Tomato is one of the most important vegetables grown in Kenya. It is a half-hardy, annual sub-tropical fruit vegetable used in salads or cooked as a vegetable, processed into tomato paste, sauce and puree. It is rich in vitamins.
Climatic conditions
It is fairly adaptable and grows well in warm conditions and optimum temperature of 20- 25oC during the day and 15-17oC at night. High humidity and temperature reduces fruit size and yields while low temperature leads to delayed colour formation and ripening. Wet conditions increases the disease attack and fruit fail to ripen.
Varieties
Rio grande and Cal-J are good open pollinated varieties, and there are also many good hybrids like Centenario F1 and Moleria with better qualities as shelf life and colour.
Seed rate
About 200 – 250gm/Ha or 100g per acre of pure germinating seed for nursery, sowing is required. Drenching of the nursery against soil pathogens with products such as Bioactiv and Plant guard, ensures a robust seedling for quick take off (growth and development)
Field Establishment
Plants can be grown on raised beds or flat land. The recommended spacing is 60cm by 45cm or 90cm by 60cm depending on variety.
Manure and fertiliser application
Manure is required if soils are poor in organic matter. It should be applied at the rate of 2 handfuls per planting hole and mixed thoroughly with the soil during transplanting. 200 Kg/Ha double super phosphate should also be applied at transplanting and mixed well with the soil. Top dressing with CAN at 100 Kg/Ha should be done when plants are 25cm high. A second application of CAN of 200Kg/Ha four weeks later is beneficial. Nitrogen deficiency will result in small fruits and blossom end rot disease. Application of foliar fertilizers such as Vitabor Gold ensures induction and production of quality flowers with no abortion both of the flower and young fruits. Ferrari Foliar fertiliser when applied at fruiting stage ensures production of big quality fruits with good colour and shelf life.
Before planting tomatoes, the following factors should be considered:-
Location for planting:- Water proximity should be as close as possible to the planting field to avoid added costs of pumping water. Although water tanks can be used and this is specifically suitable when using drip irrigation system.
The previous crop planted:- Tomatoes should not be planted immediately
after potatoes or pepper and a 3 month break should be observed. This is to minimize on risk of diseases and reduce costs on disease management.
Topology:- Gently sloping land is best as it facilitates drainage during rainy periods especially for open air method.
Soil:- The soil should be deep well drained loam. The soil should be prepared well and loosened and broken down well. The optimal pH for tomatoes is around 6-7.5. Soil analysis can be done to determine this and help you come up with the list of required fertilizer to prepare the land. If the pH is low, lime can be used to raise it and if high, gypsum can be used to lower it.
DISEASES, PHYSIOLOGICAL DISORDERS AND PESTS
Late blight (Phytopthora infestans)
Occurs under cool and high humidity especially wet conditions. It is characterised by rapid drying of leaves and brown dry rot of fruit. Brown streaks are observed on the stem. Control: Spray with Cadilac 80% WP (40 Gm / 20L water)or Tower 72% WP. Tower is both preventive and curative at 50gm /20Lt., while Cadilac is preventive.
Early blight (Alternaria solani) In tomatoes, it causes stem cankers on seedlings and small irregular dark brown spots on the older leaves leading in partial defoliation of the crop. The fungus survives on the crop debris. Infections begin as small brown spots on older leaves that quickly enlarge. The lesions develop a “bulls-eye” pattern of concentric rings that can be seen.
Control: Field sanitation, crop rotation and foliar spray as in late blight above.
Bacterial cankers (Clavibacter michiganensis)
This is a seed borne disease whose symptoms are not apparent until the disease is well established. Reduces crop by 90 per cent. Symptoms include wilting and curling of the leaflets of the lower leaves. Dried, whole leaf curls upwards, turns brown and withers but still remains attached to the stem. If affected, young fruits show slight discoloration of the vascular system, deformation and stunting of fruit and seed abortion.
Fusarium wilt, bacterial spot control
Use of resistant varieties and soil fumigation with copper based fungicides. Manage soil fertility to activate antagonistic microbes with Bioaktiv & Humigreen.
Bacterial wilt (Pseudomonas solanacearum)
The disease causes wilting of tomatoes and potatoes. In tomatoes it is mainly seed borne.
Control: Control is mainly cultural as: Strict crop rotation, removal and burning of infected plant debris and planting of certified seed.
Damping off Control: Proper spacing in the nursery. 30cm between rows avoids too much crowding between one plant to another. -Drench the nursery with Bioactive, Tower 72 per cent WP or Megaprode lock Proper watering in the nursery avoids water logging. Ensure watering is done in the morning and not late afternoon to avoid wetting at night.
Disorders Blossom end rot:
This is not a pathological disease, but is mainly physiological. It is caused by calcium deficiency. The early sign of the disease is a water soaked spot near the blossom end of the fruit. The surface of the spot becomes dark and leathery but no soft rot develops unless bacteria or fungi invade the spot. Other causes are: Too fast growth during the early stages followed by sudden drought, excessive nitrogen and infrequent irrigation.
Control: Apply Ferrari Gold foliar fertiliser fortnightly and if plant is stressed use Optimiser to help in recovery.
Pests Root knot nematodes
These are galls and swellings on the roots causing stunting of the plants and eventual death.
Control: Good agricultural practices and chemical controls are used. Planting nematode free seedlings through application of Nematicides. Fertilisers such as plant guard help through facilitating production of beneficial microbes and in production of new root hairs to substitute the damaged or infected ones.
Tobacco white fly
These are small, white, moth-like flies, which fly from foliage when plants are disturbed. Nymphs suck plants sap from the underside of the leaf. They transmit plant viruses as cowpeas mild mottle viruses (CMMV), cassava mosaic among others.
Control: Easily controlled by the chemicals as Sinophate 75 per cent SP and Presento 200SP.
Mites Red spider mites
The minute, spider like animals are visible to the naked eye and feed on sap from the underside of the leaves. They cause speckling and tarnishing of the leaves turning yellowish to whitish. The pest has a wide host range including wild plants such as sodom apple and cultivated plants such as cassava and maize.
Control: Controlled by foliar spraying with Escort 19EC
Others include; leaf hoppers and aphids Thrips and cutworms.
Control – spray with Ranger 480EC
American boll worm (Heliothes armigera).
The caterpillars bore into fruit and feed on the inner of the fruit releasing plenty of excreta which is noticeable.
Control: Spray with Legacy/ Heritage 5%EC (12Ml / 20 Lt water) or Emerald 200SL or Pentagon 5%EC or Escort 19EC (8- 10ml / 20Lt) during and fruit setting.
* Agrolution via http://smartfarmerkenya.com/tomato-production/
INNOVATING AGRIBUSINESS 