Tree tomato

The ideal field for tamarillo should have not be grown with tomato, eggplant, potato pepper and tobacco or any other Solanaceous crop for the last 3-4 seasons. The field has to be ploughed at a depth of about 20-30 cm, the debris removed, and then leveled.

1.1. Propagation in nursery

• Seed extraction

The tamarillo seeds should be extracted from fruits harveted on vigorous and heavy fruit bearing and healthy trees to prevent seed borne diseases.

Fruits are harvested at their physiological maturity after they have changed completely the colour and are kept in a dark place for about 1 to 2 weeks. Before cutting the fruits to remove the seeds, fruits are washed in wáter containing a desinfectant like JIK (1%).

After being extracted from fruits, seeds are also washed in wáter containing a desinfectant and the sticky substance around the seeds is completely washed out. Then, seed are dried in absence of direct sun light for about 3-10 days after which they are ready for sowing and they can keep germination power for about 3 month in dry and cool storage conditions.

One gram (1g) contains about 150-160 seeds.

• Nursery site selection and preparation

• The ideal site for the nursery should be under the sun and not have been grown with crops of the same family for last 3-4 seasons. The nursery soil should be well aerated, drained and with good pH. The site should be ploughed to a depth of 20-30 cm and removed with stones, weeds and debris.
• The nursery soil should also be free from diseases and pests. It should be applied with well decomposed organic manure (5 kg/m²) and the inorganic fertilizer such NPK 17-17-17 (20 g/m²) one week before sowing as well as fungicide and insecticide 2-3 days before sowing.
• The raised beds of 1-1.2m width and 20cm depth are made.
• Sowing and nursery management
• The quantity of seeds required is 25g for 1ha (2.5g for 1 are). Care should be taken to use non expired seed and this from credited sources.
• During the day of sowing, the bed surface is levelled and sowing lines of 0.5cm depth are made using a stick. Seeds are sown in lines at the spacing of 20cm x 5cm and are covered with soil. Then, the much is applied on the bed, followed by regular watering. Movable shade is also provided to protect seedlings from direct sunlight and heavy rain intensity.
• Upon germination (7-10 days after sowing), the mulching material is removed. The seedlings should be protected from the direct sunlight.
• One month after sowing, when seedlings are about 5cm in height they are transplanted in pots having 13 cm diameter.
• Fungicides like Mancozeb (2.5g/L of water) and insecticides like Lambda-Cyhalothrin (1m/1L of water) can be applied when necessary.
• To harden the seedlings, watering frequency is reduced and seedlings are gradually exposed to direct sunlight 1-2 weeks before transplanting.
• Seedlings will be ready for planting in main field about 3 months after sowing.

1.2. Transplanting

The season A is the best time for transplanting. Planting holes of   0,6 x 0,6 x 0,6 m are prepared and the soil mixed well with 12 kg of organic manure.

Tamarillo plants are planted in rows with 1.5 m – 2 m between plants and 2 m between rows. This makes 2500 plants per hectar for the spacing 1.5m and 2 m spacing between plants, respectively.

1.1. Mulching

Mulching is a popular agronomic practice in agriculture and it has many advantages which include: to prevent loss of soil moisture, to control weeds by shading them and diseases by preventing soil contact with the plant foliage, to control soil temperature, either by keeping it cool or keeping it warm, to add to soil fertility and increase soil organic matter content when organic mulch is used and decay takes place (AVRDC, 1990)

1.2. Irrigation

Tamarillo plants are sensitive to drought. Lack of water limits plant growth, fruit size and yields. It is likely that tamarillo plants will need irrigation during dry periods and peak growth times. Water should reach right through the root zone. How regularly you need to irrigate will depend on how well your soil holds moisture, and the time of year. It is a good idea to get advice about the most suitable irrigation for your situation.

1.3. Weeding

Weed control is also important as some weeds such as chickweed and deadly nightshade can harbour viruses that infect tamarillos. Weeds also compete for light, water and nutrients especially when tamarillos are young.

1.4. Pruning

Tall plants grown from seed should be cut back at planting. Prune the main stem to about 0.5m to promote branching lower on the tree (they naturally branch at about 2m). However, plants grown from cuttings are likely to grow with many low branches. These may need to be removed so the plant branches far enough above the ground. Regular removing of waterspouts is important so as improve on aeration in crop canopy.

Fruit is produced on the current season’s growth. Pruning helps to balance total yield and fruit size. On un-pruned plants, fruit is produced further and further out on the branch each season. This leaves old growth in the middle without fruit. Old growth is weak; so un-pruned branches may break, reducing overall yield.

When pruning, you should remove old, dead and diseased wood.

1.5. Fertilization

The light, well drained soils that tamarillo plants grow best on often have problems with nutrient leaching and may not be very naturally fertile. It is recommended that you test the soil at your chosen site for nutrients and that any lacking nutrients are applied before you plant your crop.

Tamarillo plants respond well to high levels of organic manure and have a high requirement for nitrogen, potassium and magnesium in particular.                   It may also be necessary to apply phosphorus as some soils are very low in available phosphate. Once soil nutrients are at a reasonable level it is recommended that you apply potassium and phosphate annually and nitrogen several times throughout the growing season.

It is recommended to apply 25-30T/ha of organic manure at the time of planting. The nitrogen, phosphorous and potassium required per year are 100:100:100kg/ha which makes about 600kg of NPK 17-17-17. This mineral fertilizer is applied into 3 splits: at planting, 3 month and 6 months after planting. For the following years, the recommended NKP is also given into 3 splits at 4 months intervals.

