Persistence and degradation of chlorfenvinphos, diazinon, fonofos and phorate in soils and their uptake by carrots

Abstract

Analytical methods are described for the determination of residues of chlorfenvinphos, diazinon, fonofos and phorate in soils and carrots. The insecticides, applied in June 1969 at 2 kg (a.i.)/ha, persisted longer in peaty loam than in sandy loam. After 7 months, the sandy loam contained 1% of the applied diazinon and 20–30% of the applied chlorfenvinphos, fonofos and phorate, the latter as its sulphone; the corresponding figures for the peaty loam were 10, 40–50, 40–50 and 30–40% respectively. None of the residues showed any substantial change from October to January. Although high initial concentrations (up to 50 ppm) of the residues in carrots were diluted by plant growth, it is shown that concentrations >1 ppm could be present in marketable crops 12–14 weeks after application at recommended rates. Carrots harvested 26 weeks after sowing contained <0.2 ppm of all insecticides. In contrast, during the first 15 weeks of crop growth the weights of residues in the carrots increased and remained approximately proportional to the square root of the carrot mean weight. Rates of uptake declined as carrot growth declined and subsequently the amounts of chlorfenvinphos, diazinon and fonofos residues in the carrots changed very little, while phorate sulphone steadily declined.

Soil Placement of Insecticide Granules for the Control of Cabbage Root Fly on Transplanted Canliflowers

“…Chlorfenvinphos granules, were consistently the most effective material in controlling ca.bbage root fly by both the sub-surface and the surfa.ce methods of application but gave better results by the former method. This result supports the findings of Suett (1971), who repO'rted that chlorfenvinphos persists for many weeks at effective dosage levels when incorporated in the soil but degrades very rapidly at the soil surface at high temperatures.…”

Interactions between insecticides and soil microbes

“…When the Arthrobacter and Streptomyces were incubated together, however, no diazinon was detected at 21 days. SUETT (1971) found considerable diHerence in the persistence of diazinon in sandy loam and peaty loam. Mter 7 months only 1 % of the applied diazinon remained in the sandy loam but 10% was recovered from the peaty loam.…”

The metabolism and degradation of vinyl phosphate insecticides

“…Indeed, small residues of chlorfenvinphos have been detected in some sampIes of root crops grown in the Held in treated soH, but residues of the degradation products have not been detected under these practical conditions (BEYNON et al 1966, SUETT 1971. SUE'IT (1971) studied the rate of uptake of chlorfenvinphos residues from treated soil by carrots.…”