200 DISEASES OF THE SWEET PEA 



sickness. With this system the parasite is 

 starved out for lack of the proper hosts. 

 With the sweet pea, the selection of hosts 

 for proper rotation is a difficult one. So 

 many of the cultivated and ornamental 

 plants, for instance, are subject to the root 

 rots which also attack sweet peas. The 

 safest method, perhaps, for seed grow- 

 ers, would be to have sweet peas alternated 

 every second or third year with a cereal 

 such as sweet corn, sugar cane, or millet. 

 Where soils are already badly affected, 

 sweet peas should be grown on the same 

 land every fifth or sixth year. 



(d) Fertilizers. Outdoor sweet peas 

 are not as yet known to suffer from eel 

 worm attacks. However, should this oc- 

 cur, increase of fertilizer will undoubtedly 

 prove to be a good method of handling 

 root knot by forcing the growth of the root 



