Bean (Phaseolus vulgaris) is considered as one of the most important legumes worldwide, which is a source of nutrients to many people. It is a staple food crop in Kenya, which rates second after maize. The crop is grown in almost all regions in Kenya. However, Eastern, Nyanza, Central, Western and Rift valley are the major bean growing provinces.
Bean crops grow with very minimum care and adds Nitrogen to the soil.
Bean Varieties
A wide range of bean varieties are grown in Kenya. These include the following;
- Rose Coco
- Mwitemania
- Wairimu
- Mwezi Moja
- Canadian W
- KK 15
Bean Ecological Requirements
- Soil– bean crop thrives in a well-drained soil which is rich in organic matter, weed free and has an optimum PH of 6.5 – 7.5. Growth is poor in waterlogged soils.
- Altitude– the crop does well at an optimum altitude range of up to between 1000-2100M ASL. It however tends to grow and mature faster in low altitude zones.
- Rainfall– a well distributed annual rainfall of between 800-2000mm is suitable for the rain fed production. Irrigation should be done if rainfall is inadequate. Too much rain or long dry spells are not conducive and reduces yields. Excessive rainfall during flowering causes flower abortion and increased disease incidences. Dry weather conditions are needed during harvesting.
- Temperature– beans grow in temperatures ranging from 15-33 degree centigrade. However, an optimum growing temperature of 20-25 degrees centigrade is essential. Relatively high temperatures affect flowering and pod setting processes. The crop is very sensitive to frost.
Bean Planting
Propagation is by seeds; it is advisable to use certified seeds or those that are disease free. Wrinkled, damaged and diseased seeds should not be planted.
Planting should be done at the onset of the rains if production is rain fed. Delay in sowing may lead to crop failure or reduced yield.
Seeds are planted at a spacing of 40*15cm (2seeds per hill) or 30*15cm (1seed per hill), at a depth of 1-2 inches.
The crop can be intercropped with others like maize.
Seeds germinate within 4 – 7days, depending on the variety and environmental factors.
NB; Do not plant beans where soil Nitrogen is too high or where green manure crops were grown. This is because, the crops will produce green foliage with very few beans.
Beans Pests and Diseases Management
Pests
- Cutworms – these are brown or black caterpillars usually found in the soil, which cut the stem of younger plants below the soil surface.
DRESS seeds with SHIELD 600FS 3 ml/kg, DRENCH soil with PROFILE 440EC 3 ml/l
- Bean fly – the larva tunnels into the plant stem damaging the vascular tissue, causing reduced plant vigour and petiole droop in older crops. Severe infestations can lead to death of seedling. Crops are at a greater risk for 3 – 4weeks after emergence, however, later on, crops can be attacked.
DRESS seeds with SHIELD 600FS 3 ml/kg, DRENCH soil with PROFILE 440EC 3 ml/l, SPRAY LEXUS 247SC 8 ml/20l to kill the adults.
- Red spider mites – these are tiny reddish yellow pests found on the undersides of the leaves. Their feeding leads to formation of yellow stipples on leaf surfaces they form webs in cases of heavy infestations.
SPRAY ALONZE 50EC 5ml/20l
- Aphids – these are soft bodied, green, black or brown insects which suck plant sap. Infested leaves curl and crinkle. They also attack the pods. As they feed, they excrete honeydew which encourages the development of sooty mold which reduces photosynthetic area.
SPRAY LEXUS 247SC 8 ml/20l, SPRAY JAMBO CLEAN 5 ml/l to get rid of the sooty mold.
- Leaf miners – the larva (caterpillar) mines under the leaf surface, resulting into development of mines / winding trails. Heavy infestations lead to death of the leaves.
SPRAY ALONZE 50EC 3 ml/20l
- Pod borer – African bollworm is the most common borer which feeds on leaves, flowers and pods thus damaging them. It bores holes on pods and feed on the seeds, with its head inside the pod and the rest of the body outside.
SPRAY PENTAGON 50EC 10 ml/20l
- Whiteflies – these are white insects which suck plant sap. Infested leaves curl, become distorted and eventually drop. They secrete honeydew as they feed which facilitates the development of sooty mold on the leaves affecting photosynthesis.
SPRAY PROFILE 440EC 1.5 ml/l, SPRAY JAMBO CLEAN 100ml/20l to clean the sooty mold if need be.
- Thrips – they feed on leaves and flowers by sucking the sap. Heavy infestations lead to flower and flower buds abortion. Leaves fall off.
