Southwest Michigan field crops update – May 8, 2025
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EmailCorn and soybeans started emerging, and wheat is at Feekes 8/9 (flag leaf emerging to fully emerged with ligule).
Weather
Precipitation over the past week totaled about 1 inch, depending on the area in southwest Michigan. Temperatures dropped over the weekend and have stayed relatively cool. Starting tomorrow, May 9, temperatures are expected to trend upward and enter the high 70s to low 80s over the next week. No significant precipitation is predicted, and potential evapotranspiration is expected to be high, so wet fields should dry out quickly and allow for fieldwork.
Crops and pests
Soybean and corn started to emerge late last week and have continued throughout this week. Check fields for damage from early-season pests such as seedcorn maggot (especially if fields were planted into decaying residues and/or tillage around April 18), black cutworm, grubs (especially along sandy ridges) and slugs (in no-till and/or high residue systems). Seedcorn maggot damage will look like burning and scarring on seeds and seedlings. Black cutworm larvae and grubs at this stage will completely cut through seedlings and stems. Slugs are just starting to become active and will eat cotyledons and seeds in the furrow if they can enter it. Planting, tillage and herbicide applications continued as conditions allowed over the past week.
Bucket traps in Berrien (near Berrien Springs), St. Joseph (Centreville) and Van Buren (Lawrence) counties have caught the following:
True armyworm
|
Date |
Berrien |
St. Joseph |
Van Buren |
|---|---|---|---|
|
4/14 |
0 |
0 |
2 |
|
4/21 |
0 |
6 |
0 |
|
4/28 |
0 |
1 |
0 |
|
5/5 |
0 |
2 |
0 |
Black cutworm
|
Date |
Berrien |
St. Joseph |
Van Buren |
|---|---|---|---|
|
4/14 |
0 |
0 |
0 |
|
4/21 |
7 |
15 |
0 |
|
4/28 |
5 |
8 |
0 |
|
5/5 |
11 |
19 |
1 |
Winter wheat is at late Feekes 8 (flag leaf starting to emerge) and into Feekes 9 (flag leaf ligule visible). Flag leaf fungicide applications went out late last week and throughout this week on some acres. The flag leaf contributes heavily to yield, so it is important to keep it free of disease and defoliation. Powdery mildew and low levels of septoria continue in the canopy, and in some cases, the diseases are creeping up the stem and affecting upper leaves. Aphid pressure increased this week.
Potato planting continued this week for some growers, and preemergence herbicide application has been as frequent as field conditions allow. With potato emergence imminent, the window for application (especially to earlier-planted acres) is shrinking.
Some alfalfa weevil insecticide applications went out on alfalfa in the past week. As alfalfa weevil populations build, wait as long as possible to spray, and cut early if reasonable to preserve natural enemies, which provide free season-long insect control. Although the damage looks bad, wait to spray for alfalfa weevil until the crop has met the following conditions: If the alfalfa is about 12 inches tall with larvae in sweeps, 75% or more of stem tips have feeding damage, and there is an average of two larvae per stem, an insecticide application is recommended. If alfalfa is about 16 inches tall, about 100% of stem tips have feeding damage, and there are four or more larvae per stem, harvest early.
For more information, refer to the Michigan State University Extension article “Weevils are popping in alfalfa fields.” If you are in southwest Michigan and feel uncertain about the time and/or procedure for scouting alfalfa weevil, contact Nicolle Ritchie at 269-858-8739 or ritchi67@msu.edu for in-field help rather than spraying too early or unnecessarily.
Irrigation update and crop water use
Early-season crop water use for both corn and soybeans remains relatively low across all three regions. During the emergence stages, weekly water demand is minimal, with most areas reporting potential evapotranspiration rates below 0.4 inches per week. In many cases, existing soil moisture and recent rainfall may be sufficient to support early crop development without irrigation.
Wheat, on the other hand, is currently at peak water use, requiring more than 1.1 inches of water per week. As temperatures and evapotranspiration begin to rise, it’s essential to carefully assess whether irrigation is needed.
It’s important to continue monitoring local weather and soil conditions to adjust your irrigation strategy as the season progresses. Tools like Irrigation Scheduling Tools, can help estimate crop water needs and decide timing and application.
Estimated weekly crop water use for field crops in Michigan (inches/week) for the week of May 5-11, 2025
|
Crop |
Growth stage |
Constantine |
Entrican |
Hart |
|---|---|---|---|---|
|
Corn |
VE |
0.10 |
0.10 |
0.11 |
|
V2 |
0.20 |
0.20 |
0.22 |
|
|
Soybeans |
VC Cotyledon |
0.20 |
0.20 |
0.22 |
|
V1 1st Node |
0.31 |
0.30 |
0.33 |
|
|
Wheat |
Leaf Elongation |
0.92 |
0.90 |
1.01 |
|
Jointing |
1.05 |
1.03 |
1.16 |
|
|
Boot/heading/flowering/grain fill |
1.12 |
1.10 |
1.23 |
The table above presents estimated crop water use for various field crops across three locations in Michigan. This data helps irrigation management decisions by showcasing potential crop evapotranspiration, calculated based on reference evapotranspiration and crop coefficients for each crop growth stage. It is crucial to note that crop water use values vary across regions due to differences in weather conditions, growth stages, agronomic practices and soil properties.
When using these values for irrigation scheduling, be mindful that they assume all applied irrigation water will be utilized by the plants without any loss. Additionally, these values do not account for any precipitation that may occur during the week of calculation.
Reference evapotranspiration data was obtained from Michigan State University Enviroweather, which also offers a model for determining potential crop evapotranspiration. To access this tool, visit Enviroweather, click on "Crops," select your crop and use the potential evapotranspiration tool by choosing your nearest weather station, the latest date of interest and other crop information.
Field Crops Virtual Breakfast Series
Disease management in wheat, presented by Marty Chilvers, was the topic for the MSU Extension Field Crops Virtual Breakfast this week. Powdery mildew and wheat streak mosaic virus have been present in the state. Stripe rust hit Michigan hard last year right around flag leaf emergence, but it is not present in the state so far this year.
Recordings of this and all the Virtual Breakfast meetings are closed-captioned and available at the Field Crops Virtual Breakfast webpage and the MSU Extension Field Crops Team social media platforms: Facebook, Spotify, YouTube, Apple Podcasts and Twitter/X.
