156 



Diseases of Economic Plants 



often quite destructive. It was first observed by Beach in 

 New York in 1892. 



Usually the leaves are the parts first attacked. Here 

 large, translucent patches, brown in color, are produced. 

 These spots later dry, become papery in texture, and rup- 

 ture, leaving the foliage ragged and torn. Later infection 

 spreads to the pods, which develop watery, ulcer-like spots 

 without definite boundary, similar to those upon the leaves, 

 though often amber-coated. Attack upon young pods kills 

 them. 



Fig. 83. — Blight of bean leaves. After Fulton. 



This disease is carried over the season largely by infected 

 seed and is conveyed from plant to plant in the field by 

 insects. 



Diseased seed and seed from fields bearing the disease 

 should be avoided, and clean culture, including the burning 

 of all infected plant parts, should be practiced. The follow- 

 ing list shows the variation in resistance, the least susceptible 

 being placed first and the most susceptible last: Schindler's 

 Round Pod Wax, Refugee Wax Burpee's White Wax, 

 Grenell's Rust-proof Golden Wax, Wardwell's-Kidney Wax, 

 Dwarf German Black Wax, Early Valentine. 



