Oviposition preference of Cactoblastis cactorum (Lepidoptera: Pyralidae) in caged choice experiments and the influence on risk assessment of F1 sterility

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.