On the first tomatoes of the season and after an extremely dry period in summer, a sort of dry and sunken decay develops on the blossom end of the tomatoes. This disorder is termed as blossom end rot or fruit rot found widely in tomatoes. The rot first appears as water-soaked spots on the bottom (also known as blossom) end of the tomato. The affected tissue thus breaks down rapidly and the whole surrounding area becomes sunken, dark brown or black and leathery. This can happen to the tomatoes at any stage of maturity of the tomatoes but are especially found in the first tomatoes of the season.
Cause of the disease.
The cause of fruit rot in tomatoes is the presence of insufficient amounts of calcium in the blossom end tissues of tomatoes. Like other plants, tomato plants also absorb calcium and other nutrients by means of roots. But, calcium becomes immobile and thus settles into parts of the plant other than growing fruits. As a result, the rot can still occur even when there is an ample supply of calcium in the soil, stems or leaves. Actively dividing meristematic tissues present in the young fruits of the plants require a continuous supply of calcium to prevent the spots from developing.
Conditions responsible for the disease.
Since this is not a disease triggered by pathogens, so there are quite a number of external conditions responsible for the fruit rot in tomatoes. The conditions include –
1. Presence of inconsistent soil moisture throughout the growing season.
2. Onset of drought.
Both the conditions are related to a deficiency of water because calcium is only transported into the plants with an ample moisture supply. The fruit will continue to develop even in absence of water but the deficiency of calcium would result in fruit rot.
3. Root damage can also result in hampering the process of absorbing nutrients and moisture as well. Overuse of fertilizers, insufficient plant spacing and waterlogged soils can result in damage of roots.
4. Field or garden soils where the tomatoes are growing may also have low levels of calcium.
Symptoms of fruit rot in tomatoes
The symptoms of this physiological disorder are quite visible and prominent. The classic symptoms of the disorder include -
- A water-soaked spot at the blossom end of the tomato fruit.
- The water-soaked areas enlarge and turn dark brown and leathery.
- The black spots slowly develop to rots and thus the whole fruit becomes unsuitable for consumption.
- The appearance of black or brown lesions on the surface of ripe and over-ripe fruits.
Stages of growth susceptible to infection.
The fruit rot in tomatoes can appear especially in the highly active fruiting stage when the young fruits are affected by deficiency of calcium.
Damages caused by fruit rot.
Fruit rot in tomatoes is one of the most deadly and fearful disorders that cause irreparable damage for the farmers. When the fruits are affected, the yield becomes highly limited and thus the income generated for the farmers decreases drastically. Also, the spreading capability of this disorder is very high which results in difficulty in controlling the spread of it once it is initiated. One by one all the fruits of a plant get affected and if the soil has calcium deficiency, the whole yield from that field gets destroyed.
Prevention & Control.
The disorder is highly problematic, but it can be prevented by means of certain steps such as –
1. Proper testing of the soil before cultivation
Nowadays with the gradual advancement of science, there are a number of methods available at low costs for testing the nutrient status of the soil. After that, fertilizers and lime should be used as recommended by the soil test. Fertilizers which are low in nitrogen but high in superphosphate with proportions similar to 4-12-4 or 5-20-5. This will greatly reduce the chances of blossom-end rot.
2. Cultural practices
Deep cultivation around the plants should be avoided especially in the dry weather. Growth of weeds should be controlled by mechanical means such as hoeing or harrowing in specific intervals which will prevent the weeds from draining nutrients from the soil.
3. Irrigation and soil moisture
One of the very important aspects for prevention of fruit rot in tomatoes is to maintain appropriate soil moisture, especially during the growing season of the plants. At least 1 inch of water should be provided to the tomato field by means of rainfall or irrigation. This will help in proper mobility of calcium from roots to the fruits.
4. Use of Mulch –
Appropriate use of plastic or organic mulch helps to conserve the soil moisture in the tomato fields. However, organic mulches should be used keeping in mind the goals of sustainable development for a green future.
5. Proper maintenance of the plants –
The infected fruits should be removed immediately after spotting. Since this is not a disease caused by any pathogens, it does not spread from plant to plant or from fruit to fruit, so the appearance of fruit rot in the earliest of fruits does not necessarily mean that they will occur in the later fruits too. Using fungicides or pesticides are useless for treating this disorder.