The prevention of herbicide injury to hazelnut trunks

European hazelnut grows as a multi-stemmed bush but is trained to a single-trunk tree in Oregon orchards to facilitate maintenance and harvest.
Control of basal sprouts is necessary to maintain the single-trunk form, typically accomplished with 4 to 8 applications of herbicides per year.
Frequent and widespread reports of trunk injury in Oregon orchards pose questions concerning the safety of the practice, particularly in juvenile trees.
Trunk guards and latex paint are commonly used as physical barriers to shield the trunk from direct contact with herbicides but no studies have been conducted to assess efficacy of either method in protecting the trunk.
To address this question, ‘Jefferson’ hazelnut trees were planted in 2018 with three trunk protection methods: unshielded, coated with latex paint, or covered in an opaque plastic trunk guard.
These trees were treated with glufosinate at 1,150, 2,300, and 4,600 g ai ha^‑1 in 2019 and 2020 with one, two, or three applications per season.
Assessments of external trunk injury were made over two years and measurements on trunk density and internal trunk injury were made when the trees were cut in summer 2021. Results showed injury was primarily induced at the 4,600 g ai ha^‑1 on unshielded and painted trunks, with no injury to trunk guard trees.
Compared to unshielded trunks, latex paint reduced trunk injured area by 53%. Trunk cross sectional area increased in painted and trunk guard trees and density was reduced in trunk guard trees.
Both latex paint and trunk guards provide protection from herbicide injury.

X International Congress on Hazelnut

R.J. Hill, D.R. King, M.L. Moretti

Corylus avellana, sucker control, latex paint, trunk guard, basal sprout

https://doi.org/10.17660/ActaHortic.2023.1379.72