Incorporation and stability of chlorfenvinphos,chlorpyrifos, diazinon and phorate in peat blocks

Factors likely to influence the uniformity of treatment and the stability of the insecticides incorporated into peat blocks were investigated. When an Adelphi horizontal mixer was used, 90% of the blocks contained the mean dose (±10%) after dry-mixing the diazinon granules for 3 min. Treatment was slightly less uniform using a concrete mixer or a spade. Between-block variability was greatest when diazinon was applied to the wet surfaces of prepared blocks; in this process, sprinkling granules by hand was less erratic than spraying a liquid formulation. When granular, wettable powder, or emulsifiable concentrate formulations of diazinon were incorporated using the Adelphi mixer, neither the between-block variability nor the subsequent stability of the insecticide were significantly influenced by the formulation used. Insecticide stability was studied by incorporating chlorfenvinphos, chlorpyrifos, diazinon and phorate at 10 mg a.i. per block in January, March, May and July. The relative order of persistence was chlorfenvinphosChlorpyrifos > phorate≫diazinon. There was little loss of insecticide ( < 10%) from the blocks treated with chlorfenvinphos or chlorpyrifos, and the stability of the insecticides was unaffected by seasonal temperature changes, but the rate of loss of diazinon increased markedly from January to July. The rate of oxidation of phorate to its sulphoxide and sulphone analogues increased gradually from January to May but was much slower than in the field after a bow-wave application. With all insecticides, there was no significant difference in loss rates at 25 and 10 mg a.i. per block. After incorporation into three moss peats and two proprietary blocking composts, there was no consistent difference in the rates of loss of either diazinon or of total phorate residues, although the rates of oxidation of phorate and its sulphoxide were not similar in all the peats and composts. It was concluded that, despite the substantial water content and high insecticide concentrations, the principal factor determining insecticide behaviour in the blocks was the adsorptive capacity of the peat.     

Uptake of chlorfenvinphos and phorate from soil by carrots as influenced by mode of application and cultivar

Granular formulations of chlorfenvinphos and phorate were applied to sandyloam soil at 2 kg a.i./ha either broadcast and incorporated to 2.5 cm, broadcast and incorporated at 10 cm or by the bow-wave method along the carrot rows. Depth of incorporation did not influence the rates of residue decline in the soil. Bow-wave applications produced the highest residues in root and foliage and also reduced the rate of oxidation of phorate. 30 weeks after sowing the carrots, all treatments gave the highest residue concentrations in the uppermost 6 cm of carrot root. The peel of carrots grown in the soil treated to a depth of 10 cm contained 88 % and 23 % of the total chlorfenvinphos and phorate residues respectively. Significant differences were found in the residue concentrations in five carrot cultivars treated with chlorfenvinphos and phorate by the bow-wave method at 1.5 kg a.i./ha. The concentrations were inversely correlated with root size so that amounts of insecticide (μg/carrot) were similar in all cultivars. Prolonged growth of cv. Norfolk Giant slightly extended the period of uptake of chlorfenvinphos, but the uptake of phorate was ultimately less than its rate of dissipation. Neither the method of application nor the selection of carrot cultivar extended the period of uptake very greatly but differences which were obtained in residue concentrations in the carrot may become significant in the event of regulatory control of residue levels.     

Effects of placement and distribution on the performance of granular formulations of insecticides for carrot fly control

Effects of granule distribution relative to carrot rows are discussed and further results described. Placing insecticides 5 to 10 cm deep 7.5 cm away from the centre line of the carrot row usually, but not always, improved their performance compared with bow-wave applications. Both sides of the row need to be protected. The efficiency of chlorfenvinphos in a sandy loam, and phorate in a peaty-loam, decreased with increasing distance from the row but they were slightly effective even 19 cm away. The optimum depth for side-placing granules at sowing time varied from 5 to 10 cm, and combining side-placement with a bow-wave application did not greatly enhance efficiency. The most effective combination on a peaty-loam was a bow-wave application of 3 kg phorate/ha at sowing time followed 6 to 9 weeks later by a similar amount side-placed 7.5 cm deep 7.5 cm from the row centre. Comparison of the performance of phorate broadcast, applied by the bow-wave method or deep side-placed indicated that efficiency was improved by restricting the granule distribution but that higher concentrations of granules were then needed in the treated zones to be equitoxic with more uniformly broadcast granules. Uptake by the carrot root system is an important factor in the action of insecticides against carrot fly larvae.     

