Impact of rice harvest on diapausing yellow stem borer, scirpophaga incertuj^xs (walker) populations

Abstract

Abstract: The effect of transplant aman and deepwater rice harvest on dia pausing populations of rice yellow stem borer, Scirpophaga inccrtulas (Walker), were studied during 1983-85 in Bangladesh. Harvestivng of deepwater rice removed only 12% of borers from the field with straw of 83 cm long but had no effect at a*• on borers in transplant aman harvested at 15 cm height. It might be possible to reduce 20% of S. inccrtulas diapausing larvae from the field by increasing the harvested deepwater rice straw length from 83 cm to 100 cm without affecting the straw quality as cattle feed, but reduction would not be possible by the manipulation of harvested straw length in transplant aman rice. During the winter, S. inccrtulas remained in the stubble on an average 110 cm away from the base of deepwater rice but below the soil surface in transplant aman stubble. The present practice of destroying most deepwater rice stubble by burning during March-April has little effect on borer populations as moths emerge earlier (Fcbruary-March). To derive benefit, stubbles are to be destroyed in a large scale by the end of January. An easy and economic method of destruction of short and isolated transplant aman stubble is needed.