Boysenberries: Control of botrytis fruit rot by fungicides

Abstract

Abstract The efficacy of fungicides and the optimum time of application were evaluated in spray programmes for control of botrytis fruit rot (caused by Botrytis cinerea Pers.: Fr.) in export boysenberries (Rubus hybrid). All fungicides tested controlled the disease, with dicarboximides (iprodione, myclozolin, procymidone, vinclozolin) and dichlofluanid being more effective than captan, thiram, or folpet. Avoiding dicarboximide sprays after 10% blossom (two applications of dicarboximide before 10% blossom), followed by folpet until mid harvest resulted in slightly more berry rot than a full dicarboximide programme (9 applications), but did not reduce marketable yield: therefore, a reduced use of dicarboximides is recommended to avoid problems associated with the resistant strains of B. cinerea identified in New Zealand. Degradation of dicarboximide residues on fruit after programmes of 9 applications followed first-order kinetics with calculated half-lives of 10–12 days for iprodione, 9 days for procymidon...