TOMATOES
Introduction
Tomato Production in Kenya
Tomato is one of the most important local vegetable crops in Kenya. It is ranked second to Brassicas (cabbage and kales) in production but first in value. In year 2013, the area under tomato was 23,000 ha and production was 494,000 Metric tons valued at KES 14 billion (HCDA, 2013).
Tomatoes are grown in many agro-ecological zones including semi-arid areas where the crop is grown with supplementary irrigation mainly by smallholder farmers. The major growing areas are Migori, Bungoma, Kajiado, Kericho, Makueni, Kirinyaga, Nakuru, Lamu and Kiambu.
Tomato has become a popular enterprise because of its high yield potential and attractive prices especially during times of scarcity making it a significant contributor to the horticultural subsector (MoA, 2004, GoK, 2007).
Tomato is one of the most highly consumed vegetable in Kenya.It is grown for fresh market, processing and export market.
The information covered here includes:
- Ecological Requirements
- Tomato Varieties
- Husbandry practices
- Pests and nutrients disorders
- Diseases
- Harvesting and Post Harvest Handling
- Marketing, Gross margin and Value addition
1. Planting
Soil Requirement
– Well drained, light loam with high content of organic matter and PH of 5 to 2.5.
Seed rate- 1 to 1.5 kg/ha for direct sowing, 150 to 200 gm/ha for nursery sowing.
2. Nursery Establishment
- Make fine tilth seedbed
- Drill seeds thinly in rows 20cm apart and 1cm deep.
- Keep soil moist but not water logged.
- After germination thin to 7cm apart in a row to ensure strong seedling.
3. Field Establishment
- Space holes 1m by 0.5m to give a population of 20,000 plants/ha.
- Apply manure at the rate of 2 handfuls per hole and mix thoroughly.
- Apply DSP/DAP at 200kg/ha (1 teaspoon per holes) during planting.
- Transplanting is done a month after germination
- Top dress with CAN at the rate of 100kg/ha when plants are 25cm high.
- Top dress again with CAN at 200kg/ha four weeks later.
- Maintain mulch especially for determinate varieties (It keeps the fruits clean, conserves moisture and keeps soil temperatures low).
- Weed regularly (Weeds compete for nutrients and also act as hosts of diseases and pests)
4. Staking and Pruning
Staking
For tall growing indeterminate varieties a 3m stake should be put firmly in the ground for each tomato plant and the stem loosely tied as the plant grows.
Pruning
-Necessary for indeterminate varieties. -Allow one or two main stems to grow, pinch off the lateral shoots weekly. -When 6 to 8 trusses are formed the growing top is pinched off. -Leaves close to the ground should be removed to prevent entry of blight. Irrigation -Irrigate 2 – 3 times a week. during dry weather
5. Physiological Disorders
Nutrients Disorders
- Potassium deficiency results to fruits with poor taste and hollow cavity.
- Phosphorus deficiency will result in stunted growth, delayed maturity and reduced yields.
- Nitrogen excess will result in small fruits and blossom end rot.
- Calcium deficiency will result in blossom end rot.
Blossom End-rot
Early signs of the disorder are a water soaked spot near the blossom end of the fruit.
This turns brown and enlarges to cover almost half of the fruit.
The causes are normally;-
Too fast growth during the early stages followed by sudden drought especially when the fruits are small.
Excessive nitrogen and infrequent watering.
Calcium deficiency especially in young fruits.
Low application of nitrogen to calcium deficiency soils
- Control: –
- Application of CAN
- Apply calcium chloride foliar feed at 15kg/1000 liters (Higher concentration will damage leaves).
- Lime calcium deficient soils.
6. Diseases
1. Late Blight
a. Symptoms
-Occurs under cool and high humidity conditions especially wet season.
-It is characterized by rapid drying of leaves and brownish dry rot of fruits often destroying the whole crop.
b. Control
Spray with Ridomil or Antracol shortly after emergence at intervals of every 4 days in wet weather and fortnightly in dry weather.
2. Early Blight
a. Symptoms
It occurs during hot weather.
