He told association members at a tree fruit event at EMR in Kent on 24 November that, apart from achieving the best possible control of the pest during the summer, it was important to reduce the overwintering population. As a result, its numbers will be much lower going into the next season.
Sex pheromone traps have been used for about 40 years, Cross explained. Despite intensive spray programmes against the pest, based on trap threshold catches, high year-on-year catches still occur and growers are failing to adequately reduce numbers of overwintering larvae and pupae.
These facts indicate that sprays are not being timed accurately enough during the critical egg-laying periods that produce the overwintering moth stages.
The Horticultural Development Company (HDC) project aims to answer questions such as how do pheromone trap catches relate to the flight of gravid females and egg laying and would the better timing of sprays kill larvae that subsequently overwinter and result in better long-term control of the pest?
It will also determine what proportion of the overwintering stages arise from the pest's first and second generations and whether the RIMpro-Cydia computer model for predicting the best spray timing offers any improvements over current practice.
Two unsprayed Kent orchards — organic Jonagold at Nichol Farm in Teynham and Worcester Pearmain at Owl House Farm in Lamberhurst — are involved in the HDC project, Cross explained.
In the first year the moth was monitored weekly from May to October, the larvae collected and measured and the temperatures logged. From this information it will be possible to determine the best spray timings and which larvae are likely to overwinter.