Submitted to: Florida Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/9/2007
Publication Date: 6/1/2007
Citation: Sivinski, J.M., Holler, T., Pereira, R., Romero, M.I. 2007. The thermal environment of immature caribbean fruit flies, Anastrepha suspensa (Diptera: Tephritidae). Florida Entomologist. 90:347-357. Interpretive Summary: Tephritid fruit flies attack scores of fruits and vegetables, and are the cause of trade barriers wherever they occur. In order to predict where they might spread and to develop genetic controls that take advantage of Temperature-Sensitive genes it is important to know what temperatures immature flies confront in fruit and in the soil. Scientists at the USDA-ARS Center for Medical, Agricultural and Veterinary Entomology in Gainesville, Florida used computerized measuring devices in the field to determine fruit temperatures in and under various parts of different host tree canopies. They found considerable variability in temperatures, some of which was related to fruit size and location. This information will be provided to collaborating geneticists who will use it to guide the development of lethal-strains for mass-release.
Technical Abstract: Since many plants regulate their internal temperatures there is no a priori reason to believe that air temperature accurately reflects the temperatures faced by tephritid larvae inhabiting the interiors of fruits. Larvae also move across and burrow into soil to pupate, and immature flies at this point in their development are also likely to encounter temperatures that might be less than or exceed air temperature. Using thermocouples and a computerized data logger we measured a substantial range of temperatures in the four major hosts of Anastrepha suspensa (Loew), the Caribbean fruit fly, (Surinam cherry, Eugenia uniflora L., Cattley guava, Psidium cattleianum Sabine, common guava, Psidium guajava L., and loquat, Eriobotrya japonica (Thunb.)), and in grapefruit, Citrus paradisi Macf., an economically important secondary host. In general, temperatures were higher in the southwestern portions of tree canopies relative to those in the northeastern interiors. Fruit on the ground was warmer than that in the tree, but there was no significant pattern of maximum fruit core temperatures being warmer than subcutaneous pulp. Soil temperatures were also higher than fruit-in-tree temperatures, and decreased and displayed less variance with increasing depth. Fruit in trees seldom reached temperatures +/ - 0.05 of adjacent air temperatures, but fruit on the ground could be more than 0.25 the adjacent air temperature. There were positive relationships between the ratio of mean and minimum fruit temperature/adjacent air temperature and fruit diameter. Information on the temperatures confronted by fruit fly eggs, larvae and pupae can be used to model population growth and distribution, and to design temperature sensitive strains through conditional gene expression for mass-rearing and release.