Cold and Heat Treatment Technologies for Post-harvest Control of Fruit Flies in Africa

Abstract

Research on cold treatments for post-harvest control of tephritid fruit flies began in South Africa more than 100 years ago. Once commercial cold treatments were accepted by the USA for deciduous fruit exported from Africa, research turned to evaluating the same treatments on citrus. Experiments in shipments to New Zealand gave promising results in the late 1940s and a treatment of <0 °C for 12 days was accepted for exports of some types of citrus from Africa to Japan in 1970. In 1956 and again in 2001, it was shown that the Natal fruit fly, Ceratitis rosa, was as susceptible as the targeted medfly, Ceratitis capitata, to cold treatments. After the arrival in Africa of the oriental fruit fly, Bactrocera dorsalis, further cold treatment research showed that this species was similar in its cold tolerance to C. capitata and commercial cold treatments were developed for both citrus and avocado. Post-harvest heat treatments for tephritids in tropical fruit did not receive much attention before the arrival of B. dorsalis. Hot water immersion is the only heat treatment that has been evaluated and shown to be effective against B. dorsalis, C. capitata and the mango fruit fly, Ceratitis cosyra, in mango. These results confirmed previous studies from other countries and so this relatively simple treatment may permit widespread exports of mango from Africa in the future.