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Tomato growing (Part III)The largest exporters are Mexico, the Netherlands and Spain, while the major importers are the United States, Russia and Germany. By proximity, it would be logical to think that Mexico exports mainly to the USA.
1. Origin
2. Taxonomy and morphology 3. Economic importance and geographical distribution 4. Edaphoclimatic requirements 5. Vegetal Material 6. Growing techniques 6.1. Settings for planting 6.2. Pruning 6.3. Ridging up 6.4. Trellising 6.5. Shoot thinning 6.6. Leaf thinning 6.7. Blunting of inflorescences and fruit thinning 6.8. Fertigation 7. Soilless crop 8. Pests and illnesses 8.1. Pests 8.2. Illnesses 9. Alterations of fruits 10. Harvest 11. Post harvest 12. Nutritional value 13. Marketing 8.2. Illnesses - Powdery Mildew (Leveillula taurica) It is an ascomycete fungus of semi-internal development and the conidiophores come out through the stomata. The wild solanaceae acts as a source of inoculums. It develops in a temperature of 10-35°C with an optimum of 26°C and a relative humidity of 70%. The symptoms are yellow spots on the upper side of the leaves which undergo necrosis at the middle, showing a white felt on the underside. As the disease progresses, the spots continue to spread (surface and number) from senescent to young leaves. In case of heavy attack, the leaves dry and fall out. Preventive control and cultivation techniques - Elimination of weeds and crop residues. - Elimination of damaged senescent leaves. - Use of healthy seedlings. - Proper management of ventilation. Chemical control
- Grey mould (Botryotinia fuckeliana, Botrytis cinerea) It is a parasite and saprophyte fungus. In seedling, damping-off occurs while brown lesions are produced in leaves and flowers. A soft mould occurs in fruits (more or less aqueous, depending on the tissue), in which the grey mycelium of the fungi is observed. The main sources of inoculums are conidia and plant residues that are dispersed by wind, splashing rain, drops of condensation on plastic and irrigation water. Infected and detached petals also disperse the fungi. The temperature, relative humidity and phenology can separately or jointly affect the development of the disease. The optimum relative humidity ranges around 95% and the optimum temperature is between 17ºC and 23ºC. Preventive control and cultivation techniques - Elimination of weeds, crop residues and infected plants. - Take special care in time of pruning, making clean cuts and fit flush with the stem. If possible, the pruning is done when the relative humidity is not very high. Apply fungicidal paste. - Control the levels of nitrogen and calcium to avoid excessive vegetative development which favours the development of moulds. - Use plastic covers in the greenhouse to absorb ultraviolet light. - Use suitable plantation setting that allows aeration. - Proper management of ventilation, both lateral and aerial. - Provision of adequate irrigation water. Irrigation favours the increase of relative humidity and thus the occurrence of these diseases. Biological control - Prepared biological made of Trichoderma harzianum Rifai T39. Chemical control
- White mould or white rot (Sclerotinia sclerotiorum) Polyphagous fungus that attacks most horticultural species. In seedling, damping-off occurs. In plant, it produces a watery soft mould at first (no apparent bad odour) which dries out later, depending on the succulence of the affected tissues, covering a rich white cottony mycelium and the presence of numerous white sclerotia which turn to black later on. The frequent attacks and the sclerotia inside the stem will quickly destroy the plant. The disease starts from the ground sclerotia from previous infections, which germinate in conditions of high relative humidity and mild temperatures, producing a variable number of apothecia. The mature apothecium produces numerous spores, which mainly affect the petals. When they fall on stems, branches or leaves, secondary infections are produced. Preventive control and cultivation techniques - Elimination of weeds, crop residues and infected plants. - Use plastic covers in the greenhouse to absorb ultraviolet light. - Use suitable plantation settings to allow aeration. - Proper management of ventilation and irrigation. - Solarization. Chemical control
