Atrazine Drift Studies with Horticultural Crops

Abstract

The feasibility of diagnosing atrazine drift accurately with physical symptoms and tissue analysis was studied extensively with cucumber plants. Concentrations of atrazine ranging from 0.0005 to 1.0 lb. active/A were sprayed on mature cucumber plants. Although the physical symptoms resembled many other types of damage, the symptoms were sufficiently distinct to be used as secondary evidence along with tissue analyses. Physical symptoms appeared initially 2 or 3 days after the spraying as marginal and/or intervenal chlorosis. These chlorotic symptoms turned briefly to a bleached-white color on the leaves, which became necrotic within 5 days after spraying. The H. S.P.A. Method, an ultraviolet spectrophotometrlc method, was evaluated and found suitable to detect the presence of atrazine in cucumber tissue at levels where physical symptoms were difficult to detect and essentially no damage occurred. Although the addition of alumina columns to the H.S.P.A. Method was not necessary with cucumber leaves under the test conditions, they were beneficial when snap beans were analyzed. Alumina columns decreased interfering background and were not responsible for any loss of atrazine. To determine the best time to sample, cucumber plots were sprayed with 0.1 lb. active/A atrazine and harvested 12 hours, 1, 2, 4 and 7 days after the spraying. The samples were analyzed using the H.S.P.A. Method. The sampling time experiment showed a rapid decrease of atrazine from the time of spraying to 4 days after the spraying and very little decrease of atrazine from 4 to 7 days. For consistency samples should be taken 4 to 7 days after the suspected drift even though an earlier sampling would give higher tissue readings. After 7 days the damaged leaves started to fall from the plant. In all field experiments the sampling of only the most damaged leaves proved to be a very satisfactory procedure.