HIGH COUNTRY — While there are many interesting bugs in the High Country, not all are good for some of our plants. This is especially true for those insects that are not native (exotics), sometimes referred to as invasive. Because many of our plants have few natural defenses against exotic insect invaders, such as predators that feed on the bugs, or parasites that kill them, the result in some cases is serious damage and death to native plants. While a previous article I wrote discussed the non-native and annoying marmorated stink bug and multi-colored Asian lady beetle, other potentially invasive bugs in our area are much more concerning.
Many are no doubt aware of the damage to, and often ultimate death, for many of our Carolina and Eastern (Canadian) hemlocks caused by the hemlock woolly adelgid, Adelges tsugae. You may have seen the many small, white, cotton-like “blobs” on the tree branches where the needles attach, which in fact are a covering for the bodies of this sap-sucking invasive insect. The adelgid originated from Asia (possibly Japan too) and was found in the U.S. Pacific Northwest many years ago.
In the 1950s this insect was discovered in Virginia and has slowly spread throughout the Eastern U.S. They have an interesting life cycle. Females (no males are needed to make new adelgids!) lay eggs that hatch into wingless “crawlers”, which then move about the tree feeding on branches where they eventually produce their white covering. Because females produce many eggs, the adelgid population can be enormous on an individual tree. To make matters worse, there is more than one generation produced per year.
Chemicals can be used to protect individual trees, but this is not a practical or indeed safe solution for large numbers of trees. Though hemlocks possess few natural defenses against the woolly adelgid, there is some good news. Researchers are finding success rearing and releasing in very large numbers small beetles that eat the adelgid, reducing their populations and in some cases resulting in tree recovery. If successful, over the long term the beetle-releasing biological control strategy could provide a way for our hemlocks to survive and thrive in the years to come.
The emerald ash borer, Agrilus planipennis, gets its name from the metallic green adult beetle. Though handsome in appearance, this bugs effects on our native ash trees is devastating. A native of Asia, this wood-boring insect first appeared in the upper midwestern US but has since rapidly spread. Unlike the sap-sucking hemlock woolly adelgid, the emerald ash borer feeds under the tree bark. Adults are found in spring feeding on the ash leaves and after mating the female lays eggs. The young (larvae) and bore into the bark, where their feeding cuts off the food supply throughout the tree, eventually resulting in tree death. Distinctive “galleries” are carved into the wood by the munching insects. Larvae overwinter in the tree and in spring produce a pupa that develops into an adult. The metallic beetles bore out of the tree leaving a visible hole, begin to eat, and the cycle continues.
Attacked trees may succumb in a few years (or sooner), leaving behind the tell-tale galleries in the wood as the bark peals away. Ash trees possess few natural defenses against the emerald ash borer, although researchers are exploring releasing small parasitic wasps that kill it. You may notice the next time you’re camping warning signs about not taking firewood from where you are into other areas. That’s because the emerald ash borer can easily be transported to places it is not found through the wood. It is especially important to take these warnings seriously to prevent further spread of this damaging insect.
Though the hemlock woolly adelgid, and more recently the emerald ash borer, have become established unwelcome invasive insects, we need to be diligently watching for other concerning invasive bugs that may soon find our area home. This is especially true for the plant-sucking spotted lanternfly, Lycorma delicatula. Also a native of Asia, this highly damaging bug threatens agricultural plants (including fruit trees) and especially grapes. Originally found in Pennsylvania, and established now in parts of nearby southern Virginia, the spotted lanternfly’s incidence in North Carolina just to our east is currently limited but likely to increase in the future. Fortunately reports of this serious pest in the High Country are not known at this time.
Though unwelcome, invasive insects are becoming part of our local insect communities through unfortunate introductions, and by the great capacity for bugs to move around. When spring arrives watching out for the bugs discussed in this article, and reporting incidents of new invaders, will assist in helping state and local agencies develop good policies to hopefully control their impacts. Sources and additional information on the insects in this article may be found using the searchable website https://content.ces.ncsu.edu
Dr. Ray Williams is a native of Asheville, and Professor Emeritus in the Department of Biology at Appalachian State University, where he taught for 25 years. What he tried to instill in his students is the fascinating lives of insects, which he continues to research and write about in retirement. He lives in Boone with his wife, Beverly, and has two children in college. He will write a semi-regular column on local insects in the area. For questions or comments, email email@example.com
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Thanks to modern technologies, you and more people are reading the Watauga Democrat than ever before. Freedom of the press is essential to preserving democracy: But a free press isn't free. It takes significant resources for Mountain Times Publications' 8 full-time journalists and editors to provide credible, fact-based and ethical journalism in the High Country. So, we are asking you to join our advertisers and print subscribers in supporting local journalism with your dollar. Your financial support will help sustain these services that you use to inform your decisions and engage with your community.
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