Conservation and Enhancement of Biological Control Helps to Improve Sustainable Production of Brassica Vegetables in China and Australia

Brassicas comprise a major group of vegetable crops in Zhejiang Province, China and southeast Queensland, Australia. In Zhejiang, heavy reliance on chemical control to manage insect pests in brassica vegetable production has resulted in insecticide resistance, increased costs of pest control and insecticide residues hazardous to human health. In southeast Queensland, reliance on chemical control has also resulted in increased cost of pest control, control failures due to insect resistance and reduced profits. To improve sustainable production of brassica vegetables in the two regions, a group of Chinese and Australian scientists have undertaken a joint project to develop practical integrated pest management (IPM) strategies for these crops. In both regions, major efforts have been made to evaluate the complexes of endemic natural enemies under different pest management practices, and to conserve and enhance these natural enemies as the central elements of effective management programs. In Zhejiang, field trials were conducted across crops, seasons and localities to test and improve an IPM system that emphasized the use of proven action thresholds for different crop growth stages and strategic application of selective insecticides to promote the impact of natural enemies. Compared with conventional methods, IPM practices were associated with substantially higher natural enemy activity, a 20-70% reduction in input of insecticides, and no yield loss. The improved IPM system has been implemented to various degrees in major vegetable production areas in Zhejiang, and has improved the safety and profitability of production. In southeast Queensland, as an important part of the IPM development and implementation effort, a three-year experimental field study was conducted to evaluate the impact of endemic natural enemies on independent farms practicing a range of pest management strategies. Natural enemy impact was greatest on farms adopting IPM and least on farms practicing insecticide intensive conventional pest control strategies. On IPM farms, the contribution of natural enemies to pest mortality permitted the cultivation of marketable crops with no yield loss but with an average of 70% less insecticide inputs compared to conventional farms. _______________________________ Biological Control for Sustainable Production of Brassica Vegetables Second International Symposium on Biological Control of Arthropods 255 The field studies and IPM implementation in China and Australia indicate that naturally occurring biological control can be substantially enhanced to form the central element of effective IPM programs and improve vegetable production. Demonstration of the effectiveness of biological control in the two regions through an international joint effort not only made the evidence more convincing but also promoted the adoption of the improved IPM strategies by farmers.