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22 August 2022 Hazelnut growth and weed control in response to selected preemergence herbicides
Rafael M. Pedroso, Marcelo L. Moretti
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Hazelnut hectarage is expanding in Oregon. Weed competition in young orchards can severely reduce the growth and survival of plants. New orchards replace crops, including grass seed fields, which often are infested with herbicide-resistant weeds, including Italian ryegrass. This research evaluated hazelnut tolerance to pronamide, pyroxasulfone, and S-metolachlor. Three multi-year field experiments were conducted at newly planted orchards in the Willamette Valley during 2019 and 2020. Treatments compared pyroxasulfone (0.24 kg ai ha–1), pronamide (2.3 kg ai ha–1), and S-metolachlor (1.39 kg ai ha–1) applied at the reference rate, and at 2× and 4× that rate, compared to weed-free check. Treatments were applied within 2 wk after the winter transplant and reapplied the following year. Hazelnuts showed a high tolerance to all herbicides tested, with negligible injury noted (<3%). No changes in leaf chlorophyll were noted, averaging 242, 179, and 225 mg m–2 on each study site. Tree growth was similar among treatments as measured by trunk cross-sectional area, canopy volume, and internode length. A separate study evaluated the control of Italian ryegrass. Pronamide and pyroxasulfone provide 100% control of Italian ryegrass, and weed dry weight was reduced by up to 79 % compared to the grower standard. This study documents that hazelnuts are tolerant to pronamide, pyroxasulfone, and S-metolachlor, and that these herbicides can improve weed management in young orchards.

Nomenclature: S-metolachlor; pendimethalin; pronamide; pyroxasulfone; Italian ryegrass; Lolium perenne ssp. multiflorum; hazelnut; Corylus avellana L.

© Oregon State University, 2022. This is a work of the US Government and is not subject to copyright protection within the United States. Published by Cambridge University Press on behalf of the Weed Science Society of America.
Rafael M. Pedroso and Marcelo L. Moretti "Hazelnut growth and weed control in response to selected preemergence herbicides," Weed Technology 36(4), 570-575, (22 August 2022).
Received: 22 April 2022; Accepted: 23 July 2022; Published: 22 August 2022
soil-active herbicides
tree nut
weed control
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