Injury on White Oak Seedlings from Herbicide Exposure Simulating Drift

Abstract

<jats:p>Herbicide drift to landscape and woodland trees is a particular concern in midwestern United States where the topography is relatively flat, large-scale agriculture relies on herbicides, and housing developments and woodlands are intermingled with agricultural fields. Recently, leaf abnormalities (called leaf tatters) have been reported on white oak (<jats:italic>Quercus alba</jats:italic> L.). We evaluated the effects of field corn herbicides on white oak at the swollen bud, leaf unfolding, and expanded leaf stages. Container-grown white oak seedlings were treated with 1%, 10%, and 25% standard field use rates of 2,4-D isooctyl ester, glyphosate, 2,4-D isooctyl ester + glyphosate, dicamba, acetochlor + atrazine, and metolachlor. Loss of interveinal tissues (leaf tatters) occurred after treatment with the chloroacetanilide herbicides, acetochlor (+ atrazine) and metolachlor, only when oaks were in the leaf unfolding stage. No other herbicide caused tatter-like symptoms. Dicamba and 2,4-D ester applied at the leaf unfolding stage caused leaf cupping, downward rolling of leaf margins, elongation of leaf tips, leaf strapping with parallel veination, and initial leaf cupping followed by death of the growing point. Glyphosate applied at either the leaf unfolding or expanded leaf stage caused leaf chlorosis and necrosis, leaf tip browning, and curling of leaves. Herbicide applications near white oak should be timed before leaf unfolding or after the expanded leaf stages.</jats:p>

Investigations of the sensitivity of ornamental, fruit, and nut plant species to driftable rates of 2,4-D and dicamba

“…Figure 3 shows a pin oak leaf that was treated with a 1/20 × rate of dicamba, which resulted in a higher ratio due to decreased leaf width compared with the nontreated control. Samtani et al (2008) described similar symptomology on white oak seedlings that were injured with dicamba. Dicamba at the 1/20 × and ½ × rates and dicamba plus glyphosate at the 1/20 × rate all resulted in higher ratios on pin oak leaves compared with nontreated leaves (Table 5).…”

“…In contrast, 2,4-D injury caused epinasty, chlorosis, and necrosis of terminal leaflets on young leaves ( Figure 1L). Al-Khatib et al (1992), Feucht (1988), , and Samtani et al (2008) reported similar symptoms in response to applications of dicamba or 2,4-D on other tree and grapevine species.…”

“…In addition to grapevines, tree species have demonstrated sensitivity to dicamba and 2,4-D. Samtani et al (2008) studied the effects of several herbicides, including dicamba and 2,4-D, on white oak (Quercus alba L.) seedlings. Following application, leaf cupping, downward leaf margin rolling, elongation of leaf tips, necrosis, chlorosis, and parallel venation was observed, and the authors suggested that herbicides containing dicamba or 2,4-D should be applied near white oaks before the leaf unfolding stage or after the leaf expansion stage to minimize injury to trees (Samtani et al 2008). Al-Khatib et al (1992) observed 5% to 52% visual injury as a result of 2,4-D treatments ranging from 1/100th to ⅓ the normal use rates on sweet cherry (Prunus avium L.) trees.…”

Comparative Leaf Phenology of White Oak and Northern Red Oak

“…Previous research found that loss of interveinal tissue (leaf tatters) is caused by exposure of white or northern red oak seedlings to low concentrations of chloroacetanilide herbicides, at the leaf unfolding stage [1,2]. Swollen bud and expanded leaf stages are not susceptible to chloroacetanilide herbicides.…”

“…Genetic or phenotypic variation of red and white oak have not been reported in the literature, but phenotypic variation occurs in other oak species. Previous studies observed variation in herbicide response within oak species [1,2]. Phenological differences among individual trees, and among populations of Valonia oak (Quercus ithaburensis Decne) in northern Israel, have been attributed to genetic variation [13].…”