Tuesday, Sep 25, 2018
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Matt Markey

No end to the parade of pests killing our trees

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Our-troubled-trees

Beech leaf disease is the latest threat to Ohio's trees. First discovered in Lake County in 2012, its symptoms include dark striping or banding on otherwise healthy-looking leaves, shriveled, discolored or deformed leaves and reduced leaf and bud production.

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North America’s trees have had to endure a seemingly endless cavalcade of diseases and dastardly creatures that have crippled some species, and nearly wiped out others. The list of assailants is a real murderers’ row of bugs and blights.

Did you ever wonder why Elm Street often has no elms? Two strains of Dutch elm disease slipped into the U.S. on logs shipped from Europe and our first elms started to die near Cleveland in 1930. Sixty years later, more than 75 percent of the elms on the continent were gone.

The American chestnut tree grew to a stately 100 feet tall and there were billions of them thriving as the 19th century ended. Chestnut lumber was prized for its versatility, straight grain, and rot resistance, making it ideal for fence posts and barn beams, as well as a prime material for making musical instruments and fine furniture.

In 1904, a fungal pathogen with the godawful name Cryphonectria parasitica arrived surreptitiously from Asia and after first being spotted in New York, it spread devastation from sea to sad sea by attacking the cambium layer and effectively choking the tree to death. By 1950, the American chestnut tree was essentially eliminated from our forests, with the best estimate stating that three billion trees were lost to the blight.

Another undocumented assassin from Asia snuck its way in much more recently. The Asian longhorned beetle was first seen in New York just over 20 years ago, and its tactics are similar to those employed by other killers — tunneling into trees and strangling the passage of water and nutrients. This insidious insect has claimed birch, willow, maple and horse chestnut trees but appears to have an even more diverse range of host victims. A frightening report by the USDA Forest Service predicted that allowing the Asian longhorned beetle to become established throughout the U.S. could result in the death of 30 percent of all urban trees, a an economic loss estimated at nearly $670 billion.

The list goes on, akin to reading the greatest hits from the Journal of Infectious Diseases put out by Oxford University Press. A messy blight called Thousand cankers disease attacks black walnut trees and wields a double-whammy, with the walnut twig beetle and a fungus it transmits teaming up to kill these trees that are highly valued for their lumber. Sudden oak death (SOD) is a soil-born fungal disease that has killed millions oaks in the coastal areas of northern California and southern Oregon. Numerous butternut populations are being destroyed by a different exotic fungal disease named Sirococcus clavigignenti-juglandacearum, which is another fatal canker.

Striking closer to home for many in the Midwest has been the notorious emerald ash borer, an exotic beetle with a metallic coat, bulbous eyes and a bullet-shaped body that looks like it might have been a reject from a Marvel sketch pad. This evil half-inch-long machine of destruction no doubt was a stowaway in wooden shipping materials from Asia that allowed it to land in the Detroit area. Ash trees there started dying in 2002 as the larvae fed on the inner bark, slowly and methodically choking the life out of the tree. When the dead ash trees soon dominated the landscape in certain areas, they looked like skeletons surrounded by other fully foliated species, and we stopped counting at hundreds of millions of lost ash.

Now we are facing two additional demons. Ohio forestry biologists are urging the citizenry to be on the lookout for beech leaf disease, which was first discovered in Lake County in 2012 and has rapidly increased its footprint across the northeastern corner of the state. The experts are scrambling, since infestations have spread to nine Ohio counties and parts of New York, Pennsylvania, and Ontario, but as of now we don’t know the causal agent for this disease.

“We really have no idea where it came from, so it’s all speculation at this point,” said Tom Macy, a forest health program administrator with the Ohio Department of Natural Resources, Division of Forestry. “There’s really not much we can tell folks now other than to let them know what the signs are, and ask them to report it, to tell us where you are seeing it.”

The telltale calling cards of beech leaf disease include dark striping or banding on otherwise healthy-looking leaves, shriveled, discolored or deformed leaves, and reduced leaf and bud production. Macy said the disease is especially devastating to younger trees, but at this point, no infected tree has recovered from the disease.

“All we have at this point is anecdotal information, but in the areas where it is heavily impacted, it looks like lot of understory trees are killed,” he said. “It is still so new, but it is getting worse in the areas where it has been around the longest. People need to be aware of what to look for, and to notify us as soon as they see it.”

To report BLD, contact Macy at the thomas.macy@dnr.state.oh.us email address or use the BLD section of the NE Ohio Parks app available at the parkapps.kent.edu website.

In Michigan, a lot of attention is being centered around a tiny invasive insect called the hemlock woolly adelgid that could decimate the state’s 170 million hemlock trees. This pest from Japan targets the eastern hemlocks that spread out in wide swaths across the northern Lower Peninsula and most of the Upper Peninsula. These coniferous trees are a vitally important part of the forest, assisting in keeping its streams cool and clean, and providing shelter for wildlife such as deer and nesting birds.

This killer is so tiny it is barely visible to the naked eye, but its homicidal methods are highly effective. The hemlock woolly adelgid looks like a black aphid and feeds by piercing the branches, removing sap as it slowly slays the tree. The best sign that indicates a likely infestation are the cotton-like, waxy white balls hanging from the hemlock branches. These are the egg sacs of the hemlock woolly adelgid.

Biologists theorize that this pest made its way here hidden in a shipment of hemlock that arrived in Virginia from Japan nearly 70 years ago, and then spread a swath of destruction across the forests of the Appalachians on its march toward Michigan. The first documented infestation in Michigan took place in 2006 Emmet County, a bit south of the Mackinac Bridge, and despite efforts to cut off the movement of this invasive insect, it spread to Macomb and Ottawa counties in 2010, Berrien County in 2012 and Allegan County in 2013.

Intensive efforts to remove infected trees and treat the surrounding area with insecticides had some success, but in 2015 new cases showed up in Ottawa County and in southern Muskegon County.

“Given the checkerboard pattern of hemlock woolly adelgid across the western counties, it is likely that multiple introductions of infested tree stock are responsible,” said Scott Lint, a forest health specialist with the Michigan Department of Natural Resources. Biologists report that the infestations can spread via wind, wildlife or by vehicles that brush against infested trees.

Michigan is employing an all-hands-on-deck approach to battling the hemlock woolly adelgid, with a consortium of scientists and field technicians from the Michigan departments of Natural Resources and Agriculture and Rural Development, Michigan State University, the U.S. Department of Agriculture’s Forest Service, and the Ottawa County Parks and Recreation Department working together as the Hemlock Woolly Adelgid Coordinating Committee.

“Our current strategy is based on the knowledge we have now,” said James Wieferich, a technician with DNR Forest Resources Division. “If adelgid infestations are limited to the areas we have surveyed, we can create a barrier to sever the infestation from areas farther north that are not infested and then stair-step treatment down to the southern limits (of the infestation).”

For more information about Michigan’s eastern hemlock trees, current hemlock quarantines and methods for identifying and treating hemlock woolly adelgid, visit the www.michigan.gov/hwa website.

Contact Blade outdoors editor Matt Markey at mmarkey@theblade.com or 419-724-6068.

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