274 Diseases of Truck Crops 



trouble does not seem to occur in the other States 

 where peas are extensively grown. In Colorado, 

 blight has suddenly made its appearance on a pea 

 area of 500,000 acres, seriously threatening the pro- 

 fitable growing of the crop. 



Symptoms. On the stems and leaves (fig. 51 b) 

 the disease may be recognized by watery olive green 

 to drab brown spots and by yellowish watery bruises 

 on the leaflets and stipules. The roots seem to be 

 free from the attacks of blight. Infection seems to 

 start on the stem, near the ground level, and from 

 there to work upwards. Lower leaves are usually 

 the first to die. Occasionally the infected plants 

 send out new shoots below the infected area. The 

 new growth is sometimes unmolested but ordinarily 

 it too becomes blighted. 



The Organism. Pseudomonas pisi is a short 

 rod, rounded at both ends, and motile by means 

 of polar flagella. It produces no spores, no cap- 

 sules, and no zooglea and no involution forms. 

 It produces no gas, and can stand drying of thirteen 

 days. 



Control. Certain varieties seem to be more re- 

 sistant than others. The development of resistant 

 varieties is recommended. All trash and diseased 

 materials should be destroyed by fire and -not fed to 

 animals. It is not known if spraying will control 

 this disease. In badly affected fields, spraying with 

 Bordeaux may be tried. 



DAMPING OFF, see PYTHIUM, p. 43. 



RUST, see BEAN, p. 262. 



