Studies On Population Dynamics Of Woodborers And The Relationship With Pine Wilt Disease On Pinus Massoniana,and Natural Enemies Of Monochamus Alternatus

Pine wilt disease was the devastating destruction to native masson pine forest, and itspathogen, Bursaphelenchus xylophilus (Steiner et Buhrer), was transmitted by woodborers. Toreveal the restrictive function of biotic factors and abiotic factors to the main woodborer, and tofind effective measures to control pine wilt disease, investigation of woodborers and theirnatural enemies, stand factors and climatic factors were carried out. The relationship betweenwoodborers’ population dynamics and pine wilt disease on masson pine, and natural enemies ofMonochamus alternatus were studied on the pine wilt disease regions of Ningbo, ZhejiangProvince, Jiuhua mountian, Anhui Province, and Zunyi, Guizhou Province during May2012toApril2014.1. The woodborer and its natural enemies on masson pine were studied. The resultdemonstrated that there were12kinds of woodborers, and M. alternatus was the most maincarrier of B. xylophilus, which niche breadth and population were the maximum. At the sametime,22kinds of natural enemies were found, and the parasitic rate of parasitoids to M.alternatus was30.83%. The population density of M. alternatus was declined closely withnatural enemies diversity index (r=-0.9283). This illuminated that natural enemies have playedan important role on the controlling of pine sawyer, and Darstarcus helophoroides was themost important natural enemy. M. alternatus own the largest niche breadth and niche overlopwith D. helophoroides, secondly are bethylids.2. The result indicated that the rate of strain with pine wilt disease shows linear increasewith the increment of the population of pine sawyer. The most direct driving force of pine wiltdisease spreading was M. alternates of all the masson pine woodborers, which could infectaveragely4.06masson pines with Bursaphelenchus xylophilus.3. The key factors restricted population of M. alternates in masson pine forest were forest age, species of tree richness, canopy, plant density and average of daily relative humidity. Theregressive model between the population of M. alternates and these5factors was built asy=16.69x1+15.07x2+x3+42.84x6+447.61x13-394.52, which could be used for the prediction onthe population of M. alternates. No obvious difference was found between prediction value andmeasured value.4. Population keeping mechanism of D. helophoroides were studied and resultsdemonstrated that D. helophoroides could keeping a high population in forest continuously bythe parasitization on Shirahoshizo patruelis, Spondylis buprestoides, Asemum amurense andSipalus gigas.5. Sclerodermus sp.(nov.) was discovered and the evaluation system, called ZhongqiIndex, on controlling efficiency of bethylid parasitoids was created, which provided a newquantitative index and method for biological control on developing natural enemies of bethylidparasitoids. The result indicated that the Sclerodermus sp. was excellent, which had greatpotential for the controlling of M. alternates, and each female bethylid could control3~43rdinstar larvae of pine sawyer.