Insecticide Residues on Forage under Sprayed Pecan Trees

Abstract

Guthion® ( O,O -dimethyl S -( 4-oxo-1, 2,3-benzotriazin-3-(4 H )- ylmethyl) phosphorodithioate), EPN and parathion applied to pecan trees in three applications at 2-week intervals using 2 pounds of wettable powder (15% or 25% active ingredient) 40% toxaphene in two applications 2 weeks apart using 6 pounds of wettable powder per 100 gallons of spray yielded initial deposits of forage under the trees of from approximately 1 to 60 p.p.m. for Guthion, 24 to 76 p.p.m. for EPN, 4 to 28 p.p.m. for parathion and 488 to 672 p.p.m. for toxaphene. Two weeks after any application, parathion residues were all below 1 p.p.m. with one exception during a dry period, Guthion residues ranged from 0.6 to 10.3 p.p.m. and EPN residues from 0.4 to 5.3 p.p.m. Toxaphene residues ranged from 69 to 126 p.p.m. after weathering 2 weeks and 23 p.p.m. remained 10 weeks after the second application.