Salvaging Tomato Production in Kenya from the Menace of Pest and Diseases. The case of– Tuta Absoluta and Fusarium wilt root-knot nematode complex.

Why tomato?
Tomato is one of the most important vegetables grown in Kenya. It plays a critical role in income generation and creation of employment for both rural and urban populations, in addition to meeting food nutritional requirements. Tomato is a nutritious vegetable that provides good quantities of vitamins A and C.

Tomatoes are used in many cooking recipes or as a fresh item in combination with salads. Tomatoes are grown for the domestic market under both rain-fed and irrigated conditions. Due to the high demand for tomato, farmers have extensively adopted high yielding varieties and modern technologies like greenhouse production to ensure year round increased production. Commercial farming of this important crop is however under immense threat from pests and disease, mainly Fusarium wilt, Nematode complex and the Tuta absoluta (tomato leafminer). Some farmers have reported yield losses of up-to 80-100 % per growing season.


Tuta absoluta
Tuta absoluta commonly known as the tomato leaf-miner, is a very harmful leaf mining moth with a strong preference for tomatoes. Measuring a mere 7mm, this invasive pest is considered a serious threat to tomato production worldwide. It also occurs on eggplants, sweet peppers as well as potatoes and various other cultivated plants. Tuta absoluta can cause 50-100% yield reduction on tomato crops and its presence may also limit the export of the product to several destinations. Prevention and proper management of the pest is crucial. Chemical control often fails due to the resistance of the pest against many pesticides, but also because a big part of its development takes place inside the plant or the soil, out of reach of pesticides.

Fusarium wilt
Fusarium wilt is one of the major diseases of tomato in Kenya. Fusarium wilt in tomatoes is caused by a fungus which is soil borne and can survive indefinitely without any host. Most occurrences are associated with infected tomato debris left in the soil. An infected tomato will begin yellowing on the bottom leaves. The yellowing will begin on one side of the leaf, shoot, or branch and then slowly spread out and up the vine. The vines will brown along the veins and eventually wilt permanently, resulting in a stunted plant. If the plant does not die, it will be weak and produce low quality tomatoes. Fusarium wilt can survive for years in the soil and is spread by water, insects and garden equipment. It develops during hot weather and is most destructive when soil temperatures approach 27˚C. Dry weather and low soil moisture encourage this plant disease. In spite of the high tomato losses associated with Fusarium wilt its control is limited to use of fungicides which are unaffordable by the many poor resource Kenyan farmers. There is therefore need to seek alternative control measures that can be attractive to a poor resource farmer.

Root-knot nematodes
In Kenya root-knot nematodes are widely spread in all tomato growing areas and hence are a major concern to both smallholder farmers and commercial producers. Losses in yields range from 28% to 68%.The small-scale farmers fail to recognize nematodes because they are found in the soil and their above ground symptoms can be mistaken for nutrient deficiencies and climatic changes especially drought.

Root knot nematodes survive by feeding directly off nutrients pumped through tomato roots. They form galls that can reach up to an inch wide where they hide and reproduce, causing a number of symptoms on the plant. Yellowing plants, stunted growth and general decline are early symptoms of the disease. Their microscopic size make it difficult to identify them and farmers are required to dig up the crop to check on the presence of root-knots which is not a common practice. Prevention against nematodes is difficult because nematodes cannot be eradicated completely from the field.

‘‘As new trends emerge, Kenyan farmers in the future will have to innovate continuously in order to remain competitive; the farmers will need to respond to the permanent pressure on margins, professionalism, increase demand and face growers in abroad countries with excellent farming techniques’’

It is against this backdrop that Koppert Biological Systems Kenya partnered with Kenyatta University and Koppert BV Netherlands in a Food & Business Applied Research Fund (ARF) project meant to tackle the two greatest threats to tomato farming -Tuta absoluta and Fusarium wilt-Nematode complex. This is in a bid to salvage an industry that rakes in approximately KES 14 billion annually. The project involved farmers in Mwea area of Kirinyaga County, one of Kenya’s leading tomato production regions among other tomato growing areas. Additionally, the project also enhanced and facilitated knowledge exchange and dissemination whilst building the capacity of farmers, agricultural extension officers and other stakeholders.

