Rust diseases are among the most destructive plant diseases, known to cause famine following destruction of grains, vegetables, and legumes. There are over 4000 species of rust fungi. Asparagus rust, caused by Puccinia asparagi, occurs in varying amounts wherever the plant is grown, and attacks asparagus ferns during and after the cutting season.
Fig. 1: Oval to elliptical-shaped lesions develop in the first stage of this disease.
Fig. 2: Tan blisters open to expose rust-colored spore masses in mid-to-late summer.
Spores overwinter on host plant residue, germinate in early spring, and produce new infections on growing asparagus spears. The light green, oval lesions are surrounded by a concentric ring pattern. In young plantings, before stalks are harvested, lesions develop yellow spore-bearing structures in concentric rings.
Wind and splashing rain can spread spores to branches and fern needles, where they germinate in the presence of water drops.
The orange spores are the key sign for this disease. Run your hand over an asparagus spear and examine your palm for orange-colored spores. Laboratory techniques may also be used for diagnosis of asparagus rust.
Plant rust-resistant varieties of asparagus, such as Viking KB3, Jersey Giant, and Martha Washington, all of which are reported to grow well in Minnesota. Remove volunteer asparagus within 300 meters of commercial plants, and locate new plants away from established fields. Plant well-spaced rows oriented in the direction of prevailing winds to maximize air movement and facilitate drying after rain. At the end of the season remove and destroy any infected stems.
- Gould, S. L. Disease-Resistant Vegetable Varieties. University of Minnesota Extension Service folder 02412, 1994.
- Howard R. J., J. A. Garland, and W. L. Seaman, eds. Diseases and Pests of Vegetable Crops in Canada. The Canadian Phytopathological Society & Entomological Society of Canada, 1994.
- Sherf, A. F., and A. A. MacNab. Vegetable Diseases and their Control, 2nd Ed. New York: John Wiley & Sons, 1986.
- Johnson, D. A., D. F. Mayer, R. Parker, and G. L. Mink. Asparagus Integrated Pest Management. Cooperative Extension, College of Agriculture & Home Economics, Washington State University, EB1383.