Last updated at: (Beijing Time) Monday, December 17, 2001

China Makes Breakthrough in Biological Control of Pests

After four years of work, Chinese scientists have made a breakthrough in the biological control of fall webworm, a kind of forest pest capable of harming over 140 sorts of plants.


Chouioia Cunea Yang -- Natural Enemy of Fall Webworm
Natural enemy introduced
Chinese scientists have made a breakthrough in the biological control of fall webworm after four years of work.

A group of experts headed by Professor Yang Zhongqi have developed a technique to mass produce the natural enemy of the fall webworm, a tiny type of alkali bee named Chouioia Cunea Yang.

Wang Chuanzhen, senior engineer with Yangtai Municipal Forest Protection Station in Yantai in east China's Shandong province, said the bee was chosen after systematic research since 1995 on 26types of fall webworms.

During two consecutive studies of 1,300 ha test fields, Chouioia Cunea Yang have been found parasitized in 95.8 percent ofpupas of fall webworms, bringing the fall webworms under effectivecontrol, says Wang.

The research project has passed an evaluation organized by the Science and Technology Department of the Shandong provincial government.

Earilier efforts not successful
Fall webworms were first found in China in 1979 in Dandong cityin Liaoning province, northeast China, and are capable of harming over 140 sorts of plants, including broadleaf trees, vegetables and crops.

The adult moth has a wingspan of 1 (25 mm) to 1 1/4(31 mm) inches and is snowy white, usually with dark spots on the wings. The larvae are 1 (25 mm) to 1 1/4 (31 mm) inches long and covered with silky hairs. The color varies from pale yellow to green, with a black stripe on the back and a yellow stripe on each side. The pupae are found inside a gray cocoon constructed of silk, frass, and debris. The eggs are small, yellow, or light green, and turn gray before hatching.

Usually the first signs of attack are the large, silken web and skeletonized leaves. The silken web usually contains large numbers of caterpillars.

The moths emerge in the spring. After mating, females lay eggs in masses (400 to 500) on the undersides of host leaves. The eggs hatch in approximately 2 weeks, and the larvae immediately begin to feed and construct webs. They enlarge the web as they continue to feed for 4 to 8 weeks. Then they spin a pupal cocoon in a sheltered place or in the duff or soil. There are at least two generations per year.

Wang said that the fall webworm is very adaptable and is resistant to farm chemicals, and the spraying of farm chemicals during 1988 and 1995 has failed to curb the epidemic situation in some coastal areas in China.


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