Response of ‘Royal Gala’ apples to hot water treatment for insect control

Abstract

Abstract The response of ‘Royal Gala’ apples ( Malus domestica Borkh.) to hot water treatments (HWTs) for the control of quarantine leafroller species was investigated. ‘Royal Gala’ apples from two orchards from each of two regions of New Zealand, and up to three harvest dates, were hot water treated at 44, 45 or 46°C for 35, 40 or 45 min. Following treatment, fruit were placed in cold storage at 0.5°C for 0, 4, 7 or 10 weeks, then held at 20°C for 7 days prior to assessment for quality. A number of HWTs were associated with damage in the form of skin browning and internal breakdown. Incidence of damage increased with increasing temperature and treatment duration, and with increasing length of time in cold storage. Incidence of HWT-associated damage varied between regions, harvest dates and orchards. Early harvest fruit had lower levels of damage than mid and late harvest fruit. A HWT of 44°C for 35 min, followed by 7 or 10 weeks of cold storage at 0.5°C, was found to be tolerated by all fruit tested. This treatment is effective in controlling the quarantine leafroller pests, Epiphyas postvittana (Walker), Planotortrix octo Dugdale and Ctenopseustis obliquana (Walker).