Greenhouse and Nursery - Crysanthemum White Rust,

Fall mum growers are reminded to watch for Chrysanthemum White Rust. This is a disease that must be eradicated if found. The following is some information.

Chrysanthemum White Rust

Chrysanthemum white rust caused by the fungus Puccinia horiana affects cultivated chrysanthemum plants in the Family Asteraceae. The disease is not established in U.S. chrysanthemum production, and could have significant impact on both greenhouse and outdoor plants of chrysanthemum, as well as cut flowers. The disease has occasionally been found in United States nursery stock in greenhouses, but it is easily and quickly cleaned up when found. Symptoms include yellow spots on the upper surface of the leaves that are up to 5 mm in size. On the underside of the leaves, raised bumps or pustules develop which have a waxy, warty appearance and are light in color.

Growers are reminded that if you see signs of white rust on leaves or flowers of a plant you are growing in Delaware, contact the Delaware Department of Agriculture. Plants must be destroyed but you need to work with the DDA for proper destruction procedures.

Information in part from Nancy Gregory, Plant Diagnostician, Department of Plant & Soil Sciences, University of Delaware