CORKY OR SCAB POTATO DISEASE.

Otago Witness, Issue 3101, 20 August 1913, Page 17

CORKY OR SCAB POTATO DISEASE.

In the last Journal of the Department of Agricultures (Ireland) 'hero is a useful report of experiments to test the best method of preventing or checking this troublesome disease.

It was extremely prevalent in the Clideon experimental plots last year, its attacks being favoured by the wet season. In some plots nearly two-thirds of the total crop was practically ruined, while the general average loss in the old land plots was about one-third of the crop. The disease is perpetuated by the plant-

ing of affected tubers or by planting sound tubers in contaminated land, ns well as, in all probability, in some oases by contaminated dung. It is seriously increased by the application of lime to the land; this has been confirmed by previous experiments. Experiments have also shown that by suitable treatment of affected seed potatoes with various fungicides (formalin, sulphur, etc.) a practically clean crop can bo obtained, provided the soil is not previously contaminated.

—Efficacy of Flowers of Sulphur.

During the past two seasons experiments were confined mainly to the difficult question of finding some means of freeing contaminated land from the pest, and last year the experiment was continued. Various applications were tried, such as an extra application of superphosphate, an extra application of sulphate of potash, and of .muriate of potash. In one plot each tuber was planted in a handful of wet sawdust, and another plot received flowers of sulphur at the rate of 6£cwt per acre. The best result was obtained with the sulphur, where not only was the amount of disease reduced to less than one-half of that in the untreated plots, but the total yield was higher than in any other case. This result confirms previous experiments carried out at Clifden, which have always shown that sulphur added to the soil increases the yield of potatoes and diminishes the attack of scab. Sumilar results ha\e been obtained by workers elsewhere as regards the increase of crop with potatoes and other plants when sulphur is applied to the soil, and they are interesting in connection with the modern question of the effects of partial sterilisation or disinfection of soils on the yields of the resulting crops, with which, however, it would be out of place to deal here. . . (Substantial as are the reductions in the amount of scab due to the methods of soil treatment above indicated they* cannot be looked upon from the_ practical standpoint as sufficient, and a suitable cheap soil disinfectant is still a great desideratum for this as well as for other purposes.