The invasive pest papaya mealybug (PMB) (Paracoccus marginatus) results in high yield losses and increased production costs for smallholder farmers. In Kenya, PMB was first recorded in Mombasa in 2016 and has since spread to become a serious pest, resulting in severe yield losses of between 57% and 91% and household economic losses of £2,224/ha (USD 2,809) annually.

For years, farmers have primarily depended on chemical pesticides to control PMB, but these are associated with concerns around environment and health. Instead, integrated pest management (IPM), including classical biological control (biocontrol), offers high potential as an alternative for controlling PMB. For example, the parasitic wasp Acerophagus papayae has proven very efficacious in managing PMB in countries where it has been released, including Ghana.

In December 2020, A. papayae was evaluated under laboratory conditions and subsequently approved as a classical biocontrol agent by the Kenya Technical Standing Committee on Imports and Exports (KSTCIE). Following mass rearing and subsequent small-scale field releases at six research sites around Mombasa, Kwale, and Kilifi coastal counties, the parasitoid was effectively established at papaya farms, confirming A. papayae’s potential as a valuable form of PMB biocontrol in Kenya and elsewhere in Africa.

Prior to any field releases of A. papayae in Kenya, a study was also conducted to determine smallholder farmers’ knowledge, attitudes, and practices (KAP) towards biocontrol. Obtaining their perceptions was key, as farmers are often overlooked despite being recognised as hugely important players in decision-making on pest management practices. Subsequently, following initial field releases of A. papayae, a follow-up study took place in 2022 to determine any changes in farmers’ KAP towards biocontrol, as well as any changes in papaya yield and subsequent farmer income.