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Fighting pests and diseases of papaya in Uganda

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CABI is working in partnership with the National Agricultural Research Organisation (NARO) and the Ministry of Agriculture, Animal Industry and Fisheries (MAAIF) to step up the fight against pests and diseases of papaya in Uganda.

As part of the ‘Protecting Biodiversity through Biocontrol of Papaya Mealybug in East Africa’ project, which is funded by the Darwin Initiative, CABI has been testing for signs of papaya mealybug and the suspected viral disease locally known as Kigenge.

According to CABI, papaya mealybug in itself has been estimated to have caused 57 percent yield losses worth £2,224/ha each year between 2016 to 2020 in East Africa. The pest is native to Central America but has spread rapidly in invaded countries. It was detected in Uganda in 2021 where it has the potential to affect the production and quality of papaya and other host crops.

CABI scientists investigated farming practices and management options for pests and diseases of papaya in eight locations across Uganda. These included Lira, Kayunga, Mukono, Ntungamo, Luwero, Masaka and Mpigi. In total, 67 samples of disease plant were collected, processed and shipped to Fera Science in the UK for identification. The work was also carried out under the CABI-led PlantwisePlus programme which aims to help farmers be prepared for crop pests and take a more sustainable approach to managing them.

The research team determined that papaya is a major cash crop in Uganda, that Kigenge is widely spread in all the survey districts but with more infestation in Kayunga and Mukono, that commercial farmers are using more pesticides (especially in Kayunga) but that non-commercial farmers are doing nothing to manage the disease at all.

According to Fernadis Makale, research officer, Invasive Species Management, based at CABI’s regional centre for Africa in Nairobi, Kenya, the identification of disease will give an opportunity to start its management including vectors, if any. “Once this is confirmed, it is suggested that there is continuous engagement with the papaya farming community and mass awareness of Kigenge and its impact and management,” noted Makale. “There should also be consideration for the development of an integrated pest management package for the papaya value chain to include this disease and other pests of interest.”

CABI has already been working on natural enemies to try and fight papaya mealybug in Kenya under the Darwin Initiative project which will see similar work to that conducted in Uganda also take place in South Sudan. It is hoped the encyrtid wasp Acerophagus papayae could prove to be an effective biological control agent to mitigate papaya mealybug. Working with the Kenya Agricultural and Livestock Research Organization (KALRO), CABI performed releases of the wasp at three coastal counties of Mombasa, Kwale and Kilifi. They also took the opportunity to train farmers on a pilot farm about the use of classical biological control of papaya mealybug using the parasitoid and how they need to avoid insecticides when doing so.

Photo: CABI and colleagues from NARO and MAAIF inspect papaya crops on a farm in Uganda for signs of papaya mealybug and the viral disease known as Kigenge (Credit: CABI).

Read the NOV/DEC 2022 issue of New AG International, free to view here.

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