Dormant forests

One of the best tools to maintain forest health is knowledge. More “eyes” in the forest serves to help catch exotic invaders early and increases the chances of successful eradication.

Now is a great time to begin monitoring the health of your trees. The hardwoods have lost their leaves, allowing easier observation of stems and branches. Conifers have also shed their older and damaged needles, lending a better opportunity to evaluate general health conditions.

Michigan State University Extension suggest that taking notes, or journaling, over the years can be a valuable resource in better understanding trends in woodlands. It can also be an effective way to notice early entry of exotic insects and diseases. Similar monitoring of trees in residential areas, parks, and urban zones will sometimes yield early detections. Early detections increase the eradication opportunity.

For many people, winter provides more time for learning. Learning to identify key insect and disease pests (and their look-alikes) might be the first step in arming yourself against forest threats in the next growing season. Knowing what can, and what can’t, be done will help owners better manage both woodland trees and residential trees. Every year, trees are host to many pests, most of which are part of natural systems, and some are quite interesting to learn about. Most do not pose serious threats to tree health.

However, exotic insects and diseases can be serious game-changers. Vigilance against these threats has become increasingly important as greater numbers of exotics find their way to American forests. People interested in trees and forests, would do well to know what to look for.

Three particularly ominous threats are the Asian long-horned beetle (ALB), the hemlock woolly adelgid (HWA), and thousand cankers disease (TCD) of black walnut. The Midwest Invasive Species Information Network (MISIN) is a good source of information, including a SmartPhone app and reporting protocols. The Michigan Department of Agriculture and Rural Development has regulatory authority for these threats. The Internet is fairly rich with information resources.

Neither the ALB nor TCD have yet been found in Michigan. The HWA has popped-up several times since 2006, with several past successful eradications. Several newer infestations were discovered this past summer. Eradication efforts are underway.

The HWA infestations often begin near the tops of hemlocks, making early detection difficult. The insect attaches itself at the base of needles and inserts a long stylet into the small twigs. Colonies of these insects appear as small, white blotches. These blotches are waxy protective coatings that many adelgids create around themselves. Now, through early summer, is a good time to watch for these adelgids.

The ALB is a large black beetle with white blotches. The antennae have alternately-colored light and dark segments. Evidence of early infestation is difficult to see. Preferred tree hosts are maples. Top dieback usually occurs first. Shallow oviposition sites might be seen on the bark. Eventually, large exit holes, about a half-inch in diameter, will be seen lower on the trunks. By this time, serious damage has occurred and the beetle has likely spread to nearby maples, or other tree species. The MISIN website has a training module.

TCD of black walnut is a combination of a native insect and an exotic fungus, an arrangement similar to beech bark disease. A small bark beetle chews through the bark inadvertently carrying the fungal spores. The spores germinate and the fungus creates a small canker of dead tissue around the beetle entry hole. Hundreds of these small cankers can form, which leads to the name “thousand cankers disease” and eventually kills the walnut. Look for small, darkened, and slightly sunken patches on twigs.

Monitoring forests and trees can be a great adventure in practicing citizen science, such as MSU’s new “Eyes on the Forest” project. A citizenry armed with knowledge of these threats can go a long way in helping agencies in the battle to keep forests, both woodland and urban, in healthy and productive condition.

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