Invasive insects can cause serious damage if not kept under control.
In Michigan, beetles and tree-dependent insects dominate the invasive species list.
Species that are not native and also have the potential to harm human health or to harm natural, agricultural or silvicultural resources can be listed as prohibited or restricted by the State of Michigan.
If a species is prohibited or restricted, it is unlawful to possess, introduce, import, sell or offer that species for sale as a live organism, except under certain circumstances, the Michigan DNR says.
Here are 6 invasive Michigan insects to watch out for:
Asian Longhorned Beetle
Why we care: This large, showy beetle was accidentally introduced into the U.S. on several occasions, probably in wood crating or pallets shipped from Asia. Larvae feed in tunnels (called galleries) in the wood of tree branches and trunks. The galleries can cause branches or trees to break and will eventually kill the tree. North American trees have little or no resistance to infestation.
What is at risk? Maple trees are the Asian longhorned beetle’s (ALB) favorite host. More than 1 billion maple trees grow in Michigan. ALB can attack and kill many other tree species, including poplar, willow, sycamore, and horse chestnut.
The threat: ALB populations are known to be present in areas of southern Ohio, Massachusetts and New York. ALB can be transported into new areas in logs and firewood. If ALB is not eradicated and populations spread across North America, the economic and ecological impacts would be enormous.
What could happen in Michigan? If a new ALB infestation is found, federal and state officials will begin survey and eradication activities, including removing and destroying all infested trees. Tree removal is unpleasant, but it has been successful in eradicating ALB populations in New Jersey, Chicago and Toronto. Early detection is critical.
Brown Marmorated Stink Bug
- Mottled-brown, shield-shaped bug ½ to ¾ inches in length.
- Legs and antennae are banded brown and white.
- Alternating black and white pattern along edges of the abdomen.
- Young bugs, or nymphs, have orange to red coloration.
- Adults emerge in late April to early May, laying eggs from May through August.
- Bugs seek overwintering sites, including indoor areas, beginning in September.
Habitat: Found on tree fruits and small fruits, vegetables, ornamental plants and legumes. Bugs overwinter in warm, sheltered areas including buildings.
Native Range: Southeast Asia
U.S. Distribution: Brown marmorated stink bug has been detected in 42 states including Michigan.
Local Concern: The brown marmorated stink bug has been shown to affect yields in fruit, nut, legume and vegetable crops in the Eastern United States. The brown marmorated stink bug can also affect ornamental plants and be a nuisance in indoor environments where they overwinter.
Emerald Ash Borer
- Bright, metallic green with purple abdominal segments under its wing covers
- Length of adult beetle is approximately ½ inch
- Can fit on the head of a penny
- Larva are worm-like
- Create D-shaped exit hole in the tree
Habitat: Urban, suburban, and rural forests
Diet: Adults feed on the foliage of ash trees, while the larvae tunnel and feed on the underside of the bark and cut off the transportation of nutrients and water to the tree.
Native Range: Eastern Russia, Japan, Northern China, and Korea
Local Concern: Since the first discovery in Michigan in 2002, this invasive beetle has killed tens of millions of ash trees in Michigan, both in forests and in neighborhoods. Adults typically only fly about ½ mile. On their own, this species doesn’t spread very far. The real concern with spread is the relocation of infested firewood to non-infested areas. Don’t move firewood!
Means of Introduction: The emerald ash borer most likely arrived in the United States via solid wood packing materials arriving from Asia.
- Gypsy moth caterpillars emerge from tan, fuzzy egg masses in April and feed on leaves through late June.
- Caterpillars are hairy, with a yellow and black head and 5 pairs of blue spots, followed by 6 pairs of red spots.
- Mature caterpillars are 1.5 to 2 inches in length.
- Leaf debris and small, round frass found under trees are indications of gypsy moth infestation.
- Male moths’ wings have a wavy pattern of brown to dark-brown and span 1.5 inches.
- Female moths are larger than males and do not fly. Wings are white to cream with wavy black markings.
Habitat: Most often feeds on the leaves of oak and aspen but can also be found on hundreds of other plant species.
Native Range: Europe and Asia
U.S. Distribution: Northeastern U.S. west to Minnesota
Local Concern: Gypsy moth caterpillars defoliate trees, leaving trees vulnerable to diseases and other pests, which may lead to tree mortality. During large outbreaks, debris and frass from feeding caterpillars can be disruptive to outdoor activities.
Pathways of Spread: Though female moths do not fly, small caterpillars can be blown by the wind to other trees. Gypsy moth egg masses and pupae can be unknowingly transported on firewood, vehicles and recreational gear.
- Adult beetles are about 3/8 inch in length, with a bright metallic green head and body and metallic brown wings.
- Legs are darker green.
- Twelve tufts of white hairs surround the edges of the abdomen.
- Grubs or larvae are about 1/16 to ¼ inch in length, white, with three pairs of legs.
- Adult beetles emerge in June or July and feed throughout the summer.
Habitat: Grubs live underground, feeding on grass roots, leaving brown patches in lawns. Adults feed on the foliage, flowers and fruit of hundreds of plants including tree fruits, small fruits, ornamentals, garden vegetables, soybeans and corn.
Native Range: Japan and Eastern Russia
U.S. Distribution: The Japanese beetle is established in nearly all Eastern states, with populations detected in some states west of the Mississippi.
Local Concern: Japanese beetle grubs damage lawns and turf grasses. Beetles skeletonize leaves and flowers of ornamental plants and trees and can damage crops.
Hemlock Woolly Adelgid
Why we care: These tiny insects secrete white wax as they feed on sap from hemlock shoots and branches. Hemlock woolly adelgid (HWA) feeding can kill needles, shoots and branches. Over time, growth slows as trees become less vigorous and trees may take on a grayish-green appearance. Infested hemlocks, especially large, old trees, are often killed when other stress factors, such as drought, affect trees.
What is at risk? More than 100 million mature hemlocks grow in Michigan. Hemlocks provide important habitat and winter cover for many wildlife species.
The threat: HWA populations are common in many eastern states, including Pennsylvania. Eggs and very young adelgids can be carried by birds and can be moved on hemlock nursery trees, logs or firewood.
What could happen in Michigan? Much of the state's hemlock resource is relatively old and very vulnerable to HWA. If this pest becomes established, most of these trees will be killed.
Non-Watch List Species
Non-Watch List species should be reported using the Midwest Invasive Species Information Network (MISIN) online reporting tool or the MISIN smartphone app. Alternately, these species can be reported to the Cooperative Invasive Species Management Area for your region or your local conservation district.
Property owners may elect to control these species on their own property using best management practices.