Bob Hartzler

July 7, 2022 4:25 PM

30 a.m.

The annual ISU Extension & Outreach Iowa State Fair Weed Identification Contest will be held on...

September 7, 2021 2:25 PM

Although I am retired, I still am passionate about weeds and decided to continue my Labor Day Tour of the first known infestations of Palmer amaranth in Iowa. I started this ‘survey’ in 2014, links to earlier reports are found at the end of this article. My efforts do not involve a systematic...

June 1, 2021 1:31 PM

The first ‘official’ finding of Palmer amaranth in Iowa was August 2013 in Harrison County. Shortly thereafter the weed was identified in Muscatine, Fremont and Page County. These infestations were likely due to Palmer amaranth seed being transported on equipment/trucks involved in crop...

March 26, 2021 12:55 PM

Volunteer corn remains high on many minds this spring and one of the biggest questions is how much of those corn seed will germinate this spring. In an effort to learn more about the challenge we’re facing, Bob Hartzler collected soil and corn ears from the same fields he collected from last...

Crop Production, Weeds
February 25, 2021 1:12 PM

The 2020 registration for Xtendimax, Engenia and the extension of the Tavium registration included additional restrictions for protection of Endangered Species. 

Iowa counties with Endangered Species protection include Allamakee, Cerro Gordo, Clayton, Delaware, Dickinson, Dubuque, Emmet,...

Pesticide Education
February 15, 2021 8:57 AM

Reliance on synthetic auxin herbicides (HG 4) has increased following the introduction of dicamba and 2,4-D resistant soybean. A common question among users of these products is: “If I use one trait repeatedly and select for resistance to that herbicide, will I be able to switch to the other...

Herbicide Resistance
February 10, 2021 3:57 PM

The 2021 Herbicide Guide for Iowa Corn and Soybean Production is now available as a free download at the ISUEO Extension Store.

In addition to numerous tables providing information on the myriad of herbicides for use in corn...

February 1, 2021 6:44 AM

Herbicide-resistant weeds are the norm in cropping systems reliant on herbicides, with more than 500 unique cases of resistance reported worldwide in 2019 ( However, the ability to accumulate multiple resistances within a single...

Herbicide Resistance
November 4, 2020 1:22 PM

This week is a welcome break from the fall chill, and it is a great opportunity to finish up any final fall weed management in pastures and no-till crop fields. Ideally, herbicide applications should be made when the sun is shining and daytime temperatures are above 50-55 degrees Fahrenheit....

October 28, 2020 7:58 AM

Most people are aware that EPA approved new labels for the dicamba products used on dicamba-resistant crops. The following describes major changes in the labels and important restrictions.  The labels only describe use on the dicamba-resistant crops, therefore eliminating some of the confusion...

October 7, 2020 1:03 PM

A concern for corn fields damaged by this year's Derecho is how best to manage volunteer corn in 2021. Our recommendation is to rotate to soybean or some other crop if at all possible since additional control options are available in soybean (...

September 21, 2020 2:42 PM

August's derecho left many Iowans with unharvestable corn. For operations that left their corn in the field, decisions should be made to reduce the problem of volunteer corn next planting season. 

In this video, Field Agronomist Meaghan Anderson and Weed Specialist Bob...

September 7, 2020 8:19 AM

Harrison County: Ground zero for Palmer amaranth in Iowa is a 25 acre field that had a severe Palmer amaranth infestation when the weed was first identified in 2013.  Since then populations have consistently declined - this year I was unable to find any Palmer in the field,...

September 3, 2020 11:57 AM

Downed corn from the August 10 Derecho, which affected millions of acres in Iowa, will contribute to significant volunteer corn populations in crop fields in 2021. Volunteer corn ranging from 800 to 13,000 plants per acre can cause yield losses up to 54% in soybean and up to 13% in corn,...

August 27, 2020 8:07 AM

Dear regulators,

I assume you are evaluating data and reviewing information that will guide your decision regarding the re-registration of dicamba for use in dicamba-resistant (DR) crops. As you know, farmers have a critical need for additional tools to help manage herbicide-resistant...

July 8, 2020 7:00 AM

There is no question that dicamba injury across the Iowa landscape in 2020 is the most extensive it has been since the introduction of dicamba in the 1960s. ISUEO field agronomists and commercial agronomists in several areas of the state report nearly all non-dicamba resistant soybean are...

July 3, 2020 10:20 AM

Nearly 20 years ago I summarized research from the University of Minnesota investigating factors that influence volatilization of dicamba (Behrens and Lueschen. 1979. Dicamba volatility. Weed Sci...

June 29, 2020 6:46 PM

We’ve seen more herbicide injury to soybean than I recall in past summers, resulting in questions about determining the source and reasons for the damage. This ICM Blog will share some tips on identifying herbicide injury we’ve seen this summer in soybean fields.

Crop injury may be caused...

Weeds, Herbicide Resistance
June 25, 2020 10:01 PM

There have been a few fields where topramezone – the active ingredient in Impact and Armezon – carried over from an application last June – and is injuring this year’s soybean crop. Other agronomists have reported carryover of other Group 27 herbicides on soybean this year (mesotrione,...

Crop Production
June 9, 2020 1:59 PM

One important benefit of cover crops to our production system is providing an alternative selection pressure on weed populations. Cereal rye has the best potential to suppress weeds because it accumulates more biomass than other cover crop species.  Weed suppression is closely related to the...

June 5, 2020 6:47 AM

Numerous herbicides registered for postemergence use on Xtend soybean have excellent activity on important weeds of Iowa’s soybean fields. Unfortunately, herbicide resistance in waterhemp is widespread to the herbicide groups active on this weed: Group 2 (ALS inhibitors), 9 (glyphosate) and 14 (...

Herbicide Resistance
June 2, 2020 10:10 AM

Although there is no evidence of widescale problems with carryover injury to corn or soybean, ISUEO field agronomists have received a few reports. The potential for carryover injury is determined by several factors, including: 1) persistence of the herbicide, 2) herbicide rate, 3) soil...

May 22, 2020 10:04 AM

I try to stay focused on important weed management issues, but people1 send me ads they feel need to be called out for breaking the principles of integrated weed management. Today's entry into the Herbicide Ad Hall of Shame is a promotion for Tough herbicide.  I don't...

Herbicide Resistance
May 11, 2020 10:23 AM

Although most crop fields have not reached the stage for regularly planned POST herbicide applications, there likely are situations where people would like to get weeds controlled prior to the rain forecast later this week.  The question is what impact will this weekend’s frost have on herbicide...

May 1, 2020 8:49 AM

Planting occurred at a near record pace in much of Iowa due to lack of rain in late April. This string of dry weather also allowed most herbicide applications to be made in a timely fashion, but now there is concern about herbicide performance after prolonged time on the soil surface.