30 



DISEASES OF CROPS. 



plants, " sucking " their juices, and thereby causing 

 disease. 



Prevention. — (1) Destroy all refuse from the pea crop, 

 as it harbours the resting-spores of this fungus. (2) Farm- 

 yard manure, from cattle fed on vetches and peas, should 

 not be used for manuring land required for peas and 

 vetches. The reason of this is, that the resting-spores of 



Fig. 10. — Pebonospora vioi^. 



The mould of Tetohes and peas (causing brownisli patches on the leaves, etc.). 

 A. Spore germmating, x about 164. 



the fungus, if present on vetches and peas, pass through 

 the alimentary canal without being destroyed. 



Cure. — When the crops are above ground, give them a 

 top-dressing of iron sulphate (| cwt. per acre). This gene- 

 rally destroys most fungoid growths. 



(6) The Parasites of Trefoil {Medicago lupuUna). 

 Several parasites which attack clover are foes of trefoil. 



