Biochemical responses of False Codling Moth, Thaumatotibia leucotreta to low temperature and modified atmospheres

Controlled atmospheres (i.e. gases such as carbon dioxide, oxygen or nitrogen) are frequently used in postharvest control to augment temperature treatments for fruit disinfestation. However, the success of such treatments is erratic and does not always result in additional mortality, particularly among major Lepidopteran pests (e.g. false codling moth Thaumatotibia leucotreta). Here, we investigate the mechanisms underlying low temperature tolerance in T. leucotreta, together with how controlled atmospheres affect this tolerance. Fifth instar larvae were exposed to a range of temperature conditions (0°C, 4°C, 25°C, 35°C), high carbon dioxide (6% CO₂) and low oxygen (2% O₂) treatments, both separately, as well as in combination for various durations; prior to a standard low temperature exposure at -1°C. During these experiments, larvae were assayed for tissue viability, membrane lipid composition, mortality, heat shock protein 70 (HSP70) and cryoprotectant expression levels. Preliminary results indicate that HSP70 changed significantly over the course of, and between, the experiments. Twenty four hours of 6% CO₂ at 4°C followed by recovery at 25°C for 2 h, cold exposure of 3 days at -1°C, 25°C for 2 h, then 5 days at -1°C resulted in 100% mortality. This work provides insights into the molecular responses which T. leucotreta employ to survive exposures to low temperatures and/or controlled atmosphere treatments. In addition, this knowledge, after additional fruit trials, may lead to improved controlled atmosphere/temperature treatments for control of T. leucotreta.