There are several strangers in a strange land here in North Carolina. In fact, the majority of our worst forest pests are non-native invasive species. In the 1990s, the tree-killing hemlock woolly adelgid was first found in N.C. and can now be found in every county in the state where hemlocks are native. Hemlock mortality resulting from this invasive insect is astounding. In more recent years, the emerald ash borer swept through much of our state in a relatively short period, leaving dead ash trees in its wake. We are also battling invasions of gypsy moth, the walnut twig beetle and thousand cankers disease, the redbay ambrosia beetle and laurel wilt, and balsam woolly adelgid… to name a few.
But the U.S. isn’t always on the receiving end of this. Global trade and movement of goods and people are a worldwide phenomenon, so it’s no surprise that the invasive issue goes both ways.
The fall webworm, for example, is a defoliating insect native to North America, including North Carolina. Here, it is primarily an aesthetic concern, known for the unattractive webs that show up on the tip of branches in the late summer. In the 1940’s, this defoliator was accidentally introduced to eastern Europe and it has since spread throughout most of Europe and into China, Korea, and Japan. In this introduced range, the fall webworm has become an aggressive defoliator and is a major pest in orchards. Some say that the fall webworm in Europe is a worse pest than the European gypsy moth is here.
Another pest that we’ve shared with the world is the pinewood nematode, the causal agent of pine wilt disease. Pinewood nematode is native here and causes relatively minor damage to our native trees. However, in its spread to parts of Europe and Asia, it has emerged as one of the most damaging forest pests of conifers worldwide. Because of this, wood logs and exports with softwood packaging materials require screening for the nematode prior to exportation.
The threat from invasive species will likely only increase with ever-increasing globalization. As stewards of the planet, we should all do our best to mitigate spread where we can. Reducing spread from the U.S. to other countries is a good way to be a good neighbor and the Plant Industry Division already inspects exports that may harbor pests.
Reducing spread of invasive species that have already invaded is another big step and one that each one of us can do. Many invasives are accidentally spread within firewood or untreated wood products, which is why buying and/or burning local firewood is recommended. Buy local firewood, burn local firewood!