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.

Papaya mealybug in itself has been estimated to have caused 57% 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.

Meanwhile Kigenge has added to the woes of smallholder farmers with crop yields also significantly reduced with seasons cut from an average of four to one and the general lifespan of orchards.

Root-rot was also found to be common, especially in the central district of Uganda.

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.


Leaves of the papaya plant show signs of the viral disease Kigenge (Credit: CABI).

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.

Fernadis Makale, Research Officer, Invasive Species Management, based at CABI’s regional centre for Africa in Nairobi, Kenya, said, “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.

“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.”

Mr Makale highlighted that without natural enemies to manage outbreaks, farmers often turn to pesticides. The lack of registered pesticides results in farmers using highly hazardous chemicals that are not only ineffective but can negatively impact native insect biodiversity such as pollinators and natural enemies of pests. A more ecologically sound approach to management is the use of biological control.


CABI is working in partnership with NARO and MAAIF to tackle papaya mealybug and the viral disease known as Kigenge on papaya crops in Uganda (Credit: CABI).

CABI has already been working on natural enemies to try and fight papaya mealybug in Kenya under the Darwin Initiative project which will also see similar work to that conducted in Uganda also take place in South Sudan.

It is hoped that 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.

A study on knowledge, attitudes and perceptions of farmers with regard to classical biological control of papaya mealybug revealed that 85% of farmers viewed the release positively, and most (94%) would support the biological control programme in their community.

The work in Kenya also involves collaboration with the Kenya Plant Health Inspectorate (KEPHIS) and the National Museums of Kenya (NMK). In South Sudan the partnership is with the University of Juba.


Additional information

Main image: 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).

Project page

Find out more about the ‘Protecting biodiversity through biocontrol of papaya mealybug in East Africa’ project from the Darwin Initiative website.

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