FRENCH BEANS FARMING

French beans are a major export crop in Kenya whose local consumption is gradually being adopted. The crop is popularly grown by both large and smallholder farmers. French beans are immaturee green pods which are referred to as snap or green beans.one acre yields 4 tons of french beans at average selling price Ksh 60 per kilo, farmers will  earn Ksh 240,000 by the end of the harvest period.French beans are recommended to be grown on small scale with staggered planting due to its intensive labour requirements. It is cultivated both for fresh consumption and processing mainly canning and freezing. The optimum temperature range for growing French beans is 20-25ºC and an altitude range of 1,000-2,1000M.Rainfed cultivation is possible in areas with well distributed medium to high rainfall of 900-1,200 per year, but supplementary irrigation is required to maintain continuous production during off season. French beans performs best on well drained silty loams to heavy clay soil high in organic matter contents with slightly acidic to slightly alkaline PH of 6.5-7.5

The major growers in Kenya are small farmers. The French beans are grown mainly for export purpose and are produced largely near the city of Nairobi where the altitude is between 1 000 and 2 000 meters above sea level and where soil is well drained and rich in organic matter.

French beans are among the major horticultural crops produced in Kenya for export. The export season of French beans is from November to April. The farmers visited used irrigation water for production. About 50 mm of water per week was applied using an overhead or furrow system of irrigation. The overhead system of irrigation, however, was comonly used.

The farming of French beans is labor and capital intensive. The costing of the inputs such as fertilizers, seed, labor for land preparation and harvesting were estimated. Between 20 to 25 kg of seed per acre (49.4 – 61.8 kg/ha) was used, costing about Kshs 32 for 60 kgs; land preparation was about Kshs 500 per acre (Kshs 1 235.5/ ha). The price for fertilizer for one acre was Kshs 500 (Kshs 1 235.5/ha). The total variable cost was about Kshs 4 670 per acre (Kshs 11 539.6/ha). Gross margin per acre was 16 530 Kshs (Kshs 1 309.6/ha).

The estimated labor input on large, mechanized farm for French beans amounts to 3 283 mh/ha. The harvesting, which include picking, selecting and packing approximately 1 300 cartons for export required the highest labor with 3 030 mh/ha; canning, 100 mh/ha; irrigation, 80 mh/ha with 20 applications; weeding, 35 mh/ha; spraying, 14 mh/ha; top dressing, 9 mh/ha and planting, 7 mh/ha. The average yield was between 600 to 1 000 cartons of 3 kg/acre (1 482.6 – 2 471.0 cartons/ha).

A good majority of the farmers estimated a profit of about 25 per cent but considered employment it provides for them and the rural people a very important benefit.

Varieties & Ecological Requirements

Varieties

The main varieties grown in Kenya are
Monei, Amy, Samantha, Teresa, Julia, Vernando, Bronco, Coby, Espadia, Bakara, Claudia, Tokai, Pekera, Super Monel, Morgan, Paulista, Cupvert, Gloria, Tonivert, Rexas.
The market requires freshy, straight, long, rounded in cross-section beans

Ecological Requirements

• The optimum growing temperature range from 20-25°C. Beans have been grown in temperatures ranging between 14-32°C. Extreme temperatures result to poor flower development and poor pod set.
• The optimum altitude range between 1,000 - 2,100m a.s.l. French beans mature faster in warmer areas.
• For rain fed cultivation, well distributed medium to high rainfall (i.e. 900-1,200mm  p.a.) is required
• Well drained loams to heavy clay soils, high in organic matter contents.
• PH 6.5-7.5 but plants can tolerate up to pH 4.5
• Crop rotations helps to control weeds, discourages diseases, protect soil from erosion, reduce insect populations, and rejuvenate soil organic matter a valuable source of nitrogen. Grass/maize- legumes recommended as it accumulates much organic matter. Should not be grown more than once, or twice at most on the same land without other crops being grown in rotation.
• Seed rate: partly determined by variety but 30kg per acre planting rate of 1 kg per 100 ft of 36-inch row will result in seed  spacing of about 3 inches. Beans rows should be on the contours or at least parallel to the slope to reduce soil erosion.

