Frequently Asked Questions

Nobody knows for sure, but we think they came over on cargo ships from China in ash crates.

It will only attack ash trees. Mountain ash is not a true ash and is therefore safe from EAB.

It all started in Michigan back in 2002. As of June 2025, EAB is now found in seven South Dakota counties, 36 other states, and the six Canadian provinces.

EAB is difficult to detect when it first infests a tree. The tree can host EAB for 3-5 years before symptoms become noticeable to anyone, including trained professionals. The first indication that a tree is infested is yellowing and thinning of the foliage. Later, often within the same season, the upper branches will begin to die back. This progressive die back continues until the tree dies, a process that may take one to several years. Sometimes the tree forms epicormic sprouts — long, thin, fast-growing shoots along the trunk during the advanced stages of decline. Another indicator of an infestation is the presence of woodpecker activity on the declining tree. These birds are searching for the borer larvae that are inside the tree. Woodpeckers will search for any insect beneath the bark so this is not a definite indicator of the insect. The best indicator that the tree is infested with emerald ash borer is the presence of small D-shaped holes on the bark of the tree. These holes are created as the adult emerald ash borer emerges from the tree or log and flies to another tree to lay eggs. These 1/8-inch D-shaped holes are not usually present on the lower trunk until the tree is near death or has already died. A tree can be infested for several years before the holes occur low enough on the trunk to be detected.

Adults are about half an inch long, slender, and a metallic green color. They normally emerge from ash trees during June or July and leave behind D-shaped exit holes about 1/8" in size. The larvae are about 1 and 1/4" long, white, and segmented.

They begin emerging from infested trees and wood in early summer. The adults fly to a nearby ash and deposit eggs on the bark. The larvae hatch in about a week or two, burrow into the inner bark of the tree, and begin to feed. The larvae are legless, white, segmented and will reach a length of 1-inch long by fall. The larvae create S-shaped galleries or tunnels just beneath the bark and these galleries are packed with a saw-dust like material. The S-shaped galleries cut off the movement of food from the leaves to the roots and this interruption results in the tree's decline and eventual death. The larvae form a whitish pupa just beneath bark in the spring and the newly formed adult emerges in a few weeks.

Ash firewood brought into South Dakota from other states may contain the larvae of the emerald ash borer. Since the adults emerge from infested wood during the summer months, any logs or firewood containing the larvae can become the source for a new infestation. Campers bringing firewood from outside the state may be inadvertently carrying this destructive insect, or other recently introduced pests such as the banded elm bark beetle. It is important that all firewood brought in from outside the state be promptly destroyed or burned.

Any suspected infested trees should be brought to the attention of your local forester. They may need to inspect the tree to determine if it is infested with the beetles. In many instances the tree may be dying from other problems or insects. You can contact your local forester here.