Dimethoate Residues Research Articles

Genetic improvement of Amblyseius finlandicus (Acari: Phytoseiidae): laboratory selection for resistance to azinphosmethyl and dimethoate

Amblyseius finlandicus (Oudemans) was selected in the laboratory for resistance to azinphosmethyl and dimethoate by subjecting adult females to increasing concentrations of dried residues of dimethoate and azinphosmethyl on detached bean leaves. The first eight selections were done with dimethoate. Slide-dip bioassays indicated selection with dimethoate increased dimethoate resistance 1.8-fold and azinphosmethyl resistance 2.6-fold. These resistances appeared to be quite stable: a 1.2 to 1.3-fold decrease in resistance ratios was observed in a subculture after 10 months without selections. No decrease was observed after 9 months without selections in a pooled colony that consisted of both resistant and susceptible mites. The dimethoate-selected colony was subsequently selected eight times with azinphosmethyl. About 15 % of the mites survived the last selection round with 2,500 ppm, which is 2.5 times the highest recommended field rate in Finnish apple orchards. At the end of the selection program, based on slide-dip bioassays, the total increase in resistance to dimethoate was about two-fold and to azinphosmethyl about 5.4-fold compared to the unselected base colony from which the selected colony was derived. The LC50 value for azinphosmethyl was 14 times higher in the selected colony (451.3 ppm a.i.) compared to the most susceptible colony tested. A similar level of resistance to both pesticides was achieved after six azinphosmethyl selections on a mixed colony that was initiated by pooling mites from five field-collected colonies and the dimethoate-selected lines. Year-to-year variation in azinphosmethyl LC50 values of the unselected base colony was high, with values varying from 83.8 to 348.7 ppm a.i., demonstrating the need to test a reference strain in each bioassay. Results of the azinphosmethyl selections and the subsequent slide-dip bioassays suggest that the resistant strain could tolerate field rates of azinphosmethyl (300–950 ppm a.i.) used in Finnish apple orchards.

Organophosphorus insecticide residues in farm ditches of the Lower Fraser Valley of British Columbia

Abstract Farm ditches flowing into three important rivers in the Lower Fraser Valley of British Columbia, Canada, were sampled periodically at seven locations from July to December in 1991, to determine the occurrence and levels of seven organophosphorus (OP) insecticides. Based oh sales records for the year, the uses of OP insecticides in this area were as follows: malathion > diazinon > parathion > dimethoate > azinphos‐methyl > fensulfothion, but no sales of chlorfenvinphos. Residues of parathion, diazinon, fensulfothion, dimethoate and chlorfenvinphos were detected at levels ranging from 1 ‐ 7,785 >μg/kg in cropped soils collected from areas adjacent to the sites for sampling ditch water and sediments. Malathion and azinphos‐methyl were not detected in any of the substrates studied, demonstrating their rapid degradation in the environment. Diazinon and dimethoate were consistently found in ditch water at seven locations, with an average concentration of 0.07 μg/L and 0.27 μg/L, respectively. Fensulfothion and parathion, with an average concentration of 0.08 μg/L and 0.17 μg/L, respectively, were sporadically found in ditch water at two locations. In ditch sediments, diazinon was detected at three locations and fensulfothion at two. The average concentrations of these two insecticides were 16 μg/kg and 9 jug/kg, respectively. The potential impact on aquatic organisms of these OP insecticides in ditches is discussed.

Residual Toxicity of Five Citrus Pesticides to a Carbaryl-Resistant and a Wild Strain of the California Red Scale Parasite Aphytis melinus DeBach (Hymenoptera: Aphelinidae)

Leaf-residue and plastic cup bioassays were done with a carbaryl-resistant (R) and two susceptible (S) (Base and La Couague) colonies of Aphytis melinus DeBach. Tolerances to carbaryl, methidathion, chlorpyrifos, dimethoate, and formetanate were compared among the two 5 colonies and the laboratory-selected R strain. Two-leaf bioassays done during 1989 indicated that the R strain survived Significantly better than the Base colony on both carbaryl- and chlorpyrifos-treated leaves. The R strain survived better than both 5 colonies on all pesticides tested with a single concentration in the cup bioassay. Results of bioassays done during 1990 connfirmed that the R strain survived better than the La Couague colony on carbaryl, methidathion, dimethoate, and formetanate leaf residues. In the 1990 leaf residue tests, chlorpyrifos residues were more toxic to the R strain. Practical aspects of releasing the R strain in California citrus orchards are discussed.

