Disposition kinetics of cypermethrin and fenvalerate in black bengal lactating goats

Disposition kinetics of cypermethrin and fenvalerate were investigated in lactating black Bengal goats following single dose intravenous administration at 57 and 45 mg kg^?1 respectively. The maximum and minimum blood concentrations of cypermethrin were 18.49 (±3.17) and 0.06 (±0.002) μg ml^?1, while the corresponding values for fenvalerate were 14.58 (±2.37) and 0.04 (±0.005) μg ml^?1 respectively. Both cypermethrin and fenvalerate remained present in blood for 36 h. The mean t1/2β) and Vd_area values were 5.56 (±0.28) h and 10.38 (±2.20) litre kg^?1 for cypermethrin and 5.66 (±0.35) h and 11.31 (±2.20) litre kg^?1 respectively for fenvalerate. Both cypermethrin and fenvalerate persisted in goat milk for 36 h. The t1/2β) and AUC values of fenvalerate were 7.37 (±1.84) h and 122.38 (±11.65) μg h ml^?1 whilst the corresponding values for cypermethrin were 6.66 (±1.54) h and 99.48 (±7.81) μg h ml^?1 in milk respectively.     

Disposition kinetics,cytotoxicity and residues of fenvalerate in tissues following oral administration to goats

Disposition kinetics in goats of fenvalerate [(RS)-α-cyano-3-phenoxybenzyl (RS)-2-(4-chlorophenyl)-3-methylbutyrate] were studied after oral administration at 5 mg kg^?1. The insecticide persisted in blood for up to 48 h. The V_d(area), t_1/2(β), and t_1/2(Ka), of fenvalerate were 12.14 (±0.39) litre kg^?1, 12.25 (±0.25) h and 0.63 (±0.11)h, while the AUC and Cl_B values were respectively 7.35 (±0.39) μg h ml^?1 and 0.68 (±0.04) litre kg^?1 h^?1. The residues in tissues reached a peak four days after insecticide administration and then started to decline. Maximum residue was found in the adrenal gland, followed by liver, kidney and intestine. Both GOT and GPT activities in kidney tissue, but only GPT activities in liver tissue had decreased significantly 4, 8 and 22 days post-administration. The fenvalerate did not produce any significant effects on serum acetylcholinesterase, cholesterol or protein levels in goats. Histopathological examination showed fatty changes in the periphery of lobule, congestion in sinusoid, haemolysis in central vein, necrosis and periportal fibrosis around the central vein of liver, and necrosis in kidney of fenvalerate-treated goats.     

Delayed cuticular penetration and enhanced metabolism of deltamethrin in pyrethroid-resistant strains of Helicoverpa armigera from China and Pakistan

The penetration and metabolism of [14C]deltamethrin was studied in susceptible and resistant Chinese and Pakistani strains of Helicoverpa armigera (Hübner), which were resistant to deltamethrin by 330- and 670-fold, respectively. The penetration of deltamethrin into resistant individuals was significantly slower than into susceptible individuals over a 24-h period. The time taken for 50% penetration of the applied deltamethrin was 1 h for the susceptible strain and 6 h for both of the resistant strains. The internal radioactivity was reduced by the larvae of resistant strains much faster than by the susceptible larvae. After 48 h, 40% of the penetrated deltamethrin was still inside the larvae of the susceptible strain, in comparison with 1.5-5% in the Pakistani strain and 8-14% in the Chinese strain. Both of the resistant strains produced methanol-soluble and water-soluble metabolites, but the susceptible strain produced methanol-soluble metabolites only. By 12, 24 and 48 h after dosing, the amount of methanol-soluble metabolites excreted by the resistant strains was almost double that of the susceptible strain. Both of the resistant strains also excreted 5-7% of the penetrated dose as a water-soluble metabolite after 48 h. In comparison with the Chinese strain, the Pakistani strain exhibited slower penetration, lower internal content and faster excretion of deltamethrin, which correlated with the higher resistance of the Pakistani strain. These findings show that the resistant Pakistani and Chinese strains of H. armigera possess mechanisms of reduced cuticular penetration and enhanced metabolism of deltamethrin and perhaps other pyrethroids.     

