Last summer I spent an hour a week walking around in circles on baseball diamonds, staring at the ground. People probably thought I was a crazy person. What I was really doing was biosurveillance. No, I wasn’t wearing a hazmat suit or carrying high-tech spy equipment. I needed only my eyes and a pencil and paper to record what I saw.
I was searching for nests of cerceris wasps, a non-stinging – to humans anyway – native wasp that makes its nest in disturbed sandy soil. Baseball diamonds that are only occasionally groomed are the best disturbed sandy soil around.
The wasp nest looks like an anthill, but the entrance hole is larger, about the diameter of a pencil. What’s important about these wasps is that they prey on emerald ash borer, the beetle that is systematically killing ash trees across our state and nation.
I am part of Wisconsin’s new First Detector Network, whose goal is to empower members of the public to take action against invasive species by providing training and volunteer opportunities. One of WIFDN’s projects is to search for and monitor cerceris wasp nests at approximately 500 baseball diamonds across the state.
Cerceris wasps sting emerald ash borers which paralyzes them. Then they carry the borer back to their nest in the sand. The wasp buries each paralyzed borer in a separate tunnel, lays an egg, and closes off the tunnel entrance. When the wasp larvae hatches, it feeds on the borer.
Occasionally, a paralyzed beetle is rejected and tossed out of the nest for some unknown reason. Spotting and collecting these rejects is the most important part of the WIFDN study. EAB are not usually detected in an ash tree until it is too late – the tree is done for by the time the damage shows up. But rejected beetles can be found around wasp nests much earlier than that, giving people a chance to save their ash trees if they so desire.
Cerceris wasps prey on beetles other than EAB. Three other beetles of concern destroy oaks and other valuable trees. While these three have not yet been found in Wisconsin, monitoring the wasp nest rejects will provide an early warning system so that we don’t have another pest like EAB sneaking in and killing off our trees before we see them coming.
So why should we care if our ash trees disappear? We have plenty of other trees don’t we? Well, ashes make up almost 7% of Wisconsin’s forests. So if we lose 7% of our trees, that doesn’t sound too bad. But that doesn’t mean every forest is 7% ash. Some forests will be entirely wiped out while others with lesser or no ash trees will be unaffected. In addition, many pretty, shaded, tree-lined residential neighborhoods (where 5.2 million ash trees live) will find themselves in blazing hot sun.
That 7% is about 834 million trees. Besides providing shade and beauty, the seeds of ashes provide food for birds and small mammals, wood ducks nest in their trunk cavities, deer and moose browse on black ash twigs, and one hundred fifty species of butterflies and moths are supported by ash trees.
EAB has been detected in 29 Wisconsin counties, mostly in the southern half of the state. These counties are under quarantine, meaning it is illegal to transport firewood from them to non-quarantined counties. Be responsible and help prevent the spread of EAB by procuring your firewood near to where it will be burned. Even though it is still legal to move firewood from and between non-quarantined areas, it’s probably a bad idea to do so.
The Wisconsin DNR has written guidelines to help landowners minimize EAB damage. See http://dnr.wi.gov/topic/foresthealth/emeraldashborer.html. For the most current Wisconsin information on emerald ash borer, have a look at this website: http://datcpservices.wisconsin.gov/eab/index.jsp. Here you can learn what an ash tree looks like, what emerald ash borer and the damage it does looks like, where in Wisconsin it’s been found, and how to manage it.
If you suspect EAB on your property, report it to the Department of Agriculture, Trade and Consumer Protection by calling the Emerald Ash Borer Hotline at 1-800-462-2803 or submit a report online here: http://datcpservices.wisconsin.gov/eab/reporteab.jsp.
There is a small ray of hope for ash trees. Along with the cerceris wasp, three other natural enemies of EAB from China have been released in Michigan, Indiana and Ohio. Two of those species have established populations. There are some chemical and microbial insecticides that can protect ash trees from EAB attack. Some are available to homeowners but others need to be applied by a certified, licensed pesticide applicator. Of course, the treatments are expensive and the use of chemicals comes with its own set of issues. Still, they may have a role in protecting some valuable forest trees.
SYMPTONS AND SIGNS OF EAB
CROWN DIEBACK: The top of the tree has dead branches.
EPICORMIC SPROUTING: New branches or leaves growing in strange places, like from the base of the trunk or low on the tree.
BARK SPLITS: Vertical splits in the bark. Peek inside and you may see a serpentine-shaped design caused by larvae feeding under the bark.
WOODPECKER FEEDING: Woodpeckers high in the tree are trying to get at emerald ash borer larvae that are under the bark.
D-SHAPED EMERGENCE HOLES: Emerald ash borer adults leave a 1/8 inch diameter capital “D” shaped hole.
S-SHAPED LARVAL GALLERIES: The larvae wind back and forth under the bark as they eat (and poop) carving a shallow serpentine pattern inside.
LARVAE: Cream colored, up to 1 ½ inches long with two tiny pinchers at the end. The body looks almost jointed, with a series of tiny bell-shaped sections placed end to end. You’ll find them feeding under the bark.
ADULTS: Bright metallic green, about the size of a grain of cooked rice.
EAB arrived first arrived in the U.S. in Detroit in 2002 in packing materials from China. Studies have shown that on their own, the beetles would have traveled less than ten miles from the port in Detroit by now. Unfortunately, humans have assisted in their spread across the United States by moving infested firewood. It was thought that emerald ash borer would stop its westward march at the Great Plains for lack of trees. And it did. Except that there is a large infestation in the Denver area. All it took was one person transporting firewood to Colorado to start an infestation that could annihilate every ash tree in the Denver area. The point? DO NOT TRANSPORT FIREWOOD!
CAN YOU BURN THE WOOD FROM AN EAB-INFESTED TREE?
Sure, but split and leave the wood near where you cut it down for at least two summers before moving it, because emerald ash borer can continue to emerge from the wood for two years after cutting. After two years, you may move it, but still only within the quarantined area.