Transmission of Botrytis cinerea by lightbrown apple moth larvae on grapes

Larvae of lightbrown apple moth, Epiphyas postvittana Walker (Lepidoptera: Tortricidae) (LBAM) transmitted Botrytis cinerea Pers. Fr. (Bc) on veraison bunches in a field experiment at Lenswood, South Australia. The presence of Bc‐contaminated LBAM larvae at veraison resulted in up to 59% of bunches infected with Bc at harvest, compared with 27% of bunches with uncontaminated larvae and 18% when no larvae were added. Under these field conditions, up to an additional 13% by weight of berry damage could be attributed to LBAM transmission, compared with controls. There was little evidence that the presence of contaminated LBAM larvae on bunches at flowering increased the incidence of infected bunches at harvest. Surveys of LBAM larvae collected from vines during the 1996/97 season showed up to 32% of larvae at Eden Valley were naturally contaminated with Bc, while the frequency at Padthaway and Coonawarra did not exceed 5%. Laboratory experiments demonstrated that LBAM larvae carry conidia of Bc on their cuticle, which explains the transmission within bunches observed in the field. Viable propagules of Bc were recovered from faecal pellets of LBAM. The habit of faecal dispersal by LBAM larvae may contribute to the build‐up of Bc inoculum in a vineyard.