Ecological Types Of Locust Areas And Biological Control Of Eastern Asia Locust (Locusta Migratoria Manilensis) In Weishan Lake Areas

The Easter Asia locust, Locusta migratoria manilensis (Meyen),is one of the important agricultural pests, which has caused serious economic losses to agriculture over the past 20 years for its frequent outbreak in China. Shandong Province is seriously infested area by the locust, especially in the Weishan Lake Areas because of the changeable water levels and a number of other factors. In recent years, serious damage occurred in the area. In order to effectively prevent its infestation, we analyzed therelationship between the water level of Weishan Lake and the area of bare-beach, and the occurrence of the locust. Investigatations about the vegetation and the natural enemies of the lake araes and a number of control trials were carried out. The results were as follows:It was certain that the decline of water level of Weishan Lake Areas can cause the over-exposure of bare-beach area, which supply the suitable base for the locust to feed and reproduce, and the accumulation of a large number of locusts led to the outbreak frquently during the past two decades.Wild vegetation containing 52 families, 209 species in Weishan Lake were made clear. The host plants of the locust, consisting of 2 families, 43 species, were known. Phragmites australis and Echinochloa crusgalli had the highest density in the gramineous plants, followed by Digitaria sanguinalis, goose grass and green foxtail; needle spikesedge herb, Cyperus rotundus and Cyperus glomeratus in Cyperaceae had higher density. All of these hosts were preferable food of the locust.According to the features of water level, vegetation and natural enemies, the sub–locust areas in the Weishan Lake Areas can be divided into 4 special types, i.e. the shallow lake water areas, the flooding lake beach area, the lake terraces and the low-lying land outside lake dam. The flooding lake beach area had abundant kinds of vegetation and natural enemies and was an obvious ecotone and also a natural enemy bank.The species of natural enemies, including 128 species of natural enemies, in Weishan Lake Areas were investigated, among which 68 kinds were more important. Among these natural enemies, there were 16 kinds of enemies feeding on the locust eggs and 112 kinds eating immature and adult locusts. Dominant species of those natural enemies protected and utilized were determined. The number of main natural enemies in the four types of sub–locust areas was changeable. Frogs and birds had the largest number in Shallow lake water area. And the number of ants, spiders and carabid beetles in the the flooding lake beach area, the lake terraces and the low-lying land outside lake dam increased in a proper order , but the number of frogs and birds were progressively less in order.A number of biological control experiments of the locust were carried out with some biological preparations. It was certain that the microbial insecticides including Metarhizium anisopliae, locust nosema, avermectin and the two botanical insecticides,matrine and celangulin, had good insecticidal effectiveness to locusts, but did no harm to natural enemies.Those biological insecticidals coordinate with natural control. Moreover, the insecticidal effectiveness of Bacillus thuringiens was not very good.