Southwest Michigan field crops update – August 14, 2025
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EmailSoybean pod fill is underway. Some corn has started to dent. Harvest began on tablestock potatoes.
Weather
High temperatures continued over the past week. Precipitation fell earlier this week, ranging from about half an inch to an inch. Although not enough to meet plant evapotranspiration demands, it was still a welcome addition. High temperatures are forecast to continue, with humidity and nighttime temperatures dropping just a little. The next chance for significant precipitation is early next week.
Crops and pests
Soybeans are mostly in early seed fill stages. Most fields have entered R5, which is when the seed of a pod on the fourth node down on the main stem is 1/8-inch long. R5 will typically continue for several weeks. Some early planted soybeans are approaching R6, which is where the seed has filled the pod cavity. Watch for sudden death syndrome, brown stem rot and red crown rot, all of which have similar symptoms. Red crown rot is a disease new to the Midwest, and it has not been confirmed in Michigan yet.
Corn ears continued to develop, which some entering R5 (dent), while others are at R2 (blister). Most acres are somewhere in the middle, with R3 (milk) being when kernels are yellow and filled with milky white liquid and R4 (dough) when kernels are more solid but still with some give. Male row destruction continued in seed corn, and defoliation sprays on some early planted acres are probably not far out.
Tar spot is present in most of the counties in southwest Michigan. The Crop Protection Network tar spot of corn map contains a helpful table for determining if a tar spot fungicide application is beneficial at various crop stages. When scouting, pay special attention to areas of the field that would have prolonged leaf wetness. Also watch for southern rust, which was found this week in Allegan, Ionia, Ingham and Jackson counties. Similar to tar spot, the benefit of applying a fungicide for southern rust decreases as the corn enters R4 and is unlikely by R5.
Western bean cutworm moth flights have been low, with peak flight occurring the week of July 14-21. Corn that is freshly tasseled or close to tasseling is most attractive to western bean cutworm moths. At this point in the season, most fields are out of the window of concern for western bean cutworm.
Bucket traps in Berrien (near Niles), Branch (near Union City), St. Joseph (Centreville and Sturgis) and Van Buren (Paw Paw) counties have caught the following western bean cutworm moths:
|
Date |
Branch 1 |
Branch 2 |
Centreville |
Niles |
Paw Paw |
Sturgis |
|---|---|---|---|---|---|---|
|
8/11 |
-- |
-- |
0 |
0 |
5 |
6 |
Winter wheat harvest wrapped up, and many fields have been planted with cover crops or double-crop soybeans by now. Variety selection and small batch seed treatment for the upcoming crop will start soon if it hasn’t already.
Fresh crop chip potato harvest continued, and tablestock potato harvest started over the past week. Vine kill applications continued, and many fields are struggling to maintain a canopy amidst potato early die, vine rot and heat.
Alfalfa and forages continued at variable stages of growth.
Weekly water use
Crop water use generally decreased this week compared to last week. In many areas, rainfall reduced the need for irrigation; however, in locations where rainfall did not fully meet crop water demands, supplemental irrigation was still necessary.
Corn is entering the dent stage, currently using about 1.27 inches of water per week in southwest Michigan. Water use will begin to decline at full dent, aligning more closely with grass-reference potential evapotranspiration.
Soybeans are in their most sensitive period for water stress between the R3 and R6 stages (from pod development through seed fill) and are also using approximately 1.27 inches of water per week. Monitor for signs of stress or disease pressure and adjust irrigation strategies accordingly.
To help reduce the risk of diseases associated with constant leaf wetness, Michigan State University Extension recommends applying larger volumes of water less frequently rather than frequent small applications. 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 Aug. 11-17.
|
Crop |
Growth stage |
Constantine |
Entrican |
Hart |
|---|---|---|---|---|
|
Corn |
Reference ET |
1.15 |
1.15 |
1.09 |
|
Corn |
V14 |
1.27 |
1.27 |
1.2 |
|
Corn |
VT, Silk, Blister, Dough, Begin Dent |
1.27 |
1.27 |
1.2 |
|
Corn |
Full dent |
1.15 |
1.15 |
1.09 |
|
Soybeans |
R2 Full Bloom |
1.27 |
1.27 |
1.2 |
|
Soybeans |
R3 Begin Pod / R4 Full pod |
1.27 |
1.27 |
1.2 |
|
Soybeans |
R5 Begin seed / Full seed |
1.27 |
1.27 |
1.2 |
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
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Field crop nematode update, presented by Marisol Quintanilla, MSU Extension nematologist, was the topic for the MSU Extension Field Crops Virtual Breakfast this week. Nematodes—and especially soybean cyst nematode—can greatly limit yields and impact plant health.
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.
This work is supported by the Crop Protection and Pest Management Program [grant no 2024-70006-43569] from the USDA National Institute of Food and Agriculture. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture.
