325 Potential Non-Chemical Methods for Use against Thrips (Thrips tabaci) in Green Asparagus P. Simantara 1 , D. Rees 2 and A. Westby 2 1 Faculty of Agriculture at Khamphaeng Sane, Kasetsart University, Nakorn Pathom, Thailand 2 Natural Resources Institute, University of Greenwich at Medway, Chatham Maritime, Chatham, Kent, UK Keywords: asparagus, thrips (Thrips tabaci), heat treatments, high CO 2 Abstract Alternative methods for disinfestation of asparagus against thrips (Thrips tabaci) need to be developed for the Thai export trade, ensuring efficient thrips’ mortality, while maintaining quality and environmental safety. Hot air/water using temperatures of 40-60°C and high CO 2 treatments were studied at laboratory level. An appropriate treatment involving hot water at 45°C for 15 min, with or without high CO 2 treatment, followed by hydro-cooling with water at ambient temperature (~20°C) was identified. Methods to assess quality, such as objective tests (% mass loss, force measurement, colour measurement) and subjective tests (appearance, decay, off- odour, snap-test for texture) gave no indication of significant quality deterioration. Chlorophyll fluorescence and ion leakage measurements were used to assess physio- logical stress. The F v /F m ratio which indicates the intactness of photosystem II was shown to decrease immediately after all heat treatments tested, but recovered over 24h for non-damaging heat treatments (42.5 and 45°C). A rise in % K + leakage was observed that increased with treatment temperature but recovered over 24h following treatment at 45°C. High CO 2 showed neither significant detrimental effect nor indica- tion of physiological stress, and could kill thrips although not at a sufficiently high rate. Confirmatory trials to demonstrate the efficacy of these treatments in Thailand using naturally infested asparagus were carried out. The mortality rate of thrips was as high as when this method was tested in the UK. Adoption of the selected disinfesta- tion method into existing process lines in Thailand would not be too complicated. INTRODUCTION In 2006, the volume of exported fresh asparagus from Thailand increased to 14,268 t (Thai Customs Department, 2006). Thrips are one of the major pests of economically important plants in Thailand. The species considered to be the most destructive on asparagus in Thailand is Thrips tabaci (Bansiddhi and Poonchaisri, 1991; Chontanaswat and Jesadadhamsatit, 2006). Exported agricultural products must be completely free from quarantine pests. In Thailand, fresh asparagus is exported to Japan and the USA, for both of which the majority of shipments are fumigated with methyl bromide (Davis and Venette, 2004). The “Montreal Protocol on Substances that Deplete the Ozone Layer” passed by the United Nations in 1992 requires developed nations to reduce most uses of methyl bromide by 2005 and eliminate most uses by 2015 (Fields and White, 2002). Alternative methods for disinfestation of asparagus against thrips (Thrips tabaci) need to be developed for the Thai export trade, ensuring efficient thrips’ mortality, while maintaining quality and environmental safety. Heat treatment (Lurie, 1998) and controlled atmospheres using carbon dioxide have been used as alternatives to chemical treatment against insect pests (Hallman, 1994). The use of heat treatment is limited by its effect on fresh produce quality. The purpose of this study is to examine the effects of heat and high CO 2 treatments on quality of asparagus as part of the assessment of these treatments as potential disinfestations methods. In this context a better understanding of the primary forms of stress and damage caused by heat would be valuable. Proc. III rd IC Postharvest Unlimited 2008 Ed: W.B. Herppich Acta Hort. 858, ISHS 2010