Forest Tent Caterpillar in the Upper Midwest |
United
States Department of Agriculture Forest Service Northeastern Area NA-PR-02-01 Information Sheet |
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In the Upper Midwest, one of the more common natural enemies of FTC is a large gray fly called Sarcophaga aldrichi (fig. 7). This fly is locally referred to as the "friendly fly" or the "government fly". It is a native parasite that has evolved with FTC. It lays tiny maggots on the cocoons of FTC. The maggots eat the developing pupa inside a cocoon. S. aldrichi becomes very numerous near the end of outbreaks. In many cases the flies become more of a nuisance than the caterpillars. This fly does not bite but often lands on people, laundry, and light colored cars and siding. Natural enemies become more and more common during outbreaks and after 2-5 years they are killing so many FTC that the outbreaks subside. | ||||||
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Certain risk factors can increase the
likelihood of trees dying. Tree age, tree species, site quality and weather can
all interact to increase or decrease tree mortality. Older trees are more
likely to die than younger ones. Oaks and paper birch appear to be more at risk
than aspen or sugar maple. Trees growing under less than ideal conditions are
more prone to die. As an example, surveys in Minnesota found more dead aspen
trees on wet sites following an FTC outbreak. Drought conditions would also
make tree mortality more likely. |
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Applied Control Small landscape trees and shrubs can be protected by hand removal of egg masses or caterpillars. However, during large outbreaks many thousands of caterpillars will crawl long distances to find new food. This can make hand control very difficult. In addition, egg masses are often laid in the upper parts of trees making them hard to reach. FTC can be controlled using insecticides. County extension or state forestry offices should be contacted for a list of insecticides registered for use against FTC. One effective insecticide against young caterpillars is Bacillus thuringiensis var. kurstaki, known as Btk. This product is preferred because it has fewer "non-target" impacts than conventional broad-spectrum insecticides. One other practice that may be helpful would be turning outside lights off during the moth flight period in mid-summer. This may prevent moths from congregating and laying eggs in well-lit areas. Landscape trees should be maintained in a healthy condition before, during and after outbreaks through watering, proper pruning and mulching. Healthy, well cared for trees will survive even complete defoliation For Further Assistance Local information can be very helpful when considering a treatment program or when you are concerned about local impacts on trees or forests. Sources of reliable information on FTC as well as on other forest and shade tree insects are readily available. In Michigan, county extension offices provide information on a variety of forest and shade tree insects. In addition, the Michigan DNR has forest health specialists located at Regional Offices in Roscommon and Marquette. You can also visit the DNR forest health unit web site at: |
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http://www.dnr.state.mi.us/www/fmd/forhealth/index.htm | ||||||
In Minnesota, local DNR foresters can provide information and assistance. In addition, DNR forest health specialists are located at Regional offices in Grand Rapids, Rochester and St. Paul. County extension offices also provide information on a variety of tree related insect and disease concerns. You can also visit the DNR forest health unit web site for specific information on FTC at: |
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http://www.dnr.state.mn.us/treecare/forest_health/ftc/index.html | ||||||
In Wisconsin, local DNR foresters can provide information and assistance. In addition, DNR forest health specialists are located at Regional offices in Eau Claire, Green Bay, Madison, Rhinelander and Spooner. County extension offices also provide information on a variety of tree related insect and disease concerns. You can also visit the DNR forest health unit web site at: |
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http://www.dnr.state.wi.us/org/land/forestry/fh/overview/index.htm | ||||||
The USDA Forest Service maintains a forest health protection unit with insect and disease specialists in St. Paul, MN. This group provides service to National Forests, National Parks and other federal lands and cooperates with various state agencies. They can be contacted at the address listed below: |
USDA Forest Service Internet: Forest Health Protection 1992 Folwell Avenue St. Paul, MN 55108 http://www.na.fs.fed.us/spfo/info_dir.htm |
Pesticide Precautionary
Statement This publication reports research involving pesticides. It does not contain recommendations for their use, nor does it imply that the uses discussed here have been registered. |
Authors |
Steven Katovich Forest Entomologist USDA Forest Service Northeastern Area State and Private Forestry |
Jim Hanson Forest Entomologist USDA Forest Service Northeastern Area State and Private Forestry |
USDA is an equal opportunity provider and employer. |
Prepared
by: USDA Forest Service Northeastern Area State and Private Forestry, St. Paul, MN |