Inter-seasonal population dynamics and cultural management of Helicoverpa spp. in a Central Queensland cropping system

A strategic trap cropping program targeting Helicoverpa spp. on cotton was developed and implemented in the Emerald irrigation area of Central Queensl and beginning in the winter of 1997. Growers were advised to plant 1% of to tal cropping area to a trap crop of chickpea (Cicer arietinum) in winter an d pigeon pea (Cajanus cajan) in summer. The population dynamics of Helicove rpa spp. in relation to the Emerald cropping system was studied over a 3-ye ar period (August 1996-July 1999) to provide a framework for testing the va lidity of key assumptions underlying the trap cropping strategy and optimis ing the implementation of the program. The population dynamics study showed continuous production of Helicoverpa p upae (moths) in the crop production system during each calendar year. The p attern of pupae production was consistent with cycling of Helicoverpa popul ations between irrigation and rainfed cropping components of the system. Sp ring rainfall and the availability of host plant resources is shown to impa ct on the population dynamics of Helicoverpa in the cropping system and its pest status on early-season cotton. Performance and potential impact of th e trap crops are discussed within the context of host plant availability an d resource bottlenecks. It is shown that the impact of the trap crops on ab undance of Helicoverpa spp. early in the growing season could not be distin guished from that of naturally occurring host plant resource bottlenecks in spring most likely as a result of suboptimal timing of trap crop destructi on. The potential contribution of cultural control tactics to integrated pe st management of Helicoverpa spp. in cropping systems is discussed.