New ambrosia beetle marching across the US

Nursery growers have been struggling with ambrosia beetles for decades. In the southeast it is

Scopes-eye view of camphore shot borer fresh from a trap mixed in with granulate and other ambrosia beetle species. Photo: Andrew Ernst, NCSU.

Scopes-eye view of camphore shot borer fresh from a trap mixed in with granulate and other ambrosia beetle species. Photo: Andrew Ernst, NCSU.

primarily the granulate ambrosia beetle, Xylosandrus crassiusculus. In the Northeast and Midwest the predominate species is Xylosandrus germanus. These are tiny beetles that make tiny albeit lethal holes in trees. 

In the past several years a new species has been detected in several states including Florida, Tennessee, North Carolina, and just last month Virginia. This is the camphor shot borer, Cnestus (used to be Xylosandrus) mutilatus, and it is BIG. At least by ambrosia beetle standards this one makes holes as big as a pencil instead of then tiny 2mm holes made by other species. You can find out all about it in a thorough publication from University of Tennessee.  

We trap at 5 -10 nurseries every year around Johnston County, North Carolina. In 2011-2013 we captured 1 or 2 camphor shot borers each year. This year we captured about a dozen from at least 3 different nurseries. So it is here to stay and will probably become more of a problem over time. 

Camphor shot borer in a twig photographed by Matt Bertone, NCSU.

Camphor shot borer in a twig photographed by Matt Bertone, NCSU.

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Ambrosia beetles trickling out

After a cool spring I was beginning to think the ambrosia beetles would never come out. Although we have found a few early non-pest species we have not seen the main -granulate ambrosia beetle- until now.  We found a couple in traps at cooperating nurseries in Johnston Co, NC. Of course it is freezing this week which could delay them again. The same thing happened last year when we got a few at a time as the weather alternated

Frass tooth-pick from adult ambrosia beetles boring into trees. Photo: SD Frank

Frass tooth-pick from adult ambrosia beetles boring into trees. Photo: SD Frank

between warm and cold.

In experimental trees at lake wheeler and sentinel trees at nurseries we have not had any attacks but it is probably time to start management if you haven’t already.

Management of ambrosia beetle damage requires pyrethroid applications every 3 weeks to the trunks of trees. Ambrosia beetles usually attack below the first scaffold branches so you do not need to spray the canopy. Most folks apply permethrin with an airblast sprayer. We have tested a manual sprayer and fold more complete, even coverage.

You can read about it in a recent paper. The manual sprayer has two opposing nozzles to

Dual nozzle spray wand for permethrin applications. Photo: SD Frank

Dual nozzle spray wand for permethrin applications. Photo: SD Frank

quickly cover tree trunk with insecticide. It takes a little longer but uses less insecticide and reduces drift and secondary mite outbreaks. Ambrosia beetle attacks also increase when trees are overwatered so resist irrigation until it is warm and trees start leafing out. Summaries of ambrosia beetle biology and management can be found in industry articles, an open source publication in the Journal of IPM, and in a free iBook about nursery pest management

 

 

Ambrosia beetles emerging en masse

After a cool spring I was beginning to think the ambrosia beetles would never come out.  Yes, we have had a few detections around the state that I posted before but we have

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Characteristic frass toothpick extruded by ambrosia beetles as they bore into trees. Photo: S.D. Frank

captured very few in our traps.  In experiments we are conducting no trees have been attacked no matter how unhealthy or stressed. Until today.  Yesterday I got a report from the foothills that the first granulate ambrosia beetle was captured. It was 80 degrees in Raleigh yesterday and our traps filled up.  This morning we had two attacks at our experimental nursery on Lake Wheeler road.  I image when we check tomorrow there will be even more.

Management of ambrosia beetle damage requires pyrethroid applications every 3 weeks to the trunks of trees. Ambrosia beetles usually attack below the first scaffold branches so you do not need to spray the canopy. Most folks apply permethrin with an airblast sprayer. We have tested a manual sprayer and fold more complete, even coverage.

 

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Dual-nozzel sprayer we made to spray trees for ambrosia beetles. Photo: S.D. Frank.

You can read about it in a recent paper.  The manual sprayer has two opposing nozzles to quickly cover tree trunk with insecticide. It takes a little longer but uses less insecticide and reduces drift and secondary mite outbreaks.

Granulate Ambrosia Beetles active!

Nurseries throughout the state have reported Ambrosia beetle captures in traps and attacks on trees. Granulate ambrosia beetles emerge in early spring and attack many deciduous trees.  They have been reported to damage over 100 species of trees.  However, species most commonly reported to be damaged in North Carolina nurseries are styrax, dogwood, redbud, maple, ornamental cherry, Japanese maple, and crepe myrtle and magnolia. The best way to prevent damage is to apply a pyrethroid such as permethrin or bifenthrin to tree trunks. Beetles generally attack below the first scaffold branches so spraying entire trees is unnecessary and can lead to mite outbreaks. An insect not is available here.