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  • Model reveals hidden threats to cassava

[CALI, COLOMBIA] Key cassava-producing regions thought to be safe may actually be hotspots for diseases and pests waiting to strike, a modelling study suggests.

Researchers from the International Center for Tropical Agriculture (CIAT) in Colombia incorporated the current geographic distribution of four threats to cassava production — cassava brown streak disease, cassava mosaic disease, green mite and whitefly — into ecological niche models to predict their potential distribution.

They found that some of the world's major cassava-producing areas are at risk, including Africa's Rift Valley, Mato Grosso state in Brazil, southern India, the northern parts of South America, and much of South-East Asia.

Their research was published in the journal Food Security last month (9 August).

Cassava is the third most important food crop in the tropics, after rice and maize. It is consumed by up to one billion people and provides important income for smallholder farmers.

"Historically, cassava pests and diseases have demonstrated a remarkable ability to colonise new areas in new countries, if conditions are favourable," said Tony Bellotti, a researcher at CIAT and one of the study's authors. "In an age of global travel … all it takes is one contaminated stake and a pest or disease could jump an entire continent and establish itself very quickly."

Beatriz Vanessa Herrera Campo, another of the authors, told SciDev.Net: "The focus of the research was to identify the areas where these threats could have favourable ambient conditions to spread. This information is a first step [towards] controlling the menace."

Herrera added that the cassava community should introduce early warning systems to help them deal swiftly with outbreaks.

Camilo López, who studies the genes underlying cassava's immunity to disease at the National University of Colombia, said: "The importance of this work is [its] determination, based on actual data and modelling, of the kinds of diseases and pests that could affect cassava crops in which regions."

This study sends an "alert signal" for institutions to monitor pests and diseases and to propose prevention strategies, López added.

Steve Yaninek, head of the entomology department at Purdue University, United States, outlined the steps needed to protect cassava from these disease or pest outbreaks.

"The predictions in the model need to be ground-truthed to identify where the real problems are. National programme experts must be empowered to maintain vigilance in areas of significant cassava production. And, finally, resources must be made available to develop new control technologies that address the evolving nature of some of these pests and the widely different production systems found globally," he said.

References

Food Security doi: 10.1007/s12571-011-0141-4 (2011)

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