20 AGRICULTURE OF MAINE. 



way of disinfecting such tubers since the fungus rests securely 

 buried within their flesh. 



The potato scab — often troublesome locally — is another 

 fungus disease, of which the germs live over winter on the sur- 

 face of infected tubers, and often of those that appear sound. 

 It also lives over in the soil, apparently persisting indefinitely 

 in a soil which is rich in humus and lime. 



While other potato diseases are known, it is beHeved that most 

 of the serious loss in New England is due to one or another of 

 the causes already mentioned. 



Having catalogued the diseases as to their causes let us now 

 note the more practical side of the matter — ^the rem.edies. 



In the first place let the emphasis again be laid on the impor- 

 tance of more attention to soil conditions — humus and tilth — and 

 to cultivation with the view of securing the fullest vigor of plant 

 and conserving for its use the available moisture. These pre- 

 vent tip-burn and make the large crop possible providing the 

 other diseases are warded ofif. How then is this last step to be 

 taken ? 



Precautions against scab must precede the planting. If the 

 germs are already in the soil the only way is to avoid planting 

 to potatoes for a number of years — five at least — and meanwhile 

 the land had best be in grain or grass crops. But it Js easily 

 possible to guard against the other source of danger — viz., seed 

 infection. This is effectively done by disinfecting either with 

 formalin solution ( i pint formalin in 32 gallons water, soak 2 

 hours) or corrosive sublimate solution (i oz. corrosive sublimate 

 in 8 gallons water, soak ij^ hours). For larger growers it may 

 prove easier to fumigate with formalin vapor. Our results have 

 indicated that if properly done this is fully as effective. The 

 formalin may be vaporized either by evaporating over a lamp 

 or by the permanganate method. 



The use of 3 pints of formalin per 1,000 cubic feet of storage 

 space is advised. This may be directly vaporized over a lamp, 

 but the permanganate method of generating the gas advocated 

 bv Evans and Russell of the Maine State Board of Health is 

 preferable. Place 18 ounces of potassium permanganate in a 

 3 gallon earthen bowl, pour the 3 pints of formalin over it and 

 at once leave the room, closing it as tightly as practicable for 

 24 to 48 hours. 