Inheritance of resistance and cross-resistance to deltamethrin in Plutella xylostella (Lepidoptera: Plutellidae) from Pakistan

A field population of Plutella xylostella (L) from Pakistan was found to be highly resistant to deltamethrin (>500-fold) but had little or no resistance to spinosad, fipronil, indoxacarb, abamectin, Bacillus thuringiensis (Bt) var kurstaki, Bt var aizawai or Cry1Ac when compared with a susceptible laboratory population, Lab-UK. A sub-population was selected for six generations (laboratory G3-G8) with deltamethrin (delta-SEL), while a second sub-population was left unselected (UNSEL). Bioassays at G9 found that selection with deltamethrin gave resistance ratios of >230 compared with UNSEL (>6730 compared with Lab-UK). The delta-selected population showed no apparent cross-resistance to spinosad, fipronil or indoxacarb. Logit regression analysis of F1 reciprocal crosses between delta-SEL and Lab-UK indicated that resistance to deltamethrin in the delta-SEL population was inherited as an autosomal, incompletely dominant (D(LC) = 0.67) trait. A direct test of monogenic inheritance based on a back-cross of F1 progeny with delta-SEL suggested that resistance to deltamethrin was controlled by more than one factor.     

Genetics and mechanism of resistance to deltamethrin in a field population of Spodoptera litura (Lepidoptera: Noctuidae)

BACKGROUND: Spodoptera litura (F.) causes enormous losses in many economically important crops. The genetics of insecticide resistance has been extensively studied in several insect pests, but there is a lack of information on S. litura. Therefore, the genetics and mechanisms of the resistance of S. litura to deltamethrin were investigated. RESULTS: Bioassays at generation G1 gave resistance ratios of 9, 5, 41, 52 and 49 for deltamethrin, cypermethrin, profenofos, chlorpyrifos and triazofos respectively, when compared with the susceptible Lab-PK strain. Bioassays at G4 with a deltamethrin-selected population (Delta-SEL) showed that selection gave resistance ratios of 63 and 7 for deltamethrin when compared with the Lab-PK and UNSEL strains respectively. Cross-resistance to other insecticides tested was observed in the selected population. A notable feature of the Delta-SEL strain was that resistance to deltamethrin, cypermethrin, profenofos and chlorpyrifos did not decline over the course of five generations. Synergism tests with microsomal oxidase (MO) and esterase-specific inhibitors indicated that the deltamethrin resistance was associated with MO and, possibly, esterase activity. Reciprocal crosses between the Delta-SEL and Lab-PK strains indicated that resistance was autosomal and incompletely dominant. A direct test of monogenic inheritance suggested that resistance to deltamethrin was controlled by more than one locus. CONCLUSION: Stability and dominance of resistance and cross-resistance suggest that insecticides with different modes of action should be recommended to reduce pyrethroid selection pressure.     

小菜蛾对溴氰菊酯的抗性消退与抗性恢复动态

利用选育的抗溴氰菊酯小菜蛾 Plutella xylostella L. 品系第100代为虫源,在不接触任何杀虫剂条件下继代繁殖50代,观察了小菜蛾对溴氰菊酯的抗性消退动态;同时对消退过程中的小菜蛾施加溴氰菊酯选择压力和利用消退过程中的小菜蛾与抗性品系、非抗性品系杂交,观察了小菜蛾对溴氰菊酯的抗性恢复动态.结果表明:①小菜蛾对溴氰菊酯的抗性消退表现为1～15代较慢,15～25代较快,25代后又缓慢的趋势,抗性消退也使氯菊酯、氯氰菊酯交互抗性水平下降;②溴氰菊酯抗性消退过程中,当连续受到一定程度的溴氰菊酯选择压力时,抗性会在几代之内很快恢复;③与其它品系杂交的后代受到一定剂量溴氰菊酯连续处理后,3～4代就能达到或接近抗溴氰菊酯品系第100代的抗性水平,对氯菊酯、氯氰菊酯的交互抗性水平也随之迅速上升.     

