Released Jan. 21, 2008
AMES, Iowa -- Let’s face it – bugs do not fall on the "Top 10 Things to Worry About" list for the average American. Oh, some may admit to thinking about those pesky Asian lady beetles or boxelder bugs that invade a home for the winter. Other folks have been concerned about what is causing the demise of honeybees. And some (mainly farmers) may talk about how soybean aphids, western bean cutworms or corn rootworms affected their crop yields at the end of the season. But a bug pest on trees usually receives little to no attention.
A Newsworthy Insect
An exception to this generalization is the emerald ash borer, Agrilus planipennis. It is one of the most watched and alarming insects right now in the United States. This exotic pest from Asia has caused the death and removal of more than 25 million trees in the principal infested areas [Michigan, Ohio, Indiana, Illinois (Chicago), and Maryland]. Contrary to normal insect borers, emerald ash borer (EAB) infests healthy ash trees, not just ones that are weak or dying. And, researchers have not identified ash trees that have resisted this pest, which differs from some American elms that were not killed by Dutch elm disease.
One of the trees used to replace the elms destroyed by Dutch elm disease was ash. Iowa has an estimated 15 million ash trees in urban settings and another 50 million ash trees in rural forests. Approximately 20-70 percent of street trees in many Iowa towns and cities are green ash. In a ‘perfect world’, no more than 10 percent the urban forest should be one species. One recent estimate to cut down and chip urban ash trees in Iowa was $3-5 billion.
The Damage Done
Although adult EAB beetles feed on ash leaflets, it is the larval stage that kills trees. These creamy white, flattened larvae feed just under the bark in the nutrient-rich cambium tissues. As they feed, they produce winding tunnels that cut across the active xylem and phloem vessels, which carry water, minerals and nutrients throughout the tree. Thus, the parts of the tree beyond an EAB-infestation slowly starve and die, usually within two to four years.
EAB in Three New Areas
During 2007, newly confirmed sites of EAB-infested ash trees were found in central Illinois, western Pennsylvania and north central West Virginia. The closest site to Iowa is Peru, Ill., approximately 85 miles from the Quad Cities. On their own, EAB adults can fly 1-2 miles. These long-distance expansions to the previously known EAB infested areas have been due to unintentional, man-assisted movement in ash wood products, especially firewood. Out-of-state campers and hunters visiting Iowa this season are encouraged to buy firewood upon arrival.
2007 Iowa Surveillance Data
In its fifth year of looking for EAB, Iowa State University (ISU) Extension worked on three fronts: visual surveys, sentinel trees and experimental traps. More than 1,100 ash trees at 400 campgrounds (private, county, state and federal) were visually checked for symptoms of EAB. ISU Extension was a collaborative partner with Iowa Department of Agriculture and Land Stewardship, Iowa Department of Natural Resources and United States Department of Agriculture in bark-peeling more than 230 sentinel trees on 58 sites across the state. And, ISU Extension coordinated the placement and assessment of 100 experimental sticky traps in 10 cities (Ames, Bettendorf, Clinton, Cedar Rapids, Davenport, Des Moines, Dubuque, Iowa City, Newton and Waterloo), thanks to several city foresters. Fortunately, EAB was not found in Iowa.
2008 Plans
The plan for this year includes revisiting sawmills and wood product sites, inspecting ornamental plant nursery operations, visual surveys in 400 campgrounds, bark-peeling 400 sentinel trees and participating in two national United States Department of Agriculture trapping programs.The purple sticky traps will be placed either at high risk sites in the state (campgrounds, rest areas, ornamental nurseries, etc.) or in a grid pattern in eastern Iowa, approximately one trap per 1.5 square miles. An attractant chemical, manuka oil, will accompany the experimental traps this season.
What You Can Do To Prepare
Because Iowa does not have EAB, we have an excellent opportunity to be prepared ahead of the invasion of this destructive insect pest. There are several things you can do to help Iowa prepare:
Determine if you have an ash tree on your property. A user-friendly picture key is available at www.extension.iastate.edu/wiki/tree/
Volunteer to help your community develop a tree inventory. Knowing the type and location of tree species is important in responding to invasive pests.
Protect your trees from mechanical injuries (lawn mowers, string trimmers, construction projects and vehicle parking on root zone). Insect borers prefer trees that are damaged or otherwise stressed.
Water your trees during dry periods.
Know the symptoms of EAB activity:
- Thinning and dieback of branches in ash tree
- Water sprouts on tree trunk or main branches
- D-shaped exit holes in the bark
- Flattened white larvae found feeding under the bark of ash trees and producing serpentine S-shaped tunnels
- Dark, metallic green beetles seen on tree trunks or flying near ash trees. Adults are small, about as long as Mr. Lincoln’s image on a penny.
Report suspect ash trees or beetles to ISU Extension Entomology (515) 294-1101 or the State Entomologist’s Office (515) 725-1470.
Talk with city managers, county governmental officials, state legislators and U.S. congressional members. Ask them if they know about EAB and the threat this pest is to Iowa. Now is the time to include EAB preventive efforts into fiscal budgets. Have them view a webcast on EAB at http://www.extension.iastate.edu/webcast.
Encourage relatives and friends to buy local firewood, whether for heating, camping or hunting purposes. Moving infested firewood is the most likely way that EAB will enter Iowa in the future.
Report any suspicious contacts with persons trying to sell you a guaranteed protection spray or injection of your ash tree with the Attorney General’s Office. Also report any persons claiming you must remove your ash tree because of a ‘bug’ in the area.
Resist the urge to apply a preventive insecticide treatment at this time. Since EAB is not known to be in Iowa, let’s wait and direct our efforts to prepare in other ways.
Bookmark these Web pages to keep current on EAB activity in Iowa at http://www.extension.iastate.edu/pme/EmeraldAshBorer.html or the nation at http://www.emeraldashborer.info/ .
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http://www.extension.iastate.edu/news/2008/jan/071602.htm
Contacts: Mark Shour, (515) 294-5963, mshour@iastate.edu
Jean McGuire, (515) 294-7033, jmcguire@iastate.edu
