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[NAIROBI] A warming climate may extend the range of coffee's most devastating pest, affecting millions of tropical farmers, a new study warns.

The coffee berry borer already costs the industry US$0.5 billion a year — or more than three per cent of developing countries' coffee earnings last year — according to the International Coffee Organization.

Researchers from the Kenya-based International Centre of Insect Physiology and Ecology (ICIPE) say the small black beetle (Hypothenemus hampei) is capable of adapting to a wide range of temperature variations.

With global warming, they expect the beetle to spread both further north and south, thereby becoming a menace in sub-tropical coffee growing areas. Rising temperatures could also see it move to higher ground, the researchers say.

Juliana Jaramillo, ICIPE visiting scientist and lead author of a paper published earlier this month (3 August) in the journal PLoS ONE, told SciDev.Net that recent data from Indonesia and Uganda show that the borer has already expanded its altitudinal distribution range and is for the first time attacking plantations at sites as high as 1,800 metres above sea level.

The impact would be "particularly devastating" in areas where coffee trees produce fruit throughout the year, such as in Colombia, say the researchers.

Jaramillo says the borer reproduces faster as temperatures rise.

Her team's analysis of 32 years of climatic data in East Africa shows, for example, that before 1984 the Jimma area of Ethiopia was too cold for the borer to complete even one generation a year, but since then it has been able to complete one or two generations per year.

The researchers suggest the best strategy for coping with climate change is for farmers to grow more shade trees, which can reduce the temperature in plantations by up to two degrees Celsius and create more favourable conditions for the borer's natural enemies.

But Jaramillo emphasises that shading must be guided by ecological knowledge and specific plantation conditions, "as not all zones will work well with trees".

José Sette, head of operations at the International Coffee Organization, told SciDev.Net that his organisation is currently evaluating methods of pest control. Preliminary findings (mainly concerning trapping, spraying and biological agents) will be published in a few weeks.

Link to full paper in PLoS ONE


PLoS ONE doi 10.1371/journal.pone.0006487 (2009)