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.     

Behaviour of trifloxystrobin and tebuconazole on grapes under semi‐arid tropical climatic conditions

BACKGROUND: A mixture of trifloxystrobin and tebuconazole is excellent in controlling both powdery and downy mildew of grapes. The objective of the present work was to study the behaviour of trifloxystrobin and tebuconazole on grape berries and soil following treatment with Nativo 75 WG, a formulation containing both fungicides (trifloxystrobin 250 + tebuconazole 500 g kg^?1). This study was carried out for planned registration of this mixture for use on grapes in India. RESULTS: Initial residue deposits of trifloxystrobin and tebuconazole on grapes were below their maximum residue limit (MRL) of 0.5 and 2 mg kg^?1, respectively, when Nativo 75 WG was applied at the recommended dose of 175 g product ha^?1. The residues dissipated gradually to 0.02 and 0.05 mg kg^?1 by 30 days, and were below the quantifiable limit of 0.01 mg kg^?1 at the time of harvest (60 days after the last treatment). Trifloxystrobin and tebuconazole dissipated at a pre‐harvest interval (PHI) of 36 and 34 days, respectively, from the recommended treatment dose. The acid metabolite of trifloxystrobin, CGA 321 113, was not detected in grape berries at any point in time. Soil at harvest was free of any pesticide residues. CONCLUSION: Residue levels of both trifloxystrobin and tebuconazole were below MRLs when grapes were harvested 30 days after the last of four applications of 175 g product ha^?1 (trifloxystrobin 44 g AI ha^?1, tebuconazole 88 g AI ha^?1) under the semi‐arid tropical climatic conditions of India. Copyright © 2010 Society of Chemical Industry     

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.     

Permethrin and deltamethrin residues on lettuce

Permethrin and deltamethrin, two synthetic pyrethroid insecticides, are registered in several countries for use on lettuce. Both chemicals were applied on autumn and spring grown lettuce in the glasshouse. When applied at the normal prescribed dose rates of 25 and 12.5 g a.i. ha^?1, < 1 mg kg^?1 of either compound was found in the lettuce at harvest, even when applied only a few days before harvest. The total amount of active ingredient applied was too low to reach the 1 mg kg^?1 level when evenly applied on marketable lettuce heads weighing about 200 g each. Applying a higher dose than 25 g permethrin a.i. ha^?1 or 12.5 g deltamethrin a.i. ha^?1, or applying two applications in the 2 weeks prior to harvest, may well result in residue levels higher than the maximum residue limit of 1 mg kg^?1 for permethrin and certainly higher than the maximum residue limit of 0.2 mg kg^?1 for deltamethrin, which is more persistent.     

The behaviour of residues of flamprop-isopropyl and its breakdown products in barley

Residue data are reported for flamprop-isopropyl ( I ) in barley grain and straw samples following applications of the herbicide to crops grown in eight countries. The samples were analysed for I and its hydrolysis product N-benzoyl-N-(3-chloro-4-fluorophenyl)-DL -alanine ( II ). Following recommended applications (normally 1 kg ha^?1 at Feekes scale G-I/J), residues of I and II in the grain were low (90% were <0.02 mg kg^?1 for I , 86% were <0.06 mg kg^?1 for II , levels which were essentially the limits of determination). Residues in straw were higher and more variable, but again 63 and 77% of samples were below 1 mg kg^?1 for I and II , respectively.     

Disappearance of carbosulfan residues in peaches

The disappearance kinetics of the carbamate insecticide, carbosulfan, applied at 2 kg AI ha^?1 (‘Marshal’ 250 g litre^?1 EC) in peaches was studied. Degradation took place in two consecutive stages (0–28 and 28–57 days), with half-lives of 7.4 and 17.5 days, respectively. The residues obtained 57 days after treatment did not exceed 0.2 mg kg^?1. When treatments were carried out 30, 21 and 14 days before the probable date of harvest (date of fruit maturation) with two doses (1.0 and 2.0 g formulated product litre^?1) and two volumes applied (750 and 1500 litre ha^?1), the residual levels detected were between 0.122 mg kg^?1 (30 days before harvest) and 0.4 mg kg^?1 (14 days before harvest). The major metabolite, carbofuran, was never detected above its determination limit of 0.004 mg kg^?1 throughout the whole study.     

