• Natural History
• Firewood Alert!!! (PDF)
• How You Can Help
• Non-DNR Links

 
Natural History

A new threat to Michigan’s native flora has arrived. In summer 2002, the emerald ash borer (Agrilus planipennis) was discovered in southeast Michigan. Native to Asia, this species is responsible for the destruction of millions of ash trees in Livingston, Macomb, Monroe, Oakland, Washtenaw, and Wayne counties. It is unknown how the emerald ash borer arrived in Michigan, but experts think it may have been here as long as five years ago based on the age of affected trees.

The emerald ash borer belongs to a group of insects known as metallic wood-boring beetles (family Buprestidae). Adults are dark metallic green in color, measuring approximately one-half inch long and 1/16 inch wide, and are present only from May until late July. Larvae are a creamy white color and can be found under the bark of affected trees. The life cycle of this species spans one calendar year. Adults begin emerging in late May, with peak emergence in mid-June. Egg-laying occurs soon after emergence. After hatching, the borer goes through several larval stages, overwinters as a larva, and then pupates in the spring.

So far, the emerald ash borer has been found to infest ash trees (genus Fraxinus) only. In Michigan, this primarily includes white ash (F. Americana), black ash (F. nigra), and green ash (F. pennsylvanica). For the most part, trees greater than 2 inches in diameter and larger can become infested, and these can occur in woodlots as well as landscaped areas. While many trees affected by borers have been stressed or diseased, they will also infest healthy trees.

Infested trees exhibit top-down dieback, with 1/3 to 1/2 of branches dying the first year and the remaining canopy dying the following year. This is often followed by a large number of shoots arising below the dead portions of the trunk. Borers make a small (1/16 inch diameter) “D”-shaped hole when entering the tree and several distinct “S”-shaped tunnels may be present under the bark. Trees may also exhibit 2-4 inch vertical splits in the bark in response to larval feeding.

Although the emerald ash borer is a good flier, human activities are the primary cause of long distance spread. This includes moving infested trees, logs, and firewood. As a result, the Michigan Department of Agriculture (MDA) has quarantined all ash trees and ash wood products in the affected counties. This quarantine makes it illegal to move any ash trees or ash wood products larger than one inch in diameter outside these six counties. If you have inadvertently moved ash wood products (including firewood) out of the six-county area, we urge you to contact the Emerald Ash Borer hotline at (866) 325-0023.

 
How You Can Help

You can do your part by:

• Adhering to the quarantine
• Using local sources of firewood - Do not bring firewood from home.  If you have already brought firewood from home, do not take it back home and do not leave it -- BURN IT!
• Reporting any observations of borer activity to the Emerald Ash Borer hotline - (866) 325-0023

 
Non-DNR Links

Emerald Ash Borer (Michiagn Department of Agriculture)

Emerald Ash Borer (USDA Forest Service)

Emerald Ash Borer Website (Michigan State University Extension)