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Carrot
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Carrot
Scientific name:
Daucus carota
Family:
Araliales: Apiaceae
Pests and Diseases:
African armyworm  Bacterial soft rot  Cottony soft rot  Cutworms  Damping-off diseases  Leaf blight  Powdery mildew  Root-knot nematodes 
Hide: General Information and Agronomic Aspects
General Information and Agronomic Aspects
Geographical Distribution of Carrots in Africa
Carrot is a popular vegetable with high vitamin A content, grown in East Africa mostly in the cooler highlands. The roots are consumed raw or cooked, alone or in combination with other vegetables (for example, peas), as an ingredient of soups, sauces and in dietary compositions. Young leaves are sometimes eaten raw or used as fodder. Carrots are an important source of vitamin A in human diets. Vitamin A deficiency can lead to blindness and especially for children to a greater risk of dying from ailments such as measles, diarrhoea or malaria.












Nutritive value per 100 g of edible portion
Raw or Cooked Carrot Food
Energy
(Calories / %Daily Value*)		 Carbohydrates
(g / %DV) 		Fat
(g / %DV) 		Protein
(g / %DV) 		Calcium
(g / %DV) 		Phosphorus
(mg / %DV) 		Iron
(mg / %DV) 		Potassium
(mg / %DV) 		Vitamin A
(I.U)		 Vitamin C
(I.U)		 Vitamin B 6
(I.U)		 Vitamin B 12
(I.U)		 Thiamine
(mg / %DV) 		Riboflavin
(mg / %DV) 		Ash
(g / %DV)
Carrot raw 41.0 / 2% 9.6 / 3% 0.2 / 0% 0.9 / 2% 33.0 / 3% 35.0 / 4% 0.3 / 2% 320 / 9% 16705 IU / 334% 5.9 / 10% 0.1 / 7% 0.0 / 0% 0.1 / 4% 0.1 / 3% 1.0
Carrot cooked 35.0 / 2% 8.2 / 3% 0.2 / 0% 0.8 / 2% 30.0 / 3% 30.0 / 3% 0.3 / 2% 235 / 7% 17036 IU / 341% 3.6 / 6% 0.2 / 8% 0.0 / 0% 0.1 / 4% 0.0 / 0% 0.7
*Percent Daily Values (DV) are based on a 2000 calorie diet. Your daily values may be higher or lower, depending on your calorie needs.


Climatic conditions, soil and water management
Carrots can grow under a range of climatic conditions, but they perform best under moderate temperatures. They are mostly cultivated as a cool season crop. Seed germination occurs between 7°C and 30°C. Optimum air temperatures are 16-24°C. Soil temperatures above 25°C may reduce root quality, including root colour. High temperatures can cause burning of young seedlings. For economic yields, carrots should be grown in tropical regions at altitudes above 700 m. Early-maturing carrot cultivars may grow in the lowlands, but yields will be low and roots will have a poor colour.

Carrots grow best in a well-drained friable loam free of stones and hard soil clods. It is a short season crop of 2-3 months with the potential of high yields for family food security and fresh market sales. It does well in the cooler areas of Kenya under both rainfed and irrigated conditions.

Propagation and planting
Carrots are propagated by seeds. Seeds are sown, often mixed with sand, 1/2 - 1 cm deep in drills 10-15 cm apart in finely prepared soils previously cultivated to a depth of at least 30 cm. Lightly aerate the soil by shallow digging before sowing carrots or sow them in ridge culture (small dams of 10 to 20cm height) to facilitate mechanical weeding, thinning, and to limit soil borne diseases. In addition, this will allow easier penetration by the carrot root and will also improve water holding capacity.
Seedlings are thinned to 5-8 cm in the rows. Seed requirements (200 plants/m² and 70% germination) for the dominant half-long carrot cultivars used in Asia, are 4-5 kg/ha. For bigger carrots, the density may be reduced to about 100 plants/m².

