Josephine Maseruka
17 July 2007
Kampala — A tropical weaver ant, commonly found in Africa, Asia and Australia, could save Africa up to 60% of its high value crops such as fruits and nuts that are consistently ravaged by fruit flies.
Dr. Paul Van Mele, the technology transfer specialist at the Africa Rice Centre in Benin, said fruit flies damage about 40% of Africa's two million metric tonnes of mangoes produced annually.
Mangoes are one of Africa's most important sources of Vitamin C.
He said fruit flies and the fact that most small-scale farmers cannot afford pesticides led to the United States to ban mango exports from West Africa.
If the weaver is taken on in Uganda, it will increase the country's mango exports, reduce on the use of expensive and inaccessible pesticides, thus raising revenue.
Africa's small-holders fruit producers evade fruit fly infestation by harvesting fruit before it matures, but still incur significant losses from fruit fly damage, according to the published research.
Van Mele has described the weaver ant known as Oecophylla longinoda as 'a gift of nature'. He is optimistic that the tropical ants will rescue Africa's high-value crops since they provide organic solutions to fruit farmers in Africa while challenging conventional biological control of insect pests.
This month, Van Mele and others published a paper entitled the "Effects of an African Weaver Ant, Oecophylla longinoda, in Controlling Mango Fruit Flies (Diptera: Tephritidae) in Benin".
The paper observes that while the weaver ants exist in abundance in Africa, their use is still at the experimental stage in many countries. Scientists say the ants have been proven effective for fruit fly control and they can be used for controlling pests in most perennial crops except coffee.
He added that the use of the weaver ant to control fruit infestations is expected to challenge and radically redefine classical methods of biological control of pests.
Van Mele said: "The role of predatory ants in sustaining agricultural systems is an under-explored research area yet small-scale farmers in countries like Vietnam, India and Cuba have generated considerable knowledge on natural pest control that may be applicable to the African context."
Classical pest bio-control has traditionally focused on the use of parasitic insects-parasitoids-which reside in very specific crop pests attacking only particular life stages of their hosts.
The use of weaver ants as natural enemies has been traced back to the third century in south China, where subsistence farmers nurtured and used the ants to protect citrus fruits from insect damage. The practice spread to several Asian countries and Australia.
In Ghana the ants are being used together with neem tree extracts to produce organic cocoa. Tanzania uses them to improve their coconut harvests, while various African countries use them to safeguard cashew nuts and mangos.
Weaver ants are better than various parasitoids currently in place, which attack specific species of fruits fly, necessitating development of numerous species-specific parasitoids, each of which takes 10 years or more to develop. The readily-available weaver ant is indiscriminate in its predation on fruit flies and is active throughout the year.
Findings have shown that with the greater efficacy in countering fruit fly infestation as recorded by studies in some African countries, weaver ants can completely eliminate the need for pesticides- which are expensive and inaccessible to most African farmers.
This will make organic fruit farming in Africa more profitable by enabling farmers to access European markets.
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