TULIP (TULIPA SPP), DAFFODIL (NARCISSUS SPP), AND IRIS (IRIS SPP) RESPONSE TO PREEMERGENCE HERBICIDES

Broadleaf weed control and tulip, daffodil, and iris response to alach lor, dithopyr, diuron, isoxaben, napropamide, oryzalin, oxadiazon, oxy fluorfen, pendimethalin, pronamide, and thiazopyr applied preemergence were evaluated. All herbicides controlled broadleaf weeds for five mo nths after application, but control with oxyfluorfen, pendimethalin, a lachlor, pronamide, and napropamide decreased six months after applica tion. The greatest weed control was with oxadiazon, isoxaben, thiazopy r, dithiopyr, and diuron, whereas the least weed control was with napr opamide and alachlor. In general, tulip was more sensitive to herbicid es than daffodil and iris. All herbicides injured tulips at early grow th stages but bulb yield of tulip was reduced only by oxadiazon, oxyfl uorfen at 0.28 kg ai/ha, pronamide, and dithiopyr. Tulip flower qualit y was reduced only by oxadiazon, oxyfluorfen at 0.28 lb/ha, and pronam ide. Daffodil and iris were tolerant to thiazopyr, isoxaben, pronamide , alachlor, oryzalin, napropamide, and diuron.