Scientists deploy wasps to control devastating tomato pest in Africa

Seasonal farm labourers pick tomatoes on a farm in the Boland region of the Cape Province. These tomatoes were destined to go to a canning factory to be made into tinned tomatoes. These workers are part of the so-called coloured or mixed race community in South Africa who often feel left out of the political process in the country. | Location: Mcgregor, South Africa. (Photo by Gideon Mendel/Corbis via Getty Images)
Seasonal farm labourers pick tomatoes on a farm in the Boland region of South Africa’s Cape Province. Some regions of Africa have been plagued for years by destructive pests targeting tomato crops. (Photo by Gideon Mendel/Corbis via Getty Images)

Scientists at the Nairobi-based International Centre of Insect Physiology and Ecology (Icipe) have turned to wasps to fight Tuta absoluta, a highly destructive tomato pest that was detected for the first time in Africa in 2008 and has since spread rapidly across the continent.

The wasps have been imported from Peru, the native home of the pest, and are being introduced outside its origin for the first time.

The wasp, known scientifically as Dolichogenidea gelichiidivoris, controls the tomato pest by laying its eggs inside it. The eggs eventually emerge as adult wasps thereby killing the larvae of the pest.

“The introduction of a natural enemy for Tuta absoluta is especially significant in view of enabling Africa tackle the rising threat of invasive species, and their dramatic effect on agriculture and livelihoods across the continent,” Sunday Ekesi, the Director of Research and Partnerships, at Icipe said in a statement on Friday.

The initial field releases of the natural enemy were done in Kirinyaga County, central Kenya, which is one of the largest producers of tomatoes in the country.

The wasp is expected to spread rapidly, in search of infested plant material. Subsequent releases are planned in other major tomato growing regions in Kenya, as well as Ethiopia.

Isaac Macharia, general manager, phytosanitary services at the Kenya Plant Health Inspectorate Service said they provided regulatory support for the importation and release of the important natural enemies to manage Tuta absoluta, a method that is environment friendly.

In the absence of effective control measures, the pest can cause 100 percent tomato yield loss.

In some countries like Nigeria, the moth is referred to as “tomato ebola” due to its severity and ability to completely ravage tomatoes.

“One of the main challenges in the control of Tuta absoluta is its fast reproduction rate, with many generations emerging per year. As such, the pest quickly develops resistance to major pesticides,” said Samira Mohamed, a senior scientist at Icipe.

“This scenario has forced farmers to apply broad-spectrum synthetic insecticides, often in extremely high doses, and far too frequently. This has led to increased production costs, and pesticide residues in yield with detrimental impact on the health of growers, consumers and the environment,” she added.

The tiny Tuta absoluta caterpillars damage tomatoes by tunnelling into leaves and eating the green parts, causing the leaves to dry out; and by burrowing into the fruits, resulting in deformities and rotting.