the; 'prevention of potato scab. 85 



like manner a given soil is more likely to produce a badly 

 scabbed crop in a wet season than in a dry season. 



The treatment or control of the disease naturally divides itself 

 into two main problems, namely : What measures can be taken 

 to decrease or eradicate the germs from soil already infected 

 and how can the infection of clean soil be prevented? 



MANAGEMENT OE INEECTED SOILS. 



Various methods of soil disinfection have been attempted, 

 usually by rolling the seed in some chemical disinfectant, mixing 

 the chemical with the soil or scattering it along the row, but this 

 is expensive and has usually resulted in partial or entire failure. 

 At one time it was thought that a practical treatment had been 

 discovered by Halsted of the New. Jersey station in using sul- 

 phur applied to the soil at the rate of 300 pounds per acre. The 

 results obtained on the station grounds were very satisfactory. 

 Favorable results from the use of sulphur were also obtained 

 by the Delaware station.* 



Many others have reported failure with this treatment, so 

 that the general consensus of opinion is that it cannot be relied 

 upon for constant results on all soils. Wheeler suggests that 

 the beneficial results obtained from the use of sulphur is due to 

 its gradual oxidation in the soil and consequent production of 

 acid.f If such is the case it would seem that the sulphur treat- 

 ment is most likely to prove beneficial on a neutral or slightly 

 alkaline soil. Many Aroostook soils are slightly acid already so 

 that the use of sulphur there might prove positively harmful to 

 succeeding crops like oats4 



It has been found that most field crops do better on a neutral 

 or slightly alkaline soil and that a large amount of soil acidity 

 may be exceedingly detrimental. In fact the potato itself does 

 better in a slightly alkaline soil, such as is most favorable to the 

 development of the scab. Fortunately it is not so sensitive as the 

 scab fungus, and the amount of acidity developed by green man- 

 uring is often sufficient to be very detrimental to the fungus and 

 not materially affect the growth or yield of the potato. 



* Del. Exp. Sta. Bui. 34, p. 19, (1896); Rep. 10, p. 45, (1S98). 

 t R. I. Exp. Sta. Rep. 12, p. 164, (1899). 

 X R I. Exp. Sta. Rep. 12, p. 165, (1899;. 



