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: http://estore.osu-extension.org/productdetails.cfm?PC=2860



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 lamczyk@illinois.edu.


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 bayerrespecttherotation.com.  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




Palmer amaranth Field Research Tour July 30

The University of Illinois weed science program would like to extend an open invitation to join us on July 30, 2014 for a field tour and discussions at our Palmer amaranth research site, located approximately ½ mile east of the intersection of county roads 14000 west and 3000 north (see Google map following this article) near the community of Union Hill.  The tour will provide an excellent opportunity for farmers, input suppliers, members of the media, etc. to have a first-hand encounter with a Palmer amaranth population thriving just a few miles south of Illinois’ largest city.  The tour will feature four presentations by weed scientists that highlight the identification, biology, and management of Palmer amaranth, and also provide ample opportunity to view the numerous research plots.  Participants will receive a complimentary tour booklet that contains field research protocols and maps that will help guide them through the research plots.  The tour will begin at 9:00 a.m. and conclude with a catered lunch around noon.  Advanced registration can be accomplished by visiting bayerrespecttherotation.com.  Everyone is welcome and there is no fee to attend this tour.  Credits for certified crop advisers will be available.

Figure 1.  Photographs taken at the Palmer amaranth location the day of planting (left) and six weeks after planting (right).


A brief synopsis of the four tour presentations follows:

Dr. Larry Steckel, extension weed scientist at the University of Tennessee, will provide tips on Palmer amaranth identification and also share his vast experience in managing this invasive and extremely competitive weed species in Tennessee

Dr. Pat Tranel, professor of molecular weed science at the University of Illinois, will discuss the current status of herbicide resistance among waterhemp and Palmer amaranth populations in Illinois, and also offer insights into how to best employ future technologies to manage these dioecious pigweeds

Dr. Aaron Hager, extension weed scientist at the University of Illinois, will discuss recommendations to manage Palmer amaranth in Illinois agronomic crops, including how to best utilize soil-residual herbicides in combination with intense crop scouting, timely applications of foliar-applied herbicides, and other mechanical and cultural methods

A representative of Bayer CropScience will provide an update on new Bayer traits and technologies under development to help manage Palmer amaranth and other troublesome weeds


Our Palmer amaranth field research activities and tour are in collaboration with scientists and researchers from Bayer CropScience.  We thank Bayer CropScience and all our research partners for providing the research support necessary to better understand and manage Palmer amaranth in Illinois.

Screening Waterhemp for Herbicide Resistance

Herbicide-resistant waterhemp populations continue to expand into more areas of Illinois each season.  Waterhemp has evolved resistance to herbicides encompassing more mechanisms of action than any other Illinois weed species, including resistance to inhibitors of acetolactate synthase (ALS), photosystem II (PSII), protoporphyrinogen oxidase (PPO), enolpyruvyl shikimate-3-phosphate synthase (EPSPS) and hydroxyphenyl pyruvate dioxygenase (HPPD).  Not every individual waterhemp plant is resistant to one or more herbicides, but the majority of field-level waterhemp populations contain one or more types of herbicide resistance.  Perhaps even more daunting is the occurrence of multiple herbicide resistances within individual plants and/or fields.

Since 2010, the Illinois Soybean Association has provided funding to screen waterhemp samples for herbicide resistance.  During the first three years of screening, approximately 1000 samples were submitted; in 2013 alone over 1200 samples were submitted.  These samples have allowed us to monitor the spread of herbicide resistance (and in particular glyphosate resistance) across Illinois (Figure 1).  One point of particular interest in 2013 was that the vast majority of samples were submitted from counties north of Champaign County.

We are pleased to announce that, with continued financial support from the Illinois Soybean Association and Pioneer, we are offering free screening for herbicide resistance in waterhemp during the 2014 growing season.  There is no fee for this service, but please understand that we cannot guarantee when results will be available. Also, because of the way in which we conduct our resistance tests, a test result of “sensitive” to glyphosate does not rule out the possibility that the plant actually is resistant, but by a mechanism that is different than for what we are testing. We would like to assure everyone that we will respect the privacy of those sending samples: we will not make the exact location of any samples, or names associated with samples, available to anyone without your permission. The sample submission form, including submission instructions, is available as a downloadable file. If you have any questions, feel free to contact Pat Tranel (217-333-1531; tranel@illinois.edu).

Sample submission form 2014

Reminder…University of Illinois Weed Science Field Research Tour

We would like to take this opportunity to once again extend the invitation to attend the 2014 University of Illinois Weed Science Field Day, to be held next Wednesday, June 25th at the University of Illinois Crop Sciences Research and Education Center, located immediately south of the main campus.  Coffee and refreshments will be available under the shade trees near the Seed House beginning at 8:00 a.m.  The tour will provide ample opportunity to look at research plots and interact with weed science faculty, staff, and graduate students. Participants can compare their favorite corn and soybean herbicide programs to other commercial programs.  The tour will conclude around noon with a catered barbeque lunch at the Seed House.  Cost for the Urbana weed science field tour is $10, which will help defray the cost of the field tour book, refreshments and lunch.

We look forward to visiting with you at the Urbana weed science field day on June 25th.  Please contact us at 217-333-4424 if you have any questions.