Cucumber (Revised)

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Scientific Name
Cucumis sativus L.
Order / Family
Violales: Cucurbitaceae (Gourd family)
Local Names
Cucumber, gherkin (English); Concombre, Cornichon (French); Pepino (Portugease); Tango (Swahili).
Pests & Diseases:
Angular leaf spot

Angular leaf spot (Pseudomonas syringae pv. lachrymans)

Spots on leaves are angular in shape and variable in size due to leaf veins that limit their enlargement. Initially, spots are water-soaked. In moist weather, bacteria ooze from the spots in tear-like droplets, which dry making the tissue white. Affected leaf dries and shrinks, and it may tear away from the healthy portion leaving irregular holes. Leaves approaching maturity are more susceptible than older leaves. Fruits may also be attacked. Fruit spots are small, nearly circular and superficial. The bacteria survive in association with seed. When infected cucumbers are used for seed extraction, the seed can be contaminated during fermentation process.

The bacteria can also survive in soil or infected crop debris. Drainage water can spread the bacteria in the soil. Angular leaf spot disease is favoured by wet conditions, frequently associated with rainfall and overhead irrigation. Optimum temperature for disease development is 23.9 to 27.8 degC. The disease attacks gherkin, muskmelon, pumpkin, squash, vegetable marrow and watermelon.

  • Angular leaf spot on cucumber

    â’¸ A. A. Seif
What to do:
  • Use resistant varieties, if available.
  • Use certified disease-free seed.
  • Practice crop rotation. A crop rotation of 1 to 2 years is recommended.
  • Avoid run-off water from nearby cucurbit fields and overhead irrigation.
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Anthracnose

Anthracnose (Colletotrichum orbiculare)

It is a very destructive disease. It causes defoliation and lesions on the fruits. 

The fungus can attack all the above-ground plant parts. Cotyledons (seed leaves) of affected seedlings droop and wilt. Lesions (elongated spots) may form on stems of affected seedlings near the ground. Spots on leaves start as small yellowish areas that enlarge and turn brown. The affected tissue dries, breaks and the whole leaf dies. On vines, the spots are elongated and may kill the vines. Symptoms are most noticeable on fruits. Spots on fruits are circular, black, and sunken. When wet, the centres of the spots become salmon coloured due to a mass of fungal spores. Affected fruits can be destroyed by secondary soft-rot organisms, which enter through broken rind. The fungus is seed-borne. It can survive in crop debris and in weeds belonging to the cucurbit family. Fungal development is promoted by wet conditions, high relative humidity and moderate temperatures (20 to 23.9°C ). Its host range includes cucumber, gherkin, gourd, muskmelon, and watermelon. Cucurbit weeds can also be attacked.

  • Anthracnose (Colletotrichum orbiculare) damage to pumpkin leaf (Cucumis sativus).

    â’¸ Clemson University - USDA Cooperative Extension Slide Series, www.insectimages.org
What to do:
  • Use certified disease-free seeds.
  • Treat own seeds in hot water for 20 minutes at 135 °F (43°C).
  • Plant resistant varieties, if available.
  • Practise crop rotation with non-cucurbits.
  • Destroy volunteer cucurbits and weeds in the field.
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Aphids

Aphids (Aphis gossypii)

The cotton aphid (Aphis gossypii) is common on cucurbits, including cucumber. Colonies of green to blackish aphids are found on tender shoots, mainly on the lower leaf surface, where they suck sap. The growth of the attacked shoots is stunted and the leaves are curled and twisted. Aphids excrete honeydew, which leads to growth of sooty mould, and may attract fruit flies. Aphids, in particular winged aphids, transmit virus diseases (e.g. cucumber mosaic virus) when moving from plant to plant.

 

  • The cotton aphid (Aphis gossypii) is a small aphid. Adults range from just under 1-1.5 mm in body length.

    © Mississippi State University Archive, Mississippi State University, Bugwood.org
What to do:
  • Plant barrier crops.
  • Apply sticky traps.
  • Use botanicals (e.g. Neem extracts).
  • Use reflective mulch (e.g a polyethylene sheet covered with a thin layer of aluminium that is spread out on the growing bed at planting time). Covering the ground with a material like aluminium foil repels winged aphids, delay aphid colonisation and may delay virus infection.
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Damping-off diseases

Damping-off disease

Damping-off diseases are caused by a complex of plant pathogens (disease inciting agents) including Alternaria spp., Fusarium spp., Pythium spp. and Rhizoctonia solani. These pathogenic fungi may cause rotting of seeds before emergence or death of seedlings after emergence. The most disposing factors are use of non-certified seeds and excessive watering of seed-beds or field plots.

  • Damping-off disease - Phytium sp. on Cucumber

    â’¸ Gerlach W. (Courtesy of EcoPort, www.ecoport.org)
What to do:
  • Always use certified disease-free seeds.
  • Avoid overwatering of seed-beds or field plots where direct sowing is done.
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Downy mildew

Downy mildew (Pseudoperonospora cubensis)

Symptoms on leaves appear as small, pale-yellow areas on upper leaf surface. Under humid conditions, a purplish, grey whitish growth may be seen on the underside of the yellowish spots. Affected leaves curl, shrivel and die.

Most downy mildew fungi require cool weather for reproduction and development. This is not true of the cucurbit downy mildew fungus. Optimum temperature for infection is at 16 to 22°C. It can survive when temperatures are over 37.8°C. The most critical factor for infection is a film of moisture and / or long dew periods on leaves. Disease spread is primarily through wind and rain splash. The fungus attacks only members of the cucumber family, mostly those that are cultivated, although it can infect wild cucumber and a few other weed hosts.

  • Downy mildew on cabbage

    â’¸ A.M. Varela, icipe
What to do:
  • Use resistant varieties, if available.
  • Leave wide spacing between plants.
  • Avoid overlap cucumber plantings.
  • Copper fungicides at 0.1% can provide control.
,
Epilachna beetles

Epilachna beetles (Epilachna chrysomelina)

Adults of this beetle, also known as the African melon ladybird, are 6-8 mm long, reddish in colour with a number of black spots on the wing cases. The larvae are 7-9 mm in length, soft and covered with dark coloured spines. Adults and larvae feed on leaves leaving a fine net of veins. Damaged leaves shrivel and dry up. Young plants can be entirely destroyed. Older plants can tolerate considerable leaf damage. This beetle is a vector of squash mosaic virus. Epilachna beetles attack all cucurbits.

  • Larvae of Epilachna beetle and damage caused on water melon

    © A. M. Varela, icipe

  • Epilachna beetles (Epilachna spp.) larvae and pupae on eggplant. Larvae are about 6 mm long.

    © O.P. Sharma, NCIPM, New Delhi. India, Bugwood.org
What to do:
  • Spray neem extracts. Simple neem-based pesticides have given control of this pest in Togo. Thus, feeding by Epilachna beetles in squash and cucumber could be reduced significantly by weekly applications of aqueous neem kernel extracts at concentrations of 25, 50 and 100 g/l and neem oil applied with an ultra-low-volume (ULV) sprayer at 10 and 20 l/ha (Ostermann and Dreyer, 1995).
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Flea beetles

Flea beetles (Podagrica spp)

They are 1.5 to 3 mm long with well-developed hind legs. They are named for their habit of jumping like fleas when disturbed. The colour of the adult beetles varies from black, brown, black and yellow striped or metallic blue-green depending on the species. Adult flea beetles chew small round holes (shot holes) in leaves, giving them a sieve like appearance. On rare occasions, they may feed directly on ripe fruit, just below the calyx. This damage is usually seen only in plants that show extreme foliar stress resulting from lack of water or powdery mildew. The larvae of flea beetles live in the soil and feed on roots, but the damage caused is not of economic importance. Adult flea beetles can be particularly damaging to young plants. Seedlings are most vulnerable to flea beetle feeding when stressed, particularly by inadequate moisture. Older plants can withstand considerable leaf perforation.

