Saturday, December 7, 2013

My Magnolia has Black Twig Borer

While most ambrosia beetles attack diseased or dying trees, the black twig borer, Xylosandrus compactus, attack apparently healthy trees and shrubs.

I noticed yesterday that Little Gem Magnolia on the right had clusters of dead leaves at the end of several twigs. Today I cut the dead twigs back to a crotch and will burn them.

These beetles also attack Dogwood and Redbud, which may account for some dead twigs on Dogwoods that I had blamed on some other cause.

Adult females begin to emerge about the time dogwoods bloom. They bore into the twigs and form brood chambers in the pith of the stem. As many as six generations per year are produced, so spraying does little good. I need to be vigilant about watching for wilting leaves come spring and prune away suspect limbs and twigs. 

I only noticed the dead twigs when I went to admire the newly swept paths with beds mulched with leaves and pine straw.

1 comment:

  1. Always something in the garden to keep us on our toes! I had tip ends of limbs wilting and turning brown on the large White Oak we had planted west of the house. I called Extension and they said not to worry, a borer of some type and it would not kill the tree. I haven't seen them since! I hope you get yours under control.

    The paths look lovely and very neat!


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