Studies On Pollution-free Techniques To Control Monochamus Alternatus Hope (Coleoptera: Cerambycidae) For Suppression Of Pine Wilt Disease

Japanese pine sawyer, Monochamus alternatus Hope, is an important forest pest to pinetrees in China, which not only kills pine trees directly but also is the main vector of pathogenof pine wilt disease-Bursaphelenchus xylophilus. During the past30years, pine wiltdisease spread by M. alternatus made a devastating destruction to the pine forest in mostprovinces of southern China, which affected the ecological environment construction offorest-based in China. In order to explore pollution-free techniques to control pine wilt disease,a method mainly by biological control was used to prevent the vector insect-M. alternatusso that cut off the chain of transmission of B. xylophilus. The study area was in JiuhuaMountains, Anhui Province. Under the funding of national program of public welfare offorestry named "Biocontrol of Monochamus alternatus Hope to Control Pine Wilt Disease(200904025)" and extended project of State Forestry Administration named "Promotion ofDemonstration Projects of Biocontrol Techniques of Pine Wilt Disease in Jiuhua Mountains(2009TK059)", a well control effect of M. alternatus has been achieved. The results weresummarized as follows.1. The biological and ecological characteristics of M. alternatus in Jiuhua Mountains werestudied. It was showed that M. alternatus had one generation in a year, and its larvaeoverwinterred in the host trees. The emergence time of adults started at early May and last5months, and from June to August the numbers of emergence was more than that in othermonths. The distribution type of dead trees of Pinus massoniana was aggregated distribution,and the distribution type of overwintering larvae was the same which appeared that thepopulation of M. alternatus was less from0to2m of the tree, and was more at themiddle-upper part of trees. The distribution type of oviposition scars, boring hole bored bylarvae and emergence hole of M. alternatus had the same distribution type like theoverwintering larvae. Through the relation between population of M. alternatus of a tree andthe diameter at breast height and height of the tree, a population model was built, which couldcalculate the population of overwintering larvae in a dead P. massoniana trees. The annual change of the population of M. alternatus in Jiuhua Mountains was also studied, which showedthat natural enemies and climate were the key factors affecting the annual change of thepopulation. The research on the flight ability of adults appeared that the self-diffusion distanceof adults was139.25m at most. The results above provide a basis for the pollution-freetechniques.2. Biocontrol of the larvae elder than3rd instar and pupae of M. alternatus by the adultsand eggs of Dastarcus helophoroides Fairmaire. The results showed that in the indoorexperiments, releasing adults of D. helophoroides on the wood segments with M. alternatus,the decreased rate of M. alternatus population was91.23%; and releasing eggs of D.helophoroides on the wood segments, the decreased rate of M. alternatus population was91.18%. In the field tests, when the releasing ratio of number of adults of D. helophoroides tothe number of boring hole by larvae was1:1in experiment of releasing D. helophoroides adultsonto the erect trees, the control effects was66.02%and the control effects of releasing adultsonto dead trees sawed and heaped was91.16%at the same proportion. In the test of releasingadults uniformly into field, the control effect of the60d was43.58%at the releasing quantityof3000adults per1hm~2,the control effect of the second year was83.68%at the releasingquantity of3750adults per1hm~2. The control effect was91.48%when ratio of numbers of D.helophoroides eggs to the numbers of boring hole by larvae was16:1in experiment ofreleasing eggs onto the hewed trees. It was concluded that the control effects of releasing eggsonto the hewed trees was the best.3. Studies on the technique of trap trees setting. The most suitable time of trap treessetting was25d before the emergence time of M. alternatus adults. The lasting effect of traptrees was2months, so the other trap tree should be set25d before the previous one gettinguseless at the side. In the degree of forest damaged by M. alternatus of light, medium andheavy, the optimal number of trap trees setting was2,5,14per1ha, which would attract mostof the M. alternatus to oviposit to protect the other trees.4. During the adults stage of M. alternatus using black light and attractant traps to trapand kill adults. Through the test in field, a optimal light wave and a kind of pest