- Mildew (Phytophthora infestans) This fungus is the causal agent of mildew of tomato. It attacks the aerial part of the plant at its any stage of development. At first, oily irregular stains appear on the leaves which quickly become necrotic and invade almost all the leaflet. Around the affected area, a small margin is observed which in the presence of moisture, shows a whitish felt on the underside. Brown spots appear that grow larger and usually encircle the stem. It also affects immature fruit, manifesting large brown spots, vitreous and an irregular contour. Infections usually occur from the calyx until they cover the top half of the fruit. The dispersion of the fungus is by the action of wind and rain, by sprinkler irrigation, sprays and drops of condensation. The favourable conditions for its development are high relative humidity (above 90%) and temperatures between 10-25ºC. Existing vines are: T0.0 (only affects potato), T.0 (affects tomato varieties without resistance) and T.1. (affects tomato lines with Gen Ph1). There are varieties of tomato with Gen Ph2, but their protection is not complete. Preventive control cultivation techniques - Removal of diseased plants and fruits. Chemical control
- Alternaria (Alternaria solani) Saprophytic fungus that produces a black seedling blight on stem at ground level. During cultivation, lesions appear in leaves, stems, fruits and petioles. The symptoms are: - Leaves: small circular or angular spots with marked concentric rings. - Stem and petiole: black elongated lesions which sometimes can be observed concentric rings. - Fruits: The fruits are attacked from the scars of the calyx, causing slightly sunken dark-brown lesions and are covered with numerous fungal spores. Inoculums sources are wild and cultivated Solanaceae, infected seeds and residues of diseased plants. Conidia can be dispersed by splashing water, rain, wind, etc. The optimum temperature for development of the disease is between 20-35°C, sporulation is favoured by the occurrence of humid nights followed by consecutive sunny days and elevated temperatures Preventive control and cultural techniques - Elimination of weeds, diseased plants and fruits. - Proper management of ventilation and irrigation. - Use of healthy seeds or disinfected and healthy seedlings. - Balanced fertilizer. Chemical control
- Fusarium oxysporum It is a deuteromycete fungus that causes falling of petioles of the upper leaves. The lower leaves turn yellow progressing toward the apex and eventually die. Green wilt may manifest at the aerial part of the plant, this may be reversible. Then it becomes permanent and the plant dies. The disease can also manifest yellowing in the lower leaves, which ends up drying the plant. If cross-section is done on the stem, darkening of the vessels is observed. The fungus may persist in the soil for years and penetrate through the roots into the vascular system. The dissemination is done by wind, seed, ground work, diseased plants or contaminated tools. The optimum growth temperature is about 28°C. Preventive control and cultivation techniques - Crop rotation. Gradually reduces the pathogen in infected soil. - Removal of diseased plants and crop residues. - Use of certified seeds and healthy seedlings. - Use of resistant varieties. - Disinfection of the structures and working tools. - Solarization. Chemical control - Chemical treatments are ineffective during cultivation. - It can be performed preventive treatments with the following active ingredients:
- Tomato black spot (Pseudomonas syringae) It is the most common bacterial blight in tomato. It affects all aerial organs of the plant. In leaf, small black spots are formed (1-2 mm diameter) and surrounded by yellow halo, which may coalesce and may even dry the leaflet. In stems, petioles and edges of the sepals, irregular black spots appear. The affected inflorescences fall. Green fruits are only attacked, in which small sunken spots is observed. The main sources of infection are contaminated seeds, plant residues and contaminated rhizosphere of numerous wild plants. Wind, rain, raindrops and sprinkler irrigation spread the disease, whose penetration via stomata and possible wounds of the plants. The optimal conditions for its development are temperatures of 20-25°C and wet periods. Preventive control and cultural techniques - Elimination of weeds, diseased plants and fruits. - Proper management of ventilation and irrigation. - Use of healthy seeds or disinfected and healthy seedlings. - Balanced fertilizer. Chemical control
- Virus
