Habitat diversity : Implications for the conservation and use of predatory insects of Helicoverpa spp. in cotton systems in Australia

Abstract Adoption of within-field monocultures of annual crops in modern farming systems is known to discriminate against and reduce the activity of predatory insects. In Australia, cotton fields are strictly monoculture and lack ecological diversity which could be the major cause of pest problems in the cotton agroecosystem. The utility of crops such as sunflower (Helianthus annuus), safflower (Carthamus tinctorius), sorghum (Sorghum bicolor), lucerne (Medicago sativa) and tomato (Lycopersicon esculentum) as refugia for predatory insects of Helicoverpa spp., when they were planted as strips in cotton fields, was evaluated from 1993 to 1995. Densities of beneficial insects, mainly predatory beetles, bugs and lacewings, were higher in lucerne crops than any other crop tested. In an experiment where lucerne was planted in strips within commercial cotton, the number of predators was highest in the lucerne strip and declined with increasing distance from the lucerne strip to reach their lowestlevel300 m away ...