Asparagus rust is caused by the fungus, Puccinia asparagi. It overwinters as a spore on host plants. The pathogen can also attack other wild plants in the same family also some varieties of onions, chives, and shallots. The disease is very common during prolonged dry conditions. It attacks spears, stems, and ferns of asparagus. The pustules (circular areas) appear on the attacked stems, and ferns. The attacked areas turn from green to red and finally to black. The attacked above ground plant parts dry up and this can lead to a weak plant which is prone to attack by soil-borne pathogens such as pythium, phytophthora, and fusarium wilt. The spores are transferred from one plant to another by wind.

Plant resistant varieties, destroy wild asparagus growing nearby, and spray with sulfur dust or other fungicides recommended in your state. Remove overwintering sites by cutting above ground parts in fall.