SPRAY ALONZE 50EC 5 ml/20l or PROFILE 440EC 30ml/20l
Diseases
- Bean rust – infection leads to formation of reddish brown pustules on leaves, pods and stems. Heavy infections cause plant death.
SPRAY DUCASSE 250EW 1 ml/l or RANSOM 600WP 15 g/20l
- Downy mildew – infection begins on the underside of the leaf which leads to formation of whitish or grey mass of fungal growth. The upper side of the leaf becomes chlorotic. Pods develop whitish patches.
SPRAY GEARLOCK TURBO 250WP 25 g/20l
- Anthracnose – infection causes development of brown to black sunken lesions on pods, stems and seeds. Attacked leaves have black spots.
SPRAY RANSOM 600WP 15 g/20l or ABSOLUTE 375SC 10 ml/20l
- Bacterial blight – symptoms begin as small brown blotches on the leaves which enlarge as infection continues eventually causing the leaves to fall off and subsequent death of the plant follows.
SPRAY GREEN COP 500WP 50g/20l
- Fusarium wilt – plants show sudden yellowing of leaves which eventually fall off, resulting into withering of the plant. The vascular tissues are discolored.
Drench soil with GREENCOP 500WP 5 g/l, TRINITY GOLD 425 WP2.5 g/l
Bean Nutrition
For optimal production, it is important to ensure that the crop is supplied with sufficient nutrients, both macro and micro nutrient elements. This is because, if deprived of such nutrients, the crop becomes weak and very susceptible to attack by pathogens. This subsequently leads to reduced yield.
During planting, application of a Phosphorous rich fertilizer is recommended. Considering the amount of organic matter in the soil, manure can also be applied. In order to improve on nutrient uptake by the plants as well as stimulating their growth, the fertilizer and/or manure should be mixed with HUMIPOWER at the rate of 1 kg Humipower into 1 ton manure or 50 kg basal fertilizer.
4 – 5 weeks after germination, top dressing should be done. CAN is used or some basal fertilizer rich in Calcium, Boron and Nitrates, which should also be mixed with HUMIPOWER at a rate of 1 Kg of Humipower against 50 kg of basal fertilizer
However, these basal fertilizers should be supplemented with foliar fertilizers because they have a wide range of nutrient elements which are very vital to the plants.
These foliar feeds include;
- OPTIMIZER 10 ml/20l– this is a stress manager, helps in boosting plant’s immunity, prevents flower abortion among other benefits and can be sprayed at any stage of the crop development. It contains both macro and micro nutrient elements.
- GOLDCHANCE SERIES 50g/20l – this takes care of the crop at the different stages of growth and development, e.g., Goldchance Super Start ( early crop development), Goldchance Super Flowers & Fruits (for flowering and fruiting/pod development stages).
Weed Control
Weeding should be done in order to avoid losses attributed to weed infestation. This is because they compete with the crop for nutrients, water, space, among others, as well as harboring pests and diseases.
- CATAPULT 480SL 10 – 15 ml/l is used to kill all types of weeds during land preparation, or even just before germination. This helps in reducing the development of weeds, even throughout the crop season.
- BENTAGRAN TOP® 240EC 2.5 ml/l is a post-emergent herbicide for control of annual weeds in beans fields and French beans fields.
Before flowering, weeding is essential.
NOTE; whenever doing any foliar spray, the product (insecticide, fungicide, foliar feed or herbicide) should be mixed with INTEGRA 3ml/20l. This is a sticker, spreader, wetter and penetrant, which improves the efficacy of the product.
MATURITY, HARVEST & POST-HARVEST HANDLING
Depending on the various varieties, beans are ready for harvesting 70 – 120 days after sowing. Others take shorter periods. At maturity, the plants have matured and leaves turned yellowish to brown or fallen.
Beans can be harvested green or when dry.
For dry harvesting, pods are harvested when completely dry. However, if they have withered but are still moist, they can be picked and sun dried. Plants can also be uprooted if most of the pods are ready for harvesting.
Pods that are completely dry split open, exposing the dried beans, which is a risky time for harvesting so some good timing is necessary.
Dry beans are stored in treated gunny or PICS bags which help to prevent major damages caused by storage pests. It is advisable to incorporate the seeds with an insecticide, e.g. Actellic Super to prevent damages while in the store by pests. Bags should be placed on pallets, not directly on the floor.
Green beans can be refrigerated for 8 – 10 days while dried beans can be stored in a cool, dry place for up to a year or more.
