Because infestation by cabbage maggot, Delia radicum (L.), does not peak immediately after planting seeds, experiments in 2014 and 2015 determined the effect of timing insecticide application for control on direct-seeded turnip, Brassica rapa var. rapa (L.). Treatments were one chlorpyrifos application either at planting or 2 weeks after planting. Twenty turnip roots were sampled three times starting 2 weeks after the second application. Roots were evaluated for the number of roots infested with cabbage maggots and severity of damage on a scale of 0 = no injury, through 9 = no root hairs or >90% root destroyed. In both years, incidence of cabbage maggot was significantly less in turnip roots treated with insecticide 2 weeks after planting than at planting. Implications of these results for management of cabbage maggot on the Central Coast of California are discussed.