There are some years when you can’t win over the onslaught of certain pests, despite your best efforts. Some of our Hydrangeas, as well as other woody plants, have suffered from ambrosia beetle this year.
If the foliage on your trees or shrubs suddenly looks wilted, and you’re sure it’s not from lack of water, then inspect the stems of your plants more closely.
You might find tiny white ‘matchsticks’ coming out from the stems, as in the photo below. If so, you probably have ambrosia beetle.
Ambrosia beetles bore holes into woody stems and trunks where they deposit broods and also introduce a symbiotic ambrosial fungus that they feed upon. The bore holes and the fungus disrupt the vascular system of the plant, causing die-back.
Early spring is the best time of year to treat for ambrosia beetle, but sometimes you won’t see the damage until autumn.
It’s an amazing thing that such a tiny insect could do so much damage. Below, an adult ambrosia beetle and two larval stage beetles.