Daily Press file photo A pathway winds through a forest in Delta County. Many insect pests pose a threat to the health of forests in the Upper Peninsula.

ESCANABA — Residents of the Upper Peninsula are no stranger to bugs. Locals familiar with insect booms have said that mayfly populations were way down this year, mosquitoes were especially aggressive in the spring, and ticks came out early and strong following a mild winter. But what about the pests that attack our forests?

Both native and invasive insects can and do wreak havoc on trees. As roughly 90% of the U.P. is forested, it is easy for outbreaks to spread. It is the responsibility of landowners to remain diligent and protect trees on their property where possible, and of travelers to avoid transporting firewood more than a few miles.

Spruce budworms, which attack primarily balsam fir and spruce trees, have been seen in high numbers for the past several years. This native pest is always present in U.P. forests, but approximately every 30 years or so, an outbreak of exceptionally high numbers lasts for about 10 to 15 years before tapering off, said Simeon Wright, forest health specialist with the Michigan Department of Natural Resources. He estimates that in Delta County, the current outbreak is on its way out, based on the defoliation observed, which was not as extreme as in other locations or in previous years. Spruce budworm damage is noticeable in the form of red or brown needles, which may still be on branches but often fall when wind and rain pick up. By this point in the summer, the damage from this year’s hatching is done, as most of the caterpillars have pupated and are now seen as little grey moths whose presence is merely a nuisance rather than destructive. However, people who are noticing fir and spruce defoliation and moths now are advised to act by spraying with budworm-specific pesticide in the spring if they wish to prevent further damage next year.

“In the spring, when the buds break open and those shoots start to expand, take a close look and see if there’s feeding, chewing starting to occur on those elongating shoots. At that time, insecticide applications can be very effective,” said Wright.

Another pest that has been thriving is the pine bark beetle. “They typically just attack stressed and dying pine trees, but when you have drought or other issues that cause trees to become stressed, these native beetles overcome the trees’ defenses and start to build up higher populations and could kill a few healthier trees,” said Wright. Watering high-value pine trees during dry periods can help extend life. Signs of pine bark beetle infestation are holes in the bark and sawdust-like frass near the base of the tree. Trees already heavily infested should be removed and destroyed — including the stump — as soon as possible in order to prevent the beetles from spreading to healthy trees. It is important to burn wood promptly and thoroughly.

Emerald ash borers, invasive pests first observed in Detroit in 2002, have spread to 36 states and killed tens of millions of ash trees, according the the U.S. Department of Agriculture’s Animal and Plant Health Inspection Service (APHIS). Delta County has fallen victim to the small green beetles and lost many trees, but emerald ash borers continue to be active and still pose a threat to surviving trees.

One home on the Stonington Peninsula provides an example of the severity of the impact of boring pests. Doug and Dawn Schmidt used to have 10 ash trees in their yard. Gesturing out at a now-empty lawn, beyond which is Little Bay de Noc, Schmidt said, “Right along the lake, in that open spot, they used to give us shade in the late evening so the sun wouldn’t beat on the house and turn it into a sauna. It hits all these windows and heats the house up, so now the air conditioning is usually running.” He was forced to remove the entire stand of trees around 2019 after emerald ash borers devoured them beginning about six or seven years ago.

For remaining valued ash trees, such as shade-providing favorites in a yard like Schmidt’s, insecticides — typically applied as a drench or injected by arborists — can work for a few years before reapplication is needed.

Forest tent caterpillars, a native species of which higher populations are seen about every eight to 10 years, defoliate hardwood trees. The bumper crop explosion usually lasts for only about two or three years before natural predators and/or diseases cause the population to crash again. “Most of the hardwood trees can withstand that defoliation pretty well,” said Wright. “The main issue is just the annoyance and the visual impacts.” By mid-July, tent caterpillars would be finishing up their activity, and any impacted trees would be refoliating. 2023 has not been a major year for the caterpillars, although the DNR has received reports of forest tent caterpillar defoliation in Iron and Marquette counties.

Spongy moths, another pest to hardwoods, are non-native, but at this point have become naturalized in Michigan. A few years ago, high numbers in the Lower Peninsula were responsible for defoliating 1.2 million acres, Wright reported. He said that spongy moths do seem to be proliferating in the U.P., with localized defoliation in Menominee county this year attributed to them. As with tent caterpillars, defoliation by spongy moths is usually not a tree’s death sentence. Growth is inhibited, but healthy trees will be producing new foliage around this time. Hardwoods that are overly stressed by drought, age, or other pressures may end up being pushed to the brink when defoliated, but often a good watering can coax a defoliated tree back into a more vivacious state. As with tent caterpillars, Wright explained, population booms of spongy moths are followed by a crash in numbers after a few years.

Many other invasive and harmful creatures that have not yet reached the U.P. are dangerously close to doing so. The spotted lanternfly — which feeds almost indiscriminately on dozens of varieties of plants — has been seen en masse across 13 states, and East Coasters are familiar with the mantra “see it, squish it, report it” that spread through the northeast along with lanternflies, which were first found in Pennsylvania in 2014. In Michigan, they have been spotted in Oakland County. The spotted lanternfly is on Michigan’s watch list, and anyone who sees them in the state is asked to “take a picture, squish it, and report it.” Reports may be made to the DNR.

The Asian longhorned beetle, which looks somewhat similar to Michigan’s native pine sawyer beetle, but has not yet been detected in Michigan, can kill trees, its favorite being maple. According to APHIS, they have “the potential to cause more damage than Dutch elm disease, chestnut blight and (spongy) moths combined, destroying millions of acres of America’s treasured hardwoods, including national forests and backyard trees.” They currently infest trees in Ohio, New York, and Massachusetts.

The increased danger of burgeoning invasive species is that native organisms lack necessary defenses, and without natural predators, invasive populations explode dramatically and can choke out native life. 42% of endangered and threatened species in the United States are directly at risk from invasive species, states The National Wildlife Foundation.

Some species, including spongy moth, fall under state and/or federal quarantine. In counties where quarantines are in place, moving certain materials is prohibited. Such items may include the infected plant matter itself, all firewood, and other organic materials like soil, which may harbor unseen eggs. Specific regulations may be found on the website for the Michigan Department of Agriculture and Rural Development (MDARD) on the page entitled “Plant Pest Quarantines.” For general information, see michigan.gov/invasives.

The easiest way to prevent destructive insects from spreading throughout forests, or from one to another, is in the name of a campaign managed by The Nature Conservancy. “Don’t Move Firewood” recommends not transporting firewood more than 10 miles, and never more than 50 miles. Firewood should be harvested or purchased in the closest area; if nothing is found nearby, certified heat-treated firewood is considered safe for transport.

In coming weeks, the Michigan DNR will be conducting aerial surveys that will provide clearer information on the state of U.P. forests and the factors that damage them. Readers may seek reports on the web page “Forest Health: Protecting Forests from Pests and Diseases” on michigan.gov.