Dose and Concentration Responses of Common Nursery Weeds to Gallery, Surflan and Treflan

Abstract

Abstract Preemergence herbicides are applied as often as every eight to ten weeks in container nursery crop production in the southeastern United States. However, weeds often emerge before reapplication. Experiments were conducted to assess the minimum surface-applied doses and the in vitro concentrations of preemergence herbicides required to control susceptible weed species. Greenhouse and outdoor container experiments were conducted to determine surface-applied Treflan (trifluralin) doses required to control large crabgrass and perennial ryegrass. In the greenhouse, 0.8 to 1.1 kg ai/ha (0.7 to 1.0 lb ai/A) was necessary for 6 weeks control. Outdoors, 1.5 to 1.9 kg ai/ha (1.3 to 1.7 lb ai/A) was needed for control 3 weeks after treatment (WAT). However, 6 WAT, 2.6 to 3.4 kg ai/ha (2.3 to 3.0 lb ai/A) was required. Petri dish experiments were conducted to determine the aqueous concentrations of Gallery (isoxaben), Surflan (oryzalin), and Treflan required to control common nursery weeds including eclipta, hairy bittercress, large crabgrass and spotted spurge. The concentration required for 80% shoot inhibition (I80) ranged from 0.4 to 1.5 μg ai/mL for Gallery, 1.2 to 9.8 μg ai/mL for Surflan and 1.1 to 73.8 μg ai/mL for Treflan. The relative response of weeds to aqueous concentrations was consistent with reports from outdoor container efficacy trials.