- Tomato Yellow Leaf Curl Virus (TYLCV) This disease consists of a complex viral TYLCV, belonging to the genus Begomovirus, causing severe losses in tomato crops. The virus is acquired from infected plants affected by larvae of whitefly (Bemisia tabaci) and transmitted by the adult. Typical symptoms of the disease are visible after 2-3 weeks, depending on environmental conditions. The most common symptoms are: - Sprouts with leaflets rolled into the upper part of the leaves, marked chlorosis in its terminal phase and leaf area reduction. - Helically shaped petiole. - Progressive reduction of the leaf blade. It may even disappear, leaving only the curved midrib. - Loss of flowers, lack of fruit set, fruits are smaller and pale in colour. - Early infection causes a severe reduction in plant growth and consequently a significant decrease in fruit production. There are many weeds that can harbour the virus, including most notably: Solanum nigrum, Datura stramonium, Mauve parviflora and Sonchus spp. There are also numerous cultivated plants that act as hosts of this virus: tobacco, pepper and beans. Control - Continued biological control to control whitefly populations. - Use chromotropic traps (yellow tapes) to record the presence of whiteflies. - Treatments for whitefly when the first symptoms of the disease appear ineffective. Suitable insecticide treatments should be done to stop any whitefly infestations, using various active substances gradually to prevent the emergence of resistance. - Use of resistant varieties. - In the case of greenhouse cultivation, avoid if it have been preceded by ornamental crops such as poinsettia (Euphorbia pulcherrima) and gerbera; since the TYLCV is registered in these two species. - Clean residues from previous crops. - Elimination of weeds. - Use of mosquito nets and thermal blankets. - Sealed greenhouse structure to prevent passage of insect vectors. - Placement of double door or door-mesh at the entrance of the greenhouse. - Cucumber Mosaic Virus (CMV) In 1999 the disease was detected in tomato crops in several European countries and the United States, spreading in areas of intensive cultivation of tomato in both continents. It is a viral species that belongs to the genus Potexvirus, comprising at least 30 other viral species characterized by having flexuous and filamentous particles. The manifestation of CMV depends on: - Cropping system. - Planting dates. - State of development of the plants. - Environmental conditions. - Time of year. - Plant behaviour of varieties. The first symptoms occur during the spring, consisting of intense yellow mosaic in mature leaves from the middle stratum of the plants and uneven distribution in the leaflets. Sometimes the mosaic development is so intense that a marked deformation and even wilting occurs on the leaves. Discoloured longitudinal grooves on the stems, petioles and fruits may occur. In young plants, more or less marked distortion of the leaflets and reduced development of these occur. The most common and characteristic symptom is the blistering of leaf blade. On fruits, a mosaic of different colours, ranging from red to orange-yellow appears. This symptom is accentuated when nutritional imbalances occur. The result is a mottled tomato of red-orange coloration with lower visual quality and unmarketable. Early infections originate reductions in terms of production, loss of flowers or by poor fruit set. In the case of wilting, it reduces the harvest and it delays the production. The danger of this virus is its easy transmission and its ability to remain in the plant residues. It is transmitted from plant to plant by infected seed (the virus contaminates the seed coat), bees (pollination of tomato), tools and work clothes, irrigation equipment, water (through the leachate reused nutrient solutions), etc. The virus remains in the contaminated plant debris and soil. Control 1. Before planting: - Remove debris from the previous crop uprooting plants including their root system. - Remove weeds both inside and on the periphery of the greenhouse, and with or without cultivation. - The virus can survive a long period of time in plant residues. - Drying and disinfecting the substrate in soilless crops. - Disinfection of the irrigation system. - Disinfection of structures, facilities, machinery, tools, gloves, etc. - Use of seedlings from authorized supplier with health guarantee. - Seeds with Phytosanitary Certificate. 2. During cultivation: - Periodic inspections. 3. Detection of diseased plants: - Elimination of suspicious and immediately nearby plants. Introduce them in a bag and take them out of the ground without touching any other. - Prevent the staff to pass from an affected greenhouse to another. If it is not possible, clothes, shoes and protective equipment must be changed. - Avoid indiscriminate visits. - Disinfect pruning tools and lines between planting and as often as possible with 5% bleach. These should be immersed for half an hour and frequently change the disinfectant solution. - Disposable body protection in infected greenhouses. - Mark the affected area. It should start working from the unaffected to affected area. 9. ALTERATIONS OF FRUIT - Blossom end rot: It begins with the appearance of light tan lesions that