Yield and Physiological Response of Nontransgenic Cotton to Simulated Glyphosate Drift¹

Abstract

Field studies were conducted in 2001 in Lewiston, NC, and in 2002 at Clayton and Lewiston, NC, to investigate the response of nontransgenic cotton to simulated glyphosate drift in a weed-free environment. Nontransgenic cotton variety ‘Fibermax 989’ was planted in a conventional seedbed at all locations. Glyphosate treatments were applied early postemergence (EPOST) at the four-leaf growth stage of cotton at 0, 8.7, 17.5, 35, 70, 140, 280, 560, and 1,120 g ai/ha and represent 0, 0.78, 1.55, 3.13, 6.25, 12.5, 25, 50, and 100% of the commercial use rate, respectively. Rates as low as 140 g/ha caused lint yield reductions depending on year and location. When averaged over all locations, lint yield reductions of 4, 49, 72, and 87% compared with nontreated cotton were observed with glyphosate rates of 140, 280, 560, and 1,120 g/ha, respectively. Visual injury and shikimic acid accumulation were evident at glyphosate rates greater or equal to 70 g/ha. Collectively, visual injury and shikimic acid accumulation at 7 d after EPOST treatment might be used as a diagnostic indicator to predict potential yield reductions from simulated glyphosate drift.

Glyphosate, a chelating agent—relevant for ecological risk assessment?

“…There are only few studies on the potential impact of glyphosate-based herbicides on the mineral content of non-target plants, such as non-resistant crops or ornamental plants, although they can be affected by spray drift (Thomas et al 2005 ) and by soil residues (Tesfamariam et al 2009 ). Plant to plant transfer of glyphosate via root exudation has been observed too, exerting inhibitory effects on the shikimate pathway, uptake of micronutrients (Mn), and growth of non-target sunflowers (Neumann et al 2006 ).…”

Deriva simulada de formulações comerciais de glyphosate sobre maracujazeiro amarelo

“…A interrupção do crescimento apical teve reflexos no comprimento total das plantas de maracujazeiro amarelo em decorrência da aplicação das maiores doses de glyphosate (Figura 2B). De acordo com Thomas et al (2005), entre as injúrias visuais provocadas por herbicidas está o atraso no desenvolvimento das plantas.…”

Yield and Physiological Response of Peanut to Glyphosate Drift

“…Many crops, depending on growth stage, are sensitive to glyphosate drift that can cause yield loss (Al-Khatib et al 2003;Burke et al 2005;Griffin 2002, Ellis et al 2003;Thomas et al 2005). Kurtz and Street (2003) reported yield loss in rice (Oryza sativa L.) with glyphosate at 70 g ai/ ha or higher and Koger et al (2005) found that glyphosate was injurious to rice quality.…”

“…Due to the inhibition of EPSP synthase, shikimate-3-phosphate, a precursor to shikimic acid, accumulates in treated plants. The accumulation of shikimic acid is unique to glyphosate-treated plants (Pline et al 2002;Ray 1989;Steinrucken and Amrhein 1980;Thomas et al 2005). Due to the accumulation of shikimic acid in response to glyphosate treatment and the availability of a shikimic acid assay, these assays may be used to predict potential yield losses due to glyphosate drift.…”