Control of Northern Willowherb in Nursery Containers

Abstract

Abstract Four experiments were conducted to determine the effectiveness of granular and sprayed preemergence herbicides for controlling northern willowherb (Epilobium ciliatum Rafin) in container crops. Eleven granular herbicides representing various combination of pendimethalin, prodiamine, oryzalin, oxyfluorfen, oxadiazon, napropamide, isoxaben, trifluralin, and flumioxazin were evaluated, as well as sprayed Surflan AS (oryzalin), Devrinol 50-DF (napropamide), Barricade 4FL (prodiamine), and Gallery 75DF (isoxaben). Herbicides were applied to recently filled containers and irrigated with overhead sprinklers. Weed numbers were counted in each pot and weed shoot dry weight was measured at the conclusion of each study. Ronstar G (oxadiazon) at 4.48 kg ai/ha (4 lb ai/A) consistently provided the most effective control among all herbicides. Other granular herbicides containing oxadiazon were also effective. Surflan and Devrinol did not consistently reduce weed numbers as effectively as Ronstar G, however they did reduce subsequent growth of northern willowherb seedlings that were able to successfully establish. Gallery did not provide any control alone nor did it improve control when tank mixed with other products.