Chinese White Pine Beetle (dendroctonus Armandi) Population Density And Spatial Distribution In Qinling Mountains

Chinese white pine beetle (Dendroctonus armandi Tsai et Li, Coleoptera: Scolytidae) is arguably the most destructive forest insect in Qinling Mountains, which primarily attacks healthy Pinus armandi Franch of over 30 years and usually increases epidemic proportions causing widespread tree mortality. It severely damage ecological and economic benefits of the forest ecosystems. It is importantly theoretic and practical significance for dymamic detection of D. armandi and sustainable development of ecological system to research population density, spatial distribution and dispersal dynamics of D. armandi in pure and mixed P. armandi forest.The research was implemented in 2008 and 2009, such as the survival and fight ability of marked and unmarked D. armandi with spray paint, mark-release-recapture of D. armandi, and the spatial distribution of D. armandi in Qinling Forest ecosystems. The results are as follows:1. The research of the survival and flight performance in 24h of D. armandi showed that marking did not adversely affect survival since marked and unmarked females and males having similar longevity (P = 0.3377 and P = 0.7410, respectively). On the other hand, there were no significant differences in the flight time and flight distance in 24 h between unmarked and marked insects (P =0.5952 and P = 0.4632, respectively). So the convenient and fast method of making beetles with spray paint should be used even more in future experiments.2. Based on the mark-release-recapture of D. armandi in five plots, the infested success rate is respectively 23.7%, 24.9%, 20.3%, 28.4% and 27.5%. The infested success rate is positively correlated with crown density in all plots. Meanwhile, it is tightly interrelated with diameter at breast height, height, and age of P. armandi.3. The research results show the attacking peak concentrated on 14:00-16:30 everyday in flying and spread period of D. armandi, and the activity is tightly interrelated with temperature. The distribution of D. armandi originally concentrates on the south and west stems of P. armandi and finally is rotiform shape. 4. D. armandi mainly chose to infest the further P. armandi to original host tree. The dispersal distance of in Plot D and E is 17.4 m (17.4±2.1, mean±SE) and 17.3 m (17.3±2.0, mean±SE), respectively. The number of D. armandi decreased with the increase of distance. There are no significant difference of dispersal distribution between Plot D and E (P=0.4515).5. The dispersal duration is 9d and 10d (5.1±0.18, mean±SE; and 4.7±0.21, mean±SE), respectively. The infested fastigium appears in 3–6 days after releasing. There are no significant difference of dispersal time distribution between Plot D and E (P=0.6192).