Advance of the adelgids: A possible threat to Michigan forests
Two potential insects are just some in a long line of exotics pests and diseases that have serious effects that could cause great damage to Michigan forests and economy.
Aphids? Adelgids? Scales? For most of us, they’re similar enough to be about the same thing. They’re very small, soft-bodied insects that siphon the juices out of trees and other plants. Many species become immobile after inserting long, feeding stylets (tubes) under the bark of a twig or branch. They then cover themselves with protective coats. These coats might be hard and shiny, waxy or fluffy. They’re unique little critters.
Most of these species are native and more-or-less harmless to trees. However, the hemlock woolly adelgid (HWA) and balsam woolly adelgid (BWA) are exotic species that have caused considerable forest damage across large parts of North America. The Carolina hemlock is facing possible extinction, for example. We don’t want these adelgids in Michigan.
Both HWA and BWA are commonly spread by the movement of nursery stock. Be careful when you buy hemlock and fir (or anything else for that matter) for landscaping. Learn where the vendor acquired the planting stock and, like many things, keep it local.
Vigilance is warranted, so what do you look for? First, learn to recognize the differences among hemlock, fir, and the other conifers. It’s not too tough and there are only about 14 common conifer species in Michigan. Incidentally, only four of them are pines.
Once you’re looking at the right tree, search for tiny white bumps or puffs, smaller than the head of a match. These are the stationary adelgids under their waxy coatings. On hemlock, they’re most common on the twigs at the base of the needles. This can be hard to see in a tall hemlock. On firs, they’re more likely to be seen on the bark of the trunk. The firs often look sickly after heavier infestations.
However, you’re not likely to soon see either HWA or BWA. Neither species is thought to be established in the Lake States, at least so far. Then why bother to look? Actually, most exotic forest pests are not discovered by the entomologists or foresters – they are discovered by observant and curious forest visitors and homeowners.
Thousands of eyes watching for unusual health conditions are critical for combating these emerging disease and insect problems. A small outbreak can often be successfully eradicated with a relatively small amount of effort. This has already happened several times in Michigan with HWA. There is hope! Larger outbreaks are more difficult to eradicate.
What about the fear of “crying wolf?” There are, of course, native species and other look-alikes that can be confusing. However, in these days of Internet access, digital photography, and email access to experts, it’s a lot easier to address these sorts of concerns. The forestry community would rather respond to a thousand cases of mistaken identity than risk missing a relatively easy job of eradicating a small outbreak of a nasty insect or disease.
Forest owners, and others, can use these opportunities to learn more about the forest. The more you know, the more likely you are to recognize an important pest. And learning about forest ecology can be rewarding and fun all unto itself. Be inquisitive – if something just doesn’t look right, try to figure out why.
Where to go for help? The Internet has lots of information, including many pictures, if you have an idea of what you’re looking for. “Knowing” is the hard part. More traditionally, try contacting a Michigan State University Extension office or County Conservation District. Most counties in Michigan are served by one or the other. The Conservation Districts now have 13 foresters funded by a new state program and they serve about 30 counties. If you’re forest owner, consider hiring a consultant forester. Forest health issues are just one of many services these foresters can provide.
Of course, healthy forests are everyone’s concern. We can’t live without them. Keeping an “eye out” during your forest visits is the first step in helping to protect these vital natural resources.