Secondary Metabolites of Entomopathogenic Fungi, Biological Alternative for the Control of Agricultural Pests and Disease: Present and Perspectives

The use of entomopathogenic fungi (EF) in recent years has been highly effective against the different orders of insects considered pests of agricultural importance and their conidia have been commonly applied, but it has been reported that these are sensitive to the environmental conditions. For this reason, biopesticides products have been formulated based on secondary metabolites, recently. These biomolecules participate as biological control agent, such as: cyclic depsipeptides, amino acids, polyketides, polyphenols and terpenoids, affecting their morphology, life cycle and insect behavior. The use of secondary metabolites of entomopathogenic fungi opens the possibility of application in a more efficient way for the control of agricultural pests in a compatible with the environment and human health;therefore, it is important to know, analyzing the type of molecules, their effects, and their different methods of application.

Interactions between Entomopathogenic Fungi and Entomophagous Insects

Direct treatment of predators with entomopathogenic fungi (EPF) at different concentrations revealed that some species, like Beauveria bassiana and Metarhizium anisopliae, were found to have detrimental effects on all developmental stages of some predator species. Other species, like Numoraea rileyi and Paecilomycis fumosorosius, showed little or no effect on treated predators. Adult predators were found to avoid feeding on fungi-infected prey. EPF could be isolated from hibernating or field-collected coccinellids. Some studies indicated that combining a fungus with a predator could increase the rate of insect control in the field. As for parasitoids, this review indicates that the developmental stages of the egg parasitoids can develop successfully in host eggs treated with fungi. However, fungus-infected hosts negatively impact the development of larval parasitoids inside such hosts and this impact depends on the species and concentration of the fungus as well as the time between infection and parasitism. Some parasitoid females can discriminate between fungus-infected and uninfected hosts and do not parasitize the infected hosts. With appropriate timing, the parasitoids or predators could be combined with fungi for the biological control of insects in the field.

Effect of Ultraviolet Radiation on Fungi <i>Beauveria bassiana</i>and <i>Metarhizium anisopliae</i>, Pure and Encapsulated, and Bio-Insecticide Action on <i>Diatraea saccharalis</i>

The effect of ultraviolet radiation on entomopathogenic fungi can be very prejudicial for causing damage to the conidia. Formulations can help protecting these fungal structures against radiation. The objective of this study was to evaluate the effect of UV radiation on pure and encapsulated conidia Beauveria bassiana and Metarhizium anisopliae sensu lato, and to evaluate their pathogenicity on the sugarcane borer, Diatraea saccharalis. The pure conidia and the sodium alginate capsules containing the fungi were submitted to the ultraviolet radiation in different temperatures and exposure times. On the pure conidia, the radiation had a deleterious effect after 5 minutes of exposure, going from 94% to 52% germination for B. bassiana and from 96% to 54% for M. anisopliae. The alginate formulation protected the B. bassiana conidia against the radiation in all times they were evaluated (15 minutes to 48 hours), because, even after exposure, the fungi remained viable. The dry encapsulated conidia B. bassiana caused 79.6% mortality of the studied pest and the M. anisopliae caused only 10%.

Effect of Ultraviolet Radiation on Fungi Beauveria bassiana and Metarhizium anisopliae, Pure and Encapsulated, and Bio-Insecticide Action on Diatraea saccharalis

The effect of ultraviolet radiation on entomopathogenic fungi can be very prejudicial for causing damage to the conidia. Formulations can help protecting these fungal structures against radiation. The objective of this study was to evaluate the effect of UV radiation on pure and encapsulated conidia Beauveria bassiana and Metarhizium anisopliae sensu lato, and to evaluate their pathogenicity on the sugarcane borer, Diatraea saccharalis. The pure conidia and the sodium alginate capsules containing the fungi were submitted to the ultraviolet radiation in different temperatures and exposure times. On the pure conidia, the radiation had a deleterious effect after 5 minutes of exposure, going from 94% to 52% germination for B. bassiana and from 96% to 54% for M. anisopliae. The alginate formulation protected the B. bassiana conidia against the radiation in all times they were evaluated (15 minutes to 48 hours), because, even after exposure, the fungi remained viable. The dry encapsulated conidia B. bassiana caused 79.6% mortality of the studied pest and the M. anisopliae caused only 10%.

