Insecticide Residues on Vegetables1

Abstract

Snap beans, tomatoes, and collards were dusted at the rate of 30 pounds per acre when they were ready for harvest. Samples were taken immediately after treatment and daily thereafter. All residues showed a linear decrease except for the effect of rainfall. The initial residue on collards was much greater than on snap beans. Snap beans had a greater amount of residue than tomatoes. DDT (10%), methoxychlor (5%), and toxaphene (20%) persisted for at least 12 days on collards and snap beans. There was no detectable toxaphene residue on tomatoes after the ninth day and DDT and methoxychlor residues were nearly gone after the 12th day. Lindane (1%) residues were detectable up to the third day on tomatoes, up to the fourth day on snap beans, and only as a trace on collards by the 13th day. Malathion (4%) and endrin (2%) were detectable for 3 days on snap beans, 2 days on tomatoes, and 3 days on collards. Rainfall removed them from the collards on the fourth day. Rainfall effected a greater reduction of residues during the early period after application than during later periods. Methods used for determining residues are cited.