Study on Sustained-Release Pesticides Blended with Fosthiazate-Stearic Acid/Expanded Perlite

The low utilization rate of pesticides makes the migration of pesticides in water and soil,which brings great harm to the ecosystem.The development of pesticide carriers with good drug loading capacity and release control abil-ity is an effective method to realize effective utilization of pesticides and reduce pesticide losses.In this work,fosthiazate-stearic acid/expanded perlite sustained-release particles were successfully prepared by vacuum impregnation using expanded perlite(EP)as carrier,fosthiazate(FOS)as model pesticide and stearic acid(SA)as hydrophobic matrix.The structure and morphology of the samples were studied by BET,FT-IR,TGA,XRD,DSC and SEM.The effects of different mass ratios of FOS to SA on loading capacity and release rate at 24 h were investigated.The sustained release behavior of FOS-SA/EP at different temperatures and pH values was investigated by static dialysis bag method.The results showed that FOS and SA were adsorbed in EP pores by physical interaction.With the mass ratios of FOS to SA decreasing from 7:3 to 3:7,the 24 h release rate of FOS-SA/EP decreased from 18.77%to 8.05%,and the drug loading decreased from 461.32 to 130.99 mg/g.FOS-SA/EP showed obvious temperature response at 25℃,30℃ and 35℃,the cumulative release rate(CRR)of 200 h were 33.38%,41.50%and 51.17%,respectively.When pH=5,the CRR of FOS was higher than that of pH=7,and the CRR of FOS for 200 h were 49.01%and 30.12%,respectively.At different temperatures and pH=5,the release mechanism of FOS-SA/EP belongs to the Fickian diffusion mechanism;When pH=7,the diffusion mechanism is dominant,and the dissolution mechanism is complementary.

The synergistic advantage of combining chloropicrin or dazomet with fosthiazate nematicide to control root-knot nematode in cucumber production

The highly-damaging root-knot nematode(Meloidogyne spp.,RKN)cannot be reliably controlled using only a nematicide such as fosthiazate because of increasing pest resistance.In laboratory and greenhouse trials,we showed that chloropicrin(CP)or dazomet(DZ)synergized the efficacy of fosthiazate against RKN.The combination significantly extended the degradation half-life of fosthiazate by an average of about 1.25 times.CP or DZ with fosthiazate reduced the time for fosthiazate to penetrate the RKN cuticle compared to fosthiazate alone.CP or DZ combined with low or medium rate of fosthiazate increased the total cucumber yield,compared to the use of each product alone.A low-dose fosthiazate with DZ improved total yield more than a low dose fosthiazate with CP.Extending the half-life of fosthiazate and reducing the time for fosthiazate or fumigant to penetrate the RKN cuticle were the two features that gave the fumigant-fosthiazate combination its synergistic advantage over these products used singularly.This synergy provides the opportunity for farmers to use a low dose of fosthiazate which lowers the risk of RKN resistance.Farmers could combine DZ at 30 g m^-2 with fosthiazate at a low rate of 0.375 g m^-2 to control RKN and adequately control two major soil-borne diseases in cucumber greenhouses.

Determination of Fosthiazate Residue in Ginger by Gas Chromatography

[Objectives] An analytical method was established for determining fosthiazate residue in ginger by gas chromatography with flame photometric detector(GC-NPD) to evaluate the safety of fosthiazate in ginger. [Methods] The fosthiazate residue in ginger was extracted with dichloromethane, and subjected to sodium chloride salt-out and liquid-liquid extraction with hexane and dichloromethane(the plant and soil samples had no need for the later two steps). The analysis was performed on gas chromatograph equipped with a flame photometric detector(GC-FPD), and the fosthiazate residue was quantitatively determined by calculating the peak area. [Results] The results of degradation dynamics showed that the half-life of fosthiazate was 7.2-8.7 d in ginger plants, and was 9.9-19.8 d in the soil. The results of the final residue test showed that after applying the fosthiazate granules according to the recommended high dose(active component 58.2 g a.i/m^2,WK) and low dose(38.8 g a.i/m^2,WK) once, the final residual amounts of fosthiazate in the ginger and soil were estimated to be <0.02 mg/kg and <0.02-0.103 mg/kg, respectively, while no fosthiazate residue was detected in all control samples(<0.02 mg/kg). The maximum residue limit(MRL) of fosthiazate in ginger was not established in China, and was 0.2 mg/kg in Japan. [Conclusions] The method was proved to meet the basic requirements of pesticide residue analysis on sensitivity, accuracy and precision and have good linearity. It is recommended that when using fosthiazate granules to control root-knot nematode and root rot in ginger, it is applied at the highest dose of 38.8 g ai/m^2,WK once 30 d before ginger cultivation to treat the soil, and ginger is harvested in the ginger harvest period.

Proteomic response of wheat embryos to fosthiazate stress in a protected vegetable soil

A proteomic analysis of wheat defense response induced by the widely used organophosphorus nematicide fosthiazate is reported. Seed germination and two-dimensional gel electrophoresis （2-DE） experiments were performed using a Chinese wheat cultivar, Zhenmai No. 5. Root and shoot elongation decreased but thiobarbituric acid reactive substances （TBARS） content in embryos increased with increasing pesticide concentration. More than 1000 protein spots were reprodueibly detected in each silver-stained gel. Thirty-seven protein spots with at least 2-fold changes were identified using MALDI-TOF MS/MS analysis. Of these, 24 spots were up-regulated and 13 were down-regulated. Proteins identified included some well-known classical stress responsive proteins under abiotic or biotic stresses as well as some unusual responsive proteins. Ten responsive proteins were reported for the first time at the proteomic level, including fatty acyl CoA reductase, dihydrodipicolinate synthase, DEAD-box ATPase-RNA-helicase, fimbriata-like protein, waxy B 1, rust resistance kinase Lrl0, putative In2.1 protein, retinoblastoma-related protein 1, pollen allergen-like protein and S-adenosyl-L- methionine：phosphoethanolamine N-methyltransferase. The proteins identified were involved in several processes such as metabolism, defense/detoxification, cell structure/ceU growth, signal transduction]transcription, photosynthesis and energy. Seven candidate proteins were further analyzed at the mRNA level by RT-PCR to compare transcript and protein accumulation patterns, revealing that not all the genes were correlated well with the protein level. Identification of these responsive proteins may provide new insight into the molecular basis of the fosthiazate-stress response in the early developmental stages of plants and may be useful in stress monitoring or stress-tolerant crop breeding for environmentally friendly agricultural production.