Atlantic Chapter

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Two Invasive Insects Threaten to Alter the Entire Character of Our Eastern Forest

Overview

     Two invasive insects, the Emerald Ash Borer (EAB) and the Asian Long-Horned Beetle (ALB), both from Asia, have found their way to North America recently, probably transported accidentally in wooden pallets.  Looking ahead, these two insects together appear to have the potential to drastically alter the entire character of our eastern forests by potentially eliminating all ash trees and maple trees from the forests.

     There is no way known to eradicate these insects once they are spread over a wide area.  Therefore the only way to save our forests is to prevent the insects from spreading much beyond the areas that are already infected.

Emerald Ash Borer expands in NY!:

The EAB attacks and kills all of our several species of ash trees and was first detected in Michigan in 2001. Since then it has been spreading eastward, state-by-state. It has been now been detected in New York State (the Randolph area of Cattaraugus County and Saugerties in Ulster County). The EAB has been spreading by leapfrogging 50 or 100 or more miles at a time.  This is thought to be the result of human transport of firewood, nursery stock and logs.  When left to its own devices the insect is believed to spread naturally only about one mile per year from light infestations and about 6-10 miles per year from heavy infestations.

Asian Long-Horned Beetle Overview:

The ALB attacks and kills our several species of maple treesand has made its way into urban areas of the United States several times. Until recently these urban outbreaks were successfully contained and eliminated by removing and burning all infected trees in the relatively small infected areas. However in 2009 a large, previously unrecognized infestation covering about 70 square miles was discovered in Worcester, Massachusetts.  The 70 square mile area is largely urban but also includes some natural forest area, giving scientists their first opportunity to see how this insect will behave in North American forests.  Based on what has previously been observed in urban areas, the expectation is that once it gets into the forests the ALB will attack and kill all of our several species of maple trees.  It is also known to attack birch, elm, and poplar trees.  The ALB infestation in Wooster is thought to have been there, unnoticed, for the past 15-20 years.  Actually, the residents apparently noticed the insects but did not recognize that they were anything out of the ordinary that needed to be reported.  Although the ALB has apparently been in North America longer than the Emerald Ash Borer, the ALB is thought by the experts to be the less urgent threat because it appears to spread more slowly.  (That is based on its behavior in the urban areas, although the jury is still out on how fast it will spread once it gets into the forests.)  Actually though, in the long run the ALB is believed to be the greater threat because the maple trees killed by the ALB are a larger component of our eastern forests than are the ash trees killed by the EAB.  My efforts so far have been focused on learning about the EAB, so I cannot say much more about the ALB at this point.

More Details on the Emerald Ash Borer:

Because the Emerald Ash Borer (EAB) has been regarded as the more urgent problem, more research has been focused on it.  Here are some facts of interest:

  • The EAB girdles the ash tree beneath the bark and it takes about three years to kill the tree.
  • New York now has a law limiting the transport of firewood to 50 miles or less. Tighter restrictions are recommended, but so far the NY Legislature has refused.
  • When people go camping they may buy firewood along the highway, take it to the campground, then take the excesshome.  That’s three locations.  Not good.
  • You can’t tell by looking at a piece of firewood whether it is infected with EAB or not.
  • Heat-treated wood is safe to transport - look for the APHIS seal of approval on the wrapper.  (APHIS is the Federal Animal and Plant Health Inspection Service.)
  • The biological agent BT (Bacillus Thurengiensis) might be effective because the insects come out from under the bark and consume leaves during a two-week adult stage.  (BT can be sprayed from a plane flying over the tree-tops, as is sometimes done when dealing with Gypsy Moth Caterpillars.)  However EAB adults are emerging throughout the summer; they do not emerge in unison.  Therefore repeated sprayings would be needed to eliminate the EAB from an area.  Further, real elimination seems unlikely.  In the case of the Gypsy Moth Caterpillar, spraying with BT can control the insect, but has never eliminated it.  Also, spraying BT is expensive: it is practical for use over s suburban neighborhood, but probably not for a large forest.
  • Although most of Michigan’s Lower Peninsula has been pretty well devastated by the EAB, the Upper Peninsula has so far been infected in only a few small patches.  The USDA Forest Service is using these isolated patches as test areas for trying different methods for combating the EAB.
Thursday, September 13, 2012
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