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

Sunday, June 17, 2007

Parasitic wasps vs. emerald ash borers

Tiny wasps may be released as a biological control for emerald ash borer

U.S. Forest Service research entomologists from Michigan have completed a study of the emerald ash borer in its natural habitat in China. They discovered three tiny parasitic wasps that keep it under control there.

The three are drawn only to ash trees. Some walk all over the bark looking for eggs to lay their own eggs in; others listen for ash borer larvae below the surface and then drill through the bark and lay their eggs in or on them.

What happens next is a tiny version of the "Alien" movies: After the wasps lay their eggs, the eggs hatch by bursting out of the embryonic borers, killing them.

Source: "Experts seek borer relief" by Dan Gibbard, Chicago Tribune, June 17, 2007.

The research team has recommended to the USDA that these wasps be imported as a biological control for the emerald ash borer.

Fears of the Public

The following comments about the parasitic wasps were posted on a radio station's news site by concerned citizens. They are very representative of concerns expressed in all the articles I read about the possible introduction of the parasitic wasps.

Re: Wasps Could Wipe Out Emerald Ash Borer
Posted: 2007/6/15 1:06 Updated: 2007/6/15 4:07
I sure hope there aren't a lot of people who are allergic to bees and stuff in those areas. Or else the hospitals will be full or maybe even the funeral homes.

Re: Wasps Could Wipe Out Emerald Ash Borer
Posted: 2007/6/14 11:07 Updated: 2007/6/14 11:19
so this sounds good, but what else will these wasps eat? what if they discover something they like better than the ash borer and decimate that species? Is this not why we are inundated with the bad ladybugs?

Fears Addressed

The fears expressed about the wasps killing people are unfounded. The wasps are stingless and very small -- about the size of a straight pin's head.

The introduction of these parasitic wasps could cause unforeseen problems. The concern that they may seek alternate hosts is certainly valid.

"Bringing in an exotic species to control an invasive species can create a lot of problems," said Dr. James Dunn, an entomologist who teaches biology at Grand Valley State University.

"There is no guarantee they will kill just the ash borer -- that's the danger," Dunn said. "Maybe the risk is worth taking, I don't know. It is not a slam dunk, though."

Repeated laboratory tests indicate that the wasps aren't interested in native borers, just the emerald ash borer, [USDA research entymologist Leah] Bauer said.

Source: "Wasps may help fight ash borer in Mich.," an AP story published June 11, 2007.

My Opinion

Personally, I would rather take the chance of introducing the wasps than watch every ash tree in North America die. The bacteria introduced from Japan to help control gypsy moths has worked well, and there's every reason to hope that the parasitic wasps will be a successful weapon against the emerald ash borer.

The emerald ash borer was first identified in 2002 in Michigan, and since then, 20 million North American ash trees have died from infestation. As these ash trees have died, entire ecosystems have been affected. It is a staggering problem.

The decision of whether to release the wasps has not yet been made.

Read more:

Battle of the Bugs: Parasitic moths are to be lined up against the ash borer

Ash borer fight adds wasps

1 comments -- please add yours:

Oak Leaf said...

I hope the wasp is effective. I am in the state, Minnesota that is fairly close to the infection area. I have several young Ash trees on my 3/4 acre property. Removing them would get expensive. I would like to see the native Green Ash in my front yard live to maturity.

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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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