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Posted 01/19/2021 in Agricuture by Wallace Mukoka




The scientific name is (Phaseolus Vulgaris)

Green beans are the unripe, young fruit of various cultivars of the common bean (Phaseolus vulgaris)Beans are classified into two distinct groups:

1. Bush or dwarf beans

2. Runner or pole beans

Climate and Soils

A relative humidity of not less than 50 percent is required for good setting, although dry, cool conditions are required for harvesting. Best yields are obtained on sandy clay loams. The optimum soil temperature range is between 25 and 30 degrees. Soils which tend to become waterlogged should be avoided as water logging causes flower and pod drop. Optimum soil pH is 5.0-5.5

The recommended planting times are as shown below. Liming where soil pH is below 5.0 is advisable. Below 750m altitude-sow March, April and May 750m-1200m altitude-sow early September to March Above 1200m altitude-sow mid end September to early November and end of February

Fertiliser Requirements

The general recommendations for fertiliser application are a basal dressing of 600 kg/ha. Compound D and a light top dressing if required of ammonium nitrate at 100 kg/ha. The fertiliser must be banded at least 75 mm to the side and 75 mm below the seed rather than broadcasting the fertiliser. Boronated fertilisers should be avoided as beans are susceptible to high levels of boron.


Seed should be sown at a rate of 80—100 kg/ha, and the seed should be treated with thiram and dieldrin to protect against attack by soil-borne fungi and the stem maggot. Bush beans are planted in situ at a spacing of 50 mm x 450 mm.

Double rows 200 mm apart and 700-750 mm apart in the row is more convenient for mechanisation. Runner beans are planted 100-150 mm apart, in rows 900mm apart. Planting depth should not exceed 25 mm.

Beans should be planted in a soil that has been ploughed to a depth of 200-300 mm, and before seeding; the soil should be brought to a reasonable tilth and irrigated.

Weed Management

Weed control should begin shortly after germination of the seeds.

Cultivation must be shallow since most of the roots are in the top 200 mm of the soil.

A number of herbicides are available for chemical weed control., examples of some are

1. Linuron (Afalon)

A pre-emergence herbicide applied at a rate of 1.5-2.5kg/ha.

2. Metalochlor (Dual)

Is another pre-emergence herbicide that is applied at a rate of 1.75– 2.0 litres for grass control. In areas where nutgrass is a problem, the rate is adjusted to 2.0-2.5 liters/ha.


Most of the roots of a bean plant are concentrated in the top 200 mm of the soil, therefore light irrigations are recommended, 35-40 mm (net) on fine textured or clay soils and 25-30 mm on light sands or coarse textured soils.


The first harvest occurs about 14 days after flowering and lasts from three to four weeks. The crop is harvested by hand when the pods are nearly full size, straight and easily snapped, and the seeds small with a jelly substance surrounding them.

Beans are ready for the first harvest about 50 days after planting and this continues for 21 to 30 days. Beans must not be harvested during the hottest time of the day, and after rain or irrigation, should be allowed to dry before picking. Green Beans usually give yields of 8-10 tonnes/ha.


1. Rust which is (Unronyces appendiculus)

Characterised by brown pustules on lower leaves with yellow halo of variable size. It is controlled by Mancozeb 80% at a rate of 300g/100 litres of water or Maneb 80% at a rate of 200g/100 litres of water.

2. Anthracnose (Colletotrichum lindemuthianum)

It is characterised by circular sunken brown pits on the pods containing pink spores.

It is controlled by ;

Mancozeb 80% at a rate of 300g/100 litres of water.

Maneb 80% at a rate of 200g/100 litres of water

Thiram 80% at a rate of 200g/100 litres of water

Zineb 80% at a rate of 200g/100 litres of water.

3. Bacterial blight (Pseudomonas midicagiu)

It is characterised by small spots with yellow green halos on the foliage, pods and seeds.

It is controlled using Copper oxychloride at a rate of 400g/100 litres of water.


Other diseases that can attack beans are scab, pre-emergent damping off and bacterial pustules.


1. Aphids (Aphis fabae)

Aphids are sap sucking insects that transmit viruses. They are controlled using Dimethoate or Malathion 50% or Endosulfan 35%.

2. Bean stem maggot

This is a small cream maggot that burrows through the stem forming swellings.

It causes yellowing of the foliage and plant wilt. It is controlled using Dieldrin

3. Heliothus bollworm (Heliothus armigera)

The heliothus bollworm hollows out the plant buds. It is controlled using Endosulfan.

4. Loopers

These are green caterpillars that eat the leaves and the pods.

They are controlled using Carbaryl 85%.

5. Red spider mite

The Red spider mite makes fine webbing on the under surface of the leaf leading to the leaves turning to a silvery colour and mottling of the leaves. It is controlled using Malathion 25%.

6. CMR Beetles

These are large clumsy black beetles with yellow and red markings.

They are controlled using Malathion 50%.

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Author; Wallace Mukoka

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