Performance studies with the new anticoagulant rodenticide,flocoumafen, against Mus domesticus and Rattus norvegicus1

Flocoumafen is a new, highly potent anticoagulant rodenticide from Shell Research. It is effective against all the economically important species tested to date, including those with warfarin-resistant strains. This paper is concerned with its performance against two important commensal rodent species, Mus domesticus and Rattus norvegicus. In laboratory studies these two pest species may absorb a lethal dose of flocoumafen by taking a 0.005% (50 ppm) bait as part of their food intake on only one occasion. This single-feed potency of flocoumafen, combined with its good intrinsic palatability, makes it ideal for use in pulse baiting. Marketed under the Shell trade mark Storm, the principal bait formulation selected for commercialization is the wax-bound block. Recent advances in formulation development include increased resistance to attack by insects and fungi and the incorporation of a bitter taste which acts as a deterrent for humans without influencing the palatability of the bait to rodents. Flocoumafen's outstanding potency has been confirmed in a wide range of field trials. In the UK alone, almost 70 pen and field trials have been successfully completed with a mean estimated control in excess of 95%.     

The dietary toxicity of flocoumafen to hens: Elimination and accumulation following repeated oral administration

In a dietary toxicity study, laying hens received a diet containing the rodenticide flocoumafen at concentrations of 1.5, 5, 10 and 50 mg kg^?1 for five consecutive days. The LC₅₀ at termination following a 28-day observation period was 16.4 mg kg^?1. Livers of birds which received doses of flocoumafen between 5 and 50 mg kg^?1 had concentrations of flocoumafen (1.5 nmol g^?1) that were independent of dose. The data indicate the presence in hen liver of a saturable high-affinity flocoumafen binding site with similar characteristics and capacity to that of the quail and rat. Residues of flocoumafen in samples of breast and leg muscle were low in all exposure groups. Higher, dose-related residues were found in samples of abdominal fat and skin-associated fat and there was a clear demonstration of the transfer of dose-related residues into eggs. In a separate study in which hens were dosed with [¹⁴C]flocoumafen for five consecutive days at a daily rate of 1 and 4 mg kg^?1 body weight, the majority (68 %) of the daily radioactive dose was eliminated over the following 24 hours via excreta. Residues in liver at death or when killed accounted for < 1 % of the cumulative administered radioactivity. Residues in eggs were located primarily in the yolk with maximum concentrations 1.0 mg kg^?1 or 0.18% of the low dose; 2.1 mg kg^?1 or 0.06% of the high dose as [¹⁴C]flocoumafen equivalents were observed at 10 days after start of dosing. Some 40 % of the total activity in the yolk was unchanged flocoumafen.     

Effect of a single oral dose of DDT on intestinal uptake of nutrients and brush border enzymes in protein-calorie-malnourished monkeys

The effect of a single oral dose of DDT (150 mg/kg body wt) has been investigated on the intestinal uptake of certain nutrients and on brush border enzymes in protein-calorie-malnourished monkeys. In contrast to the stimulatory action of DDT on intestinal functions in normal-fed monkeys (A. Mahmood, N. Agarwal, S. Sanyal, P.K. Dudeja, and D. Subrahmanyam, Pest. Biochem. Physiol.12, 141 (1979)) pesticide feeding to malnourished animals inhibited the uptake of alanine and phenylalanine and depressed sucrase, lactase, and leucine amino-peptidase activities. Glucose and leucine uptake was also reduced, albeit insignificantly and alkaline phosphatase activity was unaffected under these conditions. Protein-energy malnutrition per se considerably elevated the uptake of nutrients and disaccharidase activities. Analysis of the chemical composition of microvillus membrane in underfed and pesticide-exposed malnourished animals revealed alterations in protein, sialic acid, and phospholipid fractions of the brush borders. Membrane cholesterol and triglyceride contents remained unaltered in protein-energy-deficient and DDT-fed monkeys.     

