Large nests in trees are quite the spectacle.

    When hundreds of caterpillars began to barrage Sharon Olslund’s yard, she called the Crookston Times to investigate.


    Tom and Sharon Olslund’s yard features a medium size flowering tree that housed a large, web like nest in the fork of a branch. A flowering tree next to their home had the same type of nest in it. Sharon said that the caterpillars were falling from the tree and causing a nuisance. In an attempt to control the caterpillars, the couple removed one nest in the tree in their backyard, and hundreds of them flooded the yard. It was something that she had never seen before.


    The Olslund’s story was quickly followed by a story of ridiculous numbers of similar caterpillars making a camping trip at Turtle River State Park unbearable, and a report of “raining” caterpillars, albeit of a smaller, greener variety, at the first “Kids at Castle” event of the year on June 10.


    These reports of caterpillars falling from the sky point to an onslaught of different types of tent caterpillars this year.


    The mysterious nests in the Olslund’s yard are home to eastern tent caterpillars.The caterpillars make their tent-like web nests on fruit trees like apple, chokecherry crabapple, plum, and cherry in May and June. The larvae feed on leaves, and although they generally do not affect tree health, they do sometimes defoliate trees.


    Eastern tent caterpillars can be identified by their blue, black, and orange markings and white stripe down their back, and are two inches long when fully grown.


    While the Olslund’s nests were in flowering trees, forest tent caterpillars are typically found in broadleaf trees and plants like quaking aspens, balsam poplar, basswood, oaks, ashes, birches, alder, and fruit trees.


    To deal with eastern tent caterpillars in your yard, remove the webbing along with the caterpillars from the tree, and bury or bag them to properly dispose them. Pesticides can be used as long as the caterpillars are one inch long or less, as the pesticides may no longer be effective if they reach their full size.


    Some products that are viable to control the caterpillars are residual pesticides, spinosad, insecticidal soap directly on the insects or Bacillus thuringiensis, which is a good option if the tree is flowering, as it will not harm pollinators.


    These caterpillars usually aren’t harmful to trees, but if the trees are young or unhealthy, they may need protection from defoliation. Usually, they are only an annoyance, as the Olsunds found when caterpillars covered their yard.

Information found at https://extension.umn.edu/yard-and-garden-insects/eastern-tent-caterpillars
https://extension.umn.edu/yard-and-garden-insects/forest-tent-caterpillars