Letters on the Diseases of Plants. 23 



first mentioned, but suggest that it is a concomitant of the microbe which 

 really causes the disease. Here again, however, the doubt as to the precise 

 course of the disease has not prevented these specialists from deducing from 

 their investigations certain remedies which are, on all sides, admitted to be 

 very effective. 



Remedies. 



1. Avoid seed from your scabby crops. 



2. Buy seed only under guarantee that it comes from a perfectly healthy crop. 



3. Where land has borne a scabby crop do not immediately again use it for 

 potatoes, unless the seed be soaked in corrosive sublimate or the land be 

 dosed with sulphur. 



4. Land lower down than that suffering from scab, and receiving drainage 

 from the contaminated land, may also develop the disease. If convenient, 

 avoid such land for potatoes. 



5. If land that is subject to scab is to be again planted with potatoes, or 

 if scabby potatoes must be used for seed, soak the seed for one and one half 

 hours in a solution of corrosive sublimate, made by dissolving 10 ozs. of 

 corrosive sublimate in 60 gallons of water. 



Corrosive sublimate, or as it is otherwise called, bi-chloride of mercury, is 

 a violent poison if taken internally, and should be handled and stored with 

 care. It must not be placed in contact with metals, as it corrodes them 

 rapidly, and at the same time loses its own properties. The solution used for 

 soaking the potatoes must be placed in a wooden vessel having no internal 

 metal parts. There is no danger in putting the hands into the solution, but 

 it would be well to rinse them afterwards in pure water. The solution does 

 not injure cut potatoes, and if the potatoes are to be cut for seed they 

 should be cut befoi"e being soaked, as the cutting of the soaked potatoes 

 would be ruinous to knives. Plant the potatoes without rinsing them, but 

 allow them to drain. Corrosive sublimate can be had from any chemist, and 

 costs from sixpence to a shiUing an ounce. Several bushels of potatoes may 

 be treated for a few pence, and the treatment is very effective. 



Sowing flowers of sulphur at the rate of I to 3 cwt. per acre along with 

 the seed potatoes appears to have been attended with a very marked diminu- 

 tion of scab, and the good effects of one such treatment are said to continue 

 more than one season.* 



6. Boil up the worst of your scabby potatoes and feed them to stock. Also 

 boil or burn the parings of such scabby potatoes as may have been used for the 

 table. Scab begets scab, and the more of it there is left about, the more will 

 be begotten to attack your future crops of potatoes. 



7. Disinfect all bins, bags, and other receptacles that have held scabby 

 potatoes precisely as for wet rot (See p. 22.) 



8. Do not store scabby potatoes along with healthy ones, though this 

 recommendation has much less force in connection with scab than in con- 

 nection with wet rot. 



9. In case you are troubled with scab, avoid for potatoes, barnyard 

 manure and such fertilizers as contain much lime. Wood ashes are not 

 desirable where scab is prevalent, and potash should be supplied in some 

 other form. Carbonates should also be avoided. There are plenty of artificial 

 manures so concocted as to avoid the above pitfalls and yet be very suitable 

 for potatoes. Moreover, it appears that such fertilizers are themselves to no 

 inconsiderable extent a remedy for the disease, especially on so-called sour 

 soils deficient in iime.t 



* 17th Ann. Eeport, New Jersey Ag. Exp. Station. 

 + Wheeler, Tower, and Tucker, R.-I. Exp. Station, Bull. 33, 1895. 



