Abstract
The present investigation was undertaken to evaluate the effectiveness of 23 halogenophenylpyrazolone, 16 halogenophenylhydrazine and 12 halogenophenylacetylhydrazine derivatives on sheath blight of rice, and also the effectiveness of some of them on rice blast, bacterial leaf blight of rice, cucumber anthracnose and soft rot of chinese cabbage.
Halogenophenylpyrazolone, halogenophenylhydrazine and halogenophenylacetylhydrazine derivatives substituted at 1-position with 4-halogenophenyl group were effective and the structural modifications of these compounds had intimate relation with their controlling action against sheath blight of rice. It was assumed from the results of this test that halogenophenylpyrazolone derivatives would be decomposed to some hydrazine derivatives upon rice plant and give good controlling effect.
From the results of the seedling bed test in greenhouse, three halogenophenylpyrazolone, five halogenophenylhydrazine and three halogenophenylacetylhydrazine derivatives showed good controlling effect upon rice blast, especially the effectiveness of both 1-(3, 4-dichlorophenyl)-2-acetylhydrazine and 4-chlorophenylhydrazine·formate were estimated very highly. Ten halogenophenylpyrazolone and four halogenophenylacetylhydrazine derivatives gave good protective effect on cucumber anthracnose, but these compounds were not effective on bacterial leaf blight of rice and soft rot of chinese cabbage.