Propagation

Seed Acquisition and Treatment

Use certified seeds from reputable seed agents. Normally the produce buyers supply seeds to their contracted farmers. Should seeds come from other sources they should be disease free and well sort.    Before planting, the seed should be dressed with Fernasa-D (combination of Lindane and Thiiram) at the rate of: 3g (i.e. 2 flat teaspoons) per kg. of seed.

Manure Application

Application of 10 tons Farm Yard Manure per hectare is recommended, especially where soils are low in organic matter content.  Manure should be applied in planting furrows and worked into soil before planting.

Fertilizer Requirements

At planting:
200kg D.A.P per hectare should be applied during planting.  The fertilizer should be applied in the planting furrow and mixed thoroughly with the soil before placing the seed.

Top dressing:
Apply 100kg C.A.N per hectare at the first ‘three leaves’ stage, and another 100kg per hactare at the onset of flowering.

Foliar Feed:
Foliar feed such as Bayfolan or Rapid-grow, should be applied fortnightly, from the forth week after planting to the middle of podding phase.

Field Establishment

Growing Season:
Planting starts at the on set of rains.With irrigation, French beans can be grown all year round but the main export season is from October to May. Sowing should be scheduled such that most of the crop is ready between October to mid December, and from mid-January to end of May.

Planting Schedule:
To maintain continuous production, planting should be staggered at 2-3 weeks intervals in conveniently sized plots.

Spacing:
Beans should be sown in single rows of 30 by 15cm, (1 seed per hole); or double rows 60 by 30 by 10cm. It is advisable to plant in blocks of four single rows, separated by a path of about 50cm, for ease of management.

Seed Rate:
One hectare takes a total of 50-60 kg of bean seed.
French beans are sown directly into a well prepared seed bed.

Picking time:

In warm areas, beans take 45 to 50 days from planting to first picking.

Irrigation

Regular water supply is essential as moisture affects yields, uniformity and quality.  It is advisable to grow the beans on ridges and use furrow irrigation in heavy clays. This is because beans are very sensitive to water logging.

• To maintain a continuous production especially during the off-season, irrigation is essential.
• It is recommended to apply 35 mm/week at planting to 10 days post emergence and 50mm/week thereafter to flowering stage.
• Water could be applied through furrow or overhead irrigation.

Mulching

Mulching helps establishment under wet conditions because young bean seedlings are prone to fungal infection caused by soil splash

Weed control

Timely and thorough weeding is absolutely essential.  The first weeding should be done 2-3 weeks after emergence. Second weeding should follow 2-3 weeks later. Care should be taken to avoid damaging the shallow roots especially during the first weeding. Crops should not be weeded at flowering time and when the field is wet to avoid flower shedding, spread of diseases and soil compaction. Use of herbicides could be economical for the commercial French beans grower.  The following pre-emergence herbicides can be used: -.

• Lasso 4 EC (Alachlor) at 3 Litres in 400 litres of water per hectare
• Stomp (Pendimethalin) at 2.5 Litres in 400 litres of water per hectare
• Basagran (Bentazon)     can be applied post-emergent at 2.5-3lts/ Ha for control on broad-leaved weeds.

est and Weed Control

Root Knot Nematodes

root-knot (Meloidogyne ssp.), lesion(Pratylenchus spp), sting(Belonolaimus spp.), stubby-root( Trichodorus spp.) and cyst (Heterodera spp.). Roo-knot is probably the most common nematode and causes the most damage.

Symptoms.
These attack roots causing lesions, root galls or swellings, plant stunting and wilting of severely infected plants.  The     Lesions also serve as entry points for Bacteria and fungi. Affected plants are dwarfed and have distorted leaves.

Control

• Crop rotation with non-susceptible crops such as maize and grasses.
• Good weed control to remove weeds which are also hosts to the Nematodes.
• Leaving fallow infested fields during dry  weather.
• Soil application of 5 gm/m² Mocap at planting, or 6-10 gm/m2 Ethoprophos, 2-3 times a year.

