Altitude range

Beans do well at altitudes between 1000 – 2000 m.a.s.l. It however tends to grow and mature faster in low altitude zones.

Soil type and conditions

Beans require well-drained loam soils with high organic matter content.  Soil pH: 6.0 – 7.0 is ideal.

Temperature range

The temperatures should be 20 – 30 ^oC for optimal growth.

Rainfall

A well distributed annual rainfall of between 750-1200mm  is ideal.

Recommendations for land preparation

1. Consider minimum tillage to conserve soil, water and nutrients, and to reduce cost and workload.
2. Plough using chisel ploughs, hand hoes or oxen drawn implements to aerate the soil.
3. In gentle to moderately sloping fields, use contour farming techniques to improve on soil and water conservation.

Common planting materials:

Common planting materials include certified seeds and farmer saved seeds. Certified seeds are produced by registered seed companies and should be bought from reputable agro-dealers. Farmer saved bean seeds are good alternatives where certified seeds are not available or considered too expensive. The selection process for seed saving should include observing growth and tolerance to adverse conditions. Ensure that saved seeds are free of weed seeds, insects or disease damage. 

Seeds

New bean varieties with higher iron and zinc levels (eg. Nyota) should be promoted as they are important in strengthening the human immune system.

Varieties can be differentiated between bush type beans and climbing beans. There are also early maturing varieties and late maturing varieties. Some varieties are developed for the fresh market (Green beans, French beans).

Recommended varieties commonly grown in western Kenya include Rose Coco, Mwitemania, Mwezi moja, Katumani Bean 1 (KAT/B-1), Katumani Bean 9 (KAT/B-9), KAT X56, KAT X69. 

The website of Seed Sector Platform Kenya (www.seedsectorplatformkenya.com) gives a good overview of available commercial seed varieties. 

Recommended varieties :

• Select seeds that are adapted to local agro-ecological zones and from a recommended source
•  Ensure the required variety

Geminating seed

Germinating seedlings

Planting Procedures

Sort out good seeds, especially when using farmer saved seeds, to ensure that they are free from insects, disease, weed infestation or mechanical damages.

Plant at the onset of rains, when soil moisture is sufficient for the crop to take advantage of nitrogen flush.

Plant parallel to the contour lines, especially in sloping fields. Minimum tillage direct seeding is preferable to maintain parallel planting lines.

Recommended plant spacing

Bush type beans, pure stand; Row spacing may vary from 25 to 60 cm depending on variety. Spacing in the row may vary from 8-10 cm (1 seed per planting hole) to 15-25 cm (2-3 seeds per planting hole).  Planting depth is 2.5- 5 cm .

On average the required seed rate is 23 kgs per acre.

Fill gaps one to two weeks after planting, when plants have emerged.

Climbing beans: Plant climbing beans in rows which are 75 cm apart. Within a row, sow seeds 15 cm apart (1 seed per stand) or 25-30 cm apart (2 seeds per stand).

• Drip irrigation is well suited as it causes less diseases than overhead (sprinkler) irrigation. Irrigate early morning or late evening to avoid excessive evaporation

• Soil and water conservation methods and minimum tillage techniques, including sub-soiling (ripping,) should be practiced to increase organic matter content of the soil, and improve the water-holding capacity.

• The use of mulch, especially in early growth stages, will reduce evaporation from the soil and add organic matter.

Weeding by hand is recommended to avoid damage to the bean plant and roots. 1^st weeding is done 2 weeks after emergence and 2^nd weeding just before flowering.

Uprooted weeds should be left between the plant rows to act as mulch unless they are already in seed.

• Add manure and fertilizers to the soil in the amounts recommended from soil testing and analysis to provide the required plant nutrients for vigorous crop growth.

• The use of well decomposed manure (Compost) will improve soil biology and fertility.

• The current MoA recommendation for beans is as follows:

  At planting: 50 kg/acre of NPK blend. Baraka Planting Blend also contains micro-nutrients (Ca, Mg, B, Mn, S). The fertilizer is placed in the planting furrow and mixed with the soil before placing the seed.

• Compost can be applied in the planting furrow and mixed with the soil before placing the seed. NPK blend is added to the compost at half the rate (25 kg/acre).

• Beans do not require top dressing. The crop should not be planted where soil nitrogen is too high or where green manure crops were grown. This is because the crop will produce green foliage with very few beans.

• Implement soil conservation measures to reduce soil erosion and improve water holding capacity of the soil.