increase in size to darken and become leathery, and often can be masked by a secondary black rot. It starts from the pistil´s scar area, but may also occur on either side. Sometimes internal black lesions that are not visible on the outside of the fruit are produced. The emergence of this disorder is related to deficient levels of calcium in the fruit. Water stress and salinity also directly influence their appearance. There are also different levels of varietal sensitivity. The fruits affected by blossom end rot mature much faster than normal fruits. - Internal white tissue: the formation of white tissue is generally found in the outermost layer of the fruit. Sometimes the affected tissue extends from the centre of the fruit. This physiopathology can be very variable. For example, in tomato of the same cluster, they may differ from each other in terms of the amount of white tissue that forms on them. An adequate nutritional state, especially in terms of potassium, reduces the formation of white tissue. It is recommended to avoid stressful conditions and the use tolerant cultivars. - Cracking o microcracking: There are two types of cracking in tomato: the concentric and radial. - The concentric cracking consists of the breakage of the epidermis forming circular patterns around the stem scar. - The radial cracking consists of a breakage, radiating from the stem to the blossom scar. The fruits in ripening state are more susceptible to cracking. This disorder occurs when the fruit reduces its growth rate due to adverse environmental factors. When the optimal environmental conditions returns, the fruit accelerates its growth trying to expand more. However, the fruit has been growing at a slower pace and the fruit walls thereof have been tightened and tend to be less elastic. This hinders its own expansion and consequently, cracking occurs. The main causes of this condition are: Imbalances in irrigation and fertilization and sudden drop in night temperature after a period of heat. Therefore, the fruit that is exposed to the environment cracks more easily than those that are protected by the foliage. - Catface: The tomatoes with this disorder usually lack shape and have large scars and holes in the blossom end of the fruit. Sometimes the fruit is kidney-shaped with long scars. The causes are cold weather (T <15°C, three weeks before flowering exacerbates the problem), excessive pruning and nitrogen levels as they can aggravate the problem. - Hollowed: These are fruits with fewer seeds and hollow cores due to non-presence of placental tissue. For this reason, the fruits have a lower weight and a somewhat have hexagonal shapes. This disorder is due to a period of adverse environmental conditions (low or high temperatures, reduced solar intensity, rain, etc.), imbalance between auxin and cytochemicals and nutritional imbalances (especially potassium deficiency. - Sun scald or sunburn: It's basically a physical warming of the fruit due to the heat of the sun. To prevent the occurrence of this disorder, an adequate volume of foliage to shade the fruit must be maintained. - Blotching ripening, Tomato irregular ripening: These are fruits that have an uneven ripened surface. TIR: fruit with a star-shaped yellowish spot from the apex of the fruit. Blotching: more or less rounded greenish areas, which may occupy a considerable area of the fruit. Both disorders are associated with potassium deficiencies or excesses of nitrogen. The bites made by whiteflies or TSWV also favours the presence of these physiopathology. - Zippering: It is a long zipper or stitches-shaped scar of genetic origin (depending on variety). This disorder is due to the accession of the anther of the flower to the edge of the ovary of the fruit. When the fruit grows, the anther splits and leaves the scar. - Silvering: The leaves present gray-green spots of various sizes on one side, leaf deformation and streaks on the stem. There may also be partial or total sterility of flowers and consequently, deformed fruit are produced with silver streaks that turn pale yellow at maturity. This condition is genetic but it is true that early planting and canopy covering decrease of temperature may favour its appearance. For these reasons, the use of resistant varieties is recommended. - Yellow collar: The appearance of yellow collar occurs when the fruit is about to ripen and the environmental conditions are characterized by high temperatures or sudden changes therein. Yellow collar can be avoided by adequate potassium fertilization and no excessive pruning at the end of the planting season. 