Michigan Hemlock trees infested by woolly adelgids

Apr 4, 2012

Flip over a branch of a hemlock tree, and you might spot them.

Nasty little critters in their cute woolly homes.

They're woolly adelgids (pronounced "ah-DELL'-jids").

They're native to Asia and have been spreading around the U.S. since 1924, and the bugs have infested forests along the east coast and the Smoky Mountain range.

They were spotted here in Michigan back in 2006, and again in 2010.

And today we have news that the sap-suckers have turned up in Michigan's southwestern corner.

More from the Associated Press:

The state Department of Agriculture and Rural Development announced Wednesday that hemlock woolly adelgid has been spotted in the New Buffalo area of Berrien County. One site had 41 infested trees and a second site had eight.

Authorities are surveying the area. All infested trees will be cut down, and nearby hemlocks will be treated with an insecticide.

The hemlock woolly adelgid has attacked trees in Emmet, Macomb and Ottawa counties since 2006. In each case, the infested trees were destroyed and there's been no evidence that the parasite has
spread.

The Michigan DNR says the invasive insect harms hemlocks by "sucking plant juices and by injecting a toxic saliva while feeding." Eventually, if left unchecked, the bugs will kill the tree.

In 2010, Michigan Radio's Jennifer Guerra spoke with Kelly Goward of the Ottawa Conservation District after the insect was found in that county.

She says the woolly adelgid can be spread through firewood or landscape nursery stock that gets moved around. She says HWA can also "be trasnferred naturally in the environment...they are kind of sticky, so they'll grab hold on a bird or as a deer brushes by a tree that's infected."

If you're concerned about your hemlock trees, you can inspect them by looking for a white cottony substance under the trees' branches.

The University of Kentucky's College of Agriculture says there are three common treatment options:

  1. insecticidal soap,
  2. imidacloprid soil injections,
  3. and biological control using tiny beetles native to the Pacific Northwest that feed on hemlock woolly adelgid. 

And the Michigan DNR has these suggestions for curbing the spread of woolly adelgids:

  • Carefully monitor your hemlock trees and report any infestation immediately, early detection is critical.

  • Since Hemlock Woolly Adelgid is primarily spread to native trees from planted stock, carefully inspect any purchased trees prior to planting.

  • Do not bring hemlock trees into Michigan from infested areas