Application of the F1 Sterile Insect Technique (F1-SIT) for field host range testing of the Tortricid Episimus utilis, a candidate for classical biological control of Brazilian peppertree in Florida

Full text: Brazilian peppertree, Schinus terebinthifolius Raddi (Anacardiaceae), is a dioecious evergreen shrub-like tree native to Brazil, Paraguay, and Argentina, that was introduced to Florida in 1898 as an ornamental. Currently, Brazilian peppertree is distributed widely throughout central and southern Florida, and is listed by the Florida Exotic Pest Plant Council as a 'Category 1' invasive exotic species because it is altering native plant communities. It also has exhibited invasive behaviour in California and Hawaii, as well as subtropical regions of at least 20 different countries. In 1994, several natural enemies of Brazilian peppertree were imported into a quarantine facility in Florida as candidates for classical biological control. One of the candidates was a South American leaf-rolling moth, Episimus utilis Zimmerman (Lepidoptera: Tortricidae). Larvae of E. utilis feed by scraping the surface of the Brazilian peppertree leaflets. As they mature, the developing larvae are capable of completely defoliating the plant. Host specificity tests are used to determine whether or not a potential biocontrol candidate is safe to release in the field. Some biologists believe that these tests often overestimate host range, which leads to the rejection of acceptable candidates. As cage testing under quarantine conditions may inhibit normal behaviour, open-field studies can provide a more realistic setting where insects can display an array of behaviours. However, open-field studies pose environmental risks in the area of introduction and are prohibited. Through the application of the F1 Sterile Insect Technique (F1-SIT), lepidopteran insects could be safely released temporarily for field host range testing. Advantages of F1-SIT include manifestation of sterility in the larvae of irradiated adults, exposure of the insect to the actual environmental conditions it will experience if approved for release, prediction of true field host range in the area of introduction, and the ability to suspend releases of irradiated insects if non-target species were being attacked with no risk of permanent establishment of E. utilis. The objective of the initial phase of this study was to evaluate the effect of gamma radiation on adult moth sterility. Data on the radiation biology of E. utilis adults conducted at various doses is presented, including results of fecundity, fertility, and percent sterility. (author)