|Legaspi, Jesusa - Susie|
Submitted to: Annals of the Entomological Society of America
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/8/2007
Publication Date: 6/24/2007
Citation: Legaspi, J.C., Legaspi,Jr, B.C. 2007. Life table analysis for Cactoblastis cactorum immatures and female adults under five constant temperatures:Implications for pest management. Annals of the Entomological Society of America. 100(4):497-505. Interpretive Summary: The cactus moth, Cactoblastis cactorum, is an invasive insect pest that was first reported in Florida in 1989 and has been moving westward in the southeastern United States towards Texas and Mexico where it threatens to cause serious economic losses. Scientists at the Center for Medical, Agricultural, and Veterinary Entomology, Gainesville FL. and the state of Florida, studied the moths development in the laboratory under different constant temperatures to develop strategies for its control. We tested five different temperatures. In general, development was longest at the coldest temperatures but survival was higher at the lowest temperature. Weights and egg production was highest at high temperatures. The moth did not display particularly high reproduction, so its pest status is due largely to the protection from control agents once it has entered the cactus plant. The most vulnerable lifestage appears to be the egg stage, both because it is exposed, and also because of the relatively long duration time. Native ant populations may be encouraged to feed on the cactus moth eggs. Specialized natural enemies that seek and attack larvae inside the cactus plant and that are active at the examined temperature will be sought out.
Technical Abstract: The cactus moth, Cactoblastis cactorum (Berg) (Lepidoptera: Pyralidae) was reported in Florida in 1989, and is expanding its geographical range in the United States to threaten Opuntia cactus in the southwestern states and Mexico where it is an important economic crop. Laboratory life history studies were conducted at 18, 22, 26, 30 and 34 ºC to understand its biology and develop strategies for control. Duration of immature stages was generally longest at 18, declining at 22 and shortest at 26, 30 and 34 ºC. Total immature development time from eggs to pupae was about 180 days at 18, 116 at 22 and ranged from 65 to 72 days at 26 to 34 ºC. Development rate for egg to pupal stages was estimated using the logisitic 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 ºC), but did not differ between the sexes. Estimated lower developmental threshold temperature was 13.3 ºC, resulting in estimated degree days for development from about 845 at 18 ºC to 1387 at 34 ºC. In general, pupal weights declined with increasing temperature, and were always lower in males than in females. Female adult survivorship was longest at 18 ºC, and shortest at 34 ºC, with the other treatments clustered between the temperature extremes. The highest reproductive values were found at 30 ºC, 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 ('), 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 others, cost-effective pest management strategies against C. cactorum are discussed.