Controlling effect of pyrazole derivatives on some plant diseases. II

Abstract

The present investigation was undertaken to evaluate the controlling effect of 39 pyrazole derivatives substituted at 1-, 3-, 4- and 5-postiion with various substituents upon rice blast, sheath blight and bacterial leaf blight of rice in greenhouse.The structural modifications of pyrazole derivatives had intimate relation with their protective action against rice blast, but no relation with their protective action against sheath blight of rice and with their therapeutic action against bacterial leaf blight of rice.Some 5-hydroxy-3-methylpyrazole derivatives substituted at 1-position with aryl group showed better protective effect upon rice blast than those at 4-position with SCN, but 3-amino-5-hydroxy-1-phenyl-4-thiocyanatopyrazole, which substituted methyl radical at 3-position with amino radical, gave good protective effect. Some 1-(4-thiocyanatophenyl)-pyrazole derivatives at 4-position with CN or COOC2H5 and at 5-position with NH2 or C6H5 also showed good protective effect.Protective effect of 1-(4-chlorophenyl)-5-hydroxy-3-methylpyrazole on sheath blight of rice and therapeutic effect of 5-amino-1-phenyl-4-thiocyanatopyrazole on bacterial leaf blight of rice were evaluated highly but controlling effects of both compounds were estimated less than those of the positive control.