Powdery Mildew
This fungi likes warm dry climates. This fungus attacks the following. Mums, roses, lilacs, and many other woody type plants. The fungus looks like a white powdery substance on top of the foliage, no it is not illegal. It can infect buds, leaves and the stem. It rarely will kill the plant but it will make it look bad. You can spray with neem oil or lime sulfur ask for it at your nearest nursery retail store. It may take several applications before seeing good results.
Verticillium Wilt