[908.] Wart Disease (Black Scab) of Potatoes. 673 



should not be used for potato growing. If practicable, it should 

 be applied to permanent grass. 



Preventive and Remedial Measures. — 1. " Seed " potatoes 

 from a diseased crop or from a field in which disease is known 

 to have occurred within six years should be avoided. If " seed " 

 potatoes are purchased in a district in which the disease is 

 common, they should be bought as soon after harvest as pos- 

 sible ; the sets should be freely sprinkled with sulphur (4-5 lb. 

 will dress 1 ton) and should then be stored in boxes or pits until 

 required. 



Tubers only slightly diseased may easily be overlooked, 

 and may cause widespread infection when planted. 



2. In the case of a disease like wart disease, which infects 

 the land gradually, it is necessary to detect and stamp out 

 the fungus as soon after infection as possible. When dis- 

 covered the entire plant affected should be carefully removed, 

 the useless portions burned, the tubers boiled without delay, 

 and the soil dressed with gas-lime. Further, when the field 

 is next planted with potatoes the piece of ground where the 

 disease appeared should be fallowed and dressed with gas-lime 

 at the rate of 4 to 5 tons per acre. 



If the attack has occurred in a garden required for frequent 

 potato growing, the occupier should dig out and burn, not 

 only the affected plant, but a considerable quantity of the 

 surrounding soil so as to ensure that every fragment of the 

 diseased plant is destroyed. Gas-lime should then be applied 

 to the soil. 



3. If fields worked on the four-course rotation have become 

 generally infected, farmers should replace the potato by some 

 other crop, so as to let eight years intervene before the next 

 potato crop is planted. The sets should be dusted with sulphur 

 before planting, as recommended above. 



4. In gardens and allotments in which the disease has been 

 noticed, potatoes should on no account be planted on the same 

 piece of land next season and one of the three following methods 

 of treatment may be adopted : — 



(a) The ground towards the end of April should be covered 

 with gas-lime (2 lb. to the square yard) which may be forked 

 into the surface soil to a depth of 3 in. After lying fallow 

 until the end of June it should be dug and prepared for cabbages. 