Residues in blackcurrants,fodder peas,spinach and potatoes treated with sublethal doses of 2,4,5-T to simulate wind drift damage

Blackcurrants, treated with 0.1 kg of 2,4,5-T ha^?1 (as esters of mixed C₄–C₆ alcohols; ‘Tormona 80’), contained 0.1 mg of 2,4,5-T residues kg^?1 in the berries at ripeness 29 days after treatment. Total residues in the berries were not reduced during growth and ripening, although the residue concentrations declined in the same period due to growth dilution. In spinach leaves from old plants, treated with 0.1 kg ha^?1, 0.05 mg of 2,4,5-T kg^?1 was found 14 days after treatment. Fodder peas showed no residues (< 0.002 mg kg^?1) at harvest 62 days after treatment with 2,4,5-T esters. After application of 0.1 kg ha^?1 on potato plants, the disappearance of 2,4,5-T was rapid during the first month, but residues were translocated into the tubers and reached a constant level of 0.02 mg kg^?1 after 1 month until harvest at 108 days after treatment. In all crops, visible effects were observed after treatment with 0.1 kg ha^?1. After the application at 0.01 kg ha^?1, phytotoxic effects were observed only in blackcurrants, but negligible residues were found in all the test crops.     

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.     

Fenbutatin oxide,fate in soil after extensive commercial use in Italy and Spain

The long-term fate of the acaricide, fenbutatin oxide, in soil has been investigated. Residues of the compound and its two principal metabolites have been determined in soil samples obtained from citrus orchards in Italy and Spain where the product had been applied commercially over a period of 6–10 years. The average fenbutatin oxide content in the upper 0–15 cm soil layer ranged from ? 1 mg kg^?1 to 5 mg kg^?1 in sites receiving single and double applications per year. The residues were located primarily (> 95%) in the top 0–30 cm layer and there was virtually no movement of the compound through the soil to lower depths. Below 0.5 m depths, the sites contained average concentrations of ? 0.01 mg kg^?1, the limit of determination. No significant build-up of residues was observed and the data indicate an approximate half-life in soil of just less than one year. Residues of the two metabolites, dihydroxy-bis(2-methyl-2-phenylpropyl)stan-nane and 2-methyl-2-phenylpropyl stannonic acid, were on average 11% and 16% of the fenbutatin oxide concentration, respectively. As with fenbutatin oxide, there was no significant movement through the soil to lower levels.     

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.     

Grain protectants for the control of malathion-resistant insects in stored sorghum

Duplicate experiments were carried out on bulk sorghum stored in South Queensland and in Central Queensland. Bioassays of treated grain, conducted during 6 months' storage, established that fenitrothion (12 mg kg^?1)+ bioresmethrin (1 mg kg^?1), and pirimiphos-methyl (4 mg kg^?1)+ carbaryl (8 mg kg^?1), controlled typical malathionresistant strains of Sitophilus oryzae (L.), Rhyzopertha dominica (F.), Tribolium castaneum (Herbst), and Ephestia cautella (Walker). Chlorpyrifos-methyl (10 mg kg^?1)+ pyrethrins (1.5 mg kg^?1)+ piperonyl butoxide (12 mg kg^?1), and fenitrothion (12 mg kg^?1)+ (1R)-phenothrin (1 mg kg^?1), also controlled the strains of S. oryzae, T. castaneum and E. cautella, but were only partly effective against R. dominica. Methacrifos (15 mg kg^?1) controlled all the tested species except E. cautella. Chemical assays established that the residues and rates of breakdown of these grain protectants on sorghum conformed to the general pattern for other cereal grains; residues from the above treatments were below the individual Maximum Residue Limits recommended by the Codex Alimentarius Commission.     

