[Life-table of Helicoverpa armigera in northern China and characters of population development in southern and northern China].
The population dynamics of Helicoverpa armigera in Raoyang County, Hebei Province as an example in Northern China was researched, and its natural life-table was established. The results showed that total mortality of first to fourth generations of cotton bollworm in Northern China were 98.3%, 98.34%, 98.69% and 99.13%, and the population tendency index (I) were 3.97, 1.50, 1.41 and 1.09, respectively. A comparative analysis of the natural life-table of cotton bollworm in Southern China and in Northern China showed that the survival curves were concave curves in the two cotton zones. The curve showed that the mortality of cotton bollworm was higher in its egg stage to the second instar, and lower after the third instar. The key death factor of cotton bollworm was the scouring effect of rain and wind in Southern China, and the predation of its natural enemies in Northern China. The hatch period to the first instar was the key stage in Northern China and Southern China, and in this time, its larva instar was slim, fragile and sensitive to bad circumstances, so its mortality was higher. The second and third generations were the key damage generations in Northern China, while the third and fourth generations were the key damage generations in Southern China. The development and damage characters of each generation in Northern China and in Southern China were discussed.