Studies On Evaluating Control Effect Of The Pine Wood Nematode By Management Of Its Vector Monochamus Alertnatus Hope(Coleoptera:Cerambycidae) Using Life Table Technique

Pine wood nematode disease spreaded rapidly and caused devastating disaster to pine forests, which seriously affected the ecological environment construction of forest-based in China. The key to control pine wood nematode disease is to prevent the main vector insect of Bursaphelenchus xylophilus(Steiner et buhrer), Monochamus alternatus Hope. The biological control technique by introducing Dastarcus helophoroides and Sclerodermus alternatusi Yang to control M. alternatus has been widely used and made remarkable effects. Effects of releasing D. helophoroides and bethyloids with different frequency on controlling the pine sawyer were evaluated using life table technology and the roles of enemy insects in controlling the population of M. alternatus were quantitatively analyzed, providing theory basis for slowing down the pine wood nematode disease via releasing enemy insects. The results were summarized as follows.1. Distribution of M. alternatus in the trunks of Pinus massoniana were studied. The oviposition cut marks were mainly distributed in 2.5~6.5 m of the host trunk. The amount of oviposition cut marks exhibited a significant positive linear relationship with the diameter of hosr trees, but a parabolic relationship with the host height. By contrast, no significanr regression relationship was found between the amount of larvae and hosr diameter. The amount of pupa cells located above the entrance holes was significantly higher than those under the entrance holes. The average distances from the two types of pupa cells to the larvae entrance holes were 3.93 cm and 4.39 cm, respectively; there was no significant difference between them. Furthermore, a larvae vertical distribution model illustration in the trunk of Pine massoniana was set up to exhibits the patterns and a population model was built through the relationship between the population amount of M. alternatus and host diameter and height.2. The larval instar numbers and developmental durations of M. alternatus were determinted. The larvae of pine sawyer had 5 instars without difference between male and female; Prothoracic plate width, mandible length, head capsules width and head beak widthwere most suited for separation of larval instars. The average developmental durations of 1-5instars measured by the method of median population stadia were 6.27 d, 8.86 d, 8.98 d, 12.99 d and 265.52 d.3. Life tables for the natural population of M. alternatus were constructed. Life tables for the natural population of M. alternatus after releasing D. helophoroides and S. alternatusi with different frequency in three consecutive years were constructed. The young larvae of M.alternatus were parasitized by S. alternatusi, while pupa and a part of mature larvae were parasitized by D. helophoroides. The mortality rates during three developmental stages were significantly decreased. After enemy insects were released, their controlling effect on the population of M. alternatus increased year by year; As the increased release frequency, the effects were highlighted, but for Iphiaulax sp.4. The key factor for affecting the population development were confirmed. The death caused by D. helophoroides during pupa stages was the key factor for affecting the population development of M. alternatus from 2013 to 2015, and S. alternatusi was the important lethal factor in the young larval stages.5. The temporal-spatial niche of M. alternatus and its four parasitic enemies were illustrated. In the temporal-spatial order, the niche widthes of M. alternatus were the largest. In the forest with no release of enemies, Iphiaulax sp. appeared high frequency and maintained for a long time on the temporal dimension, showing strong tracking-down efficiency and there had wide range of activities in the natural population of D. helophoroides. After releasing enemies, the temporal-spatial niche widthes of M. alternatus had a downward tendency, while D. helophproides and its overlap index and proportional similarity with M. alternatus kept increasing year by year; there was competition between S. alternatusi and Rhopalicus tutela(Walker) in the young larvae of M. alternatus, reflecting high overlap indexes and proportional similarities on the temporal-spatial niche. But as the increasing release frequency, S. alternatusi had more advantages in the temporal-spatial niche. The temporal-spatial niche widthes of Iphiaulax sp. and its overlap indexes and proportional similarities with M. alternatus were stable, without being affected by the artificial release of enemies.6. The contribution to control M. alternatus of D. helophoroides and Iphiaulax sp. were figured out. The artificial breeding population of D. helophoroides often overwintered solely or gathered with 3-5 individuals together under the top center and southern sides of dead host trees trunk, with more than 60% survival rate. Their average supercooling points and freezing points were-11.86℃ and-10.65℃, so they could overwinter successfully in most dispersal regions of M. alternatus. The parasitoid gave priority to the third to fifth instar larvae of M.alternatus and the parasitic rates were not affected by hosts height, diameter and age. The parasitic rate of 27.38% in the top part of host tree trunks was the highest; the parasitic rate in the phloem of host trees was 20.18%, which was significantly higher than that in the xylem.The key environmental factors to the parasitic rate of the parasitoid were the slope position and the parasitic rates of other enemies.7. The spread of pine wood nematode disease were slowed down through the release of enemy insects. The population of the pine wood nematode-carrying M. alternatus were reduced by releasing enemy insects, along with lower probability of lethal P. massoniana by pine wood nematode disease. Then numbers of dead trees in forest has fallen and slowed down the spread of pine wood nematode disease.In a word, life table technology with supplemental factors was successfully applied to evaluate the effect on the control of M. alternatus using artifical breeding natural enemy insects. It provided data support for slowing down the spread of the pine wilt disease by biological control of M. alternatus and explored new approach to the evaluation of managing forestry trunk borers.