CABI News

Papaya mealybug can devastate a whole crop unless it is controlled

CABI scientists are working with partners in Kenya to find a natural enemy to fight the invasive papaya mealybug pest (Paracoccus marginatus) which can devastate whole crops if left unmanaged.

Fernadis Makale, an Invasive Species Management Assistant based at CABI’s Kenya centre in Nairobi, is part of a team of CABI researchers collaborating with institutions, including the Kenya Agricultural and Livestock Research Organisation (KALRO) and Kenya Plant Health Inspectorate Services (KEPHIS).

The scientists, working under CABI’s Action on Invasives programme – funded by the UK Department for International Development (DFID) and the Netherlands Directorate-General for International Development (DGIS) – have so far conducted socio-economic and biological surveys to discover the spread and impact of the pest.

Papaya mealybug is a serious pest of the papaya fruit which originated from Central America before spreading to the Caribbean and South America in the 1990s. The pest was first detected in Africa in 2010 in Ghana and in Mombasa County, Kenya, in 2016.

The researchers have found that more than half of Kenya has been invaded by papaya mealybug and its impact has led some papaya farmers abandoning farming the fruit altogether. They are currently considering whether or not the parasitoid Acerophagus papaya from West Africa could be introduced as an effective biological control.

Papaya mealybug infestation

Mr Makale said, “Our findings to date show that a significant part of Kenya is now invaded by papaya mealybug and that this has led to crops of economic importance being severely damaged. In some cases, farmers have given up farming the fruit due to the devastation the pest has caused.

“We have collected samples and have been monitoring them for any emergence of parasitoids that could be used to fight the pest. Two Anagyrus spp. parasitoids have so far emerged and their true identity is being confirmed both morphologically and with molecular analysis.

“Different papaya mealybug samples have also been collected from different counties and we are currently running molecular analysis to determine if there is any variation in strains which may make the biological control of the pest more complex.”

In 2017, SciDev.Net reported how pawpaw farmers in Pakistan averted a near-complete devastation of the country’s papaya crops, which were affected by the mealybug pest, after replacing ineffective conventional chemical pesticides with natural predators that proved to be successful.

The intervention was made possible through CABI’s papaya pest management program which involved researchers setting up Natural Enemies Field Reservoirs on farmers’ fields to breed the Acerophagus papaya parasitoid as well as eight other natural predators of the papaya mealybug.

Together with partners in Kenya under the UK Government’s Darwin Initiative – National Museums of Kenya (NMK), Natural History Museums, London, University of Nairobi (UoN), Kenya Plant Health Inspectorate Services (KEPHIS), Kenya Agricultural and Livestock Research Organisation (KALRO), and Kenya Forestry Research Institute (KEFRI) – CABI is also involved in the preparation of a papaya mealybug technical brief and other communication materials to aid the management of the pest

A multi-stakeholder workshop co-financed by CABI’s Action on Invasive and Plantwise programs, was recently convened involving a technical team from project Implementing partners, representatives from Ministry of Agriculture, Livestock and Fisheries, Precision Agriculture for Development (PAD), and County governments of Kwale, Kilifi and Mombasa. Workshop participants reviewed the evidence of the impacts of papaya mealybug and how to best communicate the risks and Integrated Pest Management techniques to Kenya’s papaya farmers.

Additional information

Donors

Action on Invasives/Plantwise – DFID and DGIS
The Darwin Initiative

Partners

National Museums of Kenya
Natural History Museum, London
University of Nairobi
Kenya Plant Health Inspectorate Services
Kenya Agricultural and Livestock Research Organisation
Kenya Forestry Research Institute
Ministry of Agriculture, Livestock and Fisheries, Kenya
Precision Agriculture for Development