142 The Amateur's Book of the Dahlia 



cient circulation of air and too rich soil. Dahlias 

 must have fresh air at all times. If not, they 

 "damp ofiF" when young, or mildew when older. 

 Occasionally, when a long spell of cold, damp 

 weather comes, when books in the bookcases 

 and even shoes in the cupboards grow white and 

 furry, we may well expect mould on the dahlias. 

 Powdered sulphur is the best remedy. Dust it 

 on when the leaves are damp so that it will stick. 

 Cut out the blackened leaves and shoots, and 

 when the sun comes out again new growth will 

 soon appear to replace them. 



Tubers of dahlias are subject to a mild form 

 of scab, somewhat resembling potato scab. 

 While quite dormant it is safe to soak them for 

 two hours in a weak solution of formaldehyde — 

 one fluid ounce of formaldehyde to two gallons 

 of water. Dry them off before planting. 



Mosaic, another disease, attacks the roots, 

 and many remedies have been tried without 

 avail. Usually the tuber has a normal ap- 

 pearance when planted, but the growth is slow 

 and stunted and imperfect flowers develop if 

 any at all. This disease is carried over in the 

 root from year to year, but it never affects an- 

 other root if planted in the same spot where a 

 diseased dahlia had grown the year before. 

 Lately the use of bichloride of mercury solution. 



