Vapor heat treatment for quarantine control of the oriental fruit fly (Diptera: Tephritidae) in papaya fruit from Thailand

A two-stage vapor heat treatment (VHT) is used commercially for disinfestation of the oriental fruit fly, Bactrocera dorsalis (Hendel) (Diptera: Tephritidae) in various tropical fruits exported from Thailand to international markets. In the present study, VHT was tested against B. dorsalis in papayas to confirm a high level of quarantine security. The first instar larva of B. dorsalis was the most heat tolerant life stage. The VHT consists of heating papaya fruits with hot air at 50–80 % RH from ambient temperature to a fruit center temperature of 43 °C (dry pre-heating period), then heating with saturated hot air to 47 °C (wet heating period) with a 20-min hold at 47°. In large-scale confirmatory tests of this VHT treatment schedule, none of the treated 78,405 first instar larvae survived. Papayas at the color break maturity stage treated by VHT and held under simulated commercial export conditions showed no differences in fruit quality compared with non-treated controls. VHT showed high efficacy in disinfestation of papayas of B. dorsalis while maintaining fruit quality and could be used as a standard quarantine treatment for papaya exported from Thailand.