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.     

Persistence of fenthion residues in olive oil

The level of fenthion residues was followed for up to one year in olive oil samples. The concentration of the parent compound decreased slowly following a double-phase first-order decay model, both in the freezer and laboratory, while the total concentration (parent compound and its sulfoxide) remained unchanged. Storage, therefore, cannot be used as a decontamination technique for oil containing higher than the toxicologically acceptable residues of this compound.     

Systemic fungicide residues in oil from field-treated olive1

A survey was carried out in Sardegna (IT) on residues in olive oil from olive treated against Spilocaea oleugina with several systemic fungicides at normal and double dose rate: benomyl, thiophanate-methyl, bitertanol, penconazole and fenarimol, all currently not registered for this use in Italy. There was a rapid decrease in benomyl, thiophanate-methyl, and bitertanol in the samples of oil from treated olives collected 0, 10, and 20 days after last treatment, but the degradation of fenarimol appeared slower. In contrast, the concentration of penconazole increased with time. It is suggested that registration of the first four compounds for use on olive would be justified.     

Pyrethroid insecticide residues on vegetable crops

Pyrethroid insecticides were applied on various vegetable crops as foliar treatments to determine dissipation rates. On Chinese broccoli (Guy Lon), Chinese mustard (Pak Choi) and Chinese cabbage (Kasumi, napa), fenvalerate was persistent with residues of 0.10, 0.14 and 0.11 mg kg-1, respectively, by day 21. Cypermethrin residues on head lettuce were below 0.1 mg kg-1 by day 10 but on the leafier romaine and endive varieties it was more persistent and required 14-19 days to dissipate below this concentration. After three applications, residues of cypermethrin in harvested carrots and of permethrin in eggplant were not detected on the day of application. On asparagus, deltamethrin and cypermethrin residues declined to less than 0.1 mg kg-1 by days 1 and 2, respectively; permethrin was more persistent, requiring more than 2 days to decline to less than 0.1 mg kg-1. Deltamethrin on dry (cooking) and Spanish onions was not detected on the day of application. On tomatoes, the concentration of permethrin was 0.093 mg kg-1 on the day of application and declined to about 0.05 mg kg-1 after 2-4 days. In general, permethrin, cypermethrin and deltamethrin residues declined to acceptable concentrations within an acceptable pre-harvest interval. Fenvalerate may be too persistent on these speciality crops unless a maximum residue limit > 0.1 mg kg-1 is permitted.     

Excretion and residues of the pyrethroid insecticide cypermethrin in laying hens

Laying hens were treated daily for 14 days with oral doses of [¹⁴C-phenoxy]cypermethrin (1.52 mg day^?1, 0-7 mg kg^?1) formulated on a small quantity of diet. Radioactivity in the eggs reached a plateau value of 0.05 μg equivalents g^?1 8 days after the start of dosing. Most of the residue was found in the yolk and was a mixture of cypermethrin and material which was closely associated with neutral lipids and phosphatidyl cholines. Four and a half hours after the last dose, the birds were killed and selected tissues were taken for analysis. The highest residue was found in the liver. This was composed of cypermethrin and a mixture of very polar metabolites which were not hydrolysed to significant amounts of 3-phenoxybenzoic acid or its 4-hydroxy derivative.     

Excretion and residues of the pyrethroid insecticide cypermethrin in lactating cows

Two radiolabelled forms of racemic [¹⁴C]cypermethrin (¹⁴C at the benzylic carbon or at C-1 of the cyclopropane ring) were separately administered twice daily to lactating cows in portions of the feed. The amounts dosed were equivalent to 0.2, 5 and 10 μg of cypermethrin per g of feed. The radioactivity eliminated in the milk indicated that the ingestion and elimination of radioactivity were in balance at about day 4 after the start of dosing. Urine and faeces were equally the major routes of elimination, and only a fraction of a percent of the dose appeared in the milk. The residue in the milk was unchanged cypermethrin and was found at a concentration that was proportional to the dose. At the high cypermethrin intake of 10 μg g^?1 of diet, the residue in the milk was 0.03 μg g^?1. Concentrations of residues in the tissues, measured after 7, 20 or 21 days of treatment, were low and in the order: liver>kidney>renal fat>subcutaneous fat>blood>muscle>brain. The major residue in the liver and kidney of a cow that received 10 μg of cypermethrin per g of diet was N-(3-phenoxybenzoyl)glutamic acid. Other conjugates of 3-phenoxybenzoic acid and of 3-(4-hydroxyphenoxy)benzoic acid (unidentified, with the exception of the glycine conjugate) were also present. The residue in fat (about 0.1 μg g^?1 from an intake of 10 μg g^?1 of feed) consisted mainly of cypermethrin.     

