740 Grasses and Leguminous Crops in New York 



where rotations axe regularly practiced, the field pea usually fol- 

 lows the meadow crop. lu practice, it is found that the crop of 

 field peas is veiy effective in furthering the disintegration of the 

 sod left by the grass. It is this fact which has determined its 

 position in the rotation. The ground is left by the peas in 

 especially good condition for a wheat crop, and the increase in yield 

 of grain due to a preceding crop of field peas has been quite 

 marked. 



diseases of the field pea 



Powdery Mildew 



Powdery mildew, Erysiplie polygoni DC, is usually most 

 destructive on late-planted or late-maturing varieties of field peas. 

 It is also confined rather cloiselv to humid climates, where it some^ 

 times reduces the yield considerably. The remedy for this disease 

 lies for the most pai-t in the rotation of crops; but, where only 

 small portions of a field are affected, the disease can be controlled 

 by spraying with bordeaux mixture. If large areas are affected it 

 is not economical to spray. 



Leaf-spot or Pea-hlight 



Another diseiase which has been troublesome in the pea-canning 

 districts of both Wisconsin and Ohio ^ is the leaf -spot or pea-blight, 

 Ascochyta ,p{si Lib. This disease can be controlled in the same 

 way as powdery mildew by spraying with bordeaux mixture where 

 the area affected is small, but in large fields the farmer must 

 depend upon the rotation of crops. Although the disease is car- 

 ried on the seeds, treatment of the seed with insecticides or hot 

 water is not effective, because the germ of the seed is injured by 

 the treatment more quickly than are the spores of the fungus. 



1 Van Hook, J. M., Blighting of Field and Garden Peas, Chiefly Due to 

 Seed Infection — Pou-dery Mildew of the Pea. Ohio Agr. Exp. Sta. Bui. 173, 

 pp. 231-249, 12 figs., 1906. 



Eussell, H. L. Pea Blight. Wis. Agr. Exp. Sta. Bui. 228, pp. 4-6, fig. 1, 

 1913. 



