Answer: Caterpillars are the larvae of either butterflies or moths. You may have a shrub somewhere in your garden that's attracting these adults and they then lay their eggs on your rose bushes. Unless you can identify the caterpillar and find the source, you'll just have to keep treating your roses. You can handpick and destroy these pests or use Bt (Bacillus Thuringiensis) to control them.
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