Asparagus: Rust

Biology

Asparagus rust is a fungal disease affecting the spears and foliage. Early symptoms include the development of oval yellow spots on the spears. These spots contain the fruiting bodies of the fungus, which are the source of infection for new shoots. Later in the summer, symptoms appear on stems and foliage, which develop blister-like pustules. The pustules break open to reveal red-brown masses of powdery spores. In late summer and fall, these spores may appear dark brown to black in color. Onions and related species (Allium sp.) are also attacked. This fungus overwinters on old asparagus stems. Since the fungus develops on spears in the spring, harvesting the spears breaks the life cycle of the fungus. Moisture is required for infection to occur.

Management Options

Use Integrated Pest Management (IPM) for successful plant problem management.

Non-chemical Management

Select non-chemical management options as your first choice!

• Remove wild asparagus, wild onions, and related species to reduce sources of infection around plantings.
• Plant resistant cultivars. ‘Jersey Knight’, ‘Jersey Giant’, ‘Jersey Centennial’, and ‘UC-157’ have greater resistance than ‘California 500’ and selections of ‘Mary Washington.’
• Avoid overhead watering and space plantings to reduce humidity.
• Cut out infected spears and shoots when noticed.

Chemical Management

IMPORTANT: Visit Home and Garden Fact Sheets for more information on using pesticides.

• Use when harvest is completed. May give only partial control of the summer stage.
• The effectiveness of oils is unknown in the Pacific Northwest.
• Oils should not be applied within two weeks of any sulfur application or necrotic foliage may result.
• Do not use oils below 50° F, above 90° F, or when plants are under heat or moisture stress.
• Do not use when foliage is wet as good coverage is essential.

Approved Pesticides

Listed below are examples of pesticides that are legal in Washington. Always read and follow all label directions.

• Monterey Horticultural Oil [Organic]
  Active ingredient: mineral oil/pet distillate light [EPA registration number: 48813-1-54705]
• Safer Brand Garden Defense Multi-Purpose Spray Concentrate [Organic]
  Active ingredient: clarified hydrophobic extract of neem oil [EPA registration number: 70051-2-42697]
• This list may not include all products registered for this use.

Additional Images