Mana, fusariosis, brown spot, alternariosis — these are just some of the infections that can attack your tomato crop. Here’s what you need to know about the main diseases that affect tomatoes and how you can prevent and combat them.
Tomatoes are found today in over 4000 varieties worldwide and are among the most cultivated and consumed garden products in Romania. From the plantations of the big producers to the small household greenhouses, all of them are affected, to a certain extent, by specific diseases, which can compromise the entire culture of a season.
Few unpleasant situations compare with the frustration felt at the loss of the harvest, especially when it comes to small producers, who live from the sale of tomatoes, peppers, eggplants, etc. Diseases that affect tomatoes can be prevented, and losses, reduced, if acted correctly and in time. Find out in this article how to quickly recognize risky situations and what you can do to heal the culture.
Hand to tomatoes
Mana is one of the most common and serious diseases in tomatoes and is caused by a microscopic fungus called Phytophthora infestans. You recognize it by the appearance and color of the spots that appear on all the organs of the plant:
– Circular / irregular spots, with moist appearance, green-yellow, positioned on the edge and on the top of the leaves, so that later they change their color towards brown-gray and get a whitish down on the dorsal side, if there is moisture in the air;
– Oval spots, small, brown-gray, positioned on the stems, which grow up to 10–20 cm, surrounding the plant and causing the stem to rot and the seedlings to fall;
– Olive-green spots, irregular, appearing at the site of the pendulum penetrating the fruit. They change color to purple-brown and expand, eventually leading to fruit fall by rotting the stalk;
Its appearance is favored by the cold environment (it grows well between 15 and 18 o C) and humidity:
– air humidity higher than 80%;
– drops of water left on the leaves, from watering the tomatoes with sprinklers;
– condensation that occurs in unheated greenhouses, due to the day / night temperature difference.
Prevention and control
Because the hand is transmitted from one year to another through infected potato tubers and contaminated tomatoes fallen and left on the ground, one of the best measures to prevent is crop rotation. Another is to avoid growing tomatoes near the potato layers and in no case in the same greenhouse.
– Watering the tomatoes in the solarium by drip or gutter system to avoid the formation of drops on the leaves;
– Use of healthy, disinfected seeds;
– In solariums to maintain a constant temperature of over 20 o C;
– If the crop has been infested, the affected leaves and fruits are harvested and destroyed.
To control manna in tomatoes, you can opt for either an organic treatment with milk solution, about which you can find detailed information on the Internet, or a synthetic alternative with special fungicides, selected according to the stage of development of the plant (Alcupral, Bouille Bordelaise , Bravo, Captan, Captadin etc.). Check for each solution when sprinkling the tomatoes and at what period after sprinkling you can pick the fruit.
Produced by Fusarium oxysporum, this disease affects 50% of crops in greenhouses and solariums each year, attacking both tomatoes and peppers, eggplants and potatoes. The fungus acts in all periods of vegetation, but you will best notice the symptoms when the fruits begin to ripen.
It can appear at first only on one or two branches and is manifested by the withering of the leaves and later, the falling of the leaves. It attacks the conducting vessels, affecting the feeding with water and nutrients and leading to the slowing down of the plant’s growth and then its drying. It is one of the diseases of tomatoes that is present more in solariums than outdoors.
The factors that favor the appearance and development of this fungus are:
– High soil moisture
– Soil with acidic pH
– Temperatures of 27–28 o C
– Excessive fertilization of the soil with nitrogen
Prevention and control
Unfortunately, in this case the crop rotation does not help much, because the fungus lasts in the soil for up to 4–5 years. In order to limit the spread on the field, it is recommended:
– Avoid work when the soil is wet, because the fungus can be taken on shoes;
– Plucking and destruction of diseased plants;
– Elimination of weeds that may be hosts for this disease: stir, mallow, cranberry;
– Sterilization of the poles used to support the tomatoes;
A very good method of preventing this disease is the selection and sowing of hybrid varieties, specially designed not to be affected by hand, symbolized by VF on the package.
For control, of course, treatments can be made on tomatoes, with fungal solutions, the best known being those from the Topsin range (Topsin 500 SC, Topsin 70 WDG, etc.).
Gray rot in tomatoes
Gray rot is caused by the fungus Botrytis cinerea and is manifested mainly on the fruit, but also includes the leaves. You recognize him by:
– Brown, elongated spots, covered with white-gray down on the leaves
– Gray, watery spots on the stem and softening of the fruit at the top
It affects both tomatoes and peppers, cabbage, eggplant, salad, etc. It is good to know that in this case, if the stained part is removed, the fruit can still be eaten. However, the disease affects the commercial value of the crop.
Favoring factors of gray rot
Like many tomato diseases, gray rot develops best in areas where:
– Humidity exceeds 80%
– Ventilation is not efficient
– The brightness is low
– The temperature is between 22 and 24 o C
– Excessive fertilizers are used
Prevention and control of gray rot
You can prevent this disease by ensuring good ventilation inside the greenhouse and avoiding excessive watering. It is also good to remember that care operations such as infancy, leaflessness or carnivore leave the plant injured and vulnerable and must be performed carefully.
Alternariosis in tomatoes or brown leaf spot
It is produced by the fungus Alternaria solani and attacks all the organs of the plant, manifesting itself from the seedling phase, on the lower leaves, on which brown-gray spots appear. You will be able to differentiate these spots from others caused by tomato diseases, due to the concentric rings that form on their surface, together with a fine, blackish felt. On fruits, the spots are slightly submerged and expand over time, covering the entire surface.
