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Rising temperatures lead to proliferation of coffee diseases

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The rise in temperatures due to climate change is leading to the proliferation of the coffee berry borer, one of the crop’s most devastating pests, leading to losses in coffee production at a time when coffee has started to gain its lost glory, scientists at International Center of Insect Physiology and Ecology have warned.

Researchers estimate the coffee berry borer causes more than $500m in damages each year globally, and affects 20m coffee producing families worldwide, making it the most costly pest affecting coffee today. According to the researchers, the insects thrive in warmer temperatures, with an increase in temperatures in coffee growing areas now sparking a rapid increase in the insect. This has seen the ICIPE-led team now set out to explain how shifts in the distribution of the pest might affect Arabica coffee production in the future, in order that growers can develop appropriate adaptation strategies.

The scientists are building on their pioneering work published last year, which predicted that even small increases in temperature would have serious consequences on the number of generations, as well as the latitudinal and altitudinal range of the borer, adversely affecting coffee production in East Africa and parts of South America.

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The Arabica coffee grown in Kenya, Ethiopia and Latin America is an especially climate-sensitive crop. It requires just the right amount of rain and an average annual temperature between 64 degrees Fahrenheit and 70 degrees Fahrenheit to prosper. As temperatures rise – Kenya’s average low temperature has increased by about .66 degrees F every decade since 1951, according to the National Meteorological Department – and rains become more variable, Kenyan coffee farmers have suffered increasingly poor yields. Against this backdrop, a subsequent invasion by the insect would be catastrophic.

 Colombia, once the leading coffee exporter in the world, suffered a massive invasion of the insect in the mid 1990’s. It regularly sent abroad more than 12m bags of Arabica coffee each year. But production has not reached that level since 1994, and 2009 was the country’s worst year ever.

At an International Coffee Organization meeting in February, a Colombian coffee representative revealed that the country’s coffee exports had dipped to 7.9m bags last year and that infestation by the borer — along with excessive rainfall and reduced application of fertilizer — was partly to blame. Scientists at ICIPE warn that Kenya too could be heading down the Colombian path. Coffee Berry Borer, also known widely as Broca, is a small beetle native to Africa – though its effects are now global. It destroys crops by using the fruit as a home for its young. The female beetle burrows into the fruit and lays eggs inside.

These eggs hatch and the larvae eat the coffee seeds from the inside out. By doing this they massively reduce income for coffee producers by reducing both yield and quality. In reality, female borers actually kill coffee plants by laying their eggs in the berries. Each female can lay up to 200 eggs, and the resulting damage attracts herbivores and pathogens.

While farmers have been toying with the idea of moving their coffee to higher altitudes where the insect is rare, experts say that the coffee berry borer could also be more difficult to control at higher altitudes, since moving a pest into a new ecosystem makes its behavior harder to predict. For example, insects that could serve as natural enemies to the coffee berry borer may not interact with the beetle in the same way at higher elevations.

“Natural enemies can be very useful in pest control, but their cycle has to be in sync with the pest’s,” said a researcher at ICIPE involved in the study. Moreover, soil conditions at higher altitudes might not be suitable for Arabica coffee. The scientists therefore suggest that a more practical way to adapt to the rising temperatures is to introduce shade trees in coffee plantations, as this considerably improves the microclimate and favours the growth of coffee.

Studies from the Integrated Pest Management Centre have shown that shade trees can reduce the temperature around coffee leaves by 3 degrees F to 7 degrees F, depending on the environment. There is also evidence that shade-grown coffee plants produce higher-quality coffee. But many coffee growers have cut down the trees around their coffee plants in order to increase sun access.

The ICIPE scientists are likewise encouraging coffee farmers to intercrop their plants with bananas, known to boost coffee yields, to reduce the impact of the borer.

A meeting of African scientists early this year to address the dangers of climate change in agriculture said that Africa’s arable land was expected to shrink by 60m to 90m hectares by 2030 as the impact of climate change sets in.

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Kenya exported 421m kg of coffee last year after a long lull in production due to farmers’s discontent with a poor paying crop. The government invested heavily in resuscitating the coffee industry by paying heavy incentives to farmers to encourage them to invest in the coffee.

Although coffee Robusta traditionally dominated in the country, in the last decade the government has been encouraging farmers to invest in coffee Arabica which is preferred in the international market due to its richer flavour.

“Although we are looking at all avenues of containing the coffee borer insect thanks to timely research by our institutions, we are worried of what this might do to the coffee industry that has struggled so much to pick up. We are however in constant communication with the research institutions on how we will train farmers on fighting the pest,” said Dr Mworia from the Ministry of Agriculture.

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