Treatment of Seed-Potato Diseases.

New Zealand Journal of Agriculture, Volume 56, Issue 5, 20 May 1938, Page 388

Treatment of Seed-Potato Diseases.

A. Stuart,

Instructor in Agriculture, Invercargill.

SEVERAL Southland potato-growers have for some years treated their seed potatoes with acidulated corrosive sublimate both for powdery scab and corticium disease. Not only are these diseases fairly well controlled with ■this treatment, but blight spores which may be on the skin of healthy tubers are also killed. Powdery scab, which must not be confused with common scab, is influenced by soil and climatic conditions, often being severe in cool districts. It will not appear in a crop unless the soil or the seed potatoes planted are affected with the powdery-scab organism. Once introduced into soil, it may remain for some years and be a source of danger to the clean seed planted. Both ’ these scabs spoil the appearance of a line of potatoes and lessen their market value. Corticium occurs on the tubers in the form of black sooty lumps or specks, the infection varying. These lumps cannot be removed by washing, but can be removed by the finger-nail, leaving the skin of the tuber intact. ' Corticium, when planted with the tuber, will attack the young growing shoots. Secondary eyes will then develop, rendering the plant late and producing a large number of shoots. The yield is affected, and, as a rule, few table potatoes are produced from such a plant. Seed is treated soon after grading. The procedure is to dissolve 8 oz. of

corrosive sublimate in 21 pints of commercial hydrochloric acid. and then to add the solution to 50 gallons of water, the mixture being well stirred. The potatoes are then steeped in this mixture for one hour and a half, and should be thoroughly dried before rebagging in clean bags.. A wooden trough is required to hold the mixture, ' as the solution will attack metal or concrete. For holding the tubers during immersion, wooden containers, made of light timber and widely spaced are an advantage.

'' A good method of drying is to suspend a length of bird netting in the open air in the form of a long table. The air will then circulate freely and the tubers will dry rapidly. If bagged while wet, the tubers showing powdery-scab ruptures will rot. Bags should not be immersed in the solution, as the sacking is also attacked by the mixture, which can be used three times before being discarded. The potatoes should be treated before sprouting in order to avoid injury in handling.

Tasmanian Potato.

A FARMER in the Aparima district, A Southland, received three oz. Southland, received three 2 oz. seed potatoes during last November from a friend in Tasmania. The seed were of the Brownell’s Beauty variety, and when sown were cut to give seven seeds. The resultant crop dug in early April revealed a beautifully fleshed crop of potatoes of a good, even, large size. The total yield from the three seeds weighed 34 lb., and an instructor counted fifty-five tubers all of at least 3 oz. in weight, while there were about two dozen tubers of the size of a large bean from the seven shaws. , W. L. Harbond, Instructor in Agriculture, Invercargill.