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Navigating Winter Injury in Alfalfa Stands: Assessment, Management, and Interseeding Strategies

February 28, 2024 5:25 PM
Blog Post

High February temperatures have prompted many alfalfa fields across the state to initiate greening up over the past couple of weeks (Figure 1). However, temperatures then plummeted (9°F) earlier this week, likely resulting in the demise of the new growth. But the more pressing question is whether this has led to stand damage or crown injury. Furthermore, this winter has witnessed numerous warm and extremely cold days. As spring approaches, evaluating your alfalfa stand for winter injury and potential yields becomes crucial to inform rotation and interseeding decisions.

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Watch Alfalfa for Blister Beetles

July 14, 2023 11:51 AM
Blog Post

Blister beetles are an occasional late-summer problem in Iowa alfalfa fields. The beetles feed on alfalfa and soybean foliage, but leaf loss is not of economic importance. The bigger concern with blister beetles is their toxicity to livestock when accidentally consumed in feed. The beetles produce cantharidin, an irritant that causes painful blistering when the insects are handled. The cantharidin remains in the beetle’s body even after it dies and can cause health issues in livestock when dead blister beetles are consumed with hay.

Scout Now for True Armyworm in Pastures and Hay as well as Corn and Soybean

June 15, 2023 11:51 AM
Blog Post

On June 14, Iowa State University extension entomologists put out a Pest Alert to scout for true armyworm because of statewide reports of this pest feeding on crops. In addition, there have been multiple reports, primarily coming out of northeast Iowa, regarding true armyworm feeding in hay and pastures. Now is the time to scout to determine if a treatment is warranted. 

Plant Injury

Online Tool Helps Farmers Harvest Alfalfa at the Right Time

May 10, 2023
Alfalfa measurement.

Alfalfa growth has been slow this spring due to cooler than normal weather. This is a good reminder that using a calendar date to determine when to harvest the first crop of alfalfa may not be the best method. A better way to make harvest decisions is the PEAQ method (Predictive Equations for Alfalfa Quality) which takes several factors into account to roughly estimate the relative feed value (RFV) of standing alfalfa in the field.

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Alfalfa Weevil Larvae Active in Southern Iowa

April 20, 2023
Accumulated growing degree days graphic.

In addition to checking alfalfa stands for winter injury, it is time to start thinking about scouting for alfalfa weevil. Despite recent warm temperatures, alfalfa weevil development is slightly behind last year. However, it is likely adults have emerged from their overwintering sites to lay eggs in alfalfa stems in southern Iowa.

Scouting for Winter Injury in Alfalfa Fields

April 7, 2023
winterkill in alfalfa.

While row crops are generally the focus of attention this time of year, spring is a great time to scout for winter injury in alfalfa fields and assess stand health. This is especially true if stands did not have adequate snow cover or were covered by sheets of ice during the winter. Several other factors may contribute to alfalfa winter injury, including soil moisture, 4-inch soil temperatures, and other stresses like soil fertility, stubble height, as well as the age of the stand.

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Aphids Showing up in Alfalfa

May 18, 2022
Common aphids in Iowa alfalfa.

Aphids are common insects to see in field crops, especially in alfalfa. In Iowa, there are at least four aphid species that colonize this crop. A quick scouting bout in central Iowa yesterday (May 17) revealed at least two species feeding within the same field. Learning to distinguish aphids in alfalfa takes a little practice, but is worth knowing for making sound treatment decisions.

When is it too Late to Seed Forages?

May 6, 2022
Young forages growing in field.

With the cool and wet spring in 2022, there haven’t been many opportunities to seed forages. Looking at the calendar date, is it getting too late to plant forages? The short answer is that there is still some time to seed forages this spring. While the typical planting window is late February (frost seeding) through late April, planting forages in May can still be successful. For areas south of I-80, agronomists suggest seeding by the middle of May, whereas north of I-80 could get by seeding even a little later in May.

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Estimating First Crop Alfalfa Harvest using PEAQ

May 6, 2022
alfalfa measurement against ruler

Alfalfa growth and development is affected by many factors, including temperature, soil moisture, stand age and even cultivar. Alfalfa growth has been slow this spring due to cooler than normal weather. This is a reminder that using the calendar date to determine when to harvest the first crop of alfalfa may not be the best method. In order to accurately predict the optimal time for the first cutting, the University of Wisconsin developed the Predictive Equations for Alfalfa Quality (PEAQ) method.

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