Studies on the method defining the degree of threat to pine (Pinus sylestris L.) cultivations by Brachyderes incanus L.)

摘要

The distribution of needles damaged by Brachyderes incanus L. was investigated on Pinus sylvestris trees. it was found that the percentage of damaged needles on the branches of the highest verticil does to give an exact index of the damage degree of all needles on the tree. A better index of damaged needles can be obtained by calculating the percentage of damaged needles on the branches of the lowest verticil. The most precise index is given by the length of the damaged parts of the needles in relation to their total length.