Scab in Potatoes.

King Country Chronicle, Volume II, Issue 96, 21 August 1908, Page 3

Scab in Potatoes.

The following notes are extracted from the summary cf a report of a series of trials-and investigations made at the Maine Agricultural Station :• — The use of untreated seed and the too common practice of reserving unsaleable, scabby tubers for planting may result in a rapid increase of potato scab. Scab is caused by a minute parasitic fungus. Soil conditions, the application of lime, ashes, chip dirt, etc.. may favour, the development of scab, but are incapable of causing it. Crop infection on old land may come from the soil, from the seed or from both. On new land the source is

largely from undisinfeeted seed. A'kaline soils, the use of stable manure, lime, ashes, and certain chemicals of an alkaline nature favour the fungus. Acid soils and certain other chemicals are unfavourable to it. Beet, and the roots of a few other vegetables are attacked by the disease, but the fungus may persist in infected soil for several years without the presence of known host plants. Badly infestsd soils should be devoted to such crops as grains, grasses, and clovers for as long a time as possible. Fertilisers favourable to scab should he avoided, and ''souring''' the soil by green manuring is recommended. On clean soils only healthy, disinfected seed tubers should be used. Manure containing uncooked scabby potatoes, or refuse should be avoided, but no other precautions as to fertilisers are necessary. Clean soil may be infected by means of tools, bags, baskets, etc., which have been in contact, with infected land or tubers. Small amounts, of seed arc- host disinfected by soaking : (a) Two hours in a solution of one pint formalin, to fifteen gallons of water, or (b(one and a-half hours in 2ez. of corrosive sublimate dissolved in fifteen gallons of water. FoV large quantities of seed, formaldehdye gas, generated by the use of

potassium permanganate, is the most practical disinfecting agent. Place seed tubers in bushel carts, or shallow slat-work bins in a close'! room. For each 1.000 cubic feet of sbace spread 2oct,. of potassium permanganate evenly over the bottom of a large pan or paii in centre of room. Four over this three pts. of formalin, leave room at cr.ee and allow it to remain tightly closed for twenty four lo forty eight hours.