controlequipment was filtrated as follows: FWS5and FWS-DBL-1. Combination of the two could kill 49adults of M. alternatus in one night per black light, which had little effect on the naturalenemy. The fecundity of female lured was30.09on average, which appeared that adults luredand killed by black light had not oviposited. It was concluded that black light was a new andfeasible way to control M. alternatus.Trap of YM-50which was made byGuangdong academy of forestry was filtrated from4types of traps. The female of M. alternatus lured was more than the male, whose fecundity was36.30on average which showed that the female lured had not oviposited.5. Control of the young instar larvae of M. alternatus by bethyloids. Through theexperiments of using4species of bethyloids (Sclerodermus guani Xiao et Wu, S. sichuanensisXiao, S. pupariae Yang et Yao, Sclerodermus sp.) to control M. alternatus in door, Sclerodemussp. was filtrated to be the best natural enemy, the most suitable parastic time was the2nd to3rdinstars, and the optimal releasing proportion was2:1(wasps: M. alternatus). In the field,2species of bethyloids was used to control the young instar larvae of M. alternatus, and theoptimal releasing number was determined. The proportion of number of Sclerodermus sp. tonumber of oviposition scars of M. alternatus was4.63:1, and that of S. sichuanesis was5.66:1.In order to explore the potential ability of Sclerodermus sp. on M. alternatus, a method offunction response was used to test the control effects of Sclerodermus sp. on3rd instar M.alternatus. The results showed that maximum numberof hosts killed by preying on hosts byone bethylid wasp was9.48. In the functional response of parasitization, the threshold limit ofthe number of hosts is4. When the ratio of the bethylids to larvae was approximately1:1, themortality of M. alternatus larvae was the maximal.6. Laboratory test on the control of Japanese pine sawyer by two species ofentomophagous nematodes. Under the doses of60000individuals/ml, seven days later,82.22%individuals of M. alternatus at the3rd instar were killed by Steinernema carpocapsae ALL;under the same dose and seven days later,74.44%individuals were killed by Heterorhabditissp. WG. The efficacy of Heterorhabditis sp. WG was faster than Steinernema carpocapsae All,and the lethal peak of the two nematodes to M. alternatus was from the1st to3rd day.7. Investigation of other wood boring insects and natural enemy of M. alternatus in thedead trees of P. massoniana. The survey showed that there were Shirahoshizo patruelis, Hyposipalus gigas, Hyposipalus gigas, Tomicus piniperda, Tomicus minor and Asemumamurense in addition to the largest number of M. alternatus.Tetrigus lewisi and Cryptalaus larvatus was the predatory natural enemy of M. alternatus.Cryptalaus larvatus was most important predatory natural enemy in the forestry, whichdistributed in all heights of dead tree. The other natural enemy, Tetrigus lewisi distributed onlybelow8m in the tree.There were4species of parasitoids of M. alternatus. D. helophoroides parasitized on themature larvae and pupae of M. alternatus, whose parasitism rate was0.34%at natural state. Aspecies of egg parasitoid wasp (Chalcidoidea,Pteromalidae), parasitized the eggs of M.alternatus, and was a mono-parasitic wasp with a parasitism of3.6%. Through theidentification of professor Yang, it was identified as a new species. It is the first time to find outthe egg parasitoids of M. alternatus. A species of braconid wasp (Spathius sp.) on the younglarvae of M. alternatus was found, which was a mono-parasitic wasps with a parasitism of15%.A species of pteromalid wasp (Chalcidoidea,Pteromalidae) was also found on the newlyhatched larvae, with a parasitism of6%.Through the studies of two years in Jiuhua Mountains, a pollution-free technique mainlyby biocontrol to suppress M. alternatus was preliminary achieved. This technique preventedthe spread and damage of B. xylophilus through control of the vector insect——M. alternatus,which would provide a new pollution-free way for control of pine wilt disease. The maintechniques included as follows, some of trap trees were set during the adults stage of M.alternatus, black lights and attractants were used to kill the adults of M. alternatus. During theyoung instar larvae of M. alternatus, bethyloids are released to control the larvae, then theadults and eggs of D. helophoroides are used to control the pupae and larvae over third instar.Last, the trap trees are cut down and covered with stainless steel wire mesh, which would be asthe breeding field of natural enemies to increase the numbers of D.helophoroides for goal oflong-term sustainable control effect.