Effects of Green Manure Cover Crops on Spodoptera litura (Lepidoptera: Noctuidae) Populations

ABSTRACT Spodoptera litura (F.) is an important pest of numerous agro-economic crops, including green manure cover crops. In Taiwan, sesbania (Sesbanin roxburghii Merr.), sunn hemp (Crotalaria juncea L.), and rapeseed (Brassicae campestris L. variety chinensis) are the most popular green manure crops; sesbania and sunn hemp are commonly planted in warm seasons, whereas rapeseed is grown in the winter. In this study, life-table data for S. litura reared on these three green manures were collected to evaluate their roles as refuges of this pest. The net reproductive rate, intrinsic rate of increase, and finite rate of increase of S. litura were the highest when reared on sesbania (1428.1 offspring, 0.2327 d-1, 1.2621 d-1), followed by sunn hemp (778.4 offspring, 0.2070 d-1, 1.2300 d-1) and rapeseed (737.6 offspring, 0.2040 d-1, 1.2263 d-1). The high growth rates on these green manure crops show that they can serve as potential breeding sites for S. litura. Population projection demonstrated the rapid growth...