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 postvi ttana (Walker), on 'Royal Gala apples (Malus domestica Borkhausen) were exp osed to standard packhouse processing with and without addition of high-pre ssure apple washer treatments. Insect removal and mortality were assessed. After standard packhouse processing approximate to 60% of P, viburni remain ed on their host apples. The 2 high-pressure apple washer treatments (500 a nd 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. Hig h-pressure apple washer removal by location decreased in the following orde r: calyx cavity outside the sepals > cheek approximate to stem cavity great er than or equal to calyx beneath sepals. About half of the E. postvittana larvae infesting apples was removed by standard packhouse processing. Remov al 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 rodsls) halved the number of larvae on the apple exterior r elative to the packhouse control. The pattern of removal for larvae on open -calyxed apples was calyx outside sepals approximate to stem cavity > calyx beneath the sepals approximate 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 pr oportion of larvae inside tunnels in this location compared with other appl e locations. Removal of internally positioned insects was much lower than t hat of externally positioned insects.