Fonofos residues in an organic soil and vegetable crops following treatment of the soil with the insecticide

Abstract

Fonofos (0-ethyl S-phenyl ethylphosphonodithioate) was applied to an organic soil as band treatment at the rates of 1.12 and 2.24 kg/ha. The persistence of the insecticide and its translocation into onions and two rotation crops (lettuces and carrots) was studied under field conditions. Proportionally more residues persisted in the soil from the higher rate of application. In autumn, 4 months after soil treatment, about 40-48 % of the initially recovered levels of fonofos remained in soil. However, the amount of fonofos present at the harvest time, during the second growing season was only 16-26 % of the insecticide concentration found in spring. Onions harvested 4 months after application of fonofos had no detectable residue (> 0.005 mg/kg) whereas lettuces and carrots grown in the following year contained fonofos in various amounts. At the lower rate of application the insecticide residues in lettuces and carrots were <0.005 and 0.025 mg/kg, respectively, and those from the higher application rate were 0.012 and 0.036 mg/kg. About 7240% of the residue could be removed by peeling the carrots. No residue of the oxygen analogue, 0-ethyl S-phenyl ethylphosphonothioate (I) was detected in any soil or crop samples.

Effect of endomycorrhizae on the bioavailability of bound carbon-14 residues to onion plants from an organic soil treated with [14C]fonofos

“…These data indicate that bound 14C residues in soil treated with [14C]fonofos become bioavailable and are taken up into onion plants. Previously, workers had shown negligible (Khan et al, 1976) or limited (Khan and Belanger, 1987) fonofos uptake into onion from soil containing both bound and extractable residues. The mechanism of uptake and the form of 14C absorbed by hyphae and roots were not elucidated.…”

“…Soil. A Humic Mesiosol organic soil previously described (Khan et al, 1976) was used. The soil was treated in the field with [ring-14Cjfonofos (10% granular formulation, 7.6 kg-ha",) and collected after a cropping season (Khan and Belanger, 1987).…”

“…This study was undertaken to determine whether selected endomycorrhizal soil fungi could influence the fate of bound residues of fonofos (0ethyl S-phenyl ethylphosphonodithioate) in an organic soil. Fonofos, an organophosphorus insecticide, is used in onion cultivation to control onion maggots [Hylenga antigua (Meig)] and is known to form bound residues in organic soils (Khan et a!., 1976).…”

Degradation of imazethapyr in soil: impact of application rate, soil physicochemical properties and temperature

“…Large-scale studies (Birk and Roadhouse, 1964;Hunter and Stobbe, 1972;and Khan et al, 1976) are conducted using normal agricultural practices (e.g., cultivation prior to planting, etc.) and equipment.…”