It is one of the diseases that manifests itself very aggressively in greenhouses and solariums and is quite difficult to fight.
Favoring factors for alternariosis
These fungi grow very well at temperatures of 25 to 30 o C, in the presence of water droplets on the leaves, stem and fruits, in conditions of high humidity in the environment. Among the favoring factors are also:
– Magnesium deficiency in the soil
– The presence of weeds
Preventing and combating alternariosis
To prevent the development of this fungus in greenhouses and solariums, a series of measures are needed, such as:
– chemical and thermal disinfection of the soil
– drip irrigation, preferably in the morning
– destruction by burning, in autumn, of the infested vegetal remains
– crop rotation — avoid cultivating eggplants, tomatoes and potatoes for 3 years on soil infested with this fungus
– seed disinfection
– use of fungicidal treatments — if you are wondering what to spray tomatoes against alternariosis, we will tell you that there are many solutions you can use for treatments on tomatoes, in the solarium, based on cimonaxil and famoxadon, azoxystrobin, tebuconazole, etc.
Brown spot on tomatoes
Because leaf spot, in tomatoes, is the main symptom of the presence of a disease, it should immediately make you think. Brown staining can lead to losses of up to 25% in tomato crops and is easily recognized by the fact that it manifests itself mainly on old leaves and less on the stem or fresh fruit.
In addition, the yellow spots, which later become reddish-brown, are covered on the back of the leaf with a brown down. The attacked plants grow harder, and the fruits ripen early and have a bad taste.
If you grow tomatoes in the solarium , it is good to know that this is one of the diseases of tomatoes that affects more plants grown in a controlled environment than those grown outdoors.
The brown stain is installed comfortably and develops very well in the following conditions:
– Temperature between 20 and 24 o C
– Humidity of 85–100%
– Lack of air currents (heavy rains and wind prevent development)
Prevention and control
In order to prevent the appearance and development of the pathogen, it is essential to meticulously destroy, by burning, the affected plant residues, thus avoiding the transmission in the following year.
In the solarium, the best recipe is efficient ventilation, either by automatic ventilation system or by raising the sides, to create air currents.
You can apply chemical treatments both preventively, especially if you have already faced brown spot last year, or for control, as soon as the first signs of infection of the crop.
Twisting the leaves on tomatoes
Although it is rarely caused by infestation with a parasite or one of the many diseases of tomatoes, leaf twisting is still a warning sign, which shows that the plant suffers, and untreated, can lead to crop loss. Leaf twisting can be caused by:
– Strong wind — uses shade nets or forest forests for protection;
– Moisture deficiency (leaves twist upwards, inwards) — a tomato bush needs 5–10 liters of water once every 5 days;
– Excess moisture (the leaves twist downwards, outwards) — the bushes in the greenhouse do not get wet for a week;
– Excessive heat — places shading nets;
– Excessive nitrogen fertilization (leaves twist inwards, stems thicken) — stops the addition of nitrogen;
– Childhood or defoliation of tomatoes, if they were not done correctly — fertilize with potassium and phosphorus (infusion of ash, superphosphate);
– Attack of aphids (twisted leaves with yellow spots) — apply insecticide, consulting the treatment scheme for tomatoes and taking into account the stage of plant development;
– BCTV virus — causes dandruff of plants, leaves twisted up, yellowed, flowers abort. It can be an answer to the question “why do flowers fall on tomatoes” and attack aggressively enough but offer little chance to save the plant. There is no treatment, the plants must be uprooted and destroyed.
Why do tomatoes crack
In the absence of other symptoms that lead to tomato disease, many growers do not know exactly how to react when the tomatoes on the stalks begin to crack. Fortunately, the cracking of tomatoes is mainly due to water intake.
In short, if the crop has received less water for a while and then has access to a much larger amount, the tomatoes will develop suddenly, and the peel will not be able to cope with the growth, cracking. The cracks that form are of two types:
– Circular — superficial, not a cause for concern
– Longitudinal — deeper, make the fruit vulnerable to a variety of diseases and pests of tomatoes
The solution is quite simple and consists in establishing a watering program to prevent too large quantitative fluctuations.
Tomato treatment program
To prevent the appearance of diseases, it is good to get acquainted with the recommended tomato treatment program. You can grow red without problems in the solarium, with treatments applied in time and correctly, depending on the stage of plant development.
If you do not know when to spray the tomatoes for the first time we will tell you that you can do this even before planting the seedlings, 1–2 days, to combat pests such as whitefly, California thrips, etc.
Immediately after the stabilization of the seedlings in the permanent soil, which usually means 7–10 days after transplanting, the second treatment follows. Sprinkling tomato seedlings at that time aims to prevent alternariosis.
The following treatments are generally applied at intervals of 1–3 weeks, closely related to the frequency and extent of precipitation, which will especially favor the appearance of manna.
In order for these treatments to give you good results and to keep you from withering the top of tomatoes, falling leaves and fruits and other problems with the harvest, it is good to remember a few basic rules:
– The treatments are generally applied in the evening, when outside they are less than 25 o C
– It is important to correctly identify the parasite or disease that affects the plant, so as not to use the wrong substance
– Pay special attention to the indications for using the treatments if you are put in the situation of spraying during the flowering period
Don’t forget the rest of the agricultural activities and be careful how you approach each step. For example, mulching tomatoes can cause pests or diseases if you do not choose the material you use carefully and do not make sure that it is disinfected.