Metabolism and excretion of dimethoate following ingestion of overtolerance peas and a bolus dose

Data to guide an exposure assessment were obtained by giving sugar peas containing overtolerance dimethoate residues (17 ppm; 8% oxon) and a bolus dose of dimethoate to a healthy adult male. The dimethoate tolerance on peas was and remains 2 ppm. Serial total urine samples were collected and analysed for dimethoate and its oxon, dimethylphosphate, dimethylphosphorothioate (DMTP) and dimethylphosphorodithioate. The dose of dimethoate administered was approx. 0.1 mg/kg body weight and produced no symptoms of toxicity. Dimethylphosphates appeared in the urine within 2 hr. The major metabolite (about 60%) was DMTP. Only traces (<0.5%) of dimethoate and oxon were recovered from urine. Acetylcholinesterase inhibition was not observed although urinary metabolites were prominent, indicating that they are better indicators of acute exposure than cholinesterase inhibition. The results obtained using a bolus dose were virtually identical to those from the trial with overtolerance peas, and indicated that dimethoate is readily absorbed and its urinary metabolites are readily eliminated following exposures to low doses (0.1 mg/kg body weight).

HONEY BEE (APIS MELLIFERA L.) DEATHS NEAR SPRAYED COTTON AND OBSERVATIONS ON BEE FORAGING BEHAVIOUR IN FLOWERING COTTON (HYMENOPTERA: APIDAE)

Trials were conducted to investigate the attractiveness of cotton to honey bees (Apis mellifera L.), and bee mortality resulting from insecticide applications to cotton near Emerald, central Queensland. Bees died at hives sited within 3 km of sprayed, flowering cotton on two occasions. Methyl-parathion was identified in dead bees and in pollen taken from hives on one occasion. Dimethoate residues were detected in dead bees at the same site after application of this chemical to cotton. Bee foraging in areas exposed to spraying was implicated as leading to the mortality, rather than drift to the hive site, as two of the five hives did not have increased deaths on either occasion. Bees were shown to collect nectar and pollen from cotton flowers. Numbers peaked at an average of 17.5 bees per 100 m of crop row in February on an unsprayed trial in southeastern Queensland.

Gas Chromatographic Determination of Dimethoate Residues in Chrysanthemums and Soil

Abstract A gas chromatographic (GC) method was developed for determination of dimethoate residues In chrysanthemums and soil. Dry flowers, fresh flowers, and leaves of chrysanthemum and soil samples are extracted with acetone, cleaned up by coagulation, and partitioned with dlchloromethane. Dimethoate is determined by GC with nitrogenphosphorus detection. Recovery ranges of dimethoate from samples of dry flowers, fresh flowers, and leaves of chrysanthemums are 86.7-91.0% (fortified at 0.5-2.0 ppm), 88.1-93.6% (fortified at 0.036- 0.721 ppm), and 83.3-96.9% (fortified at 0.5-1.31 ppm), respectively. Recovery ranges of dimethoate from soil samples are 93.0-104% (fortified at 0.125- 0.327 ppm). Average recoveries of the 4 kinds of samples (n = 9) are 88.4 ± 8.94%, 91.5 ± 4.18%, 91.1 ± 4.69%, and 97.3 ± 5.1 %, respectively

Postharvest quarantine disinfestation of zucchinis and rockmelons against Bactrocera cucumis (French) using insecticide dips of fenthion or dimethoate

The disinfestation efficacy of a 1-min dip in fenthion or dimethoate (400 mg/L in water) was tested against eggs and larvae of the cucumber fly, Bactrocera cucumis, in zucchinis and rockmelons. Each trial involved &gt;30 000 individuals. Fenthion gave 100% mortality of eggs and third instar instar larvae in rockmelons, 100% mortality of eggs in zucchinis, and &gt;99.99% mortality of third instar larvae in zucchinis. Dimethoate gave 100% mortality of eggs in zucchinis, &gt;99.98% mortality of third instar larvae in zucchinis, and &gt;99.99% mortality of eggs and larvae in rockmelons. Residues of fenthion and dimethoate in zucchinis or rockmelons were below the Australian maximum residue limit of 2 mg/kg on the day of treatment. There were no adverse effects on taste.

