Review and analysis of damage functions and monitoring systems for pink bollworm (Lepidoptera : Gelechiidae) in southwestern United States cotton

Pink bollworm, Pectinophora gossypiella (Saunders), continues to be a signi ficant pest of cotton worldwide. Two factors essential for effective integr ated pest management (IPM) programs for pink bollworm include: 1) quantific ation of damage-yield relationships, and economic injury levels, and 2) pra ctical sampling plans for estimating pest density, or classifying the pest population above or below an economic threshold. Research conducted over th e past 30 years is reviewed in an effort to quantify damage functions, and to assess the advantages and disadvantages of several common monitoring met hods for pink bollworm. Composite results of five independent studies front 1969 to 1991 show that yields are not reduced until the average seasonal l arval infestation in bells approaches 15%. Each study shows that insecticid e applications are significantly reduced when economic thresholds (ETs, bas ed on moth catches in pheromone traps, or egg or larval infestations in bel ls) are used. Compared with scheduled applications. the average reduction i n insecticide use, based on ETs, ranged from 23 to 37% with no reduction in yield. Although monitoring adult moth nights with pheromone traps continue s to be a. popular tool, the recent development of binomial (presence-absen ce) sequential sampling plans for pink bollworm eggs offers several advanta ges. including an indirect indicator of female moth activity and earlier de tection of subsequent larval infestations in bells. Recent commercializatio n of Bt-cotton, genetically transformed to express an insecticidal toxin fr om the bacterium, Bacillus thuringiensis. provides considerable promise for consistent control of pink bollworm. However, its continued use will depen d upon rapid development and adoption of resistance management plans by gro wers. Moreover, the use of Bt-cotton is likely to be preserved longer if it is implemented within the context of an integrated pest management (IPM) p rogram, rather than as a single tactic.