It's sweet victory over troublesome pest for pawpaw farmers

Dorcas Lekesio shows off a big pawpaw she has just plucked from one of the pawpaw trees on her farm, a big smile on her face.

For the longest time, Lekesio had suffered loss season after season due to papaya mealybug attack on her crop.

But she can now afford a smile, thanks to a new technology in the control of the troublesome pest. 

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She is among the farmers who benefited from an initiative popularising the biological control of the papaya mealybug.

Last month, when Smart Harvest visited her farm in Perkerra Scheme, Baringo South, mealybugs had invaded her pawpaw.

She explained that the invasion started last year in March, as the fruits started to dry.

Her neighbours had uprooted the cash crop, with some opting to venture into maize farming, but she held on in the hope that a solution to managing the pest would be found.

“We thank the Smart Harvest team for highlighting our plight. After the story was published last month, the Centre for Agriculture and Bioscience International (CABI) reached out to us,” she said.

Through sensitisation and capacity building by CABI, those who had abandoned pawpaw farming are slowly returning to it. 

Lekesio says with biocontrol, she can now plant more pawpaws in a bid to increase her income. 

The pests had primarily attacked the leaves and flowers, causing them to dry up and stunting the plant’s growth.

“The process of buying chemicals every week to contain the situation was financially draining, and some abandoned the venture, but with biocontrol, we are getting the better of mealybug,” she added.

Biocontrol is a method of managing pests using natural predators, parasitoids, or pathogens.

This approach partners with nature to maintain the balance of ecosystems and protect crops without resorting to harmful chemicals.

In this type of pest control, beneficial organisms like parasitic wasps and predatory mites are introduced into crops to prey on or parasitise harmful pests like aphids, spider mites, whiteflies or caterpillars.

Microbial insecticides, which are composed of naturally occurring bacteria, viruses, or fungi; can be used to target specific pest species while leaving non-target organisms unharmed.

Unlike chemical pesticides, which can have detrimental effects on ecosystems, biological pest control uses natural mechanisms, such as predators, parasites, and beneficial microorganisms to keep pest populations at bay.

Lekesio ventured into pawpaw farming five years ago on her three-acre farm. Before employing biocontrol of mealybug, she would harvest 10-15 bags per acre, earning Sh3,000 per bag.

But following the mealybugs infestation, she uprooted an acre, with the remaining acres producing 200kg.

A distance from Lekesio’s farm is Robert Cheretei, who began pawpaw farming 10 years ago. Last year, mealybugs destroyed the crop on his two-acre farm.

He resorted to the use of tobacco to contain the situation in vain.

When the farmers’ plight was highlighted by Smart Harvest, CABI responded with the introduction of biocontrol of the pest.

“The introduction of wasps on our farms has helped contain the menace. I am now able to support my family again as the crop is my main source of livelihood,” said Cheretei.

“After the mealybug invasion, one of my children who is in university was forced to defer his studies, but I’m hopeful things will normalise now,” he said.

Cheretei said that he used Sh7,000 weekly on chemicals, which was not sustainable.

Before the pest invasions, he used to harvest up to three tonnes of fruit weekly, but this fell to 0.7 tonnes.

Samson Bett, a farmer from Mogotio, ventured into pawpaw farming in 2019, and by 2022 had over 2,500 pawpaw plants.

He first noticed some white-coated masks on the pawpaws, and on doing some research online, he learnt that alcohol could be used to eliminate the pest. However, the problem only worsened.

“It was frustrating, but it’s a relief now with the use of biocontrol. It is a turning point for farmers,” he said.

Currently, he has  400 plants, down from 2,500, but is optimistic about raising the number once the pests are brought under control.

Invasive species 

Dr Selpha Miller, from CABI’s management team, noted that papaya mealybug is an invasive pest originally from Central America and Mexico, which invaded Kenya in 2016.

Mealybug, Miller said, attacks the fruit and leaves, producing a white mask over them, causing the plant to rot.

“Mealybug invasion was first reported in the Coastal region, which led to 91 per cent yield loss,” she said.

Dr Miller explained that when the first case was reported, farmers cut down their plantations after pesticides failed to bring it under control. 

CABI has been working on the biocontrol of papaya mealybug in East Africa for several years in partnership with Kenya Agricultural & Livestock Research Organisation (Kalro),  Kenya Plant Health Inspectorate Service (Kephis), National Agricultural Research Organisation (Naro)-Uganda, the University of Juba, and the National Museums of Kenya.

In 2019 following research, Acerophagus papaya (tiny wasp), was brought from Western Africa and found to be effective in controlling papaya mealybug as it feeds on the pest, killing it.

“Science is helping farmers slow down the spread of papaya mealybug. research has made an exciting discovery. Parasitic wasps can help control this pest,” said Dr Miller.

Biocontrol, she added, has worked effectively in the Coast region after four months of use with around 301 farmers benefiting.

Mealybugs have spread to other pawpaw-growing counties, including Machakos Makueni, Tharaka Nithi and Embu, where CABI is also conducting similar initiatives.

“When we saw the story about Perkerra farmers, we came to collect data and moved into action,” she said.

The wasps she said are given to farmers for free.

“In this case, parasitic wasps control papaya mealybugs by laying eggs inside them, wasp larvae then consume the bugs, which ultimately leads to the bugs’ death, providing effective natural pest control,” said Dr Miller.