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Credits: Biovision-Infonet

Scientific Name: Brassica spp.

Order / Family: Capparales: Cruciferae/Brassicaceae

Local Names: Kenya: Sukuma wiki (Swahili)Common Names: Common names and related Brassicas; Cabbage, kale, choumolea, Chinese cabbage, cauliflower, rape, broccoli, Brussels sprouts, kohlrabi, savoy, turnip.

Pests & Diseases: Alternaria leaf spot, Aphids, Bacterial soft rot, Bagrada bug, Black leg, Black rot, Cabbage looper, Cabbage moth, Cabbage webworm, Cauliflower Mosaic Virus, Cercospora leafspots, Clubroot, Cottony rot , Cutworms, Damping-off diseases, Diamondback moth (DBM)., Downy mildew , Leafmining flies (Leafminers), Powdery mildew , Ring spots, Sawflies, Thrips, Turnip Mosaic Virus (TuMV), White rust, Whiteflies

Geographical Distribution in Africa

General Information and Agronomic Aspects

Brassicas constitute the majority of cultivated Cruciferae in eastern and southern Africa. The main brassicas grown in the region include:

• Cabbage (Brassica oleracea L. var. capitata)
• Kale (sukumawiki) or choumolea (B.o. acephala)
• Chinese cabbage(B. campestris chinensis/pekinensis)
• Cauliflower (B.o. botrytis)
• Rape B. carinata (indigenous), and B. napus, (exotic type).

Other brassicas grown in the region are broccoli, Brussels sprouts, kohlrabi, savoy and turnip.Also grown in the region are radish (Raphanus sativus L. var. hortensis) and horseradish (Armoracia rusicana Gaertn.)

These vegetables are grown mainly for the local market. They are valuable as sources of vitamins and minerals, as well as a source of cash for smallscale farmers in rural and peri-urban areas. However, production is often constrained by damage caused by a range of pests (insects, diseases, nematodes and weeds).The range of pests attacking the different brassicas is similar, but the relative importance of individual pest species varies between the different crops. Cabbage is mainly sold fresh or as processed canned product. Processed products include those that are treated in vinegar, or fermented such as sauerkraut or kimchi. Fresh cut or lightly processed products include coleslaw and ready-to-eat salad mixes that contain shredded cabbage. Consumers generally prefer fresh green cabbage, when available, to stored cabbage. Much of the stored cabbage is grown for processing.

Climate conditions, soil and water management 

Cabbage is a biennial plant that grows best under full sunlight. The optimum mean temperature for growth and quality head development is 15-18degC, with a minimum temperature of 4degC and a maximum 24degC. Generally, young plants are more tolerant to heat and cold than plants nearing maturity. For seed production cabbage plants need to pass through vernalisation: continuous days with temperatures at 1.7-10 degC before they start bolting. Broccoli and cauliflower produce seed without vernalisation. Cabbage grows well on a wide range of soils with adequate moisture and fertility. Soil pH in the range of 6.0-6.5 is preferred, but cabbage will tolerate a soil pH range of 5.5 to 6.8. Cabbage is a heavy feeder, so to get good yields, proper fertilisation is necessary. To maintain growth, cabbage requires a consistent supply of moisture, and should as a general rule receive a minimum of 2.5 cm of water per week. Larger quantities may be required when cabbage is grown on sandy soils or when evapotranspiration is high.  

Nutrient deficiencies 

Growing healthy plants is the best way of avoiding problems. Healthy plants grow on a healthy and well nourished soil with a good texture. Good compost is the best and most balanced soil and plant feed available to farmers. Regardless of soil type, excessive N (nitrogen) can promote second growth and split heads. A high level of nitrogen will also shorten storage life of cabbage and promote pungent odour (strong smells) during cooking. Combined with high temperatures, excess N (nitrogen) can promote such rapid growth that plants show symptoms of tip burn in susceptible cultivars. Depressed yields, delayed maturity, reduced keeping quality and strong or objectionable flavours are indicative of N deficiency. Like most cruciferous crops, cabbage has a high requirement for boron and molybdenum. Boron deficiency causes yellowing or chlorosis of the youngest leaves and stems, which often starts from the base and extends to the tip, hollow and discoloured inside stems of broccoli and cauliflower, and hollow and/or shrunken roots of turnips. Rosetting or even death of terminal shoots or buds occurs in extreme cases. The common symptoms of molybdenum deficiency in cabbage include a general yellowing, marginal and interveinal chlorosis, marginal necrosis, rolling, scorching and downward curling of margins usually on older leaves. Compost and well rotted animal manures are good sources of most micronutrients including boron and molybdenum. 

