Insects invade the Duluth area

The population of mosquitos -- jokingly called Minnesota’s unofficial state bird -- soared this spring and has been almost overwhelming as mid-July approaches. And while the mosquitos may be running rampant in the northland this summer, they are not the only insects that have been invading the Duluth area as of late.

Mosquito - Jeff Hahn

Black flies, spruce budworms, brown marmorated stink bugs and emerald ash borers have all made their presence felt in the northland this summer. So are the bugs really worse this year than previous years?

“In general, the insects are about the same,” said Jeff Hahn, a University of Minnesota Extension entomologist. “Now there are certain types of insects where the numbers might be higher, but if we are talking about all insects in general, I’d say it’s about the same.”

Mosquitos and black flies benefited from the rainy spring.

“It has everything to do with the rainfall,” Hahn said regarding their increased populations.

The two insects laid their eggs last year. As the area saw increased rainfall, more eggs were able to hatch than usual, leading to a summer filled with the flying nuisances.

black fly - Jeff Hahn

“Mosquitos and black flies, although they both are aquatic as larvae, actually have pretty different habitats,” said Hahn. “Mosquitos like nice, shallow, calm pools of water, and black flies actually like to be in streams and rivers. Rainfall is going to basically give the same results. It’s going to give increased habitat, and large numbers.”

One insect that must have lost its invitation in the mail is the forest tent caterpillar, otherwiseknown as the armyworm. And while the forest-devastating worm’s cyclical appearance has been missing for a few years, Hahn says that we should enjoy their absence while we can.

“Know they are on the upswing,” he said. “We are starting to see increased numbers of these insects. It’s something that has been probably going a little slower than normal.”

Hahn said that although the Duluth area has not seen much defoliation (removal of leaves) from the armyworms, parts of central Minnesota have seen much more rapid defoliation than the northland.

“I would say take it while you can get it, because it’s not going to last indefinitely,” said Hahn. “I know Duluth and that part of the state certainly has had severe infestations in the past, and I would have no doubt that is going to happen again. It may just take a few more years.”

Another worm that the northland has been familiar with for many years is the spruce budworm. Similar to the armyworms, the budworm population has outbreaks approximately every thirty years. This summer just happens to fall into that cycle.

According to DNR Forest Health Specialist Mike Albers, the Cloquet Valley State Forest can expect to experience 15,000 acres of defoliation this year compared to a couple hundred acres during non-outbreak years.

Albers said that the spruce budworm was responsible for about 38,000 acres of defoliation around Lake Vermilion near Ely last summer, showing just how devastating this insect can be.

The northland knows to expect these cyclical insects, but other insects seem to come out of nowhere, such as the brown marmorated stink bug.

“The brown marmorated stink bug is definitely something that Minnesota is concerned about,” Hahn said. He added that the stink bugs show all the signs of being accidentally transported into the state.

Although the rate of population increase is slow, Hahn said that the impact these stink bugs will have is going to be very noticeable.

“Primarily it’s going to be an issue with agriculture,” he said. “If you’re growing corn or soy beans or apples, they’re all food crops that the insect can severely injure. They also attack a lot of plants in our landscapes: herbaceous plants, trees and shrubs.

brown marmorated stink bug - Jeff Hahn

“It’s also a nuisance insect,” Hahn added, citing the invasion of homes that takes place during the fall by insects such as cluster flies, lady beetles, and, of course, stink bugs. “They’re relatively big insects, and of course they can emit a pungent odor when they feel threatened. It’s something no one is going to look forward to.”

The good news is that the stink bugs will not be around in large enough numbers to affect the northland now. However, Hahn says their time is coming in several years.

The insect that may have the most harmful impact on the northland can be found in force just across the bridge in Superior.

The emerald ash borer devastated the ash trees of Superior in August 2013, forcing the city to take immediate action and begin removing over 3,000 ash trees.

Hahn said that the emerald ash borer has been found in just four Minnesota counties: Hennepin, Ramsey, Houston and Winona. But with Superior just a stones-throw away from Duluth, concern over the ash borer is building.

emerald ash borer 1 - Jeff Hahn

“There is a huge concern that (the emerald ash borer) is present in that part of the state,” he said. “They did not confirm that yet, it most likely is a matter of time before they are found, but that opens a whole new area in Minnesota where they are going to be.”

According to Hahn, Minnesota has one of the largest ash tree populations in the United States with close to a billion trees, not only in our forests but also in urban settings.

“There is basically no native ash that, once it’s attacked, it going to survive unless you treat it with an insecticide,” Hahn said. “It’s a very devastating pest.”

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