Papaya is a nutritious and profitable crop that is widely grown by smallholder farmers in Kenya.
However, papaya production is threatened by various pests, especially the papaya mealybug (Paracoccus marginatus), an invasive alien species that can cause severe damage and yield losses.
Papaya mealybug: a devastating pest in Kenya
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The papaya mealybug is a tiny sap-sucking insect that feeds on the leaves, stems, fruits and roots of papaya plants, as well as other crops such as cassava, eggplant and tomato, as per Phys.org.
The mealybug infestation causes stunting, wilting, deformation and premature fruit drop, resulting in reduced quality and quantity of papaya production.
The mealybug also produces honeydew, a sugary substance that attracts ants and promotes the growth of sooty mold, a black fungus that reduces photosynthesis and affects the appearance of the fruits.
The papaya mealybug is native to Mexico and Central America, but it has spread to many tropical and subtropical regions of the world, including Africa, Asia and the Caribbean.
It was first detected in Kenya in 2016, and since then it has become a major pest of papaya and other crops in several counties.
The mealybug has no natural enemies in Kenya, and it can reproduce rapidly and disperse easily by wind or human activities.
To control the papaya mealybug, many farmers rely on chemical pesticides, which are readily available and perceived as effective.
However, chemical pesticides have several drawbacks, such as high cost, health risks, environmental pollution and pest resistance.
Moreover, chemical pesticides can kill beneficial insects that can help suppress the mealybug population naturally.
Biological control: a promising alternative for papaya mealybug management
Biological control is a method of pest management that uses natural enemies, such as predators, parasitoids or pathogens, to reduce the pest population to acceptable levels, as per Alpha Galileo.
Biological control is considered a more sustainable and environmentally friendly option than chemical pesticides, as it can provide long-term control, reduce pesticide use and residues, enhance biodiversity and ecosystem services, and improve human health and well-being.
One of the most successful examples of biological control for papaya mealybug is the introduction of a tiny wasp called Acerophagus papayae, which is a parasitoid of the mealybug.
The wasp lays its eggs inside the mealybug body, and the developing larvae feed on the mealybug from within, eventually killing it.
The wasp has been used to control the papaya mealybug in several countries, such as India, Indonesia and Thailand, where it has reduced the mealybug infestation by more than 90%.
In Kenya, a classical biological control (CBC) program for papaya mealybug was initiated in 2018 by CABI and partners, with support from the UK Foreign Commonwealth & Development Office (FCDO) through its Action on Invasives program.
The program involved importing Acerophagus papayae from India, rearing it in quarantine facilities in Kenya Agricultural & Livestock Research Organization (KALRO), releasing it in selected sites in four counties (Kilifi, Kwale, Makueni and Taita Taveta), and monitoring its establishment and impact on the mealybug population.
Papaya farmers' willingness to reduce pesticide use
To assess the knowledge, attitudes and practices of papaya farmers towards biological control and their willingness to reduce their chemical pesticide use to support the CBC program for papaya mealybug in Kenya, CABI researchers conducted a survey study involving 383 farming households in four counties where Acerophagus papayae was released, as per Mirage News.
The study also included key informant interviews with eight extension agents and thirty agro-dealers, and eight focus group discussions with farmers.
The study results were published in the CABI Agriculture and Bioscience journal1, and they revealed that:
Most farmers (94%) were aware of the negative impacts and risks associated with chemical pesticides on human health and the environment.
Most farmers (86%) had heard of biological control as a concept, but only 29% had used it before.
The main reasons for not using biological control were lack of awareness (46%), lack of availability (28%), concerns over efficacy (15%) and safety (9%).
Most farmers (95%) expressed interest in learning more about biological control for papaya mealybug.
Most farmers (93%) were willing to support the CBC program for papaya mealybug by participating in awareness-raising, capacity building and monitoring activities.
Most farmers (87%) were willing to reduce their chemical pesticide use to conserve Acerophagus papayae, provided that they receive adequate information, training and technical support from extension and agro-dealers.
Most farmers (82%) agreed that collective action among the community is necessary to ensure the success of the CBC program for papaya mealybug.
The study concluded that there is a high level of willingness and potential among papaya farmers in Kenya to reduce their chemical pesticide use and adopt biological control as a more sustainable and environmentally friendly option for papaya mealybug management.
However, the study also identified some challenges and gaps that need to be addressed, such as:
The need for more awareness-raising, capacity building and effective information dissemination on biological control among farmers, extension agents and agro-dealers.
The need for more availability and accessibility of biological control agents and products in the market.
The need for more research and evaluation on the efficacy, safety and socio-economic impact of biological control for papaya mealybug and other pests.
The need for more coordination and collaboration among stakeholders and agencies involved in biological control and invasive species management.
The study recommends that policy makers and practitioners should:
Support the CBC program for papaya mealybug by providing adequate resources, infrastructure and regulatory frameworks.
Promote the awareness, adoption and scaling up of biological control among farmers, extension agents and agro-dealers through education, training, demonstration and incentives.
Facilitate the availability and accessibility of biological control agents and products in the market through quality control, certification and subsidies.
Encourage the collective action and cooperation among the farming community to ensure the conservation and dissemination of biological control agents.
Monitor and evaluate the impact of biological control on the pest population, crop yield, income, health and environment.
