摘要
在夏伐后的桑园,根据桑蓟马虫口密度的不同,将桑叶受害水平划分为5个等级。利用不同等级的桑叶饲育家蚕(芙蓉×湘晖),得出在桑蓟马不同为害水平下桑叶和蚕茧的产量,建立了桑蓟马虫日指数(X)与桑叶产量损失率(Ym)和茧层量损失率(Ys)的关系式分别为: Ym=-0.00532+0.00029X(r=0.9907) Ys=-0.00139+0.00011X(r=0.9853) 根据当地桑树害虫防治与蚕茧产品价格的有关经济数据,得到桑蓟马在早秋蚕期间的防治指标为3级受害水平,即桑叶受桑蓟马为害的面积占全叶面积的1/2以上,受害部分的叶脉出现红褐色斑点。考虑大草蛉对桑蓟马的捕食作用,则桑蓟马防治指标可定为4级受害水平,即叶片受害面积占全叶的1/2～3/4,叶缘向上卷起。
The injured mulberry leaves caused by mulberry thrips Pseudodendrothrips mori Niwa were divided into five levels, according to the five corresponding densities of the thrips in the mulberry orchard after summer-cutting. Silkworms Bombyx mori Linnaeus of variety Furong X Xianghui were reared on the mulberry leaves of different injury levels. The relationships of the insect-day index (X) of the thrips and the yield loss of mulberry leaves (Ym) or the loss of silkworm cocoons (Ys) were developed respectively as following two equations:
Ym=-0. 00532 + 0. 00029X (r = 0. 9907**)
Ys =-0.00139 + 0. 00011X (r = 0. 9853**)
According to the cost of thrips control and the price of silkworm cocoons in Nanchang, Jiangxi Province, the economic threshold (ET) of this insect pest in early autumn was determined as 538 insect days, belonged to the third injury level of mulberry leaves with the injured area less than 1/2 of the whole leaf and exhibited many red spots on the leaf surface. In consideration of the natural suppression of Chrysopa septempunctata Wes-mael to the thrips populations, the ET might relax to 624 insect-days, i. e. the fourth level of injury with the injured area about 1/2 to 3/4 of the whole leaf and its edges curled upward.
出处
《植物保护学报》
CAS
CSCD
北大核心
2000年第1期37-41,共5页
Journal of Plant Protection
基金
江西省自然科学基金(943027)