Land preparation and management

• Prepare land well before transplanting.
• Avoid field operations when it is wet. This will help to prevent inadvertent spread of diseases from plant to plant and movement of infested soil within and outside the field.
• Keep fields free of weeds. Especially weeds of the brassica family are potential alternative hosts of insect pests and diseases and are nutrient competitors.
• Ensure optimal fertilisation. Cabbage has a very shallow root system and is particularly responsive to phosphorus. Where the soil has a low phosphorus content the application of ‘Mijingu Rock Phosphate’ is recommended.

Propagation and planting Seedlings:

• Practise crop rotation: site seedbeds on land not previously under crucifers, and preferably away from old crucifer fields.
• Use clean wooden trays to raise seedlings, use mixture of compost and top soil or forest soil for raising seedlings.
• Heat soil in the seedbed: place plenty of crop trash or straw and burn for at least 30 min, and after cooling, mix the soil with compost in equal proportions.
• Use certified disease free seed of resistant/tolerant cultivar.
• Mulch seedlings in the seedbed, if possible.
• Do not over water seedlings in the seedbed: water seedlings early in the morning and thin out seedlings to avoid plant congestion in the seedbed. Excessive watering is conducive to damping-off diseases, and extended wetness of seedlings favours development of foliar diseases.

Seeds:

Treating own seed in hot water to prevent seed-borne diseases such as black rot, black leg, black spot and ring spot is recommended where these diseases have previously appeared Hot water treatment of seeds helps reduce the seed-borne pathogens. However, the specified temperature and time interval should be strictly followed in order to maintain seed viability. Use a good thermometer or better ask for assistance from qualified personnel from your local agriculturist office. Recommended temperature and time for hot water treatment for broccoli, cabbage, cauliflower, kale kohlrabi and turnip is 50degC (122 F) for 30 minutes.

Husbandry

• Cabbage is often planted on raised beds that are shaped from bare soil after ploughing and disking. This technique is popular on level soils where furrow irrigation is also used. Bed culture is also used in other areas to improve soil drainage or when plastic mulch is used. The trend has been toward increased use of conservation tillage, particularly on steeply-sloping soils prone to erosion. Producing cabbage using conservation tillage reduces the number of field passes by farm equipment, thus reducing compaction, preserving equipment and conserving fuel.
• Conservation tillage systems cause minimum disturbance to the soil after the previous crop has been harvested. Crop residues are left in the field to reduce soil erosion, conserve moisture, inhibit weed growth, and act as green manure. There are several types of conservation tillage in use, as well as combinations of conservation and conventional tillage. However, in disease management, crop residues must be either removed from the field and destroyed or deeply ploughed to reduce sources of disease infection and spread.
• Advantages of conservation tillage for cabbage production include less machinery, labour and fuel, as well as reduced soil erosion and compaction. Disadvantages of conservation tillage include lower soil temperatures, slower germination and emergence when direct sowing is used, slower early growth, delayed competition with weeds, higher incidence of root diseases, heavier crop residue, the possibility of more difficult planter operation, weed spectrum changes, and potential increase of soil insect pests or insects that spend part of their life cycle in the soil (e.g. cutworms, thrips, leafmining flies, grubs). Cultivation exposes these pests to desiccation by the sun heat and to predation by natural enemies

