EMILY Chakanyuka has been growing mangoes for more than 30 years. She has sold fresh mangoes to earn enough money to look after her family, but all that changed 20 years ago after an invasive and destructive citrus bug found her mangoes irresistible.
Says Chakanyuka: “In the 1980s we used to wholesale fresh mangoes to middlemen, the fruit was good and the money too, but later after 2000 the insect came and we saw our mangoes rotting. We were throwing them away,” explains Chakanyuka (58) from Ward 2 in Murewa district, 100 kilometres northeast of Zimbabwe’s capital, Harare.
“We were even scared to eat mangoes.”
The cause of Chakanyuka’s mango loss is the oriental fruit fly, known scientifically as Bactrocera dorsalis. It is an invasive fly originating from Asia which has found its way to Africa, thanks to rising temperatures creating ideal conditions for it to thrive.
The oriental fruit fly, Bactrocera dorsalis (Hendel), is a very destructive pest of fruit in areas where it occurs. It is native to large parts of tropical Asia, but has become established over much of sub-Saharan Africa, and is often intercepted in the United States, sometimes triggering eradication programmes.
The oriental fruit fly is totally different from the mango fly (cordylobia anthropophaga), which is a species of blow fly that is native to certain parts of Africa. The larvae of mango flies are parasitic, meaning they get under the skin of mammals, including humans, and live there until they are ready to hatch into maggots.
This parasitic infestation in a person is called cutaneous myiasis. The fruit fly which invades and devastates mangoes has brought misery to other mango growers like Chakanyuka who for a long time never paid attention to why their fruits were just rotting.
It took time for them to figure out the problem, while they ran loses and sustained viability problems in their citrus-growing businesses.
And the farmers’ worries have not been without justification; the fruit fly, unless controlled, can result in 100% fruit losses where it attacks. Its infestations have dwindled mango harvests and the income of smallholders across southern Africa.
Chakanyuka is one of 1 200 smallholder farmers in the mango-growing belt of Mutoko who were introduced to Integrated Pest Management (IPM) practices four years ago.
IPM involves the use of various pest management practices which are friendly to humans, animals and the environment.
The International Centre of Insect Physiology and Ecology (ICIPE), based in Nairobi, Kenya, together with various donor agencies and partners, developed an IPM package to manage the invasive fruit fly, which has been promoted under the Alien Invasive Fruit Fly project, a multi-stakeholder initiative under The Cultivate Africa’s Future Fund (CultiAF) by the International Development Research Centre (IDRC) and the Australian Centre for International Agricultural Research (ACIAR). ICIPE, working with national and international partners, developed bio-based holistic solutions to address the fly problem in East and southern Africa.
Farmers have been introduced to the male-annihilation technique, which involves mass trapping the male fruit flies using attractants such as Methyl eugenol, Curelure and Trimedlure, combined with insecticide.
The tool reduces male populations and therefore significantly reduces mating among the flies. In addition, other solutions have included farmers using “bait stations” — small plastic containers that hold food bait for fruit flies. Inside the bait is an insecticide that kills the flies.
The stations can be hung on mango trees or placed around the orchard. Alternatively, the bait can be mixed with toxicant and sprayed on tree trunks away from the fruits to avoid any residues on the fruits.
Another integrated pest management technology that has helped farmers fight the fruit flies is a tent-like structure called an augmentorium, which is fashioned out of plastic or netting and used by farmers to store fallen, infested fruits.
The augmentorium traps fruit flies because they are too large to pass through the netting holes, but it allows parasitoids (small insects and natural enemies of the fruit fly) to escape.
The parasitoids lay their eggs on the eggs or maggots of fruit flies and, as the eggs mature and emerge as adult insects, the process kills the fruit flies.
Biocontrol of pests works, scientists say. It is a shift from randomly spraying large quantities of toxic chemicals by farmers which has proved less effective as the fly proliferated. Worse, the use of insecticides is a risk to human health and for fruit quality.
As a result, residual levels of chemicals on fruit have become an issue for fruit importers like the European Union, which has tightened phytosanitary regulations for all mango exporters.
Chakanyuka says after joining the project, she earned US$80 during the second year of production from selling fresh quality mangoes. In 2022, she realised US$150 from selling a 20-litre bucket of dried mangoes. Before she started implementing IPM, she used to get under US$60 for a 20-litre bucket of fresh mangoes.
Another farmer, Chinkata Goodson, at the bait station in Likuni, Malawi, says planters have suffered losses of rotting mangoes for a long time without knowing the cause.
“I had been losing almost 50% of my mango harvest because looking at the way the fruits were bearing and what was on the market was really quite hectic,” says Goodson.
Donica Mugala, a lead mango farmer, in Chilanga district in northern Zambia, says farmers had resorted to spraying any chemical in a bid to save their mango crop from the destructive fly which they had no previous knowledge of.
“When farmers have no knowledge about how to deal with pests they resort to any means, and they fall prey to wrong chemicals as they want their fruits to be healthy. We used to buy anything we could get until we started using the IPM traps, which has really helped us,” Mugala said.
