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Killing mealybugs with bananas April 21st, 2014 by

Most scientists work in disciplinary fields, a narrow focus that encourages researchers to promote what they believe in the most and discard alternatives. Thailand has made headway in controlling the cassava mealybug, a new pest that arrived in the country in 2008. While introducing a parasitic wasp surely contributed to controlling the cassava mealybug, it was only part of the solution, as we learned on a recent visit to make a farmer training video. Staff from the Department of Agricultural Extension embrace classical biological control, but seemed sceptical about farmers using botanical pesticides.

As often happens, farmer innovations are discarded because they have not been proven scientifically. But scientists may never have the interest, time and resources to validate all farmer innovations. And scientific validation is not always needed before one can promote a local innovation. Most of the other practical arts are not subject to scientific validation of all their innovations.

At the time of planting, Mr Sawart Jaimetta, an entrepreneurial farmer in northeast Thailand, told us that before he plants his cassava cuttings, he soaks them in a solution of water and an extract made from banana plants. It kills all the mealybugs hiding in the cassava buds and increases the vigour of the cuttings.

“There are beneficial microorganisms at the base of the banana stems. When we want to make a plant extract we have to dig the banana stems in the early morning. When the plant has not yet received sunlight, the hormones are still at the base of the stem,” Mr Sawart says, his choice of vocabulary suggesting how he has creatively blended outside knowledge with his own keen know-how.

Mr Sawart chops the corms and bottom halves of two young banana shoots into small pieces. He mixes 10 liters of molasses with 10 liters of water in a bucket to which he adds a small bag of effective micro-organisms (EM) to speed up the decomposition. He says the mix would also work without adding these beneficial bacteria, but it would take longer. Unless this seems far-fetched, think of making wine or bread without beneficial micro-organisms.

After stirring this solution, Mr Sawart pours it onto the banana cuttings in a plastic drum. The drum is tightly closed and placed in a shady place. Every week, he stirs the solution to speed up decomposition. A few months later, a white film covers the surface and the extract is ready for use.

As the extract is powerful, Mr Sawart mixes one liter of it with 200 liters of water before drenching the cassava cuttings for 10 minutes.

“If we use banana shoot extract to soak cassava cuttings, they will sprout twice as fast, in 5 days. We can also use the extract as foliar spray (applied to the crop’s leaves). It is like a hormone that makes the cassava grow well and strong to resist mealybugs,” says Mr Sawart Jaimetta.

Mr Sawart received training from various projects and added his own experience: “I have also made extracts from other plants, but the corms and base of banana stems give the best results.”

To kill the cassava mealybug he also reared Beauveria (a fungus that kills insects), parasitic wasps (that lay their eggs inside insect pests) and lacewings (their larvae eat mealybugs and other pests).

As this story shows, farmers are not restrained by scientific disciplines. Farmers need training and new ideas to test. They will apply whatever does the job, especially if it is low cost and of little risk to their health. Many scientists are yet to accept and learn from this pragmatic attitude. When we communicate with farmers, especially through mass media, we need to open up to solutions offered by different disciplines as well as to those developed by farmers.

To learn about a global programme that builds on and scales up farmer-led approaches to development, visit Prolinnova.

To see examples of farmer training videos, visit Access Agriculture.

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