Bacterial Diseases Of Tomatoes: Hollowness, Mottling, Apical Rot

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

Read part 1 Bacterial diseases of tomatoes: bacterial cancer, black bacterial spot

How to prevent bacterial diseases of tomato indoors

Pith necrosis (hollowness)

In recent years, he begins to pose a great danger. This bacteriosis is also characterized by high severity: a decrease in yield from premature death of plants in the household plots reaches 20-30%. The rapid manifestation of the disease is favored by changes in day and night temperatures, as a result of which condensation moisture is formed on the plants, as well as the introduction of excess norms of nitrogen fertilizers.

The first signs of bacteriosis are observed in the fruiting phase (the formation of the second or third cluster). In the central part of the leaf lobes (between the veins), light rounded-oblong spots appear, which gradually increase in size, and the leaf lobes curl upward (this is especially noticeable on sunny days). The manifestations of bacteriosis on leaves, which can be affected in any part of the plant, are very diverse: sometimes necrosis of the top of the central lobe of the leaves is noted, which spreads "with the tongue" along the central vein.

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Affected leaves look "scalded", although they retain their green color and have dark green oily veins. First, on the surface of diseased stems, small oblong spots are noticed, located mainly above the soil level by 25-30 cm.

Later, in most cases, on diseased stems, necrotic stripes of dark green color 25-50 cm long develop, which is one of the main characteristics of this disease. In this case, strong maceration (softening) of the affected tissues is possible with the destruction of the core, from which a mucous exudate of white or cream color can be easily squeezed out in a cross section; bacterial mucus is sometimes released from the scars on the stem remaining from the leaves.

At a later stage in the development of the disease, the stems often have cracks with voids inside with a brownish core tissue. In the main healthy stems (both in the root part and along their entire length), a large number of aerial roots are formed, changing color from white to rusty-brown, and in the places of their formation, the inner part of the stem is hollow. It seems that the plant wastes the contents of the stems for their regrowth. The root system of such plants usually shows no signs of damage.

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The process of wilting of plants develops gradually, and more often their final death is observed during fruiting. In mature fruits taken from diseased plants, double rings can be seen around the pedicel: dark brown in the center and light brown along the periphery. Sometimes short (4-6 mm) rays extend from this outer ring, in the zone of which cracks then appear. In some cases, the fruits are characterized by characteristic "mesh" of light gray veins.

The development of the disease is facilitated by the alternation of high daytime (above 25 ° C) and low temperatures, as a result of which drip-liquid moisture appears on the surface of the leaves of tomato plants. Under unfavorable conditions for the development of the disease, weakly affected plants (with slight changes in the color of the core of the stem) can complete the growing season and give a small yield of fruits. The source of the primary infection of stem necrosis is seeds and plant debris. An important role in the spread of the pathogen is played by contact transmission of infection during plant care.

Bacterial spotting (mottling) of tomato fruits

The spread of this bacteriosis, as experts say, is somewhat weaker than the rest. Depending on weather conditions, yield losses from this bacteriosis in the private sector vary widely (5-30%). The disease is most dangerous in early spring plantings - with high humidity and low night temperatures. The disease affects all above-ground plant organs (leaves, stems, petioles, flowers and fruits).

On the leaves, usually small black spots (irregularly rounded) with a yellow edge are noted, sometimes they are located along the edges of the leaf. The center of such spots is raised, has a yellowish-green halo, then it darkens. With the active development of a bacterial infection, these spots merge, as a result of which the leaves curl and die. Similar spots are noted on the petioles, stems and flowers. Especially dangerous is the defeat of the flowers, which then completely dry up and fall off.

Young green fruits are more susceptible to mottling. At the first stage of the disease, small, slightly convex black spots appear on their surface, surrounded by a whitish (as if watery) border, which then gradually grow (up to 6-8 mm), taking the form of ulcers. Over time, the watery border may disappear. The main source of bacteriosis infection is seeds, but the pathogen is able to survive in the soil and rhizosphere of plants.

Top rot of fruit

The cause of its appearance, in the opinion of most experts, may be the causative agent of bacteriosis, or similar symptoms may be caused by the conditions of cultivation of this crop unfavorable for tomato plants. The infection of fruits by this bacterial pathogen during the years of epiphytoties (more often during hot summer) can reach more than 20% in household plots (the earliest fruits are affected). The pathogen affects green fruits mainly in the first 2-3 clusters. At the first stage of the disease, a watery spot (grayish-green or light brown) appears on the floral part of the fetus.

Then the spot darkens and captures a significant part of the fruit. At the same time, its affected tissues are deformed, and the top of the fetus becomes flat, somewhat depressed. Concentricity is clearly visible on this spot. Affected fruits retain a firm consistency, but soften in wet weather, resulting in rot. Affected fruits ripen earlier than healthy ones, sometimes the presence of the disease is recorded only after cutting the fruit.

According to experts, there is a connection between the development of the disease and environmental conditions (bacteriosis develops especially strongly when there is a lack of moisture in the soil and air). Under the same conditions of the air regime, the disease develops more strongly with an excess of nitrogen fertilizers, with a sharp fluctuation in soil moisture. Experts note that there is a non-infectious form of apical rot, in which similar symptoms of fruit damage appear.

According to some authors, they are observed when certain soil and weather conditions coincide; according to others, the main cause of apical rot is a lack of calcium in plant tissues. This pathogen also affects peppers. Some researchers believe that seeds are the main source of the disease, others suggest that at first, due to certain environmental factors, the tissue condition of the fruit is disturbed, and as a result, certain conditions are created for the introduction of the pathogen into plant tissue.

Protection against tomato bacteriosis

Protection against tomato bacteriosis includes a whole range of various agrotechnical measures (this also includes the use of biological and chemical means of protection). These techniques are aimed at creating good cultivation conditions for plants, which makes it possible to enhance their defense reactions to the causative agents of these diseases. On the other hand, these measures also serve to reduce and suppress bacterial and fungal infections and create conditions to limit the prevalence of diseases.

An important part of protective measures is the use of varieties with complex resistance to bacterial and fungal pathogens. They also include pre-plant seed dressing; application of balanced fertilization rates (avoid excessive one-sided application of nitrogen fertilizers); treatment of plants with aqueous solutions of drugs when the first signs of disease appear; control over temperature and humidity in the greenhouse - to reduce air humidity, if necessary, the room is ventilated.

Watering is carried out strictly in the aisles - under the root with a small stream, but at the same time, excessive soil moisture is excluded. It is necessary to regularly remove both severely affected fruits and diseased plants as a whole (together with a twine for a garter); systematic control of weeds and insects, which are reserves of pathogens. Care must be taken when collecting the fruit to avoid mechanical damage. Collecting and harvesting seeds is done only from healthy plants. It is necessary to thoroughly clean the greenhouses and the surrounding area from debris and plant residues after the end of the season, as well as to observe crop rotation with the return of nightshades to the same place no earlier than 3-4 years later. The activities also include a high-quality autumn digging. After all, deeply buried plant remains rot during the winter period.

For prophylactic purposes, immediately before sowing, the seeds are disinfected with thermal wet processing. They are kept in hot water (at a temperature strictly 48 … 50 ° C) for exactly 30 minutes. Such treatment simultaneously stimulates the germination and germination energy of seed material, reduces or suppresses the infectious stock of bacteriosis pathogens. Good results in order to suppress the causative agents of bacterial diseases of tomato are obtained by treating plants during the growing season with a 0.5% solution of Abiga-Peak, VS (up to 3 times). Specialist store sellers can get up-to-date information on new effective fungicides that will also help fight these diseases during the growing season of tomatoes.