Abstract
The purpose of this work is to evaluate the controlling effect of 36 3-methylpyrazole derivatives upon rice blast, sheath blight and bacterial leaf blight of rice and cucumber anthracnose in greenhouse.
The relationship between the structural modifications of 3-methylpyrazole derivatives and their protective effect upon rice blast was intimate, but not on sheath blight of rice and cucumber anthracnose, and also their therapeutic effect on bacterial leaf blight of rice was not intimate.
Some 3-methylpyrazole derivatives substituted at 1-position with p-nitrophenyl or p-halogenophenyl group, at 4-position with SCN or without SCN, and at 5-position with CH3 or C6H5 showed good protective effect upon rice blast, and substitution with SCN at 4-position was more effective than that without SCN, and both 3-methyl-4-thiocyanatopyrazole derivatives substituted at 5-position with CH3 and those at 5-position with C6H5 were similarly effective.
Three pyrazole derivatives, i.e. 3, 5-dimethy-1-(2-nitrophenyl)-4-thiocyanatopyrazole, 3-methyl-1, 5-diphenyl-4-thiocyanatopyrazole, and 3, 5-dimethyl-1-(4-nitrophenyl)-4-thiocyanatopyrazole, showed good protective effect and a little less sporulation inhibiting effect on rice blast, while they were not effective in the therapeutic test. In the seedling bed test in field these three componds were less effective than blasticidin S as a blast control agent.
