Don’t Forget about Marestail

The harsh realities of poor marestail control with burndown herbicides applied before soybean planting were widespread during the 2013 growing season.  We anticipated even more challenges with this species for the 2014 growing season, but by and large the forecasted marestail “train wreck” did not materialize in much of the state.  Fall herbicide applications coupled with a harsh winter that caused a high degree of mortality to winter annual weed species probably contributed to a reduced population of marestail last spring.  However, it is unwise to assume that a lower marestail population last year will translate into a low marestail population this year.

It’s not too early to apply herbicides to control emerged marestail in fields that will be planted to soybean.  The small marestail plants we have currently will be much easier to control than the larger plants that will be encountered in several weeks.  Consider an early herbicide application targeted for marestail control, and application of soil-residual herbicides for summer annual weeds closer to soybean planting.  Dr. Mark Loux, extension weed scientist at The Ohio State University, recently published suggestions to improve marestail control with burndown herbicides; you can read these suggestions at


Decisions About Winter Wheat and Weeds

The most recent report on the condition of the Illinois winter wheat crop indicated approximately 10% of the crop was rated poor or very poor, while close to 90% was rated fair to excellent.  It appears likely that much of the wheat crop will remain intact, but in other instances farmers might elect to terminate poorer stands and plant corn or soybean.  If the decision is made to plant corn or soybean into wheat stands where some plants remain alive, it is advisable to control any remaining wheat plants prior to planting either corn or soybean.  Controlling existing wheat stands may be accomplished through the use of tillage, herbicides, or a combination of these.

If the wheat field was previously treated with a herbicide, be sure to check for any applicable crop rotational intervals.  These could determine whether or not corn or soybean could be planted.  If a combination of herbicides and tillage will be used to terminate an existing stand, improved control might be achieved if the herbicide application occurs prior to the tillage operation, compared with the opposite order.  Regardless of what herbicide you use to control wheat plants, there should be an interval of at least 3 to 5 days (or more) between application and tillage to allow the herbicide to work within the plant.

It is altogether possible that other weed species, such as maturing winter annuals, early summer annuals, biennials, or perennials, also might be present in existing wheat fields.  If so, select a herbicide or herbicide combination that will provide broad-spectrum control of both grass and broadleaf weed species.  If 2,4-D is included in the tankmix, be cognizant of the intervals that must elapse between application and planting (especially for soybean, but also for corn with some formulations).

Several herbicides could be used to control existing wheat plants.  Glyphosate is very effective on grasses, including wheat.  The label suggests using 0.56 lb ae to control overwintered wheat up to 6 inches tall, 0.77 lb ae to control wheat up to 12 inches tall, and 1.125 lb ae for wheat up to 18 inches tall.  Gramoxone SL is a rapidly-acting contact herbicide.  Efficacy on wheat can be improved when atrazine or metribuzin is tankmixed with Gramoxone SL.  A crop oil concentrate or nonionic surfactant should be included, and thorough spray coverage is essential for good control.  The labels of the ACCase-inhibiting herbicides (Poast, Assure II, Select Max, Fusilade DX, and Fusion) indicate these products are effective against volunteer wheat.  However, each product label also indicates a specific rotational interval between application and planting corn.  Poast is labeled for preplant applications, but applications must be made at least 30 days before planting corn.  The labels of Select Max, Fusion, Fusilade DX, and Assure II indicate rotational intervals of 30, 60, 60, and 120 days, respectively, between application and planting corn.

Herbicide applications to control weeds in wheat must be properly timed to provide good weed control and minimize the potential for crop injury.  Applications made to actively growing weeds and during periods of warm air temperatures generally provide more effective and complete weed control as compared with applications made during cold, cloudy conditions.

The labels of all herbicides commonly used for weed control in Illinois wheat have application restrictions based on wheat developmental stage.  The labels of most herbicides commonly used in Illinois indicate applications must be made before the wheat jointing or boot stage.  Figure 1 contains information derived from the herbicides labeled for use in small grains.  Before making any herbicide application, consult the respective herbicide label for additional information.

If you are considering applying a herbicide with liquid nitrogen as the carrier, be sure to consult the herbicide label prior to making this type of application.  Not all herbicides allow applications with liquid nitrogen as the carrier, and those that do allow this might have specific recommendations with respect to including/excluding other spray additives or their application rates.

Figure 1. Wheat growth stages and herbicide application (from 2015 Weed Control Guide for Ohio, Indiana and Illinois).