Pesticide use not sustainable
What many farmers came to know is that pests like Tuta absoluta, which have a short generation time and high reproductive potential, are at an increased risk of developing resistance to insecticide use. To avoid a similar predicament, a shift in current pest management practices in Kenya is necessary. An Integrated Pest Management (IPM) strategy that employs a holistic integrated approach is likely to enhance the control of T. absoluta and other pests.

IPM is an ongoing, dynamic system that requires regular review and adjustments of pest control methods for optimal results. The Koppert-Kenyatta University project provide tomato farmers with potent & environmentally friendly pest control solutions and validate the use of IPM strategies to control Tuta absoluta, Fusarium wilt and Nematodes complex in Tomatoes.

The role of biological control
At the heart of this campaign are three superior solutions touted as key in tackling the twin tomato problems. The first one is Trianum-P, a biological fungicide that protects plants against various soil borne pathogens like Fusarium, Pythium, Rhizoctonia and Sclerotinia. Trianum-P also increases plants’ uptake of nutrients by promoting development of a healthier root system and increasing availability of macro and micronutrients.

Secondly, is the NatuGro system, a comprehensive approach which consists of a mix of beneficial biological microorganisms, plant-specific substances supplemented with professional advice. NatuGro helps plants develop more resistance to attacks; soil borne diseases are tamed while nematodes are managed effectively through enhanced root development eventually increasing yields.

Finally, Pherodis Tuta absoluta (sex-specific pheromone) in combination with Deltatraps and Tutasan watertraps on the other hand are crucial in monitoring and mass trapping of the adult Tuta absoluta male moths. This strategy helps in early detection of the pest and curbs the multiplication before they cause any serious damage. This biological cocktail combined with judicious use of chemical pesticides promises a formidable force in taming out these troublesome diseases and pest.

Mistakes to avoid
Not Hardening Seedlings
Hardening your seedlings is one of the most important things you can do to help ensure their survival. Without hardening, your seedlings won’t be able to adapt to the change in temperature or the exposure to weather, like wind and rain.

Planting Too Closely
Planting your tomatoes too closely not only stunts their growth and causes a drop in fruit production, but it also makes it too difficult for sun to reach through the plants. This means your tomato plant suddenly becomes the perfect breeding ground for plant diseases that love the damp conditions.

Tomatoes grown upright in cages need at least 1 ½ feet between them, though 2 feet is ideal. Sprawling tomatoes will require twice the amount of space. While it’s not a big deal to leave your plants slightly unsupported, you never want the plant to be touching the ground.

Planting the Wrong Tomatoes
Now that we’ve covered spacing requirements, the next step is choosing the right type of tomatoes for the amount of room you have. There are two main categories of tomato plants; determinate or indeterminate. Planting in the Shade Like other plants that produce fruit, tomatoes need at least 7 hours of sun per day. Placing them in a shady area deprives the plant of the amount of sun it needs, and it will impact how your plant grows.

Fruit production requires a tremendous amount of energy. Like all plants, tomatoes get this energy from the sun.

Not Pruning
If you have more space and opted for indeterminate tomatoes, part of your plant maintenance will be pruning. Reasons for pruning include:


  • Since overcrowding makes it easier for plant diseases to spread, neglecting to prune indeterminate plants can be detrimental.
  • The foliage on crowded plants will dry more slowly which encourages a variety of plant problems.
  • Plants need to be pruned so nutrients are being directed to fruit growth rather than to new leaf growth. Not only will plants produce smaller tomatoes at a slower rate if they aren’t pruned, but the overgrowth can also provide the perfect environment for plant diseases.


If your plants are looking diseased, sterilize your shears after use to avoid spreading the disease to healthy plants.

Not Ready For Early Blight
Early blight can leave your plants completely bare of foliage, and if you’re not prepared to treat it, this problem can quickly spiral out of control. Early blight is caused by a fungus that can overwinter in soil, so if you’ve had plants with this problem before, you should avoid planting in that area.

