotermes formosanus. Fungal isolates significantly affected disease prevalence in termite populations. Sporulation of M. anisopliae played a more important role than virulence in producing epizootics within small groups of termites, but this was not the case for B. bassiana. Isolates characterized by quick sporulation (day 2 after death) did not exhibit better transmission in termites than those with high total sporulation (day 11 after death) in either fungal species. An isolate of M. anisopliae ranking highly in all three categories (virulence, quick sporulation, and total sporulation) produced better epizootics than an isolate that was inferior in all three characteristics. High temperatures (35 degrees C) significantly reduced fungal germination rates, leading to significant reduction of epizootics. M. anisopliae was better than B. bassiana in producing epizootics at 27 degrees C. Thus, fungal characteristics other than virulence should be considered for the seasonal colonization approach to termite microbial control.     

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.     

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.     

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.     

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).     

Defense mechanism of the termite, Coptotermes formosanus Shiraki, to entomopathogenic fungi

Termites, Coptotermes formosanus Shiraki, reared individually, were highly susceptible to entomopathogenic fungi, Paecilomyces fumosoroseus and Beauveria brongniartii and Metarhizium anisopliae, while termites reared in groups were highly resistant. Quantitative assays with an epifluoresent microscope revealed a significant difference in the number of conidia attachments among three entomopathogenic fungi. The conidia of B. brongniartii and P. fumosoroseus bound to termite cuticles more effectively than M. anisopliae conidia. Our results also suggested that self-grooming behavior is less effective, but mutual grooming is very effective in the removal of conidia from cuticles of their nestmates. Statistical analysis of removal rates indicated that conidia of P. fumosoroseus and B. brongniartii were removed more rapidly than M. anisopliae conidia from termite cuticles.     

Diversity of entomopathogenic fungi near leaf-cutting ant nests in a neotropical forest, with particular reference to Metarhizium anisopliae var. anisopliae

We investigated the prevalence of entomopathogenic fungi associated with leaf-cutting ant colonies in a small area of tropical forest in Panama. There was a high abundance of Metarhizium anisopliae var. anisopliae near the colonies. Beauveria bassiana was also detected in the soil, Aspergillus flavus in dump material, and six Camponotus atriceps ants were found infected with Cordyceps sp. Based on a partial sequence of the IGS region, almost all of the M. anisopliae var. anisopliae isolates fell within one of the three main clades of M. anisopliae var. anisopliae, but with there still being considerable diversity within this clade. The vast majority of leaf-cutting ants collected were not infected by any entomopathogenic fungi. While leaf-cutting ants at this site must, therefore, regularly come into contact with a diversity of entomopathogenic fungi, they do not appear to be normally infected by them.     

Comparative analysis of the production of insecticidal and melanizing macromolecules by strains of Beauveria spp.: in vivo studies

Eleven strains of Beauveria bassiana, and a further five species of Beauveria sp., were tested by injection of 8x10(2) conidia into the haemocoel of the larvae of the lepidopteran Galleria mellonella with the aim of analysing their toxin producing activity in vivo. Although the virulent strains killed 100% of the insects at slightly different rates (4-6 days) there were significant differences in the pattern and intensity of host melanization caused by isolates. The majority of the isolates of Beauveria spp. induced a fast and intense melanization of the cuticle of the integument and of tracheal wall, which followed one of three patterns. Another small group of two B. bassiana strains, isolated from Ostrinia nubilalis, induced very weak or no melanization. Strains 618 and 101 of B. bassiana, were selected as models of "melanizing" and "non-melanizing" strains, respectively. Ultrastructural alterations of cells of hypodermal and tracheal epithelium and of haemocytes, assumed to be at least partially caused by fungal toxins, were revealed in larvae infected by both isolates. However, their effects on the fine structure of the hypodermis were different. Injection of sera obtained from haemolymph of insects infected with B. bassiana 618 showed that they have insecticidal, melanizing, and cytotoxic effects similar to those occurring during mycosis. Chromatographic studies and bioassays with fractions prepared from crude serum have allowed a partial identification of the toxic molecules secreted by the fungus in vivo. They are proteinaceous, as shown by protease treatments, thermolabile, negatively charged, and not glycosylated with alpha-d-mannose or alpha-d-glucose. If strain B. bassiana 618 produces melanizing macromolecules which are vivotoxins secreted during the mycosis, the mode of action of isolate 101 is different. Its capacity to kill the host depends on active mycelial development, and on the production of low molecular weight toxins.     

