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Know how to protect your trees from these killers

This story ran in the Herald News and features Davey Tree expert Andrew Hillman (pictured right) talking about insects attacking the local trees.

Published: March 15, 2013


Andrew _Hillman

By now, many people are aware that the emerald ash borer has been found in Massachusetts. In August of 2012, EAB was discovered in Dalton in the Berkshires. Although it took 10 years from the time it was first identified in Detroit to reach Massachusetts, EAB could show up around Fall River anytime. In fact, this major pest may already be here. People have moved it around by moving infested ash wood, in particular firewood. Most of the estimated 45 million forest ash trees in Massachusetts are west of the Connecticut River, but ash is a common street and landscape tree in eastern Massachusetts.

While many kinds of trees are susceptible to Asian long horned beetles, another very serious invasive, exotic pest found in Massachusetts, emerald ash borers only attack ash trees. Unlike Asian long horned beetle, there is little hope that emerald ash borers can be eradicated. In fact, it is assumed by many that all untreated ash trees in Massachusetts will be killed by emerald ash borers in the next several years.

So, what are the options? If you have ash trees, there are some important things to know about how emerald ash borers affect infested trees in order to make informed decisions. If you do not have ash trees, do not plant them! It is likely you will be just throwing your money away.

Emerald ash borers attack and eventually kills all native species of ash. This is the genus, Fraxinus, which is in the olive family. Mountain ash is actually in the genus sorbus and is in the rose family. It is not attacked by emerald ash borer, even though it has plenty of other pests.

The material properties of ash wood are interesting. Due to its low moisture content and relatively high BTUs/cord, ash was an important fuel wood for pioneers and homesteaders. Ash can be burned with little or no seasoning time, so as folks moved westward they often relied on ash for heat. Baseball bats have traditionally been made from ash. Its straight grain and ability to take a blow without shattering make it ideal for such uses.  

But recently published research conducted by the Davey Institute indicates that EAB-infested ash trees may become brittle and fail in unexpected ways. This has resulted in the development of safety guidelines for working in ash trees that can result in the loss of management options over time.

 For instance, an ash tree killed by emerald ash borers  should definitely not be climbed. This is also true if the infestation has resulted in the death of two-thirds or more of the crown. Thorough inspection by a trained arborist is recommended before any ash tree is climbed for pruning, removal, or any other reason.

The upper branches (tie-in and rigging points) are susceptible to failure one to two years after infestation. They may appear sound from ground level. All tie-in points should be carefully inspected. If EAB activity has occurred in a tree for more than one year, even if it appears sound, shock loading should be avoided. Shock loading occurs when branches or tree trunk sections are removed using ropes over rigging points in the tree.

What does all this technical stuff mean to the average homeowner or municipality with ash trees? Most importantly, it should be understood that as emerald ash borer infestation progresses, management options are reduced.

For example, if there is an ash tree in a back yard that cannot be reached by an aerial device like a bucket truck, it can be removed by climbing or felling. If there is no clear area for the tree to be simply felled, then it must be climbed.

As we have seen, climbing options soon disappear following an EAB attack. This means that a decision must be made to either treat the tree with effective insecticides or climb and remove the ash tree. Either way, the decision must be made early rather than later to avoid loss of options.

Ash trees can be successfully treated for emerald ash borer with several different pesticides. The conventional wisdom is that one should begin treatment when the emerald ash borer is within 15 miles. Knowing exactly when that occurs is often impossible. Treatment has been demonstrated to be cost-effective in many situations. Once EAB arrives in a community, within four years most if not all untreated ash trees will die. As emerald ash borer infestation progresses, management options decline.

A very good clearing house for the latest on emerald ash borer is the Society of Municipal Arborists EAB Toolkit, which can be found at www.urban-forestry.com. Here one can find important tools like a homeowner decision guide and links to new information and EAB research.

Andrew Hillman is a certified arborist/municipal specialist with Davey Resource Group on contract with the city of Fall River through a Mass. DCR grant. Community Voices is a weekly column featuring community-based experts or specialists.

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