Early blight will first appear on the oldest lower leaves. You’ll see brown spots that look like targets, and the leaves will yellow around it. Eventually the whole leaf will turn brown, die and fall off.

To help prevent early blight from devastating your plants, try rotating crops — moving them to a different area of the garden with fresh soil. However, if your plant is already infected with early blight, you can treat it using an organic fungicide.

Over fertilizing
Feeding your plants is important, but feeding them too much can be just as detrimental as not feeding them at all. If used too frequently, fertilizer can build up in the soil and cause problems.

Fertilizer provides plants with nitrogen, which is great. However, excessive nitrogen can cause your plants to put more energy into growing leaves than growing the tomatoes.

To combat this issue of over fertilization, look for fertilizers specifically designed for tomatoes, or opt for a shovel full of natural compost.

Not Watering Properly
Inconsistent watering can lead to multiple problems for your plants, including blossom end rot. To water your plants correctly, consider:


  • Providing your plants with a consistent watering schedule. Ensure they are able to dry out a little bit so they are not drowning, but be sure they don’t dry out all the way.
  • Watering early before the sun is in full force. Damp leaves can get leaf burn or other issues from lingering water.

Here’s How You Can Curb Tomato Losses

Tomato farmers have reported losses due to ongoing rains. What do farmers need to know when handling tomatoes to reduce post-harvest losses?

Most tomato losses start from the farm, during the growing period and after harvest. Generally, good agronomic practices will save farmers post-harvest losses. Pest and diseases like Tuta absoluta, caterpillars, tomato blights, anthracnose and bacterial speck are the lead causes of post-harvest losses in tomatoes. During rainy seasons, anthracnose, bacterial speck, damping off, powdery mildew, early and late tomato blight are common. Sometimes the tomato will look good when harvested but two days later, you find it going bad. This may be due to Tuta absoluta embedded in it.

Farmers should also avoid harvesting immature tomatoes. Delayed harvesting also leads to losses as the fruit is perishable. In most cases, marketing losses occur due to glut or spoilage.

What qualities show a tomato variety has longer shelf-life?
There are two major qualities in tomatoes that can guarantee longer shelf-life namely the outer cover and juicy content of the fruit.

The tougher the outer cover, the longer it lasts. Tomatoes with more juicy content after ripening go bad easily. Of course factors such as fertilisers applied, pest and diseases play a major role in the shelf-life of tomatoes.

What are the favourable conditions for storing tomatoes?
Have the area in controlled environment in such a way that there is enough ventilation to reduce the accumulation of heat from respiration. For longer-term storage, ripe tomatoes can be stored at temperatures of about 10–16°C and 85–95 per cent relative humidity. The area should be free from moisture.

What are the post-harvesting technologies available for farmers?
There are special packaging products that prolong the shelf-life of fresh farm produce. They include Xtend bags which prolong for more than 10 days. Another technology a farmer can apply is to use solar energy to cool rooms where tomatoes are stored. Alternatively, use charcoal coolers to store the tomatoes after harvest.

What is the ideal packaging for transporting tomatoes to market?
A more simpler material is plastic sorting crates. The crates provide more ventilation and are less damaging to the produce than traditional wooden boxes. The plastic crates reduce tomato loss in transit by 78 per cent and are ideal for transporting not only tomatoes but also any other vegetables. These crates are designed to interlock without causing any bruises on the tomatoes during transportation. The wooden boxes host 60 to 100kg of tomatoes, so when they are piled on each other, tomatoes arrive in the market squashed. Besides, wooden boxes are rough, and once the fruit gets a small bruise, infections set in.

What are the challenges farmers face in reducing post-harvest losses in tomatoes?
Most farmers lack knowledge and information on how to minimise post-harvest losses. Some of the losses are avoidable, for instance, if only they did research on the market need, used the right seed and spray suitable crop protection chemicals on time. The market trend is a key determinant to everything in the tomato value chain.

How can farmers ensure they get tomato market?
Establishment of co-operatives will help them have collection centres for the produce and reach bigger market. If there is over production, they can easily add value to the tomatoes instead of letting them go bad and throwing them away.