Submitted to: Biocontrol Science and Technology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/13/2009
Publication Date: 5/1/2009
Citation: Tate, C.D., Hight, S.D., Carpenter, J.E. 2009. Oviposition preference of Cactoblastis cactorum (Lepidoptera:Pyralidae)in caged choice experiments and the influence of risk assessment of F1 sterility. Biocontrol Science and Technology. 19,S1:317-333. Interpretive Summary: The Argentine cactus moth was found in North America in 1989. Caterpillars of this moth are orange-red with black spots and feed inside the pads of prickly pear cactus. Continued spread of this non-native insect has raised concerns about this moth’s unavoidable and unwanted impact on native, agricultural, and ornamental cactus in its new homeland. 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 to monitor and control this insect. We conducted tests in cages with different species of cactus to determine if female moths preferred to lay her eggs on some cactus species more than others. A variety of comparisons were made based on factors such as the amount of spins on a plant and short versus tall plants. In general, we found that tall prickly pear cactus species were preferred over short species, either spiny or less spiny, but that tall spiny species were preferred over tall not spiny species. This information helps scientists, control experts, and landowners manage the invasive cactus moth and predict which cactus species may be at greatest risk of attack by this insect.
Technical Abstract: Releases of lepidopteran biological control agents have successfully controlled invasive weed species. However, issues with non-target effects of released exotic agents have resulted in stringent pre-release host specificity testing. Use of inherited (F1) sterility, a radiation induced genetic condition that can cause sterility in the F1 generation, could further assess the risk of non-target effects and negative ecological effects under field conditions. This technique may aid in approving potentially effective and safe biological control agents for release. The unintentional arrival of the cactus moth, Cactoblastis cactorum, into the United States provides a unique opportunity to evaluate the potential of F1 sterility. This study was conducted to assess host oviposition preferences of C. cactorum females mated with irradiated and non-irradiated males for cactus species from seven groups based on location, cactus growth characteristics (plant structure), spine densities, genera, and economic importance. No significant differences in female host preference were observed between females mated with normal or irradiated males. Lack of significant differences in oviposition preference suggests that inherited (F1) sterility has potential as a risk assessment tool for potential exotic biological control agents for invasive weed species. Evaluation of the overall analysis of female C. cactorum host preference revealed that significantly different numbers of eggsticks were oviposited on cactus species. In whole plant cages significantly more eggsticks were oviposited on Opuntia corallicola than any other species, and in cladode cages significantly more eggsticks were oviposited on Opuntia humifusa than all other species except Opuntia pusilla.