Communications. 2G9 



only an attendant result, induced or made possible by the pre- 

 viously enfeebled condition of the plants. 



The question arises, In what way, if any, can the disease be 

 prevented ? Various methods have been tried and claimed by 

 some to be successful remedies, but on an extended trial they have 

 not proved generally satisfactory, and the natural conclusion is, 

 that the benefit attendant upon their previous use came from other 

 causes rather than from any virtue in the so-called remedies. 

 Sulphur, lime, ashes and dust have all been tried, but are of little, 

 if any, benefit. They may destroy the open air portion of the 

 fungus, but the strength, the real life of the parasite is within, 

 and no external application will be of any avail in causing more 

 than a temporary check, unless it also destroys the plant itself. 

 A few threads and spores on the outside may be destroyed, but 

 these will soon be replaced by a new growth from within. 



Cutting off the tops as soon as the presence of the fungus is 

 discovered has been lecommended. This may check its growth 

 for a time, but it is rare that it will prove a permanent remedy, 

 as the mycelia have usually occupied the tissues of the stalks and 

 well down to the tubers before the outward growth of the fungus 

 is noticed, and the part nearest the ground is that which is usually 

 affected first. Cutting away the whole top diminishes the amount 

 of the yield and also injures the quality. 



Ridging up the rows is also practiced by some, especially in 

 Europe, covering the tops with earth. In some cases very satis- 

 factory results have been reported from this practice; greatly re- 

 ducing the per cent, of diseased potatoes in the hills, but in other 

 instances the reduction in size and in market value of greater 

 numbers thus obtained, made the net returns less than they were 

 on portions of the field not thus treated. 



The means usually regarded as the most effectual and impor- 

 tant are those of a precautionary character. As avoiding, in 

 planting, ground where the crop was affected the previous season, 

 or proximity to such ground ; planting tubers wholly free from 

 disease; destroying all the diseased leaves, tops and tubers left 

 on the ground at the close of the season. This may somewhat 

 reduce the germs left over for the following season, but in 



