Differential Varietal Tolerance of Peach(Prunus persica)Seedlings to Glyphosate

Abstract

The translocation and effects of glyphosate [N-(phosphonomethyl)glycine] were determined in greenhouse-grown peach [Prunus persica(L.) Batsch] seedlings obtained from different seed parents. Two lower branches of 10-week-old seedlings of Rutgers Red Leaf, Bailey, Kalamazoo, Siberian C, and Harrow Blood were sprayed with 0.9 to 18 mg of glyphosate per plant. Seedlings of Harrow Blood, Bailey, and Kalamazoo were more susceptible to injury than were those of Siberian C and Rutgers Red Leaf. Glyphosate at 6, 9, and 18 mg produced necrotic areas on the stems of the former seedlings and at the higher rates tree death resulted. The Siberian C and Rutgers Red Leaf seedlings showed only chlorosis and malformation of apical leaves although slight stem injury occurred 1 month after treatment. Measurements of plant weight, height, and stem diameter indicated that seedlings of Harrow Blood, Bailey, and Kalamazoo tolerated only 3 mg of glyphosate without growth reduction. This was one-half and one-third of the amount which seedlings of Siberian C and Rutgers Red Leaf tolerated, respectively. The concentration of glyphosate in the treated lower branches and the main stem of the seedlings was determined by thin-layer chromatography. The concentrations in the bark were generally similar among all seedlings. Differential tolerance, therefore, was not based on differences in overall glyphosate concentration in tissues but on protective or resistance mechanisms present only in seedlings of Siberian C and Rutgers Red Leaf.

Toxicity of Giyphosate to Peach Trees as Influenced by Application Timing

“…No difference in the severity of cambial injury was detected between the tree limb receiving 1 0 , 0 0 0 or 20,000 ppm leaf dip except in 1979 with wood greater than 1.9 cm. These results sup port reports that spot sprays of glyphosate applied to any green bark or foliage on peach trees could result in tree death (6 ).…”

“…In all species studied, giy phosate injury was greatest when applied to green tissue, while applications to tree bark older than one year (not green) seldom re sulted in any visible injury (2,5,7). Gly-phosate application to peach leaves can result in severe tree injury and death (6 ). Damage from giyphosate can occur in a localized area of the tree near the application site or can result in complete tree death.…”

Weed Control in Immature Pecan (Carya illinoensis) and Peach (Prunus persica) Plantings

“…Best tree growth, which is related to weed control duration, occurred with two single applications of glyphosate at higher rates or in combination with simazine. In greenhouse studies, glyphosate at 6, 9, and 18 mg per plant produced necrotic areas on the stems of 10-week-old peach seedlings when two lower branches were sprayed (9).…”

Forty Years with Glyphosate

“…Common first visible phytotoxicity effects of glyphosate include rapid (within 2-10 days upon application) chlorosis, usually followed by necrosis (Suwannamek & Parker, 1975;Putnam, 1976;Campbell et al, 1976;Fernandez & Bayer, 1977;Marriage & Khan, 1978;Segura et al, 1978;Abu-Irmaileh & Jordan, 1978), possibly accompanied with morphological leaf deformities (Marriage & Khan, 1978), root and rhizome damage (Suwannamek & Parker, 1975;Fernandez & Bayer, 1977). Glyphosate accumulation has been reported in the meristems (Haderlie et al, 1978).…”