Potato Late Blight

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

Potato late blight is one of the most harmful potato diseases that affects tubers and leaves with stems. It is also called potato rot. Even with a weak coverage of the tops of this disease, potato tubers are affected quite strongly. As a result of late blight attacks, potato yields can easily drop to 70%. And this attack is developing at lightning speed, so appropriate measures should be taken against it no less promptly

A few words about the disease

The first signs of destructive late blight can be observed already on tiny potato sprouts. On the lower leaves, as well as on individual parts of the stems, dark brown spots are formed, which gradually begin to grow. Blackened leaves usually dry out, although they can rot when wet weather sets in. In this situation, a cobweb, whitish bloom, formed by zoosporangia with zoosporangiophores, most often formed at the borders of necrosis, appears on their lower sides.

On potato nodules, sharp outlines are formed at first, grayish, and subsequently brownish, hard, depressed specks of various sizes. And on the cuts of the nodules, under the very spots, you can see numerous necrosis of rusty shades, quickly spreading in the form of small wedges or tongues inside the tubers attacked by late blight.

The causative agent of potato late blight is a mushroom-like phytopathogenic organism.

How to fight

The area for growing potatoes should be free of significant drops, well-drained and dries quickly after rains. The fact is that early foci of the disease often appear in low areas. And infected nodules are carefully discarded before planting. It is also recommended to carry out their pre-planting germination - this is done not only in order to accelerate their development, but also in order to reduce the significance of the influence of autumn rains, which to a large extent contribute to the attacks of late blight.

It is best to treat the tubers before planting with Maxim, which will simultaneously protect potato plantings from scab and rhizoctonia disease. The selection of potato varieties resistant to late blight will also do a good job. Among them are such as Lazar, Vyatka, Ogonyok, Naroch, Temp, Vesna, Arina, September and many others.

During the growing season, it is necessary to carry out timely soil cultivation to ensure the elimination of weeds and good moisture infiltration. It is extremely important to destroy all weeds for the simple reason that they create a very favorable microclimate for the development of late blight. And in order to reduce the likelihood of penetration of fungal spores to tubers with raindrops, it is recommended to form rather wide and high ridges above the nodules.

Treatment with fungicides is most often carried out without waiting for the first signs of late blight to appear - the fact is that the treatments started after the onset of the symptoms of this ailment in most cases are useless. Most often, the drug "Ridomil Gold" is used for spraying - it is used only once or twice per season, while observing an interval of one and a half to two weeks. The main thing is to keep within with such spraying before the start of the potato flowering. And then it is already allowed to use other fungicides (Revus, Shirlan, Bravo, etc.). Copper preparations can also be used. Treatments with all these means are carried out at intervals of a week and a half.

With the harvesting of potatoes after the natural complete withering away of the tops or after its removal, it is by no means worth delaying. Otherwise, the nodules can be affected by bacterial ailments, phomosis and rhizoctonia. And before sending the tubers for storage, infected specimens, which are an excellent medium for the development of a secondary bacterial infection, should be discarded.