Spring Cover Crop Field Day March 26th – Ewing Demonstration Center

Join us on Thursday, March 26th, 2015 for the  Spring Cover Crop Field Day at the University of Illinois Extension Ewing Demonstration Center.  Registration will start at 8:30 a.m. and the program will begin at 9:00 a.m., rain or shine.  The Ewing Demonstration Center is located at 16132 N. Ewing Rd; Ewing, IL 62836, on the north edge of the village of Ewing, north of the Ewing Grade School on north Ewing Road.  Watch for signs.

Cover crops have many benefits to the soil, environment, and overall crop production and management.  Topics covered during this field day program include:

Challenges of Grazing Lush Spring Forage

–          Travis Meteer, Extension Educator, U of I Extension

Techniques for Planting into Cover Crop Residue

–          Mike Plumer, Private Consultant

Understanding the Soil Profile Beneath Your Feet

–          Bryan Fitch, Resource Soil Scientist, NRCS

Which One to Choose? Cover Crop Species Selection and Demonstration Trial Tour

–          Nathan Johanning, Extension Educator, U of I Extension

Some of the program highlights will be the demonstration trial planting of cover crops, including 17 different cover crops and combinations illustrating first hand the characteristics of the cover crops and what benefits they bring to your soil and crop production system.  Also, (weather and soil conditions permitting) we will have a soil pit dug, exposing the soil profile, where NRCS Resource Soil Scientist, Bryan Fitch will lead us through the characteristics of our southern Illinois soils to enhance understanding of the importance of a healthy soil.  Also Certified Crop Advisor CEU credits will be available (2.0 Soil & Water Management & 1.0 Crop Management) for the program.

This field day will be free and open to anyone interested in learning more about cover crops.  A light lunch will be provided and this is a great way to talk to fellow growers to learn more from their challenges and successes incorporating cover crops into their cropping systems.  Please call the Franklin County Extension Office at 618-439-3178 for more information and to register by March 24th.  We hope to see you there!

2015 Weed Control Guide Now Available

The 2008 edition of the Illinois Agricultural Pest Management Handbook was the final edition of a publication that served pest management practitioners for many decades. Herbicide information and annual updates of product performance ratings were mainstays of that publication.  Since 2008 we periodically have published herbicide performance ratings, but admittingly not with a great deal of consistency.  Recently, the weed science programs at The Ohio State University and Purdue University extended an invitation to the University of Illinois weed science program to join them in the production of their joint weed control publication.  The 2015 Weed Control Guide for Ohio, Indiana and Illinois contains 212 pages of weed management information, including weed response ratings for corn and soybean herbicides.  Information and recommendations for managing weeds in small grains and forages is included, along with more specific information about and control recommendations for several problem weed species.  A pdf of the 2015 Weed Control Guide is available to download, and a printed version of the guide can be ordered at:



Ewing Demonstration Center Fall Cover Crop Field Day – Nov. 6th

Join us on Thursday, November 6th, 2014 for the the Ewing Demonstration Center Fall Cover Crop Field Day.  Registration and refreshments will start at 8:30 a.m. and the program will start at 9:00 a.m., rain or shine.  The Ewing Demonstration Center is located at 16132 N. Ewing Rd; Ewing IL 62836, on the north edge of the village of Ewing, north of the Ewing Grade School on north Ewing Road.  Watch for signs.

Cover crops have many benefits to the soil, environment, and overall crop production and management.  Topics included in this field day program are:

Establishment Challenges and Successes

– Robert Bellm, Extension Educator, University of Illinois Extension

Calibrating Success:  Drill and Planting Calibration

– Marc Lamczyk, Program Coordinator, University of Illinois Extension

Which One to Choose? Cover Crop Species Selection and Demonstration Trial Tour

– Nathan Johanning, Extension Educator, University of Illinois Extension

In addition, we also have a demonstration planting of cover crops established late this summer so you can view the growth and characteristics of the cover crops first hand and learn more what benefits they bring to your soil and crop production system.

This field day will be free and open to anyone interested in learning more about cover crops.  Please call the Franklin County Extension Office at 618-439-3178 for more information and to register.  We hope to see you there!

Fall-Applied Herbicides: Which Weed Species Should be the Target?

Herbicides applied in the fall often can provide improved control of many winter annual weed species compared with similar applications made in the spring.  Marestail is one example of a weed species that is often better controlled with herbicides applied in the fall compared with the spring.  An increasing frequency of marestail populations in Illinois are resistant to glyphosate, and within the past year we have confirmed that resistance to ALS-inhibiting herbicides also is present in Illinois populations.  Targeting emerged marestail with higher application rates of products such as 2,4-D in the fall almost always results in better control at planting compared with targeting overwintered and often larger plants with lower rates of 2,4-D in the spring.