Bean Fly

(Ophiomyia spp, Phorbia spp)

a. Symptoms
The adult is a small 2 winged insect which can be seen resting on leaves where it lays the eggs.  The damage is caused by the larvae which mine the stem. The larvae also feed on the cotyledons of seedlings before or after emergence.    Affected plants are yellow, stunted, and stems are cracked at the soil level
b. Control
Spray with chemicals such as:

• Cypermethrine at 100ml/20lt at 7 days intervals,
• Fenvalerate at 100ml/20lts at 7 days interval.
• Karate and decis could be applied in the stages that follow through the harvesting period, at weekly intervals.

Treat soils with chemicals such as:

• Triazopho, at 30-60 ml/100lt, at 10-14 days intervals, or
• Chlopyrifos at 150ml/100lts. At 7 days intervals.
• For Triazophos and chlopyrifos, allow 21 and 7 days pre- harvest interval respectively.

Seed treatment with chemicals such as: -

• Imidacloprid at 570gm/100kg of seeds.
• Cypermethrin at 100 ml/20L At 2 weeks intervals
• Fenvalerate at 100ml/20lts at 7 days intervals.

Bean Thrips

(Megalothrips Spp)

a. Symptoms.
The damage is caused by the nymphs  and adults which feed and puncture flower structures.
b. Control

• Foliar spray before crop flowering
• Apply Karate Decis or Ambush CY during flowering

Aphids

(Aphids fabae)

a. Symptoms
Aphids cluster on plant stems, leaves, and bean pods. They suck plant sap and cause the plants to stunt.
b. Control

• Chemical sprays as for bean fly above.

Red Spider Mites

(Tetranychus Telarius)

a. Symptoms
These are tiny organisms also known as red     spider mites, since they are in the same group as spiders.  Their main damage is on the leaves    which turn silvery and brownish in colour. Infested leaves have cobwebs on the lower leaf surface.
b. Control

• Weed control to remove alternate hosts.
• In severe infestation, burn the bean straw.
• Spray with chemicals such as Kelthane (or Dicofol), Cabaryl, Dimethoate, Tedion (or Tetradifon 18% E.C). The safety period for Kalthane is 7 days, while. for the others it is 14 Days.

Cutworms, Beetles and Caterpillars

(Agrotis Spp, Astylus spp Rutelinae spp)

a. Symptoms.
These are active at night and hide during the day. They cut stems of young plants above or below soil level. They also feed on plant foliage.

b. Control.
Treat soil with chemicals such as:

• Chlorpyrifos,, at 150150ml/100lts, at 7 days intervals. Observe 7 days pre-harvesting interval.

Foliar spray using chemicals such as: -

• Deltamethrin, at 30-50 ml/20lts, at 7-10 days interval and 7 days pre-harvest interval.
• Cabarl, at 50gm /20lts, at 15 to 21 days intervals and 14 days pre-harvest Interval..
• Malathion at 30-35ml/20lts and 14 days pre-harvest interval.
• Fenitrothion at 40 ml/20lts. (14 days intervals, 7 days pre-harvest interval).

American ballworm

(Heliothus armigera)

a. Symptoms
The larvae bores holes in flower buds and young maturing pods. Pods either fails to form or don’t develop to maturity.
b. Control

• Foliar sprays with Bestox, Thuricide, Desis.
• Physical removal

Weed control

Timely and thorough weeding is absolutely essential.  The first weeding should be done 2-3 weeks after emergence. Second weeding should follow 2-3 weeks later. Care should be taken to avoid damaging the shallow roots especially during the first weeding. Crops should not be weeded at flowering time and when the field is wet to avoid flower shedding, spread of diseases and soil compaction. Use of herbicides could be economical for the commercial French beans grower.  The following pre-emergence herbicides can be used: -.

• Lasso 4 EC (Alachlor) at 3 Litres in 400 litres of water per hectare
• Stomp (Pendimethalin) at 2.5 Litres in 400 litres of water per hectare
• Basagran (Bentazon)     can be applied post-emergent at 2.5-3lts/ Ha for control on broad-leaved weeds.