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

AbstractOrganophosphorus 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&lt;5% in most cases.

Residues of dimethioate and methomyl on tomato and cabbage in relation to their effect on quality-related properties

Dimethoate EC 40% and methomyl 90% WSP were applied under field conditions to follow up the decline of their residues on tomato and cabbage plants. The results indicate that the level of dimethoate and methomyl residues were found to be below tolerance level after 7 and 3 d from application, respectively. Dimethoate and methomyl residues also had significant effects on ascorbic acid contents in tomato fruits after 1 and 7 d for dimethoate, while the effect was after 3 and 10 d for methomyl. Dimethoate also showed significant effects on total soluble solids in tomato fruits presented until 14 d after pesticide application. Both dimethoate and methomyl had significant effect on both iron and magnesium content in tomato fruits and leaves and cabbage leaves during the 14 d.

Residues of dimethoate and omethoate in peaches and apples following repeated applications of dimethoate

Etude de la persistance de cet insecticide dans les fruits en relation avec les delais entre le traitement des arbres et la recolte des fruits. Comparaison des resultats obtenus avec les teneurs limites imposees par la reglementation portugaise

Dimethoate and fenthion as packing line treatments for tomatoes against Dacus tryoni (Froggatt)

Tomatoes were disinfested of Queensland fruit fly (Dacus tryoni) by using dimethoate or fenthion applied as sprays during grading and packing. Concentrations of 400 mg/L of either insecticide applied through a high-volume recirculatory flood system delivering 16 L/min.m2 were used to treat fruit moving at a speed of 0.5 m/min, on conveyor brushes, so that fruit was flooded for 10 s and remained fully wetted for a further 1 min. Treatment efficacies of 100% against 30 000 eggs and 30 000 larvae were obtained. The treatments were equally effective when used in conjunction with post-treatment cooling to 12.5�C for 1 week. No tainting problems were detected. Residues of dimethoate (also omethoate for selected samples) and fenthion in treated fruit were found to be less than the Australian Maximum Residue Limits for tomatoes at all times; methods for determination of fenthion and omethoate residues are described. These disinfestation treatments have advantages of automation and efficiency compared with previously proven dip treatments.

Persistence and toxicity of dimethoate on wheat herbage and sweetclover herbage

Abstract Dimethoate was applied at 35, 70, 125, 250, and 500 g/ha to sweetclover and the herbage collected for chemical analysis at 0.2 hours and 1, 3, and 5 days after application. Residues of dimethoate decreased quickly with time with 20% or less remaining after 5 days. Dimethoate was applied (420 g/ha) to wheat and the herbage was collected at 0.2, 2, 5, 12, 18, 24, 48, and 72 hours after application for both chemical and biological analysis. Chemical analysis of the wheat herbage indicated a 65 to 85% loss of dimethoate in the first 24 hours after spraying. Mortality of 2nd and 3rd instar nymphs of Melanoplus sanquinipes (Fabr.) eating the sprayed herbage decreased from an average of 55% to 19% in the same time period.

Honey Bee (Hymenoptera: Apidae) Foraging During Bloom in Dimethoate-treated Apple Orchards

Honey bee ( Apis mellifera L.) reactions to dimethoate (Cygon 400) residues were evaluated following apple grower reports of decreased foraging activity and fruit set subsequent to prebloom dimethoate applications. Data collected in 1981 and 1982 in Adams County, Pa., indicated no reduction of foraging on trees treated 2–18 days earlier with dimethoate at recommended rates (562 g [AI]/ha). No excessive bee mortality was found during the tests, nor was fruit set affected by the prebloom sprays. Selective, small-scale applications made during bloom significantly shortened the duration of foraging trips and decreased the number of flowers visited on treated trees by individual foragers. A testing method using apple branch bouquets, pruned from trees, was devised to measure bee visitation on a per-flower basis. Significantly lower visitation occurred to dimethoate-sprayed bouquets at 2 days after treatment, but not at 3 days after spraying. When blooming bouquets were sprayed in the morning with either a field-rate (as above) or an exaggerated (triple concentration) dimethoate treatment, flowers typically received fewer bee visits throughout that test day.

