Soon after the arrival of the boll weevil, Anthonomus grandis Boheman, in the United States, breeders began to develop cotton, Gossypium hirsutum L., cultivars that matured in a shorter time frame. Earlier-maturing cotton cultivars allowed the continuation of cotton production in the presence of the boll weevil. Development of effective and economical insecticides for major cotton pest insects began in the 1940s, which allowed breeders to develop cultivars that used a longer part of the growing season. However, in the early to mid-1970s, studies showed great economic and pest management advantages for development of shorter-season cultivars. The shift to newly developed, short-season cultivars that began in the late 1970s was complete in all cotton producing states by 1993. These short-season cultivars were more profitable to grow and did not sacrifice yield when compared with the older, full-season cultivars. The recent development of transgenic cotton cultivars via genetic engineering of the delta endotoxin gene from Bacillus thuringiensis kurstaki into cotton has provided a very effective gene for plant resistance to the bollworm, Helicoverpa zea (Boddie); tobacco budworm, Heliothis virescens F., and pink bollworm, Pectinophera gossipiella (Saunders). Experimental cotton strains with the delta endotoxin gene from B. thuringiensis (called bollgard) have been developed which are very resistant to damage from field populations of these insects and are equal in yield to the recurrent parental cultivar. These cultivars offer great advantages for insect control when bred into the currently available short-season cultivars.