By KEVIN WALKER
Michigan Correspondent

LANSING, Mich. — State officials have completed a survey for Hemlock Woolly Adelgid (HWA), an invasive species that poses a serious threat to the state’s 100 million hemlock trees.

More than 20,000 hemlock trees were examined for this exotic forest pest, which is a small, aphid-like insect that uses its long, siphoning mouthparts to extract sap from conifer trees. HWA is native to eastern Asia and was discovered in Virginia in 1951. It has since spread to Georgia and Maine, decimating hemlock stands across much of the eastern United States.

The Michigan Department of Agriculture (MDA), Department of Natural Resources and Michigan State University worked together on the effort after HWA was discovered at five locations in Harbor Springs in 2006 and 2007. Removal and destruction of infested hemlock, multiple insecticide treatments of adjacent trees and additional detection efforts preceded the surveys that were completed in June.

“We feel we have all of it at this point,” said Ken Rauscher, director of the MDA’s pesticide and plant pest management division.
Rauscher said hemlock provides good native habitat for many woodland animals, and that it’s become popular for large area landscaping.

The HWA survey is part of a broader effort on the part of state officials to monitor for a number of exotic pests this year. Since 2000, at least eight significant exotic plant pests have been discovered in Michigan or have been identified as a potential threat.

These pests threaten the state’s wheat, potato, soybean and stone fruit industries, as well as ash, beech, hemlock and pine forests.
International trade increases the likelihood that exotic creatures will be carried across borders into places where they have no natural enemies.

Some of these creatures can live in live plants and cut flowers, solid-wood packing materials such as crates and pallets and as hitchhikers in luggage and containerized cargo.

These creatures may spread, not only through natural dispersal, but also through manmade activities in agricultural and forest commodities such as ornamental plants, landscape trees and firewood.

“We want to try and identify pests early on and take action before they become established,” Rauscher said.

One potential threat is black stem rust, called UG 99, or Uganda 99.

“It can reduce wheat yields 50 to 60 percent,” Rauscher said.
Agricultural officials aren’t sure if Michigan’s wheat crop is resistant to UG 99, which makes it potentially a destructive fungus.

An example of a pest that’s already in the state is beech bark disease, a combination of an aphid and a virus that travels along with it.

“It’s killing off a lot of beech trees in the state, in northern and western Michigan,” he said.

Rauscher said the MDA is more reliant than ever on small federal grants to conduct these surveys.

“In recent years USDA has provided funding to do what I would call proactive survey work,” he said. That funding may or may not be forthcoming in the next federal budget, however.

One success story from these surveys is work to detect the plum pox virus. Rauscher said in 2006 this virus was found on one stone fruit tree in the southwestern part of the state. Much survey work was done to find more infected trees, but so far, no others have been found.

This means the disease was probably caught and surveyed before it had a chance to spread. This year the MDA is focusing its efforts on monitoring the movement of emerald ash borer and sirex woodwasp, as well as assessing the success of eradication measures against plum pox virus, in addition to the work it’s already done with HWA.

Rauscher urges anyone who sees anything unusual with a plant, which might indicate the presence of a strange disease or pest, call the MDA at 517-373-1087.