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

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.     

The Efficacy and Residual Toxicity of certain Granular Insecticides against Mustard Aphid,Lipaphis erysimi (Kalt)

Abstract

The systemic activity of four granular insecticides (phorate 10%, Temik 10%, diazinon 5% and Sevidol [8% carbaryl + 8% gamma-BHC]) was evaluated for the control of mustard aphid, Lipaphis erysimi (Kalt). The granules were applied in the soil to one month old mustard plants transplanted in pots. 3rd and 4th instar nymphs were used for the trial. Mortality counts were made 24 hours after release. Of the insecticides tested, phorate and Temik at 1 lb a.i./ac proved most effective. Temik had a quick knockdown effect as compared to phorate, as it gave 100% control within 24 hours, while with phorate 100% kill was obtained only after 72 hours. Diazinon at 4 lb a.i./ac gave 83.3% kill after 72 hours. Sevidol proved ineffective as an aphidicide. Residual toxicity of three of the granular insecticides, namely phorate, Temik and diazinon, was tested. Phorate and Temik at 1 lb a.i./ac exhibited the same residual toxicity up to 4 weeks, i.e. 100% and 76% kill obtained at the end of 2 and 4 weeks respectively. Although the toxicity of both pesticides gradually declined there was no significant difference in percentage kill over a period of 5 weeks. After 6 weeks, however, the mortality recorded with Temik was 37.1% and with phorate was 51.1%. The residual toxicity of phorate was further found to last up to 8 weeks, when the mortality obtained was 40%. The residual toxicity of diazinon sharply declined within 2 weeks.     

Effects of phorate placement on carrot fly control,seedling density and terminal residues in the crop

The application of granules containing 10 % phorate at 1.12,2.24 or 4.48 kg a.i./ha in a narrow slit together with carrot seed significantly reduced seedling emergence in both a mineral and peat soil. When the granules were applied at 2.24 or 4.48 kg a.i./ha in a narrow slit 2.5 cm below the seed, seedling emergence was adversely affected only at the higher rate in the mineral soil. Phorate granules applied with the seed in the peat soil gave a significantly lower plant density than when applied below the seed, but subsequent carrot yields were unaffected because much larger roots were produced. All phorate treatments gave effective reduction of carrot fly larval damage to the roots. On the peat soil, there were significant increases in total phorate residues present in mature carrots with increasing rate of phorate granules placed with the seed. Placement of the granules 2.5 cm below the seed resulted in a 50% reduction in total residues of phorate in whole carrots compared with placing the granules with the seed. Residues resulting from 1.12 kg a.i./ha with the seed or 2.24 kg a.i./ha 2.5 cm below the seed were not significantly greater than residues in untreated carrots.     

Control of wireworms with organophosphorus and carbamate insecticides

Carbaryl, chlorfenvinphos, diazinon, disulfoton, parathion, phorate, fenitrothion, thionazin and trichlorphon were tested for their effectiveness in killing wireworms by broadcast treatments. Each insecticide was tested once or more in two field trials cropped with wheat and two cropped with potatoes. Phorate and parathion were very lethal to wireworms at 4 Ib active ingredient per acre (4–48 kg/ha). Thionazin and diazinon were intermediate in effectiveness and the other insecticides ineffective.     

Insecticidal control of hessian fly (Mayetiola destructor say: Dipt., Cecidomyiidae) on wheat and barley in cyprus

