Idaho Weather Conditions Perfect For Wheat Fungus Outbreak, Expert Says

May 30, 2018

Resistant or semi-resistant wheat varieties account for over half of Idaho's wheat crop.
Credit Anna King / Northwest News Network

Winds from the Pacific coast bring much-needed rains to dry Southern Idaho this time of year. For wheat farmers, they may also carry a tiny threat: fungal spores, which cause stripe rust.

The disease has already been identified in Oregon and Washington. Juliet Marshall of the University of Idaho says that’s plenty close enough to spread to southern Idaho, where spring rains and cool evenings mean the blight could spread rapidly.

“The environmental conditions are perfect right now for stripe rust to take off,” says Marshall.

When spores land on wheat leaves, they cause ruptures to form in yellow stripes, hence the name: stripe rust. The ruptures dry out the plant and release additional spores into the air.

In recent years, many Idaho growers have switched to wheat varieties that are resistant to infection. But nearly half the state’s crop remains susceptible. In those varieties, stripe rust infections can reduce yields by up to 80 percent.

Twenty years ago, Marshall says, decades would pass between stripe rust outbreaks. But thanks to climate change, more spores survive the winter.

Marshall recommends keeping an eye out for tell-tale yellow stripes where wheat leaves have ruptured. And if you do find stripe rust, fungicides can be effective at stopping an outbreak.


Wheat is Idaho’s fourth-largest crop. Last year, total farm receipts amounted to nearly $450 million.


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