Herbicide injury during and after emergence in soybean

Pre-emergence and post-emergence herbicides can injure soybean plants. This year, soybean injury symptoms following pre-emergence applications have been relatively slight for May 13 and May 19 planting dates. In the herbicide evaluation program, soybean injury symptoms that we typically observe are stunting, drawstring (puckering), chlorosis (yellowing), and necrosis. However, it is important to keep in mind that injury symptoms may be due to weather, soil conditions, or disease.

To diagnose an injury problem at or during emergence, first check the root system of the plant. Seedling root growth inhibitors, ALS inhibitors, and growth regulators change the root architecture in different ways. Next step, if the roots appear normal, take a look at the leaves for yellowing (chlorosis), bleaching, or drawstring (puckering). To help with diagnosis, University of Wisconsin Extension has a two-page guide, available for download and an online diagnostic tool.

After emergence, PPO inhibitor injury tends to appear on the leaves that receive the application but younger leaves will not show any injury symptoms. Typical damage includes yellowing (chlorosis) and browning of the leaf surface in spots (necrosis) (Fig. 1A). Researchers at Purdue University have a five minute video discussing PPO inhibitor and fluopyram (ILeVO) seed treatment injury.

It is important to remember that despite the damage, in most cases yield is not affected. Also, PPO inhibitors add another site of action to your resistance management plan and effectively control a variety of broadleaf weed species. Growth regulators cause leaf cupping or epinasty (downward growth habit) (Fig. 1B). The leaves of soybean plants with ALS inhibitor injury show chlorosis and distinctive reddish leaf veins (Fig. 1C).

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Injury symptoms typically appear seven to fourteen days after application and will gradually decrease through the season when the plants resume normal growth. Phytotoxicity data are available in the WCWS research reports. Each trial contains a summary section that will mention if any phytotoxicity symptons were observed. If the injury differed by treatment and exceeded five percent then a bar graph is included. Crop injury resulting from an application made according to the label instructions usually does not cause a reduction in yield. “Pest Management in Wisconsin Field Crops” shows the relative risk of soybean injury from different herbicides on pages 143 and 144, available 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.

UWEX Crop Budget Analyzer

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Ken Williams, an Extension agent in Waushara county has released an updated Crop Budget Analyzer for corn, soybeans, wheat, seeding alfalfa, and established alfalfa. The Budget Analyzer is a downloadable Excel spreadsheet, which can generate handy one page print-outs.

Other UWEX and USDA resources are available to help with pricing and budgeting.

More Winter Reading, the 2014 WCWS Research Report

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Yep, it is that time of year. Winter is setting in and the 2014 WCWS Research Report is here to chase away the winter blues. Print copies will be distributed at the Pest Management Update meetings and at the Wisconsin Crop Management conference. Check out our Documents page again in December for an updated report with yield data.

App for Pricing Wet Corn

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UW-Extension has a smartphone app for pricing high moisture corn. For more information, keep reading the following the press release from UW-Extension’s Greg Blonde.

Contact: Greg Blonde, UW-Extension Waupaca County, 715-258-6230, greg.blonde@ces.uwex.edu

Pricing Wet Corn? UW-Extension has an app for that

Waupaca, Wis. – It’s that time of the year when Wisconsin dairy and beef producers and Wisconsin corn growers explore their options of buying or selling high moisture shell corn (HMSC). This is especially true this year in the northern two-thirds of the state with so much wet corn still in the field.

To help farmers better evaluate their options, the University of Wisconsin-Extension released a Smartphone app this fall to provide a simple way to help estimate the market value of HMSC based on three main variables – dry corn moisture, current corn moisture and price per bushel.

The HMSC$ app is free and available for Android smart phones and tablets on the Google Play store by searching for “HMSC”.

Farmers can use this app to help determine an equivalent value for wet shell corn when compared with a dry shell corn price – a link to current local elevator dry corn bid prices is built into the app. The equivalent wet price is then calculated and displayed in both price per ton and price per bushel. Additional costs for drying and/or shelling can be evaluated under the expense tab. The app also features the ability to email the results directly to others.

“Although a desktop Excel spreadsheet for pricing HMSC is available on the Wisconsin Center for Dairy Profitability web site, it doesn’t have the ability to bring up current market information or automatically share the results”, said Greg Blonde, UW-Extension Waupaca County agriculture agent. “When you’re out in the field or on the go, the HMSC$ app is a great resource tool to have on your Smartphone or tablet computer.”

Blonde also noted the app may be useful to grain elevator managers, as well as Ag lenders and farm managers for valuing their grain or feed inventories.

In the toolbox: Invasive Plant Control Database

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The Midwest Invasive Plant Network has published an online search tool to find information on invasive species control- Invasive Plant Control Database. From this website, go to Resources and then to Tools. The MIPN database works best if you already know the invasive plant species that you have. To help with identification, the Herbarium at the University of Wisconsin-Green Bay has a very nice image catalog of invasive species in Wisconsin, including the counties where they have been found and species descriptions. Another great resource that categorizes the invasive species by habitat is hosted by Wisconsin’s Department of Natural Resources.

Still unsure of the plant species, try University of Wisconsin’s weed identification tool or go to the PlantDOC website to find your local Extension agent and submit a digital image for identification. The Extension Specialist for Invasive Plants at UW-Madison is Mark Renz and his contact information is here.

Learning from your living room

The University of Wisconsin and UW-Extension produce a wide array of educational videos. Most of these videos are posted on various YouTube channels.

In the toolbox: the Weedometer

The Weedometer is a tool built by Ed Luschei, a former Department of Agronomy faculty member, using data collected from the Weed Garden at the Arlington Research Station from 1998 until 2001. The Weedometer will chart emergence and flowering times for a wide array of weed species at many locations throughout the United States.

The Weedometer website has detailed instructions for using the tools. The following diagrams provide abbreviated instructions for how to use the Weedometer. Click on the image to make it larger.

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