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HERE COME THE CATERPILLARS!
Article #47, May 2001
By Bill Cook

     This is the year folks.  The forest insect world doesn’t get much more exciting than this.

      The forest tent caterpillar (FTC) is expected to reach epidemic proportions.  The FTC has hatched and leaves are being eaten almost as fast as they are unfurling.   Caterpillars are munching right now as you’re reading this article. 

      The aspen and oak will go first.  The beech and red maple will be last.  But the predictions are that large portions of the Upper Peninsula hardwood forest will be defoliated this spring. 

      But not to worry.

      The FTC is a native insect that has outbreaks every 10-15 years.  The last outbreak was in the late 1980s.  We probably won’t notice the caterpillars or the defoliation until the end of May.  By then, the caterpillars will be an inch or two long and crawling over everything. 

      Memorial Day barbecues may have a lot of uninvited guests.

     By early June, some interesting things will happen.  Much of our forest will be leafless.  Public agencies will be doing a lot of explaining.  The FTC will have eaten itself out of house and home.  Lastly, there will be huge numbers of large gray flies that parasitize the pupae.

     These flies are natives and natural.   They are not planted by the government.  Tiny maggots are laid on the FTC cocoons and the maggots eat the pupa inside the cocoons.  The flies don’t bite people but are attracted to laundry and light colored clothing and housing.  The can be quite a nuisance.

     FTC outbreaks do not cause significant damage to the forest.  Most trees will lose out on some growth for the year, but few trees die from FTC defoliation.  It looks a lot worse than it is.

     Don’t be fooled into harvesting your timber because of the FTC outbreaks, either.

     The trees will grow new leaves in June, although they may be smaller than the first crop.  The stress of using up food reserves may be too much for a few trees.  But trees in otherwise good condition will not die from the FTC outbreak.

      Despite the name, the FTC does not build tents.  The tents seen in early summer are made by a cousin, the eastern tent caterpillar.  Cherries, plums, and apples are preferred hosts. 

      The gypsy moth may also be falsely accused of participating in the feeding frenzy.  There are actually few breeding populations of gypsy moths in the U.P., but some folks will make the association. 

      Forests always have interesting insect activities, but few are as spectacular as the height of a forest tent caterpillar outbreak.  Enjoy the extra sunshine in the woods, if you can!

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Trailer
Bill Cook is an MSU Extension forester providing educational programming for the entire Upper Peninsula. His office is located at the MSU Upper Peninsula Tree Improvement Center near Escanaba. The Center is the headquarters for three MSU Forestry properties in the U.P., with a combined area of about 8,000 acres. He can be reached at cookwi@msu.edu or 906-786-1575.

Prepared by Bill Cook, Forester/Biologist, Michigan State University Extension, 6005 J Road, Escanaba, MI  49829
906-786-1575 (voice),  906-786-9370 (fax),  e-mail:  cookwi@msu.edu

Use / reprinting of these articles is encouraged. Please notify Bill Cook.
By-line should read "Bill Cook, MSU Extension" Please use the article trailer whenever possible.

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Last update of this page was 22 September, 2005

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