Deadly papaya pest detected in Tanzania

papaya field
Copyright: G.M.B. Akash/Panos

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  • It was first found in Africa in Ghana, and spread to four other African nations
  • Its detection in Tanzania could affect many crops and the rest of East Africa
  • Experts say biological control and inspecting plant parts could help fight it

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[NAIROBI] A destructive pest that attacks papaya plants and other crops, and was first detected on the continent in West Africa has moved to the East African coast, according to experts.
Scientists at the International Institute for Tropical Agriculture (IITA) in Tanzania fear that the deadly pest could put food security and the livelihoods of hundreds of thousands of farmersat risk.
The papaya mealybug, also called Paracoccus marginatus, has been detected in Tanzania’s coastal areas and in Zanzibar island, thus triggering alarm among the region’s scientific and agriculture community, who have initiated efforts to prevent it from spreading.

“The climates of coastal West Africa and coastal East Africa are similarly tropical and humid, and these conditions clearly favour the pest.”

James Legg, International Institute for Tropical Agriculture (IITA) in Tanzania

“Samples sent to IITA's Biological Control Centre for Africa, Cotonou, Benin, have been positively identified,” said the IITA, one of the organisations involved in curbing the spread, in a statement released on 20 April. “The mealybug[s] are easily blown by the wind or carried by ants from one plant to another. They are transported [over] longer distances by people who unknowingly carry infested plants or fruit from one part of the country to another, or from country to country.”
James Legg, an entomologist with the IITA in Tanzania, who is leading the pest control initiative, told SciDev.Net: “It is most likely that the insects that came to Tanzania arrived from South Asia, since their occurrence has not been recorded in central African countries and there is significant trade between Asia and coastal East Africa.
He added: “It is true, however, that the climates of coastal West Africa and coastal East Africa are similarly tropical and humid, and these conditions clearly favour the pest.”
According to Legg, who first detected the pest in Tanzania, the insect could spread to other parts of the East African coast, including the Kenyan coast in the coming two years.
Douglas Miano, a lecturer at Kenya-based University of Nairobi’s Department of Plant Science and Crop Protection, suggests a way to help control the pest, which attacks the leaves, branches and fruits of the target plant: “Inspecting plant material would greatly help to control the spread of the pest,” Miano says.
Legg says that the IITA, the United Nation’s Food and Agriculture Organization (FAO) and Tanzania’s Ministry of Agriculture are mobilising funds for a fighting the pest through biological control.
He notes that by introducing tiny insects called parasitoids that feed on the papaya mealybug, it could be controlled.

”The parasitoids to be introduced in Tanzania should spread rapidly and may only take two to three years to control the pest, although as [it] always happens with biological control, the pest will remain present but at much lower and non-damaging levels,” Legg explains.
The papaya mealybug has its origin in Mexico and was first observed on the African continent in Ghana in 2010 from where it spread to Benin, Gabon, Nigeria and Togo.
While papayas are its preferred host, the insect also affects a wide range of crops, including cassava, beans, coffee, pepper, melon, guava, tomato, eggplant, cotton and jatropha, according to the IITA, implying that it could cause massive losses to economies if not controlled on time.
This article has been produced by SciDev.Net'sSub-Saharan Africa desk.