Pre-treatment dips to enhance the removal of apple leafcurling midge from apples using high pressure washing

Abstract

The presence of apple leafcurling midge (ALCM) on apples is of concern for many of New Zealand’s export apple markets. High pressure washing (HPW) systems have been implemented in export packhouses to reduce the risks associated with various pests; however, higher removal rates of ALCM are required to improve access to challenging markets. A range of pre-treatment dips to improve ALCM removal efficacy when applied before HPW were tested, and the impact of these pre-treatment dips on pest viability determined. Removal of ALCM cocoons by HPW alone was 41%, compared with pre- treatments of hot water at 51?C (66%), Saturate® (58%), Prospect oil® (57%), malic acid (53%), citric acid (48%), lactic acid (46%), acetic acid (39%), HarvestCide® (37%) or sodium bicarbonate (37%). However, only the hot-water treatment significantly enhanced removal compared with HPW alone. In a second trial, removal of ALCM cocoons with HPW was 69% and hot water + UV-C increased removal to 76%, although this difference was not statistically significant. Overall, none of the pre-treatment dips was found to reduce ALCM viability significantly compared with HPW alone.