云杉顶芽瘿蚊发生与为害规律

云杉顶芽瘿蚊是近几年甘肃定西地区发现的一种危害云杉顶芽生长点的新害虫。幼虫蛀入云杉顶芽取食生长点。分布面积 4 0 0 0 hm2 ,成灾面积 6 6 7hm2 ,受害株率 97.4 % ,枝条顶芽受害率 83.7% ,10 0 cm长枝虫口密度 9.2 4头 ,虫害指数 58.2 1。为害规律 :人工造林、密度越大、海拔 2 750 m左右、山坡下部、坡位南及西南向受害较重。寄生天敌云杉瘿蚊长尾小蜂寄生率达 6 .39%。

The occurrence and the harm pattern of Dasineura rhodophaga(Coquillett)

The Dasineura rhodopaga (Coquillett) is a newly recorded insect damaging the terminal bud growing point of Picea asperata in Dingxi District.Of the 4000 hm 2 distribution area,667hm 2 area is seriouly affected.The average rate of plants suffering injury is 97 4%.The rate of terminal huds suffering injury is 83 7%.The insect density on shoots is 9 24 heads in 100 cm length,the insect index is 58 21.The harm pattern is:artificial forest,with higher density,forests of 2750 m above sea level, at the foot of hillside,or on the south and west south hillside are suffering heavier injury.The parasitic rate of parasitic natural enemy Torymus gansuensis is 6 39.