Chrysanthemum white rust, caused by Puccinia horiana, is a true rust that is regulated by a federal quarantine. The disease has been seen only rarely in the Northeast, and must be eradicated whenever it is detected. Two cases of this disease occurred in fall 2002 on Long Island, one in the garden of a hobbyist and one on garden mums at a commercial nursery site. The two locations were distant from one another and were not connected in any way. NY State Horticultural inspectors worked with APHIS to eradicate both outbreaks. Mum growers should watch carefully for symptoms of this rust, because it is far easier to eradicate when it is still a localized infection.