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.     

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.     

Build-up and subsequent decline of residues of quintozene and hexachlorobenzene in lettuce in sequential crops

The build-up and decline of quintozene and hexachlorobenzene residues in protected lettuce, resulting from one to five treatments of the soil (each of 35 g m-2) with a quintozene formulation, have been studied. Residue levels were monitored in each experimental crop during growth until harvest. Residues in the soil at harvest were also determined. Quintozene residues in the harvested lettuce were in the range < 0.02–0.80 mg kg^?1 and those of hexachlorobenzene were in the range < 0.02–0.05 mg kg^?1 (expressed on a fresh weight basis). Residue levels in the soil were 5.4–231 mg kg^?1 for quintozene, and 0.20–5.4 mg kg^?1 for hexachlorobenzene (expressed on a dry weight basis). Under the experimental conditions of the trial there was no significant build-up of quintozene or hexachlorobenzene in harvested lettuce, even after five treatments to the same site.     

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     

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.     

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.     

Factors affecting the activity of ethephon in stimulating seed germination of Striga hermonthica (Del.) Benth.

Ethephon (2-chloroethylphosphonic acid), which generates ethylene, stimulated the germination of pre-conditioned seeds of Striga hermonthica when it was added to the alkaline Gezira clay soil at concentrations of 2.5 to 30 mg kg^?1. As little as 5 min contact with treated soil was enough to stimulate germination. Ethephon in soil did not cause germination of unconditioned seeds for periods of up to 12 days and also had an adverse effect on seed germination when such seeds were given a second ethephon exposure after a storage period which was adequate, in untreated soil, to give the necessary pre-conditioning. Ethephon activity persisted in air-dry soil but declined over a 14 day period in moist soil. In the field ethephon at 0.6 to 4.8 kg ha^?1 decreased the number of Striga shoots and increased sorghum height and flowering.     

The HPLC determination of residues of maleic hydrazide in cloves of garlic bulbs following foliar application

A method was developed for the extraction and HPLC analysis of the plant growth regulator maleic hydrazide (MH) from garlic bulbs. Recovery of MH from fortified garlic tissue was 75.8(±6.1)% at the 1 and 2 mg kg^?1 fortification levels. MH residues were determined by HPLC in cloves of garlic bulbs following treatment at three sites in southern Ontario with foliar applications at 3.75 kg ha^?1. MH residues in the cloves were in the order of 3 mg kg^?1 at two sites, and 11 mg kg^?1 at the third side.     

Residues of Mecoprop in Post-emergence-Treated Wheat and Oat

The dissipation of mecoprop in wheat (Triticum aestivum L.) and oat (Avena sativa L.) was monitored over a growing season following post-emergence application of the dimethylamine salt of mecoprop to each crop at 1·1 kg ha^?1. Residues of mecoprop, as its methyl ester, were determined gas chromatographically using electrolytic conductivity detection. Initial residues in wheat (119 (±20) mg kg^?1) and oat (95·3 (± 10·0) mg kg^?1) on the day of application (four-leaf stage of wheat and four- to five-leaf stage of oat) decreased to 0·1 to 0·2 mg kg^?1, respectively, within six weeks. Residues were non-detectable in the mature seed of both crops. Recoveries of mecoprop were in the order of 90% from the green tissue and seed of both crops fortified at 0·05 mg kg^?1.     

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.     

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.     

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.     

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.     

The determination of the herbicide dinoseb in lentils

Residues of the herbicide dinoseb were determined gas chromatographically in lentils which had been treated at two locations in Saskatchewan with post-emergence applications of dinoseb at 1.4 and 1.7 kg ha^?1. Herbicide residues, determined at selected times after application, were not detected at the limit of detection of the analytical method (0.05 mg kg^?1) in either the seed and straw at maturity, or in the green foliage six to eight weeks after application. Recoveries of dinoseb were 76% from fortified green foliage at the 0.1 mg kg^?1 level, and 64% from fortified seed at the 0.05 mg kg^?1 level.     

Movement and persistence of imazaquin, oxyfluorfen, flurochloridone and terbacil in soil

The movement and persistence of imazaquin, oxyfluorfen, flurochloridone and terbacil residues were studied using a bioassay based on the shoot growth of Raphanus sativus L. var, radicula DC (radish) in a sandy loam soil under field conditions in 1992 and 1993. Imazaquin (0.3 kg a.i. ha^-1) was more mobile in the soil than the other three compounds. In 1992, under heavy rainfall conditions, the herbicide was distributed down to 60 cm in amounts of about 0.01 mg kg^-1. Conversely, in the dry year of 1993, the maximum depth of penetration was 20 cm and persistence in the surface soil layer (0-5 cm) was greater. After the first month in 1992, residues of terbacil were distributed in the 0-20 cm layer, and after 2, 3 and 5 months the herbicide had penetrated to a depth of 40 cm. In 1993, terbacil residues were distributed in the 0-10 cm layer only. In both years, residues of flurochloridone (1.0 kg a.i. ha^-1) were located mainly in the 0-5 cm layer, but there was some penetration to 10 cm. Oxy-fluorfen (1.2 kg a.i, ha^-1) showed least mobility in the soil profile. It was retained in the 0-5 cm layer throughout the experimental period in both. years.     

Persistence of carbendazim in field-grown soybeans following application of thiophanate-methyl fungicide

Carbendazim was quantified spectrophotometrically in leaves, petioles, stems and pods from upper and lower halves of entire soybean plants following one or two foliar applications of thiophanate-methyl fungicide (1.1 kg ha^?1 a.i.). Following the first application, the highest carbendazim concentrations occurred 1-4 days post-application and declined thereafter to undetectable (?0.12 mg kg^?1) or barely detectable levels by day 26. The highest concentrations were in the leaves where carbendazim levels exceeded 3.5 mg kg^?1 on day 4 and remained above 1.0 mg kg^?1 until day 19. Concentrations in petioles and upper pods were initially in excess of 1.0 mg kg^?1 and remained above 0.5 mg kg^?1 for 12 days. In lower pods and in stems, concentrations were very low and often not detectable. Typically, concentrations were higher in samples from the upper half of the plant than in those from the lower half. A second application on day 18 resulted in carbendazim concentrations similar to those immediately after the first application; however, concentrations declined rapidly coincidentally with a period of rain. This decline may have been facilitated by poor fungicide uptake due to senescence of the plants.     

Tolerance of spring wheat (Triticum aestivum L.) to trifluralin deep-incorporated in the autumn or spring

Field experiments at Lacombe on a Ponoka loam soil (9·6% organic matter) during 1982 and 1983 investigated the tolerance of spring wheat (Triticum aestivum L.) cv. Neepawa in a weed free situation to trifluralin applied at 0·0–3·0 kg ai ha^?1 in the autumn or spring and incorporated to a depth of 10 cm. Rates of trifluralin above 1·0 kg ai ha^?1 applied in the autumn or spring reduced the percent stand of wheat compared to an untreated control. Two weeks after emergence the crop showed 37 or 47% injury indicated by delayed growth, following application at 1·0 kg ai ha^?1 in the autumn or spring, respectively. The wheat recovered throughout the course of the growing season. At harvest, trifluralin applied in the autumn or spring at rates below 1·0 kg ai ha^?1 caused a yield increase while higher rates caused a yield decrease compared to the untreated control. Spring application caused a greater yield loss than autumn application. The tolerance of spring wheat to trifluralin at rates required for weed control (1·1 kg ai ha^?1 or higher) on this soil type is marginal.     

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.     

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.