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Cucumber Growing (Part II)Practical guide for a professional and intensive production of cucumber, vegetable that belongs to the cucurbitaceous family.
1. Taxonomy and Origin
- White Spider (Polyphagotarsonemus latus) This pest attacks mainly green peppers, but has occasionally been found in tomato, eggplant, beans and cucumber. The first symptoms are ripple of nerves in the apical buds and leaves, and curvatures in most developed leaves. In more advanced attacks, dwarfism and intense green color of the plants occurs. It is distributed in zones inside the greenhouse, although it disperses quickly in hot and dry periods. Chemical control Active substances: abamectin, paraffin oil, sulfur. - Whitefly (Trialeurodes vaporariorum and Bemisia tabaci) The young parts of the plants are colonized by adults by laying their eggs on the underside of leaves. The first larvae that emerge are mobile. After being fixed on the plant, they pass through three larval stages and one pupal stage. Direct damage (yellowing and weakening of the plants) are caused during larvae and adults feeding by absorbing the sap of the leaves. Indirect damage is due to the proliferation of black moulds produced during feeding. This damage stains and lowers the value of the fruits and hinders the normal development of the plant. Both types of damage become important when the pest population level is high. Another indirect damage that takes place is the transmission of viruses. Trialeurodes vaporariorum transmits the virus that causes the yellowish colour in cucurbitaceous plants. Bemisia tabaci is a potential transmitter of great number of viruses in vegetable crops and nowadays it acts as a transmitter of tomato yellow leaf curl virus (TYLCV). Preventive control and cultivation techniques - Placement of mesh on the bands of the greenhouse. - Cleaning of weeds and crop residues. - Do not combine different crops in the same greenhouse. - Do not leave the buds at the end of the cycle, as young shoots attract adult whiteflies. - Placement of yellow chromatic traps. Biological control through natural enemies Major parasites of whitefly larvae: - Trialeurodes vaporariorum. Native beneficial insects: Encarsia formosa, Encarsia transvena, Encarsia lutea, Encarsia tricolor, Cyrtopeltis tenuis. Beneficial insects used in release. Encarsia formosa, Eretmocerus californicus. - Bemisia tabaci. Native benefical insects: Eretmocerus mundus, Encarsia transvena, Encarsia lutea, Cyrtopeltis tenuis. Beneficial insects used in release.: Eretmocerus californicus, Eretmocerus sineatis. Chemical control
- Aphid (Aphis gossypii and Myzus persicae) They are the most common and abundant aphid species in greenhouses. They exhibit polymorphism, with winged and wingless females of viviparous reproduction. The wingless types of Aphis gossypii have black siphons on their green or yellowish body while Myzus are completely green (sometimes brown or pink). They form colonies and are distributed in clusters that are scattered mainly in spring and autumn by the winged females. Preventive control and cultivation techniques - Placement of mesh on the bands of the greenhouse. - Elimination of weeds and wastes from the previous crop. - Placement of yellow chromatic traps. Biological control through natural enemies - Native predatory species: Aphidoletes aphidimyza. - Native parasitoid species: Aphidius matricariae, Aphidius colemani, Lysiphlebus testaicepes. - Native parasitoid used in release: Aphidius colemani. Chemical control
- Thrips (Frankliniella occidentalis) Adults thrips colonize crops by laying their eggs inside the vegetal tissues of leaves, fruits and especially of flowers (they are floriculture), where the highest levels of population of adults and hatched larvae are found in sunsets. Direct damage is caused by larvae and adults feeding, especially on the undersides of the leaves, leaving a silvery appearance in the affected parts which become necrotic later on. These symptoms can be seen in affected fruits (especially in pepper) and in extreme cases on the leaves. The laying of eggs can be observed when they occur in fruits (eggplant, bean and tomato). Indirect damage has the utmost importance due to the transmission of tomato spotted wilt virus (TSWV), which affects pepper, tomato, eggplant and beans. Preventive control and cultivation techniques - Placement of mesh on the bands of the greenhouse. - Cleaning of weeds and crop residues. - Placement of blue chromatic traps. Biological control through natural enemies Native beneficial insects: Amblyseius barkeri, Aeolothrips sp., Orius spp. Chemical control
- Leafminers (Liriomyza trifolii, Liriomyza bryoniae, Liriomyza strigata, Liriomyza huidobrensis) Adult females lay their eggs within the tissue of young leaves, where a larva that feeds on the parenchyma begins to develop, causing the typical galleries. The shapes of the galleries are different from one another, but not always distinguishable between species and crops. Once completed the larval development, larvae leave the leaves to pupate in the soil or on other leaves, to subsequently transform them into adults. Preventive control and cultivation techniques - Placement of mesh in the bands of the greenhouse. - Elimination of weeds and crop residues. - In heavy attack, remove and destroy the lower leaves of the plant. - Placement of yellow chromatic traps. Biological control - Native parasitoid species: Diglyphus isaea, Diglyphus minoeus, Diglyphus