It causes stem cankers on seedlings and small irregular dark brown spots on the leaves.
As they enlarge they show a concentric pattern.
The result is partial defoliation of the crop.
It causes premature fruit drop and low quality fruits.
It is soil borne and the fungus usually survives on plant debris.
b. Control
Field sanitation.
Crop rotation.
Foliar sprays as for late blight.
3. Septoria leaf spot
a. Symptoms
Disease occurs at all stages of the plant.
It attacks the solanaceae family and survives on plant debris.
Its development is favoured by wet weather.
It is characterized by the presence of tiny brown black angular leaf spots on leaves.
The sports can cause defoliation which then exposes fruits to sun scald.
In severe attacks, lesions appear on stems and fruit stalks.
b. Control
Spray with Benlate.
Keep field free from weeds.
Remove and burn infected debris.
Crop rotation.
4. Bacterial Canker
a. Symptoms
It is seed borne.
It can reduce yield to 90 percent especially in indeterminate varieties.
The bacteria can survive in cracks on the sticks used for staking.
Symptoms include wilting and curling of the leaflets of the lower leaves.
Dried, whole leaves curls upwards, turn brown wither but remain attached to the stem.
The stem may split open and the pith is often discoloured.
Young fruits show discolouration of vascular system, they show deformation and stunting on mature fruits birds eye spots are visible.
Excess nitrogen favours its development.
b. Control
No chemical control has been found effective.
Planting healthy seedlings.
Crop rotation.
Field sanitation.
Disinfect pruning knife after pruning.
Avoid over fertilizing the crop with nitrogen.
5. Fusarium Wilt
a. Symptoms
Development is favoured by high temperature, low humidity and nutrient deficiency.
It is soil borne and survives in plant debris.
The symptoms include yellowing and wilting of the lower leaves, slightly dropping at high temperatures.
The vascular vessels appear brown.
In cool conditions it affects the root area only causing tomato root rot wilt.
Browning of the vascular vessels is restricted to the stem near the soil level but roots show a severe browning and decay.
b. Control
Use of resistant varieties.
Liming.
Crop rotation.
6. Bacteria Spot
a. Symptoms
The disease is seed born hence infection can start in the nursery.
It is spread by rain splash and sprinkler irrigation.
The disease attacks foliage but is most conspicuous on fruits.
Irregular dark green spots appear on the foliage which eventually dries.
It may cause blossoms to drop.
On fruit the initial spot is very small and water soaked and eventually enlarges.
b. Control
Foliar spray using copper based fungicides.
7. Pests
1. Root Knot Nematodes.
a. Symptoms
These include swellings on the roots causing stunting of the plants and eventual wilting.
b. Control.
Crop rotation.
Plant nematode free seedlings.
Keep field free of weeds.
2. American Bollworms
a. Symptoms
The caterpillar bore into fruit and feed on the inner part of the fruit releasing plenty of excreta which is noticeable on damaged fruits.
The entry point of the caterpillar acts as entry point for bacteria and fungi.
It attacks sweet pepper, tobacco, sorghum.
b. Control.
Spray with Dalathion, Lebaycid at 2 weeks before fruit set and then karate, Decis during and after fruit set.
3. Tobacco White Fly
a. Symptoms
Small white moth-like flies fly from foliage when plants are disturbed.
The nymph sucks sap from underside of the leaves.
They transmit virus.
They cause leaf distortion and stunting if attack is early.
b. Control
Same as American bollworm above but spray thoroughly on the underside.
Other insecticides used include; – Dimethoate, Sumithion or Brigade.
4. Red Spider Mites
a. Symptoms
These are minute spider like animals found on the underside of the leaves.
They cause speckling and tarnishing of the leaves which turn yellowish and whitish.
Severe infestation causes stunted growth, leaves dry up and falls off.
The problem is acute in dry areas or irrigated crops.
b. Control
Brigade at 24ml/20 liter, Dimethoate at 15ml/20 liter, Metasystox at 15ml/20 liter and Kelthane (or as label instructions).
