You have noticed that the leaves of your roses have little holes in them and are wondering whether they are suffering from a disease. They are not the culprit is the rose snail, a small caterpillar that leaves slime in its trail. You will know that it is the one responsible because it eats only the soft tissue of the leaf and leaves the veins behind. Unfortunately, there are no pesticides that can deal properly with these little pesky pests.
If you want to get rid of them you have to use a variety of methods preferably at the same time. One way to get slugs out of your roses is with beer. Pour some in a bowl and leave it near the plants overnight. The slugs are attracted by the smell of the beer and one they crawl into the bowl they drown. Pour the beer down the toilet in the morning. If you do this several nights in a row you will notice that the numbers of rose slugs in your garden will reduce.
Salt is also effective. The best thing to do is sprinkle salt directly onto the leaves at dusk. Slugs hate snails because it simply kills them on the spot. If you are wondering why you should use this treatment at dusk, it is because rose slugs do their best work at night. In fact, not just this treatment should be applied at dusk all rose slug treatments should be applied then because that is the time that they come out to feed.
You can also kill rose slugs using special pellets that contain poison. The only problem with these approach is that since you have no idea what is in the pellets you may end up harming your rose plants even further in the process.