The bug that ate Christmas


The balsam wolly adelgid is an invasive species known to kill popular fir tree species. Image by the Forest Service of the USDA.

Wild populations of Canaan and Fraser firs — some of the nation’s most popular and iconic Christmas tree species — have been deteriorating along the southern range of the Appalachian Mountains. Known for their dark evergreen color and thick branches, these trees are slowly losing their needles and turning yellow in many parts of West Virginia, Tennessee and North Carolina since an invasive insect was discovered there in the mid-1950s. The culprit? A tiny bug called the balsam wolly adelgid.

The wolly adelgid covers the branches of these Christmas trees with fuzzy waxy balls that contain its eggs. They are about the size of a tick and feed on the branches and trunks of trees by puncturing the bark and secreting chemicals that cause them to deform. The bugs are all female and are able to reproduce without mating, making them extremely hard to remove. On contained commercial tree farms, expensive pesticides are used to thwart these harmful bugs. The use of pesticides in the wild, however, risks killing much more than the tiny wolly adelgid, and so the bug is destroying enormous quantities of hemlocks at an alarming rate. The loss of large quantities of the Christmas trees can have a huge effect on the ecosystem of forests. These trees play a crucial role in keeping the floor of forests cool by providing dense shade to forest floors.

In the Great Smokey Mountains National Park, park rangers are trying to cut back on the invasion of the wolly adelgid by introducing a predator beetle who eats the eggs of the small pests. Trees like the Canaan and Fraser firs are very common from Canada through North Carolina but are especially at risk in areas where temperatures are rising, allowing insects like the wolly adelgid to proliferate.

Randall Edwards, a spokesman for the Nature Conservancy of Ohio, says that the invasion of the wolly adelgid needs attention because it’s an example of a larger problem that forests are facing in the U.S.
“It could be that the only place you see the Canaan fir in the future is on tree farms,” Edwards said. “And we think that would be unfortunate.”

H/T Jordan Vesey