Study On Control Of Dendroctonus Valens

Bionomics and occurrence of Dendroctonus valens were studied by using lured-wood, dissection of invaded woods, indoor feed and trapping adult insect methods in Huanglong Forest Region, Shaanxi province. At the same time, the control of Dendroctonus vale was studied with some chemical controlling techniques such as airtight fumigation with aluminum phosphide in plastic, spraying insecticide on trunk and tree-trunk injection,the placing lured-wood and plant attractant were also adopted. Our research results were followed.1. Bionomics of Dendroctonus valens in Shaanxi Huanglong forest regionThe research on the bionomics of Dendroctonus valen showed that this pest overwintered mainly as adult or 3-4 larva in roots of pine at Huanglong Forest Region in Shaanxi Province. It occured 2 generations one year by adult overwintering and 1 generation one year by larva overwintering. The development of the pest was not uniform, with generation overlapping.2. Occurring characteristic of Dendroctonus valens and influencing factorsThe studies showed the pest's damage was tightly associated with forest crown density, physiological condition of hosts, host habitat condition and forest structure. Pinus tabulaeformis forests, which had low crown density, branches chopped badly, severe turpentine and bad forest condition, were damaged severely. The pine stands in forest edge, valley and ridge were damaged seriously. But the trees with good growing condition and the forest with high diversity were damaged lightly. In addition, the damage of trees was associated with slop grade and slope direction, and was not related with altitude.3. Confirming controlling index through the research of Dendroctonus valens distribution pattern.The results showed that the adult insect spatial distribution pattern was aggregated negative binomial distribution, and their nature colonies could be divided into 3 types: type I (new inhabited type), type II (increasing disserving period type) and type III (pervading disserving period type). According to the above conclusion 3 types of controlling index could be recognized: controlled-type, nearly controlled-type and nearly exterminated-type. In the steps of management, firstly, choosing to clear harmed sites, that is to control the pervading disserving period type in order to reduce its pervasion and spread trend. Secondly, adopting stressing controlling measures, that is to eliminate populations in increasing disserving period and to reduce drastically the population and the damage percentage of tree. Finally, exterminate the pest thoroughly were taken so that the insect population density of imperiled forest will decline below the nearly controlled and exterminated indexes.4. Chemical controlling techniques of Dendroctonus valens. The results showed that stem injection with Omethoate and airtight fumigation with aluminum phosphide in plastic could effectively kill the larvae, pupae and even the newly emerged adults of Dendroctonus valens in trunks and roots of tree. The control effect of Trunk injection was same with airtight fumigation with aluminum phosphide in plastic.5. Trapping and killing effect of lured wood and plant attractant to Dendroctonus valens.The trapping and killing tests showed that the utilization of 50-60 cm of low-bait trap can reduce 28.3 percent invasion rate of Dendroctonus valens. The lured wood placing in forest edge has a better effect than the ones in forest. Plant attractant tests showed that the plant attractant have a strong attraction on the adults of Dendroctonus valens, and the most trapping distance was not more than 400m, the invading holes of Dendroctonus valens in forests declined to 76.1% in average after using traps.