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Habitat manipulation : an option to minimise synthetic pesticides and reduce pollution
A wide variety of synthetic insecticides, herbicides and fungicides have been used by vegetable growers to overcome insect pest problems. This has generated undesirable effects, such as insecticide resistance, accidental insecticide poisoning, agrochemical leaching, increased costs of production and importantly, environmental pollution. Contamination of surface and groundwater in several parts of the world, including Australia, is cased by the continuous use of pesticides, herbicides and fungicides (Kookana, Phang & Aylmore 1997; Vighi & Gunari 1995). Leaching of pesticides from soil, a common and growing problem in major agricultural regions, can lead residues in groundwater at trace levels (Bauld 1996). This is of great concern to communities that use groundwater for potable purposes. The Australian population relies heavily on groundwater for drinking purposes; for example two thirds of the drinking water supply in metropolitan Perth is extracted from groundwater. As part of a suite of non-chemical pest management strategies, habitat manipulation offers a method of bio-control by increasing the numbers of beneficial insects (parasitoids and predators) in and around a commercial crop. This study reports on a potential method of bio-control of insect pests and potentially diseases, using insects and other invertebrates were sampled weekly on four different species and species mixes which could be used for habitat manipulation: Goodbug Mix (a proprietary seed mixture-GBM), lablab (lablab pupureus L. Sweet), lucerene (Medicago sativa L.) and niger (Guizotia abyssinica (L.f.) Cass.). The lablab hosted the highest numbers of beneficial insects (larvae and acults of lacewing, ladybird beetles, and spiders) followed by GBM, which hosted the highest numbers of European bees and spiders. Lucerne and niger showed little promise in hosting beneficial insects but in terms of spiders, lucerne hosted significantly more than niger. Lablab and GBM appear to be viable options to grow within cucurbits or as a field boundary species to attract beneficial insects and spiders to control sap-sucking insect pests. Use of these bio-control strategies affords the opportunity to minimise pesticide usage and to lessen the risks associated with groundwater pollution.