Intercropping

• Intercrop brassica crops with trap crops or repellent plants, to reduce pest infestation. Tomato reportedly repels diamondback moth and Indian mustard acts as a trap crop. Intercropping brassicas with spinach, beans or dill reportedly reduces aphid infestation.
• Tomatoes when planted 14 days before cabbage reduce the incidence of and damage by diamondback moth. Cabbage intercropped with tomato, coriander or garlic, combined with the application of neem seed kernel extract protects plants from diamondback moth in the field. Indian mustard, Chinese cabbage, and radish are good trap crops for controlling cabbage webworm, flea hopper, and mustard aphid when planted in every 15 rows of cabbage. The mustard row is either in the outermost or in the middle row to avoid caterpillars being blown by wind into the cabbage plants. To control cabbage head caterpillar, Indian mustard should be planted 12 days before transplanting cabbage. Do not plant cabbage where members of the cabbage family have been grown for 3 consecutive years to avoid serious problems of pests and diseases (especially soil borne diseases).

Monitoring

It entails regular field observation during the crop production cycle for pests, diseases, weeds and general aspects of crop health like nutrition and water requirements. Field monitoring methods are virtually the same, but most importantly, in the process is problem recognition. Thus it is very important to be able to identify pests and diseases and to differentiate a pest from a beneficial insect, a pest damage from disease damage, and a pest or disease damage from nutritional problems or physiological disorders.

• Monitor fields regularly for pest and disease occurrence. Early detection of pests and diseases is important as outbreaks are easier controlled in the initial stages. Cutworms and other insects can do a lot of damage in just 1 or 2 days.
• Scout for caterpillar presence: feeding damage and caterpillar excrement give an indication of their activity. Scouting can be done by walking in a zigzag pattern through the field.
• Check for aphids and whether parasitised aphids (mummies) and natural enemies such as ladybird beetles and lacewings are present. Since aphid populations are often clustered, all portions of the field should be checked. 

Harvesting

Cabbage is often hand-harvested when heads are firm to the touch but before cracking begins. With hand harvesting, a given field is harvested two to four times to obtain heads of uniform size and maturity. Only one to three harvests of hybrid cultivars are required because of their greater uniformity. Use of uniform transplants and consistent growing conditions also helps reduce the number of harvests. Yields will vary with the season of production, cultivar, and production system used. With proper management, cabbage can produce 10-12 tons per acre. Generally, most fresh markets prefer heads that weigh on average 1-2,5 kg. For processing into coleslaw or sauerkraut, or for long-term storage, larger-headed cultivars are used.

Field sanitation

Remove crop residues immediately after harvest and also remove volunteer plants from the field.

Varieties grown in Kenya

Seeds of the varieties given below are readily available from seed companies and vendors in Kenya. For information on seed companies contact Horticultural Crops Development Authority. ( info@agricultureauthority.go.ke,  www.agricultureauthority.go.ke, +254 20 88469) 

Cabbage varieties 

“Globe Master F1 Hybrid”

This is a high yielding hybrid cabbage with wide adaptability to different conditions. It has nice blue green colour and globe shaped with short core. It is highly tolerant to black rot and Fusarium yellows. It grows up to 2.5 kg 75 days after transplanting but can grow up to 3.5 kg under optimum conditions, especially in warm areas.

Gloria F1 Hybrid

It is a proven best F1 hybrid in fresh market and processing industry. Well adaptable to various climatic conditions withstanding high temperatures. It is a mid-early maturing variety, ready for harvesting in 90 days after transplanting. Head weighs about 4 kg with solid blue green colour and thick waxy layer and has strong rooting, medium resistance to Fusarium yellows. Has good Pesticide resistance to splitting and keeps well after harvesting.

“Blue Dynasty F1”:

It is adapted to a wide range of agro ecological zones. It is heat tolerant. Maturity is about 80-85 days after planting. Head weight is about 4-6 kg of blue green colour. Yield potential is about is 45-68 t/acre. It is resistant to black rot, ring rot and diamondback moth.It has a good transport quality.

“Victoria F1”

It is widely accepted in various markets. Its very fast growing with maturity period about 70-75 days from transplanting. It uniformly matures. It has compact heads each weighing between 4-5 kg. Its yield potential ia about 45-56 t/acre. It transports well.

