District forester gives update on EAB, how to replace infected trees

By MARY HOYER

SALEM ? With the potential destruction of the Emerald Ash Borer (EAB) in the headlines, it was no surprise that the most common questions at the presentation ?Caring for Our Trees? on Saturday by Iowa Department of Natural Resources (IDNR) Forester Lisa Louck at the Salem Library, were ?Should I treat or remove my ash trees?? and ?What replacement trees should I plant??

And the answer to both questions is: it depends.

The EAB was positively identified in a tree in Mt. Pleasant in 2014, which puts all of Henry County in the 15-mile ?treatment circle? ? an area in which ash trees are at risk. Louck pointed out that we don?t have enough long-term studies to understand everything about the pest, right now we should assume that any ash tree, if untreated, will be infested within 5-10 years.

There are treatments which seem to be effective in killing the larva. The forester recommends injection treatments, particularly for larger trees, because all of the pesticide goes into the tree. Soil drenching, in contrast, requires a treatment area equal to the root spread of the trees, which will contaminate a large area of lawn and soil. Injection treatments will need to be repeated every two years; other treatments only last a year.

You should choose to treat for one of two reasons: to keep trees healthy until replacement trees can become established, or if you have a healthy large ash that you really want to save. EAB seems to stay with one tree until it is destroyed so taking down a healthy, established ash tree doesn?t seem to make much difference in controlling the spread of the pest.

Whether you treat or not, you should get started on replacement trees. What trees you choose depends on your particular situation ? the location, the amount of sun, and most importantly, the mix of existing trees in your lawn, your neighborhood, and even your community.

Louck cautioned that we shouldn?t repeat our mistakes of the past by replacing one set of trees with another; diversity is crucial in controlling the devastation of any pest. Right now, for example, maple trees can be more than a third of the tree population in some communities. However, if everyone replaces their ash trees with, say, Kentucky coffee trees, that isn?t good either. She also recommended choosing a tree that is native to our area as it will be adapted to our conditions, and can best withstand the stresses of more extreme weather conditions and urban stresses such as soil compaction or road treatments.

Although existing trees may provide a great deal of shade, a replacement tree can become established without necessarily removing existing trees: most trees can handle some degree of shade, and almost any location will have sun enough of the time for a young tree.

If you do decide to treat your trees, make sure that anyone you hire has the training and experience to do the proper job: ask about credentials, about experience and recommendations. Moe information is available from the Iowa DNR, the Iowa Extension Service, as well as on-line resources from extension services in other Midwest states.

The forester also discussed tree planting and maintenance.

Louck said a tree is a life form and like humans, it needs adequate water, air and nutrition. Also like humans, a good beginning means a healthier tree more able to resist diseases and pests.

?Don?t plant larger trees on the right-of-way,? Louck remarked. ?Plant smaller trees like dogwoods, they will still provide shade.?

Proper tree care includes pruning when necessary, she said. She offered the following pruning tips:

? Prune limbs with a diameter between one and two inches;

? Prune all the way back to the main stem or branch union, not leaving a stub or more than one-half inch;

? Do not cut too deep or make a large surface wound;

? Do not use pruning paint, cement, wound spray, etc.;

? Do not prune in the spring, winter is the most ideal time and for some species, winter is the best time.

She urged those thinking of planting to give trees all the advantages possible ? plant them in a good site, one that is well drained and allows for unrestricted growth as the tree matures. Add mulch around trees. Mulch, she said, increases overall health in many ways, including competition from turfgrass.

Diversity is another key, the forester continued. Guidelines from the IDNR ?Trees for Kids and Trees for Teens? program relate that for any project less than 30 trees a maximum of three trees of each species should be planted. For projects over 30 trees, the rule of thumb is a maximum of 10 percent per species and 20 percent per genus.

For more information on tree planting, go to www.treeownersmanual.info.

Louck?s visit was sponsored by the Friends of the Crew Public Library.

Brooks Taylor contributed to this article.