Persistence and degradation of chlorfenvinphos, chlormephos, disulfoton, phorate and pirimiphos‐ethyl following spring and late‐summer soil application

Abstract

Granular formulations of chlorfenvinphos, chlormephos, disulfoton, phorate and pirimiphos‐ethyl were broadcast at 2 kg a.i./ha and incorporated to 100 mm into a sandy‐loam soil either in May or in September 1971. The relative persistence of their residues, including insecticidally active oxidation products, after both application dates was disulfoton > chlorfenvinphos > phorate > pirimiphos‐ethyl > chlormephos. When applied in September all the insecticides persisted for longer than when applied in May. Degradation was slower during the winter while the mean soil temperature at 100 mm depth remained below 6 to 7°C. Rising soil temperature in the following spring rapidly increased the rates of degradation of chlorfenvinphos, chlormephos and pirimiphos‐ethyl residues but not of disulfoton‐ and phorate‐derived residues, predominantly the parent sulphones, which had been leached deeper. Ten months after the September application, half the total residues derived from disulfoton and phorate were found below the initial incorporation depth, whereas the other insecticides showed relatively little downward movement. It was concluded that late summer/early autumn applications for carrot fly control would leave appreciable residues of some insecticides in the soil at the beginning of the next growing season which may contribute to the terminal residues in crops. These would be minimised if moderately persistent compounds were used or if doses of persistent ones were substantially reduced.

Degradation of [14C]isofenphos in soil in the laboratory under different soil pH'S, temperatures, and moistures

“…However, the temperature at which this decrease takes place for most microbes is higher than the 35 C used in this experiment, and the optimum temperature range for growth of the most of the soil microorganisms is 25 to 35 C (Kaneko et al 1978). It has been reported that insecticides degraded faster in soil as soil temperature increased (Menzer et al 1970;Wheatly et al 1972;Suett, 1975). Miles et al (1983) reported an increase of chlorpyrifos and chlorfenvinphos In soil due to the increased production or reactivity of microbially generated enzymes with the insecticide substrate.…”

Comparative degradation of organophosphorus insecticides in soil: specificity of enhanced microbial degradation

“…This has 1980). The ephemeral nature of terbufos and phorate in soil has been well documented (Getzin and Chapman, 1960;Suett, 1975;Sellers, et al, 1976;Chapman et al, 1982a,b), and it is terbufos sulfoxide and phorate sulfone that are been true to some extent with the carbamate insecticides (Harris et al, 1984;Felsot, 1986), thiocarbamate herbicides ( Wilson, 1984; Harvey et al, 1986), and phenoxyacetic acid herbicides (Kirkland and Fryer, 1972). However, the enhanced degradation of organophosphorus insecticides in soil has usually been associated with a lesser degree of crow adaptation.…”

Degradation of Organophosphorus Insecticides in Environmental Matrices

“…As shown in Table VI, soil half-lives for chlorfenvinphos in several studies were 7, 63, and 135 days (Miles et ai, 1979;Suett, 1975;Bro-Rasmussen et al, 1970). As shown in Table VI, soil half-lives for chlorfenvinphos in several studies were 7, 63, and 135 days (Miles et ai, 1979;Suett, 1975;Bro-Rasmussen et al, 1970).…”