Submitted to: Florida Entomologist
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/15/2011
Publication Date: 3/22/2011
Citation: Paraiso, O., Hight, S.D., Kairo, M., Bloem, S. 2011. Egg parasitoids attacking Cactoblastis Cactorum (Lepidoptera:Pyralidae) in north Florida. Florida Entomologist. 94(1):81-90. Interpretive Summary: A moth from northern Argentina was found in North America for the first time in 1989. This moth causes damage only to prickly pear cactus. The insect’s spread from the Florida Keys along the Gulf Coast to Louisiana and the Atlantic Coast to 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 feed inside the pads of all prickly pear cactus with flat pads. Scientists with USDA-ARS Center for Medical, Agricultural and Veterinary Entomology in Tallahassee, FL, Florida A&M University, and USDA Animal and Plant Health Inspection Service are looking into ways to control this insect. Eggs of this moth were checked for attack by natural enemies at sites in northern Florida. The female moth lays her eggs one on top of the other and forms a chain that resembles a spine. This egg mass is called an eggstick. A total of 1,527 eggsticks (91,013 eggs) were monitored on cactus plants. Only one type of tiny wasp was found parasitizing eggs of the cactus moth. Attack of eggs by these wasps was at low levels – only 10 eggsticks (0.6%) were found with parasitized eggs. These wasps have been used in other programs to help control moth pests by mass rearing the wasps and releasing them at locations and times when the moth is a problem. Even though the attack rate of this wasp was low against naturally occurring cactus moth, information in this study helps scientists working to develop control efforts against this invasive pest.
Technical Abstract: Interest in the natural enemies of Cactoblastis cactorum (Berg) has increased since the moth was found in Florida in 1989. The way by which the moth first arrived in Florida is still uncertain. Previous surveys for natural enemies in Argentina identified egg parasitoids in the family Trichogrammatidae as potentially important control factors of C. cactorum. A study was conducted in north Florida to identify and to assess occurrence of egg parasitoids attacking this invasive moth in its new homeland. Surveys undertaken at six locations in north Florida from July 2008 to December 2009 revealed that eggsticks of C. cactorum were attacked by egg parasitoids from the Trichogramma genus: T. pretiosum Riley, T. fuentesi Torre, and an additional unidentified Trichogramma species belonging to the T. pretiosum group. In order to assess the importance of these egg parasitoids, the fate of individual C. cactorum eggsticks was determined during weekly visits to each site. This assessment showed that the combined level of parasitism of C. cactorum eggsticks was very low with less than 0.2% of host eggs attacked at any one of the six sites. While parasitoids attacked smaller eggsticks, there was no correlation between the number of eggs in an eggstick attacked with increasing number of eggs/eggstick. Comparing the mean number of eggs/eggstick, there was no difference between the three flight periods of C. cactorum, but there was a difference between the six sites. Based on these results, the use of Trichogramma wasps as an inundative biological control agent, complementary to the Sterile Insect Technique application, is discussed.