“Oxylus F1”

It is adapted to a wide range of agro ecological zones. It has compact heads weighing about 4-5 kg each. Yield potential ranges from 45 to 56 t/acre. Its maturing period is about 70-75 days from transplanting and matures uniformly. It is heat resistant and also resistant to alkalinity. It transports well. 

“Green Coronet F1 Hybrid”

Medium-large, semi-upright plant grows well in medium hot to cold areas, with deep green, oblate head growing up to 4 kg under optimum conditions. Medium-early in maturity and takes about 75-80 days after  transplanting. Has excellent field holding capacity and will last long in the field before bursting.

“Riana F1 Hybrid”

This is an all-round variety that is heat and cold tolerant. It produces round, blue-green compact heads weighing about 2.5 kg. It does well both in temperate, subtropical and tropical zones. It is tolerant against black rot and tip burn. It matures in 90-100 days after transplanting and has excellent non-bursting quality round head after maturity.

“Super Master F1”

Widely adaptabe hybrid, produces round to flat-round, bluish green compact head weighing 4-5 kg. It has an excellent field holding capacity and can stand in the feld for long without bursting. Matures in about 80-85 days after transplanting. It is resistant to Fusarium yellows, Alternaria, medium to high resistance to black rot and diamondback moth.

“Santar F1”

It has a very firm compact, globe-shaped head, which is blue green in colour. The weight is 4-6 kg. It matures in 80-90 days after transplanting. It has good resistance especially to black rot and diamondback moth. It has good transportation ability.

“Field Winner F1 Hybrid”

It takes about 80 days from transplanting to harvest. Head is semi-flat and weighs about 4 kg. It is resistant to black rot. It has a sweet taste.

“CPI”

It is a hybrid cabbage. It has green heads. The weight is 3-5 kg. The shape is round. It matures in 70-80 days after transplanting. It has a good field holding capacity since it does not burst easily. It has a sweet flavour therefore very ideal for salads. It is tolerant to Fusarium and black rot.

“Pruktor F1 Hybrid”

It takes about 80 days from transplanting to harvest. Head is high and round. The head weighs about 5 kg. It has high resistance to black rot. It has shown considerable resistance to diamondback moth. 

“Hero F1 (Sokoni)”

This is a Chinese cabbage. It is an early maturing hybrid, which is ready 65 days after transplanting. It has high tolerance against some virus diseases and black rot. It is strong against heat and cold, vigorous and easy growing. It produces medium sized green head with excellent internal white colour, weighing 2 kg with good transportation and storage ability. It is suitable for high density planting due to its compact round leaves and standing plant habit.

“Chihili”

It is open-pollinated Chinese cabbage. It produces uniform pale green, loaf-like heads, grows vigorously and the core is white. It is prone to bolt at low temperature. It is a widely adaptable cabbage with a slightly tangy flavour, popularly used in salads. Over the years the variety has become very popular in Tanzania.

“Red Dynasty F1”

It is high in anthocyanin with compact heads weighing about 4-5 kg each. Its yield potential ranges from 45 to 56 t/acre. Its early maturing taking about 70-75 days from transplanting. It is resistant to black rot and diamondback moth. It transports well.

“Ruby Perfection F1 Hybrid”

This is a vigorous, easy growing and heavy yielder with a deep red head weighing about 2 kg. Very uniform maturity, is late busting therefore has a long harvest period. It has strong tolerance against heat and cold with ability to form heads at low temperatures. It matures in about 80 days after transplanting.

“Copenhagen Market”

It is open-pollinated. It is the most popular amongst the ball-headed cabbages and a great favourite for the both home and market gardeners in Kenya at present. The heads are uniform round, firm, medium sized and weighing about 2-3 kg. The plant is short-stemmed and rather small, and can be spaced closer. It is early maturing, approx. 60-70 days after transplanting. It is rather sensitive to splitting and should not be left in the field for too long after maturity. It is a highly dependable and productive variety.

