The Thermal Environment of Immature Caribbean Fruit Flies, Anastrepha suspensa (Diptera: Tephritidae)

John Sivinski, Tim Holler, Rui Pereira, Maritza Romero

Abstract


Because many plants regulate their internal temperatures, there is no a priori reason to believe air temperature accurately reflects the temperatures faced by tephritid larvae inhabiting fruit interiors. Larvae also move across and burrow into soil to pupate, and immature flies at this point 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 range of temperatures in the 4 major hosts of Anastrepha suspensa (Loew), the Caribbean fruit fly: Surinam cherry, Eugenia uniflora L., Cattley guava, Psidium cattleianum Sabine, guava, Psidium guajava L., and loquat, Eriobotrya japonica (Thunb.), and in grapefruit, Citrus paradisi Macf., an economically important secondary host. Generally, temperatures were higher in the southwestern portions of tree canopies relative to those in the northeastern interiors. Fruit on the ground was warmer than 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 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 immature fruit flies can be used to model population dynamics, and to design temperature sensitive strains through conditional gene expression for mass-rearing and release.

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