Disease Control

Rust

a. Causes
The disease is caused by the fungus Uromyces appendiculatus. This is a very serious disease to French Beans and other food beans.  The Development of the disease is favoured by high humidity conditions.

b. Symptom
The disease is recognized by the presence of slightly raised, small white spots, on the surface of the lower leaf. The spots turn red to dark brown after a few days.

c. Control

• Crop rotation
• Use of tolerant varieties.
• Chemical sprays such as: Baycor 30% EC , Bitertanol, Anvil, Alto 100  SL,  or Dithane M45 should be applied after every two weeks.

Angular Leaf Spot

a. Causes
This is a fungal disease caused by Phaeoisariopsis griseola.

b. Symptoms
Leaves, stalks, and pods have angular brown or red coloured spots with purple edges and grey to brown centres. The leaves may then fall prematurely.

c. Control

• By use of healthy, certified seeds.
• Treat Seeds using chemicals such as  fernasan-D, at 3gm per kg of seed.
• Spray with chemicals such as benomyl (or benlate)

Root Rots

(Quintozene)

a. Causes
These are fungal diseases caused by the fungus Rhizoctonia spp, Pythium spp Sclerotium spp etc.

b. Symptoms
Affected plants show yellowing and drying of stem at soil level. Stunting may also occur.  The crop may also show poor seedling establishment, uneven growth, chlorosis and premature defoliation of severely infected plants.

c. Control

• Seed dressing with a chemical such as: Fernasan-D , at 3gm per kg of seed, or Quitozene.
• Drenching with chemicals such as: Brassicol (or Quitozene), Benomyl (or Benlate), or Bavistin, during the vegetative stage.

Bacterial Blights

a. Causes
The condition is caused by Pseudomonas Phaseolicola and Xanthomona phaseoli . It is a serious disease for beans in Kenya, especially in cool and wet areas. The disease is spread through splashing from exuding lesions and plant debris.

b. Symptoms
Plants show ring-like spots on the leaves, drying of leaf margins, yellowing and water soaked pods.

c. Control

• Use of certified seeds.
• Roguing and destruction of affected plants.
• Crop rotation.
• Chemical sprays using copper based fungicide such as: kocide 101.

Anthracnose

a. Causes
The disease is caused by a fungus known as Colletotrichum lindemuthiamum. The fungus is seed-borne and affects all
aerial plant parts.  It is spread by rain splash, wind or mechanical contact. The disease usually occurs in cool, damp weather.

b. Symptoms
The disease is characterised by appearance of sunken, brown spots with black edges on pods; angular brown sports on leaves; and oblong stripes on stems.

c. Control

• Use of certified seeds.
• Field sanitation.
• Crop rotation.
• Use of resistant varieties.
• Foliar sprays using chemicals such as: Benomyl, Mancozeb, propineb.

Bean common Mosaic Virus (BCMV)

a. Causes
The disease is seed-borne and it is transmitted by aphids.

b. Symptoms
The symptoms of this disease vary with variety, stage of growth, and environmental factors.
They includes a mosaic (i.e. mottling, Curling and stunting of leaves,) systemic Necrosis and local malformations.  The leaves may roll, malform and general stunting of the pant.  The plant produces excessive number of Lateral shoots.

c. Control

• Use of certified seeds.
• Plant resistant varieties
• Rouging of infected plants.
• Control of aphid vectors using insecticides.

Powderly mildew

a. Causes
It is caused by a fungus known as Erysiphe spp.

b. Symptoms
Attacks stems,leaves,flowers, and pods which appear covered with white powdrerly growth which turn black latter. In severe cases the leaves turn yellow and drop off.

c. Control

• Field hygiene
• Crop rotation
• Chemical fungicides eg. Dithane M45, Antracol, Bayleton

Downy mildew

a. causes
Caused by afungus known as perenospora spp.

b. Symptoms
The underside of leaves exhibit white to greyish growth which later cover whole leaf surface.

c. Control

• Field hygiene
• Crop rotation