“Glory of Enkhuizen”

It is open-pollinated. A nice and attractive variety which is presently more popular in East and Central Africa. The plant is low and relatively wide. The heads are medium large, flat round, green, firm and sweet (sweeter than any drumhead type). It matures after about 12 weeks with the head weighing about 3.5 kg. Harvesting is spread for about 3 weeks thus market supply can be over a long period.

“Prize Drumhead”

It is open-pollinated. A very late maturing variety in about 18-19 weeks. The heads are flat, solid, largest is about 30 cm in diameter and can weigh more than 5 kg. Plants are spreading type and very large, A hardy variety which produces high yields.

“Sugar Loaf”

It takes about 75 days from transplanting to harvest. Head is conical and weighs about 2 kg. Prefers cool conditions. Its suitable for areas with well distributed moderate to heavy rainfall. It should be planted in well drained soils.

Broccoli varieties 

“Calabrese”

An early broccoli with medium large and compact heads with exquisite flavour. An abundance of fleshy stalked flowering shoots are produced over a long period. A nice variety with fine quality.

“Heritage F1”

It is ideal for cool climatic zones. It is dome shaped with lightly beaded florets. Maturity period is about 80 days from transplanting. Potential yield is about 8 t/acre. It has intermediate resistance to downy mildew.

“Dandy Early No. 32 F1”

This is an early, vigorous variety tolerant to black rot and downy mildew. It can withstand high temperatures. The head is firm, dome-shaped about 10-12 cm wide and 6 cm high.It matures 92 days after planting and harvesting continues for about 10 days.

“Early Green F1”

It is early maturing with good quality heads. It has a typical single head and no side shoots. The heads are solid, regular shaped. It is mushroom shaped with uniform bluish green colour. The heads ripen evenly and harvesting starts 85 days after germination lasting 10-12 days. The variety responds well to heavy watering and thrives at high altitudes.

Cauliflower varieties 

“Snowball”

This is a widely adaptable, mid-early variety. The curd is well covered by straight leaves, head is rather round, firm and white weighing approximately 1 kg. It is a popular kitchen garden variety.

“Snow Crown F1 Hybrid”

This is a very early maturing variety in about 70 days after transplanting. Plants are medium-upright with excellent curd quality. The head is white and semi-dome shaped. It is a high yielder with strong tolerance to heat and cold and a very popular hybrid for its easy growing. Head weighs about 850 gm.

“Extra Early Six Weeks”

It takes 65 days from transplanting to harvest. Head is round and firm. Average head weight is about 1.2 kg. It is more exacting in climatic requirements. High temperatures are not favourable. Soils should be clean and high in organic matter.

“Kibo Giant”

It takes about 75 days from transplanting to harvest. Head is snow white, compact and fined grained. Average head weight is about 1 kg. It has large wrapper leaves.

“Fremont F1”

It is ideal for cool climatic zones. Its fast growing with a maturity period of about 90-100 days from transplanting. It has attractive white coloured curd. Yield potential of 7-9 t/acre. Average head weight is 600-800 grams.

“Italian Giant”

It takes 75 days from transplant to harvest. It has a white, smooth and firm head. High temperatures are not favourable for its growth.

“Wallaby”

It takes 80-85 days to harvest from transplanting. Head is snow white, compact and fine grained. 

Kale varieties

“Thousand Headed”

This is a continuous growing and hardy crop that is tolerant to cold temperatures. It can stay in the field for a long time, therefore, giving a higher yield. It has a thick stem with big leaves that are dark green, smooth and attractive. It matures between 90-100 days. It can also be used as fodder for animals. It is easily digestible and easy to cook.

“Southern Georgia”

It is a very popular seed variety grown across Africa. It has been developed to give high yields while up to 6 months before flowering thus profitable to farmers.The leaves are well flavoured and easy to cook. It is popular in the local market. It is adapted to hot areas. It is hardy and resistant to black rot.

“Marrow Stem”

The variety has dark green leaves and flavour and little fibre. It is vigorous, medium tall with finely curled leaves which are less prone to bird damage.