Directed Application of Goal (Oxyfluorfen) to Container Grown Euonymus, to Minimize Phytotoxicity and Leaching

Abstract

Abstract Goal 1.6E (Oxyfluorfen) was applied to rooted cuttings of Euonymus fortunei ‘Colorata’ planted in a U.C. Mix (peat:sand, 1:1 by vol), in 3.8 1 (#1) containers, either as a topical spray or mixed within the growth-medium to 2, 7 or 14 cm (0.8, 2.8, 5.6 in) depth. At comparable rates, phytotoxicity was much lower in layered treatments than when sprayed over-the-top. With an identical concentration of Goal in the growth medium, there was no difference in phytotoxicity between a shallow top layer, exposing all but the base of the root ball to treated soil, and planting the root ball into an entire container profile of treated soil. Incorporation slightly reduced the herbicidal activity—as assessed by oversown grass weeds—compared to surface application. The presence of herbicide in the effluent, collected under the containers, was determined 1 and 8 weeks after the application, by bioassay based on germinating bentgrass. In the first bioassay, no appreciable amount of Goal was detected from surface sprays up to 3 kg/ha (2.75 lb/A), nor from 2 and 7 cm (0.8, 2.8 in) layers containing up to 19 mg/kg (17 lb/A). In the second bioassay, no herbicide was detected from shallow layers containing up to 192 mg/kg (172 lb/A). Goal at 19 mg/kg incorporated 2 to 7 cm (0.8, 2.8 in) deep, at planting time, is suggested as an alternative to overall application on containers.