Evaluation of selected preemergence herbicides in field-grown landscape crops in Kentucky

Abstract Research was conducted during 1990 and 1991 at the Horticultural Research Farm in Lexington, Kentucky, to evaluate the efficacy of herbicides available for use on woody landscape plants (simazine and oryzalin), newly labelled herbicides (isoxaben, isoxaben plus oryzalin, metolachlor and metolachlor plus simazine) and those not widely labelled for the nursery industry (oxyfluorfen and dithiopyr). Herbicide phytotoxicity was also evaluated in 10 species of woody nursery crops. Results 6 WAT (weeks after treatment) indicated that the standard of simazine at 1.1 kg ai/ha (1.0 lb/A) plus oryzalin at 3.3 kg ai/ha (3.0 lb/A) provided adequate control of most common broadleaf weeds (98%) and annual grasses (98%) but not yellow nutsedge (31%). Isoxaben plus oryzalin at 4.2 kg ai/ha (4.0 lb/A) (DF formulation) and isoxaben plus trifluralin at 4.2 kg ai/ha (4.0 lb/A) (granular formulation) gave excellent full-season control of nearly all broadleaf and grass weeds with the exception of galinsoga and field bi...