 

  • Flea beetle Phyllotreta mashonana feeding on young okra pod.

    â’¸ A.M. Varela, icipe
What to do:
  • Monitor the crop frequently, particularly during the first stages of the crop. Even a small flea beetle population can cause significant damage to a crop in the cotyledon or first-leaf stages.
  • Provide good nutrition and favourable growing conditions. This helps to avoid plant stress from diseases and moisture, and helps plants survive flea-beetle attack.
  • Weed in and around fields. This may help to eliminate flea beetle shelter and breeding grounds, reducing crop damage.
  • Keep plant diversity in the farm. Living mulches or polycultures are known to reduce flea-beetle damage. Diversity in the farm supports populations of natural enemies.
  • When necessary spray botanicals or other alternative products. Extracts of neem, rotenone, pyrethrin, sabadilla, garlic, onion and mint alone or in combination have been recommended for control of flea beetles. Insecticidal soap is reported to give partial control of flea beetles. However, sprays combining rotenone with insecticidal soap are considered very effective. Diatomaceous earth and rock powders have been observed to reduce flea-beetle populations but applications must be renewed regularly after rainfalls.
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Fruit flies

Fruit flies (Bactrocera cucurbitae, Dacus spp and Ceratitis capitata)

Fruit flies are important pests of cucumber and other cucurbits.

 

Fruit flies are about 4-7 mm long, they pierce the fruits and lay eggs in fruits. The fruit fly maggots feed inside the fruit causing sunken, discoloured patches, distortions and open cracks. These cracks serve as entry points for fungi and bacteria, causing fruit rot.

 

  • Fruit fly maggots Fruit fly maggots in watermelon fruit, the larvae are about 1cm long

    © A.M. Varela, icipe

  • Water melon damage by fruit fly

    © A.M. Varela, icipe

  • External fruit fly damage symptoms on courgette

    © M. K. Billah, icipe

  • Internal fruit fly damage symptoms on courgette

    © M. K.Billah, icipe
What to do:
  • Avoid continuous cultivation of cucumbers at the same place since this may lead to fruit fly outbreaks.
  • Destroy all infested fruit.
  • In small plots, wrap individual fruits or bag them with newspaper or paper bags to prevent fruit flies from laying eggs into fruits. Wrapping or bagging should be started shortly after fruit set.
  • Spray with a pyrethrum solution in the evenings after the bees are mostly back in their hives (after 6 pm). There is a product commercially available called "Flower-DS", made of natural pyrethrum and acceptable in organic certified systems (see Hygrotech Company, contact-addresses below).

    - Precautions: Be careful to spray late in the evening, follow the spraying instructions. Wear masks and skin protection.

    All insect poisons are also poisonous to humans even if coming from natural sources.

    - Frequency of spraying: start shortly after beginning of flowering, and repeat every 5 days or according to counts.

  • Frequent applications of neem can keep fruit fly attack to a minimum.

    For more information on Neem click here.
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Fruit rot

Fruit rot

Fruit rots are of minor importance in Africa; they are primarily post-harvest problems during storage. In most African countries, cucumbers are sold fresh from farm, consumed and are hardly stored for long (exception could be supermarkets in urban areas where fruits are kept on shelves).

 

  • Choanephora fruit rot (Choanephora cucurbitarum) on pumpkin

    â’¸ Clemson University - USDA Cooperative Extension Slide Series, www.insectimages.org
What to do:
  • Avoid injuries during harvesting
  • Store fruits properly after harvest
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Fusarium wilt

Fusarium wilt

The lower leaves of the plant usually turn yellow and die. One or more branches may exhibit such symptoms. Leaflets on one side may be affected while those on the other side are symptomless. Diseased leaves readily break away from the stem. When affected stems just above ground level and petioles are cut diagonally, a reddish-brown discolouration of the water conducting tissues will be observed. The fungus is both seed- and soil-borne. It causes most damage on light, sandy soils. It is most active at temperatures between 25 and 320C. The fungus can survive in the soil indefinitely even when no tomatoes are grown. It can also survive in fibrous roots of weeds (e.g. Amaranthus, Digitaria and Malva species). Acidic soils (pH 5.0 to 5.6) and excessive nitrogen fertilisation promote disease development. Infestation by root-knot nematodes encourages the disease.

  • Wilting of okra plant due to fusarium wilt

    © A.M. Varela & A.A.Seif, icipe
What to do:
  • Use resistant varieties, if available.
  • Use certified disease-free seeds.
  • Avoid spread of the fungus through contaminated farm implements and furrow irrigated water.
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Root-knot nematodes

Root-knot nematodes (Meloidogyne spp.)

Symptoms of infestation by root-knot nematodes are similar in all crops: wilting of plants and if infested plants are pulled from the soil the roots can be seen to be distorted, swollen and bearing knots. The infested roots eventually rot and affected plants die.

 

  • Root-knot nematodes (Meloidogyne incognita / M. javanica) Roots of severely attacked (left) and healthy plant (right). Affected plants are normally stunted and eventually wilt and die. The most characteristic symptom is formation of root galls (knots) and these can be seen with the naked eye. Affected roots rot.

    © A. M. Varela, icipe
What to do:
  • Use resistant varieties, if available.
  • Practise mixed cropping. Mixed cropping with African marigold (Tagetes spp.) minimises root-knot nematode damage. Intercrop with different mustards (e.g. Brassica juncea var. integrifolia or Brassica juncea var. juncea) on infested fields. As soon as mustards are flowering they are mulched and incorporated into the soil. While incorporated plant parts are decomposing in a moist soil, nematicidal compounds of this decomposing process kill nematodes. Two weeks after incorporating plant material into the soil a new crop can be planted or sown (phytotoxic effects are usual if the crop is planted before two weeks).
  • Maintain high levels of organic matter in the soil (manure or compost).
  • Use biofumigation where possible (biofumigation involves incorporation into the soil of crop residues of crucifers, resulting in high levels of organic matter).
  • Use Neem extracts.
,
Scab

Scab (Cladosporium cucumerinum)

It attacks all aboveground plant parts. Initial symptoms on leaves appear as light water-soaked or pale green spots. The spots are numerous and can appear on and between veins. Elongate spots may develop on petioles and stems. The spots later turn grey to white and become angular. The fine veinlets in the spots may be brown and are distinct against a white background. Dead leaf tissue cracks and breaks away until the whole leaf is ragged. Fruits can be attacked at all stages of growth. However, young fruits are most susceptible. Plant tissue near the spots may produce sap, initially watery but later becomes gummy to hard.

The fruit spots are cankerous and with time become darker, sunken until a pronounced cavity is formed. Under moist weather, a dark-green velvety layer of fungal growth appears on the cavities. The fungus survives in crop debris, soil and on seed. It is spread by insects, farm tools and wind. The disease is most severe at 100% relative humidity and at relatively cool temperatures (21-25°C). Its host range includes cantaloupe, gherkin, muskmelon, pumpkin, squash and watermelon.

