FRENCH
BEANS (Phaseolus vulgaris)
French
beans are immature green pods which are referred to as snap or green beans. The
beans are a major export crop in Kenya whose local consumption is gradually
increasing. The crop is grown by both large and smallholder farmers.
The pods vary in colour, depending on cultivar. The growth habit is both dwarf
and climbing type.
The beans are grown for both fresh consumption and processing (mainly canning
and freezing). French beans containing protein, fat, calcium, iron, phosphorus,
vitamins A, B, D and starch.
Marketing
A major outlet for these French beans is the European Union market. The export
market in Kenya falls into two major seasons:
The low demand season runs mostly from June to September every year. It is
characterized by lots of supply from those who produce with the long rains and
low demand from the EU market as they can produce their own by then.
The high demand season usually runs from September to around March. During this
period, EU markets are faced with winter and their only option is to import and
that is when Kenyan farmers benefit from production.
Ecological
requirements
Altitude
The most suitable areas for the production of French beans fall within the
lower Midland to Lower Highland zones at altitudes between 1500-2100m above sea
level.
Rainfall
Rain fed cultivation is possible in areas with well distributed, medium to high
annual rainfall of 900-1,200mm per annum, however to maintain continuous supply
especially during the off-season, irrigation is essential. Up to 50mm of water
per week is required.
Soils
French
beans can grow in a wide range of soil types, ranging from sandy, and loam to
clay. They however grow best on friable (easily crumbled), silty loam to heavy
clay soils which are well drained high in organic matter. The optimum soil pH
is 6.5 to 7.5, but beans can tolerate a low pH of up to 4.5.
Below pH
4.5, plant growth is impaired through limitation of development of the
Rhizobium bacteria that are responsible for the nitrogen fixation in the galls
formed on the bean roots. It’s advisable to carry out a soil test before
planting.
Temperature
French beans can grow in temperatures range for production is 14-320 C
depending on the variety. The optimum temperature for production is 20-250 C.
Extreme temperatures result in poor flower development and poor pod set.
Seedlings will not tolerate temperature lower than 100C.
Varieties grown in Kenya
There are various varieties grown mainly for the export market. Production is
determined by market preference. The varieties includes: Amy, Teresa, Samantha,
Julia, Paulista, Vernando, Serengeti, Cupvert, Tokai and Bakara, Monel, Gloria,
Claudia, Morgan, Amy coby, espada, Maasai and Nerina.
- Varieties for fresh market:
Amy, Pekara, Teresa, Paulista, Rexas, Samantha and Cupvert.
- Varieties for Processing:
Julia, Vernandon and Sasa.
Planning
production
To venture into French beans production, it is important to get a reliable
market first and then produce as required by the market outlet.
French beans production can be labour intensive especially during harvesting
thus it require adequate provision for labour.
Pest and diseases can be a problem in production hence provisions for crop
protection chemical should be made in advance
Planting
season
Planting should be scheduled so that most of the crop is ready between October
to mid December and from mid-January to end of May. From mid December to mid
January the demand is low because of the holidays.
In warm areas, beans take 55-60 days from planting to first picking, hence,
plant from mid-August to mid-October, then plant again early in December.
Land
preparation
French beans are sown directly into the seed bed. The land should be ploughed
and harrowed properly just before planting
Planting
With irrigation, French beans can be grown all year round but the main export
season is from October to May.
Spacing
Single rows 30 x 15 (1 seed per hole) or double rows 60 x 30 cm may be used.
The spacing will depend on the variety, soil fertility, water availability as
well as climate. It is advisable to plant in blocks of about 4 rows separated
by a path of about 50 cm. The seed rate required is, 25-60kg/ha (10-24kg/acre)
of certified seeds depending on the variety.
Fertilizer and manure application
- Apply 200 kg/ha (80kg/acre)
DAP along the rows before planting. Contact between fertilizer and seed
should be avoided by mixing the fertilizer thoroughly with the soil in the
planting furrow.Apply 150-kg/ha (60kg/acre) Calcium ammonium nitrate
(CAN), as a top dressing in a split application. First split is applied
when 2-3 leaves appear and the second at the beginning of flowering.
- Excessive nitrogen should be
avoided as it may promote vigorous vegetative growth at the expense of pod
production.