5. Aphids
a. Symptoms
These are plant lice that suck sap from leaves causing leaf distortion especially during dry spells. Aphids prefer young leaves, stems or flowers.
Their secretion causes sooty mould.
They transmit viral diseases.
b. Control.
Spray with dimethoate 40 percent c.c. at 15ml/20 liter water, or Fenitrothion 50 percent E.C at 15ml/20 litre of water.
Common Soil Borne Pest in Tomatoes
Pests and diseases are amongst the major constraints in tomato production, particularly the soil- borne pathogens that are capable of surviving in the soil for long durations. Soil is a reservoir for many plant pathogens and when conditions become favorable; the plants become infected by the pathogens and develop disease.
These soil borne pathogens may cause diseases such as, bacterial wilt, Fusarium wilt and damping off disease. Bacterial and fusarium wilts (plate 1.2.1& 1.2.2) are responsible for severe losses of up to 75 -100 percent leading to high economic losses in tomatoes and potatoes.
Damping-off disease, which is caused by several soil borne pathogens, is capable of wiping out the entire tomato crop at the nursery level (plate 1.2.3 & amp; 1.2.4).Tomatoes are also affected by other pests found in the soil and especially the root knot nematode (Figure 1) while weeds compete with the crop for available nutrients and water leading to high economic losses.
There is need to address the management of soil borne pests (diseases, pests such as nematodes and weeds) to reduce losses thus enhancing tomato quality and yields with overall objective of increasing farm incomes .
Currently, many farmers rely on chemical pesticides as a method of protecting crops against soil-borne pathogens. However, use of chemical pesticides may not be desirable due to the potential risk to the environment as well as human and animal health and therefore should be used as a last resort. As a result of these risks, increased restrictions have been imposed on a variety of chemical pesticides in Kenya for example use of Methyl Bromide as a soil fumigant.
Alternatives to use of pesticides for management of soil borne pathogens are available, for example use of Integrated Pest Management (IPM) approaches. Some of the promising alternatives or IPM approaches for the management of soil borne pathogens include soil solarization, soil heat treatment and fumigation.
8. Harvesting
Harvest tomatoes by picking the fruits that have changed or are starting to change colour.
9. Variety Characteristics
| Variety | Fruit wt (gm) | Days to Maturity | Yield Tons/Ha | Disease Resistance |
| Money maker | 75 | 67 | 32-50 | Susceptible |
| Marglobe | 188 | 70 | 38 | – do – |
| Beauty | 80 | 70 | 20 | – do – |
| Roma UF | 53 | 120 | 83 | Resistant to Fasarium wilt |
| Cal J | 68 | 120 | 73 | Susceptible |
| M – 82 | 53 | 120 | 57 | – do – |
| Riogronde | 74 | 128 | 84 | – do – |
| * Rubino | – | 110 | 84 | – do – |
| *Parmamech | – | 110 | 75 | Susceptible |
| *Parma VF | – | 110 | 79 | – do – |
| *Nema 140 L | 85 | 118 | 39 | Resistant to nematodes |
| *Picardor | – | 110 | 41 | Susceptible |
| *Spectrum | 81 | 110 | 38 | – do – |
| *G 527 | 45 | 120 | 37 | Resistant to Fusarium wilt and nematodes |
| *Nema 1400 | 90 | 117 | 37 | Resistant to nematodes |
| *Nema 1200 | 82 | 109 | 34 | – do – |
| *Capitan | 100 | 74 | 67 | Resistant to some stains of bacterial wilt. |
| *Tropic | 230 | 74 | 58 | |
| *Kentom 1 | 100 | 65 | 65 | Resistant to nematodes |
| *Kentom 2 | 120 | 70 | 65 | Resistant to nematodes and bacteria wilt. |
Other sources of information/References
- For market information contact: Ministry of Agriculture – Marketing Division; KACE.
- For detailed gross margin and profitability contact: Ministry of Agriculture – Agribusiness Division.
- On recommended chemicals contact: Pest Control and Produce Board, Agrochemical Association of Kenya and Registered Agrovets.
- On soil analysis contact: Kenya Soil Survey – KARI