Field Efficacy Trials of 1%Bifenthrin·thiamethoxam GR against Sweet Potato Weevil

[Objectives]The paper was to verify the field efficacy of 1%bifenthrin·thiamethoxam GR replacing organophosphorus GR against sweet potato weevil and its impact on the yield and quality of sweet potato.[Methods]A total of 4 field trials were conducted in Guangdong Province,including 1%bifenthrin·thiamethoxam GR applied at the doses of 3,4 and 5 kg/667 m^(2),and 3%phoxim GR applied at the dose of 4 kg/667 m^(2).[Results]1%Bifenthrin·thiamethoxam GR applied at the dose of 5 kg/667 m^(2)had excellent control effects on sweet potato weevil,with an average control effect of 77.60%,which was significantly higher than that of 3%phoxim GR applied at the dose of 4 kg/667 m^(2)(48.52%).And the average yield increase rate of sweet potato treated with 1%bifenthrin·thiamethoxam GR reached 24.79%,significantly higher than 12.37%in the control group.[Conclusions]1%Bifenthrin·thiamethoxam GR should be evenly distributed on the ridge surface near sweet potato within 5-7 d after planting,and the recommended dosage is 5 kg/667 m^(2),which will have good control effect on sweet potato weevil and increase the yield of sweet potato.

甲氰菊酯和辛硫磷及其混剂的土壤微生物降解

The degradation rates of fenpropathrin, phoxim and their mixture in un sterilized soil were much quicker than those in sterilized soil, which indicated that soil microorganisms played a significant role in the degradation process in soil. The half life (T 0.5 ) in un sterilized soil was 56.2 d for fenpropathrin, 57.8 d for mixed fenpropathrin, 48.2 d for phoxim, and 41.7 d for mixed phoxim. The corresponding half life (T 0.5 ) in sterilized soil was 135.1 d, 147.3 d, 123.6 d, and 126.2 d, respectively. There were no significant differences for degradation rates between single use and mixed use of fenpropathrin and phoxim.

Joint action of phoxim and fenvalerate on reproduction in male rats

Aim: To evaluate the joint action of phoxim and fenvalerate on the reproductive function in male Sprague-Dawley rats. Methods: The 2×2 factorial analysis experiment was used in the study. The pesticides were orally given at daily doses of phoxim (Pho) 8.2 nig/kg, fenvalerate (Fen) 3.3 mg/kg and Pho 8.2+Fen 3,3 mg/kg (Pho:Fen = 5:2), 5 days a week for 60 days. Sperm motility was measured with computer-assisted sperm motility analysis (CASA) and daily sperm production estimated. Immunoenzymatic method and electron microscopy were used to evaluate the serum testosterone and the testicular morphology, respectively. Results: There were significant decreases in sperm motility parameters in the treated animals, including straight line velocity (VSL), beat cross frequency (BCF), linearity (LIN) and straightness (STR). After treated with Fen, significant decreases in VSL, LIN and STR were demonstrated. Significant decreases of daily sperm production were seen in animals treated with Pho and Pho+Fen in comparison with the controls. Serum testosterone levels were not significantly changed in the treated groups. Factorial ANOVA showed that no significant interactions were noted between Pho and Fen in sperm motility, sperm production and serum testosterone. Both the single and mixed pesticides caused various degrees of testicular lesions, involving vacuolation of endoplasmic reticulum and necrosis of Sertoli cells. Conclusion: The pesticides may cause sperm motility changes and testicular lesions in male rats. The action of Pho and Fen may be additive.

Characterization of carboxylesterase PxαE8 and its role in multi-insecticide resistance in Plutella xylostella(L.)

Carboxylesterase(CarE)was considered as important phase-I detoxifying enzymes which participated in detoxification of different types of insecticides.Up-regulation of CarE genes has been proved playing a major role in insecticide resistance in many pest insects,but its involvement in resistance to insecticides in Plutella xylostella has been rarely reported.In this study,a CarE cDNA named PxαE8 was identified in P.xylostella,which has an open reading frame of 1599 nucleotides and putatively encodes 532 amino acids.The investigation of spatial expression profiles of PxαE8 revealed that it was expressed in all developmental stages,especially in larvae and adults.The body part/tissue-specific expression profiles showed that the PxαE8 mainly expressed in fat body,malpighian tubule and hemolymph of larvae.Further,the relative expression of PxαE8 in two multi-resistant field populations,Hainan(HN)and Guangdong(GD)populations,was found 24.4-and 15.5-fold higher than that in susceptible population,respectively.Knockdown of PxαE8 by RNA interference dramatically increased the mortalities of larvae of HN population treated with LC_(50) of beta-cypermethrin and phoxim by 25.3 and 18.3%,respectively.These results suggested that up-regulation of PxαE8 was involved in resistance to both beta-cypermethrin and phoxim in P.xylostella,which shed light on further understanding of molecular mechanisms of multi-insecticide-resistance in P.xylostella and other pest insects.

