The scope, scale, and impact of aphanomyces in Montana and North Dakota


Aphanomyces is a destructive, persistent root disease of pulses that’s wreaking havoc on pea and lentil crops in Saskatchewan, Montana and North Dakota.

In the last 20 years, pulses have become a very common rotation crop for these areas, as they do well in dry conditions. However, with the introduction of more pea and lentil crops in the mix came the added risk of aphanomyces, and it’s a problem that is growing in scope, scale, and cost.

Blake Rasmussen farms near Plentywood, Montana, and has seen first-hand the destruction aphanomyces can cause in a pea or lentil crop. “What we thought was a sustainable rotation of durum/lentil/durum/pea with maybe a chickpea in the mix has turned out not to be,” he says.

Jeannie Rude, agronomist with PRO Co-op, explains that prior to pulses the area was a wheat/fallow area with no disturbance no-till. The addition of pulses not only brought new crops to the area, they brought profit to the farmers and helped grow the community.

That’s why the threat of aphanomyces and fusarium root rot and how to manage for these diseases is a key focus of the North Central IPM Center through the United States Department of Agriculture’s National Institute of Food and Agriculture and work happening through the Montana State and North Dakota State University’s Pulse Working Group.

Rude explains that they’ve already learned that earlier sampling of fields is required to determine the presence of aphanomyces, as testing too late results in finding fusarium root rot, but missing aphanomyces.

Rasmussen says the cost of the disease is in the hundred of thousands for his farm alone. When seen from above (in the video), it’s clear that some areas of what could be an $800/ac income will yield nothing.

This video was made possible with support from North Dakota State University, Montana State, Pulse Crops Working Group and the National Institute of Food and Agriculture-USDA through the North Central IPM Center. For more information on this research, visit


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