Spatial and Temporal Distributions of the Fourth Generation Cotton Bollworm Eggs on Summer Corn Seeded at Different Times in North China

摘要

The spatial and temporal distributions of the cotton bollworm (Helicoverpa armigera Hübner) eggs on summer corn seeded at early-, middle- and late-times were studied in 1998 - 1999 in Hengshui, Hebei Province in North China. There were several egg peaks during the period from the middle to late August, which were coincided with the pollen-shedding or blister stage of summer corn depending on the change of bollworm occurrence. The eggs were mainly deposited on silks of ears, and leaves and sheaths above the ears.The number of eggs laid on middle- and late-seeded summer corn were higher than that on the early-planted one, resulting in more heavy damage the on late-seeded corn.