论文部分内容阅读
1954年以后美国马里兰州有一种松叶蜂盛行为害,最近在北卡罗里纳及佛吉尼亚的滨海平原及皮德蒙特区更形猖獗。1955年叶部被食的松林面积约有325,000亩(131,527.5公顷),自此以后美国林业局及各州政府曾年年实行地面的及航空的虫情调查,以决定此虫迅速蔓延的范围和严重程度。据1959年调查,约有1,400,000(566,580公顷)多亩的佛州松(Pinus vir-giniana mill.)、脂松(P.rigida mill.)和短叶松(P.
After 1954, the United States of America Maryland has a pine needles Sheng Sheng behavior, recently in North Carolina and Virginia’s coastal plains and Piedmont more rampant. Since 1955, approximately 325,000 acres (131,527.5 hectares) of pine forest have been eaten in the foliage. Since then, both the United States Department of Forestry and the state governments conducted ground-based and aerial insect surveys every year to determine the extent and severity of the rapid spread of the insects degree. According to the 1959 survey, about 1,400,000 acres (566,580 hectares) of Pinus virginiana mill, P.rigida mill. And P. gmelinii (P.