2024 Author: Gavin MacAdam | [email protected]. Last modified: 2023-12-16 13:38
Alternaria, or dry spot, attacks tomatoes quite often. Often this attack also affects potatoes, as well as a number of other nightshade crops. At the same time, neither crops growing in open ground, nor tomatoes grown in protected ground are insured against Alternaria. The loss of fetuses as a result of damage to this ailment often reaches thirty to forty percent. And if you transport tomatoes over long distances, losses can be much higher - to a large extent, this is facilitated by the dense placement of tomatoes in boxes and boxes. Therefore, it is necessary to fight very actively with Alternaria
A few words about the disease
Initially, the formation of brownish zonal concentric spots begins on the lower tomato leaves. As the disease develops, the unfortunate specks gradually grow and often eventually cover the entire leaf blades. And this, in turn, often leads to the death of the leaves.
On the stems, as well as on the leaves, zonal oval specks appear, provoking their dry rot. Often, such spots are distinguished by a fairly solid depth.
As for the fruits of the tomato, the harmful ailment gets to them closer to the end of the growing season. Slightly depressed rounded specks of dark color are formed on them. Most often, these spots are located near the stalks. And if the season is characterized by high humidity, the development of conidial sporulation of rather dark, almost black shades begins on the surface of all specks. This sporulation usually takes the form of a velvety bloom.
Alternaria differs from late blight in that the spots formed when this disease is affected are dry under any weather conditions and are scattered over the entire surface of the leaves. Also, all the spots have a rounded shape and fairly clear boundaries. In general, depending on the causative agents of the disease and on the varieties of tomato, the symptoms of this ailment may differ.
The causative agent of such an unpleasant infection is the pathogenic fungi of the genus Alternaria, whose conidiophores are distinguished by their olive-brown or pale brown color and can be either twisting or straight.
A kind of "gateway" for the penetration of infection are all kinds of mechanical damage to the fruit. And its main sources are considered to be the conidia hiding in the remains of plants. Other nightshade crops (for example, potatoes or peppers with eggplant) are also considered as sources of infection.
Dry and hot weather (with temperatures from twenty-five to thirty degrees), accompanied by night dews or slight precipitation, usually wetting only the surface of the leaves, is especially favorable for the development of Alternaria.
How to fight
In the fight against tomato alternaria, it is important not to forget about such agrotechnical measures as deep autumn plowing and incorporation of plant residues - these measures significantly reduce the stocks of wintering spores, since soil microorganisms triumph over them. It is equally important in order to reduce damage to tomatoes and their spatial isolation, along with compliance with the rules of crop rotation. After cabbage with potatoes and eggplants with peppers, planting tomatoes is definitely not worth it.
An excellent effect is provided by prophylactic spraying of growing tomatoes with the preparation "Quadris". Ideally, such spraying is carried out before the first symptoms of the unfortunate misfortune begin to appear. However, it can be carried out even if the first spots are found. Such treatment provides plants with fairly long-term protection - up to three weeks.
If the development of Alternaria is massive, the vegetation is treated with a working solution of the drug called "Ridomil Gold" (0.25%). And for repeated treatments "Oxyhom" or "Bravo" are perfect.
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