Helicoverpa armigera (Hubner) and H. punctigera (Wallengren) are serious pests of cotton in Australia. These pests constitute a continually increasing production cost for most field crops,

particularly cotton. At the end of the 1996-97 cotton season, cotton growers in the Emerald, Biloela and Theodore areas of CQ agreed to adopt a trap-cropping program as a first step in

the development of an area-wide strategy for management of Helicoverpa.

The principal research objectives of this project were (i) To review the strategic framework and test the validity of ecological assumptions underlying the CQ trap-cropping program, (ii) To develop indicators for assessing the efficacy and impact of trap crops, and (iii) To determine field parameters for optimising trap crop deployment and trapping efficiency under local field conditions. These objectives have all been achieved to varying degrees,

The research outputs of the project show that the CQ trap-cropping strategy is based on sound ecological principles. The strategy seeks to exploit weaknesses in the regional population dynamics of Helicoverpa. The fundamental assumptions underlying the strategy are valid.

The Helicoverpa problem in CQ is to a great extent locally generated within the cropping system. This explains the measurable rise in the level of insecticide resistance in the pest. Host plant bottlenecks are clearly important factors in the population dynamics and pest status of Helicoverpa. This project has shown a relationship between spring rainfall and the incidence of resource bottlenecks in spring, namely, the correlation between spring rainfall and the incidence of Helicoverpa on cotton crops. Within cropping systems, spring resource bottlenecks, if and when they occur, are important determinants of Helicoverpa pest status early in the spring/summer cropping season.