The Control of Blight (Phytophthora Infestans) in Seed Potatoes by Tuber Disinfection

SUMMARY During storage the loss in seed potatoes through blight (Phytophthora infestans) is often severe if the crop is lifted while the fungus is sporulating on the haulms. It has been shown that this loss may be prevented by the disinfection of the tubers immediately after digging. The best results have been obtained when the disinfection was carried out on the same day as digging, immediately after the crop was lifted. Disinfection 3 or 4 days after digging gave little or no control of the disease. Both methods of disinfection employed, a 90 min. steep in a 01 per cent solution of mercuric chloride and an instantaneous dip (30 sec. to 1 min.) in a solution of a proprietary organic mercury compound, gave satisfactory results. Disinfection had no injurious effect on the subsequent sprouting of the tubers. The practice of “greening” the tubers is not likely to give any control of blight when wet weather follows digging.