• Practice conservation farming approaches like minimum soil disturbance, permanent soil cover, and crop rotation to improve soil structure and soil biology.

• Apply IPM principles for increased use of biophysical methods and reduced use of agrochemical methods to control weeds and pests.

• Thin the crop 14 days after plant emergence to minimize competition for nutrients, water and light.

Major Pests include;

African bollworm (Heliothis armigera), Bean aphid (Aphis fabae), Bean fly (Ophiomyia spp), Flower thrips (Taeniothrips siostedti) and Leaf miner

They are controlled by field use of Integrated Pest Management (IPM), plant early or harvest early, rogueing, crop rotation, resistant varieties

Symptoms of common pests and their control

Use of appropriate insecticides as recommended by experts

African bollworm (Heliothis armigera)

Symptoms: Larvae feeds on leaves, flowers and pods. It bores holes on the pod and feeds on the seeds, with its head inside the pod and the rest of the body outside.

Control

• Use of natural enemies which parasitize the larvae (Biological control eg Bacillus thuringiensis )
• If infestation is high, spray recommended insecticide eg Pentagon 50EC.

(ii)Bean aphid (Aphis fabae)

Symptoms: Aphids are soft bodied green, black or brown insects which suck plant sap. Infested leaves curl and crinkle. They also attack the pods. Their excreta, honeydew, enhances the growth of sooty mold which reduces leaf photosynthetic area.

Control

• Use tolerant varieties if available.
• Use reflective mulches such as silver colored plastic to deter aphids from feeding on plants.
• Knock aphids from leaves using strong jets of water.
• Apply insecticidal soaps or oils such as neem.
• Spray with insecticides eg Kingcode Elite 50EC, Pentagon 50EC, if infestation is very high

(iii)Bean fly (Ophiomyia spp)

Symptoms: The larvae tunnels into the plant stem damaging the vascular tissue, causing reduced plant vigour; petioles droop in older crops; seedlings die under severe infestation.

Crops are at a greater risk 3-4 weeks after emergence.

Control

• Apply insecticidal soap
• Use natural enemies
• Dress seeds before planting with Shield 600FS
• Spray recommended insecticide eg Kingcode Elite 50EC or Lexus 247SC, if infestation is high.

(iv)Flower thrips (Taeniothrips siostedti)

Symptoms: The pest feeds on leaves and flowers by sucking the sap. Heavy infestation leads to flower and flower buds abortion; and leaves fall off.

Control

• Use natural enemies
• Apply insecticidal soap to plants.
• Spray recommended insecticide eg Profile 440EC

(v)Leaf miner

Symptoms: The larva (cartapillar) mines under the leaf surface, resulting into development of thin, white, winding trails (mines). Heavy infestation leads to white blotches on leaves and leaves dropping from plant.

Control

• Field sanitation – by removing plants from soil immediately after harvest.
• Use of natural enemies
• Spray recommended insecticide eg Escort 19EC, Alonze 50EC, etc.

(vi) Whiteflies

Symptoms: These are white insects which suck plant sap. Infested leaves curl, become distorted and eventually drop. They secrete honeydew which enhances the growth of sooty mold on the leaves, thus affecting photosynthesis.

Control

• Use natural enemies
• Apply insecticidal soap to plants.

Spray recommended insecticide eg Profile 440EC

Diseases include;

Root rots (Fusarium, Black), Leaf spots (Angular Phaeisariopsis griseola, Alternaria) Anthracnose (Colletotrichum lindemuthianum), Bean rust (Uromyces appendiculatus), Bacterial blight (Halo Pseudomonas phaseolus, Common Xanthomonas phaseoli, Ashy stem (Macrophomina phaselina), Bean common mosaic necrosis virus (BCMV), Bean scab (Elsione phaseoli) and White mould (Sclerotinia phaseoli)

(i)Root rots (Fusarium, Black)

Cause: Fungus; survives in plant debris in the soil.

Symptoms: Elongated red-purple lesions on root tissue which turns dark grey to black; lesions coalesce to form large dark areas on roots and stems.

Deep lesions cause stunted growth, wilting or chlorosis of leaves, defoliation, decayed roots and plant death.

Control

• Avoid excess irrigation or drought stress
• Crop Rotation crops with non-susceptible grasses
• Plant tolerant varieties

(ii)Leaf spots (Angular Phaeisariopsis griseola, Alternaria)

Cause: Fungus; Emergence favored by high humidity and warm temperatures.