- Foliar feeds are recommended
to boost crop development and production. The choice of the fertilizer
depends on the fertility of the soil and variety requirements.
- Use of farmyard manure is
also recommended especially where soils are low in organic matter e.g. on
the heavy clay and sandy soils. It should be applied in planting furrow
and worked into soil before planting at the rate of 10 tons/ha
Note1 kg of
seed requires 4-8 kg of fertilizer depending on the variety and soil conditions.
Crop
rotation
This practice is recommended to avoid pest and disease build up. Rotation is
mainly done with cassava, maize, sorghum or any other non leguminaceae family
member crop.
Weed
control
- Timely and thorough weeding
is absolutely essential. The first weeding should be done 2-3 weeks after
emergence followed by a second weeding 2-3 weeks later.Care should be
taken to avoid damaging the shallow roots especially during the first
weeding.
- The crop 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 may be
economically feasible for the commercial French beans grower.
Pre-emergence herbicides such as: Lasso 4 EC( Alachlor) and Stomp
(Pendimethalin) can be used
- Basagran (Bentazon)-Can be
applied post emergence for control of broad leaved weeds
Irrigation
- Constant
supply of water is very essential because soil moisture affects yield,
uniformity and quality of French beans.
- Water
stress during flowering and podding causes flower abortion and curved pods
leading to reduced yields.
- French
beans are also very sensitive to waterlogged conditions. Therefore, where
the soils are not well drained such as the black cotton soils, it is
advisable to grow them on ridges. In such soils, furrow irrigation with
the beans planted on the ridges is a better practice than the common
system of basin irrigation. Either furrow or an overhead system of
irrigation may be used.
The
irrigation regime below is based on crop water requirement at various stages of
growth as well as the soil and weather conditions. The recommendation is as
follows:
1. Planting to 10 days (Post emergence) apply 35 mm per week
2. 10 days Post emergence to flowering blooms apply 50 mm per week
3. At Podding stage apply 35 mm per week.
Supporting
French beans
The climbing variety which grows to about 1.8m (6ft) high needs to be
supported. This variety requires trellises, poles, or other means of support at
least 200cm (8ft) high.
Pests
Root Knot
Nematodes
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 nematicides
Bean Fly (Ophiomyia
spp, Phorbia spp)
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
Control
Spray with recommended insecticide
Bean
Thrips (Megalothrips Spp)
The damage is caused by the nymphs and adults which feed and puncture
flower structures.
Control
Foliar
spray before crop flowering with recommended insecticides
Aphids (Aphids
fabae)
Aphids cluster on plant stems, leaves, and bean pods. They suck plant sap and
cause the plants to stunt.. Control-As for bean fly above.
Red
Spider Mites (Tetranychus Telarius)
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.
Control
Weed
control to remove alternate hosts.
In severe
infestation, burn the bean straw.
Spray
with miticide
Cutworms,
Beetles and Caterpillars
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.
Control.
Treat
soil with recommended chemicals
American
ballworm (Heliothus armigera)
The
larvae bores holes in flower buds and young maturing pods. Pods either fails to
form or don’t develop to maturity.
Control
- Foliar sprays with
recommended insecticides
Diseases
Rust
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.
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.
Control
- Use
of tolerant varieties.
- Chemical
recommended fungicides
Angular
Leaf Spot
This is a fungal disease caused by Phaeoisariopsis griseola.
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.
Control
- By
use of healthy, certified seeds.
- Treat
Seeds using recommended fungicides
Root Rots
These are fungal diseases caused by the fungus Rhizoctonia spp, Pythium spp
Sclerotium spp
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.
Control
- Seed
dressing with a recommended fungicide
- Drenching with recommended
fungicide during the vegetative stage.
Bacterial
Blights
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.
Plants show ring-like spots on the leaves, drying of leaf margins, yellowing
and water soaked pods.
Control
- Rouging
and destruction of affected plants.
- Chemical
sprays using copper based fungicide
Anthracnose
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.
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.
Control
- Use
of resistant varieties.
Bean
common Mosaic Virus (BCMV)
The disease is seed-borne and it is transmitted by aphids.
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.
Control
- Plant
resistant varieties
- Rouging
of infected plants.
- Control of aphid vectors
using insecticides.
