Bean Diseases

• One of the drawbacks of growing beans in the family garden is their susceptibility to a wide variety of plant diseases, from bacterial blights to fungal diseases, including anthracnose, root rots, watery soft rot, Cercosspora leaf spot and powdery mildew. There are no cures for most of these, but for some there are reasonably effective treatments. Most bean diseases can be prevented, deterred or at least minimized by careful garden practices. Growing disease-free bean varieties and planting disease-free seeds also helps.
  
  

Resistant Varieties

• There is no known cure or recommended chemical control for the mosaic viruses, which are transmitted to beans by aphids and present in diseased seeds. There are relatively few pole bean varieties with disease-resistant traits. "Blue Lake" is resistant to the first "race" of bean mosaic virus and to common bean mosaic virus. Kentucky Blue, a cross between Blue Lake and Kentucky Wonder that produces earlier than both parents, is resistant to bean rust and is also an All-America Selections award winner. Helda is a very productive Romano-type pole bean resistant to common bean mosaic.
  
  

Disease-Free Seed

• Bean seeds are among the easiest vegetable seeds to harvest, dry and save for planting in later years. But don't do it if disease breaks out, however insignificant it may seem. Diseases introduced from seed to soil can multiply exponentially under the right conditions, wipe out your entire crop and contaminate the soil for two or three years. Plant certified disease-free seeds in disease-free soil to prevent both common blight and halo blight, and to avoid introducing fungal diseases.
  
  

Garden Practices

• The spread of most fungal diseases can be prevented with prudent garden practices. Plant beans only after soil is fully warm---at least 69 degrees Fahrenheit---to a depth of 4 inches. Allow adequate spacing for good air circulation and full sunlight exposure. Plant beans only in well-drained soil. Build raised beds if necessary. To avoid spreading fungal spores, never water with sprinklers or spray. Plant beans in fresh soil. Remove all plant and leaf debris and avoid injuring plant roots when cultivating.
  
  

Other Beans

• In case of severe disease outbreaks, consider growing bush-style bean varieties at least temporarily. Because bush beans represent a fairly recent breeding success, and because they are a successful commercial crop, there are many more bush or green bean varieties with good disease resistance, including French and Italian beans. The department of plant pathology at Cornell University regularly updates its Vegetable MD Online disease resistance tables.