Abstract
The injurious effect of the common cutworm, Spodoptera litura, on red bean plants was studied through the use of artificial defoliation. As the defoliation rate increased, the number of pods and the weight of grains decreased, especially in the end of the defoliation cycle. At earlier phases of defoliation compensatory leaf areas were relatively large. Average leaf areas of red bean plants consumed by S. litura were 203.9cm2, of which 82% was fed by final instar larvae. Based on relationships between the defoliation area and the yield index of red bean plants, the number of final instar larvae which caused 5% loss of yield (Tolerable injury level), was estimated to be approximately 2per plant. Care should be taken against cutworm damage in the first half of September. After dispersal, larvae directly injure flowers at full flowering stages, as well as infesting pods in the beginning of growth.
