The black bottom of the tomato, recognizable by the dark spots always appearing on the part of the fruit opposite the peduncle, indicates a calcium deficiency. This phenomenon called apical necrosis is not a disease and tomatoes can be eaten if they are very slightly affected, provided that the affected part is removed. There is no no treatment against apical necrosis but we can indeed prevent. Let’s do a check in.
Tip necrosis or black bottom of tomatoes: causes
The black ass of the tomato isphysiological origin. It’s the water stress which is mainly the cause, either because the plants are watered with too cold water, or because the waterings are too irregular, or even because the soil is leached by an excess of water. Too high a rate of ammonium nitrate or nitrogenous fertilizer can also interfere with the absorption of calcium by tomatoes. Note also that soil salinity promotes apical necrosis.
Black ass of the tomato: prevention
Once you have some idea of the main causes of apical necrosis, it is quite easy to avoid this phenomenon. The tomato black ass prevention inevitably involves avoiding water stress. This implies respecting the following points:
- Install a mulch at the foot of the tomato plants to prevent the soil from drying out since the mulch slows down the evaporation process. But be careful: we only mulch the tomatoes after rain or watering but never on dry soil, and we preferably use a organic mulch so that it quickly turns into nutritious humus, which is the case with grass clippings. If these are perfectly dry at the time of spreading, a thickness of 10 cm is necessary, but we limit ourselves to 5 or 6 cm if the grass clippings still contain moisture.
- Never wet the leaves when watering, but sprinkle all around the feet.
- Water regularly to avoid alternating periods of drought and excess humidity.
- Make arrangements if you plan to be away. Upturned water bottles are installed to make up for the lack of watering for a short week, but for a longer period, it is necessary to use a specific watering system such as the drip or one more microporous pipe in order to water directly at the foot. It is very important to have a programmer.
In parallel with this fight against water stress, to prevent black bottom in tomatoes, it is absolutely essential to provide enough calcium to your plants. Must therefore :
- Place oyster shells and/or eggshells at the bottom of each planting hole after crushing them.
- Allow the young transplanted plants to develop enough roots so that the tomatoes can be well supplied with water.
- Spread wood ashes in small quantities (after having diluted them in water) at the foot of the tomato plantations in order to rebalance the ground.
- Do not overuse the soil.
- Opt for a foliar fertilizer of seaweed juice or liquid manure (from horsetail, fern or nettle) or buy a special tomato fertilizer of very good quality.
- Remove excess young tomatoes.
When the apical necrosis reaches the tomatoes in depth, the flesh being affected, the fruits end up being unfit for consumption. At the slightest sign, do not hesitate to eliminate all the affected fruits.
Finally, when buying tomato plants, it is better to avoid varieties more easily prone to tomato black ass, such as San Marzano, Cornue des Andes or Roma. But you should still be aware that all varieties of tomatoes, even the most resistant, can be affected by this problem if you do not adopt the good cultivation principles allowing to prevent apical necrosis. All precautions must be taken from planting and throughout the development of the fruits so that the calcium can be perfectly absorbed by the plants and benefit the tomatoes.