Glyphosate Efficacy on Velvetleaf Varies with Application Time of Day

Abstract

Field and growth chamber experiments determined the efficacy of temporal glyphosate applications on velvetleaf. Glyphosate was applied postemergence to velvetleaf periodically before and during light and after dark. In 1999, glyphosate at 840 g ae/ha applied before sunrise and after midday provided 54 and 100% velvetleaf control, respectively. In 2000, glyphosate at 840 g/ha applied before sunrise, midday, and after sunset provided 69, 100, and 37% velvetleaf control, respectively. In the growth chamber, glyphosate at 840 g/ha applied before or after light reduced velvetleaf biomass 15 to 20% or 32 to 47%, respectively, and reduced velvetleaf height 24% or 45 to 54%, respectively. Velvetleaf control was consistently greater with glyphosate applications during light compared with dark, regardless of constant air temperature and relative humidity (growth chamber), dew absence or presence (field and growth chamber), or leaf blade orientation (growth chamber) with natural light-dark movements or a fixed horizontal position.

Fatores Ambientais Que Afetam a Eficácia De Glifosato: Síntese Do Conhecimento

“…A variação do ângulo foliar em função da hora do dia em algumas espécies provavelmente se deve a adaptação às diferentes condições de irradiância. Maior intensidade luminosa provoca incremento no ângulo foliar de determinadas espécies, fato que permite inclinação mais horizontal (WALTZ et al, 2004). A aplicação de glifosato ao meio-dia permitiu aumento de 31 % no controle de A. theophrasti em comparação aos períodos de baixa luminosidade (MOHR, SELLERS e SMEDA, 2007).…”

Common Lambsquarters Response to Glyphosate across Environments

“…Waltz et al (2004) reported control of velvetleaf with glyphosate in the field to be correlated with the air temperature at the time of herbicide treatment. However, we did not find a relationship between ambient air temperature and common lambsquarters control by glyphosate.…”

“…(McWhorter and Azlin 1978) and quackgrass [Elymus repens (L.) Gould] (Klevorn and Wyse 1984). A time of day effect on glyphosate efficacy has been observed in velvetleaf (Mohr et al 2007;Waltz et al 2004), common lambsquarters, common ragweed, foxtail species (Martinson et al 2002), and barnyardgrass in some studies (Mohr et al 2007) but not in others (Stewart et al 2009). Ambient air temperatures can also affect glyphosate efficacy, absorption, and translocation (Adkins et al 1998;Jordan 1977;Masiunas and Weller 1988;Reddy 2000;Sharma and Singh 2001;Tanpipat et al 1997).…”

Physiological and Genetic Bases of the Circadian Clock in Plants and Their Relationship with Herbicides Efficacy

“…Studies in the field and in greenhouses showed that glyphosate applications during a period with higher photosynthesis rate (between 10:30 a.m. and the sunset) offered better control levels. This effect is related to the fact that, because it is a herbicide with systemic action, high photosynthesis rates increase the transportation of metabolites in the plant, allowing the increment of the glyphosate translocation (Waltz et al, 2004). Some weed species are less sensitive to glyphosate since they show lower herbicide translocation (Shaner, 2009;Galon et al, 2013).…”