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Starch-Encapsulated Atrazine: Efficacy and Transport

USDA-ARS, Dep. of Botany and Plant Pathology, Purdue Univ., West Lafayette, IN 47907.

^* Corresponding author.

ABSTRACT

Current data indicate that pesticides are a contributor to the groundwater contamination problem, with the herbicide atrazine [6-chloro-N-ethyl-N'-(1-methylethyl)-1,3,5-triazine-2,4-diamine] one of the most commonly found contaminates. Reports indicate that the highest levels of atrazine found appear to be associated with the heavy spring rains following application of presently used commercial formulations (CF) of atrazine. This work reports the role of new starch encapsulated (SE) granular formulations of atrazine that significantly reduce the initial mobility of atrazine without appreciable loss of weed control efficacy. Leaching studies in the laboratory indicate that SE formulations reduced movement of atrazine by 70% compared to CF in both silty clay loam and sandy soils following a 75 mm h^–1 simulated rainfall. Results from leaching of intact soil blocks with simulated rainfall of 40 mm h^–1 for 2 h showed CF leached 80 and 60% more atrazine than the SE formulation from chisel and no-till systems, respectively. Granular size of SE formulations can affect the rate of release. Starch-encapsulated formulations gave good to excellent control of most weeds at 10 sites in six Midwest states during the 1990 and 1991 growing seasons and resulted in corn (Zea mays L.) yields equal to or better than with CF. Control of some large seeded weeds such as velvetleaf (Abutilon theophrasti Medic.) and cocklebur (Xanthium strumarium L.) was variable from site to site with both SE and CF. Starch-encapsulated formulations offer an excellent potential technology advancement for significant reduction of atrazine and other pesticide contaminates of groundwater with minimal loss of efficacy.

Published as Purdue Agric. Exp. Stn. J. Paper No. 13386.

Received for publication June 19, 1992.