 
What to do:
  • Use resistant varieties, if available.
  • Use certified disease-free seeds.
  • Practise crop rotation with nonrelated crops.
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Spider mites

Red spider mites (Tetranychus spp.)

Red spider mites attack leaves of cucumber. Adults are about 0.6 mm long. Attacked leaves have a stippled appearance, turn yellowish to whitish and dry up. Often young plants are entirely destroyed. In older plants growth can be severely stunted and the fruit set considerable reduced. Spider mites can be a problem in dry and hot conditions. Plants under water stress (drought) are more likely to suffer damage by spider mites.

  • Spider mites on tomato. Note the mites and their webbing visible beetween the leaves.

    â’¸ Clemson University - USDA Cooperative Extension Slide Series, Bugwood.org

  • A related Spider mites species on cotton leaf. They are very tiny (they rarely exceed a size of 0.5 mm)

    © O.P. Sharma, NCIPM, New Delhi. India, Bugwood.org
What to do:
  • Conserve natural enemies. Predatory mites and anthocorid bugs are important in natural control of mites.
  • Avoid use of broad-spectrum pesticides. They may kill natural enemies and may lead to mite outbreaks.
  • Provide good growing conditions for plants. Healthy plants are more likely to withstand mite attack. Adequate irrigation is particularly important. Apply mulch and incorporate organic matter into the soil to improve the water holding capacity and reduce evaporation.
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Virus diseases

Mosaic Virus diseases

Cucumber mosaic virus

It is not seed transmitted except through seed of perennial wild cucumber (Echinocytis lobata) and chickweed (Stellaria media). It is mechanically transmitted and in nature it is spread by various species of aphids. It has a very extensive host range including such varied species as bananas, carrots, cowpeas, lupine, lilies, onions, passion fruit, potatoes and tomatoes.

 

Watermelon mosaic virus

This virus is mechanically transmitted and also spread by several species of aphids. It is not seed transmitted. Its host range is primarily restricted to cucurbits although one of its strains infects peas.

 

Squash mosaic virus

It is mechanically transmitted. It is transmitted through seeds of melons and squash. It is also transmitted by spotted, striped and banded cucumber beetles, which attack cucumbers in the Americas. The Epilachna beetle (Epilachna chrysomelina) a pest of cucumber in Africa, is also vector of squash mosaic virus. Its host range includes cucurbits, peas, coriander, and salad chervil.

 

  • Virus on cucumber

    © A.A. Seif, icipe

  • Mosaic virus on water melon leaf

    © A.M. Varela, icipe
What to do:
  • Use tolerant / resistant varieties if available.
  • Remove infected plants (disinfect hands and tools with 70% alcohol after contact with infected plants).
  • Do proper weeding.
  • Control insect vectors. A sustainable approach of controlling aphids is important to prevent aphids reaching the crops and transmitting virus.
  • In case of squash mosaic virus use certified disease-free seeds.
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Whiteflies

Whiteflies (Bemisia tabaci)

They suck plant sap and excrete honeydew where moulds grow, which may affect plant growth and vigour. The tobacco whitefly is considered a major pest due to its ability to vector various virus diseases, which cause considerable damage to cucurbits.

 

  • Adults and eggs of the cabbage whitefly (Aleyrodes proletella)

    © A. M. Varela, icipe
What to do:
  • Conserve natural enemies. Parasitic wasps are important in natural control of whiteflies
  • Use reflective mulches (see aphids). Reflective mulch repels whitefly adults in pumpkin, cucumber and zucchini squash, resulting in delayed and reduced attack by this pest with consequent reduction in damage as shown in experiments in USA. Whitefly density on pumpkins and cucumbers plants growing over reflective mulch was reduced 10- to 14-fold as compared to plants growing on bare soil. This was reflected in significantly higher yields in plants grown over reflective mulch than in those grown over unmulched soil. (UCANR, 2003; Summers & Stapleton 2002)
  • Whenever necessary spray the crop with neem products. Neem-based pesticides are reported to inhibit growth and development of immature stages, and to reduce egg laying by adult whiteflies
Other pests: Leafminer, Powdery mildew

Geographical Distribution in Africa

Geographical Distribution of Cucumber in Africa. Updated on 8 July 2019. Source FAOSTAT
© OpenStreetMap contributors, © OpenMapTiles, GBIF.
The cucumber is native to the region around the Himalayas south to Bangladesh and Thailand but is now grown worldwide.

Other Local names

Angola: Nungo (Kimbundu), Pepino (Portuguese)
Morocco: Khiyar (Arabic); Concombre (French)
 

 

General Information and Agronomic Aspects

Introduction

Cucumis sativus, commonly known as cucumber, is a widely cultivated plant belonging to the genus Cucumis and the family Cucurbitaceae. This family includes other important plants such as pumpkins, squash, gourds and zucchini. Cucumis is a diverse genus, comprising around 95 known species.
Cucumber is native to South Asia but is now cultivated worldwide. It is a warm-season annual vine that thrives in temperate and tropical regions. Cucumber plants have sprawling vines with large leaves and produce cylindrical fruits that can vary in size, shape, and color, depending on the variety. They are typically grown in gardens, greenhouses, and commercial farms.
Cucumber is mainly grown for the immature fruits, which are consumed fresh (slicing cucumber) in salads, sandwiches or used for pickles (pickling cucumber). The slicing cucumbers are peeled, sliced and served with vinegar or dressing, or as an ingredient of salads. The large, yellow, round types are boiled and eaten as an ingredient of stews. Pickling cucumbers are preserved or marinated with vinegar, salt, or spices.

Long type cucumber in Nairobi market, Kenya. â’¸ Foods of the Nairobi people, 2005
Long type cucumber in Nairobi market, Kenya.
â’¸ Foods of the Nairobi people, 2005

Cucumbers are a good source of vitamin C. Cucumber's mild and refreshing flavour makes it a popular ingredient in various cuisines around the world, including Mediterranean, Asian, and Middle Eastern dishes. In many tropical African countries, cucumbers are considered exotic or Western vegetables. Southern African states however have their specific large type common in markets and used in local food preparations. They are primarily used by urban consumers. Cucumbers are low in calories and rich in water content, making them a hydrating and refreshing food choice. They are a good source of vitamins, including vitamin K and vitamin C, as well as minerals like potassium and magnesium. Cucumbers also contain antioxidants and phytonutrients that have been associated with potential health benefits, such as reducing inflammation and supporting digestion. They are also a good source of dietary fiber, which aids in digestion and promotes a healthy gut. The skin of cucumbers contains additional nutrients, so it is recommended to consume them with the peel whenever possible.
Ripe raw cucumber fruits are believed to have curative properties for sprue, and in Indo-China, cooked immature fruits are used to treat dysentery in children. The cucumber seeds have anthelmintic properties. Cucumber extract is known for its cleansing, soothing, and softening effects on the skin, making it a popular ingredient in various health and beauty products. Non-food uses of cucumber are not widespread in Africa.
(Van Luijk, M.N., 2004, Khan, A., et al., 2021, Maundu et al., 2007).

