Study on vapor heat treatment to disinfest Oriental fruit fly in Chinese mango fruits for exporting to foreign countries

Key Words： vapor heat treatment (VHT), mango, Bactrocera dorsalis, disinfestation

Abstract：        The use of vapor heat treatment (VHT) to eradicate infestations of the Oriental fruit fly Bactrocera dorsalis(Hendel) from shipments of Chinese mango fruits (Mangifera indica L.) destined for export to foreign countries was investigated. There were three main areas of research: 1. A heat tolerance test of the eggs and different instar larvae of B. dorsalis in various Hainan mango varieties (cv. Jinhuang, Aiwen, Xiaya and Tainong 1). 2. A small and  large-scale trial of the effectiveness of VHT in eradicating fruit flies from fresh mango fruits. 3. A study of the effect of VHT on mango fruit quality. The results show that when the temperature of treatment chamber increased to 50℃ (by saturated hot air) and the temperature of the innermost fruit pulp was raised to 47℃ and thereafter maintained at 47℃ for 0, 5, 10, 15, 20 min respectively, the relative heat tolerance of eggs and larvae of B. dorsalis was, from most to least tolerant, 2nd then 3rd then 1st instar larvae, then eggs. The most heat tolerant developmental stage was 2nd instar larvae infesting “Jinhuang” mangoes (the largest of the Hainan mango varieties with an average weight of 856 g).  Exposure to a temperature of 47℃ for 20 min killed all eggs and larvae in all varieties of mangoes tested. The results of a small and large-scale trial of VHT to eliminate the 2nd instar larvae from fresh “Jinhuang” mango fruits indicated that VHT completely killed estimated larval populations of 14 000 and 35 000 larvae respectively, and can therefore provide greater than a Probit 9 level of quarantine security (100% mortality). Meanwhile，with the exception of vitamin C which was decreased slightly, the quality of fresh “Jinhuang” mango fruits, including color, reduced sugar content, sucrose, total sugar, total acidity，and soluble solids, was not significantly affected by VHT treatment (20 min at 47℃).