Analysis and dissipation of dislodgable residues of acephate, dimethoate and formetanate hydrochloride on citrus foliage

AbstractDislodgable residues of acephate and its hydrolysis product methamidophos, dimethoate and its oxygen analogue omethoate (dimethoxon), and formetanate hydrochloride on citrus foliage were determined by gas–liquid chromatography. The use of 5% OV‐101 coated on a Carbowax 20M surface‐modified support (Ultra‐Bond 20M) allowed the reproducible analysis of dimethoate and omethoate residues. Formetanate hydrochloride residues were analysed as the free base, without preparation of a derivative, on a column packed with 5% Apiezon N coated on 80–100 mesh Ultra‐Bond 20M. The dissipation of the residues of the three pesticides applied to citrus trees was studied. Acephate and formetanate hydrochloride dissipation curves followed first‐order kinetics; dimethoate residues were best characterised by two first‐order kinetic processes. The half‐life values were 8.2 days for acephate, undeterminably long for formetanate hydrochloride, and 2.2 days (the 1–10 days portion) and 7.0 days (the 10–49 days portion) for dimethoate.

Dimethoate spray residues in strawberries

AbstractStrawberries were sprayed with solutions of 200, 300 and 500 mg dimethoate litre−1 and analysed for dimethoate residues up to 21 days after the final spraying. The residues were found to be below the National Health and Medical Research Council limit of 2 mg kg−1, 1, 2 and 4 days after spraying. Consequently, the withholding period of 7 days could be reduced to 3 days to allow uninterrupted picking of the ripe strawberry crop.

Effects of Dimethoate on Honey Bees (Hymenoptera: Apidae) When Applied to Flowering Lemons

Honey bee, Apis mellifera L., visitation to lemon, Citrus limon (L.) Burm. f., flowers nearly ceased after lemon groves were treated with dimethoate. Bee visitation remained low for 2 weeks after treatment. Colonies placed in a treated orchard the day after treatment lost more than 1,000 bees the first day; losses greater than normal continued for 1 week. Colonies brought in up to 2 weeks later also had more than normal mortality during a 2- or 3-day period after they were exposed to the dimethoate-treated lemon trees. Nectar removed from flowers had dimethoate residues greater than 0.1 ppm for up to 8 days after treatment. Nectar shaken from combs had maximum dimethoate residues of 0.1 ppm. Honey from exposed colonies had no detectable residues.

Dimethoate dipping of tomatoes against Queensland fruit fly, Dacus tryoni (Froggatt)

Dipping of tomatoes for 3 min. in a solution of dimethoate of 425 mg/litre strength was shown to be effective against infestations of Queensland fruit fly. An efficacy standard of no survivors in 30 000 individuals treated was achieved; dimethoate residues were below the relevant maximum residue limit of 1 mg/kg, and no taint was produced in green or ripe fruit.

Residues of Commercially Used Insecticides in the Environment of Megachile rotundata12

Residues of demeton, aldicarb, trichlorfon, dimethoate, and carbofuran (and their toxic metabolites) were determined in alfalfa leaf, pollen, and nectar, and in the pollen-nectarball and leaf from the reproductive cell ofMegachile rotundata F. The exposure of larvae to insecticide residue in the pollen-nectar ball from the bee cell averaged 17.6 ng of total insecticide for demeton, 0.4 ng of total insecticide for aldicarb, 148 ng for trichlorfon, and essentially 0 ng for dimethoate and carbofuran. The data showed no adverse effects on larvae by any of the residue found in various insecticide investigated.

Determination of dimethoate residue in some vegetables and cotton plants.

Determination of dimethoate residue in some vegetables and cotton plants.

Quantitative Confirmation of Dimethoate Residues in Wheat Plants by Single Ion Mass Spectrometry

A gas chromatographic-single ion mass spectrometric method was developed for determining dimethoate residues in wheat plants. The base peak (m/e 37) of dimethoate was chosen as the single ion peak, and methyl stearate was used as an internal standard for this analysis. The minimum detectable concentration of dimethoate by this method was about 0.1 ppm for a 20 g wheat plant sample. The recoveries of dimethoate were about 89% at 0.13 ppm and greater than 96% at 0.5-1 ppm.