Species account

Cucumis sativus (cucumber) is an herbaceous, annual plant (surviving only one growing season) that typically grows in a trailing or climbing manner, with curling tendrils for support. Leaves: palmate and alternate in arrangement, deeply lobed with three to five lobes and have a rough texture. Leaves are typically green in color and have a rough surface due to small prickles. Flowers: produce both male and female flowers, usually yellow in color. Male flowers appear in clusters, while the female flowers are solitary and distinguishable by the presence of a small ovary at the base. Flowers are insect-pollinated and produce nectar to attract pollinators. Fruit: vary in size, shape, color and texture but is generally a curved cylindrical or elongated, although some varieties can be round or oval. The skin range from smooth to bumpy, and the color may vary from dark green to light green or even yellow. Some cultivars have a striped or mottled pattern on the skin. The flesh of the cucumber is crisp and juicy, containing numerous seeds. Seeds :ovate-oblong, compressed, white, smooth. Seedling with epigeal germination.

(Van Luijk, M.N., 2004. plantvillage.psu.edu)

Rough Cucumber in Nairobi market, Kenya â’¸ Foods of the Nairobi people, 2005
Rough Cucumber in Nairobi market, Kenya
â’¸ Foods of the Nairobi people, 2005

 

Long type cucumber in Nairobi market, Kenya. â’¸ Foods of the Nairobi people, 2005
Long type cucumber in Nairobi market, Kenya.
â’¸ Foods of the Nairobi people, 2005

Short cucumber in Nairobi market, Kenya. â’¸ Foods of the Nairobi people, 2005
Short cucumber in Nairobi market, Kenya.
â’¸ Foods of the Nairobi people, 2005

Varieties.
The species Cucumis sativus displays significant variation, which has led to the development of numerous cultivars with different characteristics. Variations in fruit size, shape, color, taste, and disease resistance have been selected and bred by growers to meet specific consumer preferences and market demands. This variability within the species allows for a wide range of cucumber types to be grown and enjoyed worldwide.

Cucumber varieties are categorized into four types on basis of fruit length: 
•    Long cucumbers: Fruit length over 30 cm. Examples: "Berlin RZ", "Bologna RZ", "Cumlande RZ", "Myrthos RZ", "Pluto RZ" "Virginia RZ")
•    Midi cucumbers: Fruit length between 18 -24 cm Examples: "Media RZ
•    "Mini cucumbers: Fruit length between 15 -19 cm. Examples: "Khassib RZ", "Gianco RZ
•    "Cocktail cucumbers: Less than 15 cm. Examples: "Rania RZ"
 
Other varieties include:
•    "Ashley" It takes about 65 days to maturity. Fruit colour is dark green. Fruit shape is long and spined. It has some resistance to downy mildew.
•    "Danora F1 Hybrid". It is a long cucumber. It tales about 65 days to maturity. Fruit colour is green. Fruit is elongated. It has good resistance to powdery mildew and leaf spot.
•    "Palomar". It takes about about 60 days to maturity. Fruit is dark green. Fruit is long and cylindrical. It has good tolerance to leaf diseases. It is good for pickling.
•    "Poinsett". Poinsett is a variety with a very high yield potential, good disease and heat resistance
•    ."Sarig". It is dark green in colour. Fruit length of 14-16 cm. It is very smooth and of high quality. It has a long shelf life. It is resistant to powdery mildew. It is suitable for green house production.
•    "Super Marketer". Maturity period is 45 to 60 days. It grows well in hot climatic conditions. Its very high yielding about 16-32 t/ha. It is very popular in the local market.
•    "Tempo" ("HA 78"). It is dark green in colour. The average fruit length is 30-35 cm. It has a good shelf life of up to 2 weeks. It is resistant to powdery mildew.
•    "Toaz". It has a very vigorous growth. Fruit is dark green in colour. Fruit length is 16-18 cm. It is smooth and has a good shelf life, It is suitable for green house production.
•    "Long Fellow"
•    "Hybrid Victory"
•    "Kande" (new variety produced in Tanzania)
Because varieties change all the time, please ask your local seed company to give information about the available varieties.

Cucumber. © Biovision.

Marketable cucumbers: The two long varieties are greenhouse types that need protected environment and careful staking so as not to damage fruits. The two short types on the right can be grown in open fields and without staking. Pickling varieties are even smaller, but also baby fruits of the two field varieties are good for pickling. 

Ecological conditions 
Cucumber requires a warm climate. The optimum temperature for growth is about 30degC and the optimum night temperature 18-21degC. In the tropics, elevations up to 1700 m appear to be suitable for cucumber cultivation. A lot of light tends to increase the number of staminate (male) flowers. Cucumbers need a fair amount of water but they cannot stand waterlogging. High relative humidity encourages downy mildew. The soil should preferably be fertile and well-drained, with a pH of 6.5-7.5. Long and medium long slicing cucumber varieties are grown in greenhouses where climate and other growing conditions can be controlled. 

Agronomic aspects 

Cucumber is propagated by seed. Soil preparation requires generous incorporation of well-rotted manure. About 30 t/ha or 15 tons/ha should be applied inside the planting holes together with a spoonful of rock phosphate (3 tea spoons) for each planting hole. Sowing is done directly in the field with several seeds per hill, 90-120 cm apart, then thinned to 2-3 plants per hill, or seeds are sown in nursery beds and seedlings transplanted to the field at the 2-true-leaf stage at 30-40 cm within and 1-2 m between the rows. Sowing rates per ha are about 2.5-3 kg for direct seeding and 1 kg when transplanted. Cucumber cultivated for pickles is planted closer, up to 250,000 plants/ha. For greenhouse varieties plants are started in individual pots and transplanted to permanent position when they have 2-3 permanent leaves. 

Husbandry
Weed control is necessary until the plants cover the soil entirely. Support (stakes) should be provided for some cultivars, and the tip of the main stem can be nipped off to encourage branching. Irrigate at frequent intervals, and maintain a high level of soil moisture throughout the growing period. Lateral shoots can be pruned after the first fruits have formed to limit leaf and flower production. Greenhouse varieties are staked according to preferred practices, usually by means of twisting the growing stem around a string attached to an overhead strong wire. There are indications that irrigation water containing applications of effective micro-organisms (EM) can prevent damping off and early attacks of diseases on leaves.
Irrigation should preferably be applied in the form of drip in order to prevent water splashes and spread of diseases. Staked cucumbers are very susceptible to wind, so if grown in open land should be carefully protected from wind.

Harvest, post-harvest practices and markets 

Harvest
Cucumbers for fresh consumption are harvested before they are fully mature, usually starting about 50- 60 days after planting, and thereafter every few days. Mature fruits are yellow and the flesh is often tough with woody seeds. For pickling, immature fruits of several stages are harvested. Only for seed production are cucumbers allowed to mature on the plant.

Post-harvest practices
Cucumbers should be handled with care as they get damaged easily during transport. Depending on variety one plant may yield up to 10 fruits, and total yields with good plant care can easily reach 50 tons/ ha of the larger fruit types. More common yields are 25-30 tonnes/ha. Fruits should not be left to ripen on the vines as the plants will cease to bear. The marketed fruit must be firm, green and the size typical of the cultivar. 
Some of the long slicing cultivars of cucumber are packed individually before marketing and cooled.

