Avoiding and controlling pests and diseases
Asparagus beetle – (Crioceris asparagi) This lousy pest produces larva who love to eat asparagus stems. You can control them with various natural sprays derived from plants, such as pyrethrum, spinosad, neem, or d-Limonene. You may also be able to control them with beneficial nematodes, applied early in the spring (when temperatures are above freezing) or in the fall. You can find beneficial nematodes at many mail order insectaries across the country.
Rusts (Puccinia asparagi) – This fungus attacks the stems first and then goes after the rest of the plant. It appears in the form of small rust-like flakes on the surface of the asparagus. Its flakes grow and finally burst, releasing a cloud of spores that will infect other asparagus. This can be deadly to your plants, but only if the infection is allowed to become severe. If your plant is attacked, spray or dust the infected stems lightly with sulfur, garlic or a fungicide (preferably organic) such as Greencure, which may work on rust. Then, burn, toss or hot-compost the stubble after it has died back in the winter.
Applying cornmeal at 20 lbs per 1,000 sq. ft. over the infected area may help prevent this disease from returning.
Asparagus grown in moist climates with frequent mists, rains or a wet spring season will be more prone to asparagus rust. Talk to your local gardening experts to see if you live in a rust-prone area and, if so, plant a rust-resistant variety. Mary and Martha Washington are both bred for their resistance to rust. While Martha Washington is more rust-resistant, Mary Washington is the better plant overall.
Fungal and bacterial rots (fusarium sp. and others) – These and other rots caused by poor drainage are the most serious long-term problem with homegrown asparagus, but the good news is that it is a disease you can prevent. In order to prevent these rots from taking hold of your asparagus, you need to plant them in well-drained soil that gets full sun, or in properly prepared raised beds. Always make sure the beds drain well and don’t “pond” in wet weather. If drainage is the problem, there are only two things you can do. Fix the drainage on site or move the beds to a more appropriate location and start over. If you already have a problem with fungus, try cornmeal (which both absorbs water and deters fungus). This can be applied at 20 pounds per 1,000 square feet.
A preventative application of a product that contains Mycorrhizal fungus, such as Garden-ville Mycorrhizal fungi, may be able to stop these diseases from ever occurring.