Beans are one of the major crops grown in the country both for subsistence and commercial purposes. In most regions, it is intercropped with maize.
According Stanley Nkalubo, a crop scientist at the National Crop Resources Research Institute (NaCRRI), beans take about three months to mature, depending on the variety. Below are some of the diseases and pests that affect the crop.
Rust
The rust is a fungal disease that is caused by Uromyces appendiculatus. The disease affects leaves, stems and pods.
It is most prevalent during the rainy season when the humidity is very high and is characterised by the presence of raised, small white spots on the lower leaf surface, which turn red to dark brown after a few days.
Infected pods develop red-brown powdery pustules surrounded by a yellow halo. This makes the pods to deform.
However, most symptoms are usually on the lower side of the leaf.
This disease usually spreads very fast and must be controlled quickly to avoid severe cases that result in the death of the plant.
Disease spores can easily be carried by wind, tools and equipment while carrying out routine management practices.
To minimise instances of the disease spreading, a border crop can be planted to act as a windbreaker.
Also, ensure all the tools are disinfected and work from the unaffected to the affected areas to avoid further spread of the disease.
Crop rotation with plants that are not highly infected such as broccoli and cauliflower also helps in breaking the disease’s life cycle.
Since the leguminous crops fix nitrogen, it is recommended to rotate them with brassicas since they require nitrogen for vegetative growth and are not affected by rust.
Anthracnose
The beans anthracnose is the most common disease affecting beans in Uganda. It attacks the lower parts of the leaves. Infected pods turn black which leads to poor seed development.
“Farmers must spray their gardens the moment they spot the signs,” says Nkalubo. The other diseases include bean blight, angular leaf spot and pythum root rot.
Cutworms
Cutworms are brown or black and are usually found in the soil. All the plant debris should be removed as this acts as a hiding place for the worms.
Chemicals can be used to prevent and control diseases and pests to avoid further spread. Other pests that affect beans include beetles, aphids and mites.
Farmers should avoid planting beans where nitrogen content in the soil is high since the crop has rhizobium, which helps in fixing the mineral in the soil. Excess nitrogen results in the plants being vegetative with few pods.
Timely weeding is critical as this reduces competition for nutrients, light and space. Regular water supply is necessary and is more critical during flowering to avoid flower abortion.
However, avoid excess watering to curb waterlogging, which causes the beans to turn yellow due to leaching of nutrients.
Beans do best in ridges or furrows. However, the spacing should be observed. After harvesting, thresh, dry and store in well-ventilated place for a longer shelf-life.
Bean stem maggots also damage the entire plant especially during the rainy season.
Farmers are advised to soil near the plants, mulching, chemical seed dressing with insecticide such as Endosufan, Acephate before planting to protect the seed.
How to plant beans
To plant beans, farmers must drill drainage holes at a spacing of 45cm between rows and 15cm from one plant to another. This is followed by application of DAP fertiliser.
