Rose disease - white fluff spots on canes

Asked April 9, 2020, 12:26 AM EDT

Hello! I have some highly overgrown climbing roses in Klamath Falls, Oregon. Some have white spots on the canes. (Leaves aren’t out yet.) The white is fluffy and can be scraped off and it is dark brown underneath. What is this and what should I do about it? Also, how do I know which canes are from the rootstock and which are the bred roses? Thanks so much! Gardening is saving my mental health right now and I’m always so very appreciative of the service you all provide.

Klamath County Oregon

2 Responses

Gardening is a GREAT way to hold on to our mental health right now, I applaud you for that! Looks like you are dealing with rose scale, something I don't see often in Klamath. Here is a link from UC Davis that discusses rose insects, including scale (scroll down page about halfway to get to scale):

The more or those infested canes you can just remove entirely, the better. Scale insects are typically treated with a systemic insecticide that will be taken up through the plant: it's nearly impossible to get good pesticide coverage through the waxy, scaly outer "shell" that the insect creates.

I hope you find this helpful, please let me know if you have follow up questions!
Thanks for using Ask an Expert.
Nicole



Hi again, upon review I realized I missed the part of your question about canes from rootstock vs canes from scion material. The graft on most roses is easy to see.- it will look like a scar or scab near the base of the plant. We can avoid canes emerging from the rootstock by making sure the graft is kept above the soil line. Canes that emerge from below the graft scar, are from the rootstock.

Have a great day, Nicole