Synergistic effect of entomogenous fungi on some insecticides against Bihar hairy caterpillar Spilarctia obliqua (Lepidoptera: Arctiidae)

A number of fungal parasites infect a wide range of insects and cause epizootics from time to time. Beauveria bassiana (Balsamo) Vuillemin and Metarhizium anisopliae (Metschnikoff) Sorokin are two of the major disease-causing fungi in insects. Investigations were carried out to study the effect of these fungi on the toxicity of endosulfan, imidacloprid, lufenuron, diflubenzuron, dimethoate and oxydemeton methyl against 10-11 days old larvae of Spilarctia obliqua (Walker). For some products the combination treatments showed higher dose mortality response than the sole treatment of fungal conidia or the insecticide. The combination of insecticides with B. bassiana showed 1.26-35.8 fold increase in toxicity of insecticides over sole treatment, while the increase was 1.05-72.0 fold in case of M. anisopliae. Imidacloprid 17.8 SL and oxydemeton methyl 25EC may be used in combination with these fungi for management of S. obliqua.     

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.     

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.     

Laboratory evaluation of entomopathogenic fungi Beauveria bassiana and Metarhizium anisopliae against puparia and adults of Ceratitis capitata (Diptera: Tephritidae)

Laboratory experiments were done to measure the pathogenicity of 10 autochthonous isolates of Beauveria bassiana (Balsamo) Vuill. and of five Metarhizium anisopliae (Metsch.) Sorok. toward puparia and adults of the Mediterranean fruit fly, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae). Although all isolates applied via inoculation of the fungal suspensions on the ventral surface of the abdomen were pathogenic to adults, with mortality rates ranging from 30 to 100% and average survival times (ASTs) from 6.5 to 8.6 d, when C. capitata puparia were immersed in the conidial suspensions, only B. bassiana Bb-1333 and EABb 01/103-Su and M. anisopliae EAMa 01/58-Su isolates caused >50% mortality of puparia. In a second series of bioassays conducted on five selected isolates, adults were sprayed with four 10-fold concentrations ranging from 1.0 x 10(5) to 1.0 x 10(8) colony-forming units (cfu)/ml. The median lethal concentrations (LC50) of the four most virulent isolates ranged from 4.9 x 10(5) to 2.0 x 10(6) cfu/ml with estimated time to kill 50% of the insects ranging from 4.6 to 5.3 d. The effect of a sublethal dose (ca. LD50) of either B. bassiana EABb 01/103-Su or M. anisopliae EAMa 01/58-Su isolate was studied by reciprocal crossing. Treatment with B. bassiana reduced fecundity and fertility at 6, 8, and 10 d after treatment, with fecundity and fertility reductions ranging from 20.0 to 71.2% and from 33.6 to 60.0%, respectively. These reductions occurred in pairing combinations of treated females with either treated or nontreated males. M. anisopliae was more effective in reducing fecundity and fertility at 6 d after treatment, with the reduction varying from 58.4 to 72.1% and from 28.6 to 45.9%, respectively. In addition, the first oviposition was significantly delayed for 1 d in females treated by either fungal species. The above-mentioned five selected isolates were assayed against C. capitata puparia treated as late third instars in sterilized soil at 25'C under three moisture conditions (-0.1, -0.01, and -0.0055 MPa). At -0.01 MPa, all isolates were low pathogenic to C. capitata puparia, whereas significant differences in the puparia mortality occurred between isolates at -0.1 and -0.0055 MPa. The highest pupal mortalities ranged from 52.5 to 70.0%, as a function of soil moisture and were caused by EAMa 01/58-Su and Bb-1333 isolates.     

