Diseases and Insect Troubles 



Alexander Malcolm of Duns. Mr. Malcolm said 

 that he knew of a lot of Sweet Peas in East 

 Lothian which had gone off with streak disease, 

 although planted out in perfectly fresh ground 

 which had not been manured at all. Now I think 

 it is just possible the cause of the trouble in both 

 these instances was the same the lack of the 

 work of nodule-forming bacteria. In the first 

 instance because the plants were overdone with 

 nitrogenous manure ; in the second because the 

 bacteria were absent. My readers may not 

 all be aware that plants of the order Leguminosce, 

 to which the Sweet Pea belongs, are able to 

 absorb nitrogen prepared for them from 

 the atmosphere by the bacteria contained in 

 the nodules on the roots of the plants. These 

 nodules are easily observed by the naked eye. 

 It is thus that a crop of peas or clover is a good 

 preparation for a crop of a different character, 

 because the ground Rafter them is left richer in 

 nitrogen. Nothing is accurately known about 

 streak disease, and no cure has been found for it. 

 I have grown Sweet Peas in large and small 

 quantities for twenty years at least, and I have 

 never had any trouble with streak. I have seen 

 a few plants here and there in a big plantation 

 become sickly. Possibly they had streak disease 



