POTATO DISEASES IX HAWAII. 
discoloration of the vascular or woody ring. Brownish or black 
discoloration at this point indicates Fusarium wilt or other infection. 
Such tubers are not suitable for seed. Then cut the tuber length- 
wise through the bud cluster at the end and through to the stem end. 
Then divide each half crosswise. With large tubers further division 
can be made, but the cuts should always be so made as to insure 
blocky pieces when possible. It requires about 22 bushels of seed 
adequately to plant an acre at the standard distance of rows 3 feet 
apart and seed pieces 1 foot apart in the row. Less than half this 
amount is commonly planted. 
Potato seed disinfection. — Diseases such as corky scab, Rhizoctonia 
scab, and rosette (PI. VIII), which are carried on the surface of 
the seed, can be controlled in some degree by soaking the seed in 
a disinfecting solution. Seed disinfection will be of little value if 
the soil is already infected with the disease for which the seed is 
treated. It is on the whole a better practice not to cut the tubers 
before soaking them in the disinfecting solution. For immediate 
planting, however, the tubers may be cut before dipping. 
The solutions most frequently employed for potato disinfection 
are formalin and corrosive sublimate. Either is suitable for the 
cork} 7 scab, but the evidence is in favor of the latter solution for 
the Ehizoctonia diseases (black scurf and rosette). 
The usual formalin solution is made up as follows : 
Formalin (40 per cent formaldehyde) pint 1 
Water to make gallons— 30 
The sacks containing the potatoes should be immersed in this 
solution for two hours, after which the tubers should be removed 
and spread to dry. Thirty gallons of the solution is sufficient for 
disinfecting about 30 bushels of seed. 
Corrosive sublimate has the disadvantage of being a deadly inter- 
nal poison, and it should be handled with this fact always in mind. 
The solution corrodes metal and therefore only wood and nonmetal- 
lic containers should be used. The formula is as follows : 
Corrosive sublimate ounces 4 
Water gallons— 30 
Dissolve the chemical in a few gallons of hot water and dilute to 
30 gallons. Immerse the sacks containing the tubers for two hours. 
then remove and spread the potatoes to dry. As this solution loses 
its strength after treating four to six lots of potatoes, fresh solution 
should be substituted. 
SUITABLE POTATO SOIL. 
Kind of soil and method of treatment. — So far as possible soil 
free from potato diseases should be chosen. As the Irish potato is 
a cool-climate crop, in the Hawaiian Islands it is at home at an ele- 
