Preventing the Spread of the Emerald Ash Borer
Emerald ash borer (EAB) was introduced to the Detroit, Michigan, area in the mid-1990s. Since then, it has spread outward in an ever-expanding infestation. EAB is not a strong flier, so long-distance travel has been through people – movement of infested firewood, wood products and nursery stock. On its own, EAB travels about ½ mile per year. With human help, it travels 55 miles per hour or even more! Please, don’t move firewood.
EAB attacks all ash (genus Fraxinus) species that are native to the U.S. It does not attack mountain-ash trees, as they are not true ash species, but instead are in the genus Sorbus. EAB has a major impact on those communities with a heavy reliance on ash. In North Dakota, many communities’ urban forests are comprised of more than 50% green ash; in some towns that number approaches 80%. The importance of diversification can’t be stressed enough. For more information on trees that are adapted to North Dakota, check out the North Dakota Tree Selector.
Economic Impact of the Emerald Ash Borer
The economic impact of emerald ash borer is staggering. The city of Bismarck estimates that the removal of ash trees on their boulevards will cost over $5 million.
The financial impact of EAB is incredible. Direct costs include tree removals (don’t forget stump grinding) and planting replacement trees. For those people who want to save specific ash trees, stem injections with the chemical ‘emamectin benzoate’ have been extremely effective – but they’re definitely not free. Indirect costs are also large – losing a prime shade tree can result in an increase in electric bills by more than 25%. That loss of shade has also resulted in an increase in water bills, as exposed lawns have needed additional irrigation. Property values have decreased in some communities as the overall tree cover has declined. One study even found an increase in heart and respiratory diseases in those areas that have been hardest-hit by EAB.
Many North Dakota communities’ urban forests are comprised of more than 50% ash trees. In one study of four North Dakota small towns, the cost of removal-and-replacement was estimated from $22,000 to more than $163,000; that study was completed 5 years ago and costs increase every year. Insecticide injections provide an alternative to removals-and-replacements, and may be a cost-effective option for managing the urban forest. The EAB Cost Calculator from Purdue University allows users to compare the costs of different management alternatives.
Technical and financial assistance for developing community-level management plans is available from the ND Forest Service. Contact Gerri Makay at 701-652-2951 or email@example.com for more information.
Signs and Symptoms of an Emerald Ash Borer
The signs and symptoms of EAB are varied:
- dieback of the branches in the crown
- new branches sprouting from the stem
- D-shaped exit holes from the adult insects.
Unfortunately, each one of these can be caused by something other than the Emerald ash borer. Correct diagnosis and confirmation of the true cause of problems in ash trees is difficult but it’s critically important—treating for the wrong problem is a waste of time and money. At the other extreme, missing an opportunity to treat a problem is equally as bad.
EAB is tricky to diagnose for those who are not been trained. If you think that your ash tree has Emerald ash borer, please contact one of the following people:
Lezlee Johnson, ND Forest Service – firstname.lastname@example.org, 701-231-5138
Joe Zeleznik, NDSU Extension Service – email@example.com, 701-231-8143
Charles Elhard, ND Department of Agriculture – firstname.lastname@example.org, 701-239-7295
Treatments for Emerald Ash Borers
Treatments for EAB are available, but aren’t recommended for North Dakota at this time because the insect has not been found in our state.
Since EAB was discovered in the U.S., researchers have focused much of their efforts towards finding effective control treatments. Experimental results are variable – some treatments are highly effective, but others are less so. The latest research results can be found in the 2nd edition of ‘Insecticide Options for Protecting Ash Trees from Emerald Ash Borer’, which came out in 2014. A summary is listed below. Note that new research results are coming out all the time, so recommendations may change is the future. As always, follow all pesticide label directions carefully.
Spray-type treatments with traditional broad-spectrum insecticides have been the least effective at controlling EAB. Quite simply, EAB adults can be active through most of the summer, and the insecticides didn’t last long enough to provide enough control. Additionally, obtaining a thorough spray coverage is very difficult, especially with larger trees.
Systemic chemicals, those that move within the tree, have proven more effective. Those with the active ingredients ‘imidacloprid’ and ‘dinotefuran’ have been researched extensively and are available in multiple formulations. Some formulations can be applied as a soil drench, a soil injection, a granular product applied to the soil surface, a bark-penetrating spray, or a stem injection (professionals only). These chemicals move through the tree to the tissues that EAB feed on. Control is not 100%, but these pesticides do a very good job of reducing the number of EAB larvae feeding beneath the bark.
The most effective insecticide treatment by far has been stem injections with the active ingredient ‘emamectin benzoate’. Test results have shown that this product provides better than 99% control of EAB larvae – and that level of protection lasts for at least two years. Many communities in the Midwest have found that a combination of insecticide treatments, along with timely removal of low-value trees, is incredibly useful in managing the ash trees in their urban forests.
Prevent the Spread of Emerald Ash Borers By Buying Firewood
Campground managers, foresters and many others are encouraging their clients “Don’t move firewood” this summer and throughout the year. Movement of infested firewood has been one of the main methods of long-distance dispersal of emerald ash borer (EAB). The legal regulations regarding firewood movement can be rather confusing, with some examples listed below:
- A federal quarantine is in place around all of the known EAB-infested areas of the U.S. Moving firewood and other ash products out of the quarantine area is illegal unless very specific, highly detailed rules are followed.
- ND Forest Service – prohibits out-of-state firewood at their campgrounds, but they will provide a free bundle of firewood for each paid campsite. Additional firewood is available for $3.00 per bundle.
- US Army Corps of Engineers – at campgrounds in North Dakota, firewood must originate within 100 miles of the campground, unless it has been officially certified as pest-free.
- MN Department of Natural Resources – in Minnesota, regulations were amended in December 2017 regarding firewood use on DNR lands including state parks.
Prevent the Spread of Emerald Ash Borers By Diversifying Your Landscape
Many years ago, American elm was the most common tree species planted in urban areas of the Great Plains. In some areas, it was the only tree species. Then, Dutch elm disease came and wiped out the tree canopy. People searched for a new species to replace the elms, and they came up with green ash – a tall, fast-growing tree that is tough enough to handle the urban environment. Again, people relied on a single tree species and green ash was overplanted. With the approach of emerald ash borer, the importance of diversity in tree plantings cannot be overstated.
Many species of tall deciduous trees are available for conservation plantings as well as in urban areas. (Some, such as cottonwood or boxelder are probably better suited to conservation plantings.) The ND Tree Selector is an online tool that helps users choose tree and shrub species based on a variety of characteristics. Are you looking for something that is fast growing? Or a tree that is long-lived? Perhaps a species with pretty flowers? The ND Tree Selector can help you find species to consider for your next planting.
And don’t forget to visit with your local professionals – city foresters, nursery owners and many others who have been planting trees for years can make recommendations about which species will do well – and those that won’t!
Additional information about EAB is available from the North Dakota Department of Agriculture. For more information about tree pests such as Dutch elm disease, gypsy moth, and others, please visit the North Dakota Invasives website.