THE ONION-SMUT. 173 



it would seem to be well to pull up and destroy plants as soon 

 as the smut makes its appearance. Practically, as Mr. Ware 

 suggests, the disease first appears when the plants are so 

 small that they cannot well be pulled. It is, however, very 

 desirable to pull up and burn all plants which reach any size 

 and are affected by the disease. The best plan is to burn over 

 fields where the disease has appeared. This is best done in 

 June, but it may also be done with advantage in autumn. 

 In neither case should the soil be previously dug up, for, 

 by so doing, the spores, most of which are on or near the 

 surface, are only the more likely to be removed beyond reach 

 of the fire. To prevent the spread of the disease, all agri- 

 cultural implements which have been used iti soil where the 

 smut exists should be thoroughly cleansed before using again 

 elsewhere. 



After all, the means of checking the disease which we have 

 just mentioned, are only partial. Some of the spores will 

 have remained behind in spite of all care; enough, perhaps, 

 to cause the next onion crop, if planted on the same spot, to 

 be diseased. The great question is, What becomes of the 

 spores which remain behind ? If an onion crop is started on 

 the same spot the next year, the spores may germinate and 

 reproduce the disease. If other crops are planted, of course 

 no harm is done. Then comes the all-important question, 

 For how many years do the spores of the smut fungus retain 

 their germinative power, and how many years after one onion 

 crop, which was affected by the smut, must one wait before 

 again planting onions on the same spot? On this point, testi- 

 mony is conflicting ; but about four or five years is apparently 

 the limit, for although some gentlemen, who have been so kind 

 as to communicate their views on this question, believe that 

 the smut has - reappeared in fields after twenty years' freedom 

 from onion crops, yet we must believe that, unconsciously, 

 these statements are much exaggerated. 



Mr. B. P. Ware assures us that the farmers of Essex 

 County, Mass., have found by experience that four years is 

 the limit within which it is unsafe to repeat the crop, and, by 

 a coincidence which would seem to warrant the accuracy of 

 the statement of Mr. Ware, Wolff states that the spores of 

 Urocystis occulta, the rye-smut (which, in their germinating 



