Saturday, October 26, 2013

Emerald Ash Borer

Fall color in the neighborhood

As fall arrives the ash that was in our front yard when
we purchased the home turns yellow...
... while the ash that was in our backyard
turns a beautiful red from the outside in.

and looking in either direction ash trees in other
neighbors yards are adding to the show.
It appears many ash were a popular landscaping choice in our area 5-15 years ago when many of the homes in this area were being landscaped.  Ash were thought to adapt better than many other species to disturbed soils typical of new subdivisions.  Wisconsin forests contain more than 770 million ash trees, nearly 7 percent of the tree population. In urban areas, the estimate it that, on average, 20 percent of trees are ash. 

Unfortunately, as the emerald ash borer spreads across the Midwest, it appears likely it will eventually take a toll in our area, as it has already been spotted in nearby counties.  Some neighborhoods have been planted in near monocultures of easy to grow ash trees, suggesting we learned little from the devastation caused to elm trees by Dutch Elm disease, once a very popular shade tree in this country.

Emerald Ash Borer (Agrilus planipennis) is an invasive, wood boring beetle. It kills ash trees (Fraxinus spp) by eating the tissues under the bark.  This metallic green beetle is native to East Asia. It was brought to the United States accidentally, in the wood of shipping crates from China. The larva (the immature stage of EAB) spends its life inside ash trees, feeding on the inner bark where we cannot see it. This feeding disrupts the trees' ability to move water and nutrients back and forth from the roots to the rest of the tree. The tree starves and eventually dies.  A tree that has been attacked by EAB can die within 2-4 years. It is estimated that more than 50 million ash trees are dead or dying in the Midwest because of this insect.

Based on current research, treatments are suggested only for ash trees located within 15 miles of a confirmed EAB site, or for trees located within a quarantined area.   Research suggests that insecticide treatments are significantly more effective on EAB-infested ash trees with less than 50% canopy dieback.   Trees with greater than 50% canopy dieback should be removed and destroyed in accordance with established guidelines.  Insecticide treatments must be repeated each year.  The Bayer Advanced Products, Bonide Annual Tree and Shrub Insect Control, Ferti-lome Tree and Shrub Systemic Drench, and Optrol are systemic insecticides applied as soil drenches around the base of an ash tree in mid-April to late-May and/or early-September to mid-October.  Two of the Bayer Advanced Products (Tree and Shrub Protect and Feed, Tree and Shrub Protect and Feed II) and Ortho Tree and Shrub Insect Control are available in granular formulations. 

On its own, the beetle will only fly a few miles. However, it is easily and quickly moved to new areas when people accidentally move emerald ash borer larvae inside of infested firewood, ash nursery stock, and other ash items.  The main defense in Wisconsin is to identify and destroy infestations before they can become widespread.  The following Emerald Ash Borer and Gypsy Moth quarantines are in effect in Wisconsin:

Green to Any Color 
Red to Any Color 
Yellow to White or Red

DATCPcertified firewood can be used at any WI State Park.
You can bring firewood to state campgrounds if it was harvested within 25 miles and obeys the permitted list above. No firewood from outside Wisconsin is allowed on state properties

If you have an EAB-infested tree that you would like to use as firewood, be aware that EAB can continue to emerge from the wood for two years after cutting. To avoid spreading EAB, split and leave the wood to age near where you cut the tree for two summers. After two years of drying, EAB that may have been within the wood will have emerged or died. The aged firewood poses little risk of introducing EAB and you may move it freely within the limits of the quarantine. 

A list of trees to consider planting as alternatives to ash include:

The Green Bay Botanical Garden publishes a map with the loction of "Ash Alternative Trees" suggested for our climate to view including Redpointe Sugar Maple, Red Sunset Sugar Maple, Commemoration Sugar Maple, Crescendo Sugar Maple, Shademaster Honey Locust, Sunburst Honeylocust, Orange Crush Flowering Crabapple, Purple Prince Flowering Crabapple, Satin Cloud Flowering Crabapple, Goldfinch Magnolia, Eye Stopper Amur Corktree, Shingle Oak, Crimson Spire English Oak, Legend American Linden, Redmond American Linden, Glenleven Linden, and Frontier Elm.
To maintain the long-term health and sustainability of our landscapes and urban forests we need to consider and plant a diversity of species and selections.  To latch on to one, or even a few selections, as replacements for ashes, invites us to repeat the mistakes of the past.   The devastation caused by exotic pests such as Dutch elm disease, chestnut blight, and emerald ash borer suggests the importance of considering species diversity in our landscapes. Exotic pests can be especially destructive because our native species may not have evolved and resistance mechanisms. A couple of rules of thumbs can help to promote species diversity:
-The '10% Rule' states that a single species should make up no more than 10% of the trees in an area, so if an especially destructive pest breaks out, 90% of the trees will remain healthy.
-The 'Look around Rule' states that when you look around, if you see a lot of a particular species, select something else.

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