Abstract
Insecticidal characteristics of 10 carbamates, 2-chloro-3, 5-dimethylphenyl-(CXMC), 3, 5 dimethylphenyl-(XMC), 2-methyl-4-allylphenyl-(AMPMC), 2-chlorophenyl-(CPMC) 2-isopropoxyphenyl-(PHC), 3, 4-dimethylphenyl-(MPMC), 2-isopropylphenyl-(MIPC), 3-methylphenyl-(MTMC), and 3, 4-dimethyl-6-chlorophenyl N-methylcarbamate, and carbaryl, were compared using the smaller brown planthopper, Laodelphax striatellus FALLÉN, the green rice leafhopper, Nephotettix cincticeps UHLER, and the brown planthopper, Nilaparvata lugens STÅL. LD50 values by 3 hour contact on residual dry film to the smaller brown planthopper and the green rice leafhopper, and LD50 values by the topical application method to the green rice leafhopper were determined. The LD50 values to the green rice leafhopper by the two application methods were run in parallel. The increase of LD50 values with descending temperature was observed to be little except for carbaryl. KT50 values were determined graphically from the time-knocked-down insects curve. There was little difference in the KT50 values with carbamates and KT50 values with malathion to the smaller brown planthopper though MIPC and carbaryl showed differences. PHC showed the smallest KT50 value among them. KT50 values of AMPMC, carbaryl, and 3, 4-dimethyl-6-chlorophenyl N-methylcarbamate to the green rice leafhopper were larger than those of other carbamates. AMPMC, CXMC, XMC, PHC, and carbaryl were effective against the brown planthopper. The results of spraying test, using the rice plants cultivated in the Wagner's pot, showed that insecticidal activity of PHC, carbaryl, and CXMC to the smaller brown planthopper and the green rice leafhopper lasted long. In the case of the insecticide than application into pot water, the residual insecticidal activity of MIPC was much longer in spraying.
