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Ravenous fruit flies no longer bother us

Saturday June 6 2015

A fruit fly trap hanging on a mango tree with dead insects. PHOTO | RACHEL KIBUI

A fruit fly trap hanging on a mango tree with dead insects. PHOTO | RACHEL KIBUI | NATION MEDIA GROUP

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A visit to the AIC Cheptembo Farm in Marakwet leaves one yearning for a piece of a mango, if not mango juice.

The green mangoes hanging on trees whet a visitor’s appetite. If only one would paint the fruits yellow and ripen them, then sit under one of the trees to enjoy their juicy taste…

In the hope of finding at least one ripe mango, I go searching but I only find a clear plastic container dangling on one of the branches. Its brownish contents can easily be mistaken for sand.

Why would someone hang a half-full container of sand on a tree?

“Well, the content is not sand, they are dead male fruit flies which were trapped and have died in there,” explains Walter Rono, the farm manager

So how did the fruit flies end up in the container?


The farm’s journey to adopting this relatively new technology was triggered by the hefty losses that were caused by fruit flies.

Initially, Rono explains, workers struggled to spray the mango trees against fruit flies. This was not only expensive, but unrealistic. The stubborn pests would fly away anyway, only to return when the sprayed chemicals are no longer effective.

“It would cost at least Sh2,000 to spray a single mango tree, yet there was minimal, if any, achievement in curbing the white flies,” explains Rono.

The farm has a total of 150 mango trees on three acres of land. But only 60 trees are mature enough and are bearing fruits.

Fruit flies mostly affect mangoes, pawpaws, avocados, water melons and other fruit trees.

The flies are a quarantine pest under the European Union market, meaning produce that is infected or suspected to be infected cannot be exported to this market that buys 90 percent of Kenya’s horticultural export.

Until mid-last year when this farm introduced the bactrolure, Rono says, they used to dispose of up to 60 percent of their annual harvest due to destruction by the white flies.

But this year has been different as they only lost about seven percent of the harvest to the pest.

Each tree gives between 300 to 600 fruits annually, which sells at between Sh10 to Sh15 each on the local market.

The main varieties grown here include Kent, Tommy At, Apple, Van Dike and Dodo mangoes.

While other varieties have one annual season, Apple mangoes have two seasons each year.

“I learnt about the bacrolure trap when I attended a farmers’ training seminar organised by the Kenya Plant Health Inspectorate Service (KEPHIS) in Eldoret last year,” says Rono

Knowing how desperate his employer was to eradicate fruit flies, Rono was quick to try the new technology, and his decision has not been in vain.

For Sh350 per bacrolure set, the trap comes as a set of a bucket trap which is perforated on its lid, a thin wire hook and a sachet with lure.

Rono says that soon, the farm will venture into mango export business as their produce will finally be cleared especially for the coveted European market.


Samuel Kagumba, the technical director at Farmtrack Consulting, says the trap is laced with a chemical which has a pheromone, a scent that disrupts, attracts and kills male flies.

Farmtrack has beaten the odds to become the first company to adopt this trap that brings hope to fruit farmers.

Kagumba says the mimicked pheromone attracts males, which are lured into the trap thinking they are heading to females for mating.

“Unknown to them, the scented trap is laced with some chemical that kills males,” says Kagumba, adding, “The more males that die, the lower the chances of fertilisation, meaning that finally, the pests are eradicated,”

One female, Kagumba says, lays 300 eggs in her lifetime, but the unfertilised eggs do not cause any destruction to fruits.

Kenya exports mangoes to Saudi Arabia, according to Kagumba, but attempts to sell to EU countries have been futile due to interception occasioned by fruit flies infection.

“The Middle East has no much problems with the pest as the flies cannot survive there anyway,” says Kagumba.

Though one trap can attract insects from as far as a kilometre away, it is advisable to use each (trap) for a quarter acre piece of land.

The lure can last up to three months before being changed. It can catch up to 1,500 male fruit flies, according to Kagumba.

In the recent past, the EU has been partnering with United Nations Industrial Development Organization (UNIDO) to educate farmers and exporters on pests that are a threat to the export market.

Among the top five pests that are a threat to this market are fruit flies, false codling moth, cotton leaf worm and white flies.

Spraying against white flies, Kagumba says, is unrealistic as the insects are likely to fly away while spraying goes on while mango trees are too large to be sprayed.

Other regions that have adopted this technology, according to Kagumba, include Embu, Meru and parts of Coast.