Biodegradation of the Organophosphate Insecticide Coumaphos in Highly Contaminated Soils and in Liquid Wastes

Approximately 400000 litres of cattle dip wastes containing approximately 1500 mg litre⁻¹ of the organophosphate insecticide coumaphos are generated yearly along the Mexican border from a USDA program designed to control disease-carrying cattle ticks. Use of unlined evaporation pits for the disposal of these wastes has resulted in highly contaminated soils underlying these sites. Previous work has shown that microbial consortia present in selected dip wastes can be induced to mineralize coumaphos. Our results demonstrate that similar microbial consortia are present in coumaphos-contaminated soils from eight waste sites and that these organisms are capable of mineralizing cou-maphos in these soils using soil slurries to less than 1 mg litre⁻¹ in 7–10 days at 28°C. In addition, our results show that these consortia are able to colonize pea gravel in trickling gravel filters and can be used in these filters to metabolize coumaphos from dip wastes to less than 0·1 mg litre⁻¹ in 7–10 days at 28°C. These simple systems offer potential low cost means to detoxify coumaphos-containing wastes and to bioremediate soils contaminated with this organophosphate compound.     

Residue distribution of the acaricide coumaphos in honey following application of a new slow-release formulation

Acaricide used in beehives for the control of varroa often leaves residues in bee products. The behaviour and distribution of the acaricide coumaphos in honey following the application of a new slow-release strip formulation (CheckMite+) was assessed. The bee colonies were allowed to build new combs without foundation, and two strips were hung in the brood chamber of each colony for a period of 42 days. The distribution of coumaphos residues in honey in relation to the position of the frame and the duration of treatment was examined by collecting samples from each comb at various time intervals up to 145 days after treatment. In the brood chamber, coumaphos was incorporated into honey from the first day of application, and residues accumulated mainly in combs placed next to strips. In the adjacent combs, residues remained at low concentrations with slight variations. In the honey chamber, residue concentrations on the day of strip removal ranged between 0.006 and 0.020 mg kg(-1), while 79 days after application the concentration of coumaphos residues was below 0.020 mg kg(-1). Residues above the EC fixed maximum residue limit (MRL) of 0.1 mg kg(-1) were measured only in brood chamber honey obtained from those combs placed next to strips. In these samples, 0.060-0.111 mg kg(-1) of coumaphos was detected up to 103 days after strip removal. Coumaphos residues in honey extracted from combs that were placed at the edge of the brood chamber were found below the MRL value, even during the 42 day period of CheckMite+ strip treatment.     

Enhanced degradation of atrazine under field conditions correlates with a loss of weed control in the glasshouse

Enhanced degradation of atrazine has been reported in the literature, indicating the potential for reduced residual weed control with this herbicide. Experiments were conducted to determine the field dissipation of atrazine in three cropping systems: continuous Zea mays L. (CC) receiving atrazine applications each year, Gossypium hirsutum L.-Z. mays rotation (CCR) receiving applications of atrazine once every 2 years and a no atrazine history soil (NAH). Subsequent laboratory and greenhouse experiments were conducted with soil collected from these cropping systems to determine atrazine degradation, mineralization and residual weed control. Field dissipation of atrazine followed first-order kinetics, and calculated half-life values for atrazine combined over 2003 and 2005 increased in the order of CC (9 d) = CCR (10 d) < NAH (17 d). Greenhouse studies confirmed that the persistence of atrazine was approximately twofold greater in NAH soil than in CC or CCR soil. Biometer flask mineralization studies suggested that enhanced degradation of atrazine was due to rapid catabolism of the s-triazine ring. Glasshouse efficacy studies revealed a loss of residual weed control in CC and CCR soil compared with NAH soil. These data indicate that, under typical Mississippi Delta field conditions and agronomic practices, the persistence of atrazine may be reduced by at least 50% if the herbicide is applied more than once every 24 months. Glasshouse studies suggest that under these conditions a loss of residual weed control is possible.     

Investigating the in situ degradation of atrazine in groundwater

This study focused on whether or not atrazine could be degraded by indigenous groundwater bacteria as part of an in situ remediation approach. Groundwater was taken from an unconfined middle upper chalk site where concentrations of atrazine and nitrate were typically in the ranges 0.02-0.2 microg litre-1 and 11.6-25.1 mg NO3-N litre-1 respectively. Sacrificial batch studies were performed using this groundwater spiked with atrazine at a concentration of 10 microg litre-1 in conjunction with a minimal mineral salts liquid (Glu-MMSL) medium which contained glucose as the sole carbon source. Treatments comprised either the Glu-MMSL groundwater cultured bacteria or Pseudomonas sp. strain ADP. Results from sacrificial batches indicated the occurrence of bacterial growth and denitrification as monitored by optical density (absorbance at 600 nm) and NO3-N content. Analysis of atrazine content by solid phase extraction coupled with high-performance liquid chromatography showed no degradation of atrazine over a period of 103 days in either treatment. These results indicated that no acclimatised bacterial community featuring positive degraders to the herbicide atrazine had become established within this chalk aquifer in response to the trace levels encountered.     

