Isolation, identification, biological characteristics, and pathogenicity of an entomogenous fungus against the Egyptian mealybug, Icerya aegyptiaca (J.) (Hemiptera: Monophlebidae)

Abstract

Abstract Background In this study, an entomogenous, fungus was isolated from the Egyptian mealybug, Icerya aegyptiaca (J.) (Hemiptera: Monophlebidae) on the parasol leaf tree, Macaranga tanarius, in China where evaluated as a biocontrol fungus to reduce the population of the target insect. The strain was identified as Aspergillus parasiticus by morphological and phylogenetic analysisand named ZHKUAP1. The biological characteristics, pathogenicity, and field control effect of the strain were determined. Results The most suitable medium for the mycelial growth of strain ZHKUAP1 was PPDA medium, with an optimum temperature of 30 °C and pH 7, in addition to glucose and peptone as carbon and nitrogen sources. The optimum sporulation conditions were the PPDA medium at 30 °C and pH 6, using the soluble starch and beef extract as carbon and nitrogen sources. The mycelial growth and spore production of strain ZHKUAP1 were stopped at 70 °C and above, indicating that it was not resistant to high temperatures. High concentrations of spore suspension, against young insect age, resulted high corrected mortality, as well as decreased the median lethal time. When the spore concentration was 1 × 108 cfu/ml, the corrected mortality of the second nymph was 88.33%, and the LT50 was 0.66 day. After 10 days of inoculation, the LC50 of the second instar nymph was the smallest, reaching 4.07 × 104 cfu/ml. On the 10th day of the field experiment, the corrected mortality was 76.45%, indicating that the A. parasiticus strain ZHKUAP1 had strong pathogenicity on I. aegyptiaca population. Conclusions The indoor toxicity of the strain to I. aegyptiaca was determined, and the field control effect of the pathogen was explored on this basis. The results have important application prospects in the biological control of I. aegyptiaca.