Evaluation of a non-chemical disinfestation treatment on quality of pome fruit and mortality of lepidopterous pests

Abstract

Australian pome fruit exports to northern America and Japan are rejected if they contain lightbrown apple moth (Epiphyas postvittana Walker) or codling moth (Cydia pomonella Linnaeus) respectively. A warm controlled atmosphere (CA) disinfestation treatment (72 h at 28˚C at 0, 1 or 2 kPa O₂ ), followed by varying lengths of cold storage (5 weeks, 10 weeks or 6 months), is described. Four cultivars were studied: Packham’s Triumph pears (Pyrus communis Linnaeus); Royal Gala; Fuji and Pink Lady apples (Malus domestica Borkh.). Consumer panels found that fruit subjected to the 2 kPa O₂ warm CA treatment and cold storage were as acceptable as control fruit. This is an important finding as previously published results for a harsher treatment described treated fruit (especially Pink Lady) as being less acceptable than controls. Some advanced ripening was observed for treated Packham’s Triumph pears. After 5 and 10 weeks cold storage, treated Royal Gala apples were generally firmer than the controls. Insects were also subjected to the 2 kPa O₂ warm CA treatment. The most tolerant life stage (MTS) of lightbrown apple moth was the sixth instar with an LT₉₅ of 37 days cold storage (0.5˚C) after the 2 kPa O₂ warm CA treatment. Comparison with previous research suggests that the 2 kPa O₂ warm CA treatment approximately halves the time required in cold storage for effective control of late instar lightbrown apple moth. A LT₉₅ of 81 days was achieved for fifth instar codling moths (considered to be the MTS) and this may need to be reduced for export to Japan. Preliminary observations suggested that there may not be substantial difference between the resistance of non-diapausing and pre-diapausing codling moth larvae to the warm CA followed by cold treatment.