• Researchers using tiny wasp to prevent the damage caused by the mealybug.
• The papaya mealybug (Paracoccus marginatus) is a serious pest of papaya fruit.
Researchers have developed an initiative to combat the destructive papaya mealybug in Kenya.
Researchers at the Centre for Agriculture and Bioscience International (Cabi) have introduced a parasitic wasp, a natural predator, to coastal counties to help control the papaya mealybug pest.
The tiny wasp helps to prevent the damage caused by the mealybug, it does not affect the fruit but only attacks the papaya mealybug by laying eggs on the pest until it dies.
The papaya mealybug (Paracoccus marginatus) is a serious pest of papaya fruit.
Abdul Rehman, an expert from Cabi said the sap-sucking insect originated from Central America and then spread to the Caribbean and South America in the 1990s.
It was first detected in Africa in 2010 and by 2016, it had been found in Ghana as well as Mombasa County in Kenya. Cabi researchers have now discovered the mealybug in more than half of Kenya.
Data shows that the pest causes crop losses of 53-100 per cent and it is responsible for economic losses of Sh354,000 (£2,224) per hectare every year forcing some smallholders to abandon papaya farming.
Rehman said through PlantwisePlus, CABI has worked with partners to release this wasp in three counties in Kenya.
“Within a year of its release from July 2022 to July 2023, the wasp established itself at the release sites in Kilifi, Kwale and Mombasa. This means its numbers are growing and the hope is that it will successfully control the papaya pest along Kenya’s coastline,” he said.
In 2021, Cabi held a meeting with stakeholders from Kenya’s county and national governments to find solutions to controlling papaya mealybug.
The meeting was held with partners, Kenya Agricultural and Livestock Research Organisation (KALRO), Kenya Plant Health Inspectorate Service (KEPHIS), and National Museums of Kenya. Farmers from the three target counties also attended.
In 2022, Cabi together with KALRO and KEPHIS, trained extension officers in pest control. The goal was to protect native insect biodiversity threatened by pesticide use.
“For the wasp release to work, pesticide use would need to be controlled. Pesticides kill pests, but they kill beneficial insects, too. Extension officers paved the way for creating the right release environment,” he added.
The project team selected six farms that weren’t using insecticides. This would ensure a natural pest control environment. Each farm also had more than 100 trees of the right spacing for the release to work.
In 2022, the team reared wasps in special facilities. The training helped to dramatically increase the rearing of the wasps.
The numbers grew from 500 in January 2022 to 3,210 in March. Training boosted the numbers to 13,295 by April.
Rehman who is a CABI expert in mass rearing the wasps based in Pakistan, trained technical personnel in Kenya, and by May, the wasps’ numbers had been scaled up to 18,185.
“The outcome from this study provides strong evidence of the exceptional efficiency of the wasp. It shows how it can manage the papaya mealybug population in coastal Kenya,”Rehman said.
“Cabi has also trained farmers to establish Natural Enemies Field Reservoirs (NEFRs). The reservoirs are storage boxes where beneficial pest predators can be reared.
"The project is doing this so that farmers can rear their own wasps on-site. This will help to conserve the parasitoids in communities when the project ends."