Insecticide Residues in Organic Soil of the Holland Marsh, Ontario, Canada, 1972–751

Abstract

Insecticide residues in the organic soils of the Holland Marsh, Ontario, were determined from 1972–75, inclusive. Soil samples were collected annually in the fall. Organochlorine and organophosphorus (OP) insecticide residues were determined using GLC. DDT residues (p,P'-DDT, o,P'-DDT, p,P'-TDE, o,P'-TDE, and p, P'-DDE) averaged 28.6 ppm over the 4-yr period. Only limited degradation of DDT is occurring in these organic soils. Residues of 6 cyclodiene insecticides were detected. Levels of aldrin, endrin, and, to a lesser extent dieldrin, may be declining slowly. However, increased use of endosulfan and occurrence of its residues in soil has resulted in total-cyclodiene residues remaining relatively stable, averaging 1.8 ppm over the 4 yr. Nine OP insecticide residues were present. Total-OP insecticide residues, averaging 5.6 ppm over the 4 yr, were considerably in excess of the total-cyclodiene residues. Ethion, used as a seed furrow treatment for control of 1st-generation onion maggot, Hylemya antiqua (Meigen), comprised 80% of the total-OP residues. Experiments indicated ca. 25% carryover to the next spring of ethion applied to organic soil in the granular form. Residues of parathion, diazinon or both were detected in soil on all 13 farms but at levels 1/9 and 1/30, respectively, of those found for ethion. Other OP insecticides detected at avg 4-yr levels ≥ 0.1 ppm included fonofos, chlorpyrifos, VC-13® (O-2,4-dichlorophenyl O,O-diethyl phosphorothioate), and chlorfenvinphos.