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Increasing yields: How to control common diseases in potatoes

By Grace Chomba

Emily Chebeya harvests Irish potatoes from her farm in Endebess Sub-County. [Harold Odhiambo, Standard]

Potato farming is a profitable venture with a luring potential of two to three harvests in a year.

According to experts, the farming thrives in highland areas with temperatures ranging from 20 to 30 degrees.

Despite being a lucrative venture, farmers always face low production and shrunk profits, often due to disease infestations such as bacterial wilt and late blight disease.

Here are some of the way to control common diseases and ensure a bumper harvest:

Bacterial wilt

It is a soil-borne disease that spreads through infected seed, water, soil, arming tools, livestock and people. It can cause stunted growth in plants.

The disease leads to rapid wilting and death of the plant without the leaves turning yellow or spotting.

The plant stem inner section will turn dark brown and when the potato is cut into half you will notice black or blown rings which display a thick white fluid when squeezed.

Solution – Crop rotation is advised. Experts say you should opt for varieties unrelated to potatoes such as maize or beans.

You should also clean farm tools thoroughly before and after use, uproot all infected plants and tubers and burn them and avoid planting in waterlogged areas.

Late blight

It is a fungal disease that attacks plants after they get foliage. It causes lesions in lower leaves around the leaf margins which enlarge and spread fast in humid and cloudy weathers. As the leaves start rooting the lesions turn black or dark brown. The tubers will have purplish-brown lesions on the surface.

Solution – One should monitor the field twice a week as the fungal development is favoured by cool and moist conditions. Practice proper field sanitation by disposing of all infected potatoes after harvesting. Contact fungicides should be applied to the stems and leaves.

In advance, proper spacing and drainage can reduce the spread of the fungus.

Early blight

It is a fungal disease that mostly affects older leaves. It thrives on warm temperatures and humid conditions. Late blight and early blight occur at the same time in the field. The terms early and late are relative to the time of their infestation to the plant.

It causes brown lesions on older leaves which are dry and may develop brown-black circular to oval areas. The leaf may turn yellow at the edge of the lesions. The potatoes get dark with circular to irregular spots and sunken lesions might appear.

Solution- Keep the plant healthy and disease-resistant through watering and fertiliser application, avoid overhead irrigation, planting disease-resistant and early maturing varieties, practice crop rotation and apply foliar fungicides. During harvesting, avoid bruising mature potatoes.

Verticillium wilt

It is a soil-borne disease that causes the leaves vein to start yellowing immediately after flowering. The areas between the leaves and leaf edges turn yellow and later brown. The stem will remain upright as the leaves wilt and when cut a grey-brown discolouration will be seen on the lower stem.

Solution – Soil testing helps to detect the fungus present in the soil as the disease symptoms might be mistaken for early maturity. Monitor the fields twice a week and check brown discolourations on the wilted planted stems. Crop rotation with non-susceptible cereal crops is advised with one also implored to control host weeds and avoid over-irrigation.

Other diseases include bacterial soft rot that leads to rotting and foul odours during storage, common scab and Fusarium Wilt. The diseases can be controlled by practising crop rotation, planting certified seeds and maintaining proper farm hygiene.

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