crassinervis, Chrysonotomyia formosa, Hemiptarsenus zihalisebessi. - Parasitoid species used in release: Diglyphus isaea. Chemical control - Active substances: paraffin oil, presented as emulsifiable concentrate doses of 0,75-1,50%. - Caterpillars (Spodoptera exigua, Spodoptera litoralis, Heliothis armigera, Heliothis peltigera, Chrysodeisis chalcites, Autographa gamma) The main difference between species in the larval stage is seen in the number of false abdominal legs (5 in Spodoptera and Heliothis and 2 in Autographa Chrysodeixis), or in the way of moving in Chrysodeixis and Autographa by arching their body (camel caterpillars). The presence of silks (long "hairs") on the surface of the body of the larva of Heliothis, or the dark brown coloration especially on the legs and head of the caterpillars Spodoptera litoralis, also differs them from other species. Spodoptera which do the laying of eggs in groups while other species do it in isolation. Damage is caused by larvae feeding. In Spodoptera and Heliothis, the pupal stage takes place on the ground while Chrysodeixis chalcites and Autographa gamma, takes place on the leaves. The adults are moths with nocturnal and crepuscular habits. The damage can be classified as follows: damage to the vegetation (Spodoptera Chrysodeixis), damage to the fruits (Heliothis and Spodoptera) and damage on the stems (Heliothis and Ostrinia) which they can get at the point of cutting the plant stem. Preventive control and cultivation techniques - Placement of mesh on the bands of the greenhouse. - Elimination of weeds and crop residues. - In the case of heavy attacks, remove and destroy the lower leaves of the plant. - Placement of pheromone traps and light traps. - To monitor the early stages of crop development, it is during this stage when they can produce irreversible damage. Biological control through natural enemies - Indigenous parasites: Apantelles plutellae. - Indigenous pathogens: VPNSe-SP2 - Biological products: Bacillus thuringiensis. Chemical control
- Nematodes (Meloidogyne javanica, M. javanica, M. arenaria and M. incognita) They affect practically all horticultural crops, producing root nodules. They penetrate underground roots. Fertilized females which are filled with eggs, take a globular aspect within the roots. Together with the hypertrophy produced in the tissues of the same roots, the results will be the formation of a sequence of nodules. These damages cause clogging vessels and prevent the absorption of nutrients by the roots that cause lower plant development, chlorosis, dwarfism and the appearance of green-wilt symptoms in the hottest hours of the day. They spread in lines or stands and are easily transmitted by irrigation water, by the farmer footwear, by the tools and by any means of land transportation. Furthermore, nematodes interact with other pathogens, either actively (as vectors of virus) or passively by facilitating the entry of bacteria and fungi through the wounds that they cause. Preventive control and cultivation techniques - Use of resistant varieties. - Disinfection of soil in previously infected plots. - Use healthy seedlings. Biological control through natural enemies - Biological products prepared with the fungus Arthrobotrys irregularis. Control by physical methods - Steam sterilization. - Soil solarization, which consists in raising the soil temperature by placing a clear plastic sheet on the floor for at least 30 days. Chemical control
7.2. Illnesses - Oidiopsis (Leveillula taurica) It is a parasite of semi-internal development and the conidiophores come out through the stomata. 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. In case of heavy attack, the leaves dry and fall out. The wild solanaceae act as an inoculums source. It develops in a temperature of 10-35°C with an optimum of 26°C and a relative humidity of 70%. Preventive control and cultivation techniques - Elimination of weeds and crop residues. - Use healthy seedlings. Chemical control Active substances: wettable sulfur, bupirimate, Cyproconazole, Cyproconazole + sulfur penconazole, triadimenol:. - "Ash" or powdery mildew of cucurbitaceous (Sphaerotheca fuliginea) The symptoms are white powdery spots on the leaf surface (upper and lower surface) that can cover the entire leaf vegetative structure. It also affects stems and petioles and even fruit in very severe attacks. Infected leaves and stems become yellowish and dry out. Weeds and other cucurbitaceous crops, as well as crop residues would be the sources of inoculums and the wind is responsible for transporting the spores and spreading the disease. The temperatures range between 10-35°C, with an optimum temperature of 26°C. The optimum relative humidity is 70%. Preventive control and cultivation technique. - Elimination of weeds and crop residues. - Use healthy seedlings. - Perform treatments to structures. Chemical control
