5 common Sukuma Wiki diseases And Control (Diseases In Kale)

Kales are quite the hardy crops in my experience. You will note that they do not succumb easily to sukuma wiki diseases when you feed them well. However, there are cases where even the strongest ones will fall. Such cases mainly occur when the kales are stressed either from water, nutrients, or diseases.

Common sukuma wiki diseases that affect kale are black rot, powdery and downy mildew, dry rot canker, and ring spot. Rust, mold, and damping-off are rare and do not have significant damage but you should not be surprised if you find them.

Black rot

Black rot is among the common sukuma wiki diseases that affect kale during rainy seasons when there is a lot of moisture in the air. It is caused by bacteria that is usually carried by infected seeds but you can get it from infected plants neighboring your farm.

The ideal weather conditions for black rot are 20 degrees to 29 degrees Celsius and moisture in the air, such as rain. You might notice a surge in cases during these periods especially if you crowded your kales in one place not spacing them enough.

Crowded plants create a conducive environment for infection and the spread of infection because:

There is restricted airflow between the leaves, which dries them. Wet leaves harbor bacteria, fungi, and other plant pathogens.

Once you have a black rot infection on your kales, the quickest remedy is to pick or cut off the infected plants and throw them away in a dumpsite far from the farm where they can be burnt.

Symptoms of black rot

You will notice the leaves turning yellow. The yellowing also presents itself as v-shaped lesions staring at the leaf margin moving inwards on bigger plants. In the nursery, seedlings become yellow and drop their lower leaves. In some cases, the seedling dies.

As the disease progresses or moves onto mature leaves, the veins inside the lesion become distinctly black. The infection grows until it kills large areas of the affected leaves.

If you cut a cross-section of an infected stem of an infected plant, you will see a black ring.

Controlling black rot

  • With plant diseases, the first line of defense is buying quality seeds that are tolerant to sukuma wiki diseases. Always confirm that whoever is supplying you with seeds is genuine and the seeds are certified, so you do not run into problems.
  • Practice good hygiene when you handle your crops. For example, you should sterilize your tools as you move from one plant to another and one crop to another. You should also have a foot bath where you sterilize your feet before getting into the farm.
  • A two-year crop rotation program is the best, but depending on the land size, this can be reduced to around 8 to 12 months.
  • You can spray fungicides when you notice the first symptoms.

Read more: Common sukuma wiki pests (kales) and how to control them

Dry rot canker

Dry rot canker also comes from infected seeds but can also be carried from infected tools, plants, and crop debris into the farm.

Sukuma wiki diseases

You will see light brown spots which may be circular and later develop ash grey centers with many black spots.

In the case of severe stem infection, results in a dark dry rot above the soil line which extends below and kills the roots.

The disease spreads fast. You might find some plants abruptly wilting and then dying.

Controlling dry rot canker

  • Use certified seed and provide field sanitation and hygiene.
  • Crop rotation is also advised to keep the disease at bay. A 3 to 4-year crop rotation is a good enough interval.

Ring spot

Ring spot in kales is caused by fungi. The spores of the fungi are brought in by wind from other infected areas. So another critical source to watch out for is infected compost.

The first symptom to look out for is circular brown-grey spots on the leaf surface. These are bordered by a green margin and concentric zones with black specks.

Controlling ring spot

  • Buying certified seeds and practicing hygiene
  • The crop rotation program should take at least two years before you plant kales in the same area again.
  • You can apply a fungicide with copper oxychloride as the active ingredient. Remember to read the instructions on the label for the pre-harvest index, among other recommended practices.

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    Downy mildew

    Downy mildew is a fungal disease that affects kales during wet and moist seasons. The fungi grow from spores that are very light and tiny. The fungal spores can be carried by wind or washed by rain from one infected area.

    Downy mildew

    Overhead irrigation can also contribute to disease spread on your farm. It is because overhead irrigation, like rain, will wet the leaves. Wet leaves are the perfect environment for the fungal spores to germinate and grow.

    While scouting for downy mildew, you should look under the leaves. If downy mildew is present, you will see a fluffy growth which will produce black spots on the top side of the leaf in advanced stages.

    Controlling downy mildew

    Space the plants at 60 cm between rows and 40 cm between plants. Observe good hygiene from the nursery to the main field. Rotate your crops regularly, giving the land about two years. You can spray a fungicide with mancozeb as the active ingredient if you have to.

    There are other options as well if ask your local supplier. Remember to follow the instructions on the label always. These control measures also work with powdery mildew disease that you will read next.

    Powdery mildew

    This is also a fungal disease spread by wind, rain, and overhead irrigation just like downy mildew above. Therefore, you will most likely encounter it when the climate is warm and dry. You will notice white powdery spots starting to form on the farmers’ lower and upper leaf surfaces.

    When left unchecked, your kale leaves will start turning yellow and die, after which they are likely to fall off the plant.

    Adequate spacing between crops for good airflow

    Use fungicides sparingly.


    Diseases in kales are not such a big deal. There is no need for you to worry now that you have these tips at your disposal. You can quickly correct them through hygiene, buy certified seeds, and apply the correct fungicide, and your crops will be okay.

    Read More

    9 Strategies for Disease Management in Kales (Sukuma wiki) on the Farm


    1. Hi
      I am in the process of starting vegetable farm in Uyoma area.
      I intend to do drip irrigation since i have a borehole.
      I need to have a one to one chat with you for advice.
      Call me on 0721381581

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