Effectiveness of entomopathogenic fungal strains against poplar/willow weevil(Cryptorhynchus lapathi L.)larvae

The poplar and willow weevil,Crypto rhynchus lapathi L.,a major universally destructive wood-boring insect has become one of the important quarantine pests that is extremely destructive to forestry development and needs to be controlled.Entomopathogenic fungi(EPF) are considered safe and friendly for humans and the environment and play important roles in controlling insect pest populations.In this study,the screening of entomopathogenic fungi for control of C.lapathi is reported through the evaluation of virulence of four fungal Beauveria bassiana(CFCC81428,CFCC83116,CFCC83486,CFCC87297)strains,one B.brongniartii(CFCC83487) strain and one Metarhizium anisopliae(CFCC88953) strain.The virulence of the different strains was appraised by correct mortality rate,cumulative mortality rate,median lethal concentration(LC_(50)) and median lethal time(LT_(50)).B.bassiana strains CFCC81428 and CFCC83116 were the most virulent among the six strains with a mortality up to 100%,and the LT_(50) were 2.7 and 3.1 days.Five conidia concentrations of three strains(CFCC81428,CFCC83116 and CFCC87298) that caused high virulence was screened for dose-relationship.Their effect on controlling C.lapathi larvae were also determined under field condition by brushing conidia suspensions on C.lapathi larvae infested in a poplar trunk.The cumulative rate in the field was lower than those obtained from the laboratory,but the order of the virulence of different strains did not change.Mortality in all three strains occurred at their highest concentration(1.0 × 10^(8) conidia mL^(-1)).Under field conditions,the CFCC81428 strain was the most effective,causing mortalities of 80.3% and 75.2%in two plots in Beipiao and Lindian counties,respectively,followed by CFCC83116(69.1%,66.6%) and CFCC87298(60.7%,59.3%).Based on our results,the B.bassiana strain CFCC81428 has the potential as a biological insecticide to control C.lapathi larvae.

不同森林生态系中球孢白僵菌遗传多样性比较研究(英文)

ISSR molecular marker technology was adopted to conduct comparison analysis on genetic diversity level and population genetic structure of Beauveria bassiana population in natural secondary forest （Langyashan national forest park） in Chuzhou City of Anhui Province and artificial pure pine forest （Magushan forest farm） in Xuancheng City of Anhui Province.Seven primers were selected to conduct PCR amplification on total 222 strains of B.bassiana in two populations,a total of 58 unique amplified loci were obtained through amplification,the number of polymorphic loci was 56,the percentage of polymorphic loci was 96.55%,Nei＇s genetic diversity was 0.299 3,Shannon information index was 0.459 3,genetic differentiation coefficient among populations （Gst） was 0.128 3,gene flow Nm=3.398 4;the gene flow between the two populations was small,genetic differentiation was relatively large,being 12.83%,this may be caused by human selective pressures and barrier of gene flow;the genetic variation level of B.bassiana populations in Langyashan was relatively high（PPL=96.55%,H=0.278 1,I= 0.429 9）;the genetic variation level of B.bassiana populations in Magushan was relatively low（PPL=93.10%,H=0.255 2,I= 0.382 5）.The genetic diversity of B.bassiana from the primary forest in Dabieshan was studied（PPL=81.00%,H=0.318 7,I= 0.478 2）,indicating that the genetic diversity of B.bassiana populations in Dabieshan with complex ecological environment was the highest,followed by the populations in natural secondary forest,and the genetic diversity in artificial pure pine forest was the lowest.Nei＇s genetic distance was adopted to construct the genetic relationship dendrogram of B.bassiana individuals collected from Langyashan and Magushan,from the cluster analysis of UPGMA,the strains from the same collection places clustered together.

