Plant diseases to watch out for during the rainy season,guide for sukuma wiki, tomato and capsicum farmers

As rain drops, causing farmers to rejoice, most often than not it is short-lived as the wet season comes with a myriad of challenges; waterlogging and plant disease-most prevalent among the Brassica (Sukuma, cabbages, spinach ) and Solanaceae (tomato, capsicum/hoho, chili) family. Here are some of the plant diseases you should watch out for, and how to manage them.

Solanaceae family (tomatoes, capsicum)

Early blight

Commonly referred to as ‘baridi’ by farmers due to its prevalence in cold and rainy seasons. Early blight is characterized by black/brown circular spots on leaves that spread throughout the leaf causing it to wither. It has a knockdown effect on the fruits causing shrinking (fewer leaves means less food from photosynthesis) in addition to exposure to pests such as birds and sunscald.

Leaf infected with early blight.
Photo courtesy of


Blight is caused by a fungus thus a preventive spray during rainy periods will be effective, use preventive fungicides such as  Cosavet and Mancozeb. Once infected use curative fungicides like Milraz and Ridomil.

Additionally, wider spacing of plants-up to 60 by 60 cm between plants, and planting in raised beds could reduce the possibility of disease occurrence.

Downey Mildew

Characterized by an oval purple-grey growth on leaves that later turns pale and yellow before withering. Disease spread is accelerated in periods of leaf wetness and high humidity thus even in hot weather, sprinkler irrigation can cause the disease.

Leaf infected with Downey mildew.
Photo courtesy of


Apply preventive and curative fungicide sprays depending on how prevalent the disease is and also dictated by harvesting intervals when you are spraying preventively. Fungicides you can use include, Nimrod from Amiran, Pyramid, Actara from Syngenta, Mesural etc.

Make sure to alternate fungicides that have different ingredients to avoid the disease developing resistance.


Brassica family (sukuma wiki, spinach cabbage)

Bacterial soft rot

This is one of the most common diseases plaguing Sukuma wiki and cabbage farmers, characterized by a collapse of the plant stalks or head due to decay, a foul smell and flies can often be seen on the infected plants. The disease is easily spread from plant to plant through splashing of raindrops, knives, hands etc.


Bacterial soft rot has no effective chemical treatment, once infected, remove infected plants from the farm. Improve soil drainage by planting your sukuma wiki or cabbages in raised beds (one meter wide and 10 meters long). Additionally always clean farming tools after use.

Black rot

Very common disease in cabbages and sukuma wiki, the disease does not kill the infected plants but ruins the marketability of leafy vegetables from its characteristic yellow/light-brown wounds on the leaves.

Black rot disease
Photo courtesy of

It spreads quicker in areas where periods of rain and sunshine alternate, creating a warm and moist environment.


Prevention is key, once a farm is infected only crop rotation for up to three years will completely eliminate the disease. Do not overcrowd seedlings while in the nursery, space plants well when planting in the rainy season up to 60 by 60 cm apart, look for tolerant varieties, mulch your plants to prevent spread by soil splashing (the bacteria is sometimes hosted in the soil).

To fair well against bacterial and fungal plant diseases, prevention is better than cure, regular consistent practices such as cleaning of farm equipment, proper disposal of farm waste coupled with regular preventive sprays will keep your farm safe.


  1. I have started growing capsicum, they are on the nursery, now I believe that through the knowledge I have gotten, I’ll make it. Thanks


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