北京顺义地区褐家鼠对溴敌隆敏感性研究

采用5个浓度以急性无选择攻毒的方式对捕自北京顺义区褐家鼠进行溴敌隆敏感性检验。结果表明:各浓度的溴敌隆毒饵对褐家鼠的致死率均为100%,此地区褐家鼠对溴敌隆敏感,未检测出抗药性,且致死量与药饵浓度间相关性不显著(p>0.05),各浓度组试鼠死亡时间亦无显著差异(p>0.05)。测试表明在本地区仍然可以继续使用溴敌隆控制褐家鼠。建议采用低浓度以降低鼠防成本和延缓抗药性的产生时间从而延长溴敌隆的使用寿命。     

Animal metabolism of propham (isopropyl carbanilate): The fate of residues in alfalfa when consumed by the rat and sheep

Alfalfa was root-treated with [¹⁴C]propham (isopropyl carbanilate[¹⁴C-phenyl(U)]) for 7 days and then harvested and freeze-dried. Rats and sheep were orally given either ¹⁴C-labeled alfalfa roots ([¹⁴C]root) or ¹⁴C-labeled alfalfa shoots ([¹⁴C]shoot). When the [¹⁴C]root was given, 6.5–11.0% of the ¹⁴C was excreted in the urine and 84.6–89.4% was excreted in the feces within 96 h after treatment. Less than 3% of the ¹⁴C remained in the carcass (total body—gastrointestinal tract and contents) 96 h after treatment. When [¹⁴C]shoot was given, 53.2–55.2% of the ¹⁴C was excreted in the urine, 32.1–43.4% was excreted in the feces, and the carcass contained 0.2–1.1% of the ¹⁴C 96 h after treatment. When the insoluble fraction (not extracted by a mixture of CHCl₃, CH₃OH, and H₂O) of both alfalfa roots and shoots was fed to rats, more than 86% of the ¹⁴C was excreted in the feces and less than 3% remained in the carcass 96 h after treatment. The major radiolabeled metabolites in the urine of the sheep fed ¹⁴C shoot were purified by chromatography and identified as the sulfate ester and the glucuronic acid conjugates of isopropyl 4-hydroxycarbanilate. Metabolites in the urine of the sheep treated with [¹⁴C]root were tentatively identified as conjugated forms of isopropyl 4-hydroxycarbanilate, isopropyl 2-hydroxycarbanilate, and 4-hydroxyaniline. The combined urine of rats dosed with [¹⁴C]shoot and [¹⁴C]root contained metabolites tentatively identified as conjugated forms of isopropyl 4-hydroxycarbanilate, isopropyl 2-hydroxycarbanilate, and 4-hydroxyaniline.     

The fate of imazapyr in a Swedish railway embankment

The long-term fate of the herbicide imazapyr [2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)nicotinic acid] applied to a Swedish railway embankment was studied. Imazapyr was applied at 750 and 1500 g ha(-1) by a spraying train used for full-scale herbicide treatment operations. Soil and groundwater were sampled twice a year for 8 years after application of the herbicide, and the dissipation of imazapyr was studied by HPLC analysis of the residues in soil and groundwater. A clean-up procedure including solid-phase extraction was performed prior to detection by HPLC. Recoveries of imazapyr from soil and water samples were 76-98% and 61-90%, respectively, and detection levels were 0.003 mg kg(-1) and 0.05 microg litre(-1), respectively. Sorption, desorption and microbial amount and activity were also measured at the two locations. The organic matter content correlated positively and the pH negatively to the adsorption of imazapyr on soil, and increasing organic matter contents decreased desorption. Apart from the 0-10-cm top layers of both sites, the microbial amount and activity were small. The main proportion of imazapyr was found in the upper 30 cm of the soil, and degraded with a half-life in the range 67-144 days. Small amounts were transported to lower soil layers and to the groundwater in proportion to the amounts applied. Traces of imazapyr were detected in the groundwater even 8years after application. It was concluded that environmental risks from the use of herbicides on railway embankments could be reduced by including adsorption layers in the embankment during their construction and by reducing the dose of the herbicide used.     

The metabolic fate of methomyl in the cabbage looper

Methomyl, S-methyl N-[(methylcarbamoyl)oxy] thioacetimidate, is metabolized primarily to water-soluble products by susceptible, DDT-resistant, and parathion-resistant strains of the cabbage looper, Trichoplusia ni (Hübner). However, the rate of injected methomyl metabolized varies with the strain to give respective half-lives of 60, 44, and 15 min. In each strain, maximum methomyl-metabolizing activity is present in the last larval stage and prepupal forms, particularly in the fat body. Metabolism by fat body homogenates is dependent on oxygen and NADPH and is inhibited by carbon monoxide and methylenedioxyphenyl synergists. The water-soluble metabolites could not be converted to organosoluble materials by acid or enzymatic treatment. Methomyl sulfoxidation products or oxime derivatives do not appear to be terminal metabolites in the cabbage looper.     

