Development Of Environmentally Friendly Pesticide Formulations Such As Metalaxyl, Azoxystrobin, Fludioxonil And So On

Currently,seed treatment with fungicide has became a universal measure to control soil fungal diseases.However,commercialized metalaxyl-azoxystrobin-fludioxilone seed coating agents have shortcoming,such as short persistence,high exfoliation rate,and the seed germination and seedling growth were inhibited under high dose condition.Pyraclostrobin exhibited satisfactory control efficacy on rice blast disease.Unfortunately,the application of pyraclostrobin in paddy fields is significantly restricted owning to the high toxicity to aquatic organisms.Microencapsulation technology is an effective means of solving the abovementioned problems.Therefore,the microcapsules were prepared by interfacial polymerization and the synthesis conditions were optimized.The sustained release behavior and release mechanism of microcapsules was investigated.To evaluate the effects of microcapsule seed treatment formulations on the safety for treated seed,and physiological and biochemical indicators of peanut seedlings.Acute toxicity to zebrafish,spreadability on rice blades,and control effect on rice blast of pyraclostrobin microcapsule formulations were investigated systemically.The conclusiond are shown as follows:1.Metalaxyl-M · azoxystrobin · fludioxonil microcapsule seed treatment formulations:（1）Metalaxyl-M · azoxystrobin microcapsules were prepared by interfacial polymerization,and optimized to obtain an optimal shear rate of 16000 rpm/min.The mean diameter of microcapsules was 3.951 μm.The size distribution is narrow（0.261-12.3 μm）.（2）The microcapsules were characterized through optical microscopy（OM）,scanning electron microscopy（SEM）,fourier transform infrared spectroscopy（FTIR）and Laser particle size analyzer（LPSA）.The microcapsules were nearly spherical and no obvious defects.The particle size was consistent with normal distribution.Sustained-release experimental studies showed that microcapsules have a pronounced slow-release effect and can prolong the utilization of pesticides.（3）Microencapsulated seed treatment formulation for azoxystrobin ··metalaxylM··fludioxonil were prepared by mixing in proportion the abovementioned microcapsules with fludioxonil 20% flowable suspension.The results of germination test showed that the germination rate of peanut seeds in the treatment group was 91.7% under the ratio of the drug species was 1:500,which was equivalent to the blank control.（4）Peanut seeds were treated with either traditional or microencapsulated formulations.Each of the formulations of seed coating was applied to the seeds at concentrations of 4.4,2.2,0.367,0.22,and 0.157 g a.i./kg seed,and the physiological and biochemical indicators of peanut seedlings were evaluated through a house plant experiment.At a high dose of 4.4 g a.i./kg seed,the emergence rate,shoot fresh weight,root fresh weight,plant height,and root length of the peanut seedlings in the conventional seed treatment formulations group were inhibited to some extent.By comparison,the inhibitory effect of microcapsule formulations treatment on peanut seedlings was not significant.Compared with the blank control,the chlorophyll a（C_a）,chlorophyll b（C_b）,peroxidase（POD）,and catalase（CAT）activity of the seedlings treated with the microcapsule seed treatment were improved.2.Pyraclostrobin microcapsule suspension formulations:（1）Pyraclostrobin microcapsules were prepared by interfacial polymerization.The mean particle size of microcapsules synthesized under optimal conditions was 3.945 μm.The particle size distribution was narrow（0.815-8.674 μm）and the encapsulation efficiency（EE）was 96.86%.The microcapsules were characterized by OM,SEM,FTIR,Differential scanning calorimetry（DSC）and LPSA.The microcapsules were nearly spherical and no obvious defects.The particle size distribution was in accordance with the normal distribution.In addition,the quality control indicators of pyraclostrobin microcapsule suspension formulations are in line with national and industry standards.（2）The release behavior of pyraclostrobin microcapsules in 40% methanol: water solution was studied and the release curve was fitted.The value of fitting result was 0.5236,indicating that the release mechanism of microcapsules was controlled by diffusion-erosion.（3）The acute toxicity tests showed that the LC50 of pyraclostrobin EC to zebrafish was 0.05 mg/L,while microcapsule formulations were relatively safe for zebrafish(LC₅₀=0.413 mg/ L).The toxicities lowered 8 to 9-fold.（4）The spreading experiment of microcapsule formulations on rice leaves showed that the silicone additive QS-302 can significantly reduce the surface tension and contact angle of the agents.Field experiment showed that the disease control efficacy of microcapsule formulations was 85.03% for panicle blast,which was superior to that of the control fungicide treatment（81.36%）.Thus,the control effect of microcapsule formulations was satisfactory on rice blast disease.