Kenya: Mango farmers use plastic bottles to manage fruit flies

November 11, 2019
A translation for this article is available in French

Josiah Mwangi’s farm is full of mango trees. Looking at it from a distance, the trees appear to form a canopy, with scattered patches of green stretching to the horizon. On the farm, the 52-year-old father of five walks with heavy, crunching steps over dry, fallen mango leaves.

With his left hand, Mr. Mwangi holds a one-litre plastic bottle with holes punched in the sides so that flies can enter, attracted by bait inside the bottle. He will hang the bottle on one of his mango trees to trap fruit flies, a pest that attacks mango fruits and is responsible for up to 60% of post-harvest losses. He says, “Fruit flies are small, but they cause huge damage.”

Mr. Mwangi comes from Kambiti village in central Kenya’s Muranga county. In Kambiti, mangoes begin to ripen in November. Like many farmers in his village, Mr. Mwangi is busy placing traps to protect his mango orchards from fruit flies.

Fruit flies damage ripening mangoes when the adult fly lays eggs inside the fruit. The eggs hatch within 2-4 days and the larvae feed on the flesh, causing the fruit to rot.

Mr. Mwangi used to grow maize as a cash crop but switched to mango farming because of the erratic rains in his area. But 2013 was painful: he lost almost 80% of his two acres of ripening mangoes to fruit flies.

He says, “Mango farming is one of the reliable cash crops, but still we are hit with pest infestation which can destroy the entire harvest in a season.”

Following a training on pest management conducted by Farmtrack Consulting Limited, Mr. Mwangi and other farmers learned how to use a jar-like container with holes punched in the sides as a trap for fruit flies.

Mr. Mwangi says: “I could not believe this would work, but I can attest to it now. Through fruit fly traps, I can assure you that I have seen a great reduction in losses of mango fruits every season.”

Farmtrack trained the farmers to use pheromones. Pheromones act similarly to hormones, and the traps use them as a bait to lure male fruit flies into the container to mate with females. The male fruit flies are trapped inside and die because the trap also contains an insecticide. So the traps help to reduce pest populations by interfering with reproduction.

Farmers can buy commercially-produced bait in shops for 300 Kenyan shillings (about $3 US) and a container for 100 Kenyan shillings (about $1 US). To reduce the cost, farmers are using free and readily available plastic bottles. The farmers punch holes in the bottles instead of buying fly trap containers.

Samson Ndauti is a mango farmer who also lives in Kambiti village and was trained by Farmtrack. He says: “Farmers have quickly adopted the idea and are now making these trappers on their own. The trappers are hung on mango trees, with the bait serving for the three-month harvesting season of mango fruits.”

Here, mangoes are grown in a single season that runs from November to February or March. Mr. Ndauti says that farmers should place fruit fly traps in early to late November.

He explains: “This ensures that the farmer does not spend more towards purchasing the bait. One buys bait once per season. However, those who grow late-maturing mango varieties should use bait for more than three months.”

Mary Wangui is another local mango farmer. The 41-year-old mother of four says that, since she started using the simple innovation of plastic bottles to manage fruit flies, she has had huge success in reducing post-harvest losses .

She says: “I once lost almost the entire harvest season to fruit fly infestation on my one-acre farm. However, fruit fly traps, especially when we use locally available materials such as plastic, have helped us in the fight.”

This resource is supported by The Rockefeller Foundation through its YieldWise initiative.

Photo: Stella Wangechi explains how the traps work to FRI’s Moses Provabs.