The fate of chlorpyrifos-methyl in stored wheat: A comparison of a laboratory-scale experiment with a pilot-scale treatment

An experiment was carried out in which a pilot-scale treatment of a bulk of grain with chlorpyrifos-methyl was compared with a laboratory treatment of 1 kilogram of grain with ¹⁴C-radio-labelled chlorpyrifos-methyl. The conditions under which the grain was maintained in the laboratory resembled those of the pilot-scale treatment as closely as possible, with sampling and analysis being carried out at the same time and in a similar manner in both. The results from the two experiments were in general agreement with approximately 60% of the chlorpyrifos-methyl remaining intact at the end. A satisfactory level of insect control was achieved in the pilot-scale treatment although it was not possible to assess efficacy in the radiochemical experiment. The use of the radio-label enabled more information about the fate of the degraded insecticide to be obtained from the laboratory experiment. The majority of this radioactivity comprised a fraction which remained within the grain tissue after solvent extraction. The level of activity in the grain tissues gradually increased with time but its nature is as yet unknown. The good agreement obtained between the residue profile and the breakdown patterns in both experiments would suggest that such a laboratory-scale experiment can be a satisfactory model for the situation obtaining in a larger-scale treatment.     

Review of non-target hazards associated with rodenticide use in the USA1

Relatively few field studies have been conducted to evaluate hazards to wildlife from rodenticide use. In the USA, field studies have been conducted on both acute and chronic compounds, including zinc phosphide, strychnine, 1080 (sodium monofluoroacetate), and the anticoagulants diphacinone and brodifacoum. Techniques employed in these studies have included carcass counts, direct counts, indirect counts, nest site monitoring, radiotelemetry, habitat and diet evaluation, necropsy, and residue analysis. Although zinc phosphide generally is not secondarily hazardous, it can pose primary hazards, especially to seed-eating and gallinaceous birds and waterfowl. Strychnine can pose primary hazards, such as to seed-eating birds; secondary poisoning may be minimal unless predators consume stomach or cheek-pouch contents of poisoned prey. 1080 can result in primary poisoning, but it especially can pose a secondary hazard to mammalian predators; the risk to raptors is minimal. Anticoagulants are toxic both primarily and secondarily; they can pose a substantial hazard to raptors. Gallinaceous birds, however, are quite resistant to them. Hazards associated with any one rodenticide may vary significantly depending upon use pattern (e.g. commensal vs field). Environmental concerns over rodenticide hazards to wildlife are increasing greatly and will affect future registrations.     

Laboratory and field trials of the rodenticide brodifacoum against warfarin-resistant Norway rats

Norway rats (Rattus norvegicus) trapped in a low-income housing area in Raleigh, North Carolina, and on a poultry farm in Garner, North Carolina, manifested high levels of resistance to warfarin in laboratory tests. Of the rats tested, 59.1 and 91.7% from the Raleigh and Garner trap sites, respectively, survived a 6-day no-choice test of a diet containing 0.005 % warfarin. The warfarin-resistant rats were subsequently given a choice of a 0.005% brodifacoum bait and a placebo diet. Of 27 rats, 19 died after a 3-day test. Survivors had consumed significantly less brodifacoum (0.1 < P > 0.05) than those that died, but the survivors also died when subjected to an additional 1-day no-choice test of the brodifacoum bait. Field trials, in which warfarin-resistant rats in four poultry houses were fed with poison bait for 14–16 days with 0.005% brodifacoum in a pelletised bait (‘Talon’), resulted in 87–99 % control being achieved.     

The metabolic fate of tridemorph in rats

A single oral dose of [¹⁴C]tridemorph was partly, but rapidly absorbed by rats. Most of the radioactivity was excreted with a half-life of about 15 h. During 5 days, 42.6% was excreted in the urine, 46.7% in the faeces, 1.5% in the expired air and 3.4 % was still retained. 24 % was excreted in the 48 h bile. Sequential wholebody autoradiography indicated that much of the radioactivity was confined to the gastrointestinal tract, liver and kidneys. There was no unexpected uptake of radioactivity. Urinary metabolites were more polar than tridemorph and were also detected in the bile and faeces. The major metabolite in 24 h urine, accounting for 22.3% of the dose appeared to be a side-chain hydroxylated derivative. Cleavage of the morpholine ring was limited to about 1.5 % of the dose.     

