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.
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.
I just got some great pictures from one of great Extension Agents, Mark Danieley, this week
Sawdust accumulated around the base of an infested ash tree. Photo: Mark Danieley
of some pretty messed up ash trees in a parking lot. They have sawdust (frass) accumulated on the ground around their trunks and in clumps on the bark. Of course the first thought was whether the tree was infested with emerald ash borer. Mark noted however that the holes were round not D-shaped. Turns out the trees are infested with banded ash clearwing larvae. As the larvae feed they periodically shove frass out of their galleries to keep them clear. This time of year the larvae are getting very big and thus feeding heavily. Adults will emerge soon. Thus, the holes in the pictures are from last year when adults emerged front he same trees. That is why they did not have characteristic pupal casings sticking out of the holes.
Sawdust in clumps and round exit holes on tree bark. Photo: Mark Danieley