A northern California rosarian swears by a recipe for Habañero Tea that she sprays on rose leaves during the rose slug season. Naturally, in the preparation and use of this stuff, you don't want to get it in your eyes or on your hands. If you are asthmatic, you must avoid breathing the vapors and probably even using this stuff at all. All hot pepper vapors are an instant asthma trigger for me. For the rest of you...

2 dozen habañero peppers
2.5 quarts water

For concentrate: Wear rubber gloves when handling peppers. Cut the peppers in half and toss in the water. Bring to a boil, cover and simmer for about 15 min. Don't lean over the steam and avoid getting the oils in your eyes in any way. Let it steep while it cools. Strain. Refrigerate.

For spray: Mix 2 cups of the tea with a good squirt of dish detergent and a gallon of water in your sprayer and put a fine spray on the undersides of leaves. As with all spray materials, avoid getting the spray in your eyes, on your skin or in your lungs.

I wonder if that would fry midge larvae crawling up stems?

I can see rabbits running away from California. And swearing never to eat roses again.

But to the O.P. Are you talking about the really small slugs, almost inch worm like? If that's your problem, often they are not specific to your roses but are living in trees upwind of or overhanging your trees.

Habanero Tea....I can see that as a solution to pilfered lunchbags in company refrigerators.

The best thing I found for rose slugs was also certified organic by CA; spinosad. Effective, relatively clean, and not requiring follow=up. The darned things also seem to have two seasons in my area, spring and again in late fall.

Re: Habanero: I wonder if it would improve with effectiveness and decrease the volume if you used Thai hot peppers instead.

JimD

Do remember that there's no guarantee that rose slugs respond to those peppers the way we do. We respond as we do because of the concentration of capsaicin in the tissues of the fruits, but I don't know at all whether that chemical has any effect on rose slugs or not. (It has no effect at all upon birds. That's why you can add hot pepper flakes & chili powder to bird seed as a squirrel deterrent. Squirrels can taste the capsaicin like we can, but the seed eating birds cannot.)

In any case, I can't help wondering if the reason that spray works on rose slugs is the detergent. Detergents have a powerful way of cutting through fats and waxes. An insect's outer body (especially when it's a soft-bodied outer body the way a rose slug or an aphid is) is covered in waxes. If the detergent cuts through the waxes then when you cover the insect's body in detergent it becomes impossible for the insect to keep water inside its body. Thus, the insect dies of dehydration.

I don't know for sure, but I suspect that's what's really going on.

It's easy enough to figure out. Try spraying your rose slugs with detergent.