Characteristics: Asparagus plants that are infected with asparagus rust will usually first develop light green spots on the stalks of newly emerging spears, which develop into circular orange pustules. As the disease spreads and develops, it is characterized by red pustules on all parts of the plant, fern yellowing, and dieback. At the end of the season, the pustules turn black.
Cause: Spores that are allowed to overwinter on crop debris will infect the new growth in the spring. It usually becomes evident following the harvest season.
Management: Adequate plant spacing to allow for air circulation will help to inhibit asparagus rust development and spread. Adequate irrigation is also necessary. Fern growth should be cut back and removed from the garden at the end of the season.
Characteristics: Asparagus crowns that are infected with crown rot will change color to yellow/orange. The tissue may also look water-soaked.
Cause: Crown rot is caused by a soil-borne fungus. It generally infects plants that are waterlogged.
Management: Do not overwater. Provide adequate drainage. Do not plant in areas that have previously been infected by the fungus. Once infection sets in, more aggressive treatment may become necessary.
Characteristics: Fusarium wilt is characterized by stunted, yellow ferns. The base of the stalks will develop a noticeable red color running along the vascular portions of the plant.
Cause: Fusarium wilt is a soil-borne fungus that is spread through movement of the soil, planting in contaminated soil, and use of infected seed.
Management: Overharvesting (more than eight weeks in the fifth and subsequent years) can result in weakened plant development leaving it susceptible to Fusarium wilt. Maintain crown health with proper watering and fertilization.
“Asparagus: Fusarium Crown and Root Rot.” UC IPM Online. N.p., n.d. Web. 25 Feb. 2014. <http://www.ipm.ucdavis.edu/PMG/r7100211.html>.
“Vegetable Overview: Asparagus.” Sophisticated Gardening. N.p., n.d. Web. 25 Feb. 2014. <http://www.sophisticatedgardening.com/1175.html>.