On the susceptibility of the box tree moth Cydalima perspectalis to Anagrapha falcifera nucleopolyhedrovirus (AnfaNPV)

Abstract

The box tree moth Cydalima perspectalis is an invasive insect pest in many European countries. Caterpillars of this species cause widespread damage on box tree plants. In this study, a new opportunity to control this pest with the baculovirus Anagrapha falcifera nucleopolyhedrovirus (AnfaNPV) was investigated. Initially, AnfaNPV was identified to infect larvae of Diaphania nitidalis by determining the partial nucleotide sequence of the three highly conserved genes polh, lef-8 and lef-9 of the infection causing agent. Two AnfaNPV isolates, termed Dn10 and BI-235, were then propagated in larvae of C. perspectalis and purified by sucrose density centrifugation. A bioassay using leaf disks of box tree was established to evaluate the virulence of both AnfaNPV isolates to neonate C. perspectalis larvae. After 7days, the mortality of larvae was scored and median lethal concentrations (LC50) were determined to 7.8×105OBs/ml for isolate BI-235 and 2.3×106OBs/ml for isolate Dn10 by using probit analysis. Thus, AnfaNPV BI-235 was significantly more virulent to neonate C. perspectalis larvae than Dn10 based on a three times higher LC50 value. Additionally, light and transmission electron microscopic investigations verified high rates of infection in fat body, epidermis and tracheal matrix of C. perspectalis by both AnfaNPV isolates BI-235 and Dn10. In conclusion, the performed laboratory experiments indicate the susceptibility of C. perspectalis to AnfaNPV.