Value addition and markets

Common cucumber value addition methods include pickling, juicing, and using cucumber extracts in skincare products. Pickling cucumbers in vinegar or brine extends their shelf life and creates a tangy snack or side dish. Juicing or blending cucumbers into smoothies adds a refreshing and nutritious element to beverages. 
Cucumbers are globally popular vegetables, top cucumber producers include China, Turkey, Iran, Russia, and the United States. These countries have substantial cucumber cultivation and supply to both domestic and international markets. The United States, European Union, Japan, and Southeast Asian countries are significant cucumber markets.
In Africa, cucumber cultivation is widespread, primarily for domestic consumption and local markets. Countries such as Nigeria, Egypt, South Africa, Kenya, and Morocco are notable cucumber producers. Cucumbers form an essential part of African diets and are used in various traditional dishes and salads. However, the export of cucumbers from Africa is relatively limited compared to major global producers. In recent years, there has been an increasing demand for fresh and organic produce globally, including cucumbers. Consumers are seeking healthier food choices, driving the popularity of cucumbers in salads and healthy beverages. Additionally, the rising trend of natural skincare products has boosted the demand for cucumber extracts in the cosmetic industry.
(Van Luijk, M.N., 2004. tridge.com)

Nutritional value and recipes

Cucumbers offer a versatile culinary diversity, making them a popular ingredient in various cuisines around the world. They can be enjoyed raw in salads, sandwiches, or as a refreshing side dish. In Mediterranean cuisine, cucumbers are often combined with yogurt to create tzatziki, a cooling sauce or dip. In East Asian cuisine, they are pickled or added to sushi rolls. Additionally, cucumbers can be juiced or blended into smoothies for a refreshing beverage. 
Cucumbers are low in calories but high in vitamin C. Cucumbers are primarily composed of water, accounting for about 95% of their weight. This high water content helps to keep the body hydrated, especially during hot summer months. They also contain a variety of essential vitamins and minerals, including vitamin K, vitamin C, potassium, and magnesium, though in small quantities compared to green leafy vegetables. Cucumbers also contain antioxidants, including flavonoids and tannins, which prevent the accumulation of harmful free radicals and may reduce the risk of chronic disease.
One of the notable benefits of cucumbers is their potential to aid in weight management. Due to their low calorie and high water content, cucumbers are a filling snack that can help satisfy hunger cravings without adding excessive calories 
(healthline.com, webmd.com/)

Approximate nutritional value for 100g of Cucumber, green, unpeeled, raw

Proximate composition and dietary energy

Cucumber, green, unpeeled, raw

Recommended daily allowance (approx.) for adultsa

Edible conversion factor

0.97

 

Energy (kJ)

47

9623

Energy (kcal)

11

2,300

Water (g)

96.2

2000-3000c

Protein (g)

0.6

50

Fat (g)

0.1

<30(male), <20 (female)b

Carbohydrate available (g)

1.3

225 -325g

Fibre (g)

1.4

30d

Ash (g)

0.5

 

Mineral composition

 

 

Ca (mg)

20

800

Fe (mg)

0.7

14

Mg (mg)

14

300

P (mg)

20

800

K (mg)

136

4,700f

Na (mg)

22

<2300e

Zn (mg)

0.18

15

Se (mcg)

1

60

Bioactive compound composition

 

 

Vit A RAE (mcg)

0

800

Vit A RE (mcg)

1

800

Retinol (mcg)

0

1000

b-carotene equivalent (mcg)

5

600 – 1500g

Thiamin (mg)

0.03

1.4

Riboflavin (mg)

0.02

1.6

Niacin (mg)

0.20

18

Dietary Folate Eq.(mcg)

7

400

Vit B12 (mcg)

0

3

Vit C (mg)

7

60

Source (Nutrient data): FAO/Government of Kenya. 2018. Kenya Food Composition Tables. Nairobi, 254 pp. http://www.fao.org/3/I9120EN/i9120en.pdf

RE=retinol equivalents.

RAE =Retinol activity equivalents. A RAE is defined as 1μg all-trans-retinol, 12μg beta-carotene, or 24μg α-carotene or β-cryptoxanthin.

a Lewis, J. 2019. Codex nutrient reference values. Rome. FAO and WHO

b NHS (refers to saturated fat)

c https://www.hsph.harvard.edu/nutritionsource/water/

d British Heart Foundation

e FDA

f NIH

g Mayo Clinic

 

 

 

Aphids (Aphis gossypii)

The cotton aphid (Aphis gossypii) is common on cucurbits, including cucumber. Colonies of green to blackish aphids are found on tender shoots, mainly on the lower leaf surface, where they suck sap. The growth of the attacked shoots is stunted and the leaves are curled and twisted. Aphids excrete honeydew, which leads to growth of sooty mould, and may attract fruit flies. Aphids, in particular winged aphids, transmit virus diseases (e.g. cucumber mosaic virus) when moving from plant to plant.

 

What to do:
  • Plant barrier crops.
  • Apply sticky traps.
  • Use botanicals (e.g. Neem extracts).
  • Use reflective mulch (e.g a polyethylene sheet covered with a thin layer of aluminium that is spread out on the growing bed at planting time). Covering the ground with a material like aluminium foil repels winged aphids, delay aphid colonisation and may delay virus infection.

  • The cotton aphid (Aphis gossypii) is a small aphid. Adults range from just under 1-1.5 mm in body length.

    © Mississippi State University Archive, Mississippi State University, Bugwood.org

  • The cotton aphid (Aphis gossypii) is a small aphid. Adults range from just under 1-1.5 mm in body length.

    © Mississippi State University Archive, Mississippi State University, Bugwood.org

Fruit flies (Bactrocera cucurbitae, Dacus spp and Ceratitis capitata)

Fruit flies are important pests of cucumber and other cucurbits.

 

Fruit flies are about 4-7 mm long, they pierce the fruits and lay eggs in fruits. The fruit fly maggots feed inside the fruit causing sunken, discoloured patches, distortions and open cracks. These cracks serve as entry points for fungi and bacteria, causing fruit rot.

 

What to do:
  • Avoid continuous cultivation of cucumbers at the same place since this may lead to fruit fly outbreaks.
  • Destroy all infested fruit.
  • In small plots, wrap individual fruits or bag them with newspaper or paper bags to prevent fruit flies from laying eggs into fruits. Wrapping or bagging should be started shortly after fruit set.
  • Spray with a pyrethrum solution in the evenings after the bees are mostly back in their hives (after 6 pm). There is a product commercially available called "Flower-DS", made of natural pyrethrum and acceptable in organic certified systems (see Hygrotech Company, contact-addresses below).

    - Precautions: Be careful to spray late in the evening, follow the spraying instructions. Wear masks and skin protection.

    All insect poisons are also poisonous to humans even if coming from natural sources.

    - Frequency of spraying: start shortly after beginning of flowering, and repeat every 5 days or according to counts.

  • Frequent applications of neem can keep fruit fly attack to a minimum.

    For more information on Neem click here.

  • Fruit fly maggots Fruit fly maggots in watermelon fruit, the larvae are about 1cm long

    © A.M. Varela, icipe

  • Water melon damage by fruit fly

    © A.M. Varela, icipe

  • External fruit fly damage symptoms on courgette

    © M. K. Billah, icipe

  • Internal fruit fly damage symptoms on courgette

    © M. K.Billah, icipe

  • Fruit fly maggots Fruit fly maggots in watermelon fruit, the larvae are about 1cm long

    © A.M. Varela, icipe

  • Water melon damage by fruit fly

    © A.M. Varela, icipe

  • External fruit fly damage symptoms on courgette

    © M. K. Billah, icipe

  • Internal fruit fly damage symptoms on courgette

    © M. K.Billah, icipe

Whiteflies (Bemisia tabaci)

They suck plant sap and excrete honeydew where moulds grow, which may affect plant growth and vigour. The tobacco whitefly is considered a major pest due to its ability to vector various virus diseases, which cause considerable damage to cucurbits.