Hessian fly was controlled to a maximum of 95% with organophosphate insecticides, in terms of the number of puparia and percentage tiller infestation at harvest. Granules: phorate at 1.68 kg/ha (1 1/2 lb/acre) as 10% granules in the seed furrow was most effective on durum wheat in 1967–8, with 69–92%, control, of tillers infested. 1.12 kg/ha gave 74–89% control, 0.56 kg/ha in the seed furrow 35–54%. Seed furrow treatment was more effective than band or broadcast treatment over young plants, although granules broadcast over young barley at 1.68 kg/ha of phorate gave 74% control in 1967–8. Fonofos (Dyfonate) granules at 1.55 kg fonofos/ha were most effective on barley in 1968–9, with 66% control. After fonofos and phorate, disulfoton at 1.68 kg disulfoton/ha was next in effect, with up to 86%, control in 1967-8 and 24% in 1968–9, but variable and not much more effective than at 0.56 kg/ha. Other insecticides were less effective. Seed dressings: disulfoton was the most effective, giving 79% control in 1967-8 on wheat and 77% on barley at a high rate of application that was phytotoxic in 1968–9. Diazinon, bromophos and ethion gave 15–38%, control and chlorfenvinphos and dimethoate less. Carbaryl dust at 1.12 kg carbaryl/ha gave 32% control. Yields were poor, but grain yield was increased by up to 33% in wheat in 1967-8, averaging about 15%. Barley yield was increased by 7% in 1967–8, and from 9–23% in 1968-9 by fonofos and phorate granules. Insect control reduced the number of tillers, increased the number of heads and increased the grain weight per head. In observation plots, chlormequat (CCC) spray alone at the 5-leaf stage reduced infestation of wheat by between 22% and 43%, but CCC with fertilizer, and fertilizer alone had no conclusive effect. High fly populations are partly due to leaving crop residues in the field at harvest. When these can be ploughed in, infestation should decrease. The use of insecticides may not be economic unless more consistent increases in yield can be obtained.     

Influence of block and cell size,growing medium and insecticide dose on the behaviour and uptake of phorate by lettuce and uptake of carbofuran and chlorfenvinphos by calabrese

Phorate residues in peat blocks and lettuce were determined following incorporation of the insecticide into different block and ‘Speedling’ cell sizes. Between-block variability was influenced little by block size. Phorate oxidation was most extensive in the largest blocks containing the smallest dose. Total residue concentrations in the lettuce declined from the time of planting to harvest, although accumulation of insecticide continued and was related more to dose than to block or cell size. Residues in the lettuce at harvest exceeded the proposed maximum limit of 0.2 mg kg^?1 in some treatments. Residues at planting comprised mainly the parent sulphoxide and sulphone, but by harvest, the oxygen analogue sulphoxide and sulphone predominated. Lettuce weight was not influenced by dose but was related directly to block size. Carbofuran and chlorfenvinphos residues were determined in calabrese sown into two sizes of blocks. At planting time, carbofuran residue concentrations were 100 times greater than those of chlorfenvinphos but residues of both insecticides in the mature heads were < 0.01 mg kg^?1. Seedling weights in both sowings declined with increasing concentrations of the insecticides. It was concluded that manipulations of block size and the dose of insecticide need to be evaluated for individual insecticide/crop combinations to exploit the technique fully.     

Dissipation rates of insecticides in six minor vegetable crops grown on organic soils in Ontario,Canada

Dissipation rates of diazinon, endosulfan, leptophos, methamidophos, methomyl, parathion and pirimicarb were studied on five minor vegetable crops, including cos and head lettuce, endive, cauliflower and Chinese cabbage. Residues from foliar treatment generally followed an exponential rate of decline. The number of days for residues to drop to below acceptable tolerances was highly dependent on the magnitude of the initial residue; large variations in initial residues were observed between years, between insecticides, and between crop types. Residues of five insecticides and two fungicides used in furrow treatments for onions intended for pickling were determined in the onions at harvest and after pickling. Fensulfothion and fonofos levels were below the accepted tolerance of 0.1 mg kg^?1 at harvest, while chlorfenvinphos, chlorpyrifos and ethion were present above this level; fungicide residues were not detected. Following pickling, only ethion residues were still present in the onions at levels greater than 0.1 mg kg^?1.     

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

Fonofos (O-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 72–80% of the residue could be removed by peeling the carrots. No residue of the oxygen analogue, O-ethyl S-phenyl ethylphos-phonothioate (I) was detected in any soil or crop samples.     