Examples of Varieties
"Chantenay" Fresh market and canning
"Nantes" Fresh market
"Amsterdam forcing" Fresh market variety
"Little finger" Suitable for canning
"Nebula F1" Fresh market
"Touchon" Fresh market


Carrots that bolt (produce seed) in between normal carrots should be pulled out and fed to livestock. Seed produced this way will not produce good quality carrots. Seed production under tropical highland (above 1200 m) conditions is possible by selecting and harvesting the best quality mature carrot roots and replanting them separately in a corner of the field. Bolting and seed setting soon follows.

Husbandry
Crop rotation is essential to reduce soil-borne diseases and pests. Mulching (rice straw or dried grass) after sowing is recommended to encourage germination. Seedlings may be earthed-up when roots start swelling to keep them cool and prevent green tops. Temperature of 15 to 20°C is optimal for seed development. In hot weather, light overhead shade is beneficial. Under such conditions carrots grow well under the canopy of fruit trees. Irrigation during dry spells is necessary to prevent irregular root development. Nutrient requirements of carrots are particularly high for potassium (200-300 kg/ha) and low to medium for nitrogen (0-90 kg/ha). Carrots are sensitive to high Chlorine concentrations and more susceptible to diseases at very high soil pH. Liming is recommended when pH is below 5.5. Well-decomposed organic manures are beneficial when applied moderately (10-20 t/ha). Fresh organic matter such as farmyard manure or manure from a leguminous crop can induce forked roots, which are difficult to clean and to market.

Young carrot seedlings are weak and grow slowly. Therefore, it is essential to keep weeds under control for the first few weeks after germination. Cultivate shallowly with a hoe.

Deep cultivation may injure the roots. Weeding and thinning of young plants can be very labour intensive, for which reason most families grow fairly small beds at any one time.

Intercropping
Because of their limited space requirements and early growing habits, carrots are ideal for intercropping between other crops such as tomatoes, lettuce or capsicums and because of their fragrant leaves can help keep pest levels low. Other crops good for intercropping with carrots include garlic, dwarf bean, onion, parsnip, leek, small peas, pea mange-tout (snow peas), and radish. The most profitable example of an association is that of carrots and leeks. Carrots have very deep roots that extract nutrients deep in the soil, whereas leeks have extremely superficial roots, which help the crop to extract nutrients near the soil surface. Moreover, carrots can drive away worms from leeks, while leeks can drive away flies from the carrots (TOF No. 8, page 8).

Harvesting
Carrots are mostly harvested manually by pulling up the roots at the leaves as long as the soil is moist and soft. If the soil has dried, it will be necessary to use either a spade or similar tool to loosen the soil and harvest the roots. Carrots are usually ready for harvesting 60-85 days after sowing. Mature roots should be orange-coloured internally down to the blunt tip.

A good market price can be fetched from young carrots with a fresh top, but leaving the top on dries out the root quickly and reduces the marketing period of the crop. An alternative is to trim the top back to about 2 cm and package attractively.

For mature carrots the tops are trimmed down completely to avoid storage rots before marketing. Carrots can remain in good condition for 100-150 days when the foliage is removed and they are stored at 1-4° C with 95-100% relative humidity. Carrots should be stored separately from other vegetables to prevent a bitter flavour induced by ethylene (a colourless gas with a sweet odour that is produced by many fruits and vegetables that accelerates the ripening process). Generally carrots store better when they are mature and harvested under moist conditions, and undamaged and free of diseases and pests.
Hide: Fresh Quality Specifications for the Market in Kenya
Fresh Quality Specifications for the Market in Kenya
The following specifications constitute raw material purchasing requirements

© S. Kahumbu, Kenya

Hide: Information on Diseases
Information on Diseases

Cottony soft rot (Sclerotinia sclerotiorum)

The disease is caused by the fungus Sclerotinia sclerotiorum and is characterised by development of soft, watery rot of leaves, crowns and roots. Affected areas become covered with white, cottony fungal growth in which black, irregular, fungal resting bodies (sclerotia) form. The sclerotia enable the fungus to survive for long periods in the soil. This disease is a serious field and storage problem. If diseased roots are packed, extensive breakdown may occur during transit and storage.

