High-pressure washing treatments to remove obscure mealybug (Homoptera: Pseudococcidae) and lightbrown apple moth (Lepidoptera: Tortricidae) from harvested apples

Mixed life stages of obscure mealybug, Pseudococcus viburni (Signoret), and late 1st-instar or early 2nd-instar lightbrown apple moth, Epiphyas postvittana (Walker), on 'Royal Gala' apples (Malus domestica Borkhausen) were exposed to standard packhouse processing with and without addition of high-pressure apple washer treatments. Insect removal and mortality were assessed. After standard packhouse processing approximately equal to 60% of P. viburni remained on their host apples. The 2 high-pressure apple washer treatments (500 and 800 psi at 2.0 rods/s) were equally effective and significantly reduced the number of P. viburni on apples compared with the packhouse control. High-pressure apple washer removal by location decreased in the following order: calyx cavity outside the sepals > cheek approximately equal to stem cavity greater than or equal to calyx beneath sepals. About half of the E. postvittana larvae infesting apples was removed by standard packhouse processing. Removal rates were similar for all locations on open-calyxed apples. However, no removal occurred from the calyx beneath the sepals if the apple calyx was closed. All 4 high-pressure apple washer treatments tested (500 and 800 psi at 1.0 and 2.0 rods/s) halved the number of larvae on the apple exterior relative to the packhouse control. The pattern of removal for larvae on open-calyxed apples was calyx outside sepals approximately stem cavity > calyx beneath the sepals approximately equal to cheek. A similar pattern was evident for larvae on closed-calyxed apples, except insects beneath the sepals evaded removal. The persistence of insects on the apple cheek reflects the high proportion of larvae inside tunnels in this location compared with other apple locations. Removal of internally positioned insects was much lower than that of externally positioned insects.