Thursday, July 26, 2012

Asian Longhorn Beetle Threatens Trees


Many Tree Species Are At Risk



Another foreign intruder, the Asian Longhorn Beetle, has been detected in the US.  Originating in China, this destructive beetle has been introduced on freight containers entering the US. 
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The State of Ohio is only the fifth US state to report this infestation of this wood-boring beetle.  The first infestation was reported in 1996 in New York. New Jersey, Illinois, and Massachusetts have reported the ALB. 
risk map  Risk Map here is just that – the potential risk in a given area.  The red shadings are higher possibility of infestation due to the types of forest in the region. The blue areas are less likely to be come infested since the desirable host trees are less available.
sycamore mapleNorway maple
boxelder stinging buckeye tree
The hardwood species such as the Maple family of trees is highly preferred.  The Norway, sugar, silver and red maples, as well as box elder, and the State of Ohio Tree, the buckeye are host plants for the ALB.
One reason this beetle is so feared is that the list of preferred or host trees is quite extensive.  Besides Maples, and Buckeye, other trees on this list are elm, birch, sycamore, hackberry, ash, poplar and willow. 
planetree sycamoreSalix willow
Sycamore, Plane Tree              Willow

The preferred Maple varieties are potentially disastrous to Ohio as there are 7 billion board feet of maple wood currently in Ohio. This is a $2.5 billion of maples in Ohio, not to mention the $5 billion nursery trade and the 240,000 people employed in the green industry.   The New Hampshire maple syrup industry would be devastated by an ALB infestation.
maple syrup harvesting
So, how do we determine if this pest is present?   This is the second reason this beetle is so dreaded.  The female mates and deposits her eggs into the bark of the host. 
images (2)  As the larvae hatch, they burrow further into the tree.  They create tunnels in the tree's heartwood as they eat.  This greatly weakens the tree.
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The tunneling takes place for up to a year from the ovipositing of the eggs to the emergence of the next generation of adult beetle. 
images (5) Female depositing eggs, with male keeping guard.
images (9) The exit holes are about 3/8” and there are many holes on a heavily infested tree.  Sawdust and/or sap may be seen at the exit site. June through October are the months when the adults emerge, and the search for a mate starts the process all over again.  The fact that this process takes a year before the visible exit holes, a lot of damage can take place before we are even aware of the activity deep in the tree. 
Since there are no biological predators, the  steps to contain this pest are rather drastic.  Complete removal of infected trees is mandatory.  This may seem logical, but the expense is high.  No wood can be transported out of a quarantined  area – so all wood is chipped or burned.  Even the stumps and roots must be eliminated.
tree stump grinding 
The beetle can transport itself up to a half mile – therefore, host trees showing oviposit sites are targeted to be removed in that 1/2 mile radius of the infected tree.  Other host trees not showing sign of infestation are being treated with a chemical,  Imidacloprid, which is the active ingredient in Merit ™, an insecticide in the commercial and retail market.  Bayer Advanced™ is labeled for the homeowner and also has Imidacloprid in this systemic product.  
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This injectable application of Merit ™ is available and the bark and root flare needs to be treated.  The treated  tree takes several months for the chemical to be drawn up into the tree and branches.  Early spring applications are most effective, as the tree needs time to take up the product to poison the nymphs and adults as they eat. Unfortunately, the expense continues to mount with this pest, as chemical treatments need to be repeated yearly until new infestations are under control.
Even as there is some promise of containment,  the exceptions are cause for concern.  The Imidacloprid has not been approved for use on Maple trees that are harvested for the maple syrup industry.  Always  follow label instructions – the Label is the Law
Nematodes may become a natural control for the ALB, but so far they are not readily available or proven to be easily distributed into the forests.
dead larva of ALB by nematode  Dead larvae by a nematode.
Tree removal is the first line of defense in the fight to limit spread of the ALB.  More than 29,000 trees have been removed in the Worchester area of New Hampshire.  And the pest has been successfully eradicated in Illinois and part of New Jersey.  In Ohio, Clermont County is the only infected region, and  monitoring is ongoing in other areas of the state. 
Clermont county ohio ALB region
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IF the tell-tale symptoms of ovipositing or exiting become evident in your landscape, notify your County Extension Office or Department of Natural Resources. 
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