What to do:
  • Practice 3-year rotation using cereals and forage grasses.
  • Soil flooding is helpful where feasible.
  • Do not pack and store damaged and or diseased roots.
  • Use clean containers in storage.
  • Maintain temperature near 0°C and a relative humidity no higher than 95% during storage.
Cottony soft rot (Sclerotinia sclerotiorum) on carrot
Greyish, white mold forms at the base of stem. Black round structures appear as disease progresses. The disease can extend underground to the root.
© David B. Langston, University of Georgia, Bugwood.org

Leaf blight (Alternaria dauci)

The disease is caused by the fungus Alternaria dauci. Dark-grey to brown, angular spots form on leaves. Surrounding tissue yellows and affected leaves eventually die. Older leaves are attacked first and only in very severe cases are younger leaves affected. Large spots can girdle leaf petioles and kill leaves without spots developing on individual leaflets. During warm moist weather, dying of affected leaves may occur so rapidly that plants appear scorched. This fungus can also cause seedling damping-off. The fungus is seed-borne and survives in the soil crop debris.

What to do:
  • Use resistant hybrids where available.
  • Use certified disease-free seeds. In case of using own seeds hot water treat seeds. For information hot water treatment of seeds click here
  • Avoid parsley in crop rotation and practice good field hygiene.
  • Enhance aeration of crop field by less dense crops and ridge cultivation.
  • No or little N-fertilisation.
  • Monitor fields regularly to be able to react properly.
  • Copper treatments can reduce infection. For more information on copper click here
Leaf blight (Alternaria dauci)
Small, irregular, black to purplish coloured spots. Spots may coalesce to cover the entire leaf.
© David B. Langston, University of Georgia, Bugwood.org

Powdery mildew (Erysiphe polygoni)

The disease is caused by the fungus Erysiphe polygoni (E. heraclei). It is characterised by the development of white, powdery fungal growth on leaves. Affected leaves become chlorotic and eventually die. The fungus is seed-borne.

What to do:
  • Use certified disease-free seeds if using own seeds hot water treat the seeds.
  • Practise good field hygiene.
  • Practise over-head irrigation where feasible.
  • Spray with sulphur based products where acceptable.
Powdery mildew on carrot
Powdery mildew on carrot caused by Erysiphe heraclei
© www.poljoberza.net

Damping-off on carrot (Phythium sp.)

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 disease-free seeds and excessive watering of seed-beds or field plots.

What to do:
Damping-off
Damping-off on carrot (Phythium sp.)
© David B. Langston, University of Georgia, www.bugwood.org

Bacterial soft rot (Erwinia carotovora var. carotovora)

Erwinia carotovora subsp. carotovora is a bacterium. Bacteria survive in decaying refuse and enter the root principally through cultivation wounds, harvest bruises, freezing injury, and insect openings. After infection, high humidity is essential for progress of the disease. When soft rot occurs in the field, it usually follows a period of water logging in low areas following excessive rain or irrigation. Carrots, potatoes, onions, crucifers, and celery are only a few of the many plants attacked.

The disease causes a soft, watery, slimy rot. The rotted tissues are grey to brown and may have a foul odour. It decays the core of the root. Also prolonged wet weather favours disease development. It is a serious transit and storage problem if affected carrots are not discarded. In the field, tops of rotted carrots turn yellow and wilt as roots break down.

What to do:
  • Follow a crop rotation of cereals and fodder grasses.
  • Destroy by burning of infected plants.
  • Carefully handle carrots at harvesting to minimise bruising.
  • Discard affected carrots before transport and storage.
  • Store carrots in well ventilated places.
Soft rot on carrot (Daucus carota)
Bacterial soft rot caused by (Erwinia carotovora var. carotovora) on carrot
© Oregon State University
Hide: Information on Pests
Information on Pests

Root-knot nematodes (Meloidogyne spp.)