Accumulation of endosulfan residues in fish and their predators after aerial spraying for the control of tsetse fly in Botswana

Residues of endosulfan insecticide (α- and β-isomers, and ‘endosulfan sulphate’) in fish and their predators were measured during and after operations to control tsetse fly in the Okavango Delta, Botswana. Six ultra-low-volume doses of endosulfan 35% e.c. (6–12 g a.i. ha^?1) were applied from the air in a period of 12 weeks over 2500 km². The concentration of residues found in living fish was up to 0.19 mg kg^?1 wet wt in caudal muscle, and usually < 0.8 mg kg^?1 wet wt in pooled viscera (maximum 2.8 mg kg^?1). These values returned to near-normal within 3 months after cessation of spraying, but residues were still detectable after 12 months. By comparison, fish killed by spraying contained a maximum residue level (whole-body) of 1.5 mg kg^?1 wet wt. The residue level in fish was approximately proportional to their fat content. Lean fish were more susceptible to poisoning than fat fish. The proportion of the ‘endosulfan sulphate’ metabolite in fish increased at least six times with respect to the parent isomers (α+β) during the period of spraying, but more advanced stages of metabolic breakdown were not monitored. Residue levels in fish predators (fish-eating birds and crocodiles) were similar to those in their prey, and the risk to them was consequently low.     

Organophosphorus insecticide residues in virgin Greek olive oil, 1988–1990

Organophosphorus insecticide residues have been monitored for two years in virgin olive oil after dimethoate and fenthion treatments to control the olive fruit fly. No dimethoate residues were detected in any of the samples. For the first and second years, 50% and 21%, respectively, of the samples contained no detectable fenthion residues, while 4% and 6%, respectively had residue concentrations exceeding the Codex Alimentarious Maximum Residue Limit (1 mg kg^?1). The mean concentration was 0·236 mg kg^?1 oil and the estimated daily intake of fenthion 0·0002 mg kg^?1 body weight (Acceptable Daily Intake 0·001 mg kg^?1 body weight). The parent compound was the most important residue in fresh samples, while aged samples contained a higher amount of the metabolite fenthion sulfoxide. The contribution of the oxygen analogues (P= 0 metabolites) of fenthion to the total residue concentration was<5% in most cases.     

Pesticide residues in foodstuffs in England and Wales. Part I: Inorganic bromide ion in lettuce grown in soil fumigated with bromomethane

Surveys of lettuce, produced commercially in England and Wales, were carried out during the years 1977–82 to determine residues of inorganic bromide ion, following soil sterilisation with bromomethane. Lettuce grown on unfumigated soil contained less than 10 mg bromide ion kg⁻¹, while most lettuce grown on bromomethane-fumigated soil were found to contain higher levels of bromide ion, with a proportion in excess of 1000 mg kg⁻¹. The accumulation of bromide ion appeared to be related to the interval between soil fumigation and planting, and also to the frequency of bromomethane application to the soil. A limited amount of data is presented on the levels of bromide ion in imported lettuce.     

Determination of residues of endosulfan and endosulfan sulfate on eggplant,mustard and chickpea

Extractable residues of endosulfan stereoisomers and its toxic metabolite, endosulfan sulfate, on a vegetable, an oilseed and a pulse crop were determined by gas-liquid chromatography. The study revealed that the alpha isomer degraded faster than the beta isomer. Beta-endosulfan accumulated during the first three days following the treatment. Endosulfan sulfate residues appeared a few days after application and decreased with time. The total endosulfan residues in the seeds from treated mustard ranged from 0.08 to 0.12 mg kg^?1 and were at or below the limit of determination (0.02 mg kg^?1) in chickpea seeds following harvest.     

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

A study has been made of the influence of pesticides used annually on soil microorganisms and crop yields. The persistence of these pesticides in the soil was also investigated. The herbicides MCPA, glyphosate, maleic hydrazide and tri-allate, and the insecticide parathion, were applied on experimental plots on which barley was grown during the years 1973-1981. The fungicide 2-methoxyethylmercury chloride was used every year for dressing the seeds grown in pesticide-treated plots. The pesticide treatments did not affect significantly the numbers of several groups of soil microorganisms. A slight increase was, however, observed in the nitrification activity in the soil. The barley yields were on average higher on pesticide-treated plots than on controls because of successful weed control. Pesticide residues in the soil were generally very low; for example, for parathion they were below 0.02 mg kg^?1 within 11 days, and for MCPA 0.06 mg kg^?1 within 7 days. However, the glyphosate residue was 1.6 mg kg^?1 in the autumn 2 days after the treatment, and the residue settled to a level of 0.2 mg kg^?1 during the following summer. No clear dependence was observed between the residue level and the time between treatment and sampling.     

