Invasives Blog

Teacher and pawpaw farmer Wilfred Mutondi with his infested pawpaw fruits (Credit: CABI).

The potential and importance of papaya production in Kenya cannot be overemphasised. It is ranked fourth most important fruit crop in Kenya after oranges, mangoes and bananas, writes Fernadis Makale, Research Officer, Invasive Species Management based at CABI’s Africa Centre in Nairobi, Kenya.

While this important fruit contributes immensely to both nutrition and the economy, several production challenges have hampered the growth and development of the value chain in the country.

Among other constraints, the invasive papaya mealybug (Paracoccus marginatus) has been ranked high in the top pests affecting the papaya and other horticultural crops. Since its first report in 2016, the pest has spread to over 53% of papaya producing counties in a span of just four years.

Significant losses

Economic damage as a result of the feeding activity of papaya mealybug has been estimated by the Kenya Plant Health Inspectorate Service (KEPHIS), CABI and the Kenya Agricultural and Livestock Research Organization (KALRO) in selected counties on pawpaw production and has seen crop losses range from 53-100%. Other losses were incurred through increased production costs and the psychological effects upon farmers themselves.

While farmers trialled different management practices, they reported them to be ineffective against papaya mealybug. According to Wilfred Mutondi, a teacher and pawpaw farmer in Mombasa county, many of his neighbours are abandoning pawpaw cultivation for other crops.

Mr Mutondi said, “In the last two years, my garden has been shrinking. I opt to uproot the affected crop but I have been basically reducing my farm size as the transplanted seedlings get killed before maturity.”

Another farmer and nursery operator, Mr Mahindra poses: “Is it worth growing papaya anymore if I have to spend over 80% of my production budget on buying chemicals? What are the negative effects for the sprayer and consumer as a result of continued pesticides use?”

Walter Pole, an agricultural extension officer, Kwale, with a heavily infested papaya leaf (Credit: CABI).

Research conducted

Working with counties of Mombasa, Kilifi and Kwale, CABI conducted a Knowledge, Attitude and Practices (KAPs) study of papaya mealybug biological control in these areas. From the Focussed Group Discussions (FGDs) and Household surveys, the use of pesticides and local concoctions (including neem, chilli etc.) were the common management practices. Interestingly, many farmers did not know native biocontrol solutions including pest natural enemies.

In advocating for and willing to participate in communal biocontrol projects, many farmers were very keen to participate in cooperative efforts with neighbours – including the coordinated release of biological control agents such as the encyrtid wasp (Acerophagus papayae) towards the control of papaya mealybug. However, major concerns were raised which included the expansion of the biocontrol agent’s host range and the impact of abiotic factors including weather and biotic factors e.g. hyperparasites. Indeed, this reflects the fears of any biocontrol projects across the world and the concerns were valid.

Agent released

CABI and KALRO were granted a conditional release permit of the biocontrol agent and among the conditions were mass awareness and farmer and extension training before release of the parasitoid. Elaborate plans to engage different stakeholders in the selected counties have been put in place and already a stakeholder awareness meeting has been held in Mombasa, Kwale and Kilifi.

Acerophagus papayae female lateral view (Credit: ICAR-National Bureau of Agricultural Insect Resources).

This involved the top leadership of the county agricultural department, local authority, farmers, KEPHIS, National Museums of Kenya, The International Centre of Insect Physiology and Ecology (ICIPE), KALRO and CABI. The objective of this meeting was to create awareness of the introduced biological control agent, Acerophagus papayae, and share the findings of the quarantine performance to enable stakeholder buy-in in anticipation of the field release.

During the meeting, the background of the papaya mealybug biocontrol works and findings of the biological and socio-economic surveys and performance of biocontrol agent in quarantine were shared. A way forward regarding further engagement was also agreed between participants.

While biocontrol offers a sustainable solution to the management of papaya mealybug, less is known of the native and introduced natural enemies including the selected parasitoid.

Knowledge gaps

Indeed, even with willingness of farmers to embrace and support biological solutions in pest management, they confessed to knowledge gaps at both farmer and extension level. Borrowing from experiences in Pakistan and West Africa, we plan to emulate success of the roll out plans to include as many stakeholders as possible. Post-release monitoring and reporting to the Kenya Standing Technical Committee on Imports and Exports (KSTCIE) is scheduled for every quarter from release.

Biocontrol for most pests has been shown to succeed at community level and A. papayae is not an exception. But for it to do so, suggestions from farmers in the three counties included forming farmer committees to supervise area-wide operations especially in mass rearing, distribution/release and monitoring were important.

A papaya orchard (Credit: CABI).

Glory days

These committees are to be the advocacy group for the reduction of pesticide use and communication centre regarding plant health. Other suggestions included: Adoption of Farmer Field School (FFS) model where farmers learn about Integrated Pest Management and Good Agricultural Practices (GAPs). These FFS will be the training ground and also mass rearing points for the parasitoid. We believe through this we will be able to manage papaya mealybug and revitalise the papaya production in the country back to its glory days.

Additional information

Main image: Teacher and pawpaw farmer Wilfred Mutondi with his infested pawpaw fruits (Credit: CABI).

Relevant news stories

See also ‘CABI searches for biological control to halt surge of papaya mealybug menace in Kenya’ and ‘New research maps potential global spread of devastating papaya mealybug pest.’

Funding acknowledgement

We gratefully acknowledge the core financial support from our member countries (and lead agencies) including the United Kingdom (Foreign, Commonwealth and Development Office), China (Chinese Ministry of Agriculture and Rural Affairs), Australia (Australian Centre for International Agricultural Research), Canada (Agriculture and Agri-Food Canada), Netherlands (Directorate-General for International Cooperation, and Switzerland (Swiss Agency for Development and Cooperation). Other sources of funding include programme/project funding from development agencies, the fees paid by our member countries and profits from our publishing activities which enable CABI to support rural development and scientific research around the world.

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