This research investigated use of the sterile insect technique (SIT) to control American serpentine leafminer, Liriomyza trifolii (Burgess), an important insect pest of chrysanthemums and gerberas in Canadian ornamental greenhouses. Emergence and flight ability of treated L. trifolii were not compromised by X-ray exposure from a linear particle accelerator. Females treated with 150Gy and 170Gy were completely sterile, while residual male fertility was observed. Three sieves were designed to remove females prior to irradiation and improve SIT efficacy. Sieve pore dimensions of 1.543mm by 0.688mm excluded 76% of female pupae and doubled the male-to-female ratio. Knowledge of the endemic population density determines sterile insect release rates. The regression equation y = (√YSC - 1.36) / 0.0074 (R2 = 0.73) was found to provide an estimate of current L. trifolii populations. Results from this research regarding dose rate, mechanical sexing, and estimation of L. trifolii population density will aid in developing a commercial SIT program.