Several species can attack mums including the brown to black-colored chrysanthemum aphids and the greenish to pinkish green peach aphid. Aphids have many natural enemies such as the lady beetle and lace wing. Different caterpillars may be a problem from year to year. The caterpillars chew holes in the leaves and stems, and some may bore into the stems. These very small pests feed by sucking juices from the undersurfaces of leaves.
Mites are most damaging during the summer months since they favor hot, dry weather.
A fine webbing is apparent in extreme cases as the mites travel over the webbing. Since mites are not insects many insecticides are ineffective in controlling mites. The slug bodies are fleshy, soft, legless and slime covered. Most feeding is done at night and they rest and hide during the day. As slugs move about, they leave a trail of silver slime.