Devil in a Green Dress
(Editor's Note: This article was originally published on September 30, 2007. It is being repeated this week as part of the Emerald Ash Borer awareness week. Your comments are welcome, but please be aware that authors of previously published articles may not be able to respond to your questions.)
It began very subtly, a few dead branches at the top of the tree. Leaves began to fall during the summer. We passed it off as heat stress; after all it had been a very hot dry summer. We thought that in the spring it would recover. It was the summer of 2002. Our two beautiful, 40-foot green ash (Fraxinus pennsylvanica) trees didn’t recover and we had to cut them down. Our once shady side yard was now exposed to the hot summer sun. Little did we know that we were among the first victims of a half-inch green insect that would wreak havoc and cause billions of dollars (that’s correct billions with a “B”) of dollars of damage in the state of Michigan and throughout the Great Lakes region.
The Emerald Ash Borer had arrived, eating its way through our forests and neighborhoods with a vengeance.
Adult Emerald Ash Borer
The most likely path into the U.S. was by hitchhiking on a shipping pallet made from ash. The target area was Western Wayne County about 20 miles west of Detroit. There are many automobile suppliers in the area and shipments arriving from Asia are a daily occurrence.
The EAB only feeds on ash trees, and southeastern Michigan was an ideal target area. You see, back in the late 1950s and early '60s, Dutch elm disease moved through the area killing most of the mature elm trees that lined the streets. Homeowners looking for a quick-growing replacement chose ash trees. White ash (Fraxinus americana), black (F. nigra) and green ash (F. pennsylvanica) trees were selling like crazy; nurseries couldn’t keep them in stock. By the late '70s and early 1980s the ash had replaced the stately elm and the shade tree of choice in most neighborhoods. Sadly no one thought of the word diversity when it came to planting trees.
During the summers of 2002 and 2003 ash tress began to show sign of a problem, 2003 and 2004 brought death to hundreds then thousands of ash.
Scientists from Michigan State University, Michigan Department of Agriculture, and the U.S. Department of Agriculture went to work finally identifying the problem as the Emerald Ash Borer. By this time the pest had spread to five surrounding counties and showed no sign of slowing down. Ash trees continue to die. None of the pesticides in use at that time had any effect on the EAB, more trees died.
More than 20 nillion ash trees have
been killed by the EAB in Michigan.
Quarantines were put into place, no wood from ash trees were to be moved from their counties of origin.
Trees were being cut down at an alarming rate.
The northern two-thirds of the state of Michigan is a major recreational area. Summer cottages, hunting camps and campground abound. With all of the trees being cut, firewood was abundant and folks began to haul firewood up to their cottage or campsite. Either they were not aware or didn’t care, but little did they know that they had hitch-hikers in their firewood: EAB larvae. The pest was spreading. It has now been identified in 79 of Michigan’s 83 counties.
Scientists were burning the midnight oil attempting to find something to stop this pest. Trials were under way testing beneficial insects and various chemical compounds.
The insect began to spread into northwest Ohio and across the Detroit River into southern Ontario.
The EAB generally has a one-year life cycle here in Michigan, zone 5 and 6; but can require a 2-year cycle in colder regions. Females can mate multiple times laying their eggs in crevices in the bark of ash trees. They can lay up to 60 to 90 eggs during their life time. They hatch in 7 to 10 days.
After hatching the larvae bores through the bark and into the cambial region. They feed on the phloem and outer sapwood. The S-shaped feeding trails wind back and forth getting larger as the larvae grows. These S-shaped trails are called galleries
Feeding is completed in the fall, and the pre-pupal larvae over winter in chambers excavated in sapwood or the bark. In late April or early May the adult borer emerges fro D-shaped holes they create in the bark
"D" shaped exit holes left by the EAB.The trails or galleries created by this insect can be quite extensive; they actually remove the cambium layer so that nutrients and water can’t travel from the roots up to the canopy.
Gallery made by EAB while feeding
Early detection is the key in eliminating this pest. It is extremely difficult to detect early infestation. Woodpeckers feeding on the larvae are one of the early signs. If you examine the barks closely you will see small D-shaped exit holes from where the adults emerged. Bark may split vertically above feed galleries. When removed you will be able to see the tunnels that have been made by the EAB.
Watch for wilting foliage and thinning of the upper canopy. Trees usually lose 30 to 50% of their leaves after two years of infestation.
The good news is that several new treatments are very effective in eliminating this pest.
Imidacloprid is a fairly new insecticide that has been very effective in killing the EAB. This product is only available to professional arborists or other certified professionals.
I was recently invited to attend a seminar conducted by Michigan State University and a group of arborists. A golf course had permitted them to conduct a two-year study to determine which treatments worked the best.
Trees were treated with different products and methods, other trees were not treated at all. It was extremely interesting to view the results.
Many products and methods were used in this trial
Trees that had a 50% dieback were saved by treatments of Imidacloprid
Applied by injection and a basal soil drench.
Equiptment used to inject insectcide into
the soil under pressuer.
Trees have a vascular system very similar to humans. By injecting the insecticide it is distributed very quickly throughout the tree.
One method of injecting product into
trees vascular system.
The majority of the arborists have concluded that fertilization and plenty of water are key to restoring a tree's health. The more stress that a tree is under the less chance it has to recover.
The recommended plan to treat an infected tree is an injection of the insecticide along with fertilizer and a root stimulator. Followed up in 4 or 5 months with a soil injection or soil drench of the same product.
Trees on righ and left have been treated, two trees in the center were not.
There is also a new product that shows great promise; it is sprayed directly onto the bark and has shown good results so far.
New product can be sprayed directly onto the bark
Those of you who live near states that have been infected with the emerald ash borer; keep a close eye on your trees. If you suspect that an ash tree has a problem contact your county extension or a certified arborist. The only way to eliminate this pest is early detection and treatment. The earlier you begin treatment the more successful it will be.
Keep your trees healthy, water during dry periods. Use fertilizer spikes on a regular basis. A healthy tree is less prone to attack than one that is under stress.
If you happen to have an ash that has been killed by the EAB it must be disposed of properly in order to prevent further spread.
Chipping, burning or removing to a certified sawmill to be cut into lumber are the suggested methods of disposal.
Paul’s Garden Tip
For years we’ve heard about using broken clay pots to line the bottom of pots to keep the soil from coming out of the drainage holes.
So many of us today use plastic pots and don’t always have broken clay pots lying around.
You can use coffee filters or used dryer or fabric softener sheets in the bottom of your planters to keep the soil in and the water will drain out.