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Problem with wild/prickly rose leaves bleaching out--not powdery mildew #875986

Asked July 05, 2024, 11:19 AM EDT

We bought a property 3 years ago and inherited a bunch of old-fashioned prickly rose bushes in various non-adjacent parts of the property. (I don't know the exact species, but Picture This called it a prickly/wild rose.) Regardless of the weather (we've had very wet and dry years, and this year is in between), they all have the same problem: Every year, the bushes leaf out nicely but fairly quickly thereafter most start to "bleach out" and turn white/gray. The veins mostly stay intact, and there are few holes in them. The bushes bud and bloom well and there's no issue on the branches or the blossoms, but the leaves go partially to completely white/gray; some shrivel a bit. We have not treated the roses at all--no fertilizer, no insecticides, no watering--they grow well in their outdoor setting. I can't find this specific issue in any online "most common rose diseases" posts. The leaf problem repeats every year and may even be getting progressively worse each year. NOTE: This problem doesn't spread to any of the many other plants on the property. Roses only. FWIW the previous owners told us these roses had been propagated in their family for over 200 years.

Windham County Vermont

Expert Response

Hi Andrea.  Thanks for contacting the UVM Extension Master Gardener Helpline.

This appears to be Rose Slug damage, a type of sawfly larva (Hymenoptera family). More
information can be found at the below Missouri Botanic Garden site which
includes some integrated pest management (IPM) strategies:

https://www.missouribotanicalgarden.org/gardens-gardening/your-garden/help-for-the-home-gardener/advice-tips-resources/insects-pests-and-problems/insects/sawflies/rose-and-pear-slugs-sawflies

I've also included some additional extension sites on rose slug/sawfly below, some of which also recommend treatment strategies:

https://hort.extension.wisc.edu/articles/roseslug-sawfly/

https://content.ces.ncsu.edu/roseslug-or-rose-sawfly

https://yardandgarden.extension.iastate.edu/encyclopedia/rose-sawfly-roseslug

I hope this information is helpful.  Good luck!
Jessie, UVM Extension Master Gardener Volunteer Replied July 05, 2024, 12:37 PM EDT

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