Dislodgeable residues and persistence of diazinon,chlorpyrifos and isofenphos following their application to turfgrass

In laboratory experiments, residues of diazinon applied to turfgrass, Poa pratensis L., that could be dislodged by rubbing with cheese-cloth, declined from c. 10% of the total applied when the grass was vigorously rubbed immediately after application to 0.3% after 1 day. Sunlight did not influence the rate of decline in dislodgeable residues or residues remaining on or within the leaf blades. In field experiments where 4.5 kg ha^?1 of diazinon was applied in liquid or granular form, about 20 times more diazinon was dislodged from the liquid formulation immediately after application than from the granular. By 1 day after application the percentage of the total applied diazinon that could be dislodged was equal for both formulations. Rainfall had a significant effect on the amount dislodged from grass blades, but mowing did not. Similar rates of decline in the dislodgeable fraction of diazinon, chlorpyrifos and isofenphos were observed in field experiments. Recovery of the dislodgeable fraction declined to 0.25% or less of the total amount of any of these insecticides by 1 day after application. However, residues in the thatch remained sufficiently high for control of insects for up to 7 days after application for diazinon and 14 days for chlorpyrifos and isofenphos.     

Persistence of some organophosphorus insecticides in hen-house litter

Thin-layer chromatography was used to assess semi-quantitively the persistence of six organophosphorus insecticides in hen-house litter. Malathion disappeared within 4 h of application. Carbofenthion was the most persistent. Four weeks after treatment the proportions of the applied doses extracted from the litter were: carbofenthion 46%, phorate 21%, diazinon 13%, coumaphos 7% and fenitrothion 3%.     

Uptake of phorate by lettuce

Following experimental and commercial applications to soil of a granular formulalation of phorate (O,O-diethyl S-ethylthiomethyl phosphorodithioate), residues in the soil and in lettuce were determined by gas-liquid chromatography. When applied by the bow-wave method as a continuous logarithmically-changing dose ranging from approximately 0.9 to 16.0 kg a.i. ha^?1, the proportional rate of oxidation in soil of phorate sulphoxide to phorate sulphone was inversely related to dose. Ten weeks after application, total phorate residues in the soil had declined by about 35% at all dose levels. Residues in mature lettuce, from the 1-5 kg ha^?1 dose-range, comprised the parent and oxygen analogue sulphoxides and sulphones; the relative proportions of the individual metabolites were independent of dose. Over this dose-range, total residue concentrations in the crop became proportionally slightly greater with increasing dose. When single doses of 1.1, 2.0 or 2.2 kg a.i. ha^?1 were applied at drilling, the total residue concentrations in the lettuce declined from 5 mg kg^?1 in seedlings from some treatments to <0.05 mg kg^?1 at harvest. In plants raised in peat blocks containing 10 or 20 mg a.i. per block, however, residues in seedlings totalled 45-47 mg kg^?1 and declined to only 0.7 mg kg^?1 at harvest. It was concluded that bowwave applications of phorate when field-sowing lettuce were unlikely to lead to unacceptable residues in the harvested crop, but that residues in lettuce raised in phorate-treated peat blocks may be unacceptably high.     

Persistence of chlorfenvinphos in soils

The persistence and behaviour of chlorfenvinphos, an organophosphorus insecticide, was studied on different soils. On a peaty soil the insecticide was only very slowly degraded, there being 70% of the applied dose remaining after 21 weeks and 30% after nearly 12 months. On the sandy soils, however, persistence was much shorter; between 3 and 15% of the applied dose remained after a period of 15 weeks. Rates of loss appear to be related to soil moisture conditions; in dry seasons, although the initial rate of loss was high, subsequent rate of breakdown was slower than in wetter seasons. The results are discussed relative to the efficiency of the insecticide for controlling brassica root fly.     

Leaching of aldicarb and thiofanox,and their uptake in soils by sugarbeet plants

The leaching of aldicarb and thiofanox in soils (sandy loam, silt loam and sandy clay loam), and their uptake by sugarbeet plants were studied. Three irrigation levels were maintained: half, normal and double dose. The residues were determined as the sum of the insecticidal metabolites (parent compound + sulphoxide+ sulphone) for both pesticides. Leaching was greatly influenced by the amount of water added and the soil type. Under normal conditions, leaching seemed to proceed very slowly, keeping the chemicals available for uptake by the root systems for a long time. The concentration of insecticide in the leaves was highest in beets grown on sandy loam and lowest in those grown on sandy clay loam. The quantity of irrigation did not influence the residue concentration in the leaves greatly, although its influence was obvious on the total residue present (μg per plant). Increasing the water dose always resulted in a higher total residue, and a greater plant weight. The breakdown in the soils was directly related to the water dose. The experiments show that thiofanox was more stable than aldicarb and was taken up by sugarbeet to a greater extent.     