Various species of Meloidogyne cause galls or swellings on the fleshy tap-root. In warm climates M. incognita, M. javanica and M. hapla are the main species causing problem. The disease is a problem in carrots grown in sandy soils.

What to do:
  • Plant resistant hybrids where available.
  • Practice crop rotation with cereals and fodder grasses.
  • A 3-year stop for all Apiaceae and Chenopodiaceae crops and a 4 to 5 year stop for legumes is needed to interrupt the life-cycle of these nematodes.
  • Soil amendments with neem cake or extracts are recommended.
  • Where feasible, practice at least 1 year fallow cultivation.
Root-knot nematodes of carrot
Root knot nematodes (Meloidogyne spp.): Note galling and deformation of carrot roots
© University of Hawaii, www.ctahr.hawaii.edu/nelsons

Cutworms (Agrotis spp)

Cutworms such as the black cutworm (Agrotis ipsilon) and the common cutworm, also known as the turnip moth (Agrotis segetum), attack carrot roots. Feeding on roots causes holes ranging from small and superficial to very large deep holes.

What to do:
  • Conserve and encourage natural enemies. For more information on natural enemies click here
  • Plough fields to expose caterpillars to predators and dessication by the sun.
  • Destroy weeds and vegetation before planting.
  • Flood fields for a few days before planting.
  • Spread ash thickly in the seedbeds, around seedlings or mixed with the soil in the planting holes.
Cutworm
Cutworm (Agrotis sp.) Early instars are about 7-12 mm long. Fully grown caterpillars are 35-50 mm long.
© A.M. Varela, icipe

The African armyworm (Spodoptera exempta)

The African armyworm can cause serious crop losses. Armyworms may cause indirect injury to the taproot by cutting stems and/or consuming foliage above ground.

What to do:
  • Monitor regularly field margins, low areas where plants have lodged, beneath plant debris around the base of plants, on the ground, and underneath the plant leaves. Check daily young crops if conditions are known to be favourable for to the pest.
  • Spray Bt or botanicals such as neem and pyrethrum extracts. Spray when caterpillars are small. Once caterpillars are mature (about 3 to 3.5 cm long) they may have cause serious damage and it may no longer be economical to treat the crop. For more information on (neem click here, for pyrethrum click here and for Bt click here)
  • Conserve and encourage natural enemies. For more information on natural enemies click here
  • Practise field sanitation. For more information on field sanitation click here
The African armyworm
African armyworm (Spodotera exempta). Mature caterpillars measure up to 4 cm.
© University of Arkansas
Hide: Information Source Links
Information Source Links
  • Agricultural Information and Resource Centre (2003): Fruits and Vegetables Technical Handbook.
  • CABI. (2004). Crop Protection Compendium, 2004 Edition. © CAB International Publishing. Wallingford, UK. www.cabi.org
  • East African Seed Co. Ltd. Africa's Best Grower's Guide www.easeed.com
  • Herold, W. (1919). A contribution to the knowledge of Agrotis segetum, Schiff. Zeitschrift für angewandte Entomologie, 1:47-59.
  • Madge, D., Jaeger, C., Clarke, S. (2003). Agriculture notes. Organic farming: Carrot production and marketing. State of Victoria, Department of Primary Industries. www.dpi.vic.gov.au
  • Ministry of Agriculture and Rural Development (Kenya) and Japan International Cooperation Agency (2000). Growing Manual for Local and Export Vegetables. Reprinted by Agricultural Information Resource Centre (Nairobi, Kenya). 274 pp.
  • Neergaard P. (1945). Danish Species of Alternaria and Stemphylium. London, UK: Oxford University Press.
  • Nutrition Data www.nutritiondata.com.
  • Pests of carrot: www.ipm.ncsu.edu
  • Sherf, A. F., Macnab, A. A. (1986). Vegetable Diseases and Their Control. 2nd. Edition. A Wiley-Interscience Publication. ISBN: 0 471 05860 2
  • University of Illinois Extension. www.urbanext.uiuc.edu
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