Prevalence of cross‐ or multiple resistance to the acetyl‐coenzyme A carboxylase inhibitors fenoxaprop,clodinafop and pinoxaden in black‐grass (Alopecurus myosuroides Huds.) in France

BACKGROUND: Repeated use of acetyl‐CoA carboxylase (ACCase) inhibitors, especially fenoxaprop and clodinafop, since the late 1980s has selected for resistance in Alopecurus myosuroides Huds. (black‐grass) in France. We investigated whether resistance to pinoxaden, a phenylpyrazoline ACCase inhibitor to be marketed in France, was present in French black‐grass populations. We investigated pinoxaden resistance conferred by five mutant ACCase isoforms. Using 84 French black‐grass field samples, we also compared the frequencies of other mechanisms endowing resistance to fenoxaprop, clodinafop or pinoxaden. RESULTS: ACCase mutant isoforms Leu‐1781, Gly‐2078 and, likely, Cys‐2027 conferred cross‐resistance to pinoxaden, while isoform Asn‐2041 possibly conferred moderate resistance. Other mechanisms of resistance to fenoxaprop, clodinafop and pinoxaden were detected in 99, 68 and 64% of the samples investigated, respectively. Cross‐ or multiple resistance to fenoxaprop or clodinafop and pinoxaden was not systematically observed, suggesting a diversity of mechanisms exist. CONCLUSION: Pinoxaden resistance was observed before pinoxaden release in France. Only a fraction of the mechanisms endowing fenoxaprop or clodinafop resistance also confer pinoxaden resistance. Pinoxaden resistance was likely mostly selected for by ACCase inhibitors, and, in some cases, possibly by herbicides with other modes of action. This illustrates the necessity to use metabolisable herbicides cautiously where black‐grass has evolved non‐target‐site‐based resistance. Copyright © 2009 Society of Chemical Industry     

溴氰菊酯降解菌的分离筛选与应用潜力评价

为解决杀虫剂溴氰菊酯的残留污染问题及丰富其降解菌资源库,采用富集培养法,从长期被溴氰菊酯污染的土壤中分离筛选到1株高效降解菌株XQ08,经形态学特征、生理生化及16S rDNA鉴定其为嗜麦芽寡养单胞菌Stenotrophomonas maltophilia,并对菌株发酵条件、菌剂制备方法及应用潜力进行了初步研究。结果表明:在纯培养条件下,XQ08菌株5 d内对50 mg/L溴氰菊酯的降解率可达66.76%;在35 ℃、pH=8及以麦芽糖为碳源、氯化铵为氮源的条件下可获得理想的发酵效果,同时明确了XQ08液体菌剂的制备方法。分别在室内盆栽与田间种植的香菜上喷施高剂量 (推荐剂量10倍,有效成分6.25 g/hm2) 的25 g/L溴氰菊酯乳油,于施药后2、24和48 h施用XQ08菌剂,3、5、7和9 d后,香菜上溴氰菊酯的降解率分别超过20%、50%、60%及70%;7 d后施用菌剂处理组溴氰菊酯残留量均低于0.5 mg/kg,9 d后残留量均低于0.2 mg/kg。本研究首次报道了嗜麦芽寡养单胞菌对溴氰菊酯的降解,发现其XQ08菌剂可有效促进溴氰菊酯的降解,且其降解符合一级动力学特征。嗜麦芽寡养单胞菌XQ08菌株能有效降低或清除蔬菜上的溴氰菊酯残留,具有较好的应用潜力和开发价值。     

Comparative metabolism of famoxadone in fish,plants and animals

The fate and comparative metabolism of famoxadone in fish, plants and animals were evaluated. Famoxadone residues were retained by the fish after exposure (BCF 2800), mainly in the viscera; however, rapid and complete elimination/depuration of the absorbed residues occurred within seven days after the exposed fish were placed in untreated water. Minimal absorption, translocation, and metabolism of famoxadone were observed in grape and potato plants after foliar treatment. Metabolism of famoxadone in the wheat plants, rats, goats, and poultry was extensive. Transfer of ¹⁴C-residues to the wheat grain, milk, eggs, organs and tissues was minimal. Common metabolic reactions of famoxadone in plants and animals include aryl hydroxylation, cleavage of the anilino-oxazolidinedione and phenoxy-phenyl ether linkages, opening of the oxazolidinedione ring and conjugation.     