 

What to do:
  • Conserve natural enemies. Parasitic wasps are important in natural control of whiteflies
  • Use reflective mulches (see aphids). Reflective mulch repels whitefly adults in pumpkin, cucumber and zucchini squash, resulting in delayed and reduced attack by this pest with consequent reduction in damage as shown in experiments in USA. Whitefly density on pumpkins and cucumbers plants growing over reflective mulch was reduced 10- to 14-fold as compared to plants growing on bare soil. This was reflected in significantly higher yields in plants grown over reflective mulch than in those grown over unmulched soil. (UCANR, 2003; Summers & Stapleton 2002)
  • Whenever necessary spray the crop with neem products. Neem-based pesticides are reported to inhibit growth and development of immature stages, and to reduce egg laying by adult whiteflies

  • Adults and eggs of the cabbage whitefly (Aleyrodes proletella)

    © A. M. Varela, icipe

  • Adults and eggs of the cabbage whitefly (Aleyrodes proletella)

    © A. M. Varela, icipe

Epilachna beetles (Epilachna chrysomelina)

Adults of this beetle, also known as the African melon ladybird, are 6-8 mm long, reddish in colour with a number of black spots on the wing cases. The larvae are 7-9 mm in length, soft and covered with dark coloured spines. Adults and larvae feed on leaves leaving a fine net of veins. Damaged leaves shrivel and dry up. Young plants can be entirely destroyed. Older plants can tolerate considerable leaf damage. This beetle is a vector of squash mosaic virus. Epilachna beetles attack all cucurbits.

What to do:
  • Spray neem extracts. Simple neem-based pesticides have given control of this pest in Togo. Thus, feeding by Epilachna beetles in squash and cucumber could be reduced significantly by weekly applications of aqueous neem kernel extracts at concentrations of 25, 50 and 100 g/l and neem oil applied with an ultra-low-volume (ULV) sprayer at 10 and 20 l/ha (Ostermann and Dreyer, 1995).

  • Larvae of Epilachna beetle and damage caused on water melon

    © A. M. Varela, icipe

  • Epilachna beetles (Epilachna spp.) larvae and pupae on eggplant. Larvae are about 6 mm long.

    © O.P. Sharma, NCIPM, New Delhi. India, Bugwood.org

  • Larvae of Epilachna beetle and damage caused on water melon

    © A. M. Varela, icipe

  • Epilachna beetles (Epilachna spp.) larvae and pupae on eggplant. Larvae are about 6 mm long.

    © O.P. Sharma, NCIPM, New Delhi. India, Bugwood.org

Flea beetles (Podagrica spp)

They are 1.5 to 3 mm long with well-developed hind legs. They are named for their habit of jumping like fleas when disturbed. The colour of the adult beetles varies from black, brown, black and yellow striped or metallic blue-green depending on the species. Adult flea beetles chew small round holes (shot holes) in leaves, giving them a sieve like appearance. On rare occasions, they may feed directly on ripe fruit, just below the calyx. This damage is usually seen only in plants that show extreme foliar stress resulting from lack of water or powdery mildew. The larvae of flea beetles live in the soil and feed on roots, but the damage caused is not of economic importance. Adult flea beetles can be particularly damaging to young plants. Seedlings are most vulnerable to flea beetle feeding when stressed, particularly by inadequate moisture. Older plants can withstand considerable leaf perforation.

 

What to do:
  • Monitor the crop frequently, particularly during the first stages of the crop. Even a small flea beetle population can cause significant damage to a crop in the cotyledon or first-leaf stages.
  • Provide good nutrition and favourable growing conditions. This helps to avoid plant stress from diseases and moisture, and helps plants survive flea-beetle attack.
  • Weed in and around fields. This may help to eliminate flea beetle shelter and breeding grounds, reducing crop damage.
  • Keep plant diversity in the farm. Living mulches or polycultures are known to reduce flea-beetle damage. Diversity in the farm supports populations of natural enemies.
  • When necessary spray botanicals or other alternative products. Extracts of neem, rotenone, pyrethrin, sabadilla, garlic, onion and mint alone or in combination have been recommended for control of flea beetles. Insecticidal soap is reported to give partial control of flea beetles. However, sprays combining rotenone with insecticidal soap are considered very effective. Diatomaceous earth and rock powders have been observed to reduce flea-beetle populations but applications must be renewed regularly after rainfalls.

  • Flea beetle Phyllotreta mashonana feeding on young okra pod.

    â’¸ A.M. Varela, icipe

  • Flea beetle Phyllotreta mashonana feeding on young okra pod.

    â’¸ A.M. Varela, icipe

Red spider mites (Tetranychus spp.)

Red spider mites attack leaves of cucumber. Adults are about 0.6 mm long. Attacked leaves have a stippled appearance, turn yellowish to whitish and dry up. Often young plants are entirely destroyed. In older plants growth can be severely stunted and the fruit set considerable reduced. Spider mites can be a problem in dry and hot conditions. Plants under water stress (drought) are more likely to suffer damage by spider mites.

What to do:
  • Conserve natural enemies. Predatory mites and anthocorid bugs are important in natural control of mites.
  • Avoid use of broad-spectrum pesticides. They may kill natural enemies and may lead to mite outbreaks.
  • Provide good growing conditions for plants. Healthy plants are more likely to withstand mite attack. Adequate irrigation is particularly important. Apply mulch and incorporate organic matter into the soil to improve the water holding capacity and reduce evaporation.

  • Spider mites on tomato. Note the mites and their webbing visible beetween the leaves.

    â’¸ Clemson University - USDA Cooperative Extension Slide Series, Bugwood.org

  • A related Spider mites species on cotton leaf. They are very tiny (they rarely exceed a size of 0.5 mm)

    © O.P. Sharma, NCIPM, New Delhi. India, Bugwood.org

  • Spider mites on tomato. Note the mites and their webbing visible beetween the leaves.

    â’¸ Clemson University - USDA Cooperative Extension Slide Series, Bugwood.org

  • A related Spider mites species on cotton leaf. They are very tiny (they rarely exceed a size of 0.5 mm)

    © O.P. Sharma, NCIPM, New Delhi. India, Bugwood.org

Root-knot nematodes (Meloidogyne spp.)

Symptoms of infestation by root-knot nematodes are similar in all crops: wilting of plants and if infested plants are pulled from the soil the roots can be seen to be distorted, swollen and bearing knots. The infested roots eventually rot and affected plants die.

 

What to do:
  • Use resistant varieties, if available.
  • Practise mixed cropping. Mixed cropping with African marigold (Tagetes spp.) minimises root-knot nematode damage. Intercrop with different mustards (e.g. Brassica juncea var. integrifolia or Brassica juncea var. juncea) on infested fields. As soon as mustards are flowering they are mulched and incorporated into the soil. While incorporated plant parts are decomposing in a moist soil, nematicidal compounds of this decomposing process kill nematodes. Two weeks after incorporating plant material into the soil a new crop can be planted or sown (phytotoxic effects are usual if the crop is planted before two weeks).
  • Maintain high levels of organic matter in the soil (manure or compost).
  • Use biofumigation where possible (biofumigation involves incorporation into the soil of crop residues of crucifers, resulting in high levels of organic matter).
  • Use Neem extracts.

  • Root-knot nematodes (Meloidogyne incognita / M. javanica) Roots of severely attacked (left) and healthy plant (right). Affected plants are normally stunted and eventually wilt and die. The most characteristic symptom is formation of root galls (knots) and these can be seen with the naked eye. Affected roots rot.

