Content
Tomato stem necrosis is a disease that can destroy bushes completely or severely inhibit their development. In both cases, the gardener is left without a harvest. It is impossible to get rid of the pathogen and cure plants using modern chemicals; pathogen-resistant varieties and hybrids also do not exist. Therefore, special attention must be paid to prevention and competent agricultural technology.
What kind of disease is this
The official name of the disease is core necrosis of tomato stems. The pathogen causes death of cells and tissues, which leads to irreversible disruption of their functions.
In the vast majority of cases, stem necrosis is observed in tomatoes in a greenhouse, although “outdoor” plants are not immune from it. The disease takes a long time to develop (the incubation period is more than 18 days), the first symptoms appear already at the fruiting stage.
Tomato stem necrosis is caused by a bacterium. The pathogen is transmitted primarily through infected planting material.It is also able to remain viable for quite a long time (up to 4-5 months) in dry plant residues. The bacterium does not live in the soil; it is quickly “suppressed” by other soil microorganisms.
The disease has been known since the late 70s of the twentieth century. It appeared in Russia a little later, in the 90s: it was “promoted” by the active import of planting material from the Netherlands.
In the best case, when the stem is affected by necrosis, the loss of tomato yield is 50-80%. If you use infected planting material, you may not expect fruit at all; the plants will quickly die.
People sometimes call the disease “hollowness”
England is considered the “homeland” of tomato stem necrosis
Symptoms of infection
The first symptom of necrosis is elongated, slightly “pressed” spots and stripes, slightly darker than the main shade of the stem. Gradually they become deeper, turning into cracks, from which a cloudy creamy-whitish viscous liquid oozes, reminiscent of mucus - exudate.
At the same time, the process of “massive” formation of aerial roots begins, gradually “rising” along the stem from the base above and changing the shade from brownish-beige to dirty brown. The stem core of tomatoes affected by necrosis is at first watery-transparent, then cloudy brown. The section clearly shows the black vascular system.
Aerial roots are an obviously unsuccessful attempt by an infected plant to compensate for the lack of water and nutrients.
It is obvious that in diseased bushes the above-ground part does not receive sufficient water and nutrients.Therefore, the leaves of tomatoes affected by stem necrosis quickly turn yellow and wither. They often look as if they have been “scalded” with boiling water.
Since in most cases the active development of the bacterium that causes necrosis of the tomato trunk coincides with the beginning of crop ripening, the tomatoes themselves suffer. A “network” of light yellowish veins appears on the surface of the skin, which does not disappear during the ripening process.
The seed coat of tomatoes affected by stem necrosis is also black and dead
Causes of tomato stem necrosis
In most cases, the primary source of infection of tomatoes with stem necrosis is planting material. The bacterium lives in the shell or embryo of seeds. The “second wave” of the spread of the pathogen is ensured by exudate oozing from the stems of diseased plants, penetrating into any microdamage. Its drops are carried by the wind and fall from infected bushes to healthy ones with water when watering.
The gardener himself can become a “carrier” of tomato stem necrosis. The pathogen gets on garden tools, equipment, gloves and is transferred to healthy plants if their regular disinfection is neglected.
In addition to serious errors in agricultural technology and neglect of preventive measures, there are other “risk factors” that increase the likelihood of tomatoes becoming infected with stem necrosis:
- constantly increased air and soil humidity;
- large differences between day and night temperatures, quite cold nights;
- excess nitrogen in the soil.
It is quite possible for drops of sap from diseased bushes to fall on their “neighbors” in the garden during pruning.
Development of the disease
Once on tomato bushes, the bacterium that causes necrosis “invades” the core of the stem and actively multiplies there, forming entire colonies that are whitish mucus exudate. As a result, all vital processes in cells and tissues, including photosynthesis and metabolism, are disrupted.
Next, there are two main possible scenarios. If a tomato bush is initially “weakened” and does not have good immunity and endurance, it dies. Healthier, stronger and pathogen-resistant specimens survive, and their disease becomes chronic.
Surviving plants practically stop developing and become a source of pathogen spread
Cases of “spontaneous healing” of tomato stems affected by necrosis are much less common. The mechanism of this phenomenon cannot yet be explained. Usually the pathogen spreads along the rows, but in some bushes the characteristic symptoms disappear completely or almost completely 3-4 weeks after their appearance, they continue to grow and bear fruit. However, it is strongly not recommended to use seeds extracted from such tomatoes for planting next season.
Methods for treating tomato stem necrosis
Methods and means to cure tomatoes infected with stem necrosis do not yet exist. The bacterium does not “give in” to agrochemicals, biological products, or folk recipes. They can be used only for prophylaxis to reduce the number of primary infections.
Folk remedies
Gardeners who want to prevent infection of tomatoes with stem necrosis use folk remedies exclusively at the stage of pre-planting seed preparation.During the active growing season, treatments with them will be completely useless.
