| 翻訳と辞書 |
| hemlock woolly adelgid ： ウィキペディア英語版 |
hemlock woolly adelgid
Hemlock woolly adelgid (''Adelges tsugae''), or HWA, is member of the Sternorrhyncha suborder of the Order Hemiptera and native to East Asia. It feeds by sucking sap from hemlock and spruce trees (''Tsuga'' spp.; ''Picea'' spp.). In eastern North America, it is a destructive pest that gravely threatens the eastern hemlock (''Tsuga canadensis'') and the Carolina hemlock (''Tsuga caroliniana''). Though the range of eastern hemlock extends north of the current range of the adelgid, it could spread to infect these northern areas as well. Accidentally introduced to North America from Japan, HWA was first found in the eastern United States near Richmond, Virginia, in the early 1950s. The pest has now been established in eleven eastern states from Georgia to Massachusetts, causing widespread mortality of hemlock trees. As of 2007, 50% of the geographic range of eastern hemlock has been impacted by HWA.
==Characteristics==
The presence of HWA can be identified by its egg sacs, which resemble small tufts of cotton clinging to the underside of hemlock branches. Hemlocks stricken by HWA frequently become grayish-green rather than the dark green of healthy hemlocks. In North America, the hemlock woolly adelgid asexually reproduces and can have two generations per year. In its native Asian habitat is a third winged generation called Sexupera; this generation's reproduction requires a species of spruce that is not found in the Eastern United States and therefore dies there. Between 100 and 300 eggs are laid in the woolly egg sacs beneath the branches. Larvae emerge in spring and can spread on their own or with the assistance of wind, birds and/or mammals. In the nymph stage, the adelgid is immobile and settles on a single tree.
The hemlock woolly adelgid feeds on the phloem sap of tender hemlock shoots. It may also inject a toxin while feeding. The resulting desiccation causes the tree to lose needles and not produce new growth. In the northern portion of the hemlock's range, death typically occurs four to ten years after infestation. Trees that survive the direct effects of the infection are usually weakened and may die from secondary causes.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
■ウィキペディアで「hemlock woolly adelgid」の詳細全文を読む
スポンサード リンク
| 翻訳と辞書 : 翻訳のためのインターネットリソース |
Copyright(C) kotoba.ne.jp 1997-2016. All Rights Reserved.
|
|