Entomopathogenic fungi and entomopathogenic nematodes are globally distributed soil organisms capable of infecting and killing a vast variety of insects. Therefore, these organisms are frequently used as biocontrol agents in insect pest management. Both entomopathogenic fungi and nematodes share the soil environment and thus can infest and compete for the same insect host; however, natural co-infections are rarely found due to the cryptic soil environment. Our current knowledge on their interactions within hosts mainly comes from laboratory experiments. Because of the recent trend of combining biocontrol agents to increase their efficacy, many studies have focused on the co-application of different species of EPF and EPNs against various insect pests with variable outcomes ranging from synergistic effects and additive effects to antagonism. In addition, the effect on the development and reproduction of each pathogen varies from normal reproduction to exclusion, and generally the outcomes of the interactions are dependent on pathogen and host species, pathogen doses, and the timing of infection. The present review aims to summarize the current knowledge on the interactions of entomopathogenic fungi and nematodes within an insect host and to estimate the possible effects of the interactions on natural pathogen populations and on their use in biocontrol.

• Keywords
• biocontrol, effectiveness, entomopathogenic fungi, entomopathogenic nematodes, synergy,
• Publication type
• Journal Article MeSH
• Review MeSH

The Colorado potato beetle, Leptinotarsa decemlineata (Say), is a serious, widely distributed pest of potato and other crops. This pest is able to defoliate the host plant and cause severe yield loss. Moreover, the pest quickly becomes resistant to many chemical pesticides. Therefore, the development of novel biopesticides targeting this pest is urgently needed. The purpose of this study was to obtain new strains of the entomopathogenic fungus Beauveria bassiana and assess their efficacy against L. decemlineata adults under laboratory conditions. Twelve strains were isolated from cadavers of Colorado potato beetles collected in potato fields in the Czech Republic. Test beetles were treated by suspensions of conidia at the concentration of 1 × 107 spores per milliliter and their survival was recorded daily for three weeks. The results of the bioassays revealed that all new native strains were pathogenic to L. decemlineata adults and caused mortality up to 100% at the end of the trial period with an LT50 of about 7 days. These strains were more virulent than a reference strain GHA and some of them can be recommended for the development of a new mycoinsecticide against L. decemlineata. Our findings also highlight the importance of searching for perspective strains of entomopathogenic fungi among naturally infected hosts.

• Keywords
• biological control, efficacy, entomopathogenic fungi, insect pest, mycoinsecticides, potato,
• Publication type
• Journal Article MeSH

Colorado potato beetle Leptinotarsa decemlineata is among the most destructive pests of potatoes quickly developing resistance to traditional insecticides. In the present study, we tested the effect of various species and strains of entomopathogenic nematodes on CPB adults, and subsequently, the most effective nematodes were applied alone and in combination with entomopathogenic fungus B. bassiana in pots with potato plants and in the field and their effect on the number of emerging adults was evaluated. In the experimental infections, both the nematode invasion and pathogenicity were variable, and, in several strains, the mortality reached 100%. In pot experiments, soil application of nematodes S. carpocapsae 1343 and S. feltiae Jakub and fungus significantly decreased numbers of emerging CPB adults, while, after the application on leaves, only fungal treatment was effective. The field application of fungus B. bassiana significantly decreased the number of emerging CPB adults in comparison to control sites by ca. 30% while the effect of nematodes and the nematodes-fungus combination was not significant. In conclusion, we demonstrate the necessity of thorough bioassays to select the most effective nematode strains. Entomopathogenic nematodes have the potential to effectively decrease the emergence of CPB adults, but further research is needed to improve the effectiveness in the field.

• Keywords
• Beauveria, Colorado potato beetle, Steinernema, entomopathogenic fungi, entomopathogenic nematodes, field application,
• Publication type
• Journal Article MeSH

Entomopathogenic nematodes and fungi are globally distributed soil organisms that are frequently used as bioagents in biological control and integrated pest management. Many studies have demonstrated that the combination of biocontrol agents can increase their efficacy against target hosts. In our study, we focused on another potential benefit of the synergy of two species of nematodes, Steinernema feltiae and Heterorhabditis bacteriophora, and the fungus Isaria fumosorosea. According to our hypothesis, these nematodes may be able to disseminate this fungus into the environment. To test this hypothesis, we studied fungal dispersal by the nematodes in different arenas, including potato dextrose agar (PDA) plates, sand heaps, sand barriers, and glass tubes filled with soil. The results of our study showed, for the first time, that the spreading of both conidia and blastospores of I. fumosorosea is significantly enhanced by the presence of entomopathogenic nematodes, but the efficacy of dissemination is negatively influenced by the heterogeneity of the testing arena. We also found that H. bacteriophora spread fungi more effectively than S. feltiae. This phenomenon could be explained by the differences in the presence and persistence of second-stage cuticles or by different foraging behavior. Finally, we observed that blastospores are disseminated more effectively than conidia, which might be due to the different adherence of these spores (conidia are hydrophobic, while blastospores are hydrophilic). The obtained results showed that entomopathogenic nematodes (EPNs) can enhance the efficiency of fungal dispersal.

• Keywords
• PDA plates, blastospores, conidia, dispersal, entomopathogenic fungi, entomopathogenic nematodes, soil substrate,
• Publication type
• Journal Article MeSH

Buxus sp. is an important native and ornamental tree in Europe threatened by a serious invasive pest Cydalima perspectalis. The larvae of this moth are able to defoliate box trees and cause their death. The development of novel biopesticides targeting this pest might help protect Buxus trees grown wildly or in city parks. Laboratory experiments were conducted to assess the efficacy of entomopathogenic fungus Isaria fumosorosea strain CCM 8367 against C. perspectalis. The last-instar larvae of the box tree moth were treated by the suspension of fungus conidia at concentrations ranging from 1 × 104 to 1 × 108 spores per 1 mL. Fungus infection was observed mostly in pupae, but the maximum mortality did not exceed 60%, indicating a very low susceptibility of C. perspectalis to I. fumosorosea. Furthermore, a number of ungerminated fungal conidia were found on larval cuticles using a low-temperature scanning electron microscopy. Our data also reveal that the hydroalcoholic extract from B. sempervirens leaves significantly inhibits both the germination of I. fumosorosea conidia and fungus growth. It can be speculated that the strain CCM 8367 of I. fumosorosea is not a potent biocontrol agent against C. perspectalis and low virulence of the fungus might be due to the accumulation of host plant phytochemicals having antimicrobial activity in larval cuticle of the pest.

• Keywords
• Buxus, alkaloids, antimicrobial activity, entomopathogenic fungi, invasive pests, virulence,
• Publication type
• Journal Article MeSH