Integrated Pest Management (IPM) in cotton emphasises conservation of beneficial species (mainly insects and spiders) to suppress pest populations and reduce the need to apply insecticides. Many beneficial's encountered in cotton are ‘generalists’ allowing them to consume a range of prey, subsisting on non-pest prey when pests are scarce. These generalists are very important in managing pest species especially when the pests are at low densities. Disruption of these generalist beneficial populations, and the resulting reduction in mortality on pest species, can lead to outbreaks of secondary pests. This is especially a risk for fast life cycle species such as mites and aphids but also for pests such as SLW and Helicoverpa and probably also mirids and green vegetable bug(GVB).

Given the significance of generalist predators in biological control (75% of studies quantifying the impact of generalist predators report a positive suppression on pest species), it is surprising that we have a poor understanding of which species have the greatest effect on pest abundance in Australian cotton. This is further compounded because a number of pest species are also generalist predators, such as ‘phytophagous’ thrips species, green mirids and apple dimpling bugs. The lack of information reflects the difficulty in measuring predation by observation and impracticality of remote methods (eg video). However, knowledge of the key beneficial species would be valuable so that they can be targeted for conservation in crops. Further, it can also focus research to understand how these predators survive within the agroecosystem which may lead to strategies to enhance their abundance (e.g. conservation of native vegetation remnants on farm).

This project used ‘molecular diagnostics’ to identify the key predators of silverleaf whitefly (SLW; B. tabaci MEAM1, commonly known locally as B-biotype) and green vegetable bug (GVB, Nezara viridula) both important pests in current Bollgard II dominated cotton systems. This involved collaboration with Professor James Harwood, University of Kentucky, who has pioneered this technique and has extensive experience with its application in agricultural systems.