Papaya was an important crop in Ghana in 2008. Farmers grew 2,510 ha of the fruit, and Ghana was the fourth largest exporter of papaya to the EU. In 2008, 978 tons of papaya reached international markets. Ghana’s papaya exports to Europe in 2008 were valued at 1.57 million Euros ($2.15 million). 

Disaster hit in 2009, when the papaya mealy bug (Paracoccus marginatus), originally from Latin America, destroyed around 85 percent of the crop and led to a 65 percent drop in exports. The fruit virtually disappeared from local markets. In 2010 no papaya was exported from Ghana. Commercial, post-harvest processing basically stopped and 1,734 people lost their jobs in packing and exporting the fruit.

In 2012, with the help of IITA (International Institute of Tropical Agriculture), MoFA (Ghana’s Ministry of Food and Agriculture) introduced a parasitic wasp (Acerophagus papayae) from Puerto Rico. The work was funded by the FAO at a cost of $195,000. That may sound like a lot, but it is a mere 10 percent of the value of exports to Europe in 2008.

The wasp parasitizes the mealy bug, killing the pest without chemicals. The tiny wasp is harmless to humans and reproduces on its own in farmers’ groves and gardens.

By 2013 papaya farmers were expanding their farms and hiring more workers. By 2014 more papaya fruit is on sale in the local market, and processing factories have bounced back and have taken on some workers. Although the papaya sector has not fully recovered yet, it is on its way, especially on larger, commercial farms that have more access to information.

Entomologists like this type of research (classical biological control) not only because it offers a “natural� solution, but because the work is challenging and can be done on a research station, with a few screen houses for rearing the plants, the pest and the natural enemy, which can then be released onto farms.

So although beneficial insects, like this wasp, can be introduced into a country without involving farmers, it is crucial to get all the farmers on board as soon as the wasp is released. But it costs money to inform extension agents and farmers.

In the central city of Kumasi, Giftie Boakya, an extension agent, said that researchers told her to inform farmers not to spray their papaya trees, but did not give her money to run an information campaign.

On 30 January, I visited a local group with the inspiring name “Peace and Love Farmers’ Association� on the outskirts of Kumasi. They are so close to the city that they built a wall around their land to protect it from would-be home builders. Being close to town is also an advantage, because the farmers can sell fresh produce. They specialize in nice fruits and vegetables, including papaya. When I asked them about the papaya mealy bug and its wasp, the group members had never heard of it.

If a well-connected, well-organized group like this has not heard of the beneficial insect, it means that more remote villagers certainly have not heard either. Now that the wasp is establishing itself, at least in some areas, smallholder farmers deserve a mass media campaign, explaining how the wasps live and why it is important to protect them by avoiding pesticides. Research and extension need to go hand in hand, or at least one after the other. Even a high-technology solution like classical biological control needs the participation of farmers to work in the long run.

Thanks to Felicia Ansah-Amprofi, Copperfield Banini, Emmanuel Nah, and Giftie Boakya of MoFA, Vikas Choudhary of the World Bank, and the members of the Peace and Love Farmers’ Association.

Watch a video on Managing mealybugs in cassava made in Thailand by Agro-Insight with CIAT.