On May 14, 2009, the Minnesota Department of Agriculture announced that Emerald Ash Borer (EAB) is present in Minnesota. While it has long been suspected of being in the state, this is the first confirmed discovery of this destructive beetle. First found in the United States in 2002, this pest has killed tens of millions of ash trees in the United States and Canada. All species of ash (Fraxinus spp.), healthy or stressed, are susceptible to attack. In North America, ash trees are the only known host to Emerald Ash Borer. Mountain Ash (Sorbus) is not a true ash and is not affected. It is estimated that there
are over 900 million ash trees in the urban areas, yards, and forests of Minnesota. Homeowners, landowners and the state must decide how they will handle this pest and its destructive attacks on ash trees.
Description
The adult insect is a beetle about 1/3 to ½” long and metallic emerald green in color. The body is slender and tapers to the rear; it is widest just behind the head. The top of the abdomen beneath the wings is purplish-red. The adult insect is difficult to detect because it feeds in the canopy of the ash tree. The larvae feed underneath the bark layer. It belongs to the same group of insects (flat-headed borers) as the Bronze Birch Borer and the two-lined chestnut beetle. There are pictures showing insects similar to the EAB at The University of Minnesota Extension.
Life Cycle
The EAB has a one-year life cycle, possibly two years in colder regions. The adult female beetle lays eggs on the bark or small cracks in the tree. The eggs hatch in 7-10 days and the larvae tunnel into the bark. They feed beneath the bark layer creating serpentine galleries that disrupt the flow of nutrients and water through the tree. The larvae overwinter
under the bark, pupate in early spring, and then emerge as an adult in late May to August. After emerging, the adult beetles feed on ash leaves and mate. The female lays 60-90 eggs. Adult insects live about three weeks.
Symptoms and Damage
Symptoms of an EAB infestation include canopy dieback especially in the top third of the tree, epicormic sprouts (shoots coming from the trunk and roots), vertical splits in the bark, serpentine galleries beneath the bark layer, D-shaped exit holes, and increased woodpecker activity. Since woodpeckers may feed on the larvae, the increase in woodpecker activity may be the first sign a homeowner notices. Trees from 1” diameter to fully-grown mature trees may be attacked. Stressed, unhealthy trees are usually attacked first, but healthy trees are susceptible too.
Be aware that ash trees are susceptible to numerous other problems such as ash anthracnose, ash plant bug, stem girdling roots, environmental stresses and verticillium that may produce some symptoms similar to EAB. The University of Minnesota Extension website has pictures and information for many ash tree problems at ‘What’s Wrong with My Plant?’
Questions to Ask Yourself Before Treatement
• Is the tree already showing symptoms of EAB? Visit the MN Department of Agriculture website for the checklist ‘Do I Have Emerald Ash Borer?
• If EAB cannot be ruled out, contact the Forest Resources Extension and Outreach. Trained First Detectors are available to help you further. Or contact the Minnesota Department of Agriculture Arrest the Pest Hotline at 651-201-6684 or 1-888-545-6684.
• Is the tree within a 12-15 mile radius of an infestation site?
• What is the value of this tree to the home landscape?
• What is the cost of treatment? Treatment will prevent EAB in a currently uninfected tree. You will need to treat the tree yearly.
• What is the cost of tree removal vs. the cost of insecticide application or a new tree?
If You Decide to Treat Your Trees
• Imidacloprid, a systemic insecticide, is available to the homeowner. Imidacloprid is the active ingredient in these insecticides available at Bachman’s: Xytect, Bayer Advanced 12-Month Tree and Shrub Insect Control, Bonide Annual Tree and Shrub Insect Control, and Fertilome Tree and Shrub Systemic Insect Drench. It is applied once a year and will protect the tree for one year.
• Xytect is the highest concentration of imidacloprid available to the homeowner and has been shown to be highly effective at controlling EAB. Even ash trees in the early stages of infestation can be treated.
• Imidacloprid applications made in the spring (April/May) or the fall (late summer/early fall until soil freezes) have been shown to be equally effective. It is mixed in a bucket with water, and then the solution is poured evenly around the base of the trunk as a soil drench.
• To facilitate uptake, it should be applied when the soil is moist but not saturated or excessively dry. Soil moisture should be maintained for 7 to 10 days following application.
• Imidacloprid can bind to organic matter such as mulch, therefore pull mulch back from under tree before application.
• Homeowners wishing to protect trees larger than 20” diameter at 4.5’ above ground level should check with an arborist about having their trees professionally treated.
• Preventative treatment is also available from tree service companies.
• Unnecessary insecticide applications waste money. If EAB has not been detected within 12-15 miles, your trees are at low risk. Be aware of the status of EAB in your location.
If You Decide Not to Treat Your Trees
• Healthy, uninfected trees do not need to be removed from your home landscape.
• Provide proper care to keep your ash trees healthy and reduce stress, but keep in mind that healthy trees can be attacked too.
• Keep informed as to where emerald ash borer has been detected.
• Consider planting other tree species in place of ash.
What You Can Do to Prevent the Spread of EAB
It has been found that the insect moves only ½ mile a year from infected sites on its own. Much of its spread has been due to the transportation of infested firewood, other wood products, and nursery products. Quarantines are in place in affected areas to help reduce the spread of this destructive insect. Do your part to control the spread of EAB by not transporting firewood to campsites. Buy only from local sources that know the source of the firewood. Do not buy firewood from outside the state or transport firewood outside the state.
Watch for symptoms of infestations or areas with numerous weakened ash trees when visiting parks or hiking in the woods. Notify the MDA if you see anything suspicious. Be aware of the symptoms of EAB and keep informed as to its movement in the state.
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