Farmers buffeted by the voracious bean fly pest which has defied conventional pesticides, are now finding solace in cheap home made solution like papaya soap water, and are reporting saving upto 30 percent of their yield through this venture. Bean flies, also called bean stem maggots, are serious pests in Africa where in 2006 they entirely swept out some large bean farms, costing the Nigerian and Ghanaian economies $100 million in lost crops.
The adult is a tiny fly, about 2mm long, of a shiny black-bluish colour. The female fly pierces the young leaves to lay eggs and sucks the exuding sap. This creates yellow blotches on the leaves, which are the first signs of bean fly attack and can serve as an early warning of the infestation. The young maggots then mine their way from the leaves down to the base of the stem.
The maggot feeding destroys the tissue causing the stem to swell and split, with the flies often visible in the stem splits. Attacked plants tend to produce extra roots in compensation. But young seedlings and plants under stress wilt and die when attacked by bean flies. The damage is more severe in plants growing under poor conditions, with infertile soils or during drought.
But with the help of ethnoveterinarians - veterinarians who rely on traditional knowledge in pest control – farmers are now using common plants like Sodom Apple, pawpaw and African Marigold to spray their bean cultivated land with home-made solutions that act as repellants to the bean fly.
Conventional pesticides like Uquash 22100 from Russia, which farmers have used for many years, were only partially effective in controlling the fly, but also had long term adverse effects on the soil, with farmers needing to spend more on fertilizer after spraying the land with the pesticides. “It took us some time to detect why there was a drop in yields. Though we had managed to bring down the number of pests in the farm by a considerable number, yields in subsequent harvests were pathetically low. It took officials from the Ministry of Agriculture to identify that the problem was with the pesticides we were using,” said Conrad Ndegwa from Nyahururu.
Now, the organic pest control methods that began in Nyahururu borders are now being taken up in neighbouring districts, not only warding off the flies but assisting in fertilizing the soil. Farmers using Sodom Apple mix a kilo of its fruits and leaves with 3 litres of water, and crush the fruits together with the leaves before adding a little soap.
They soak the solution for a day after which they spray the solution either early in the morning or late in the afternoon. “The secret with spraying during these times is because pests are concentrated in one area during early morning as they plan where to go feed on during the day or late afternoon when they converge in one place in the afternoon. So far the method is working wonders,” said Mrs Nduguta Njeru, an ethnoveterinarian working with the Nyahururu farmers.
With papaya, farmers add a kilo of finely shredded papaya leaves to 1 litre of water and shake vigorously. This is then added to around 4 litres of soapy water. “If you have quarter acre of land, you get about half a kilo of leaves mixing them with half a kilo of water,” said Mrs Njeru.
However, the new methods have been met with dismay by local agrovets as the Nyahururu farmers have stopped buying the pesticides. The word of mouth reporting on the stellar performance of the home made solutions has become so widespread that some 5 agrovet dealers have closed shop in the last six months.
Farmer Smile agrovet is one of the shops that closed down two months ago after being in operation for five years.
“Our joy is not to drive them out of business, but to work for the greater good of the farmers. If farmers can save their land from pests, increase yields and save money to use elsewhere, that's all that matters. We have made several enemies in this pursuit, but we are guided by the principle of empowering farmers,” said Gachoka Tande, another ethnoveterinarian.