Will your alfalfa stands make it through the winter? As temperatures drop and the snow begins to fall, this question probably pops into your mind frequently. And, it may make you especially nervous if you didn't assess your alfalfa's risk of winter injury this fall.
September was a good time to assess your risk of alfalfa winter injury, the degree to which all alfalfa buds formed in the fall are able to grow in the spring. However, September may have slipped by, leaving you with alfalfa fields left unchecked. That could set your fields up for winter injury and leave you with poor quality forage and lower yields next spring. Take the following quiz to determine your risk of alfalfa winter injury.
For each section, determine the point value. Then, add up the points from each section to determine your final score. That will help you assess your alfalfa's winter-injury risk.
1. Determine alfalfa stand age
The older an alfalfa stand is, the greater the risk for winter injury.
"A new seeding is the most winterhardy," says Dan Undersander, extension agronomist at the University of Wisconsin. As the stand ages and plants become larger, they become more diseased, and more susceptible to injury. That, in turn, makes the plants more susceptible to winter injury.
A. Is your alfalfa stand greater than three years old? (4 pts)
B. Is the stand two to three years old? (2 pts)
C. Is the stand less than one year old? (1 pt)
2. Determine your alfalfa variety's disease resistance
Make a list of the diseases which have occurred in your fields in the past few years. Then, refer to your seed company's product literature to determine if your alfalfa varieties protect against these diseases. It's important to know this, since alfalfa weakened by disease becomes more susceptible to winter injury.
Most improved alfalfa varieties have high resistance to these five major diseases: bacterial wilt, Phytophthora root rot, Fusarium wilt, Verticillium wilt and anthracnose, Undersander says. However, if your variety doesn't exhibit high resistance, and one of these diseases lurks in your fields, your alfalfa stands a greater chance of suffering winter injury.
A. Is your stand moderately resistant to bacterial wilt only? (4 pts)
B. Is it moderately resistant to bacterial wilt, plus either Phytophthora root rot, Fusarium wilt, or anthracnose? (3 pts)
C. Is the stand moderately resistant to all the diseases mentioned? (1 pt)
3. Assess your alfalfa variety's winterhardiness score
Check your seed company's product literature to determine your alfalfa varieties' level of winterhardiness and compare the score to the "Alfalfa winter survival index" below. If your varieties don't have winter survival scores which match your needs, your alfalfa stands have a greater chance of suffering winter injury. Winter survival indexes will vary, depending on your location and alfalfa management practices. (See the map, "Winterhardiness zones,")
A. Does your variety have a winterhardiness score one point higher than that recommended for your region (Such as a score of 3.0 when the suggested winterhardiness score is 2.0)? (3 pts)
B. Does your variety have a winterhardiness score equal to that recommended for your region? (2 pts)
C. Does your variety have a winterhardiness score one point less than that recommended for your region (Such as a score of 2.0 when the suggested winterhardiness score is 3.0)? (1 pt)