Cercospora blight of asparagus

First appear on lower portions of the ferns after row closure and periods of high humidity. Symptoms are small, oval, gray to tan lesions (spots) with reddish brown borders on the needles and small branches. Spores of the fungus are produced on the lesions and are dispersed by wind and rain. Development of the disease depends on rainfall and humidity levels during June to August. Browning progresses upward from the lower ferns as conditions favor spread of the disease. Entire ferns may be blighted by late July in a wet year. The disease results in reduced photosynthesis of affected ferns. Yield loss the following spring is a result of reduced crown vigor caused by the early defoliation. Repeated yearly defoliation by Cercospora blight weakens crowns and reduces stand productivity and longevity. First-year asparagus is rarely affected by Cercospora blight.