10. HARVEST In general, the minimum required ripeness to harvest (Mature Green 2) corresponds to the time at which the seeds are fully developed and cannot be cut by slicing the fruit. The gelatinous material is present in at least one of the locular cavities and is developing in others. In "Long Life" tomatoes, normal ripening is severely affected when the fruits are harvested in Mature Green 2 state (MG2). The minimum maturity to harvest corresponds to the class Pink (state 4 of the standard colour table used by the USDA). In this state, more than 30% but less than 60% of the fruit surface shows pink to red colour. On the other hand, tomato in cluster has a different rate of harvest, which must be adapted to the ripening of the fruits that form clusters. In winter, with long growing cycle and in a greenhouse without heating system, the period between the harvest and other phases will be greater than in spring due to rising temperatures. 11. POSTHARVEST - Quality: The quality of fresh tomato is mainly based on the uniformity of form and the absence of growth defects and handling. Size is not a factor that defines the degree of quality, but may have an important impact on the expectations of marketable quality and the market that is chosen. - Form: Well formed according to the variety (round, globose, oval or flattened globe, depending on type). - Colour: Uniform (orange-red to deep red, light yellow). No green shoulders. - Appearance: smooth and with scars corresponding to the floral tip and to the small peduncles. Absence of physiological disorders, sunburn, insect damage and mechanical damage or bruising. - Firmness: Firm to touch. Not soft and easily deformed due to ripeness. - Optimal temperatures: In general, the storage temperature should be between 10-15°C although the proper conditions for tomato conservation depend on the ripeness of the fruit - Mature Green: 12.5-15°C - Light Red: 10-12.5°C - Mature Firm: 10-12°C - Ripening temperatures: 18-21°C and 90-95% RH for normal ripening 14-16°C for slow ripening. - Chilling injury: Tomatoes are sensitive to chilling injury at temperatures below 10°C. If they are kept in these conditions for 2 weeks or at 5°C for longer than 6-8 days period. Symptoms include alteration in ripening (inability to develop a full colour and full flavour, irregular coloration, premature softening), chopped (depressions on the surface), browning of seeds and increased rotting (especially black rot, black mould, caused by Alternaria spp.). Chilling injury is cumulative and can be started in the field before harvest. - Optimum relative humidity: 85-90%. High humidity is essential to maximize postharvest quality and prevent water loss (drying). Prolonged periods of high humidity can increase the rotting of peduncle´s scar and the fruit surface. - Respiration rate:
- Rate of ethylene production: 1,2-1,5µl/kg.h a 10°C y 4,3-4,9µl/kg·h a 20°C. - Effects of ethylene: Tomatoes are sensitive to ethylene present in the environment. Exposure of fruit in mature green state to this gas causes the onset of ripening. Tomatoes along the ripening process produce ethylene at a moderate rate. For this reason, tomatoes are not be stored or transported with ethylene sensitive products. - Ripening: The ripening process is fast at temperatures between 12.5-25°C and RH 90-95%, so a good airflow must be kept in order to ensure the uniformity of temperature in the ripening room and to prevent the accumulation of CO2 (CO2 delays the action of ethylene to stimulate ripening). The optimum ripening temperature that ensures good sensory and nutritional quality is 20°C. At this temperature the colour development is optimal and the retention vitamin C is high. Once harvested, if the tomatoes are ripened at temperatures above 25°C, they develop somewhat yellowish colour and are softer. The treatment with ethylene usually lasts 24-72h. Sometimes when green-fruits are harvested in its immature state, a second treatment is applied after re-packaging. - Effects of controlled atmosphere (CA): The controlled atmosphere storage provides a modest benefit. Low concentrations of O2 (3-5%) delays ripening and decay development in stem scar and surface without severely affecting the sensory quality. Up to 7 weeks of storage using the following combination: 4% O2, 2% CO2 y 5% CO. 12. NUTRITIONAL VALUE
13. MARKETING Exports and imports of tomatoes in 2011 (last reference contained in the FAO), are observed below. It only shows the top 15 positions in both.
The summary table shows that the largest exporters are Mexico, the Netherlands and Spain, while the major importers are the United States, Russia and Germany. By proximity, it would be logical to think that Mexico exports mainly to USA while the Netherlands and Spain to Russia and Germany. Author: Infoagro
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