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[KAMPALA] East Africa's horticulture could face a severe crisis due to 'species jump' — whereby a disease moves from a known host to new and unusual ones — affecting fruits, vegetables, and medicinal and ornamental plants.

Researchers in Uganda have discovered that the Black Coffee Twig Borer, a devastating coffee pest, has crossed over from Robusta coffee to about 40 plant species including avocadoes, cocoa, eggplant, ginger, guavas, jackfruit, mangoes and tomatoes.

"Sooner rather than later it will also cross over to tea" — another major cash crop in the East Africa region — Africano Kangire, director of Uganda's Coffee Research Institute (CORI), tells SciDev.Net.

The researchers who addressed the media at CORI last month (6 February) say the pest has badly hit coffee farming in the region, especially in Uganda, where the indigenous Robusta coffee is widely grown.

"It has been reported in many countries in Africa, including Kenya and northern Tanzania, which are already highly infested," says Godfrey Kagezi, a researcher and entomologist at the Coffee Research Centre (COREC), based at the National Agricultural Research Organisation.

A 2012/13 COREC survey, as well as various reports by the Uganda Coffee Development Authority, show that the pest is rapidly spreading from Bundibugyo, western Uganda, where it was first reported in 1993, to other parts of the country. 

The research also shows that more than 40 plant species in over 17 families are potential hosts for the pest.

According to Kagezi, it is yet to be identified in Burundi and Rwanda.

But he also flags up issues with data collection in the region: there is not enough information available on whether the disease has spread to the Democratic Republic of Congo, and all three countries need comprehensive surveys.

The pest, native to Asia, has slowly spread to the rest of the world. When the small black beetle attacks coffee, it destroys 90 per cent of the plant, as it does with both fruit and vegetables. 

"Most research [regionally] has been done on coffee only and not in relation to other tree crops," says Kenneth Masuki, a researcher with the Association for Strengthening Agricultural Research in Eastern and Central Africa.

Scientists say temperature rises related to climate change could be responsible increasing the spread of species jump by creating an enabling environment for their survival.

Patrick Kucel, a COREC plant entomologist, says the pest's high reproductive ability also makes it difficult to control: the female pest is capable of reproducing both sexually and asexually, and produces about 20 offspring per week — a peculiarity among its group.

Kucel says better management practices to help reduce or eliminate infestation sources must be implemented.

This article has been produced by SciDev.Net's Sub-Saharan Africa desk.