Brazilian peppertree, Schinus terebinthifolius Raddi (Anacardiaceae), is one of the most widely distributed invasive weeds in central and south Florida. This natural area weed was targeted for classical biological control in the 1980s. A South American leaf-rolling moth Episimus utilis (Zimmerman) (Lepidoptera: Tortricidae) is one of several promising candidates for biological control of Brazilian peppertree. Host-specificity tests were conducted in a quarantine facility to assess potential risks to non-target plants. However, traditional starvation (no-choice) and multiple choice testing procedures used for demonstrating the safety of E. utilis produced ambiguous results. Therefore, the F1 Sterile Insect Technique (F1SIT) is a novel approach that could be used to safely release the insect for field host range testing. Advantages of F1SIT 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 doses of 0, 50, 100, 150, 200, 250, and 300 Gy is presented including results of fecundity, fertility, and percent sterility.