Influence of selected environmental factors on glyphosate efficacy when applied to awnless barnyard grass (Echinochloa colona (L.) Link)

Abstract

Glasshouse experiments were conducted to determine the effects of various environmental factors on glyphosate efficacy when applied to Echinochloa colona (L.) Link (awnless barnyard grass) plants. The variables examined were 4 soil moisture conditions (29, 42, 55, and 100% of field capacity), 2 levels of irradiance (400 and 800 µmol/m2· s), 3 temperature regimes (20/15, 30/25, and 35/30°C; day/night), and 2 levels of relative humidity (92 and 65%). The efficacy of 360 g acid equivalent glyphosate/ha was greatest when applied to well-watered (field capacity) plants that were placed under cool (20/25°C) and humid (92% relative humidity) conditions. The efficacy was least when applied to plants under severe water stress (29% of field capacity) that were placed under hot (35/30°C) and less humid (65% relative humidity) conditions. In all experiments, efficacy was not altered by the level of irradiance.

Target-site EPSPS Pro-106 mutations: sufficient to endow glyphosate resistance in polyploidEchinochloa colona?

“…Although not examined in our study or in other studies, reduced glyphosate efficacy at high temperatures may be due to increased glyphosate upward movement caused by higher rates of plant transpiration, thus decreasing glyphosate translocation. E. colona is the most common weed of summer fallows in the north‐eastern grain region of Australia; extreme growing conditions have been recorded, and higher temperatures (over 35 °C) in summer are quite common . In addition, other factors reducing glyphosate rates (e.g.…”

Size selectivity of aqueous pores in stomatous cuticles of Vicia faba leaves

“…Permeability of poplar cuticles to ionic glyphosate salts increased by a factor of 5-10 when relative humidity was increased from 70% to 100% (Scho¨nherr 2002). High humidity increased the herbicidal efficacy of glyphosate (Tanpipat et al 1997;Adkins et al 1998). Permeability of pear leaf cuticles for calcium chloride (Scho¨nherr 2002) and potassium carbonate (Scho¨nherr and Luber 2001) also increased with increasing humidity.…”

Glyphosate Efficacy on Velvetleaf Varies with Application Time of Day

“…However, changing light level from full to 50% sunlight did not change the response to glyphosate. Similarly, glyphosate activity on junglerice [Echinochloa colona (L.) Link] increased as temperature increased from 20 to 35 C, but glyphosate activity was unaffected by different lightdark periods (Tanpipat et al 1997).…”

“…Glyphosate activity or absorption increased with increasing RH for quackgrass [Elytrigia repens (L.) Nevski] (McIntyre and Hsiao 1982), bermudagrass (Jordan 1977), liverseedgrass (Adkins et al 1998), junglerice (Tanpipat et al 1997), and johnsongrass (McWhorter et al 1980). Generally, high RH and high temperatures, as well as low light intensity before treatment followed by high light intensity after treatment, increase plant susceptibility to POST herbicides (Hammerton 1967).…”