1.1. Fungal diseases

The major fungal diseases include anthracnose (Glomerella cingulata), powdery mildew (Erysiphe sp., Oidium sp.), and verticillium wilt, a soil-fungal disease which can affect tomato, potato, and eggplant (Morton, 1987; Prohens and Nuez, 2005; Orwa et al., 2009). Other fungal diseases of tamarillo are ascochyta disease, black spots disease, etc.

1. Powdery mildew

The fungus grows on the plant and produces spores that appear as white powder on the surface of leaves; which is the characteristic symptom of the disease. If not controlled, the disease can cause defoliation of the whole plant.

Management:

• Avoid overcrowding of plants.
• Application of a sulphur based fungicide like Thiovit/Thionil at 40g/20L of water with 2 weeks spray interval. Spray benomyl (e.g. benobest) at 40g/20L water in alternation with the above product.

b) Verticillium wilt

The fungus infects plant through the roots and then travels up the plant stem. Leaves, stems and fruit are all affected by the disease. Affected leaves become yellow gradually. Other disease symptoms include leaf necrosis and wilting and internal brown discoloration of the stem, which help to distinguish it from other causes of yellowing, such as virus, nematodes, root rot.

Management:

Crop rotation for about 3-4 years is recommended to prevent this disease. Care is needed also not to transmit the pathogen through soil movement on tools and boots.

c) Ascochyta disease

This disease is characterized by dry circular and concentric rings which are black or dark brown in colour, mainly on older leaves.

Management:

• Application of a sulphur based fungicide like Mancozeb or Copper oxychloride 40g/20L of water with 2 weeks spray interval.

 

1.2. Bacterial diseases

Bacterial diseases can also attack tamarillo but they are not an important problem. However, bacterial wilt, bacterial canker of tomatoes (Corynebacterium michiganense), bacterial blast (Pseudomanas syringae and P.solanacearum) and crown canker (Agrobacterium sp.) have been shown to cause damage (Prohens and Nuez, 2005).

There is no direct control measure for bacterial diseases; proper hygiene is required to prevent these diseases. The affected plants should be removed and burned.

1.3. Viral diseases

Tamarillo is susceptible to a number viruses including tamarillo mosaic virus (TaMV), Potato aucuba mosaic virus (PAMV), alfalfa mosaic virus (AIMV), tomato spotted wilt virus TSWV), arabis mosaic virus ArMV), tobacco strick virus (TSV), and tomato aspermy virus (TAV).

Symptoms:

All virus will cause loss of yield and “mottling” on the fruit (this does not affect eating quality). Symptoms are most severe on young or unhealthy plants, and will be worst if several viruses have infected the plant at once.

Management:

• Good orchard hygiene, pruning and burning infected plants and a good pest management program will help to reduce pests and diseases.
• However once a plant is infected there is no treatment – prevention is the only solution. Thus, It is important to have good control over aphids and whiteflies as they are carriers of viruses.
• Weed control is also important as some weeds such as chickweed and deadly nightshade can harbour viruses that infect tamarillos. Weeds also compete for light, water and nutrients especially when tamarillos are young.

1.4. Aphids and whiteflies

Different species of aphids attack tamarillo but the green peach aphids (Myzus persicae) are the most important. They are vectors of several viruses that affect tamarillo such as cucumber mosaic virus (CMV) and potato virus ‘Y’ (PVY).

Whiteflies secrete honey dew over the leaves and fruit. This can lead to the appearance of sooty mould, which leaves fruit unsalable. They also transmit viral diseases.

Prevention:

• A complete crop break will help ensure complete eradication of the pest and prevent carry-over into subsequent crops.
• Use pest-free planting material.
• Keep recently received plants isolated to monitor closely and prevent the spread of any potential infestation.
• Field sanitation to destroy weeds which may act as refuge and alternative hosts.
• Where possible, protect seedlings from infection by growing them under 60 mesh screening.
• Conserve natural enemies: parasitic wasps (Hymenoptera) in the family Aphelinidae, lady bird bettle, etc.

Monitoring:

• Thoroughly inspect plants before planting for all stages of the pest, particularly on the underside of leaves. They are usually found on young leaves.
• Monitor throughout the growing season with yellow sticky traps.
• Check for the presence of whiteflies by agitating plants to encourage flight by adults and inspect the leaves for immature “stage”

Direct control:

• Begin treatment immediately if any life stages of the pest are detected to ensure prompt eradication.
• Application of insecticidal soaps and oils is effective in controlling aphids and whiteflies. Spraying water underneath the leaf also help to kill adults and reduce the number of eggs laid.

• Chemical control can be achieved using Lambda-Cyhalothrin at 1 ml/1l of water at 14 days interval. Alternate   the above pesticide with any one of the following: imidacloprid, acetamiprid, abamectin, nimbecidine (1 ml/1l of water) at 14 days interval.

Tamarillos start producing fruit 10-12 months after planting, yields of up to 16 tones/ha are possible, but production tends to drop off as the crop is getting old as some trees may be lost. The commercial life of a tamarillo plantation is about 8 years when diseases are well managed.

After the harvest, Tree tomatoes are handled with care so as to minimise post harvest damages and losses. They are, thus sent to the market or processing plants for sale as raw fruits or raw materials for juice making plants.

Tomato tree fruits are eaten alone or processed into delicious juices, either alone or blended with other fruits.