    © A. M. Varela, icipe

  • Root-knot nematodes (Meloidogyne incognita / M. javanica) Roots of severely attacked (left) and healthy plant (right). Affected plants are normally stunted and eventually wilt and die. The most characteristic symptom is formation of root galls (knots) and these can be seen with the naked eye. Affected roots rot.

    © A. M. Varela, icipe

Information on Diseases

General Information

Many viruses affect the cucumber family. The important viruses include cucumber mosaic virus, watermelon mosaic virus and squash mosaic virus. Field symptoms of these three diseases are similar and therefore it is very difficult to separate them by symptoms alone. Leaf symptoms include a prominent light and green mosaic pattern, mottling (yellow with green islands or blisters), and in severe cases, leaf distortion whereby affected leaves appear fern-like. Diseased fruits are malformed (slightly to severely misshaped with wart-like lumps).

Examples of Cucumber Diseases and Organic Control Methods

Damping-off disease

Damping-off diseases are caused by a complex of plant pathogens (disease inciting agents) including Alternaria spp., Fusarium spp., Pythium spp. and Rhizoctonia solani. These pathogenic fungi may cause rotting of seeds before emergence or death of seedlings after emergence. The most disposing factors are use of non-certified seeds and excessive watering of seed-beds or field plots.

What to do:
  • Always use certified disease-free seeds.
  • Avoid overwatering of seed-beds or field plots where direct sowing is done.

  • Damping-off disease - Phytium sp. on Cucumber

    â’¸ Gerlach W. (Courtesy of EcoPort, www.ecoport.org)

  • Damping-off disease - Phytium sp. on Cucumber

    â’¸ Gerlach W. (Courtesy of EcoPort, www.ecoport.org)

Downy mildew (Pseudoperonospora cubensis)

Symptoms on leaves appear as small, pale-yellow areas on upper leaf surface. Under humid conditions, a purplish, grey whitish growth may be seen on the underside of the yellowish spots. Affected leaves curl, shrivel and die.

Most downy mildew fungi require cool weather for reproduction and development. This is not true of the cucurbit downy mildew fungus. Optimum temperature for infection is at 16 to 22°C. It can survive when temperatures are over 37.8°C. The most critical factor for infection is a film of moisture and / or long dew periods on leaves. Disease spread is primarily through wind and rain splash. The fungus attacks only members of the cucumber family, mostly those that are cultivated, although it can infect wild cucumber and a few other weed hosts.

What to do:
  • Use resistant varieties, if available.
  • Leave wide spacing between plants.
  • Avoid overlap cucumber plantings.
  • Copper fungicides at 0.1% can provide control.

  • Downy mildew on cabbage

    â’¸ A.M. Varela, icipe

  • Downy mildew on cabbage

    â’¸ A.M. Varela, icipe

Angular leaf spot (Pseudomonas syringae pv. lachrymans)

Spots on leaves are angular in shape and variable in size due to leaf veins that limit their enlargement. Initially, spots are water-soaked. In moist weather, bacteria ooze from the spots in tear-like droplets, which dry making the tissue white. Affected leaf dries and shrinks, and it may tear away from the healthy portion leaving irregular holes. Leaves approaching maturity are more susceptible than older leaves. Fruits may also be attacked. Fruit spots are small, nearly circular and superficial. The bacteria survive in association with seed. When infected cucumbers are used for seed extraction, the seed can be contaminated during fermentation process.

The bacteria can also survive in soil or infected crop debris. Drainage water can spread the bacteria in the soil. Angular leaf spot disease is favoured by wet conditions, frequently associated with rainfall and overhead irrigation. Optimum temperature for disease development is 23.9 to 27.8 degC. The disease attacks gherkin, muskmelon, pumpkin, squash, vegetable marrow and watermelon.

What to do:
  • Use resistant varieties, if available.
  • Use certified disease-free seed.
  • Practice crop rotation. A crop rotation of 1 to 2 years is recommended.
  • Avoid run-off water from nearby cucurbit fields and overhead irrigation.

  • Angular leaf spot on cucumber

    â’¸ A. A. Seif

  • Angular leaf spot on cucumber

    â’¸ A. A. Seif

Anthracnose (Colletotrichum orbiculare)

It is a very destructive disease. It causes defoliation and lesions on the fruits. 

The fungus can attack all the above-ground plant parts. Cotyledons (seed leaves) of affected seedlings droop and wilt. Lesions (elongated spots) may form on stems of affected seedlings near the ground. Spots on leaves start as small yellowish areas that enlarge and turn brown. The affected tissue dries, breaks and the whole leaf dies. On vines, the spots are elongated and may kill the vines. Symptoms are most noticeable on fruits. Spots on fruits are circular, black, and sunken. When wet, the centres of the spots become salmon coloured due to a mass of fungal spores. Affected fruits can be destroyed by secondary soft-rot organisms, which enter through broken rind. The fungus is seed-borne. It can survive in crop debris and in weeds belonging to the cucurbit family. Fungal development is promoted by wet conditions, high relative humidity and moderate temperatures (20 to 23.9°C ). Its host range includes cucumber, gherkin, gourd, muskmelon, and watermelon. Cucurbit weeds can also be attacked.

What to do:
  • Use certified disease-free seeds.
  • Treat own seeds in hot water for 20 minutes at 135 °F (43°C).
  • Plant resistant varieties, if available.
  • Practise crop rotation with non-cucurbits.
  • Destroy volunteer cucurbits and weeds in the field.

  • Anthracnose (Colletotrichum orbiculare) damage to pumpkin leaf (Cucumis sativus).

    â’¸ Clemson University - USDA Cooperative Extension Slide Series, www.insectimages.org

  • Anthracnose (Colletotrichum orbiculare) damage to pumpkin leaf (Cucumis sativus).

    â’¸ Clemson University - USDA Cooperative Extension Slide Series, www.insectimages.org

Fusarium wilt

The lower leaves of the plant usually turn yellow and die. One or more branches may exhibit such symptoms. Leaflets on one side may be affected while those on the other side are symptomless. Diseased leaves readily break away from the stem. When affected stems just above ground level and petioles are cut diagonally, a reddish-brown discolouration of the water conducting tissues will be observed. The fungus is both seed- and soil-borne. It causes most damage on light, sandy soils. It is most active at temperatures between 25 and 320C. The fungus can survive in the soil indefinitely even when no tomatoes are grown. It can also survive in fibrous roots of weeds (e.g. Amaranthus, Digitaria and Malva species). Acidic soils (pH 5.0 to 5.6) and excessive nitrogen fertilisation promote disease development. Infestation by root-knot nematodes encourages the disease.

What to do:
  • Use resistant varieties, if available.
  • Use certified disease-free seeds.
  • Avoid spread of the fungus through contaminated farm implements and furrow irrigated water.

  • Wilting of okra plant due to fusarium wilt

    © A.M. Varela & A.A.Seif, icipe

  • Wilting of okra plant due to fusarium wilt

    © A.M. Varela & A.A.Seif, icipe

Fruit rot

Fruit rots are of minor importance in Africa; they are primarily post-harvest problems during storage. In most African countries, cucumbers are sold fresh from farm, consumed and are hardly stored for long (exception could be supermarkets in urban areas where fruits are kept on shelves).

