Rose help please

Asked April 27, 2016, 2:03 PM EDT

My roses all have this white spot which later turns into something chewed with holes. My neighbor in the next block has the same thing. We are wondering if you maybe able to tell what it is (rose slug?) and how to treat it organically?
All of my roses, hybrid, old fashioned, climbing, bush, even the hybrid knockout roses are affected.
The photos are of the top leaves and the bottom of the leaves.
Thank you.

Montgomery County Maryland roses rose slug

3 Responses

Yes, your rose bush is suffering from damage inflicted by rose slugs. One of the critters is visible in the photo showing the underside of the leaves. If you enlarge the photo, look just to the left of the main twig in the center of the photo. There is a leaf with a rather large hole to the left of the vein. Look just to the right and up slightly and you should be able to pick out the larva.
http://extension.umd.edu/hgic/rose-slugs-shrubs
As suggested in the above page from our website, hand picking is the first option, but you could use horticultural oil (summer dilution) or a residual insecticide such as pyrethrins or acetamiprid.
LS

Thank you. I understand by the time you see the larvae, it's a bit too late to prevent the damage. Is there anyway of keeping the sawfly away from laying eggs in the first place?

Controlling sawfly larvae is a daunting task, but it can be done if you are willing to monitor your rose bushes regularly and know what to look for.
Many people resort to using a chemical control. There are a couple of systemic products sold as soil drenches that provide roses with fertilizer, fungicide and insecticide for the entire season.
LS