As a result, plant vigor declines, spear size decreases, and weaker plants die. Symptoms are much more severe when plants are under stress because of excessively long harvests, poor drainage, competition from weeds, and damage from insects and diseases. Rust is another common fungus disease in asparagus. It appears on the surface of stems and branches as small rust-colored spots containing spores that spread the disease. In the fall, the rust-colored areas produce black, overwintering spores that can infect the plant the following year.
Severe rust destroys much of the foliage and reduces yields of the next year's crop.
Fungicides can partially control rust. Rutgers Beacon and Waltham Washington have some rust resistance. The asparagus beetle is a serious pest every year. Adult beetles resembling slender ladybird beetles lay rows of small, black, elongated eggs on asparagus brush. Insecticides can control them.