Tests with Some Insecticides against the Paddy Borer, Schoenobius incertulas , in Taiwan

Abstract

Tests made all the second paddy crop in Taipei in 1960 to study the initial and residual effects of parathion, Sumithion ( O,O -dimethyl- O -(3 methyl-4 nitrophenyl) thioposphate), dimethoate and endrin against primarily the newly hatched larvae of the paddy borer, Schoenobius incertulas Wlk., indicated that control by the residues or the plant metabolites of these compounds was better with higher concentrations or dosages, and appeared to vary considerably with the stage of growth of the plants. At the maximum tillering stage, excellent control was obtained with parathion for about 12 days, with Sumithion for about 7 days, but dimethoate lost its persistent effect rapidly 1.5 to .5 days after treatment. Endrin gave poor residual effect in one test at the maximum tillering stage but at the heading stage it gave as good results as parathion, and was better than Sumithion. Re-sidual effect of these chemicals at the heading stage of paddy plants was, on the whole, poorer than at the maximum tillering stage.

At the maximum tillering stage, Sumithion and parathion gave better control initially than dimethoate or endrin. When the plans were thoroughly wet with the sprays, no significant difference in initial kill was obtained with a 0.02% or a 0.04% concentration with either parathion or Sumithion. At the heading stage dimethoate at a 0.06% concentration appeared to be better than parathion or Sumithion at a 0.04% concentration. At the milk-ripe stage dimethoate gave the best initial control followed by parathion and Sumithion. In these tests endrin was found to penetrate deeply into the leaf sheath and killed 30% to 57% of the young larvae feeding within.