One question typically posed is whether or not a fall application needs to include one or more herbicides that provide residual control of winter annual weed species.  Typically, the earlier the fall application is made (say, early October) the more benefit a soil-residual herbicide can provide since emergence of winter annual weeds is often not complete.  However, delaying the herbicide application until later in the fall (say, mid-November) often diminishes the necessity of a soil-residual herbicide since most of the winter annual weeds have emerged and can be controlled with non-residual herbicides.  Applying a soil-residual herbicide late in the fall in hopes of having a clean field prior to planting is akin to gambling on the weather.  Cold winter conditions (similar to last winter) can reduce herbicide degradation in the soil and increase herbicide persistence.  This might not always be favorable since, depending on the residual herbicide, increased persistence also can cause injury to the following crop.  A more moderate winter and early spring warming will increase herbicide degradation, which could result in the need for a burndown herbicide to control existing vegetation before planting.

We recommend fall-applied herbicides target fall-emerging winter annual species, biennials, and perennials.  We do not recommend fall application of residual herbicides for control of any spring-emerging annual weed species.  We are aware that some products have 2(ee) recommendations that suggest the product will control certain summer annual weed species following application in the fall.  Particularly concerning to us is that “pigweed species” are listed on at least one product label.  The extension weed science program at the University of Illinois does not recommend fall-application of residual herbicides to control Amaranthus species the next spring for the following reasons:

1)      Inconsistent performance: as previously described, the performance consistency of soil-residual herbicides applied in the fall is greatly dependent on weather and soil conditions after application.  Our data suggest the greatest and most consistent control of Amaranthus species either at planting or several weeks after planting was achieved when residual herbicides were applied in the spring, not in the fall.

2)      Increased selection for herbicide-resistant biotypes: soil-applied herbicides are not immune from selection for herbicide-resistant biotypes (please see the April 16, 2013 article titled: “Herbicide Resistance: Are Soil-Applied Herbicides Immune?”).  Following a fall application, the concentration of herbicide remaining in the spring when Amaranthus species begin to germinate will be much lower compared with the same product rate applied closer to planting.

Populations of several of the most challenging summer annual broadleaf weed species in Illinois demonstrate resistance to herbicides from more than one site-of-action herbicide class.  Their effective management requires an integrated approach that often includes soil-residual herbicides.  Applying these herbicides when they will be most effective against these challenging summer annual species is a critical component of an integrated management program.

Remain Vigilant for Palmer Amaranth

Accurate identification of weedy Amaranthus species during early vegetative stages can be difficult.  However, identification of the various species becomes much more reliable when reproductive structures are present (Figure 1).

Figure 1. Inflorescences of five Amaranthus species.

Before harvest begins, consider taking a few minutes to scout fields; at this time of year it is much easier to differentiate between Palmer amaranth (Figure 2) and waterhemp plants (Figure 3).

Figure 2. Mature Palmer amaranth in soybean.

Figure 3. Mature waterhemp in soybean.

Similar to waterhemp, Palmer amaranth plants are either male or female; male plants produce only pollen while female plants produce only seed.  Most seeds on female plants already have attained their mature black color, although some seeds may still be dark brown.  The terminal inflorescence of male and female Palmer amaranth plants is generally unbranched and very long (Figure 4).

Figure 4. Palmer amaranth inflorescences.

The terminal inflorescence of female Palmer amaranth plants (Figure 5) have flowers containing 5 spatulate-shaped tepals.  The tepals are about twice the length of the seed, and the seed capsule (utricle) breaks into 2 regular sections when fractured.  Modified leaves (bracts) of the female inflorescence are long and become very pointed and stiff as the plant matures (Figure 6).

Figure 5. Inflorescence of a female Palmer amaranth, measured in feet.

Figure 6. Stiff, pointed bracts of a female Palmer amaranth.

This characteristic can also aid in differentiating between female Palmer amaranth and waterhemp plants; the inflorescence of a mature female Palmer amaranth plant feels very sharp and prickly while the inflorescence of a mature female waterhemp plant is soft to the touch.

As a reminder, through finding provided by the Illinois Soybean Association we are able to screen samples of suspected Palmer amaranth using molecular markers to verify the species identification.  Information on how to collect and submit tissue samples from suspected Palmer amaranth plants can be found in the “Palmer Amaranth Identification” form that accompanies this article.  Please download this form, provide as much information as possible, and submit it along with the tissue samples to the address listed at the top of the form.

