A Fungus Is Killing Wheat in Bangladesh and It's Threatening to Spread

In February, wheat farmers in Bangladesh noticed something unusual about their crops. Yellow and black spots appeared on the leaves and sheaves of wheat. Then, the plant heads gradually turned white and dried up before producing any grain.

Soon, those farmers were setting fire to their fields in a desperate effort to prevent the spread of a deadly disease that's now claimed 90 percent of the harvest from an estimated 15,000 hectares—58 square miles—of wheat so far. Scientists fear that if left to its own devices, the pathogen, known as wheat blast, could threaten wheat production throughout Southeast Asia.

Wheat blast is a nasty sucker, first identified in 1985 in Brazil and now also found in Bolivia, Paraguay, and a small corner of northeast Argentina. How it got across an ocean and all the way to Bangladesh is something of a mystery, but researchers suspect the wheat blast in Bangladesh originated in South America.

"This is a really big deal," Dr. Barbara Valent of Kansas State University, a plant pathologist who heads up the university's wheat blast team within the department of plant pathology, told MUNCHIES. "We're having trouble finding resistance to control this," she said. "When the weather is right for the fungus, there's really no way to control it. It really can devastate the fields."

Wheat is the second biggest food crop in Southeast Asia after rice—and unfortunately, there's also such a thing as rice blast, though rice blast is easier to manage. Wheat blast (Magnaporthe oryzae, for those keeping score) is a fungal disease, and on wheat plants it takes out the grain-producing, spikey, nook and cranny-filled head of wheat, making it more difficult to treat with fungicide.

Wheat blast can easily spread from an infected plant to healthy wheat propelled by wind and rain. From time to time, wheat blast devastates wheat production in the countries where it is found in South America, where it has claimed up to 3 million hectares of fields since 1985. In 2009, it wiped out a third of the wheat crop in Brazil. Authorities in Bangladesh suspect that days of nonstop rain in early February helped spread the disease, and Valent notes that there is a correlation between El Niño and bad wheat blast outbreaks. Climate change could fuel wheat blast spread, too.

There isn't much natural resistance to wheat blast in wheat, and the possibility for wheat blast to spread rapidly necessitates quick intervention. Scientists are approaching wheat blast epidemics informed by how health officials try to manage virus outbreaks like Zika. A key component is identifying the strain of wheat blast, which then allows scientists to search for genes that could provide resistance.

Valent's lab at Kansas State has made progress in that area, and their research could be critical for biosecurity. Her lab uses genome sequencing to compare strains, and in March, she and her team published a study identifying a gene that reduced wheat blast by as much as 72 percent. Her team works with the USDA to study the disease, which could be a threat to wheat production worldwide, causing food shortages in developing nations and economic turmoil in developed countries. In 2011, a fungal disease related to wheat blast but independent from the kind of wheat blast in South America was found on a single head of wheat in Kentucky, but quickly eradicated.

A concern is that wheat blast can be seed-borne, meaning the disease could spread unwittingly by farmers while wheat is in the seed state. Valent's team has developed a technique to diagnose wheat blast in seeds, and she says treating seeds with fungicide will be key.

"The fact that this is in South Asia is extremely scary," Valent said. "It can spread now easily into India. People even in Australia are concerned."

But for now in Bangladesh, the best option for some farmers is to watch their fields burn. Some areas of South America know the helpless feeling all too well, and they have given up on growing wheat completely. There is, however, a glimmer of hope—with the strain of wheat blast identified, scientists can work toward putting a stop to its spread. Per usual, we're praying for science to save us.