The cactus moth, Cactoblastis cactorum (Berg) (Lepidoptera: Pyralidae), was reported in Florida in 1989, and it is expanding its geographical range to threaten Opuntia cactus (Cactaceae) in the southwestern United States, into Mexico, where it is an important economic crop. Laboratory life history studies were conducted at 18, 22, 26, 30, and 34°C to understand cactus moth biology and to develop strategies for control. Duration of immature stages was generally longest at 18°C, declining significantly at 22°C, and shortest at 26, 30, and 34°C. Total immature developmental time from eggs to pupae was ≈180 d at 18°C, 116 at 22°C, and ranged from 65 to 72 d at 26–34°C. Developmental rate for egg-to-pupal stages was estimated using the logistic equation, rate = 0.0165/(1 (T/20.7093)−5.8823). Percentage survival of immatures was usually lowest at the temperature extremes tested (18 and 34°C), but they did not differ between the sexes. Estimated lower developmental threshold temperature was 13.3°C, resulting in estimated degree-days for development from ≈845 at 18°C to 1,387 at 34°C. In general, pupal weights declined with increasing temperature, and they were always lower in males than in females. Female adult survivorship was longest at 18°C, and shortest at 34°C, with the other treatments clustered between the temperature extremes. The highest reproductive values were found at 30°C, which indicates an approximate optimal temperature. Net reproductive rate (R0), gross reproductive rate (GRR), generation time (T), intrinsic rate of increase (r), finite rate of increase (λ), and doubling time (DT) were 43.68 ♀/♀, 44.02 ♀/♀, 67.14 d, 0.0562 ♀/♀/d, 1.058 ♀/♀/d, and 12.33 d, respectively. An oviposition rate surface describing mean oviposition rate as a function of time and temperature was, eggs = (−11.241 0.854T) d exp (−0.020Td). Given the life history characteristics found in this study and other studies, cost-effective pest management strategies against C. cactorum are discussed.
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Vol. 100 • No. 4