Augmentative Biological Control in Greenhouses: Experiences from China

To enhance biological control of insect pests in greenhouses, facilities and procedures for mass production of the parasitoids, Eretmocerus sp., Encarsia formosa, and Trichogramma brassicae, and the predator, Aphidoletes aphidimyza were successfully developed in Hengshui, Hebei province, China. Mass production of the aphelinid wasps was achieved by using different plant varieties and host insect species, as well as specific rearing procedures and techniques. Production of T. brassicae was greatly enhanced through the design of special devices and improved rearing techniques. Annual production of natural enemies in our institution reached 2 billion individuals. Biological control experiments conducted in sunlight greenhouses and plastic greenhouses allowed innovative techniques to be developed. Inoculative release techniques were established, including preparation before release, appropriate release time, release rate and special measures. Through experimental results and demonstrations, populations of aphelinid parasitoids and cecidomyid predators were able to establish and play very important roles in pest control on tomato, cucumber, and ornamental crops grown in greenhouses. Parasitism of the whiteflies, Trialeurodes vaporariorum and Bemisia tabasi was as high as 85% to 96%. Natural enemies released also effectively suppressed aphid populations on tomato and cabbage crops. Egg parasitism of the cabbage butterfly, Pieris rapae, and the cotton bollworm, Helicoverpa armigera, by Trichogramma wasps reached 78% to 95% on average. It was shown that natural enemies can suppress populations of target insect pests to below the economic threshold in greenhouse vegetable crops. When these techniques are combined with other non-chemical means of control for diseases and non-target insect pests, such as application of target specific fertilizers, augmentative biological control practices could greatly reduce the utilization of chemical pesticides, making non chemically-polluted vegetable products possible. A great economic benefit was acheived in 11,000 ha of biological control demonstration areas in Hebei, Beijing and Tianjin, by implementing the above augmentation biocontrol techniques from 2001 to 2004.