Symptoms: Small irregular brown lesions on leaves which expand and turn gray-brown or dark brown with concentric zones; lesions coalesce to form large necrotic patches.

Older areas of lesions may dry out and drop from leaves causing shot hole.

Control

Plant beans in fertile soils. Plants grown in nitrogen and potassium deficient soils are more susceptible

(iii)Anthracnose (Colletotrichum lindemuthianum)

Cause: Fungus; disease transmitted through infected seed.

Symptoms: Dark brown to black sunken lesions on pods, stems and seeds. Attacked leaves have black spots.

Control

• Plant resistant varieties
• Use certified disease free seeds
• Field sanitation – to reduce levels of inoculum. Fungus can survive in crop debris
• Avoid sprinkler irrigation
• Crop rotation.
• Spray Ransom 600WP, Absolute 375SC, or Ducasse 250EW.

(iv) Bean Rust (Uromyces appendiculatus)

Cause: Fungus; Spores spread by air.

Symptoms: Initially symptoms appear as small yellow/white spots on leaves. Later the spots become enlarged and show raised brick red rust pustules on leaves, pods and stems. Normally this pustules are surrounded by a yellow halo. Heavy infestation causes premature leaf drop and plant death.

Control

• Plant resistant varieties
• Destroy infected crop debris
• Crop rotation
• Keep the field free from weeds
• If infection is severe, Spray fungicide eg Milestone 250SC, Ducasse 250EW, Ransom 600WP.

(v)Bacterial blights (Halo and Common)

Cause: Bacterium; disease emergence favored by warm temperatures and wet weather conditions.

Symptoms: Small brown blotches/spots on the leaves which enlarges and become necrotic; spots may be surrounded by a yellow discoloration; lesions coalesce and give plant a burnt appearance. Leaves that die remain attached to the plant. On pods, circular, sunken, red-brown lesions may be present.

Control

• Plant only certified seed
• Plant resistant varieties
• Spray crop with protective copper based fungicide before appearance of symptoms.( eg Greencop 500WP)

 
(vi)Bean Common Mosaic Necrosis Virus (BCMNV)

Cause: Viruses; transmitted by seed.

Symptoms: Mottled dark and light green patterns on leaves; leaves may be distorted; yellow dots on leaves; Reduced plant growth.

Control

• Plant certified seeds
• Plant resistant varieties

(vii)Bean scab

Symptoms: The pathogen attacks all parts of foliage.

On stems, symptoms are elongated raised lesions which coalesce to cover big portions.

On leaves, the lesions are ashy grey, roundish to irregular.

On pods, the lesions are roundish to irregular with brown to brick red margins.

Control

• Plant certified seeds
• Use resistant varieties
• Spray recommended fungicides eg benlate and copper oxychloride.

(viii)Fusarium wilt

Symptoms: Sudden yellowing of leaves which eventually fall off, resulting into withering of the plant. Vascular tissues become discoloured.

Control

• Crop rotation
• Drench soil with Greencop 500WP
• Spray recommended fungicide eg Colonizer 440WP or Trinity Gold 425WP.

(ix)White mold (Sclerotinia sclerotum)

Cause: Fungus; disease spread by wind, irrigation water and infected seeds.

Symptoms: Flowers covered in white, cottony fungal growth; dark green, water-soaked lesions on pods, leaves and branches which enlarge and become slimy. Cottony white growth on lesions during periods of high humidity; death of branches and/or entire plant.

Control

• Crop rotation with non-hosts like cereals.
• Plant rows parallel to direction of prevailing winds to prevent spread from nearby hosts.
• Use wide row spacing.
• Avoid excessive nitrogen fertilizer.

At maturity bean plants and pods have dried up and turned yellow or brown.

• Harvesting of fresh green beans (immature seed pods) can start as early as 6 weeks after planting, and should be done frequently to pick the desired grade

• Harvesting of dry beans should be done before pods begin to shatter or rot.

•  Climbing beans have a longer growing period and can be harvested (for green beans) over a longer period.

•  Beans can produce between 1.0 – 2.8 tons per ha (0.4 – 1.1 tons per acre).

   

•  As an alternative, store in sisal or jute bags but this requires fumigation or the use of insecticides to protect the beans from weevils.

• Storage bags should be placed on pallets or raised platform.

  Protect the bags or metallic silos from moisture absorption, insects and rodents.