EFFECTS OF ENVIRONMENT ON UPTAKE AND TRANSLOCATION OF MON 0818 ADJUVANT AND GLYPHOSATE COMBINED WITH ADJUVANTS IN FIELD BINDWEED (CONVOLVULUS ARVENSIS L.) (SURFACTANT, PENETRATION, ABSORPTION)

STEWART LEE SHERRICK, Purdue University

Abstract

Adjuvant enhancement of herbicide activity is often thought to be the result of reduction in surface tension and thus enhanced wetting, spreading, and sticking to the leaf surface. However, the specificity of many adjuvants and the concentrations which maximize activity indicate a more complex action. Uptake and translocation of glyphosate with and without adjuvants and MON 0818 (polyethoxylated tallow amine) were examined to develop an understanding of the influence of selected adjuvants and environment on glyphosate activity. Light intensity and humidity during plant development resulted in differences in 14C-glyphosate uptake. When applied in water or with oxysorbic (20 POE) adjuvant, 6% or 13% of the glyphosate was absorbed in plants developed in high light intensity, low humidity (HLLH) as compared to 17% or 26% in plants grown in low light, high humidity (LLHH). Levels of epicuticular wax on HLLH field bindweed were almost three times as great as on LLHH field bindweed leaves and may explain uptake differences. No differences in glyphosate uptake were observed between glyphosate applied with oxysorbic or no adjuvant even though oxysorbic effectively reduced surface tension. Uptake was increased 2 to 3 fold with MON 0818 adjuvant as compared to no adjuvant and was insensitive to environmentally induced differences in field bindweed. Uptake continued for 24 to 36 hours after application regardless of adjuvant. Altered distribution patterns appeared to correlate with adjuvant concentrations and the resulting necrosis. Reductions in MON 0818 concentration and subsequent necrosis resulted in increased movement of radioactivity away from the site of application. Scanning electron microscopy did not reveal any physical disruption of the epicuticular waxes from spray applications of MON 0818, Tween 20 or glyphosate. Radioactive MON 0818 uptake was rapid during the first six hours. Maximum uptake (84%) occurred by 24 hours after application. Less than 3% of the applied radioactivity was recovered from the epicuticular wax of treated leaves. Movement of radioactivity out of the treated area was limited predominantly to the treated leaf. Altering light intensity or humidity in which the plants developed prior to treatment did not influence MON 0818 uptake.

Degree

Ph.D.

Subject Area

Botany

COinS