Research and development of Cordyceps in Taiwan

Cordyceps is treasured entomopathogenic fungi that have been used as antitumor,immunomodulating,antioxidant,and pro-sexual agent.Cordyceps,also called DongChongXiaCao in Chinese,Yartsa Gunbu(Tibetan),means winter worm-summer grass.Natural Cordyceps sinensis with parasitic hosts is difficult to be collected and the recent findings on its potential pharmacological functions,resulted in skyrocketing prices.Therefore,finding a mass-production method or an alternative for C.sinensis products is a top-priority task.In this review,we describe current status of Cordyceps research and its recent developments in Taiwan.The content and pharmacological activities of four major industrial species of Cordyceps(C.sinensis,Cordyceps militaris,Cordyceps cicadae and Cordyceps sobolifera)used in Taiwan,were reviewed.Moreover,we highlighted the effect of using different methods of fermentation and production on the morphology and chemical content of Cordyceps sp.Finally,we summarized the bottle-necks and challenges facing Cordyceps research as well as we proposed future road map for Cordyceps industry in Taiwan.

Effects of Aschersonia aleyrodis on the life table and demographic parameters of Bemisia tabaci

The present study reports the sublethal effects of the entomopathogenic fungus, Aschersonia aleyrodis（Webber） on Bemisia tabaci（Gennadius）（Homoptera： Aleyrodidae）. A fungal suspension of A. aleyrodis isolate Aa005 containing 1×107 conidia mL^-1 was sprayed against B. tabaci on eggplant leaves under greenhouse conditions. The effects of fungal application on survival as well as life table parameters of the whitefly were observed at different post inoculation periods. The results indicated that A. aleyrodis can significantly affect the survival of 1st, 2nd, and 3rd nymphal instars of B. tabaci. Developmental periods of different instar nymphs were not affected by fungal application. A. aleyrodis spores persisted well and significantly affected the survivorship of young instar nymphs of B. tabaci at different post incubation periods. Life table results suggested that A. aleyrodis has no impact on general fecundity and longevity of B. tabaci. When the pathogen was exposed to the open environment and maintained for a relatively longer period, a reduction in the reproductive rate and intrinsic rate of increase was caused by the fungal spores, though the sublethal effects were not as good as the control treatment. The results suggest that the ability of spores to suppress an increase in whitefly population persists well after incubation of spores to the external environment（up to 9 days）.

Bemisia tabaci： The current situation in the UK and the prospect of developing strategies for eradication using entomopathogens

The sweetpotato whitefly, Bemisia tabaci （Gennadius） （Hemiptera： Aleyrodidae） remains a serious threat to crops worldwide. The damaging B-biotype is of specific economic concern because it is an effective vector of over 111 viruses from several fam- ilies, particularly geminiviruses. Bemisia tabaci is regularly intercepted on plants coming into the UK where it is subjected to a policy of eradication. The UK maintains Protective Zone status against this pest. A main pathway of entry of B. tabaci into the Protected Zone involves propagating material, especially Poinsettia （Euphorbia pulcherrima）. With increased insecticide resistance continuously being recorded, B. tabaci is becoming more difficult to control/eradicate. Recent research involving both entomopathogenic nematodes and fungi is showing much potential for the development of control programs for this pest. Both the nematode Steinernemafeltiae and the fungus Lecanicillium muscarium have been shown to be most effective against second instar B. tabaci. Fine-tuning of the environmental conditions required has also increased their efficacy. The entomopathogens have also shown a high level of compatibility with chemical insecticides, all increasing their potential to be incorporated into control strategies against B. tabaci.

