238 The Canadian Horticulturist. 



REMEDY FOR THE POTATO SCAB. 



LATE bulletin of the Michigan Agricultural Experi- 

 ment Station gives the results of some experiments in 

 the use of Bordeaux mixture and of corrosive subli- 

 mate as preventitives of the potato scab. Inasmuch 

 as this scab has been causing much injury to the 

 potato in many parts of Ontario, it has seemed to 

 the writer that a brief summary of what is known in 

 regard to this fungus would be of interest to the 

 readers of the Canadian Horticulturist, taken in 

 large measure from the above-mentioned bulletin. 

 The germs of the scab fungus will remain in the ground in sound condition 

 for some years, hence it is not wise to plant this vegetable in ground that has 

 yielded scabby potatoes. 



The germs also retain their vitality when scabby potatoes have been fed to 

 animals, hence the manure from such animals should not be applied to land 

 in which it is designed to plant potatoes. 



Sound potatoes, that are free from scab, planted in ground not infested by 

 the scab fungus, will yield a clean crop, but if there is a possibility that spores 

 (or germs) of the fungus may be on the seed potatoes, or in the ground, then 

 the seed should be prepared for planting by immersion in the fungicide 

 mentioned below. 



Very scabby potatoes so treated before planting, if planted in uninfested 

 ground, will yield a crop nearly free from scab. Potatoes having a very thick 

 skin seem to be less easily injured by the scab than those that have a delicate 

 skin. 



Corrosive sublimate is the best remedy known at present. It should be 

 used in the proportion of two ounces to sixteen gallons of water. It dissolves 

 most quickly in hot water. Two gallons of hot water will dissolve two ounces 

 of the sublimate, and when dissolved, the fourteen gallons of cold water should 

 be added. Rain water is to be preferred, but not absolutely necessary. No 

 metal vessel or utensil should be used ; always use one of wood, glass or earthen- 

 ware. 



The seed potatoes should be clean, no clay or dirt adhering to them. For 

 convenience in handling small quantities, they may be put into sacks and 

 immersed in the corrosive sublimate solution. They should remain in it an 

 hour and a half. Longer time in the solution may somewhat lessen the amount 

 of scab in the crop, but it lessens the yield, while a less time — say only one 

 hour — does not sufficiently lessen the scab. The best results, when the freedom 

 from scab and quantity of crop are considered, are obtained by soaking the seed 

 not less than an hour and a quarter, nor materially more than an hour and a 



