Southwest Michigan field crops update – July 23, 2026
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EmailMost soybeans are in pod formation, and many corn acres have tassels and silks out.
Weather
Smoke from wildfires in Canada blanketed Michigan late last week, reducing solar radiation in the southwest part of the state by about 25%. Rain leading into the weekend helped clear some of the smoke away and brought cooler temperatures that have felt a little like fall. The forecast shows that temperatures will increase slightly this week, although nights will remain fairly cool. Scattered showers early next week are not expected to provide significant precipitation, and the rest of the week will be dry and partly cloudy.
Crops and pests
Most soybeans are in early pod stages, with some early beans starting into seed development. Fungicide applications to prevent white mold should be applied between R1 and R3. The Crop Protection Network’s Crop Risk Tool showed high risk of white mold development on irrigated soybeans and low on non-irrigated soybeans in southwest Michigan for the past week.
Corn stages vary throughout the region from late vegetative stages to full pollination. Seed corn detasseling continued. As corn enters reproductive stages, scout for tar spot by looking for small dark lesions on leaves. Make sure to add water and try to rub the lesion off. If it can be rubbed off, it is not tar spot, but insect droppings. Tar spot fungicides are most profitable when applied between R1 (silking) and R3 (milky kernel) in corn. Beyond last week’s confirmations of tar spot in Calhoun and Jackson Counties, no Southwest Michigan counties have confirmed tar spot this week, according to the Tar Spot Map. The Crop Risk Tool showed low risk for tar spot development over the past week. Cooler temperatures and irrigation increase tar spot risk.
Watch for western bean cutworm (WBC) in fields that are close to tasseling or freshly tasseled. WBC traps near Union City and Lawrence had a high moth count this past week. Put the sun behind the leaves to watch for egg masses, which will appear as dark shadows on the backlit leaves. The threshold for WBC treatment is 5% of plants affected (cumulative week after week).
WBC adult moth counts spiked in Branch and Van Buren Counties this week. Bucket traps in Berrien (Eau Claire), Branch (Union City), St. Joseph (Centreville and Sturgis) and Van Buren (Lawrence) Counties have caught the following:
|
Date |
Branch 1 |
Branch 2 |
Centreville |
Eau Claire |
Lawrence |
Sturgis |
|
7/6 |
-- |
-- |
106 |
35 |
117 |
61 |
|
7/13 |
85 |
76 |
33 |
50 |
45 |
41 |
|
7/20 |
109 |
9 |
14 |
41 |
93 |
21 |
Winter wheat harvest and straw baling continued over the past week and are nearly finished. Cover crops or soybeans have been seeded following wheat on some acres.
Potatoes are in tuber bulking stages. Vine kill began this week on early crop Russets, which will be harvested in a few weeks. In full-season and storage potatoes, scout for aphids by checking the undersides of lower leaves, and scout for late blight along field edges and moist spots. Late blight risk over the past week was moderate to low, according to the Vegetable Disease and Insect Forecasting Network. Vine rot is a constant battle during July, but recent cooler temperatures should help slow it down a little.
Alfalfa and forage cutting and baling continued over the past week.
Irrigation and water use
Corn has reached the peak crop water stages. Corn at VT (tasseling) and silking is using approximately 1.4 inches of water per week. The period from one week before tasseling through three weeks after is the most critical for water, and stress during this time can significantly reduce yield.
Soybeans are also at peak water demand, requiring approximately 1.3–1.4 inches of water per week. The most critical stages for avoiding water stress are R3–R4 (pod development) and R5–R6 (seed fill).
Potatoes in the tuber bulking stage continue to have high water demand, requiring approximately 1.2 inches of water per week
Irrigation demand will continue to remain high as crops reach peak water use stages. Watch for visible signs of water stress, such as leaf rolling in corn and flipped leaves in soybeans during the early morning or evening, as these may indicate inadequate soil moisture.
To improve irrigation management, consider using irrigation scheduling tools such as the free and updated MSU Irrigation Scheduling Mobile App, available for Apple and Android devices. The app provides field-specific irrigation recommendations based on crop growth, weather, and soil type.
Weekly crop water use updates will continue to be shared through the Southwest Michigan Crop Updates. For added convenience, updates will also be sent through direct email and text messages. Sign up here. If you would like to see an additional location included in the report, please contact Angie Gradiz at gradizme@msu.edu or 531-249-4956.
The following table summarizes estimated crop water use (inches per week) for major irrigated field crops across Michigan's primary irrigated regions.
Estimated weekly crop water use for field crops in Michigan (inches/week) for the week of July 13-19, 2026:
| Crop | Growth stage | Constantine | Berrien Springs | Entrican | Hart |
|---|---|---|---|---|---|
| Reference ET | 1.31 | 1.29 | 1.31 | 1.30 | |
| Corn | V12 | 1.00 | 0.98 | 1.00 | 0.99 |
| Corn | V14 | 1.31 | 1.29 | 1.31 | 1.30 |
| Corn | VT and Silk | 1.44 | 1.42 | 1.44 | 1.43 |
| Soybeans | V4-V5 | 1.31 | 1.29 | 1.31 | 1.30 |
| Soybeans | R1 | 1.44 | 1.42 | 1.44 | 1.43 |
| Soybeans | R2 and R3 | 1.44 | 1.42 | 1.44 | 1.43 |
| Potato | Tuberization | 1.31 | 1.29 | 1.31 | 1.30 |
| Potato | Blossom | 1.31 | 1.29 | 1.31 | 1.30 |
| Potato | Tuber bulk | 1.19 | 1.17 | 1.19 | 1.18 |
Field Crops Virtual Breakfast Series
No Pipe, No Trench: Do Mole Drains Fix Wet Soils? presented by Ehsan Ghane, was the topic for the MSU Extension Field Crops Virtual Breakfast this week. Mole drains leave cracks in the soil leading to a subsoil channel where water can drain. They work best in fields with high clay and low sand contents.
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, Mediaspace, 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.