Palmer Amaranth ID Form


2014 Ewing Demonstration Center Fall Field Day

2014 Ewing Demonstration Center Fall Field Day

The University of Illinois Extension will host its annual Ewing Demonstration Center Fall Field Day on Thursday, September 11, 2014 at 9 a.m.  The Ewing Demonstration Center at is located at 16132 N. Ewing Rd; Ewing IL 62836, on the north edge of the village of Ewing, north of the Ewing Grade School on north Ewing Road.  Watch for signs.

The ongoing research plots this year consist of a soybean cover crops trial, LibertyLink soybean variety trial, insecticide/fungicide trial on soybeans, corn population study, drought tolerant corn hybrid evaluation, and new this year a pumpkin variety trial.


The topics to be discussed at Field Day include:

Fusarium Head Blight (Scab) and Vomitoxin Management in Wheat

  • Carl Bradley, Extension Specialist, Plant Pathology, University of Illinois Extension

Sky High Crop Scouting; Unmanned Aerial Drones

  • Dennis Bowman, Extension Educator, University of Illinois Extension

Alternative Forages and Harvesting Methods

  • Teresa Steckler, Extension Educator, Commercial Ag, University of Illinois Extension

Palmer Amaranth: Coming (Soon) to a Field Near You

  • Robert Bellm, Extension Educator, Commercial Ag, University of Illinois Extension

Cover Crops and Weed Management

  • Nathan Johanning, Extension Educator, Small Farms Local Foods, University of Illinois Extension

Refreshments will be provided by Franklin County Farm Bureau.

The field day is free and open to anyone interested.  A light lunch will be provided and registration is recommended by September 8, 2014 for an accurate meal count.

For additional information or to register, contact Marc Lamczyk at University of Illinois Extension Office in Franklin County at 618-439-3178 or


Reminder of the Palmer amaranth Field Research Tour

The weed science program at the University of Illinois would like to take the opportunity to remind everyone of the Palmer amaranth field research tour scheduled to begin at 9:00 a.m. on July 30.  The tour will feature presentations about Palmer amaranth identification, biology, and management and provide participants the opportunity to view several field experiments conducted by the University of Illinois and scientists from Bayer CropScience.  Advanced registration can be accomplished by visiting  Everyone is welcome and there is no fee to attend this tour.  Credits for certified crop advisers will be available.  Additional information and directions to the field research location can be viewed at:

Fomesafen Rotational Crop Intervals

Nearly all herbicide labels (soil-applied or postemergence) have rotational crop intervals that specify the amount of time that must elapse between herbicide application and planting a rotational crop.  Adhering to these intervals is always important, but becomes particularly important with late-season herbicide applications or when soil moisture is limited.  These intervals are established to reduce the likelihood that herbicide residues will persist in sufficient quantities to adversely affect the rotational crop.  Some herbicide rotational restrictions are based solely on time, while other factors, such as soil pH and the amount of precipitation received after herbicide application, can influence the length of the crop rotational intervals.

Soil moisture is often the most critical factor governing the efficacy and persistence of soil-residual herbicides.  Many herbicides are degraded in soil by the activity of soil microorganisms, and populations of these microorganisms can be greatly depressed when soil moisture is limited.  Additionally, dry soils can enhance herbicide adsorption to soil colloids, thus rendering the herbicide unavailable for plant uptake and degradation by soil microbial populations.  Some herbicide rotational intervals are increased if a specified amount of precipitation is not received by a certain calendar date.

Diphenylether herbicides (Flexstar, Cobra and Ultra Blazer, for example) are routinely applied to soybean for control of waterhemp.  In non-GMO and glyphosate-resistant soybean varieties these herbicide active ingredients can provide good to excellent control of small, susceptible waterhemp, but control is often poor when waterhemp plants exceed 5–6 inches or are resistant to PPO-inhibiting herbicides.

Fomesafen has the longest soil residual activity among the three foliar-applied diphenylether herbicides.  Soil half-life values (the time required for half of the applied herbicide to degrade) for fomesafen have been reported to range from100 days to 6 to 12 months.  The range is dependent upon several factors, including soil type and soil moisture.  For example, the soil half-life of fomesafen under anerobic conditions (flooded soil) is only 3 weeks, but persistence is extended as soil moisture becomes more limited.  Labels of fomesafen-containing products (Table 1) specify 10 months must elapse between application and planting corn.  Applying a fomesafen-containing product at this time of the 2014 growing season would preclude planting corn before May 2015.

Table 1.  Fomesafen-containing products labeled in Illinois.


Battle Star

Battle Star GT


Cheetah Max



Flexstar GT









Shafen Star



Top Gun