Leaf Mold Or Brown Spot - A Disease Of Tomatoes In Greenhouses

2024 Author: Sebastian Paterson | [email protected]. Last modified: 2023-12-16 13:47

“Oh, we have started phytophthora,” the neighbors are worried. I went to one neighbor, to another, visited several acquaintances, looked. Everyone has the same picture: on the leaves of tomatoes there are light and yellowish spots, and from the inside - a gray velvety bloom with an olive tint. The most interesting thing is that such a picture was in all the greenhouses that I visited, and all their owners were convinced that this was late blight. However, they are all wrong.

This is not late blight at all, but the so-called leaf mold. Scientifically - cladosporia, or brown spot. It is not as harmful as late blight, because it does not damage the fruit. But then, when this disease develops, new fruits are no longer tied. The flowers dry up and fall off, and the set fruit grows very slowly. As a result, the yield of diseased plants is sharply reduced. The earlier the plant got sick, the less harvest it has.

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Cladosporium is a tomato disease that loves warmth very much, and it develops in our area only in greenhouses. For a successful course of the disease, high humidity is required. Only plants with a weakened immune system that do not like something are sick. In the open field, tomatoes do not get sick with them. As it turned out in practice, cladosporia is a very common disease in our greenhouses. In any case, I saw this disease much more often than late blight.

The disease begins with the fact that light spots of a vague shape appear on the lower leaves. At this time, the plants grow vigorously, bloom profusely. The first clusters of fruits are tied. Gardeners are happy, so they do not pay attention to the spots on the leaves. This is a big mistake, because it is at this time that the alarm must be sounded, the struggle must begin. Those gardeners who began to fight at the beginning of the disease usually won it. And they saved themselves by spraying the plants twice with Bordeaux mixture. If the disease was not recognized in time, then further light spots begin to gradually turn yellow, a well-visible velvet bloom appears on the inside of the sheet.

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This has already formed a mushroom plantation. As soon as you touch it, mushroom spores scatter in all directions, which settle around on the leaves, on the soil, on the elements of the greenhouse and even on our clothes and tools. Neighboring plants are infected, the disease spreads rapidly from the bottom up, affecting more and more plants. Later, the leaves affected by the fungus dry out. This is already a very advanced version of the disease. Now it cannot be defeated by any spraying. You can only suspend it, completely stopping watering. One consolation: where there is cladosporiosis, there is no phytophthora. These mushrooms are not friends.

Disease spores overwinter on plant debris, on the soil surface, on greenhouse parts. They even manage to get on the seeds. Therefore, it is very difficult to get rid of this disease, if it has appeared. It is necessary to rinse all parts of the greenhouse structure with copper sulfate, change the topsoil in the greenhouse, pickle the seeds before sowing - all this is laborious and ineffective. The disease will haunt your charges every year. It can be stopped by a sharp decrease in irrigation, which moisten the soil surface and thereby increase the humidity of the air. Since our gardeners often have no more than one greenhouse, the option of changing the place of tomato planting disappears.

You can do prevention. 10-15 days after planting the seedlings in the ground, when it takes root in a new place, you need to carry out preventive spraying with 1% Bordeaux mixture or copper chloride. Then every 10 days spray the plants with garlic tincture. Perhaps these activities will help, and perhaps not very much, especially if you miss at least one scheduled spraying.

Fortunately, there are a small number of cultivars and some modern hybrids that are resistant to this disease. So they will have to be limited so that the joy of growing does not turn into a long war with the disease.

When I began to study catalogs of tomato varieties in order to acquaint respected readers with varieties resistant to cladosporium, it turned out that there are several races of this disease. In addition, in most catalogs they write, after words of praise about the variety, simply: "Resistant to disease." And that's all. In practice, I know that almost all the varieties I tested with this characteristic had cladosporium disease.

In foreign catalogs, they indicate to which specific disease the variety or hybrid is resistant, even the race is indicated. We rarely do it. And yet, we managed to unearth several varieties. Here they are: varieties Admiralteisky, Cherry red, Ogorodnik; F1 hybrids: Blagovest (resistant to cladosporiosis race 5), Verlioka plus, Gunin, Donna Rosa, Druzhok, Crown, Kostroma, Red Arrow, Swallow, Leopold, Lelya, La la fa, Master, Margarita, Olya, Paradise delight, Northern Express, Titanic, Favorite, Flamingo, Energo.

Of the newer hybrids, one can name Torbay F1, Octopus F1 and Premier F1, on which I did not see traces of the disease, while the neighboring plants were completely affected by the disease. This year I have not seen any traces of the disease on the new variety of Handbag. There are probably other varieties and hybrids that are unknown to me.