Timing of sulphur spray application for control of hazelnut big bud mites (Phytoptus avellanae and Cecidophyopsis vermiformis)

Abstract

Eriophyoid big bud mites are key pests of hazelnuts throughout the world, although little is known of the identity and impact of the species on New Zealand hazelnut crops. The objective of this study was to determine the efficacy of and optimum timing for sulphur application to control these mites. A field experiment tested the application of sulphur (1.12 g ai/tree) at 3, 62 and 88% accumulated mite emergence from overwintering big buds. The greatest reduction in emerging mite numbers was achieved with an application at 62% emergence. The importance of determining peak mite emergence, the appearance of hazelnut buds and weather conditions to optimise the time to apply control measures are discussed.