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调查100株落叶松,结果表明,兴安落叶松鞘蛾(Coleophora dahurica Flkv.)越冬幼虫和早春第四龄幼虫在树冠上的垂直分布规律是:由下层向上层虫口密度逐渐变小;下层虫口密度通常为上层的2倍以上,最多可达3.2倍。在枝条上的水平分布规律是:当年生枝段上虫数最少,前一年枝段上虫数最多,前二年枝段上次之;前一年枝段上的虫数常为当年枝段上的3倍以上。据幼虫在树冠上的分布规律,讨论了以下问题:①冬季或早春调查虫口密度时,顾及树冠形状,应用“加权法”原理在树冠的上、中、下层调查不同数量样枝,所得结果会更接近于实际;②样枝长度如过短(如:10cm、15cm),所得结果不应用于测报。
100 larches were investigated. The results showed that the vertical distribution of overwintering larvae of Coleophora dahurica Flkv. And fourth instar larvae in early spring on the canopy densities was gradually decreased from lower layer to upper layer, Usually more than 2 times the upper, up to 3.2 times. The horizontal distribution of the branches is: the annual number of branches on the smallest number of insects, the largest number of branches in the previous year, the first two branches last; the number of branches in the previous year often the number of branches On the 3 times more. According to the distribution rules of larvae in the canopy, the following problems were discussed: ① In winter or early spring, when the population density of insects was taken into account, the shape of the canopy was taken into account. Different numbers of branches were surveyed in the upper, middle and lower canopies by using the “weighted method” Closer to the actual; ② sample length is too short (such as: 10cm, 15cm), the results should not be used for measuring the newspaper.