Submitted to: Florida Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/1/2006
Publication Date: 8/1/2006
Citation: Mclean, S.C., Bloem, K.A., Bloem, S., Hight, S.D., Carpenter, J.E. 2006. Effect of temperature and length of exposure time on percent egg hatch of Cactoblastis cactorum (Lepidoptera: Pyralidae). Florida Entomologist. 89(3):340-347. Interpretive Summary: A cactus moth native to South America was found in North America for the first time in 1989. The insect’s spread from the Florida Keys along the coast of southeastern United States to Alabama and South Carolina has raised concerns about this moth’s unavoidable and unwanted impact on native, agricultural, and ornamental cactus in its new homeland. The bright orange-red, black-spotted caterpillars are eating all species of prickly pear cacti with flat pads. Scientists with USDA Center for Medical, Agricultural and Veterinary Entomology in Tallahassee, FL and Crop Protection and Management Research Unit in Tifton, GA are looking into ways of controlling this insect in urban and agricultural settings. Experiments were conducted in growth chambers with eggs of this moth to identify the temperatures under which the eggs could survive. Cactus moth eggs failed to hatch when held at constant temperatures under 15°C and over 35°C. Also, eggs did not hatch if exposed to -10°C for only one day or -5°C for four days. This information will be combined with ongoing experiments to determine the areas of North America conducive to the survival of the South American cactus moth.
Technical Abstract: The oligophagous cactus moth, Cactoblastis cactorum (Berg), has been recognized as a serious and immediate threat to Opuntia cacti in Florida and the southeastern United States. The moth has successfully colonized new geographical ranges with lower annual temperatures north of the Florida Keys where it was first detected in the continental United States in 1989. This study evaluated the effect of temperature on egg development and egg hatch of C. cactorum by utilizing various treatment temperatures, exposure times, and egg ages. The temperatures used in this study ranged from a low of -20°C to a high of 50°C, thus encompassing the potential range of temperatures that eggsticks may be exposed to in potential new host areas. One-day-old eggs held at a constant temperature of 30°C resulted in the highest percent hatch and shortest time to egg hatch. Eggs did not hatch when held at constant temperatures '15°C or '35°C. Furthermore, one day of exposure at -10°C and 4 days of exposure at -5°C were 100% lethal to one-day-old eggs. Eggs that were seven- and 14-days-old before exposure to cold temperatures were generally more resistant to temperature effects than one-day-old eggs.