Efficiency of a bagasse substrate in a biological bed system for the degradation of glyphosate, malathion and lambda-cyhalothrin under tropical climate conditions

BACKGROUND: After the rinsing of spray equipment, the rinsing water contains polluting products. One way to avoid pollution is to bring the rinsing water over a purification system, a biological bed. The system consists of an impermeable tub filled with a biomix substrate that facilitates biodegradation of pesticides. Usually, straw is one component of the biomix. The objective of this study was to assess the efficiency of an unusual substrate, bagasse, a residue of sugar cane, for the degradation of three pesticides, glyphosate, malathion and lambda‐cyhalothrin. RESULTS: Results showed that more than 99% of malathion and glyphosate were degraded in 6 months. In the biological bed, the DT₅₀ value for malathion was 17 days, for glyphosate 33 days and for lambda‐cyhalothrin 43 days. The degradation rate of aminomethylphosphonic acid (AMPA) residues from the degradation of glyphosate was slower than that of the other pesticides (DT₅₀ 69 days). Finally, the innocuousness of the biomix after 6 months of degradation was confirmed by biological tests. CONCLUSIONS: Although the degradation rates of the three pesticides in the present bagasse‐based system were similar to those under temperate conditions, the degradation conditions were improved by comparison with those in soil under the given tropical conditions. Further benefits of this system are pesticide confinement, to avoid their dispersion in the environment by liquids or solids, and a lower overall cost. Finally, possibilities for optimising the bagasse‐based system (e.g. management of the water content and nature of the biomix) are discussed. Copyright © 2008 Society of Chemical Industry     

Fate of the insecticide lambda-cyhalothrin in ditch enclosures differing in vegetation density

Use of the insecticide lambda-cyhalothrin in agriculture may result in the contamination of water bodies, for example by spray drift. Therefore, the possible exposure of aquatic organisms to this insecticide needs to be evaluated. The exposure of the organisms may be reduced by the strong sorption of the insecticide to organic materials and its susceptibility to hydrolysis at the high pH values in the natural range. In experiments done in May and August, formulated lambda-cyhalothrin was mixed with the water body of enclosures in experimental ditches containing a bottom layer and macrophytes (at different densities) or phytoplankton. Concentrations of lambda-cyhalothrin in the water body and in the sediment layer, and contents in the plant compartment, were measured by gas-liquid chromatography at various times up to 1 week after application. Various water quality parameters were also measured. Concentrations of lambda-cyhalothrin decreased rapidly in the water column: 1 day after application, 24-40% of the dose remained in the water, and by 3 days it had declined to 1.8-6.5%. At the highest plant density, lambda-cyhalothrin residue in the plant compartment reached a maximum of 50% of the dose after 1 day; at intermediate and low plant densities, this maximum was only 3-11% of the dose (after 1-2 days). The percentage of the insecticide in the ditch sediment was 12% or less of the dose and tended to be lower at higher plant densities. Alkaline hydrolysis in the water near the surface of macrophytes and phytoplankton is considered to be the main dissipation process for lambda-cyhalothrin.     

杀虫植物颗粒剂对地老虎诱杀效果初报

利用对地老虎幼虫具诱杀作用的夹竹桃叶植物颗粒剂在棉花苗期进行诱杀试验 ,结果表明 :杀虫植物颗粒剂在棉田对地老虎幼虫有较强的诱杀效果 ,平均死亡率达 83.3% ,显示了一定的实用性 ,为植物源杀虫剂的开发利用提供了一种新的思路     

Esterase-mediated tolerance to a formulation of the organophosphate insecticide monocrotophos in the entomopathogenic fungus, Beauveria bassiana (Balsamo) Vuill: a promising biopesticide

The use of biopesticides compatible with chemical pesticides is recommended in pest management as an effective and ecologically sound strategy. The entomopathogenic fungus Beauveria bassiana (Balsamo) Vuill, which is used as a biopesticide, was found to exhibit and lose tolerance to two organophosphorus insecticides widely used in Indian fields. The pattern of response is similar to the esterase-mediated organophosphate tolerance in aphids achieved through esterase gene duplication. Therefore the role of esterase in the tolerance exhibited by isolates of B. bassiana to the organophosphate, monocrotophos, was studied. Both the total soluble protein content and esterase activity were found to increase significantly in B. bassiana cultures that were able to grow in the presence of monocrotophos. With the hitherto established linkage between esterase overproduction and organophosphate tolerance in insects and the observed similarity in response of the insects and B. bassiana to the chemical, it is concluded that tolerance to monocrotophos in B. bassiana may be due to a mechanism similar to that operating in insects. Habituation of the fungus to monocrotophos to initiate expression of esterase gene may help in achieving compatibility between the two.     

