Effects of Droplet Composition on Glyphosate Absorption and Translocation in Velvetleaf (Abutilon theophrasti)

Abstract

In laboratory studies, absorption and translocation of glyphosate in velvetleaf was dependent on the concentration of both glyphosate and surfactant in the applied droplet(s). At equivalent total quantities applied, absorption by leaves was greater with concentrated droplets than with more dilute droplets in greater number. Increasing the surfactant concentration increased the relative absorption of dilute glyphosate droplets but did not overcome the negative effect of higher droplet number on total amount absorbed. More glyphosate was translocated from concentrated versus the most dilute droplets at equivalent total quantity applied. Conversely, more absorbed glyphosate from dilute droplet applications remained in the treated leaves. About 90% of translocated14C glyphosate from the most concentrated drops was distributed evenly between roots and shoot tissue above the treated leaf and the remainder in shoot tissue below the treated leaf. As droplet number increased and surfactant concentration decreased, the relative amount of glyphosate distributed in roots declined in relation to shoots.