Persistence and movement of ethofumesate in soil*

Persistence of ethofumesate [(±)2-ethoxy-2.3-dihydro-3,3-dimethylbenzofuran-5-yl-methansulphonate] in soil was associated with soil temperature. Ethofumesate applied at 4.5 kg/ha in November persisted about twice as long in soil as that applied the following March. In another field study, 88–91% of the herbicide had dissipated after 24 weeks in sandy loam soil, compared to 72–77% in loam soil when it was applied at rates of 2.2, 3.4, 4.5, and 9.0 kg/ha. The rate of degradation was independent of the initial rate of chemical applied. The time required for 50% of the herbicide to dissipate in sandy loam and loam soils was 7.7 and 12.6 weeks, respectively. The movement of ethofumesate in these two soils over a 24-weeks sampling period was confined mainly to the upper 7.5 cm of the soil profile.     

The effect of the annual use of some pesticides on soil microorganisms,pesticide residues in soil and carrot yields

The study deals with the effect of common, annually-used pesticides on soil microorganisms, pesticide residues in soil, and carrot (Daucus carota) yields in Central Finland. Linuron residues in carrot roots were also analysed. Thiram+lindane and dimethoate were applied from 1973–1981 at the commercially recommended doses on experimental plots of carrots, linuron was applied at twice the recommended rate from 1973–1979 and at the normal rate thereafter and in addition TCA was applied in 1978. Maleic hydrazide was used in the years 1973–1976, and glyphosate after 1977. The numbers of different soil microorganisms, their activities and the pesticide residues were studied from autumn 1978 to 1981. The pesticide treatments reduced the growth of soil algae but increased the total number of microorganisms and the number of aerobic spore-forming bacteria. Linuron residues in the soil were 0.9–2.8 mg kg^?1 in the growing season and 1.2–1.7 mg kg^?1 in the autumn, 3 months after application. The residues of glyphosate in the soil were 0.7 mg kg^?1 in the autumn, 41 days after the treatment, and had declined to a level of about 0.2 mg kg^?1 by the following summer. In the pesticide-treated plots the carrot yield was only 20–60% of the yield in the hand-weeded plots. The herbicide programme controlled most of the annual weeds but not couchgrass Elymus repens and milk sow-thistle Sonchus arvensis.     

Conversion rates of aldicarb and its oxidation products in soils. I. Aldicarb sulphone

The rate of loss of aldicarb sulphone was studied in incubation experiments on soils from four plough layers and two deeper layers. In all instances the loss could be described by first-order kinetics in the first period of two to three times half-life. However, in a clay loam soil and a greenhouse soil a faster degradation rate was observed after the first 56 and 112 days of incubation respectively. The half-lives of sulphone in plough layer soils at 15°C ranged from 18 days in a clay loam to 154 days in a peaty sand. Conversion in deeper layers was considerably slower than in the corresponding top layers of the soil profile. In a silty layer at 70 to 90 cm depth the half-life at 15°C was 46 days, whereas in a sand layer at 90–110 cm no clear loss was found during the 294 days of incubation.     

Pesticide residues in fat of cattle treated with backrubbers impregnated with coumaphos,methoxychlor or DDT

Cattle were treated thrice weekly for 12 weeks with simulated backrubbers impregnated with 1% solutions of pesticides in mineral oils. Both coumaphos and methoxychlor applied in S.A.E. 50 oil induced maximum residues of 0–21 ppm in omental fat after 12 weeks treatment. Application of DDT in S.A.E. 50 oil or in used crankcase oil induced residues of 0·5–7 ppm DDT in omental fat after 12 weeks treatment. Where diesel fuel oil was the vehicle, DDT residues in omental fat were in the range 17–26ppm.