Insecticide and Fungicide Combinations to Optimize Control of Onion Maggot (Delia antiqua) and Onion Smut (Urocystis cepulae) in Ontario

ABSTRACT Changes in pesticide availability require that new compounds be tested for their efficacy in control of pests and pathogens on important vegetable crops. A study was conducted to determine the effectiveness of combinations of the insecticides LORSBAN® 15G (chlorpyrifos), GOVERNOR® 75WP (cyromazine), AZTEC® 2/0.1G (phosetbupirin + cyfluthrin) and REGENT® 80WG (fipronil), and the fungicides PRO-GRO® 30/50D (carbathiin + thiram), DITHANE DG® 75G (mancozeb), and PRO-GRO + DITHANE DG for control of onion maggot (Delia antiqua) and onion smut (Urocystis cepulae) in onions grown on muck soils in Ontario. Seed and granular in-furrow treatments were tested. Insecticide and fungicide efficacy varied depending on the pesticide combination. Effective control of both onion maggot (91–98%) and onion smut (57–100%) was achieved with insecticide treatments in combination with PRO-GRO + DITHANE DG. GOVERNOR and REGENT seed treatments provided the best onion maggot control. The best onion smut control was achieved with PRO-GRO seed treatment + granular in-furrow applications of DITHANE DG and LORSBAN. The results suggested that LORSBAN has fungistatic properties.