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

sp. is an important native and ornamental tree in Europe threatened by a serious invasive pest . 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 trees grown wildly or in city parks. Laboratory experiments were conducted to assess the efficacy of entomopathogenic fungus strain CCM 8367 against . The last-instar larvae of the box tree moth were treated by the suspension of fungus conidia at concentrations ranging from 1 × 10 to 1 × 10 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 to . 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 leaves significantly inhibits both the germination of conidia and fungus growth. It can be speculated that the strain CCM 8367 of is not a potent biocontrol agent against 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.