Agricultural entomologist and biocontrol expert Dr Samira Mohamed notes that the project is driven by the demand for solutions from mango growers hit by the fruit fly infestation. An entomologist is a person who studies insects.
Entomology is a branch of zoology.
“If they [farmers] spray the produce, it is rejected because it exceeds the maximum residue level of the export market, and if they do not spray, the mango is destroyed through the infestation of fruit flies,” she says.
Shepard Ndlela, an entomologist with ICIPE and project manager of the Invasive Fruit Fly project, says they sought to increase productivity of fruit growers while reducing post-harvest losses by linking agriculture, nutrition and human health.
Ndlela said the introduction of several technologies such as the parasitoids, pheromones, protein baits, augumentorium and biopesticides have helped farmers in Malawi, Mozambique, Zambia and Zimbabwe to fight the invasive fruit fly.
“When we bring science to the farmers, there is need to ensure adoption of the technologies and it is important that we involve the farmers in implementing the solutions that we have introduced and this project has successfully demonstrated that,” Ndlela says.
In Zimbabwe, approximately half of the 400 000 metric tonnes of mangoes produced annually are lost as a result of the destructive fruit fly.
Regionally, the accumulated losses caused by the fruit fly are estimated at more than US$2 million annually, according to the Food and Agriculture Organisation of the United Nations (FAO), which has categorised the oriental fruit fly as one of top four most destructive agriculture bugs worldwide.
Zimbabwe’s deputy minister of Lands, Agriculture, Fisheries, Water and Rural Resettlement Vangelis Haritatos says the government is working to protect farmers from the destructive fruit fly in line with Zimbabwe’s Horticulture Recovery Plan.
“We are worried about the post-harvest losses in horticulture . . . the farmer bears all the liabilities, the risks and then at the end this pest comes in and takes away all the profits,” Haritatos says, underscoring that the government would support recommendations on boosting farmer productivity in fruit growing.
A win for women
The Fruit Fly project has also empowered women who constitute a larger proportion of actors along the mango value chain in southern Africa.
The project, funded by the Canadian International Development Research Centre (IDRC), and the Australian Centre for International Agricultural Research, has trained 1 1684 farmers in southern Africa on IPM techniques, more than half of whom are women.
Christina Buchan, Canada’s ambassador to Zimbabwe, says IDRC has a priority on gender and believes that empowering women and girls is the most effective way to reduce poverty.
Noting that mangoes are important for livelihoods, especially of women and the youth, Buchan says the devastating effects of the fruit fly have forced many mango growers to contemplate moving away from the citrus venture.
“This project demonstrates that there are sustainable solutions that are effective, ecologically friendly and scalable,” she says.
In Zimbabwe, the project found that knowledge about fruit flies and IPM has increased equally among women and men, but the practices are more often used by women.
A direct impact of the project has been that women are also now coming together to form group saving accounts, enabling them to raise their own money — separate from their husbands’ income.
“In the past, most women were housewives and were expected to wait for the husbands to look after the family, but now women have become the breadwinners,” says Menale Kassie, in a presentation on the project.
Pelegrinah Musingwini, a mango farmer from Mhondiwa village in Murewa, extols the fruit fly project for boosting her mango production and income.
Musingwini (47) is one of the early adopters of the IPM techniques and has become a lead farmer in her village — using the traps and baits to enhance her mango harvest.
“When this project started, I benefitted from the knowledge I received and realised mangoes can be sold dried through value addition,” says Musingwini, a mother of 10 children, saying in the 2022/2023 farming season she earned US$200 from dried mangoes.
Musingwini also credits the project for enabling her to form money-saving clubs with other women in the community from the proceeds of mango sales. She has since bought two fourplate gas stoves with which she bakes cakes and muffins for sale.
Principal research officer in plant quarantine services under the ministry of Agriculture Louisa Makombe says the project has left a huge footprint in the three districts that served as project sites where the use of IPM strategies have helped reduce the fruit fly problem in mango production.
“However, the IPM strategies had overflowing impact in that they also improved quality of other fruits and fruiting vegetables that are hosts to fruit flies were protected from fruit flies through the same initiatives,” says Makombe.
“The project targeted to improve the quality of fresh mangoes, but however the excess fruit realised made farmers harness on value addition by solar drying mangoes for consumption off-season and also potentially for export.”
Entrepreneur and farmer Kuziva Chatukuta of Chatukuta Dried Foods in Murewa says there is unmet total demand for dried mango of over 350 tonnes in Zimbabwe and southern Africa region.
Chatukuta has been part of the project, helping train farmers in value addition and this has also benefitted him in expanding his business of drying mangoes as well as manufacturing solar driers.
“Our market in the past was the local Zimbabwean market, now we are into the Southern Africa Development region and in future we are targeting the USA, Europe, and UAE markets with our dried fruits and vegetables,” Chatukuta says, noting that his company has been training farmers on mango drying and buys the dried mango from them.