Crop Diagnostic Training Center Summer Workshops

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University of Wisconsin’s Crop Diagnostic Training Center will be hosting two hands-on workshops this summer: Diagnostic Troubleshooting July 30 and Crop and Pest Management on August 13. For more information, please download the workshop flyer. Registration is available online.

Post-emergence herbicides for corn and soybean

At this time of the year, integrated weed management programs focus on scouting and diversifying management practices including non-chemical methods and herbicide sites-of-action. For more information, please visit the United Soybean Board’s TakeAction website for field management guidelines and to learn more about herbicide sites of action. Michigan State University’s Weed Science website has detailed web pages on common weeds in annual crops with biological information and management recommendations. After each field season, the Herbicide Evaluation Program here at the university publishes efficacy data in a research report. Summary ratings for many weed species are located in “Pest Management in Wisconsin Field Crops” available as a free pdf or in print at Cooperative Extension’s Learning Store.

Herbicide Injury Diagnosis for Corn Seedlings at Emergence

Depending upon the herbicide, injury can occur after a pre-emergence application when corn is germinating in cool, wet soils. This year, if corn was planted in mid-April then you may observe some injury. However, it is important to remember that other environmental factors can mimic herbicide injury symptoms such as corn emerging in crusted or compacted soil. For this spring, WCWS has a re-designed online diagnostic tool, available at http://wcws.cals.wisc.edu/herbicide-injury-diagnostic-tool or from the main page, go to ‘Resources’ and then to ‘Tools’. The diagnostic tool asks three basic questions 1) When do injury symptoms appear? 2) Are both broadleaves and grasses affected or just one group? and 3) What are the symptoms and where do they occur? The original web-based tool was developed by Tim Trower and Chris Boerboom to accompany a handy two-page guide. The following changes were made to the new version:

  1. Each page shows your previous answers.
  2. A ‘Start over’ button is located at the bottom of each page.
  3. For each herbicide mode-of-action, an herbicide chart from the TakeAction Herbicide Classification poster or on the WCWS website under ‘Resources’, ‘Documents’(Fig. 1).
  4. Simplified guides to symptoms that mimic herbicide injury during and after emergence are included on each mode-of-action page (Fig. 2).
  5. Photo galleries for both corn and soybean injury symptoms are located on the same page (Fig. 3).

Figure 1. Herbicide site-of-action groups, chemical  families, active ingredients, and product examples for the seedling shoot growth inhibitor mode-of-action.  Specific sections of the larger TakeAction chart are on each mode-of-action page.

Figure 1. Herbicide site-of-action groups, chemical families, active ingredients, and product examples for the seedling shoot growth inhibitor mode-of-action. Specific sections of the larger TakeAction chart are on each mode-of-action page.


Figure 2. Mimics of herbicide injury to corn during or at emergence.

Figure 2. Mimics of herbicide injury to corn during or at emergence.


Figure 3. Example of a photo gallery for corn and soybean herbicide injury symptoms.

Figure 3. Example of a photo gallery for corn and soybean herbicide injury symptoms.

For pre-emergence applications in corn, the seedling shoot growth inhibitors, particularly the chloroacetamides, may injure seedlings when soils are cool and wet. Injury will not always be apparent aboveground. For example, corn plants with seedling root growth inhibitor damage will display clubbed root tips and grasses will be more affected than broadleaves. To get an idea of injury risk, check out the herbicide tables in “Pest Management in Wisconsin Field Crops” available in pdf and print formats at Cooperative Extension’s Learning Store.

Scout your fields for weed seedlings this spring

Figure 1. A) Common lambsquarters, Chenopodium album; a soil sampler, one inch diameter, is in the foreground B) Horseweed (marestail), Conyza canadensis; C) Giant ragweed, Ambrosia trifida, with seed capsule attached; D) Giant ragweed seedlings.

Figure 1. A) Common lambsquarters; a soil sampler, one inch diameter, is in the foreground B) Horseweed (marestail); C) Giant ragweed, with seed capsule attached; D) Giant ragweed seedlings.

The fields may look cold, wet, and dormant this week but weeds were germinating in some fields in Janesville and Arlington last week. On April 17 at Janesville, common lambsquarters, giant ragweed, and horseweed were emerging (Fig. 1A-D). At Arlington in a plowed area, velvetleaf was emerging (Fig. 2). If you are leasing new land this year or want to get a head start on weed management, then scouting for weeds at the seedling stage before tillage can be a good way to assess density, the number of weeds in a given area, and for which weed species will likely be an issue around planting time. The Weedometer, developed by University of Wisconsin, can predict when weed species will likely be emerging for your location at http://weedecology.wisc.edu/weedometer/ . A guide to identifying the “Common Weed Seedlings of the North Central States” is available in pdf and print formats at Cooperative Extension’s Learning Store, or on the WCWS Weed info page.

Figure 2. Velvetleaf seedling.

Figure 2. Velvetleaf, Abutilon theophrasti, seedling.

UW Cooperative Extension Cover Crop Workgroup Website

What are the economic costs of cover crops? What are the environmental and economic benefits? How do the nutrients from cover crops cycle through the soil? What is The New York Times saying about cover crops? All of this information and much more can be found on the UW Cooperative Extension Cover Crop Workgroup website, where UWEX personnel across Extension programs and disciplines provide resources regarding cover crops which will be frequently updated.

Yahara Watershed Videos

Wisconsin’s Yahara Watershed encompasses lakes Mendota, Monona, Waubesa, Wingra, and Kegonsa, and also includes the Lakeshore Nature Preserve.The UW-Madison Water Sustainability and Climate project created the Water Walk video series to provide a virtual tour of this beautiful area as well as to show how human activities impact the quality of water in the watershed.

Common ragweed confirmed ALS inhibitor-resistant in Brown County Wisconsin

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Recently, Thomas Butts, a graduate research assistant, Vince Davis, and Dave Stoltenberg confirmed that a common ragweed population in Wisconsin is resistant to an ALS inhibitor. The full report is now available. For more information, please visit the WCWS documents page.