|Legaspi, Jesusa - Susie|
Submitted to: Journal of Entomological Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/15/2009
Publication Date: 11/3/2009
Citation: Legaspi, J.C., Baez, I., Legaspi,Jr, B.C. 2009. Phenology and egg production of the cactus moth, Cactoblastis cactorum(Lepidoptera: Pyralidae): comparison of field census data and life stage development in the field. Journal of Entomological Science. 44(4): 341-352. Interpretive Summary: The invasive cactus moth threatens native and commercial cacti in the USA and Mexico, but may be stopped from spreading out of the southeastern states by a creating control -barrier along the gulf coast. In order to best time the various control techniques, scientists at the USDA-ARS Center for Medical, Agricultural and Veterinary Entomology in Gainesville, Florida surveyed Florida cactus plants and set up traps to discover when eggs, larvae and adults were most abundant. They found there were three generations per year with different developmental rates. Such information will be used to organize Sterile Insect Releases, biological control releases and the removal of infested cacti.
Technical Abstract: Natural phenology and development of the cactus moth, Cactoblastis cactorum (Berg) (Lepidoptera: Pyralidae) was studied under field conditions in St. Marks National Wildlife Refuge, St. Marks, FL. from July 2006 to September 2007. Cactus pads (Opuntia stricta Haw. [Cactaceae]) were visually surveyed weekly for presence of moth immature stages. Adult male C. cactorum populations were surveyed using a pheromone lure and wing style sticky traps. The field census data indicate three generations per year. The generations may be broadly generalized as occurring in approximately August to September, October to April, and May to July. Numbers of eggsticks peaked in mid August, mid October and mid-April. High numbers of early larval immatures (1st to 3rd instars) were recorded in October 2006, May 2007 and Sept. 2007. High numbers of late larval immatures (4th to 5th instar) were recorded in September to October 2006, December to January 2006, June to July 2007. Peak numbers of Cactoblastis male adults were approximately in mid-October 2006, April to May 2007 and July to August 2007. Pupae were cryptic and difficult to sample. Development in field cages was studied by introducing cohorts of moth eggs on potted cactus plants (Opuntia ficus-indica (L.) Mill.) into the field at approximately the same times they were found to occur naturally. During the course of each generation, potted plants were returned to the laboratory for determination of moth lifestage. Body weights and lengths were also recorded. The field cage experiment also produced the three generations found by sampling native cactus. However, the generations were more clearly defined because eggs were introduced as cohorts and most insects were recovered. Measurements of larval head capsules and body lengths show that development in the Winter generation is slower than that of the Summer and Fall generations, although peak measurements are approximately identical in all three generations. Female pupae weighed 225.25 mg which was significantly heavier than males weighing 138.01 mg. Pupal weights differed according to generation, but this was not found in adults. Female adults weighed 130.3 mg, compared to males, which weighed 60.81 mg. Adult sex ratio was approximately 1:1. Male adults appear to have emerged earlier than females in the Fall generation.