Potato Diseases. Part 2

2024 Author: Gavin MacAdam | [email protected]. Last modified: 2023-12-16 13:38

In the first part of the article, we figured out how the manifestations of ring rot and various types of scab (silver, powdery, common and lumpy) look on potatoes. The list of misfortunes attacking potato plantings, of course, does not end there, so now is the time to get acquainted with some other ailments - dry phoma rot, alternaria, rhizoctonia and late blight

Dry phoma rot

On the surfaces of the potato nodules attacked by this disease, dark, rounded, depressed specks, outlined by rather distinct boundaries, begin to form. As the misfortune develops, they grow, turning into sores covered with tightly stretched skin. Infected tissues are stained in pale brownish tones and begin to spread conically inward, separating from tissues unaffected by infection with intensely colored narrow stripes. And the potato peel begins to wrinkle and crack on the sly. By the way, sometimes destructive pycnidia can appear through the skin to the surface. In the fields, the spread of the pathogen occurs mainly with the wind or with rain, and in storage facilities the infection spreads from one nodule to another through mechanical damage and eyes with lenticels.

Alternaria

This attack is especially harmful in the southern regions. Its first symptoms can be seen on young potato bushes, which have reached a height of fifteen to twenty centimeters. Some time later, fifteen to twenty days before flowering, the plants begin to become covered with rather large dark brownish or brownish spots, often characterized by pronounced concentric zoning. If the humidity and temperature are favorable, such spots can be seen already on the second or third day after the infection has occurred. And after three or four days, as soon as the size of the spots increases to 3 mm, the formation of numerous conidia, colored in smoky gray tones, will begin in the infected areas. All organs attacked by the disease are fragile and fragile.

Rhizoctonia

This disease can manifest itself on potatoes in several forms. On nodules, lesions may appear as black scab or reticular necrosis (usually manifested in hot and dry weather). Also, pitted (deepened) spotting can form on them - as a rule, this occurs in the case of waterlogging of the soil and at a sufficiently low air temperature.

Dry rot begins to appear on the underground parts of potato stalks and on seedlings, which looks like rotten wood (brownish ulcers of various sizes). And for the affected aerial parts of the potato, stuntedness, twisting of the upper leaves along the central veins and wilting in the daytime are characteristic. Sometimes bizarre airy tubers can begin to form in the axils of the shoots.

Late blight

The very first signs of late blight can be observed already on potato sprouts. In some areas of the stems and on the lower leaves of the growing crops, dark brownish spots begin to appear, growing at a truly lightning speed. The leaves, blackened, dry out, and when wet weather is established, they often rot. On their lower sides, a characteristic whitish bloom is often formed, characterized by a cobweb structure. And on the nodules, you can notice sharply outlined, at first, grayish, and after some time, brownish specks of unequal sizes. All of them are quite hard and depressed. Under the spots, directly on the cuts of the nodules, characteristic rusty necrosis is clearly visible, which gradually deepen into the tissues in the form of wedges or tongues.