In warm and humid summers, the potato plague can halve the harvest. Blight has earned such a formidable popular nickname for its destructive power and speed of spread. If you notice the first signs of the disease on the potato field, then the time has already been lost. In order not to try to extinguish the fire at the time of its maximum ignition, you need not be lazy and pay due attention to the comprehensive prevention of the disease. This will be discussed in the article.
On average, late blight destroys from 10 to 20% of potato plantings, however, severe epidemics occur every three to five years, and then losses sometimes reach 100%.
The variability of the genetic structure and high adaptability explains the amazing survivability of the pathogen. More than 500 genetic versions of the infection have already been discovered, which continues to constantly modify and develop immunity to modern agricultural poisons.
From the moment it was discovered at the beginning of the 19th century, late blight has only strengthened its ability to empty potato plantations. If in the beginning, he hit only potato leaves, today the infection easily penetrates into stems and tubers. Previously, a comfortable temperature range for late blight was +8 … + 24, but today he is not afraid of a drop in temperature indicators to +3 and an increase to +27.
Phytophthora is a kind of hybrid of fungus and algae, which is propagated by spores. Spores of infection live in the cellar and in the ground for up to 4 years, and in some cases up to 30 years.
Signs of late blight on potatoes
Although the disease is characterized by rapid development, its first signs are easy to overlook. If you notice tiny black spots on the leaves of potatoes, it’s time to sound the alarm.
Without urgent measures, after 2-3 days the foci of infection will expand, turning into dirty brown spots. Gradually, these spots will merge with each other and spread to the stems and tubers. On the back of the leaves, you will also find a whitish light fluff – sporulation of the fungus. All this will lead to the imminent death of the aerial parts of plants and the defeat of tubers.
Usually, the disease raises its head closer to the end of July, but with a certain combination of weather conditions and an infectious background in the area, the infection can begin even before the potatoes bloom. Regular inspections of plantings will allow you to make a diagnosis on time and begin treatment.
Methods of infection and spread
A humid and moderately warm summer, plus the presence of late blight spores in the soil actually guarantees the infection of your crops with this formidable disease.
The methods of getting the infection on the site are diverse:
- with diseased seed tubers;
- with purchased seedlings of solanaceous crops (tomatoes, peppers) and imported soil;
- on garden tools and work shoes;
- with the wind (phytophthora spores can travel a distance of 2-3 kilometers);
- with some flying insects.
The most rapid spread of late blight is observed at an ambient humidity above + 75% and a temperature of +15 to +22 degrees.