利用中华甲虫蒲螨防治双条杉天牛幼虫研究

双条杉天牛Semanotus bifasciatus(Motschulsky)是危害柏树类树木的主要蛀干害虫之一,主要以幼虫蛀干危害树木。1～4龄幼虫主要危害韧皮部,4龄后幼虫则开始进入到木质部危害,并且用虫粪堵塞蛀道与外界的联络通道,造成小型天敌进入困难。本文通过利用中华甲虫蒲螨Pyemotes zhonghuajia(YuandZhang)防治双条杉天牛1～2和3～4龄幼虫研究试验,比较了天敌中华甲虫蒲螨不同释放量对双条杉天牛的防治效果。结果表明,当中华甲虫蒲螨释放量为1管/木段时,对1～2龄幼虫防治较好,达83.0%;当中华甲虫蒲螨释放量为2管/木段时,对3～4龄幼虫防治也有较好的防治效果,防治效果高达87.7%;但从防治经济高效的角度出发,最合理高效的投放量为1管蒲螨/木段,防治1～2龄幼虫可行性最高。通过中华甲虫蒲螨对双条杉天牛幼虫的寄生结果比较得知,其对寄生体长为1～2cm的双条杉天牛幼虫有明显的趋向性。

Study of utilizing Pyemotes zhonghuajia to control Semanotus bifasciatus beetles

Semanotus bifasciatus（Motschulsky） is one of the major stem borers of cypress.First to the fourth stage larvae of this species heavily damage phloem and older larvae begin to damage xylem.Older larvae block the tunnel connecting them to the outside world with frass,which may hinder the entrance of small predators.We assessed the effectiveness of the Po mite,Pyemotes zhonghuaji（Yu and Zhang）,as a biological control for first to the second and third to the fourth stage S.bifasciatus larvae,and compared the cost effectiveness of releasing different numbers of mites.The control effectiveness of a treatment rate of 1 000 mites per cm DBH on first to the second stage larvae was up to 83.0%.Although releasing more mites（2 000 /cm DBH） achieved control effectiveness on third to the fourth stage larvae of 87.7%,this was less cost-effective than the lower treatment rate.Po mites are a more effective biological control of S.bifasciatus larvae no more than 1 to 2 cm long.