珠江三角洲地区黄毛鼠抗药性的发生趋势及其Vkorc1基因多态性

为阐明珠江三角洲地区黄毛鼠Rattus losea对第1代抗凝血灭鼠剂的抗性发生趋势及其遗传机制,以杀鼠灵为标准药物,采用致死期食毒法对2017—2021年在广东省江门市捕获的165只黄毛鼠进行生理抗性检测,并测定每只试鼠的维生素K环氧化物还原酶复合物亚单位1(vitamin K epoxide reductase complex subunit 1,Vkorc1)的编码基因序列,分析其突变情况。结果显示,江门市黄毛鼠对第1代抗凝血灭鼠剂杀鼠灵的抗性率为27.03%～50.00%,在黄毛鼠Vkorc1基因中检测到6个不同的突变位点,包括2个错义突变位点Arg58Gly及Tyr139Cys和4个沉默突变位点Ala41Ala、Cys96Cys、Arg98Arg及Ala143Ala,突变率分别为87.27%、0.61%、1.21%、0.61%、1.21%和0.61%,其中Ala143Ala是在黄毛鼠中新发现的沉默突变位点。表明珠江三角洲地区黄毛鼠已对第1代抗凝血灭鼠剂产生了群体抗性并呈上升趋势,第58位的精氨酸突变成甘氨酸(Arg58Gly)是黄毛鼠抗性基因Vkorc1的主要突变位点。     

The aquatic fate of triclopyr in whole-pond treatments

The aquatic fate of the triethylamine salt formulation of triclopyr (3,5,6-trichloro-2-pyridinyloxyacetic acid) was determined in whole-pond applications in closed (no water exchange) systems in California, Missouri and Texas in two studies conducted in 1995 and 1996. These studies determined dissipation rates of triclopyr and its principal metabolites, 3,5,6-trichloropyridinol (TCP) and 3,5,6-trichloro-2-methoxypridine (TMP) in water, sediment and finfish. Ponds at each site containing a healthy biological community were treated at 2.5 mg AE litre-1 triclopyr. Water and sediment samples were collected through 12 weeks post-treatment, and non-target animals were collected through 4 weeks post-treatment. Dissipation rates for triclopyr, TCP and TMP were similar at each of the study sites, despite differences in weather, water quality, biotic community, light transmission and geographic location. Half-lives of triclopyr in water ranged from 5.9 to 7.5 days, while those of TCP and TMP ranged from 4 to 8.8 and 4 to 10 days, respectively. Levels of triclopyr and TCP declined in sediments at half-lives ranging from 2.8 to 4.6 days and 3.8 to 13.3 days, respectively. No TMP was detected in sediment. Triclopyr and TCP cleared from fish in relation to concentrations found in the water column. TMP levels in fish were generally an order of magnitude higher than levels of triclopyr and TCP, particularly in the visceral portion of the animals. No adverse effects on water quality or on the non-target biotic community were found following triclopyr applications. Results of these studies were comparable to those of triclopyr dissipation studies conducted in reservoirs, lakes and riverine systems in Georgia, Florida, Minnesota and Washington, indicating that the degradation and dissipation of triclopyr and its metabolites are similar in representative systems throughout the USA.     

The fate of the herbicide chlortoluron and its possible degradation products in soils

Chlortoluron hadàhalf-tire in soil of 4–6 weeks. The only metabolite identified was monomethyl chlortoluron, half-life 8 weeks. 3-Chloro-4-methylphenylurea hadàsimilar half-life but was not detected in soils treated with chlortoluron or monomethyl chlortoluron suggesting that 3-chloro-4-methylaniline was formed directly from monomethyl chlortoluron. This aniline hadàhalf-life of 1–2 days in soil, initial concentrations above 5 ppm yielding dimers and trimers predominantly C — N linked. Neither the aniline nor polymeric products were detected in chlortoluron treated soils, presumably because slow formation of the aniline was followed by rapid degradation which kept concentration low.     

