Environmental Issues

An invasive species can be defined as a species that causes environmental and economic harm to human beings, plants and animals (Simberloff, 1996). Hemlock wooly adelgig is aphid- like small insect approximately 0.8 mm in length. Its oval in nature with reddish brown color or purple and black in color.

This species can be identified by dry wooly wax substance found on its body as it matures. The wooly was substance is almost 3 mm or more in diameter and it is used for protecting its body as well as its eggs from enemies (Cheah, et al 2000). The species is scientifically known as adelges tsugae. It was introduced around 1951, near a place called Richmond in eastern part of U.S where it infested almost halfway of the western and mountain hemlock trees. It was later reported in Virginia in 2005, then to other places like Georgia, Maine, among others. After its introduction in eastern America, the species was said to have led to extensive decline in trees in the area (U.S.D.A, 2005). The mode of dispersal of hemlock wooly adelgig is either by wind, birds and other mammals that come into contact with the species.

Hemlock wooly adelgig is a dangerous species as it devastating ecological effects. Some of the problems of hemlock are as follows

It causes faster decline in health of the trees which may be followed by quick death and if not controlled immediately, the tree can die in a period less than a year. The introduction of adelgig did not only bring threats to hemlock tree but also to species like bird which use the tree for nesting purposes, food sources. It also affected many trees that uses hemlock stands as its shelter or habitat

It affects the regulation of water temperatures in area they are found

It also affects the survival of various species of animals.

It affects other services of the ecosystem. For example, it leads to greater changes in the cycle of nitrogen among other problems.

From the above effects, it is evident that this invasive species affects the whole ecosystem (Cheah, et al 2000).  

Fighting the dangers of invasive species will be the most important and cost effective strategy for the nation to deal with adverse effects experienced in the ecosystem by introduction of the invasive species. However, it has increasingly proved difficult to control Hemlock wooly adelgig due to its fluffy body surface.  Two most important methods that have been used in controlling the species include mechanical control and use of predators (Simberloff, 1996).

Mechanical control involves the use of different types of machines. For instance in Florida they use volunteer convicted labourforce to cut paperbank trees and this helps eradicate the tree (Simberloff, 1996). In case of Hemlock wooly adelgig, eggs and crawlers are dislodged from hemlock twigs by wind and sometimes by rain. This means that streams of water can be used to dislodge eggs and crawlers especially between April and June and also clipping away twigs infested with the species can control the species (Cheah, et al, 2000).
Most predators are ineffective in controlling hemlock adelgig although there are some exotic insects that were identified which are natural predators of the species. For instance beetle is one of the most effective predator of hemlock wooly adelgig (HWA), it has also been very vital in checking the population of HWA in control in Japan. It suits control of HWA due to its various characteristics like being mobile and feeding mostly on HWA (Cheah, et al, 2000).