Weekly applications of methomyl at 0.45 and 0.9 lb AI/acre on fresh market tomatoes resulted in significantly more (total) mines by Liriomyza sativae Blanchard in the methomyl-treated plots (26,041 and 22,570, respectively) than in the untreated check (13,897 mines). These differences were due at least in part to methomyl’s adverse effect on parasites normally attacking L. sativae and to its inability to control this leafminer. Nine species of parasites in 2 families were reared from L. sativae. Of these, Diglyphus begini (Ashmead) was far the most common, comprising 80.7% of the total number reared.