Virulence, horizontal transmission, and sublethal reproductive effects of Metarhizium anisopliae (Anamorphic fungi) on the German cockroach (Blattodea: Blattellidae)

Virulence of Metarhizium anisopliae (Metschnikoff) Sorokin strain EAMa 01/121-Su against the German Cockroach, Blatella germanica (L.), was determined using four concentrations ranging from 4.2 x 10(6) to 4.2 x 10(9) spores per milliliter. The LD50 value was 1.4 x 10(7) spores per milliliter (56,000 spores per cockroach) and LT50 values were 14.8 days and 5.3 days for 4.2 x 10(8) and 4.2 x 10(9) spores per milliliter, respectively. An experiment was conducted to evaluate whether a fungal transmission could exist among infected and healthy cockroaches. Percentage mortality at a ratio of 1:10 of infected to unexposed cockroaches was 87.5% and LT50 was 12.2 days, which indicated the potential of this strain to be horizontally transmitted and to rapidly spread the infection in the insect population. The effect of a sublethal dose (ca. LD60) of M. anisopliae EAMa 01/121-Su strain, applied topically on German cockroaches, was studied by reciprocal crossing. Othecal production, oothecal hatchability, and nymphal production declined upon exposure to M. anisopliae EAMa 01/121-Su strain. The mean number of oothecae laid by female was progressively and significantly reduced by fungal treatment from second oviposition period onwards. Oothecal hatch of fungally challenged females was reduced by 46-49%, oothecal viability by 48-85%, and nymphal production by 22-35%. Only treated females showed an effect on oothecal production, oothecal hatch, and nymphal production, although oothecal hatch was also governed by treated males at a higher significance level. Our results on virulence and horizontal transmission of fungal conidia of M. anisopliae EAMa 01/121-Su strain and its sublethal reproductive effects on German cockroach females are discussed in terms of its potential to decrease the pest status of B. germanica in the short and long terms.     

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。     

Starvation induced stress and the susceptibility of the Colorado potato beetle,Leptinotarsa decemlineata,to infection by Beauveria bassiana

Starvation of second instar Colorado potato beetle larvae for 24h immediately after treatment with Beauveria bassiana conidia increased susceptibility to the pathogen and subsequent sporulation of cadavers but decreased time to larval death. In feeding studies, B. bassiana-treatment had no effect on subsequent larval development, and mortality occurred 5-6 days after treatment. Twenty-four hours of starvation alone retarded subsequent larval development but did not affect mortality. Mortality of B. bassiana-treated starvation stressed larvae occurred 4-5 days after treatment. Both B. bassiana treatment and 24h starvation significantly reduced total foliage consumption and daily weight gains. On the day of treatment, B. bassiana had no effect on the efficiency with which food was converted to biomass (ECI). ECI was not affected by B. bassiana or starvation alone on the day following treatment but was significantly affected by a combination of both. When larvae were exposed to a range of limited food quantities, ECI decreased with decreasing food availability but only extreme stress (starvation for 24h) increased susceptibility to B. bassiana. Topical application of Dacryodes excelsa resin (an antifeedant) to potato leaves caused a concentration dependent reduction in foliage consumption and weight gain by second instar larvae but did not affect larval mortality. When larvae were exposed to a fixed concentration of B. bassiana and a range of antifeedant concentrations there were significant linear relationships between 24h larval weight gain and mortality and 24h larval weight gain and sporulation. The interaction between starvation stress and the susceptibility to B. bassiana infection is discussed and its possible implications in pest management considered.     

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.     