Residues of synthetic pyrethroid insecticides on horticultural crops

Foliar applications of synthetic pyrethroids were made to several crops to determine residue levels at various intervals after application. On onions, residues of cypermethrin, permethrin and fenvalerate were negligible > 0.1 mg kg^?1, 7 days after application. On lettuce, residues of fenvalerate and permethrin were 0.8 mg kg^?1. On celery, residues of fenvalerate did not decline and ranged from 0.12 to 0.25 mg kg^?1 during the 14-day period. On green bush-beans, residues of permethrin and cypermethrin did not decline during the 14-day period and ranged from 0.1 to 0.6 mg kg^?1. By day 7, residues of cyfluthrin, cypermethrin, deltamethrin, fenvalerate and permethrin on strawberries were less than the acceptable maximum tolerance of 0.1 mg kg^?1 with the exception of cypermethrin, applied at the rate of 0.14 kg a.i. ha^?1 which gave a residue of 0.14 mg kg^?1.     

The behaviour of residues of benzoylprop-ethyl and its breakdown products in wheat

Samples of wheat grain and straw have been analysed from trials with the wild oat herbicide benzoylprop-ethyl ( I ) in several countries. Following recommended commercial treatments (application of 1.0–1.6 kg ha^?1 at Feekes growth stage G-J), total residues of I and its hydrolysis product N-benzoyl-N-(3,4-dichlorophenyl)-DL - alanine (free and conjugated) were low and in the majority of instances they were < 0.01 mg kg^?1 in samples of grain from the UK, although rather higher residues were detected in some grain samples from other countries. Residues in straw were higher, but normally did not exceed 2 mg kg^?1, and were rather variable, possibly as a result of differences in agricultural practice.     

Further studies of the deposition and persistence of binapacryl,bupirimate and diflubenzuron on apple foliage and fruit

In an extension of previous work, deposits and residues of binapacryl, bupirimate and diflubenzuron on mature foliage and the peel of developing fruit of Worcester and Cox apple trees were monitored throughout the 1980 season following applications by mistblower sprayer. The three compounds were applied as commercial formulations in trials to compare integrated pest management with routine farm spray programmes. In contrast to previous results, all three compounds persisted on foliage until leaf-fall and were detected on the peel of harvested fruit. The mean residue of diflubenzuron on harvested Worcester fruit was 0.05 mg kg^?1 fresh weight and on harvested Cox fruit was 0.02 mg kg^?1 fresh weight. Binapacryl and bupirimate were present on harvested fruit of both cultivars. The unexpectedly long persistence of these chemicals in 1980 remains unexplained, but may be due to climatic factors.     

Residues of the algicide endothal in water,soil and rice,after paddy field applications

In order to obtain residue data from the application of the algicide endothal in Italian rice paddy fields, two experiments were carried out using a 50 g kg^?1 granular formulation in a small pond and the same granular and two liquid formulations in actual paddy fields of the Italian rice growing area. Endothal decay in the pond water was very rapid, reaching residue levels of 0·01-1·02 mg litre^?1 in two days and 0·004-0·01 mg litre^?1 at the third day. The muddy soil of the pond was free from measurable endothal residues( <0·02 mg kg^?1). In the paddy-field waters, the endothal decay was slower, with an average half-life time of 3·3 days, independently of the type of formulation. The actual residues in water after 6 days ranged from 0·3 to 1·3 mg litre^?1 according to the initial amount of product applied, and, consequently, to the initial concentration in water. Rice samples collected at the normal harvest time from the two paddy fields, treated with three different formulations, showed no endothal residue at the minimum detectable level of 0·01 mg kg^?1.