To “treat” seeds wrapped in gauze or linen napkin, compositions with antiseptic properties are used:
- Aloe juice. The large lower leaf of an adult (over 4-5 years old), absolutely healthy plant is peeled, and the pulp is crushed into a pulp. It is mixed with water in approximately equal proportions. The seeds are kept in liquid for a day.
- Potassium permanganate solution. Crystals are added to the water until it turns bright pink. To prevent necrosis of tomatoes and destroy other pathogenic microflora, planting material is pickled for 5-6 hours.
- Infusion of onion or garlic. Leaves, heads, and cloves are used as “raw materials”. It is crushed, poured with warm water in a ratio of 1:2, left in a warm, dark room under a tightly closed lid for 3-4 days. Before use, filter and dilute with water 1:1. The seeds are soaked in the finished infusion for 2-3 hours.
Potassium permanganate solution is a very popular means for disinfecting any seeds.
Chemicals
Since it is impossible to combat necrosis of the tomato stem, including by using agrochemicals, the bushes are pulled out and destroyed, getting rid of the sources of the spread of bacteria. After this, it is recommended to spill the soil with a fungicide solution for disinfection. Suitable drugs:
- Acrobat MC;
- Quadris;
- Bayleton;
- Ridomil-Gold;
- Abiga Peak;
- Oksikhom;
- Cuprosan;
- Topaz;
- Speed;
- Strobe.
The concentration of the working solution is determined according to the manufacturer's instructions. Approximate consumption 4-5 l/m². The bed is watered from a watering can.
The entire procedure, starting from the moment of preparing the solution, is carried out using personal protective equipment.
Biological products
Biological products are an alternative to folk remedies for pre-planting seed treatment. To destroy bacteria that cause necrosis of tomato stems on the surface of the shell, they are soaked in a solution:
- Maxima;
- Previcura;
- Fitosporina;
- Phytolavina;
- Alirina-B;
- Bactofita;
- Gamaira.
The solution is prepared according to the manufacturer's instructions. It also determines the etching time.
As a rule, a biological product solution does not have even a short shelf life; it must be used immediately
Treatment of stem necrosis in tomato seedlings
Stem necrosis in tomato seedlings is a rare occurrence. Even if the seed embryo itself is infected with the bacterium, it requires a fairly long period to develop and reproduce. During this time, the gardener manages to transfer the seedlings to the garden bed or greenhouse.
From the photos of the plants it is clear that it is difficult to identify stem necrosis in tomato seedlings. Cracks do not appear; the seedlings simply look lethargic. The only way to accurately diagnose it is to cut the stem and look at the pith.
Trying to treat stem necrosis on tomato seedlings is a waste of time. The seedlings are guaranteed to be non-viable. Affected specimens can only be destroyed.
Preventive measures
Prevention is essentially the only thing a gardener can do to really reduce the risk of tomatoes becoming infected with stem necrosis. It includes the following activities:
- Purchasing seeds produced by well-known agricultural companies with a solid reputation that can guarantee the quality of planting material. In addition, the seller must be able to confirm their “originality” by having a certificate of conformity.
- When collecting seeds yourself, you need to carefully select the “donor” bushes and no less carefully cull the planting material before sowing for seedlings.
- Compliance with the planting scheme. It is determined taking into account the dimensions of the adult plant and the type of bush. With “cramped” plantings, the bacterium that causes tomato stem necrosis spreads much faster.
- Disinfection of the substrate and container for planting seeds for seedlings, any tools and garden equipment every time after work.
- Proper care of plantings. Proper watering and fertilizing are especially important for the prevention of tomato stem necrosis.
- “Support” of immunity. During the season, regular (every 2.5-3 weeks) foliar feeding with biostimulants and immunomodulators will be useful to strengthen overall endurance.
- Timely ventilation of the greenhouse to maintain air humidity comfortable for plants.
- Mandatory post-harvest cleaning. All tops and other plant debris are raked from the garden bed and burned. In the greenhouse, it is advisable to disinfect the substrate or replace its top layer.
Without disinfection, there is a high probability that the gardener himself will become a “carrier” of bacteria that causes necrosis of tomato stems
Resistant varieties
There are no varieties and hybrids of tomatoes that are immune to the bacterium that causes stem necrosis.Even if the manufacturer indicates in the description the presence of “relative resistance” to the disease (as, for example, in the hybrids Red Arrow F1, Maeva F1, Resento F1), it is very likely that this is just a publicity stunt.
Based on the experience of gardeners, tomato varieties and hybrids, which are distinguished by their ability to successfully resist negative external influences and generally good immunity, suffer somewhat less frequently from stem necrosis. These include, in particular:
- Vologda F1;
- Ural F1;
- Bohemia F1;
- Koenigsberg;
- Cio-Cio-san;
- Waterfall;
- Geisha;
- Crimson Giant;
- Eagle Heart;
- Monomakh's hat;
- Golden domes;
- De Barao.
Conclusion
Tomato stem necrosis is currently an incurable disease. Neither folk remedies, nor biological products, nor “heavy artillery” in the form of agrochemicals can help infected bushes. There are also no varieties and hybrids of tomatoes that are immune to the bacterium that causes stem necrosis.
