This project investigated how key insect predators contribute to the suppression of the cotton bollworm, Helicoverpa armigera, in Australian cotton crops and explored the interaction between predator abundance and diversity, agronomic practices and predation of H. armigera eggs and larvae. Several strategies were used to determine the importance of different insect predators in cotton: manipulative experiments, direct monitoring of insect abundance in commercial cotton crops, observation of predator behaviour under natural conditions and development of diagnostic laboratory tests (ELISA) to detect recent consumption of H.armigera by predatory arthropods.

The predatory bigeyed bug (Geocoris lubra) and damsel bug (Nabis kinbergii) were

significant predators of H. armigera in cotton crops during seasons of low and high

H.armigera abundance. Over two consecutive cotton seasons (2001-02 and 2002-03), 12-14% of G. Iubra and 22-28% of N. kinbergii tested positive for recent predation on H. armigera using ELISA. Juvenile G. lubra survive and develop better on a diet of H. armigera compared with a diet of aphids under laboratory conditions, further suggesting that H.armigerea is an important food source for this predator. Warm temperatures (above 27 C) also favour breeding of this species.

Although the predatory red and blue beetle, Dicranolaius bellulus, was highly abundant in both the 2001-02 and 2002-03 seasons, only I% tested positive for recent predation on H.armigera. However the diagnostic ELISA test is less effective with predatory beetles than , so these results may underestimate the rate of predation for this species. Most species of native ladybirds found in Australian cotton crops feed primarily on aphids but may feed on H. armigera in the absence of their preferred prey.

Early in the growing season, ants (Pheidole and Iridomyrmex spp.) were observed to prey upon H. armigera eggs in small quantities. Cultivation and flood irrigation severely disrupt ant populations in cotton crops and limit their impact as predators. Minimum tillage combined with a cotton/wheat rotation can increase ant abundance relative to other. Some spiders such as the yellow nightstalker (Cheiracanthium spp. ) are

likely to feed upon Helicoverpa spp. , although their impact on H. armigera was not specifically addressed in this project.

Insecticide use remains the key factor affecting the abundance and diversity of beneficial arthropods in Australian cotton crops. When a soft insecticide regime is used in both conventional and Ingard cotton fields, the abundance of beneficial arthropods is likely to increase dramatically in response to crop growth overthe course of the season.This project has improved our understanding of insect predator ecology and has demonstrate the importance of predatory bugs as key predators of H. armigera. When making pest

management decisions, growers need to consider not only the total abundance of beneficial arthropods within their cotton crops, but also the species composition of the beneficial

community.