HORTICULTURAL ENTOMOLOGY Evaluation of Insecticides and Application Methods Against Contarinia nasturtii (Diptera: Cecidomyiidae), a New Invasive Insect Pest in the United States

The midge Contarinia nasturtii (Keiffer), a serious gall-forming insect pest of cruciferous plants in Europe and southwestern Asia, was Þrst reported in the United States in summer 2004. It had not been recorded in North America until its discovery in Ontario, Canada, in 2000. EfÞcacy of 20 insecticides belonging to 12 different classes was evaluated by using a foliar spray, soil drench, or seed treatment method. The broccoli cultivar ÔPackmanÕ was used in all tests at the suitable stage of four to Þve true leaves. Results indicated that foliar sprays of -cyhalothrin, acephate, acetamiprid, chlorpyrifos, and methomyl reduced C. nasturtii larval populations by 96.7Ð100%. Except for acetamiprid, theother four insecticides alsowereeffective against adults andprovided100%mortality after 24 h. When applied by drench, acetamiprid, imidacloprid, and thiamethoxam provided 100% control ofC. nasturtii larvae, and the duration of efÞcacy lasted at least 7 wk.When applied as seed treatment, clothianidin and thiamethoxam provided 100% control of larvae and did not signiÞcantly affect seed germination. Imidacloprid also provided 100% control but the percentage of germination after treatment was only 62% (96.9% in check). These results indicate that several insecticides may signiÞcantly reducemidge populations. The nicotinoid class of insecticides, which has strong systemic activity, is likely to be the Þrst choice. It is necessary to explore and develop other control methods such as cultural control and host resistance to develop an effective integrated pest management system.