Roses are an iconic symbol of love, a Valentine's Day staple and the quintessential garden flower. Some pests also love to eat them. Beetles, caterpillars, slugs and other garden invaders will move in whenever conditions are right. Once you identify the most likely source of the problem, you'll need to mount a counterattack.
Fuller Rose Beetle
The fuller rose beetle is tan in colour and small, reaching 1/2 inch in length at most. They feed during the night and are hard to spot during the daylight hours. They can make holes in rose leaves and create jagged cuts around their edges. If left alone, they can become a real threat to rose health. Some insecticides can get them under control and nematodes have proven effective when introduced into the surrounding soil.
There are a number of caterpillars that can cause rose problems. A few of these include the tussock moth, tent caterpillar, omnivorous looper, fruittree leafroller and the orange tortrix. Most of the time, there will not be many of them and the damage will be minimal, in which case the caterpillars can just be picked off by hand individually. In the event that a lot of damage is being done, a microbial insecticide can eliminate the problem. Spinosad and Bacillus thuringiensis are the most effective.
The rose slug is the precursor to the sawfly. It can be hard to identify because it looks more like a caterpillar than a slug. Sometimes they are black and sometimes they are greenish in hue, but they always have small legs, which is the main thing that makes them so caterpillar-like. Left on their own, they can cause the leaves of an entire rose bush to become riddled with holes. Methods for eliminating them include spinosad and insecticidal soaps.
Rose curculios, a type of snout weevil, are not usually found on rose bushes with pink or red flowers. They are particularly attracted to rose bushes with white and yellow flowers. Colouration is usually black or red and although they are small -- less than 1/2 inch -- they are still large enough to see. It is not often that enough of these would amass to cause severe damage to rose health, but if they do, they can be picked off by hand when they are spotted and the application of an insecticide should rid the plant of the remaining weevils.