Released June 4, 2009

AMES, Iowa -- The presence and new discovery of emerald ash borer (EAB) in states adjacent to Iowa has increased interest in this exotic, invasive insect and what Iowans can do to protect ash trees (Fraxinus species) on their property.

ISU Extension is collaborating with Iowa state regulatory agencies and local officials to prevent introduction of EAB into Iowa and limit its spread. For a full list of EAB detection and education activities, visit http://www.extension.iastate.edu/pme/EmeraldAshBorer.html .

Treatment options to protect ash trees from this destructive pest are available but careful and thoughtful analysis is needed to circumvent spread of false information and excessive and needless use of insecticides. Forest, horticulture, and insect specialists with Iowa State University Extension have developed a guide that outlines your management options against EAB.

The first step for many is confirming that you do have an ash tree. Only ash trees are susceptible to EAB attack, but all species and cultivars of ash trees are at risk.

Second, is the ash tree growing vigorously and in apparent good health? Trees must be healthy and growing for treatments to be effective. Ash trees with mechanical injuries, loose bark, thin canopies, and those growing on poor sites (limited rooting area, compacted soil or other stresses) are not worth treating. If your ash tree looks healthy and is important to your landscape, then preventive treatment options may be considered.

Insecticide control measures against EAB should not be used unless you live within 15 miles of the confirmed EAB infestation. Treatment outside this risk zone is not advised. Protecting ash trees with insecticides is a long-term commitment. Most treatments will need to be reapplied annually or twice per year for an indefinite number of years to protect the tree. With that in mind, most homeowners would be ahead to remove and replace susceptible trees.

Treatment timing is critical and must be matched to insect life cycle. After mid-June treatment is not recommended because it takes time for the systemic insecticide to be distributed within the tree (from 2 – 8 weeks depending on the application method).

The recommended time of application is early to mid April each year. If the tree is large (more than 16” diameter), a treatment in early fall is also suggested. So the next window for treatment for trees in Iowa would be mid to late September 2009.

A new Iowa State University Extension publication, PM 2084, Emerald Ash Borer Management Options, will be available on June 12. The North Central Region Integrated Pest Management Center’s Insecticide Options for Protecting Ash Trees from EAB was issued in May 2009. Both can be found at http://www.extension.iastate.edu/pme/EmeraldAshBorer.html.

--30--

http://www.extension.iastate.edu/news/2009/jun/060401.htm

Sources: Mark Shour, (515) 294-5963, mshour@iastate.edu

Laura Jesse, (515) 294-0581, ljesse@iastate.edu

Donald Lewis, (515) 294-1101, drlewis@iastate.edu

Jesse Randall, (515) 294-1168, randallj@iastate.edu

Jeffery Iles, (515) 294-3718, iles@iastate.edu