寄主树木、寄主和环境因子对松褐天牛深沟茧蜂寄生率的影响研究

目的]松材线虫病是我国对森林危害和威胁最严重的病害,控制其传播媒介昆虫松褐天牛是防治松材线虫病的主要手段。作者发现的松褐天牛深沟茧蜂(Iphiaulax monochamusi Yang)是寄生松褐天牛中老龄幼虫的重要天敌。为明确松褐天牛深沟茧蜂的寄生率与寄主树木、寄主和环境因子的关系,开展了本研究。方法]通过解剖46株松褐天牛危害致死的马尾松,调查了松褐天牛深沟茧蜂寄生率与马尾松、松褐天牛和环境因子之间的关系。结果]调查研究表明:寄主树木的高度、胸径和树龄对松褐天牛深沟茧蜂寄生率没有显著影响,松褐天牛的数量对松褐天牛深沟茧蜂寄生率亦没有显著影响,而松褐天牛幼虫龄期和松褐天牛幼虫在树干上的位置显著影响松褐天牛深沟茧蜂寄生率。松褐天牛深沟茧蜂寄生率与松褐天牛龄期呈显著正相关,其偏好寄生3~5龄幼虫;就天牛在其危害寄主树木上的位置而言,松褐天牛深沟茧蜂偏好寄生马尾松主干上部和在韧皮部危害的松褐天牛幼虫,其对位于马尾松树干上部的寄主幼虫寄生率最高,达27.38%,对在韧皮部生活、危害的寄主幼虫寄生率为20.18%,显著高于位于木质部生活的寄主幼虫寄生率(5.46%)。逐步回归分析表明:影响松褐天牛深沟茧蜂寄生率的关键环境因子是寄主树木的坡位和其它天敌寄生率,其中,坡位与松褐天牛深沟茧蜂呈显著正相关,其它天敌寄生率与松褐天牛深沟茧蜂寄生率呈显著负相关。结论]以上研究初步明确了松褐天牛深沟茧蜂的寄生率与寄主树木、寄主害虫和天敌之间的关系,为今后利用该重要天敌控制松褐天牛打下了基础。

A Study on Host Tree, Host and Environmental Factors Affecting the Parasitism of Iphiaulax monochamusi Yang (Hymenoptera: Braconidae), a Larval Parasitoid of Monochamus alternatus (Coleoptera: Cerambycidae)

Objective] Iphiaulax monochamusi Yang is an important parasitoid on larvae of Monochamus alternatus Hope in Zunyi County, Guizhou Province. For determining the main factors affecting the parasitism of the parasitoid, the relationships among host tree, host and environmental factors were investigated.Method] 46 Pinus massoniana trees died from M. alternatus attacking were investigated in the forests at Zunyi County to explore the effects of host tree, host and environmental factors nor the natural control of the parasitoid.Result] It was found that the effect of neither height, DBH and age of host tree or the number of M. alternatus host on the parasitism were little. However, the M. alternatus'' instar and location on host tree had a great influence on parasitism. There was a significant positive correlation between larval instars of the M. alternatus host and the parasitism of the parasitoid. The parasitoid''s preference was 3-5 instars of host larvae. The parasitoid had partiality for the host larvae tunneled at the phloem and upper trunk of host pine tree. Therefore the parasitism on those parts of host pine trees was the highest with an average parasitism of 27.38%, and the parasitism in the phloem of host trees was 20.18% which was significantly higher than that in the xylem (5.46%). The slope position of the host trees had a significantly positive correlation with the parasitism of I. monochamusi, and the parasitism of I. monochamusi had a significantly negative correlation with the parasitism of other natural enemies.Conclusion] The present study provided a basic information of the relations between parasitism and host tree, host and environmental factors and it would provide references for the biological control of wood borer pests by applying the parasitoid.