Powdery
mildew
It is
caused by a fungus known as Erysiphe spp. Attacks stems, leaves, flowers,
and pods which appear covered with white powdery growth which turn black
latter. In severe cases the leaves turn yellow and drop off.
Control
Downy
mildew
Caused by a fungus known as perenospora spp. The underside of leaves
exhibit white to greyish growth which later cover whole leaf surface.
Control
Harvesting
- Picking
of pods begins 6-8 weeks after planting, depending on the area and
variety, and continues for about 1-2 months.
- Clean
harvesting equipment should be used and workers should maintain personal
hygiene.
- The
pods are carefully picked and not pulled from the plants and should have
the stalk attached to them.
- Picking
should be at regular intervals, as per buyer specifications. Harvesting
may be done twice a week for the fine beans and three times a week for the
extra fine beans. This continues for around three weeks.
- Harvesting under rain or wet
conditions is not recommended. If this cannot be avoided, the produce
should be placed on a clean cloth, under shade, to dry before packing. If
the pods are soiled, they should be immersed in clean water and placed on
a clean dry cloth to dry.
Yields
- Yields
of 9 to 15 tons/ha are attainable. An acre of land should give you 6 tons
of French beans within 2 ½ months.
- 1kg
of seeds may produce 200-600 kg of produce depending on the variety and
crop management.
Post-harvest
handling
- The
harvested pods should be carefully placed in clean plastic containers and
protected from direct sun.
- The
containers should be covered with moist clean cloths (preferably white
cotton) to maintain low temperatures.
- In cases of soiled
pods, clean by immersing them in clean water and handle gently to avoid
bruises.
- The
pods should be taken to the grading shed (or put under shade) and sorted
out to remove broken, malformed, overgrown, off-types and insect damaged
pods.
Grading
- French
beans intended for marketing should meet the following minimum quality
requirements:
- Beans should be intact,
sound, of fresh appearance, clean and free from excess external moisture
- Beans
should be of specified size and of such a state as to enable produce to
with stand transport and handling so as to meet market requirements at the
destination.
- Extra
fine pods should be very tender, turgid, seedless, with no strings, and
free from any defects. The width of the pods (maximum diameter) should be
less than 6 mm and the minimum length of 10cm.
- The
fine pods may have small seeds and be short with soft strings, be turgid
and tender. The width of the pods should be between 6-9 mm while the
length of 12-l4 cm is recommended.
- Bobby
beans comprise beans of marketable quality which do not qualify for inclusion
in the higher classes but satisfy the minimum requirements specified
above. Beans should be reasonably tender and seeds should not be too
large.
- N/B:
In all grades, the pods should have the characteristic size and colour of
its variety.
Packaging, Pre-cooling and Transportation
- The
pods are packaged in corrugated fiberboard cartons of 3 kg gross weight or
in plastic pre-packs weighing 250,500 or 1,000gm.
- The
pods are pre-cooled to remove field heat. This is done at 7-80C (using
forced air coolers). The beans can be stored at 7 to 80C and a relative
humidity of 95-100% for up
- The
cartons should be carefully stacked during transportation to reduce
movement of cartons and allow free movement of air. Insulated or
refrigerated vehicles should be used for transportation of french beans.
Post
harvest diseases
- White
mold can infest pods just before harvesting and cause damage to the crop
during storage and transportation. This can lead to loss of an entire
shipment. The losses are highest at temperature between 18 and 240C.
- Hydro cooling of beans in
chlorine water after sorting and maintaining temperatures in shipping
container at 3.3-4.4 0C helps reduces the post-harvest losses.
Challenges
in production
- A
major setback is rejection of the produce if they do not meet the set
quality standards. (Harvest as per the buyers specifications of pods)
- Poor
disease and pest management can lead to poor quality produce
Advice to
Potential Growers
- With
continued demand for the beans being recognized, export companies are
going into contract farming with farmers. This involves setting of fixed
prices that run throughout the year whether the season is low or high.
- Due
to high labour requirements it is recommended that it is grown on a small
scale, possibly with staggered planting so that a manageable proportion of
the crop is ready for picking at any one time and that harvesting is
continuous. For instance, the land may be divided into convenient sized
plots (i.e. ¼ acre plots) and planted at 2-3 weeks intervals.
- Growing
these beans requires a lot of dedication and capital especially for the
high season. The most sensitive stages in production include; germination,
flowering, fruiting and harvesting.