Use of mathematical modeling and its inverse analysis for precise assessment of pesticide dissipation in a paddy environment

The extrapolability of the lysimeter test as a dissipation simulator in an actual paddy field was evaluated using mathematical models and their inverse analyses for predicting pesticide fate and transport processes in paddy test systems. As a source of experimental data, a four-year comparative experiment in lysimeters and paddy fields was conducted using various paddy pesticides. First, the dissipations for various active ingredients in granule pesticides under submerged applications were statistically compared using simple kinetic modeling. Second, the dissipation pathways, unobserved experimental components, and effect of the experimental setting were evaluated using a higher tier mathematical model with a novel inverse analysis protocol. Finally, owing to experimental constraints, the unobtainable parameters were extracted from the laboratory container test before being transferred to compare the outdoor experimental data under different formulation types.     

Considering degradation kinetics of pesticides in plant uptake models: proof of concept for potato

BACKGROUND

Degradation kinetics of pesticides in plants are crucial for modeling mechanism-based pesticide residual concentrations. However, due to complex open-field conditions that involve multiple pesticide plant uptake and elimination processes, it is difficult to directly measure degradation kinetics of pesticides in plants. To address this limitation, we proposed a modeling approach for estimating degradation rate constants of pesticides in plants, using potato as a model crop. An operational tool was developed to backward-estimate degradation rate constants, and three pesticides were selected to perform example simulations.

RESULTS

The simulation results of thiamethoxam indicated that the growth dynamics of the potato had a significant impact on the degradation kinetic estimates when the pesticide was applied during the early growth stage, as the size of the potato determined the uptake and elimination kinetics via diffusion. Using mepiquat, we demonstrated that geographical variations in weather conditions and soil properties led to significant differences in the dissipation kinetics in both potato plants and soil, which propagated the variability of the degradation rate constant. Simulation results of chlorpyrifos differed between two reported field studies, which is due to the effect of the vertical distribution of the residue concentration in the soil, which is not considered in the majority of recent studies.

CONCLUSIONS

Our proposed approach is adaptable to plant growth dynamics, preharvest intervals, and multiple pesticide application events. In future research, it is expected that the proposed method will enable region-specific inputs to improve the estimation of the degradation kinetics of pesticides in plants. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.     

利用农药成分监测技术,监控非法添加行为

市场流通的农药产品中,以助剂名义搭售农药行为严重干扰了市场经营秩序。依据《农药成分监测技术指南》中监测方法,开展助剂中农药成分的定性定量监测工作,是强化农药产品质量监管,保障农业生产和农产品质量安全的重要举措。     

Imidazenil,a new drug for the management of convulsions in organophosphate intoxication in rodents

The summary deals with the anti-convulsant and antilethal effects of a new benzodiazepine receptor partial agonist, imidazenil, in DFP intoxication. It has been demonstrated that imidazenil (2–5 mg kg⁻¹) significantly decreases convulsion intensity, rapidly inhibits seizure patterns in brain bioelectrical activity and significantly increases the anti-lethal efficacy of atropine plus obidoxime therapy. These effects are comparable to diazepam at 5 mg kg⁻¹. However, diazepam exhibits myorelaxant activity at therapeutic doses, which are only observed at 5–10 times the therapeutic doses of imidazenil.     

Use of the RFLP-PCR diagnostic test for characterizing MACE and kdr insecticide resistance in the peach potato aphid Myzus persicae

The peach-potato aphid Myzus persicae (Sulzer) has developed a number of insecticide resistance mechanisms owing to the high selective pressure produced by world-wide insecticide treatments. Knowledge of the geographical distribution and the temporal evolution of these resistant phenotypes helps to develop suitable pest-management programs. Current understanding of the major mechanisms of resistance at the molecular level makes it possible to diagnose the presence of modified acetylcholinesterase (MACE) or knockdown resistance (kdr). This paper describes a rapid method for the identification of both resistance mechanisms in a single molecular assay by using restriction fragment length polymorphism of PCR products (RFLP-PCR) in individual as well as pooled aphids.     

