Evaluating Herbicides for Postemergence Control of Common Weeds in Container Nursery Crops
HaoSheng Lin, MHS Seminar
Under the direction of Dr. Joe Neal
Monday, August 17, 2020, at 8:00 am
Join Zoom Meeting: https://ncsu.zoom.us/j/96280114247?pwd=ZDFuL0tCcjhRYjFoWXZmLzdBb1NrQT09
Meeting ID:  962 8011 4247
One tap mobile:
+13017158592,,96280114247#,,0#,,384200# US (Germantown)
+13126266799,,96280114247#,,0#,,384200# US (Chicago)

Abstract

To control weeds, producers of container nursery crops apply preemergence herbicides 3 to 6 times a year.  Despite the availability of numerous herbicides, weeds continue to emerge and must be removed by hand, a laborious and expensive production practice.  In other cropping systems, emerged weeds are controlled with postemergence herbicides.  Yet little information is available on the efficacy of postemergence herbicides on common weeds of container nursery crops.  Therefore, experiments were conducted in 2018 and 2019 in North Carolina to evaluate herbicides for postemergence control of common cool-season and warm-season annual weeds in container nursery production. The cool-season study was conducted at NCSU’s Horticulture Field Lab (HFL), Raleigh, NC. Summer studies were conducted at HFL and the Horticultural Crops Research Station in Castle Hayne, NC. Weed species for the winter study were common groundsel, common chickweed, and flexuous bittercress. For the summer studies, chamberbitter, eclipta, livid amaranth, rice flatsedge, spotted spurge, and yellow woodsorrel were included. All weeds were surface seeded twice, two weeks apart, to evaluate the effects of growth stage on herbicide efficacy. Treatments included diquat, flumioxazin, flumioxazin + pyroxasulfone, halosulfuron-methyl, indaziflam, isoxaben bentazon, sulfentrazone, cloransulam-methyl, glufosinate, oxyfluorfen, saflufenacil, and topramezone. Percent weed control was visually evaluated weekly and aboveground fresh weights were measured at 4 or 7 weeks after treatments for summer and winter studies, respectively. In the winter study, diquat, flumioxazin, and flumioxazin + pyroxasulfone provided ≥ 80% control of common groundsel, common chickweed, flexuous bittercress, for both growth stages. In summer studies, flumioxazin provided ≥ 80% control of chamberbitter, eclipta, livid amaranth, rice flatsedge, and yellow woodsorrel. Glufosinate provided ≥ 80% control of chamberbitter, eclipta, and spotted spurge. Other herbicides each controlled at least some seedling weed species, but were generally less effective overall.  These results illustrate that effective postemergence control of common weeds may be possible in certain contain grown nursery crops but application methods or specialized application equipment to avoid contact with the crop canopy will be required.