Resurrecting this 2014 article…
Last fall (2013) we got hit by some suspicious bulges on a couple of our roses. Our Eddie’s Jewel, completely unaffected by our winters, was hit rather hard by these things. The entire cane above the bulge typically dies. I didn’t see any of these on any of our mini rose, nor on any of the “old garden” roses. It turns out that we were zapped by Rose Girdlers, a type of beetle (actually the larva.)
A friend of Lynn’s sent the following: “the damage appears to be that of the rose rose girdler, a buprestid beetle that girdles the canes right under the bark. The tell tell sign is the swollen areas and the girdling inside the stems. The larvae are very distinctive. They are usually flattened dorso-ventrally and the thoracic area is flattened and enlarged. Overall, the larvae look like a car key.
“Unfortunately, these beetles are hard to control. Protective insecticides would need to be applied when infestations are really bad. Some of the insecticides with a long residual action have been taken off the market so there isn’t anything good out there that I would recommend anymore.”
So I did a little googling of the buprestid beetle and found a few things. Most of them seem to attack trees, but the method is the same. The adult bores a small hole, lays an egg, and the emerging larva eats away at the soft, yummy tissue under the bark. The rose reacts by swelling st the point of injury, but that doesn’t seem to do much.
The adults seem to be harmless, other than drilling holes where they are not at all wanted.
Here’s some info that I found on these things:
- Various pics of the larva. I didn’t see any of these in any of the cuts I made, just the damage left by them.
- This PDF has a lot of info on wood boring beetles in general, including some idea on controlling them.
- Bug of the Week has some nice info on these guys, as well.
Pics of the Damage
I don’t have any pics (yet) of either the adults or the larva. Hopefully our cold winter killed them off. Most of them anyway.
Click them images for a larger view. All of the pics below were from one plant, though several others were also affected. Sometimes they seem to attack a joint (where it branches off) and sometimes mid-cane.
Note the ring bulge and the tiny hole in the pic below. Is that the entry point? Where the egg was laid?
My poor rose…
And some tracks…