- Mildew (Pseudoperonospora cubensis) This fungus is a parasite that requires free water to disperse their spores. The fungal mycelium is hyaline (colorless) and sporangia (where spores are produced), are gray and can be seen directly on the underside of leaves. In the presence of free water, sporangia release spores that travel in the water with its flagella and when they find a suitable area, germinate and infect the plant tissues, the optimum temperature for infection is 16 to 22ºC. Once the leaf is infected, fungal growth is favored by alternate warm daytime (25°C) and cool nighttime temperatures (15°C) and by a very high relative humidity of 80% to 90%. Temperatures below 5°C or above 35°C stop their development. The evening dews and morning mist favour the development of mildew. This disease occurs in the leaves of cucurbits. At first, light green spots appear on the leaf surface, which turn to yellow with angular shapes. On the underside, a gray-purple felt is formed where the spores of the fungus are produced. These spots become necrotic which cause the leaves to have a shriveled appearance. Petioles remain green, holding completely dried leaves, but still attached to the stem. Preventive control and cultivation techniques - Use healthy seeds or vegetal material. - Do not combine different crops in the same plot. - Remove and destroy damaged organs and trimmings. - Use resistant or tolerant varieties. - Expand the plantation setting as much as possible. - Reduce humidity. - Avoid the presence of free water on the crop. - Avoid excessive nitrogen fertilization. - Avoid excessive plant foliage. With regards to chemical control, treatment is needed when there are symptoms of the illness and when the conditions are favorable, always using authorized active substances and applying the recommended dose by technical staff. The application technique should get in well on the underside of the leaves, ensuring good coverage of these in all plants. Upon application, the lower leaves and stems of the plant should be reached too. Chemical control
- Grey mould (Botryotinia fuckeliana, Botrytis cinerea) Parasite that attacks a wide range of plant species, affecting all protected horticultural crops, being able to act both as a parasite and as a saprophyte. 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. 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. Infected and detached petals disperse the fungi. 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. - Use plastic covers in the greenhouse to absorb ultraviolet light. - Use suitable plantation setting that allows aeration. - Proper ventilation and irrigation management. 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 odor) 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 technique - 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
- Gummy stem blight (Didymella bryoniae) It affects mainly the cotyledons in seedlings where it produces rounded brownish spots, in which black and brown spots, distributed in concentric rings, is observed. The cotyledon dries up, producing lesions in the area of insertion with the stem. The most common symptom in melon, watermelon and cucumber are the "gummy stem blight" that is characterized by a beige stem wound, coated with pycnidia, and gummy exudates are often produced near the wound. In the aerial part, it causes wilting and death of the plant. The inner part of this stain will break and eventually will perforate the stem. Attacks on fruits occur in cucumber and courgette crops, which are characterized by throttling of the stylar scar area that is covered with pycnidia. It can be transmitted by seeds. Harvest waste is a primary source of infection and the spores can survive in soil, stems and in the structure of greenhouses. Infections are frequent in cuts after pruning and grafting. The ideal temperature for disease development is 23-25°C, favored with high relative humidity and excess nitrogen fertilizer. High light intensities diminish the development. Preventive control and cultural techniques - Use healthy seed. - Remove crop residues both around and inside the greenhouses. - Disinfection of greenhouse structures. - Ventilation control to reduce humidity. - Avoid excessive moisture in soil. Remove droppers from the base of the plants. - Infected fruits and pruning residues must be removed from the greenhouse. - Do pruning correctly. - Virus
- Cucumber vein yellowing virus (CVYV) The CVYV is an RNA virus with flexuous particles of 740-780nm in length, belonging to the family Potyviridae. It is widespread throughout the eastern Mediterranean: Israel, Turkey and Jordan Valley. This virus affects species of the Cucurbitaceae family: cucumber, courgette, watermelon and melon. There are two strains: Jor-CVYV produce similar symptoms in cucumber and melon (yellowing of the veins), although Jor - CVYV causes more dwarfism in cucumber. The symptoms of this virus in cucumber are vein yellowing, although depending on the scale of infection, the symptoms can be seen throughout the plant or just part of it. Light-green or dark-green mosaics occur in cucumber fruits. If this virus is associated with cucurbit yellow stunting disorder closterovirus (CYSDV) virus, it produces a synergy that enhances the symptoms of both viruses. Transmission of this virus is carried by the insect vector Bemisia tabaci in semi-persistent way. The insect retains the virus for 6 hours and has a latency period of 75 minutes. The virus needs at least 15 to 20 insects per plant for its transmission. The life cycle of the whitefly on cucumber crop at constant temperature, can be completed in 17,8 days at 32°C and 38,2 days at 20ºC. Control - Use of resistant varieties. - Surveillance and vector control in the early stages of cultivation and seedbeds. - Placement of mesh in the bands and ridge of the greenhouse with a minimum density of 10 x 20 threads/cm2, except in those cases that do not allow adequate ventilation of the greenhouse. - Placement of double door or door and mesh (minimum 10 x 20 threads/cm2) at the greenhouse entrance. The greenhouse structure must be completely sealed to prevent passage of the insect vector. - Placement of yellow chromotropic traps for monitoring and capturing whiteflies. - Remove plant residues and weeds in and around the greenhouse, leaving more than a meter perimeter clean of weeds. - Pull out and eliminate virus-infected plants and the surroundings at the beginning of cultivation and before fruit set. - Perform treatments with specific insecticides against whitefly before removing plant residues from the plot. - In large growing areas, fallow period must be observed between cucurbit crops and the next to break the cycle of whiteflies. 