The fate of fluroxypyr in the soil in an oil palm agroecosystem

A study on the fate of fluroxypyr in Malaysian agricultural soils was carried out under natural conditions in an oil palm plantation. Three experimental plots in the oil palm estate were selected and three types of treatments were administered, namely fluroxypyr at the recommended dosage, double the recommended rate, and the untreated control. Residues of fluroxypyr in the soil, water, and oil palm leaf were monitored at regular intervals up to 90 days after treatment (DAT). The recovery of fluroxypyr in the water and soil samples ranged from 91–102% when fortified at 1–25 p.p.b. and 91–98% when fortified at 4–50 p.p.b. The recovery from the oil palm leaf ranged from 76–114% when the oil palm leaf sample was fortified at 0.05–1.0 p.p.m. The results showed that fluroxypyr leached down to 50 cm depth at 1 DAT when the plots were treated with either dosage. However, fluroxypyr was not detected in the soil residue at 14 and 21 DAT. Fluroxypyr was not detected in the oil palm leaf samples irrespective of the rates of herbicide application or sampling intervals. The residue of fluroxypyr was detected in water from a nearby stream up to 5 DAT at levels ranging from 0.06–0.21 µg L⁻¹. This result suggests that fluroxypyr persists for a short period in the soil and water ecosystems, but not in the oil palm leaf.     

The fate of the herbicide benzoylprop-ethyl in crops grown in treated soils

The herbicide benzoylprop-ethyl (SUFFIX,^a ethyl (±)-2-(N-benzoyl-3,4-dichloro-anilino) propionate) is applied post-emergence for the control of wild oats (Avena spp.) in wheat. During application some falls onto the soil and in the present work the possible uptake of residues from the soil, particularly by rotation crops has been studied using radioisotope techniques under indoor and outdoor conditions. Soil application at 1 kg/ha gave lower residues in wheat in the year of application than were found in previous studies using overall foliar-soil application. In the radiochemical experiments soil residues did persist into the following year, but residues in potatoes and wheat grown in these soils, although generally below the limit of determination (0.005 mg/kg), were occasionally just above this level (0.006 mg/kg). On the results of the present work, residues in rotational crops from soils treated in the previous year are unlikely to reach the limits of normal analytical determination.     

The environmental fate of diuron under a conventional production regime in a sugarcane farm during the plant cane phase

BACKGROUND: Field studies of diuron and its metabolites 3-(3,4-dichlorophenyl)-1-methylurea (DCPMU), 3,4-dichlorophenylurea (DCPU) and 3,4-dichloroaniline (DCA) were conducted in a farm soil and in stream sediments in coastal Queensland, Australia. RESULTS: During a 38 week period after a 1.6 kg ha(-1) diuron application, 70-100% of detected compounds were within 0-15 cm of the farm soil, and 3-10% reached the 30-45 cm depth. First-order t(1/2) degradation averaged 49+/-0.9 days for the 0-15, 0-30 and 0-45 cm soil depths. Farm runoff was collected in the first 13-50 min of episodes lasting 55-90 min. Average concentrations of diuron, DCPU and DCPMU in runoff were 93, 30 and 83-825 microg L(-1) respectively. Their total loading in all runoff was >0.6% of applied diuron. Diuron and DCPMU concentrations in stream sediments were between 3-22 and 4-31 microg kg(-1) soil respectively. The DCPMU/diuron sediment ratio was >1. CONCLUSION: Retention of diuron and its metabolites in farm topsoil indicated their negligible potential for groundwater contamination. Minimal amounts of diuron and DCMPU escaped in farm runoff. This may entail a significant loading into the wider environment at annual amounts of application. The concentrations and ratio of diuron and DCPMU in stream sediments indicated that they had prolonged residence times and potential for accumulation in sediments. The higher ecotoxicity of DCPMU compared with diuron and the combined presence of both compounds in stream sediments suggest that together they would have a greater impact on sensitive aquatic species than as currently apportioned by assessments that are based upon diuron alone.     

The fate and insecticidal activity of pirimiphos-methyl in stored wheat grain

The degradation of [¹⁴C]pirimiphos-methyl was investigated on a 1-kg bulk of grain stored in the laboratory at 15°C for 28 weeks. Breakdown of pirimiphos-methyl was slow, leaving 77% of the applied dose unchanged at the end of the experiment. The major degradation product was the hydroxypyrimidine (up to 12.5% of the applied dose) with the remainder of the residue (up to 12.1%) remaining within the grain tissues after solvent extraction. The efficacy of the treatment was assessed in a parallel experiment by bioassay of a 5-kg bulk of grain dosed with unlabelled pirimiphos-methyl. 100% Mortality of an organophosphateresistant strain of Oryzaephilus surinamensis L. was maintained throughout the experiment whereas some survival of an organophosphate-resistant strain of Tribolium castanewm (Herbst) occurred after 12 weeks of storage. This increased to give a 20% survival rate at the end of the experiment.