Up‐regulation of PR1 and less disruption of hormone and sucrose metabolism in roots is associated with lower susceptibility to ‘Candidatus Liberibacter asiaticus’

Huanglongbing (HLB), caused by ‘Candidatus Liberibacter asiaticus’ (Las), is a devastating disease of citrus trees in Florida. Previous work showed that the rootstock cultivar Cleopatra mandarin (Citrus reticulata) has a higher population of Las in roots than Swingle citrumelo (C. paradisi × Poncirus trifoliata). Las reduced fibrous root biomass and sucrose content in Cleopatra mandarin more than in Swingle citrumelo. To understand the mechanisms for susceptibility to Las infection, sucrose and hormone metabolism status were evaluated in Cleopatra mandarin and Swingle citrumelo. In fibrous roots of Cleopatra mandarin, higher expression of genes related to sucrose cleavage was consistent with lower sucrose content compared to noninoculated seedlings at 5 weeks post‐root trimming (wpt). In fibrous roots of Swingle citrumelo, both sucrose content and gene expression related to sucrose cleavage were less disrupted by Las infection compared to Cleopatra mandarin at 5 wpt. Genes associated with salicylic acid (SA), ethylene (ET) and abscisic acid (ABA) synthesis, and ABA signalling, phospholipases D (PLD), and phospholipase A2 (PLA2) were activated by Las infection at 5 wpt in Cleopatra mandarin. Expression of downstream effectors of SA, i.e. NPR1, WRKY70 and PR1, did not change in Cleopatra mandarin, suggesting inhibition of the response to SA by the elevation of ABA, ET and PLD. In contrast, the up‐regulation of PR1, lower response of sucrose metabolism genes and down‐regulation of biosynthesis of phytohormones indicates that Swingle citrumelo activates a more effective defence against this biotrophic pathogen than Cleopatra mandarin.     

Hydrolysis of triasulfuron,metsulfuron‐methyl and chlorsulfuron in alkaline soil and aqueous solutions

The hydrolysis of triasulfuron, metsulfuron‐methyl and chlorsulfuron in aqueous buffer solutions and in soil suspensions at pH values ranging from 5.2 to 11.2 was investigated. Hydrolysis of all three compounds in both aqueous buffer and soil suspensions was highly pH‐sensitive. The rate of hydrolysis was much faster in the acidic pH range (5.2–6.2) than under neutral and moderately alkaline conditions (8.2–9.4), but it increased rapidly as the pH exceeded 10.2. All three compounds degraded faster at pH 5.2 than at pH 11.2. Hydrolysis rates of all three compounds could be described well with pseudo‐first‐order kinetics. There were no significant differences (P = 0.05) in the rate constants (k, day⁻¹) of the three compounds in soil suspensions from those in buffer solutions within the pH ranges studied. A functional relationship based on the propensity of nonionic and anionic species of the herbicides to hydrolyse was used to describe the dependence of the ‘rate constant’ on pH. The hydrolysis involving attack by neutral water was at least 100‐fold faster when the sulfonylurea herbicides were undissociated (acidic conditions) than when they were present as the anion at near neutral pH. In aqueous buffer solution at pH > 11, a prominent degradation pathway involved O‐demethylation of metsulfuron‐methyl to yield a highly polar degradate, and hydrolytic opening of the triazine ring. It is concluded that these herbicides are not likely to degrade substantially through hydrolysis in most agricultural alkaline soils. © 2000 Society of Chemical Industry