Studies on tuber rot of potatoes due to phytophthora infestans (mont.) de by.

Late blight rot due to the fungus Phythopthora infestans is one of the most destructive diseases of potatoes. Losses occur in the field and in storage. An important feature of the disease is that it is frequently followed by secondary decay organisms which rot the tubers much more rapidly than does P. infestans. Tuber infections arise in several ways. It is a well established fact that spores produced on blighted vines fall to the ground through which they are washed to the surface of the young growing tubers where they germinate and initiate tuber infections. According to Link and Ramsey, 1932, the fungus may gain entrance into the stem end of a tuber by growing along the stolon of a diseased plant but this method of infection seems to occur only rarely. According to Link and Ramsey, 1932, Crosier and Reddick, 1935, and Barrus et al, 1940, the fungus may grow and fruit in and on heavy wet soils during wet seasons and thus spread underground from tuber to tuber. Tubers are almost certain to become infected during harvesting operations if they are dug while the fungus is fruiting on the vines or if the tubers are covered in the field by blighted tops. Rotted tubers in storage are usually due to infections which took place before or during harvesting but if moist air and temperatures above 41°F prevail in the storage room, the fungus may grow out of infected tubers and produce spores which may spread to nearly sound tubers. [...