Local trees dying under insect-spread disease

Trees in our national forests are suffering under the effects of invasive insects. Photo by Brandy Carl.

Western North Carolina is home to multiple national forests, which see thousands of visitors every year.  The forests are popular destinations for students looking to hike, camp or just enjoy the views the mountains have to offer.  Over the years, some of our most beloved trees in these forests have begun to die under the influence of non-native invasive insects.

Trees such as hemlocks, laurels and walnut trees have been suffering under the effects of the diseases caused by various insects and the fungi or diseases they bring.  In fact, areas lined with dead trees along the Blue Ridge Parkway and Great Smoky Mountain National Forest show evidence of these insects and their effects on our forests.

Public Affairs Officer for the USDA Forest Service Stevin Westcott points to invasive insects as being one of the top sustainability issues.  Westcott has been working closely with the forest revision plan for the Nantahala-Pisgah national forests, saying the plan will impact how sustainability will be handled.

A variety of agencies within the forest service have taken on the battle against invasive species, including the State and Private Forestry Services and the Forest Health Protection branches, according to Eastern Forest Environmental Threat Assessment Center Director Danny C. Lee.

The EFETAC was created under the Healthy Forests Restoration Act to monitor and assess threats to our forests, including the threats from invasive species.

One of the most well-known invasive species impacting our forests is the hemlock woolly adelgid, named for the wool-like casing it uses to cover its eggs in and its feeding habits on hemlock trees.  The adelgids cover their eggs in said secretion meant to protect the offspring from threats such as pesticides, making them harder to control.  Signs of the adelgids’ arrival include graying needles, premature needle loss which leads to the loss of grown opportunities and death of the tree.

Sprays can be applied to trees with infestations, but North Carolina State University’s Department of Entomology recommends the spray be applied during winter.  During winter, growth of the hemlocks is slowed.  Applying the spray during a hemlock’s growth phase may hinder its development.  According to NC State’s entomology department’s insect notes, October also serves as a good time to spray as the eggs are going into their second phase of life and are more susceptible to the effects of the sprays.

This particular kind of adelgid was first discovered in the north around the 1920s.  It made its way to the south thanks to the wind and hitch hiking on birds, according to The National Park Service.

Hemlock woolly adelgids are not the only pests impacting our forests.  Lee also lists gypsy moths, the Asian longhorn beetle and the redbay ambrosia beetle as other important species.  Lee is also quick to point out that the insects themselves don’t always cause the damage.  In some cases, microbes or fungi living on the insects are what affect the trees.  The redbay ambrosia beetle is an example of such effects.

The disease laurel wilt comes from a fungus carried by the redbay ambrosia beetle.  Like the name implies, the disease causes trees in the laurel family to wilt.  The wilting occurs when the fungus prevents the trees from taking in water, according to the National Forest Service.

Areas where disease is common can be quarantined.  This means that lumber from these forests cannot be transported.  It also means that certain kinds of wood brought in to the forests by campers will no longer be allowed in.  Firewood brought in unknowingly is one of many ways these insects (and the diseases associated with them) spread throughout our forests.

These quarantines have been used for various diseases such as thousand cankers disease.  TCD is another disease associated with a fungus.  In this case, the walnut twig beetle spreads the fungus by laying eggs in the bark of walnut trees, according to the National Forest Service.   According to a press release from the North Carolina Department of Agriculture and Consumer Services, a recent outbreak of TCD has caused Haywood County to go under quarantine.

“The effectiveness of the quarantine depends heavily on the life cycle of the insect,” said Lee.

Insects that thrive in live trees will not survive once the tree has been cut, but insects that live in the heart of the tree can lay eggs that will hatch after the tree has been cut.  The emerald ash borer is one such insect.

The emerald ash borer lays its eggs deep within ash trees.  After the tree has become infested, it will die within five years.  Because the borer’s eggs are laid beneath the bark and the death of the tree is so slow, it is easy for campers to cut an ash for firewood without realizing it is sick.  This is also why ash trees are under quarantine in various parts of the nation.

Though quarantines can slow the spread of insects and the viruses associated with them, they cannot solve everything.  Studies suggest insects could also travel via birds.  Some may attach itself to a bird’s foot and travel with it.

“They’re [the insects] here because they’re successful,” said Lee.

Most of the insects discovered in our forests are not new by any means.  Rather, they’ve been seen in other parts of the country and have made their way to North Carolina.  If conditions are left exactly as they are now for six months to a year, the state could see a large increase in the number of pests.  Lee notes that it is unlikely any new pest will be discovered.

Some of the insects found in our area have come from other areas of the world, like Asia.  The climate in our section of the country is similar to the climate in parts of Asia, said Lee.  The insects first arrive in port cities, where goods have been brought in.  Because we don’t have the same predators as they do in Asia, their population can expand greatly.  Scientists are now trying to bring some predators over to the United States to control the spread of these invasive insects.

“We’re creating invasive pest problems for them too,” said Lee.

While other countries’ insects are invading our lands, our insects are invading theirs as well.

To help prevent the spread of invasive insects, community members and students alike can look for signs of invasion.  The National Forest Service puts out publications pointing out warning signs.  Students who notice an unusual change trees both on and off campus are encouraged to call the National Forest Service.  This is one way in which they can be aware of new species coming in.  Students can also help stop the spread of these insects by paying attention to what firewood they bring when camping.

When it comes to slowing the spread of invasive insects and monitoring the health of our national forests, everything can be summed up into one phrase: Knowledge is power.