Selection of a highly virulent fungal isolate, Metarhizium anisopliae CLO 53, for controlling Hoplia philanthus

The June beetle, Hoplia philanthus Füessly (Coleoptera: Scarabaeidae), has become a widespread and destructive insect pest of lawns, sport turf, pastures, and horticultural crops in Belgium. The virulence of 34 entomopathogenic fungal isolates from the genera Metarhizium, Beauveria, and Paecilomyces to third-instar H. philanthus was tested in bioassays by dipping larvae in 10(7)conidia/ml suspensions. Two isolates of Metarhizium anisopliae (CLO 53 and CLO 54) caused maximally 90% mortality 10 weeks post-inoculation while other isolates only caused mortalities between 10 and 62%. The virulence of M. anisopliae CLO 53 was further tested by exposing H. philanthus larvae to conidial serial concentrations of 10(4)-10(9)conidia/g sandy soil for up to 11 weeks at 15, 20 or 25 degrees C. Mortality was dependant on the fungal concentration, exposure time, and temperature. Eleven weeks after inoculation, the LC50 values for this isolate ranged from 1.3 to 4.0 x 10(6), 1.0 to 3.2 x 10(5), and 2.5 x 10(4) to 10(5)conidia/g soil at 15, 20, and 25 degrees C, respectively. The LT50 values for this isolate ranged from 3.5 to 21.7, 2.4 to 18.7, and 2.9 to 16.1 weeks at concentrations of 10(9) and 10(4)conidia/g soil at 15, 20, and 25 degrees C, respectively. In glasshouse pot experiment with perennial ryegrass (Lolium perenne L.), the isolate CLO 53 caused mortalities of 50 and 88% of H. philanthus larvae 10 weeks after application of 10(4) and 10(6)conidia/cm(2) soil surface, respectively. The present results suggest that the Belgian isolate CLO 53 has excellent potential for biological control of H. philanthus.     

Potential capacity of Beauveria bassiana and Metarhizium anisopliae in the biosorption of Cd2+ and Pb2+

In this study Beauveria bassiana and Metarhizium anisopliae were used as inexpensive and efficient biosorbents for Pb(II) and Cd(II) from aqueous metal solutions. The effects of various physicochemical factors on Pb(II) and Cd(II) biosorption by B. bassiana and M. anisopliae were studied. The optimum pH for Cd(II) and Pb(II) biosorption by two fungal species was achieved at pH 6.0 for Pb(II) and 5.0 Cd(II) at a constant time of 30 min. The nature of fungal biomass and metal ion interactions was evaluated by Fourier transform infrared. The maximum adsorption capacities (q(max)) calculated from Langmuir isotherms for Pb(II), and Cd(II) uptake by B. bassiana were 83.33±0.85, and 46.27±0.12 mg/g, respectively. However, the q(max) obtained for Pb(II) uptake by M. anisopliae was 66.66±0.28 mg/g, and 44.22±0.13 mg/g for Cd(II). B. bassiana showed higher adsorption capacity compared to M. anisopliae. The data obtained imply the potential role of B. bassiana and M. anisopliae for heavy metal removal from aqueous solutions.     

Conidium production by insect pathogenic fungi on commercially available agars

AIMS: Conidium production by three species of insect pathogenic fungi, Metarhizium anisopliae, Beauveria bassiana and Verticillium lecanii, was assessed on various depths and types of commercially available agars. METHODS: Conidium production was assessed after 14 d of growth on commercially available media as well as at three different agar depths. RESULTS: Metarhizium anisopliae and B. bassiana isolates showed greatest conidium production on potato dextrose agar (PDA) at a depth of 2 mm, whereas V. lecanii showed greatest conidium production on yeast extract-peptone-dextrose agar (YPDA) regardless of agar depth. Optimum conidium production for M. anisopliae and B. bassiana was not only dependent upon the isolate used but also on the medium type and agar depth. SIGNIFICANCE AND IMPACT OF THE STUDY: Conidia are the infective structures for insect pathogenic fungi and this study suggests a rationale basis for consistent conidium production for laboratory and commercial practices.     

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.