On Screening Of Effectual Fungicides And Mixed Preparations For Controlling Rapeseed Sclerotinia Stem Rot

In recent years,Sclerotinia sclerotiorum developed a certain degree of resistance to the fungicides used in the prevention and control of rape sclerotinia stem rot,such as carbendazim and dimethachlon,which led to the reduction and even loss of prevention and control effects of these fungicides.Therefore,screening new fungicides and mixed preparations for the prevention and control of rape sclerotinia stem rot is of great significance.To seek newly effective fungicides for the control of rape sclerotinia stem rot,the toxicity of 12 kinds of newly sale and commonly used fungicides to S.sclerotiorum were tested,and further mixture design and oil dispersion preparation were investigated,in this dissertation.The main results obtained are as follows.1.The toxicities of 12 kinds of fungicides to S.sclerotiorum were tested by applying mycelium growth rate method.The results showed that the order of EC₅₀values is fluazinam（0.023 mg/L）,fludioxonil（0.025 mg/L）,prochloraz（0.035mg/L）,tebuconazole（0.250 mg/L）,azoxystrobin,carbendazim,iprodione,procymidone,dimethachlon,fluorocyclozole,trifloxystrobin,and prothioconazole,suggesting that the former four fungicides have a stronger toxicity to the causal organism of the disease.2.The mixing tests of the four fungicides were conducted by means of Sun Yunpei’s method.In the compounding experiments of tebuconazole and fluazinam,it was found that fluazinam:tebuconazole has an efficiency effect at 8:1,6:1,4:1 and1:8,and the efficiency factor reaches a maximum of 3.8 when the compound ratio is1:8.In the mixing experiments of fluazinam and prochloraz,it was found that fluazinam:prochloraz has an efficiency effect at 10:1,8:1,1:4,1:8 and 1:10,and the efficiency coefficient reaches a maximum of 3.4 when the compounding ratio is 1:10.3.The oil dispersion preparation of fluazinam and prochloraz in 1:10 ratio was tested,and final determination of 40%fluazinam and prochloraz compounding agent oil dispersion formulation was made,（by mass fraction）original compounds 40%,dispersant MOA-7 7.5%,emulsifying agent PEG600MO 7.5%,BY110 7.5%,thickener Silica 0.5%,and loading media（methyl oleate:colza oil=2:1）37%.4.The physical and chemical properties of the oil dispersion were determined,and the results indicated that the dumping properties were qualified,and the residuals after dumping were 1.72%and the residues after washing were 0.36%.The suspension rate was 98.2%.The wet sieve test passed 98.7%by 45μm.The particle size D₅₀ is 3.0μm and D₉₀ is 4.8μm.Low temperature cold storage qualified,high temperature thermal storage oil rate of 6.5%.The properties meet the requirements of the national standard.In the control efficiency experiment on rape sclerotinia stem rot,200 and 400 times dilution spray have a good protection and inhibition effect on the rape leaves in vitro.