Control Thresholds for Managing Common Cutworm, Spodoptera litura (Fabricius) (Lepidoptera: Noctuidae) on Chinese Cabbage

摘要

This study aimed to estimate control thresholds for managing common cutworm, Spodoptera litura Faricius (Lepidoptera: Noctuidae) at different larval densities and growth stages of Chinese cabbage in field conditions. The percent yield reduction (Y) ofChinese cabbage infested by different densities of S. litura (X, no. of larvae/100 plants) for three weeks were estimated by Y= - 21.85X+1300 (R2=0.997) 5 days after transplanting and Y= - 12.1X+1382 (R2=0.998) 20 days after transplanting. Based on therelationships between the densities of S. litura larvae and the yield index of Chinese cabbage, the number of larvae (2nd to 3rd instar) which caused 5% loss of yield was estimated as 2.9/100 plants 5 days after transplanting, and 5.6/100 plants 20 daysafter transplanting.