engleski

Pathogenicity of entomopathogenic nematodes Steinernema feltiae combined with entomopathogenic fungi Beauveria bassiana and B. pseudobassiana

Insect pest management programs mostly depend on chemical pesticides. Due to increased environmental awareness and withdrawal of many efficient chemicals from the market, new methods and tools of pest suppression are needed. Entomopathogens, such as nematodes and fungi are promising alternative to chemicals. Croatian strains of entomopathogenic nematodes (EPN) and entomopathogenic fungi (EPF) are reported recently. We tested the pathogenicity of EPN Croatian strain Steinernema feltiae (ISO 16) and EPF Croatian species Beauveria bassiana (isolated from Dendrolimus pini, Skradin) and B. pseudobassiana (isolated from Corythucha arcuate, Spačva). Greater wax moth (Galleria mellonella)larvae were treated with 200 IJs insect-1 alone or in combination with one of the tested EPF, and EPF alone in laboratory bioassay. Beauveria bassiana was used in dose of 1 ml per Petri dish and 10 insect larvae in a concentration of 7 × 107 spores ml-1 and B. pseudobassiana in a concentration of 4.4 × 107 spores ml-1, respectively. Experiment was conducted with three repetitions of each treatment. Mortality of insect larvae was monitored during 96 h after exposure. Single species and combined application of entomopathogens caused 100 % mortality of insect larvae after 48 h, and all insects survived in control dish after 96 h. The antagonisms between tested species of entomopathogens was not detected. Insect cadavers were colored brown from all treatments, except from cadavers treated with EPN and B. pseudobassiana, and B. pseudobassiana alone. Those cadavers were colored in light brown or beige. Progeny of EPN was abundant, and lower populations were found from combined treatments. Increase in efficacy when combining two entomopathogens was not recognized, since their pathogenicity was identical for all tested combinations. Further investigations are needed, with lower concentrations of EPN and/or EPF and in different environments, and insect hosts. The combined use of S. feltiae with B. bassiana or B. pseudobassiana should be considered as an integrated approach that could increase the efficacy of control of agricultural and forestry pests, all in favor of biodiversity protection and sustainable plant production.

entomopathogens ; mortality ; Galleria mellonella ; synergetic effect

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