Question
QUESTION: My crabapple tree has started dropping the ends of its branches this spring.  The smaller branches less than 1/2 inch in diameter are being sheered off cleanly, as if cut by pruners, at about a 45 degree angle.  Every morning we find another 8 to 10 small branches on the ground.  I live in NH and the tree has been budding for the past 2 weeks whild this has been going on.  The tree is now in bloom, but half the crown is missing.  What is wrong and how can I fix it?

ANSWER: There are a couple insects that can cause the twigs to break off.

Twig girdler--A species of long horn beetle that attacks most hardwoods including dogwood, basswood, redbud, poplar, oak, persimmon, pecan and many fruit trees. A typical infected tree will exhibit small cleanly cut branches on the ground and sometimes dangling branch tips within the tree. The adult female twig girdler chews a V-shaped groove around a small branch, girdling it. She then deposits an egg under the bark in the upper portion of the branch above the V-groove. This is because the larvae of the beetle cannot live in healthy sapwood.

Twig pruner---Also a species of long horn beetle that attacks many of the same tree species, and its damage looks very similar to the twig girdler. On a closer look, the fallen twigs have a ragged edge along the bark of the twig. This is because this beetle larvae bores deep within the twig and spends this stage of its life cycle chewing its way out of the twig. Eating in concentric circles, the larvae reaches the bark, the branch is weakened and falls off.

About the only way to control the twig girdler and twig pruner is to collect the severed twigs containing the larvae and destroy them by burning, shredding, or removing the twigs from the area. Control of these insects with insecticides is not practical.

Here is a web link to pictures of this damage.




http://extension.missouri.edu/publications/DisplayPub.aspx?P=g7276

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QUESTION: Thank you.  I had considered these insects as the cause, but the pictures and descriptions don't really match the damage to my tree.  The photos all show a 90 degree angle of cut on the branches.  Mine are all cut at 30 to 45 degrees.  Also, the ridges on the cut ends are not concentric circles, but are parallel and go all the way across the cut ends.  Are these findings consistent with these insects or perhaps a larger animal climbing the tree and chewing on the branches?

Answer
These are the only insects that I know of that cut branches. It could be squirrels. The cut may not be a smooth one since they tend to chew rather than cut but on small twigs they would probably cut through the branch. Here is one picture I found of branches cut by squirrels http://www.penick.net/digging/?p=989

You should notice the squirrel activity if this is what it is. Might try a repellent thus might discourage the cutting.  Ro-pel is a taste repellent that can be applied to seeds, bulbs, and flowers; trees and shrubs; poles and fences; siding and outdoor furniture. Capsaicin is also a taste repellent, registered for use on maple sap collecting equipment.