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Alfalfa is Nebraska’s third most valuable crop, and variety selection plays a key role in how well a stand performs over time. As you think about planting alfalfa this year, be sure disease resistance is part of that decision. Two of the most serious alfalfa diseases we deal with in Nebraska are Phytophthora root rot and anthracnose.
Phytophthora root rot is the most common root rot affecting alfalfa and can impact plants at any stage. It is most severe in poorly drained or saturated soils. In new seedings, it can cause damping-off and rapid seedling death under wet conditions, sometimes within just a few days. In established stands, infections damagethetaproot, leading to yield losses of up to 50 percent, gradual stand decline, and increased risk of winterkill.
Anthracnose can occur at any time of the year and affects alfalfa of all ages. It attacks stems and crowns, spreads quickly, and can significantly reduce production within one to two growing seasons. Disease stress also weakens plants, reducing their ability to withstand cold temperatures and increasing the risk of winter injury. Anthracnose spores spread easily by wind, rain, and harvesting equipment.
Multiple races of anthracnose cause economic damage in the Midwest, including races 1 and 2, along with the newer and more aggressive race 5. Race 5 has been confirmed in neighboring states and tends to show up earlier in the life of a stand. It is most aggressive during warm, moist conditions in mid-summer and fall.
While race 5 has not yet been lab-verified in Nebraska, its presence in surrounding states raises concern — especially since alfalfa is a longterm perennial crop. Planning ahead by selecting varieties with broad disease resistance can help protect stands over their full lifespan, particularly in fields with a history of anthracnose.
Because symptoms of both Phytophthora root rot and anthracnose are most severe in susceptible varieties, seed selection is the first line of defense. Select alfalfa varieties rated Resistant or Highly Resistant to both anthracnose and Phytophthora root rot to reduce yield loss and improve stand persistence. Work with your seed representative to understand resistance ratings, especially as new varieties become available this year.
One thing to keep in mind is that disease resistance doesn’t mean a variety is immune. Even highly resistant varieties can show some symptoms under heavy disease pressure, but the difference is how well those plants survive and recover. Resistant varieties maintain healthier crowns and root systems, which helps stands persist longer and continue producing.
It’s also important to match resistance to field conditions. Fields with heavier soils, poor drainage, or a history of stand loss are at greater risk for Phytophthora root rot. Fields with frequent harvest traffic or a history of stem disease are more prone to anthracnose. Knowing your field history can help guide better variety decisions.
At the end of the day, seed selection is one of the few disease management decisions you only get to make once. Taking the time now to choose varieties with strong resistance to Phytophthora root rot and anthracnose can help protect yield, stand life, and profitability for years to come. That upfront decision can save a lot of headaches down the road.
-Ben Beckman is a beef systems Extension Educator northeast Nebraska. He is based out of the Cedar County Extension office in Hartington. You can reach him by phone: (402) 254-6821 or email: ben. [email protected] mailto:[email protected]
