Low Efficacy of Isaria fumosorosea against Box Tree Moth Cydalima perspectalis: Are Host Plant Phytochemicals Involved in Herbivore Defence against Fungal Pathogens?

Abstract

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.

Molecular characterization of an Isaria fumosorosea (Wize) native strain, and its pathogenicity on Eublemma amabilis (Lepidoptera: Noctuidae)

“…Abnormal changes in emerged adults having crippled wings was observed for the first time in E. amabilis when treated with I. fumosorosea strain, which was a significant finding. As a result, the deformed adults fail to perform normal flight behavior and mating, which was earlier reported in Cydalima perspectalis and Spodoptera litura (Zemek et al 2020). The egg mortality was found the highest (40.00%) at 1 × 10 7 spore/ml upon infection, which was significantly lower as compare to other stages of E. amabilis, which proposed that the egg stage was the most resistant stage to fungal infections (Mochi et al 2009).…”

Virulence of Beauveria bassiana Strains Isolated from Cadavers of Colorado Potato Beetle, Leptinotarsa decemlineata

“…Moreover, several studies have documented that the persistence of EPF spores on plants is limited by many factors such as temperature, rainfall, low humidity, solar radiation, plant chemistry, host plant genotype, fungal strain, etc. [58][59][60][61][62][63][64][65][66][67][68][69].…”

Efficacy of soil isolates of entomopathogenic fungi against the bulb mite, Rhizoglyphus robini (Acari: Acaridae)

“…Reference strain CCM 8367 of I. fumosorosea caused 40% mortality which was slightly higher compared to the two other I. fumosorosea strains tested. This strain was reported to be a promising biocontrol agent against several insect pests (Hussein et al 2013(Hussein et al , 2016Prenerová et al 2013) although recent findings demonstrated that some pests might be resistant to infection (Zemek et al 2020). The strain also turned out to be virulent against T. urticae (Zemek et al 2016).…”