A small-scale method for the determination of pyrethroid insecticide residues in crops and soils

A small-scale method for the determination of pyrethroid insecticide residues in crops and soils is described. Compared with the conventional methods, the overall analysis time is reduced by approximately 60% and solvent usage is reduced by approximately 80% using this approach. Results obtained on a range of crops using the small-scale and conventional methods were in good agreement, and a repeatability study showed that the small-scale approach is unbiased and gives good precision. To date, linseed, tobacco, cotton foliage, cotton seed, wheat grain, sorghum, savoy, cauliflower, cabbage, cucumber, apple, peach, blackcurrant, gooseberry, raspberry and soil samples have been analysed using the method. Good recoveries were obtained with all these matrices.     

Persistence on cotton foliage of insecticide residues toxic to Heliothis larvae

Control measures for Heliothis spp. on cotton are usually applied against eggs and newly hatched larvae that infest plant terminal growth. In order to investigate the rate of degradation of a range of insecticides, leaf disc samples were collected, at intervals after application, from both fully expanded cotton leaves and unfolding terminal leaves. The samples were subjected separately to bioassay with newly hatched larvae, and to chemical analysis of the surface deposits. On old leaves, larval mortality caused by two biological insecticides declined by half after field exposure for 36 h, but for the synthetic insecticides, the interval ranged from 4.5 days with endosulfan to 18 days with fenvalerate. On new leaves, the longest interval was 7 days with fenvalerate. Chemical half-life on old leaves ranged from 1 day with endosulfan to 12 days with DDT, and was also shorter on young leaves than the equivalent biological half-life. Bioassay appears to be the most reliable method of assessing insecticidal activity over time. Dosage/mortality data were integrated to give LC₅₀ and LC₉₀ values. Leaf expansion may have the greatest effect on insecticide persistence during the 6 week period of rapid growth commencing 2 months after sowing. Expansion was slower when plants were water stressed, and accelerated following irrigation. The implications of the above findings for cotton pest management are discussed.     

A colorimetric method for the determination of eight carbamate insecticide residues

A simple, quick and reliable method is described for the colorimetric estimation of residues of eight carbamate insecticides. The method is applicable to carbamates which on hydrolysis yield phenols with free para-positions suitable for coupling with a diazo reagent to yield coloured solutions. Optimum conditions for the development and measurement of the colour are described. Analytical data including graphs and some results from mud-bricks and cloth are presented to show the wide applicability of the method.     

Time trends in mortality of Conophthorus ponderosae (Hopkins) exposed to insecticide residues

The protection of the female cones of Pinus monticola (Dougl. ex D. Don) from attack by Conophthorus ponderosae (Hopkins) requires that the beetles be killed before they enter the cone. This encourages consideration of the distributions of length of time to death and how these distributions are changed with different concentrations of various candidate insecticides. In this study a three-parameter Weibull function was employed to depict the distributions for data originally collected for a probit analysis. The time to achieve 90% mortality as defined by the Weibull function was taken as a dependent variable, and a regression evaluation was used to define relationships with concentration for selected insecticides. The mode Y = b0 + b1 · X⁻1, in which Y = LT90 and × = insecticide concentration in g litre⁻1, proved useful when a sufficient range of concentrations was included in the testing.     

Organochlorine insecticide residues in bovine milk and manufactured milk products in Illinois, 1971-76.

Monitoring activities were initiated in 1971 to survey the occurence and levels of organochlorine insecticide residues in bovine milk and manufactured milk products in Illinois. Dieldrin residues were the most prevalent, and were found in 96 percent of the samples. Dieldrin also accounted for the highest average residue concentration (0.09 ppm). Only 0.3% of the samples contained illegal insecticide residues. Levels of DDT and lindane were generally declining, but those for dieldrin and heptachlor epoxide tended to remain constant.