Trends in Helicoverpa spp. (Lepidoptera: Noctuidae) abundance on commercial cotton in central Queensland: implications for pest management

Abstract

Within and between-season patterns of Helicoverpa egg and larval abundance on commercial cotton in central Queensland were analysed using crop scouting data for 5 farms over 9 consecutive growing seasons (1989/90–1997/98). Within seasons, analysis of mean weekly egg density profiles for individual farms reveals asynchronous oviposition activity among farms for approximately the first 8 weeks of the growing season. Beyond 8 weeks oviposition activity appears to be well synchronised among farms. Weekly egg density profiles differed significantly between seasons. Mean larval density increases linearly throughout the season. Medium and large larvae were detected on cotton as early as 5–6 weeks after planting. The ecological significance of oviposition activity and larval survival patterns on cotton is discussed. Pesticide application and control strategies are discussed.