Invasives Blog

Smallholder farmers in South Sudan are embracing nature’s solution to the papaya mealybug menace which has been devastating crops since it first invaded East Africa between 2015 to 2020.

The papaya mealybug (Paracoccus marginatus) causes up to 91% yield losses – worth around £2,224/ha to households – thereby severely impacting the livelihoods of smallholder farmers as well as local and national food security and opportunities for export.

But CABI is working in partnership with the National Museums of Kenya and the University of Juba, South Sudan, to fight back with the release of the biological control agent Acerophagus papayae as part of anIntegrated Pest Management (IPM) plan.

Focus turned on infested fields at selected learning farms

As part of the project Protecting biodiversity through biocontrol of papaya mealybug in East Africa,’ funded by the Darwin Initiative, CABI has turned its focus on infested fields at selected learning farms in the Central Equatoria region of South Sudan.

A team led by CABI’s Fernadis Makale, Scientist, Invasive Species Management, and Professor Peter Gama from the University of Juba, conducted field releases of the parasitoid Acerophagus papayae in Central Equatoria.

These tiny natural enemies, imported from CABI’s biocontrol labs on mummy cards, were strategically placed on infested papaya leaves to target the mealybug population.

This biocontrol approach offers a sustainable and environmentally friendly alternative to harmful pesticides, aiming to protect livelihoods and food security in the region.

Mr Mundia, a papaya farmer in Nesitu, inspects his crop with the mummy cards (Credit: CABI).

Mr Mundia, a papaya farmer in Nesitu with a 12-acre farm, expressed his gratitude for the introduction of the papaya mealybug parasitoid. He shared that the mealybug infestation had been a persistent and costly challenge, despite heavy pesticide use.

Need for an alternative solution

The ongoing spread of the pest, despite these efforts, underscored the need for an alternative solution.

Mr Mundia believes that the parasitoid release offers a promising avenue for reducing reliance on harmful pesticides, which not only incur high costs but also pose potential risks to the plant’s health, the environment, and his own well-being.

Mr Mundia said, “Since I first observed the mealybug, I have spent a lot of money on pesticides to control them, but as you can see, I have not been successful as the mealybug continues to spread.

With the release of these parasitoids, I will save money that would have gone to buying pesticides. Since I grow papaya for seed, I believe excessive use of pesticides is not only expensive but also impacts plant physiology, the environment, and my health. So, this is a welcome saviour.”

Surveys to understand the broader impact of the mealybug

Beyond papaya, the team also conducted extensive surveys to understand the broader impact of the mealybug. Farms in Rajaf West, Rajaf East, Nesitu, and Nyaing were surveyed for signs of infestation on crops like citrus, okra, cassava, and hibiscus. While the mealybug was detected on all farms, the infestation levels were relatively low, possibly attributed to the recent rains.

Mr Makale said, “This initial phase of the mission is a crucial step towards controlling the papaya mealybug and protecting South Sudan’s agricultural sector. Continuous monitoring and future releases are planned to safeguard crops and ensure the long-term success of this biocontrol initiative.

“By harnessing the power of nature, we aim to empower farmers and safeguard their livelihoods. The fight against the papaya mealybug is far from over, but with dedicated efforts and innovative solutions, we are optimistic about creating a sustainable future for South Sudan’s papaya and horticulture industry at large.”

Back in July, CABI working with key Kenyan partners, also stepped up the fight against the papaya mealybug in five more major papaya growing counties in Kenya.

This means CABI scientists and colleagues from the Kenya Agricultural and Livestock Research Organisation (KALRO), the Kenya Plant Health Inspectorate Service (KEPHIS) and the National Museums of Kenya (NMK) are fighting the pest in a total of eight counties across the country.

CABI is also partnering with the National Agricultural Research Organisation (NARO) to tackle the papaya mealybug in Uganda, intensifying efforts to fight this pest in East Africa.

The work is funded through the Darwin Initiative project as well as the CABI-led PlantwisePlus programme.

Additional information

Main image: CABI is working in partnership with the National Museums of Kenya and the University of Juba, South Sudan, to fight back with the release of the biological control agent Acerophagus papayae as part of an Integrated Pest Management (IPM) plan (Credit: CABI).

Project page

Find out more from the project page ‘Biocontrol of papaya mealybug in East Africa.’

Relevant stories

‘Conserving insect biodiversity.’

‘CABI and partners step up fight against devastating papaya mealybug on more farms in Kenya.’

‘Study shows “strong evidence of exceptional efficiency” of biological control agent against papaya mealybug pest.’

‘New research maps potential global spread of devastating papaya mealybug pest.’

‘Natural Enemies Field Reservoirs play critical role in management of papaya mealybug, CABI study reveals.’

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Scaling up the fight against papaya mealybug pest in South Sudan

The papaya mealybug (Paracoccus marginatus) is a significant pest of papaya which has been wreaking havoc amongst smallholder farmers since it first invaded East Africa between 2015 to 2020. At worst, the papaya mealybug causes up to 91% yield losses –…

1 December 2023