Notes to broadcasters
Cassava mosaic disease (CMD) is the most important viral disease of cassava in Africa. The disease reduces the size of leaves and disfigures them. Leaves of infected plants have a green and yellow mosaic pattern. Infected plants produce small roots, especially if they are infected early in the season.
The disease is caused by a virus, and transmitted from infected to healthy plants by insects called whiteflies. It is commonly spread by planting infected cuttings. There is no chemical control for the disease.
To manage CMD:
- Choose planting materials from virus-free stem cuttings.
- Uproot and bury plants that show symptoms of CMD as soon as recognized.
- Plant resistant or tolerant varieties.
- Practice intercropping with leguminous crops to decrease whitefly populations.
In this script, we talk to farmers about the causes and symptoms of cassava mosaic disease.
We also talk to a plant pathologist, who gives us essential tips on preventing and combating the disease.
You might choose to present this script as part of your regular farming program.
You could also use this script as research material, or as inspiration for creating your own programming on cassava disease problems or similar topics in your country.
Talk to farmers and experts who are growing cassava or are knowledgeable about the crop.
You might want to ask farmers:
- Are you familiar with cassava mosaic disease?
- Do you know how the disease is transmitted?
- Do you know how you can prevent the disease from affecting your cassava crop?
And the experts:
- Where can farmers get clean, disease-free cassava planting materials?
Estimated duration of the script, including intro and extro: 25 minutes.
Today we will be talking about cassava mosaic disease in Nigeria. We will be speaking to cassava farmers from across the country about their experiences with the disease and how they managed it.
In Nigeria, cassava is one of the most important food and cash crops. We produce close to a fifth of the world’s cassava each year—about 34 million tonnes. Cassava is a hardy crop that grows easily across the country, regardless of climate, and does not need a lot of care.
To give you an idea of how easy it is to grow, when we studied agricultural science in school, it was cassava that we first grew, the idea being that even us city kids couldn’t mess it up.
Cassava is truly a versatile crop, and can be used to produce industrial starch, ethanol, and cassava flour, amongst other products.
Cassava mosaic disease could have a cataclysmic effect on cassava production in Nigeria. That’s why preventing it is of the utmost importance.
But there is a lot of confusion about the disease. Most farmers don’t know how to prevent it, and are only aware of the symptoms after it’s too late.
To learn more about the disease, we spoke to Dr. Elechi Asawalam. She is an Associate Professor at the Department of Plant Health Management at the Michael Okpara University of Agriculture in Umudike.
Thank you for joining us, Doctor.
It is a very serious disease, in fact the most serious viral disease that affects cassava. Losses of yield range from 20%-90%, depending on the variety and the stage of crop growth at infection. In fact, we are only about 20 years removed from the worst ever cassava pandemic, which affected production across Nigeria, the DRC, Uganda, and other parts of East Africa.
There can also be reduction in the size of the leaflets. The large cassava leaves consist of seven leaflets. In severe cases you really don’t get any smooth leaves on an infected plant.
The adult whitefly attacks the undersides of the young leaves. Whiteflies are less active in the early mornings, and you can actually see them on the leaves then.
The whiteflies suck the sap from the leaves with their piercing and sucking mouthparts. When they suck the sap from the leaves, this does not really cause any physical damage to the plant. But, as the whitefly feeds, it injects the plant with the virus which causes cassava mosaic disease.
Dr. Asawalam will be back later in the program to tell us how to combat and prevent cassava mosaic disease. But first, let’s talk to a few farmers about their experiences with CMD.
We have with us Mr. Afolabi Akintonde, a cassava farmer from Lagos. Hello, Mr. Akintonde, welcome to the program.
I have been farming cassava for three years now, since 2013. Before cassava, I raised animals—cattle, sheep and goats, pigs, and poultry. You might say I am a complete farmer!
Cassava is the crop I grow, though; cassava and a bit of watermelon on the side.
My farm is in Oke-Ogan, which is in Ogun State. But I still live in Lagos, so I commute a lot to go and check it out.
Things are a lot better now; we’ve certainly come a long way.
I feel that this difficulty in managing the farm led to some of our plants being infected with the virus. We had areas that became overgrown with weeds and were hosts to rodents and other vectors.
When that didn’t work effectively, we decided to isolate the part of the farm that had the disease. We uprooted the infected plants and burnt them so the virus would not spread to other plants.
Burning the plants meant that whiteflies couldn’t continue to transmit the virus from an infected plant to a healthy plant.
We’ll be talking with one more farmer, and then we will welcome back Dr. Asawalam to talk about how to combat CMD.
We welcome Mr. Joogi Tor to the show.
It didn’t just happen once, it happened twice to me, and both times I was a bit helpless. All we could do is not use the stems again. We thought they were defective. Talking to you now is the first time I ever heard that insects might be the cause. So if it was to happen again, I would look at it differently.
Another method for curbing the spread of the virus is to use virus-free stem cuttings for all new plantings. Make sure that the stem cutting is virus-free.
Intercropping is also a very useful tool. As you know, cassava is a root and tuber. But you can plant another crop in between the cassava—a legume like cowpea or mung bean. This will actually decrease the whitefly population.
Try to time your plantings. Avoid planting when the whitefly is most abundant. The farmer needs to avoid exposing vulnerable young plants to the risk of infection when whiteflies are most abundant.
There are synthetic or chemical insecticides, but I would not really recommend them as they are hazardous to the environment. However, there are now biopesticides, or pesticides made from plants. Our local medicinal plant extracts like neem, scent leaf (Ocimum gratissimum), ginger, bitterleaf, and many more can be extracted and sprayed in the field as a natural insecticide for the whiteflies. They have been proved to kill whiteflies.
You can also plant hedgerows and strips of plants like mucuna, also called velvet bean, in between the cassava plants, which helps create barriers to whiteflies.
Well, there you have it. It seems like the easiest way to prevent cassava mosaic virus is to be vigilant and conscientious on the farm. Watch out for diseased plants. If you notice your leaves are curling or turning white or yellow, you should immediately take action, and cull or rogue the affected plants before they infect the rest of your crop. You can do this by burying or burning.
Also, keep the farm well-maintained, and combat any insect infestations and your cassava yields will not be too adversely affected. And lastly, always plant clean, disease-free stem cuttings.
That’s all for today. I hope you all learned a lot; I most certainly did.
Contributed by: Ted Phido, The Write Note Limited, Lagos, Nigeria
Reviewed by: Dr. Elechi Asawalam, Associate Professor, Department of Plant Health Management, Michael Okpara University of Agriculture, Umudike
Dr. Elechi Asawalam, Associate Professor, Department of Plant Health Management, Michael Okpara University of Agriculture Umudike, December 16, 2016
Afolabi Akintonde, Secretary, National Cassava Growers Association, Lagos Chapter, December 22, 2016
Margaret Adegbite, Lagos-based farmer, January 19, 2017
Eniin Emicy, owner and farmer, Ego Farms Resources, Rivers State, January 20, 2017
Ezekiel Sammy, Cross-River State based farmer, February 16, 2017
Joogi Tor, Benue State-based farmer, February 17, 2017
This script was created with the support of CABI Plantwise through Farm Radio Trust.