 

What to do:
  • Avoid injuries during harvesting
  • Store fruits properly after harvest

  • Choanephora fruit rot (Choanephora cucurbitarum) on pumpkin

    â’¸ Clemson University - USDA Cooperative Extension Slide Series, www.insectimages.org

  • Choanephora fruit rot (Choanephora cucurbitarum) on pumpkin

    â’¸ Clemson University - USDA Cooperative Extension Slide Series, www.insectimages.org

Mosaic Virus diseases

Cucumber mosaic virus

It is not seed transmitted except through seed of perennial wild cucumber (Echinocytis lobata) and chickweed (Stellaria media). It is mechanically transmitted and in nature it is spread by various species of aphids. It has a very extensive host range including such varied species as bananas, carrots, cowpeas, lupine, lilies, onions, passion fruit, potatoes and tomatoes.

 

Watermelon mosaic virus

This virus is mechanically transmitted and also spread by several species of aphids. It is not seed transmitted. Its host range is primarily restricted to cucurbits although one of its strains infects peas.

 

Squash mosaic virus

It is mechanically transmitted. It is transmitted through seeds of melons and squash. It is also transmitted by spotted, striped and banded cucumber beetles, which attack cucumbers in the Americas. The Epilachna beetle (Epilachna chrysomelina) a pest of cucumber in Africa, is also vector of squash mosaic virus. Its host range includes cucurbits, peas, coriander, and salad chervil.

 

What to do:
  • Use tolerant / resistant varieties if available.
  • Remove infected plants (disinfect hands and tools with 70% alcohol after contact with infected plants).
  • Do proper weeding.
  • Control insect vectors. A sustainable approach of controlling aphids is important to prevent aphids reaching the crops and transmitting virus.
  • In case of squash mosaic virus use certified disease-free seeds.

  • Virus on cucumber

    © A.A. Seif, icipe

  • Mosaic virus on water melon leaf

    © A.M. Varela, icipe

  • Virus on cucumber

    © A.A. Seif, icipe

  • Mosaic virus on water melon leaf

    © A.M. Varela, icipe

Scab (Cladosporium cucumerinum)

It attacks all aboveground plant parts. Initial symptoms on leaves appear as light water-soaked or pale green spots. The spots are numerous and can appear on and between veins. Elongate spots may develop on petioles and stems. The spots later turn grey to white and become angular. The fine veinlets in the spots may be brown and are distinct against a white background. Dead leaf tissue cracks and breaks away until the whole leaf is ragged. Fruits can be attacked at all stages of growth. However, young fruits are most susceptible. Plant tissue near the spots may produce sap, initially watery but later becomes gummy to hard.

The fruit spots are cankerous and with time become darker, sunken until a pronounced cavity is formed. Under moist weather, a dark-green velvety layer of fungal growth appears on the cavities. The fungus survives in crop debris, soil and on seed. It is spread by insects, farm tools and wind. The disease is most severe at 100% relative humidity and at relatively cool temperatures (21-25°C). Its host range includes cantaloupe, gherkin, muskmelon, pumpkin, squash and watermelon.

 

What to do:
  • Use resistant varieties, if available.
  • Use certified disease-free seeds.
  • Practise crop rotation with nonrelated crops.

References and information links 

References

  1. AIC, Nairobi (2003). Fruits and Vegetables Technical Handbook
  2. AVRDC International Cooperators' Factsheet on Cucurbits www.avrdc.org
  3. Beije, C.M., Kanyangia, S.T., Muriuki, S.J.N., Otieno, E.A., Seif, A.A., Whittle, A.M. (1984). Horticultural Crops Protection Handbook.National Horticultural Research Station, Thika KEN/75/028 and KEN/80/017/
  4. Blay, E., Cudjoe, A. R., Braun, M. (Editors) (2000). Handbook of crop protection recommendations in Ghana: An IPM approach. Vol 2; vegetables. Plant Protection & Regulatory Services Directorate (PPRSD) and the Integrated Crop Protection Project, German Development Cooperation (GTZ).
  5. Bohlen, E. (1973). Crop pest in Tanzania and their control. Federal Agency for Economic Cooperation (BFE). Veralgh Paul Parey. ISBN 3-489-64826-9
  6. CAB International (2005). Crop Protection Compendium, 2005 Edition. Wallingford, UK www.cabi.org
  7. East African Seed Co. Ltd. Africa's Best Grower's Guide www.easeed.com
  8. Ekesi, S., Billah, M.K. (Eds) (2006). A field guide to the management of economically important tephritid fruit flies in Africa. ICIPE. ISBN: 92-9064-179-7
  9. Khan, A., Mishra, A., Hasan, S. M., Usmani, A., Ubaid, M., Khan, N., & Saidurrahman, M. (2021). Biological and medicinal application of Cucumis sativus Linn.–review of current status with future possibilities. Journal of Complementary and Integrative Medicine, 19(4), 843-854.
  10. Kuepper, G. (2003). Flea Beetle: Organic Control Options. NCAT Agriculture Specialist. Published ATTRA Publication #CT114. National Sustainable Agriculture Information Service.
  11. Ministry of Agriculture and Rural Development (Kenya) (MoARD) & Japan International Cooperation Agency (JICA) (2000). Local and Export Vegetables Growing Manual. Reprinted by Agricultural Information Resource Centre, Nairobi, Kenya. 274 pp.
  12. Nutrition Data www.nutritiondata.com.
  13. Ostermann, H., Dreyer, M. (1995). Vegetables and grain legumes. In "The Neem tree Azadirachta indica A. Juss. and other meliaceous plants sources of unique natural products for integrated pest management, industry and other purposes". Edited by H. Schmutterer in collaboration with K. R. S. Ascher, M. B. Isman, M. Jacobson, C. M. Ketkar, W. Kraus, H. Rembolt, and R.C. Saxena. VCH. pp. 392-403. ISBN: 3-527-30054-6
  14. Royal Botanic Gardens, Kew. (2023). Plants of the World Online. Retrieved May 26, 2023, from https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:292296-1
  15. Sherf, A.F., Macnab, A.A.(A.A. (1986). Vegetable Diseases and Their Control. 2nd. Edition. John Wiley & Sons Inc. USA. ISBN: 0-471-05860-2
  16. Summers, C.G. and Stapleton, J. J. (2002). Use of UV reflective mulch to delay the colonization and reduce the severity of Bemisia argentifolii (Homoptera: Aleyrodidae) infestations in cucurbits. Crop Protection. Volume 21. Pages 921-928.www.sciencedirect.com
  17. UCANR. UC helps pumpkin farmers produce pumpkins without pesticides. October 2003. www.ucanr.org
  18. van Luijk, M.N., 2004. Cucumis sativus L. [Internet] Record from PROTA4U. Grubben, G.J.H. & Denton, O.A. (Editors). PROTA (Plant Resources of Tropical Africa / Ressources végétales de l’Afrique tropicale), Wageningen, Netherlands. Accessed 30 July 2023.

Information links
•    https://specialtyproduce.com/produce/Cucumbers_385.php
•    https://www.researchgate.net/figure/Top-eight-producers-of-cucumbers-fresh-and-processed-in-the-world_tbl1_311840374
•    https://www.newsnetmedia.com/story/48183798/cucumis
•    https://www.healthline.com/nutrition/7-health-benefits-of-cucumber#TOC_TITLE_HDR_3
•    https://www.tridge.com/intelligences/canned-cucumber
•    https://www.webmd.com/food-recipes/cucumber-health-benefit

Contact Links

 

Review Process

Dr. Patrick Maundu, James Kioko, Charei Munene and Monique Hunziker, June 2024

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