The North China cotton region mainly referred to as the Yellow River Valley includes the major cotton-producing provinces of Shandong, Hebei, Henan, Shanxi, Shaanxi, etc. with 3.33 million hectares planted with cotton annually or 2/3 of the nation's total. The region is located in the warm temperate zone with annual average temperature above 11 C, a frost-free period of 180-230 days, and 400-700mm of rainfall. The principal cropping system there had been single cotton. However, the cotton-wheat double cropping system has been rapidly expanded in recent years because of the dramatic increase in human population and decrease in tillage land per capita. In 1990, 50% of the cotton acreage was double-cropped with 70% expected in 1992.

More than 30 species of insect pests are commonly known to attack cotton in this region, of which the cotton bollworm, Heliothis armigera, is one of the most injurious pests at squaring-boll stage with an annual loss in production of over 10%. The bollworm has four generations annually with the first one infesting wheat and the second to fourth attacking cotton. Control of the bollworm has been greatly dependent on insecticides, particularly the pyrethroids in the 1980's. Pyrethroid resistance has become a major problem in control of the bollworm due to the indiscriminate and continuous application of this kind of insecticide in large quantities, seriously threatening the cotton production and development in this region.