TREATMENT FOR POTATO SCAB

Otago Witness, Issue 3102, 27 August 1913, Page 16

TREATMENT FOR POTATO SCAB

Potato 60ah is caused by a fungus which also causes scabs on beets. Germs of the fungus occur in great numbers on scabby potatoes. Much of the loss from ecab is directly due to the use of infected seed. When the fungus is not present in the soil a clean crop is assured if clean seed is need. On the other hand, the planting of scabby seed usually results in a scabby crop. Soil conditions may be favourable to scab. Heavy soils and alkaline soils aro more favourable to scab than light soils and acid soils. Certain varieties of potatoes are more liable to scab than others.

Attempts at prevention should consist in tlio selection of resistant varieties, keeping the soil free from ihe fungus and disinfecting the seed potatoes. On badly infected soil it is cheaper to abandon potato-growing than otherwise to combat the pest. Flowers of sulphur (30010 per acre applied in the drills) has been recommended for such cases, but experience has shown it to bo an unreliable remedy, and not to be recommended. Ploughing under green rye sometimes partially obviates the trouble; but this. too. is unreliable. If soil is free from ■jjio scab fungus, any method of fertilisation is safe, but if infected alkaline fertilisers such as lime, wood ashes, and stable manure are to be avoided. The use of such fertilisers aggravates the trouble. Seed potatoes are disinfected either with corrosive sublimate or with formalin. Place loz corrosive sublimate in one gallon hot water. When dissolved, add enough water to make seven gallons, this solution should be made in wooden or earthen, rather than metal, vessels, since it corrodes metals. Soak the seed potatoes one and n-lialf hours in the solution. The treatment may bo made at any convenient time previous to planting, preferably several weeks before planting, since it may retard germination somewhat if used just before planting. The same solution may be used over and over. Corrosive sublimate is a deadly poison if taken internally; lienee all treated tubers should bo planted, buried, or burned. Mix one pint or pound of formalin (40 per cent, formaldehyde) with 30 gallons water. Soak the seed tubers In this solution for two hours. The same solution rnav be used several times if the barrel is kept covered to prevent los« of strength. The best results arc obtained when the treatment is made only a few days before plant-

The two methods are equally effective, but the formalin, treatment is preferable, because formalin, being- a liquid, is easily diluted, there is no banger of retarding germination, and the solution is not poisonous. By either method care must bo taken that the treated tubers are not infected by coming in contact with bags or boxes in which scabby potatoes have been kept.