Banana Mnyauko

Pronouced mm-nya-ou-ko, this crippling banana disease is number one on famers’ list of problems here in the Kagera Region of Tanzania. Its English name is Banana Xanthomonus Wilt (BXW). Don’t ask me how that’s pronounced.

In 2001, this bacterial banana disease was detected in Uganda.  Despite quick action to control the disease at every level – commercial production down to the subsistence farmer – within five years it had spread to Rwanda, DRC and Tanzania.

Why is it such a big deal? First of all, cooking banana is the main food source, usually boiled with beans and lots of salt in a dish called matoke (ma-toh-kay).  Most of the population eat it at least once a day and it’s often the only thing eaten, all day.  Every family has a little farm (shamba) in their backyard, which is principally a small banana plantation with other crops grown in the understory. Bananas are perennial, so it works well as a holistic system, with corn, pumpkin, coffee, fruit trees and beans all under the shade of the bananas. Since banana is the staple food, and everyone has them growing year-round, people generally can feed their families from the small shambas. Generally. Until banana disease comes into play.

Beautifully diverse shamba, or small backyard farm, complete with banana, corn, beans and goats!

Cultivated bananas are naturally susceptible to disease outbreak since they propagate through clones, small offshoots of the main stem, called suckers. Once the main stem produces a fruit, it dies and a sucker grows up to replace it, producing its own fruit in 7 months or so. When you want to plant a new banana tree (not actually a tree but a pseudostem!), you simply take a sucker and plant it somewhere new; thus bananas of a certain variety are all genetically very similar, with similar susceptibility to invading pests. So disease spreads fast.

It’s only a matter of time until an intensively cultivated banana population becomes challenged with serious disease pressure. The bananas we eat in North America – bright yellow, having been artificially ripened in rooms flooded with ethylene – are of the Cavendish variety.  Cavendish replaced the previous popular variety, Gros Michel, when it was all but wiped out by the fungal Panama disease in the 50’s.  Wikipedia informs me that Cavendish has 10-20 years before it goes the same way as Gros Michel (from a different disease, of course).

The staple food here in Kagera is going the same way as Gros Michel unless a solution is found, which will probably involve genetic modification for a resistant variety.  Think potato famine.  Right now, extension officers preach cutting down infected stems and burying them, sterilization of tools used in the shamba, cutting off the male flower to discourage spread by pollinators (insects and birds), and ensuring that new stock is disease-free.  Lack of adherence to these measures, and the highly infectious nature of the bacteria, mean that not much control has been achieved.

Farmers say that about 1 in 5 new banana plants produce viable fruit.  Not only is it the staple food but many people make their living from bananas as well, so lack of food and lack of income with which to replace that food has meant a severe decrease in standard of living since 2006.  People complain they are no longer able to buy soap and pay their children’s school fees.

Banana plants infected with mnyauko

I heard some of these stories the other day, when I went with some of my youth volunteers (two from the UK and two Tanzanians) and the Ward Agricultural Officer (a woman!) to meet with a banana producer’s group.  I sat back to take notes, letting the volunteers direct the meeting, as they were collecting information about the group’s knowledge of mnyauko.

I wavered between annoyance and tears upon hearing the outpouring of desolate stories; the latter because I know they’re true, the former because people try hard to make their words resonate when they see three white faces sitting there.  From experience I know how to highlight that I am only offering the exchange of knowledge, before I even walk in.  It’s best to keep expectations low even if you do have hopes of finding funds, otherwise you end up with a room full of people yelling at you; what are you going to do about it?!  “It”, mnyauko, has researchers across the region stumped.  No, we are not offering loans, chemical pesticides (none are effective), or money.  The worst part is that in cases where a crop variety must be replaced by something more pest-resistant, farmers tend to be resistant as well… to the switch.

The meeting was informative for the volunteers and for me.  We managed to mitigate expectations after a few tense moments.  People are sick of hearing about control measures in the face of their potato famine.  They’re sick of talking, of knowledge exchange, of pamphlets.  Solutions are in demand, but nobody has any.

Daily banana market on my street in Kamachumu – people mostly bring their bananas by bicycle

A few [poorly cited] sources.

East African Highland Banana:

Bouwmeester et al. 2010. The Potential Benefits of GIS Techniques in Disease and Pest Control: an Example Based on a Regional Project in Central Africa:

Viljoen 2010. Protecting the African Banana (Musa spp.): Prospects and Challenges:

Biruma et al. 2007. Banana Xanthomonas wilt: a review of the disease, management strategies and future research directions:

Adriko et al. 2011. Banana Xanthomonas wilt sampling procedures: A technical publication:

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