Common Tree Pests in Michigan and How to Deal With Them
Michigan’s forests are facing a multitude of threats. Whether they’re from invasive pests or diseases, these pests impact the trees that wildlife depends on for shelter and food.
Beech bark disease is killing beech trees in the state’s upper and lower peninsula. Watch for black spots on leaves that could be the first signs of the fungus.
1. Brown Marmorated Stink Bug
The brown marmorated stink bug has killed tens of millions of apple and peach trees in the East, and it may be coming to Michigan. It also preys on stone fruit, tomatoes and field corn, as well as a variety of ornamental woody plants, including maple, birch and hemlock.
This bug, Halyomorpha halys, is easy to recognize: it’s a mottled-brown shield insect about 1/2 inch long with alternating black and white striping on its abdomen. Young bugs, called nymphs, look orange to red and get darker as they mature.
The Asian longhorned beetle and the emerald ash borer are other real-life villains that have caused billions of dollars worth of damage to crops, forests and property since they arrived in Michigan. These insects feed in tunnels, or galleries, that girdle the tree and kill it. If you’re looking for top-notch services, simply click or visit this link to experience excellence firsthand: https://grandrapidsmitreeservices.com/services/tree-trimming/
2. Emerald Ash Borer
The invasive emerald ash borer (Agrilus planipennis) is devastating ash trees in Michigan and other states. This metallic-green insect and its larvae tunnel under the bark, disrupting the flow of water and nutrients and eventually killing the tree.
In a Brighton lab — the only one of its kind in the United States — scientists are raising four species of stingless wasps native to Asia and Russia that hunt down and kill emerald ash borer eggs and larvae. They’re testing whether the wasps can control an infestation that has wiped out millions of ash trees across Southeast Michigan and North America.
The emerald ash borer most likely entered the country in wood crating or pallets brought to Detroit in cargo ships from the pest’s native China. It has since spread to dozens of states, creating a plant health emergency that experts say will ultimately lead to widespread ash tree mortality.
3. Pine Leaf Beetle
While the mountain pine beetle is more common in eastern North America, it has become one of the most destructive forest pests in the West and could threaten Michigan’s pine trees if introduced. Its rapid spread is due to hot summers and mild winters that encourage outbreaks.
When an overwintering beetle reaches its target tree, it bores feeding tunnels (called galleries) through the bark. Eventually, the beetles kill the tree by causing internal wounds and sap leakage.
You can identify a beetle attack by pinhead-sized holes in the bark. Infested trees may also have discolored needles that fade to yellow-green, red or brown and eventually fall off the tree. If you see these signs, spraying your pine trees with preventive treatments is the best way to protect them.
4. Cherry Leaf Beetle
Infestations result in premature defoliation with negative influences on production and vigor. Leaves become yellow with purple spots and are covered with a whitish mold.
The disease is caused by a fungus that ruins apples and can also attack other trees. Symptoms include olive-green spots with dark brown or black borders.
This pest has been found in the state’s hemlock forests and could have devastating impacts. If HWA establishes in Michigan, it will kill the vast majority of hemlocks. HWA can be transported to new areas in walnut logs, firewood and woodworkers’ staves.
Keep an eye out for signs of HWA like holes in trees larger than a pencil and piles of sawdust beneath them. Report any suspicious activity. A fungicide can help control the damage.
5. Hemlock Woolly Adelgid
Hemlock Woolly Adelgid (HWA) is an invasive pest from Asia that has killed hemlocks in eastern United States. These small insects girdle trees at every stage of life, including needles and branches, by creating tunnels under the bark called galleries. They have been found in Michigan and threaten our state’s estimated 170 million hemlocks, which provide shade, winter cover, food for birds and other wildlife and support the steep, sandy dunes that are crucial to the state’s coastline.
Hemlocks can be distinguished from pines and spruces by their cone or egg-shaped shape, drooping branches and flat needles. HWA can be found in hemlocks overwintering by looking for a round, white mass of waxy material on the undersides of branches.
Help the State find HWA by observing your hemlocks this winter and reporting them if you see them. Check out this link for current HWA infestation maps.