2024 Author: Gavin MacAdam | [email protected]. Last modified: 2023-12-16 13:38
Brown spot of cucumber leaves, also called olive spot or cladosporiosis, as a rule, attacks cucumbers grown at rather high air humidity in greenhouses. The spread of this scourge occurs through seeds infected with the spores of the fungus-pathogen. Very often, the development of the disease can be observed in fruits. In order to avoid significant crop losses, it is important to timely identify brown spot and take the necessary measures against it
A few words about the disease
At the very beginning of the disease, first single, and then numerous specks of brown color with a light center are formed on the leaves. All these spots are angularly rounded. Affected plant tissues are covered with a grayish-olive bloom.
On the petioles of the leaves and stems, the spots are deepened, oblong, with a characteristic olive bloom. And on the fruits, in addition to olive bloom, rapidly hardening yellowish droplets are formed. Curved fruits infected in the early period stop their growth. In general, in terms of a number of signs, the defeat of fruits with an unpleasant olive shade resembles bacteriosis, but at the same time differs from it by the appearance of plaque.
As the disease develops, a light transparent border forms around the spots. If you look at the leaves in the light, this border will be perfectly visible with the naked eye. Individual specks begin to merge, turning into rather large irregular sores.
The source of brown spot are seeds, as well as remnants of damaged vegetation, on which spores of the pathogen fungus often hibernate.
How to fight
Humidity in greenhouses must be reduced by ventilation or regular ventilation so that it drops to 80 - 85%. Also, the air humidity in greenhouses can be reduced by means of their air-heater heating. And the greenhouses themselves are recommended to be thoroughly cleaned and then disinfected by fumigating with sulfur dioxide (sulfurous bombs) for one or two days.
In greenhouses, it is very important to maintain the correct regime. If possible, sharp temperature fluctuations should be avoided, as well as a decrease in temperatures at night and in cold periods (autumn and spring) below 15 - 17 degrees.
It is very important to follow the rules of crop rotation, as well as from time to time to carry out deep autumn plowing. It is best to grow varieties resistant to brown spotting - Graceful, Nezhinsky 12, Dolzhik, Nerosimy 40, as well as VIR 517 and 516 hybrids. All infected plants, as well as plant residues, must be promptly eliminated from the site.
Plants grown in the open field are sprayed with one percent Bordeaux liquid or its substitutes at the first signs of brown spotting. If necessary, this event can be repeated after ten to twelve days. In especially difficult cases, "Hom" or "Fitosporin M" is often used. And for preventive purposes, some summer residents spray the vegetation with a preparation with the symbolic name "Amulet".
Dusting all cucumber leaves on both sides with ash or an ash mixture will serve as a good service - this tool is considered a universal assistant in the fight against various types of spots. And you can spray the vegetation from all sides with colloidal sulfur (for 10 liters of water - 40 g) or a weak infusion of mullein.
In order to "invigorate" the soil microflora, it is very useful to spray it with nettle infusion. To prepare such a tool, a plastic or enameled bucket (the main thing is that it is not iron) is stuffed tightly with carefully chopped nettle shoots collected before flowering, pour the mass with water and put it in a sunny place. Every day, the composition is actively stirred with a stick. These actions are repeated throughout the week, until the release of gas bubbles stops. The composition will be ready to use when it has a disgusting odor. For spraying, this mixture is diluted in a ratio of 1:10. And the resulting thick can be safely sent to the compost heap. In addition, it is useful to spray the soil with such an infusion throughout the garden, and not only in greenhouses.
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