Tree Notes is about trees -- especially native trees, trees for wildlife, and trees in history.

Wednesday, May 30, 2007

Protecting young trees from periodical cicadas

17-year cicadas may damage small trees


Question:
What do these states have in common?
• IA, IL, IN, MI, WI
• KY, GA, IN, MA, MD, NC, NJ, NY, OH, PA, TN, VA, WV

Answer:
Both will soon experience the return of 17-year cicadas. The first group of states (IA, etc.) will have a cicada summer in 2007 when Brood VIII hatches, and the second group of states (KY, etc.) will have a cicada summer in 2008 when Brood XIV hatches.

There are 12 broods of 17-year cicadas and 3 broods of 13-year cicadas in the eastern U.S. Most of them are on different schedules. A master schedule and much information about periodical cicadas is provided on the Periodical Cicada Page by The University of Michigan Museum of Zoology.

The cicadas have been underground, sucking sap from tree roots for the last 17 years, and they will be emerging to mate, not feed. However, female cicadas will cut slits in small branches and lay eggs in the wounds. This will often cause the end of the branch to die. On a large, healthy tree, the damage won't be life threatening, but it could injure a small tree seriously.

The University of Illinois Extension Service provides this information:

Eggs are inserted into tree and shrub stems that are up to two inches in diameter. Heavy egg laying will cause twigs to break, resulting in dead leaves at the end of branches. Small trees may have enough eggs laid into the trunk that it breaks off.

Source: The Green Line, They're Back! Periodical Cicadas."June 2005
They advise that a small tree should be protected with netting or mesh that stands away from the main branches and trunk far enough that the cicadas can't reach them with their ovipostors (egg-depositors).

A recent article in the Chesterton [IN] Tribune gives similar information:

These small trees can be protected with nylon netting or cheesecloth during the egg-laying period. The netting should have a mesh of no less than 1/4 inch and should be placed over the trees when the first male songs are heard. The netting should be tied to the trunk beneath the lower branches and can be removed after adult activity has ended. Young twigs that have been damaged by egg laying should be pruned and destroyed within a three-week period after eggs are laid. Doing so will prevent newly emerged nymphs from reaching the ground.

Source: "Cicadas are back: Tips to protect small trees," Chesterton Tribune, by staff.

If you live in one of the states that will host periodic cicadas in 2007, you should be prepared to put the mesh in place soon. Cicadas may already be emerging. Small "volcanoes" of dirt under your trees will be the first sign that the cicadas are moving to the surface to mate. After they mate, the egg laying will begin.

Don't worry about your conifers. Cicadas don't usually bother them.

More information:
The Master Gardeners: The 17-year cicadas are coming this year
The Otherworldly Roar of the Cicadas
Periodical Cicadas in Kentucky

17-year cicadas
USDA image

2 comments -- please add yours:

Collagemama said...

I've worked in libraries so much of my life that "periodical cicadas" gives me nightmarish images of swarms flying out when I open a Newsweek or AARP magazine!

Genevieve said...

Sounds like a possible horror movie plot to me.

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Enrich your life with the study of trees.

"The power to recognize trees at a glance without examining their leaves or flowers or fruit as they are seen, for example, from the car-window during a railroad journey, can only be acquired by studying them as they grow under all possible conditions over wide areas of territory. Such an attainment may not have much practical value, but once acquired it gives to the possessor a good deal of pleasure which is denied to less fortunate travelers."

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Print references I frequently consult

Benvie, Sam. Encyclopedia of North American Trees. Buffalo, NY: Firefly, 2000.

Brockman, C. Frank. Trees of North America: A Guide to Field Identification. Ed. Herbert S. Zim. New York: Golden, 1986.

Cliburn, Jerry, and Ginny Clomps. A Key to Missouri Trees in Winter: An Identification Guide. Conservation Commission of the State of Missouri, 1980.

Collingwood, G. H., Warren David Brush, and Devereux Butcher. Knowing Your Trees. Washington: American Forestry Association, 1978.

Dirr, Michael. Dirr's Hardy Trees and Shrubs: an Illustrated Encyclopedia. Portland, Or.: Timber, 1997.

Elias, Thomas S. The Complete Trees of North America; Field Guide and Natural History. New York: Book Division, Times Mirror Magazines, 1980.

Grimm, William Carey. The Book of Trees;. Harrisburg, PA: Stackpole, 1962.

Hightshoe, Gary L. Native Trees, Shrubs, and Vines for Urban and Rural America: a Planting Design Manual for Environmental Designers. New York: Van Nostrand Reinhold, 1988.

Little, Elbert L. National Audubon Society Field Guide to North American Trees. New York: Chanticleer, 1996.

Martin, Alexander C., Herbert S. Zim, and Arnold L. Nelson. American Wildlife and Plants. New York: McGraw Hill, 1951.

Mitchell, Alan F., and David More. The Trees of North America. New York, NY: Facts On File Publications, 1987.

Randall, Charles E. Enjoying Our Trees. Washington: American Forestry Association, 1969.

Settergren, Carl D., and R. E. McDermott. Trees of Missouri. Columbia: University Extension, 1995.

Sternberg, Guy, and James W. Wilson. Native Trees for North American Landscapes: from the Atlantic to the Rockies. Portland: Timber, 2004.

Wharton, Mary E., and Roger W. Barbour. Trees and Shrubs of Kentucky. Lexington: University of Kentucky, 1973.

Wyman, Donald. Trees for American Gardens. New York: Macmillan, 1965.

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