By: Gloria Anderson, Nairobi Kenya
Barely two millimetres long, is a tiny parasitic wasp helping Kenyan farmers win back their papaya farms from a destructive pest that once threatened to wipe them out. The papaya mealybug, an invasive pest native to Mexico, first appeared in Kenya in 2016.
By the following year, the country’s papaya farms were in ruins. The pest spread quickly, feeding on papaya leaves, stems, and fruits leaving farmers devastated and forcing many to abandon their fields.
Papaya, which is Kenya’s fourth most important fruit crop, provides food, income, and nutrition to thousands of families. Its destruction not only hurt farmers but also affected national exports and local diets.
A Cry for Help, a Tiny Hero
As farmers cried out for help, scientists at the Centre for Agriculture and Bioscience International (CABI) began searching for a sustainable solution. They found inspiration in Ghana, where researchers had successfully used a natural enemy of the mealybug, a tiny wasp called Acerophagus papayae to fight the pest. Dr. Selpha Miller, an Invasive Species Scientist at CABI, visited Ghana to learn and take the solution back to help farmers there. She explained that Kenya imported the wasps from Ghana and adapted the method to make it more efficient.
“We learned how to produce and distribute the wasps while they are still in their ‘mummy’ stage,” she said. “That allowed us to produce more and reach about 995 farms so far.”
The wasps are reared in laboratories using potato sprouts. Once they develop, the mummified wasps are placed on small cards coated with glue and stapled under papaya leaves. When they hatch, the wasps immediately begin to attack and “mummify” the mealybugs stopping them from spreading.
Farmers Regain Hope
For farmers like Joseph, the change has been life-saving.
“We were struggling to control the pest because nothing worked at that time,” he said. “The extension officers told us not to spray chemicals since they were harmful. When I heard about biological control using natural enemies, I was excited. It’s good news for us farmers.”
Another farmer, Mary, who grows papaya, citrus, and bananas, recalled how tough things were before.
“The mealybugs destroyed about half of what I was supposed to harvest,” she said. “I used to spray chemicals every week, and it was very expensive. It was like we were sharing the yield 50–50.”
Today, Mary’s story is very different and she hopes to grow pawpaws because she is reaping a lot of benefits.
“Since using this biological control, I’m now saving a lot. Buyers come to my farm to buy fruits directly. My plan is to expand, grow more pawpaws, and support my children’s education,” she said proudly.
The Science Behind the Success
Dr. Miller explained that biological control takes time but works sustainably.
“Unlike pesticides that give instant results, this method takes about six months for the wasps to build up and control the pest population,” she said.
Even better, the wasps spread naturally to nearby farms. “Farmers who didn’t receive the wasps directly later benefited because they moved to their farms,” Dr. Miller added.
Through collaboration with partners like KALRO, KEPHIS, the National Museums of Kenya, and county governments, CABI’s intervention has restored papaya farming in counties such as Machakos, Makueni, Embu, Tharaka Nithi, and Baringo.
A Sustainable Future
Thanks to the tiny Acerophagus papayae, papaya farming in Kenya has been revived. Farmers have regained confidence, incomes are improving, and the country’s papaya industry is thriving once again.
With Ghana’s help many other countries have been helped through CABI’s support, where the model has been replicated in such countries.
Dr. Miller confirms this, “We’ve already supported Uganda, Tanzania, Rwanda, South Sudan, and Burundi,” she said. “If we work together, we can manage this pest across the region.”
From devastation to recovery, the story of Kenya’s papaya farmers shows that even the smallest creatures can make the biggest difference.
Gloria Anderson attended the IFAJ World Congress with sponsorship support from OFAB (Open Forum on Agricultural Biotechnology in Africa) a project of the AATF.