Comparison of cauliflower-insect-fungus interactions and pesticides for cabbage root fly control

Cabbage root fly （Delia radicum L.） control represents a major challenge in brassica production, therefore different management strategies for its control were tested in conventionally managed open field cauliflower production. Strategies included treatments with low-risk methods such as nitrogen lime, the insecticide spinosad and the Beauveria bassiana ATCC 74040-based biopesticide Naturalis. Their effects were compared with treatments based on nonformulated fungal species Metarhizium brunneum, B. bassiana, Clonostachys solani, Trichoderma atroviride, T. koningiopsis, and T. gamsii and commercial insecticides λ-cyhalothrin and thiamethoxam. Spinosad and thiamethoxam were pipetted to individual plants before transplanting; λ-cyhalothrin was sprayed after transplanting; nitrogen lime was applied at first hoeing. Nonformulated fimgi were delivered onto cauliflower plantlets＇ roots as a single pretransplantation inoculation. The cabbage root fly population dynamics exhibited a strong spatiotemporal variation. The lowest number of cabbage root fly pupae recovered from cauliflower roots in the field experiments was recorded in plants treated with spinosad （significant reduction）, followed by Naturalis and one of the tested M. brunneurn strains （nonsignificant reduction）. Significantly more pupae were counted in the nitrogen lime treatment. The field experiments showed that a single drench of cauliflower plantlets with spinosad offered consistent and enduring cabbage root fly control. Naturalis and nonformulated fungal isolates did not decrease cabbage root fly pressure significantly, apparently due to lack of statistical power. The implications of the substantial intra- and inter-annual pest pressure variation and the benefits of using single plant treatments are discussed, and recommendations for improvement of rhizosphere-competence utilizing biological control strategies provided.

Soil application of Beauveria bassiana GHA against apple sawfly, Hoplocampa testudinea （Hymenoptera： Tenthredinidae）： Field mortality and fungal persistence

Low impact alternatives to synthetic insecticides for the control of apple sawfly （Hoplocampa testudinea Klug） are scarce encumbering pest management in organic apple orchards. We investigated the soil persistence and field efficacy of the entomopathogenic fungus Beauveria bassiana （Balsamo） Vuillemin （BotaniGard） against apple sawfly under common organic orchard practices. We also assessed the efficacy of B. bassiana GHA and Metarhiziurn brunneum Petch （indigenous strain） against sawfly in the laboratory. Larvae treated with either fungus in the laboratory died faster than control larvae and displayed 49.4%-68.4% mycosis. In the field, B. bassiana density remained high in the week after application, during larval descent to the soil. Fungal density decreased to 25% at 49 d after application and to 0.4% after 55 weeks. Molecular markers revealed that the majority of fungal isolates recovered comprised the applied B. bassiana strain GHA. Larvae pupating in soil cages in the orchard for 49 d displayed 17% mycosis. The high efficacy under laboratory conditions was not seen in the field. B. bassiana application resulted in densities above the upper natural background level during the growing season, but reversion to background levels occurred within a year. It remains to be investigated whether this has a detrimental effect on nontarget organisms. Additional work is needed to bridge the knowledge gap between laboratory and field efficacy in orchards.

Effects of a combined infection with Paranosema locustae and Beauveria bassiana on Locusta migratoria and its gut microflora

Even though Paranosema locustae is widely used in China as a biological agent for controlling grasshoppers,the mortality rate is initially quite low.This study sought to determine whether the simultaneous use of P.locustae and Beauveria bassiana would be a more effective control strategy.Additionally,changes in the intestinal microbial communities of migratory locusts infected with the two pathogens were analyzed to investigate the roles of gut microbes in pathogen-host interactions.The mortality rate of locusts inoculated with B.bassiana and P.locustae simultaneously was not significantly higher than expected but the mortality rates of locusts inoculated with B.bassiana 3,6,and 9 days after inoculation with P.locustae were significantly higher than if their effects were additive,indicating synergism.A MiSeq analysis found that Weissella was the most common bacterium,representing 41.48%and 51.62%of the total bacteria in the mid-and hindguts,respectively,and the bacterial declines were greatest during dual infections with B.bassiana and P.locustae.The appropriately timed combined application of P.locustae and B.bassiana was more effective against locusts than either treatment alone.Moreover,the combined inoculation of the two pathogens changed the gut microflora of locusts,indicating the potential relevancy of their synergistic effects on locust control.