2024 Author: Gavin MacAdam | [email protected]. Last modified: 2023-12-16 13:38
Downy mildew, also called peronosporosis, is one of the most common diseases of lettuce. The most dangerous is the defeat of seedlings by this disease, because young and immature plants die very quickly. However, this does not mean at all that such an unpleasant ailment does not affect adult plants - it does, and quite often. Peronospora is equally damaging both in protected ground and in the open. And its harmfulness lies mainly in a decrease in the quality and yield of lettuce. The sowing quality of seeds also deteriorates significantly
A few words about the disease
When affected by peronosporosis, yellow spots are gradually formed on the upper sides of the lower lettuce leaves, which are characterized by an irregular shape. At first, the spots are limited to leaf veins, and as the disease develops, they grow, acquire a brownish tint and merge, as a result of which the lettuce leaves begin to die off. The ailment also does not bypass the lower sides of the leaves - a whitish loose bloom containing spores of the pathogen fungus appears on them. Occasionally, such a bloom can also cover the upper sides of the leaves.
Downy mildew is also quite harmful to the testes - plaque forms on the inflorescences when they are damaged, and the tissues are slightly pressed in and quickly darken. As for the seeds, they become rather puny and dull.
The causative agent of this unpleasant disease is a mushroom called Bremia lactucae Regel. Sporulation of this fungus represents conidiophores with conidia emerging in the form of a whitish plaque through the stomata on the lower sides of the leaflets. During the growing season, the pathogen is spread by these conidia. Moreover, if the air humidity is increased, then several generations of pathogens can form.
The overwintering of the fungus, the causative agent of peronospora, takes place mainly in the soil and in the remains of vegetation. The spread of this scourge also occurs through the soil through the spores of the harmful fungus-pathogen.
Peronosporosis of lettuce is widespread literally in all regions where this crop is grown.
How to fight
All kinds of plant residues should be promptly removed from all beds. It is also not worth walking past diseased plants - they must be eliminated. Compliance with the rules of crop rotation is no less important - you need to learn how to properly alternate crops, returning the salad to its former place no earlier than two or three years later.
Growing lettuce in greenhouses, cultivation rooms are systematically ventilated - an increase in air humidity in them is unacceptable. Also, when growing lettuce (regardless of whether it grows in greenhouses or in the open), it is important to ensure that there is no excessive thickening of crops - such thickening can enhance the development of not only downy mildew, but also a huge number of other diseases.
For planting, it is necessary to use only high quality seeds treated with dressing agents. To disinfect the seeds, they are heated for fifteen to twenty minutes in hot water, the temperature of which reaches 48-50 degrees. After that, for two to three minutes, the seeds must be quickly cooled in cold water, then dried a little.
They are used to combat peronosporosis and folk remedies. In particular, good results can be achieved with the help of iodine milk - a liter of skim milk is added to nine liters of water, and then five percent iodine is added to this solution (ten to twelve drops, no more). You can use a garlic broth or a decoction of horsetail, as well as an ash infusion - half a liter of ash is brewed in two to three liters of boiling water, then water is added in such an amount so that the total volume of the solution reaches ten liters, and they start spraying the plants.
If folk remedies did not give the desired result, you can proceed to the use of biological products (Fitosporin-M, Gamair, Vitaplan, etc.) and insecticides (Previkur, Kuproksat, Abiga-Peak, Strobi "," Hom "," Bravo ", etc.).
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