Use of oils combined with low doses of insecticide for the control of Myzus persicae and PVY epidemics

Experiments were carried out in the laboratory to assess the insecticidal effect on Myzus persicae Sulzer of different oils applied alone or combined with imidacloprid or pirimicarb. The oils tested were a horticultural mineral oil, a refined rapeseed oil, a refined soya oil and a raw fish oil. When the oils were sprayed alone on pepper plants infested with M. persicae, mineral oil caused the highest mortality of aphids (over 80%). Applied before aphid infestation of pepper leaves and in mixture with low doses of imidacloprid (at one-fifth of the dose recommended by the manufacturer) and pirimicarb (at one-tenth of the dose recommended by the manufacturer), the oils did not significantly increase the toxicity of the insecticides alone. However, sprayed on aphid-infested pepper plants, the mortality rates achieved by imidacloprid/mineral oil and imidacloprid/rapeseed oil mixtures were significantly higher than those achieved by imidacloprid alone at 16 and 24 h. In a field experiment the effect on the incidence of the potato virus (PVY) of the oils in combination with imidacloprid was determined. Mineral oil, rapeseed oil and soya oil were sprayed eight times onto seed potato plants treated with imidacloprid before sowing. Mineral oil reduced PVY-infected plants by 60% and rapeseed oil by 40% compared with plots treated with imidacloprid. The oils applied as 10 ml litre-1 emulsions in water did not cause symptoms of phytotoxicity on the potato plants, and yield was not reduced.     

Biochemical determination of acetylcholinesterase genotypes conferring resistance to the organophosphate insecticide chlorpyriphos in field populations of Bemisia tabaci from Benin, West Africa

Resistance to chlorpyriphos insecticide in Bemisia tabaci from a field population collected in Benin, West Africa was suggested with bioassay showing the presence of two sub-populations. Patterns of acetylcholinesterase (AChE) inhibition by the organophosphate chlorpyriphos-oxon were analyzed to estimate the number of possible genotypes with different sensitivity expected in three B. tabaci field populations collected in Benin. The analysis of inhibition patterns in these populations compared with four laboratory strains of B. tabaci using chlorpyriphos-oxon allowed the differentiation of three possible genotypes. In the reference strain SUD-S we detected two different acetylcholinesterases with different sensitivity to chlorpyriphos oxon suggesting the presence of two genes ace 1 and ace 2. The proportion of the insensitive enzyme (ace 2) was estimated to be 31%. In field populations we can detect two alleles at the same gene locus ace 1: one susceptible ace1S and one resistant ace1R. Both strains called Arizona University and Mexico-S2 have lost sensitive ace1S but the field populations from Benin clearly contained at least three genotypes confirming heterogeneous populations not completely resistant.     

防治蚜虫、白粉虱的新颖杀虫剂-吡蚜酮(pymetrozine)

嗪酮类杀虫剂可分为二嗪酮类和三嗪酮类杀虫剂,因其具有高效、低毒、作用机制独特等特点而在农药研究领域具有重要的地位,其中吡蚜酮是此类杀虫剂中的典型代表。本文综述了吡蚜酮的开发历程和作用机制,以及二嗪酮类和三嗪酮类杀虫剂的研究进展,对该类杀虫剂的构效关系进行了总结,对其发展前景进行了展望。     

Variation in the sensitivity of Callosobruchus (Coleoptera: Bruchidae) acetylcholinesterase to the organophosphate insecticide malaoxon: effect of species, geographical strain and food type

BACKGROUND: Bruchid beetles, Callosobruchus species, are serious pests of economically important grain legumes; their activity in stores is often controlled by the use of synthetic insecticides. Esterases are known to be involved in insecticide resistance in insects. However, there is a dearth of information on esterase activity in the genus Callosobruchus. In this study, the effect of species, geographical strain and food type on the variation in acetylcholinesterase (AChE) activity and its inhibition by malaoxon (malathion metabolite) was investigated using an in vitro spectrophotometric method. RESULT: AChE activity varied significantly among species and strains and also among legume type used for rearing them. Generally, irrespective of species, strain or food type, the higher the AChE activity of a population, the higher is its inhibition by malaoxon. C. chinensis had the highest AChE activity of the species studied, and in the presence of malaoxon it had the lowest remaining AChE activity, while C. rhodesianus retained the highest activity. CONCLUSION: A first‐hand knowledge of AChE activity in regional Callosobruchus in line with the prevailing food types should be of utmost importance to grain legume breeders, researchers on plant materials for bruchid control and pesticide manufacturer/applicators for a robust integrated management of these bruchids. Copyright © 2012 Society of Chemical Industry