8. PHYSIOPATHOLOGY - Burns at the apical area of cucumber: it is produced by "sunburn" or excessive perspiration. - Striped fruit: longitudinal shallow slits which are healed soon. This occurs in cold weather with sudden changes in humidity and temperature between day and night. - Curving and narrowing of the tip of the fruit: the origin of this alteration is unclear, although several factors influence: inadequate fertilizing, water deficit, salinity, variety sensitivity, thrips, high temperatures, excess production, etc. - Fruit self-thinning: it occurs when the fruit are recently set: fruits turn yellowish, shrivel and fall. It is due to an overload of fruit, water and nutrient deficits. - Yellowing of fruit: starts from the stylar scar and gradually progresses to occupy much of the fruit epicarp. The causes include: excess nitrogen, lack of light, excess potassium, very high conductivity in the soil, severe dehydration, etc. 9. HARVEST Cucumbers are harvested at various stages of development. Fruits are to be cut with scissors instead of pulling them off. The period between flowering and harvest may be 55 to 60 days, depending on cultivar and temperature. Usually, the fruits are harvested at a slightly immature state, close to its final size, but before the seeds harden and complete their growth. Firmness and external glossiness are also indicators of the desired pre-ripe state. At the appropriate state of harvest, a gelatinous material begins to form in the cavity that carries the seeds. For fresh consumption, different cucumber cultivars reach different sizes when they have reached commercial maturity. The range varies between 20 and 30cm long and 3-6cm in diameter. Fruit colour depends on cultivar; however, it should be dark green or green with no signs of yellowing. For the pickled cucumber, the fruits are shorter and the length/diameter ratio should be between 2/9 and 3/1. Its colour must be a light green hue. 10. POSTHARVEST - Quality: the quality of the fresh cucumber is mainly based on the uniformity of shape and on the firmness and dark green colour of the epicarp. Other quality indicators are the size and the lack of growth or handling defects, decay and yellowing. Specifications and quality control used by the horticultural industry adhere to the conventional nomenclature used in packing. - Optimal temperatures and relative humidity: 10-12,5°C; 95% RH. Generally, the cucumber is stored for less than 14 days as it loses quickly its visual and sensory quality. Decaying, yellowing and drying out starts after a couple of weeks, especially after the fruits are transferred to standard conditions of sale. Short term storage or transport temperatures lower than the optimal conditions, such as 7,2°C are commonly used, but this may cause chilling injury after 2 to 3 days. - Chilling injury: cucumbers are sensitive to chilling injury at temperatures below 10°C if they are kept in these conditions for more than 3 days, depending on the specific temperature and cultivar. The manifestations of chilling injury are translucent and water-soaked areas, chopped (pitting) and accelerated decay. Chilling injury is cumulative and can be started in the field before harvest. The different varieties of cucumber differ considerably in susceptibility to this physiopathology. - Rate of ethylene production: 0,1-1,0µl/kg·h at 12,5°C. - Effects of controlled atmosphere (CA): low concentrations of O2 (3-5%) delay deterioration and the beginning of rot for few days. Cucumbers tolerate up to 5% of CO2. 11. NUTRITIONAL VALUES High content of ascorbic acid and small amounts of vitamin B complex are among the important nutritional properties of cucumber. As for minerals, it is rich in calcium, chlorine, potassium and iron. The seeds are rich in vegetable oils.
Cucumbers must be selected according to the quality standards after harvest. First , they are classified by their degree of maturity; then by size, preferably 20 to 30cm long, smooth and straight cylindrical surface, dark green (no yellowing), and clean. It should be firm when it is cut and the inner ring must present higher proportion of white pulp, the seeds should not be larger than 3mm long, showing moisture inside. When it is broken manually, it should emit a slight sound of resistance. In some cases, when the market allows, the fruits are waxed in order to improve the appearance and prolong its postharvest life, as the wax reduces water loss by evaporation. Author: Infoagro
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Related imagesCucumber plant  Cucumber leaves  Cucumber leaves and tendrils  Cucumber flower  Cucumber fruit  Short cucumber. Spanish type  Long cucumber, Dutch type  Trellising of cucumber plant  Pre-sowing irrigation in cucumber crop  Mildew  Cucumber vein yellowing virus (CVYV)  Curving and narrowing of the tip of the fruit
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