Behavior and Quantification Studies of Phoxim Pesticide Using Cyclic and Linear Sweep Stripping Voltammetry at a Mercury Electrode

The adsorptive and electrochemical behaviour of phoxim on a hanging mercury drop electrode were explored in NH3·H2O-NH4Cl buffer by using cyclic and linear sweep voltmmetry. The procedure was successfully applied for the assay of phoxim in vegetable and fruit samples.

Application of Synergist Beichuang in Dose-reduced Chemical Control of Bradysia odoriphaga Yang et Zhang

[ Objective] The paper aimed to explore the dose-reduced pesticide control technique of Bradysia odoriphaga Yang et Zhang. [ Method] The field trids were carried out by routine spraying method, and the control effects of mixtures of Beichuang （ Liangfenbao and Jianweikang） and less dose of phoxim than conrentional against B. odoriphaga larvae were examined. [Result] The results indicated that the control effects of mixtures （containing 14% of Liandeibao or Jian- veikang and 30% -40% less phoxim than conventional dosage） against B. odoriphaga larvae were 84.01% -2.46% and 81.07% -86.12%, respectively. The mntrol effects were equivalent to the conventional dose of phoxim （89.42%）. [ Conclusion] When Beichuang is mixed with phoxim in controlling B. odor/phaga arvae, the suitable reduction level of phoxim is 30% -40%.

Acute Toxicity of Four Organophosphorus Pesticide Products

Acute toxicity of phoxim,acephate,isofenphos-methyl and isocarbophos on male SD rats of clean grade was carried out by gastric lavage method at room temperature of 18℃. These rats are 4 to 5 months old with body weight of 180 to 220 kg. The results indicate that the orders of the toxicity of these four pesticides on SD rats are isofenphos-methyl,isocarbophos,acephate,phoxim. We found that the median lethal concentration of phoxim in 24 h,48 h,72 h and 96 h is 3. 892 g /kg,3. 051 g /kg,2. 618 g /kg and 2. 458 g /kg respectively; the median lethal concentration of isofenphos-methyl in 24 h,48 h,72 h and 96 h is 0. 015 g /kg,0. 013g /kg,0. 012g /kg and 0. 011 g /kg respectively; the median lethal concentration of isocarbophos in 24 h,48 h,72 h and 96 h is 0. 049 g /kg,0. 046 g /kg,0. 043 g /kg,0. 041 g /kg respectively; and the median lethal concentration of acephate in 24 h,48 h,72 h and 96 h is 0. 137 g /kg,0. 113 g /kg,0. 100 g /kg,0. 085 g /kg respectively. Finally,we evaluated the characteristics of toxicity effect and safe concentration of these pesticides to SD rats.

Environmental behaviors of phoxim with two formulations in bamboo forest under soil surface mulching

Phoxim（emulsifiable concentrate（EC） and granules（G）） has been widely used in bamboo forests. The persistence and magnitude of phoxim residues in the crop and soil must be investigated to ensure human and environmental safety. The environmental behaviors of the two formulations were investigated in a bamboo forest under soil surface mulching conditions（CP） and non-covered cultivation conditions（NCP）. The half-lives of phoxim in soil under the two conditions in soil were 4.1–6.2 days（EC） and 31.5–49.5 days（G）,respectively. Phoxim in EC could be leached from the topsoil into the subsoil. A minimized leaching effect was observed for G under NCP. Inversely, an enhanced leaching effect was observed for G under CP. The G formulation resulted in more parent compound（in bamboo shoots） and metabolite（in soil） residues of phoxim than in the case of EC, especially under CP conditions. In addition, the intensity and duration of the formulation effect on soil p H adjustment from G were more obvious than that from EC. Results showed that the environmental behaviors（distribution, degradation, residue） of phoxim in the bamboo forest were significantly influenced by the type of formulation. The prolongation effect from phoxim G might cause persistence and long-term environmental risk. However,bamboo shoot consumption could be considered relatively safe after applying the recommended dose of the two phoxim formulations.