Investigating the feasibility of short-duration hot water treatments for apple disinfestation

The presence of live pests on packed apples is a concern for many of New Zealand's export markets. Greedy and latania scale, onion thrips, apple leafcurling midge (diapausing larvae) and obscure mealybug were subjected to hot water treatments (HWT) of 49.5, 51.0 or 52.5°C for either 1, 2 or 3 min. Latania, greedy scale and onion thrips were the most susceptible pests to HWT, with either 2-3 min at 49.5°C or ≥ 1 min at 51.0 or 52.5°C achieving >80% mortality. HWT of 52.5°C for 1-3 min consistently achieved >90% mortality of apple leaf curling midge diapausing larvae. Obscure mealybug was the most tolerant species tested, with mortalities of 60-70% at 51.0 or 52.5°C for 2 or 3 min. A HWT of 51°C for 2 min did not affect quality of 'Royal Gala', 'Fuji' and 'Braeburn' apples. There is potential for short-duration HWTs to achieve high mortalities of a range of insects, while resulting in minimal damage to apple fruit.