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Study finds fungicide worsens coffee rust issue

By Yijia Zhou, Daily Staff Reporter
Published January 28, 2014

A cup of coffee can be a lifesaver in the morning — unless it's rusty, that is.

Recent reports from University researchers suggests that spraying fungicide is not the perfect cure for coffee rust, an environment disease that has devastated Latin American plantations since 2012 that is already causing significant losses in production.

In reality, it’s quite the opposite of a cure. According to University ecologists, using fungicide could make the situation worse, as it kills “good” fungus, which protects coffee from the disease.

In a Jun. 22 publication in BioScience, an academic journal, John Vandermeer, professor of ecology and evolutionary biology and his co-authors — Ivette Perfecto, professor of ecology, natural resources and environment and postdoctoral fellow Doug Jackson — discussed the possible harm that fungicide could bring to the ecological system. They also provided an alternative solution for killing the disease: The restoration of traditional shade-growing techniques.

Coffee rust disease, according to Vandermeer, is caused by Hemileia vastatrix, a fungus that mainly attacks coffee leaves. Pale yellow rust-like spots will appear on the leaves of infected coffee plants, which will then lose their leaves entirely and die from defoliation.

A disease that ravaged South Asia during in the 19th century, coffee rust had not been a significant threat to Latin American plantations until late 2012. Due to reasons not yet understood by scientists, it killed thousands of coffee trees in the region, resulting in immense economic losses.

Vandermeer said spraying fungicide and removing the plants’ sources of shade are the two most common ways to fight the disease in Latin America. However, both solutions create serious problems that may result in harming the complicated ecological system.

“Fungicide functions by killing any kind of fungus directly, and here’s the problem: The disease is caused by a fungus, but there are also several other kinds of fungi that would kill this fungus,” Vandermeer said. “So you kill the bad fungus and the good fungus at the same time when using the fungicide.”

He added that White Halo fungus is one of these “good” fungi that can help control the disease but is being killed inadvertently due to human behavior.

Additionally, abandoning traditional shade-growing techniques will not stop coffee rust dispersion. According to Vandermeer, it actually does the opposite.

He explained that the traditional plantation in Central America creates a canopy of shade for coffee, which resembles a forest system in its complexity.

“But people are removing the shades, thinking that if they get the coffee out to the full sun, then the fungus will stop growing,” Vandermeer said. “But we know as a fact that it does not work. In fact, you get more fungus when you have them in the sun instead of the shade.”

Exposure to sunlight does not kill the fungus, but the shade will lead to less wind, which is how the fungus spreads, according to Vandermeer.

The ecologist provided his recommendations for fighting the disease: to continue research on the fungus, return to shade-growing techniques and “definitely stop using fungicide.”

However, Vandermeer added that out that these solutions could face difficulties because they run counter to the interests of fungicide sellers.

“They run around telling people, ‘What you need is fungicide.’ It was the same thing with pesticide and our food system. And most farmers get their information from salespeople.”


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