Bob Hartzler

Dr. Bob Hartzler is a professor of agronomy and an extension weed specialist. He conducts research on weed biology and how it impacts the efficacy of weed management programs in corn and soybean. Dr. Hartzler also teaches undergraduate classes in weed science and weed identification.

Bob Hartzler image
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,...

Weeds
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,...

Weeds
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...

Weeds
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...

Weeds
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...

Weeds
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...

Weeds
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...

Weeds
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...

Weeds
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.

...

Weeds
February 4, 2020 8:02 AM

After a fairly long hiatus, a tweet from Corteva has earned a coveted spot in the HOS. This is a tough one since the company has used a farmer’s quote to disregard the principles of integrated weed management, rather than someone in marketing dreaming up an irresponsible advertisement.

...

Weeds
January 13, 2020 4:30 PM

Although ‘pure’ botanists often scoff at the use of common names for plants, common names are a useful tool when working with domesticated plants and weeds since the pool of species is relatively small.  One problem with common names is they may vary from location to location. When I started...

Weeds
November 11, 2019 7:08 AM

Waterhemp’s rise to the Cornbelt’s worst weed is one of the Cornbelt’s more fascinating weed-related events over the past 40 years.  Waterhemp (Amaranthus tuberculatus) is native to the United States but is a relative newcomer to crop fields. Prior to waterhemp’s ascent, redroot pigweed...

Weeds
October 19, 2019 8:58 AM

Combines are the most important seed dispersal mechanism for weeds in our cropping system.  While a small amount of seed may leave the field with grain, most weed seed that enter the combine with the crop are either spread throughout the field or carried to other fields. Harvest weed seed...

Weeds
September 30, 2019 1:00 PM

The spread of multiple-resistant weeds threatens Iowa’s production system. In order to slow the expansion of resistance, greater diversity in weed management is necessary.  An October 21 workshop will discuss one potential alternative weed management tool that is used in other parts of the world...

Weeds
September 4, 2019 7:55 AM

Sensing an impending lackluster performance by the Cyclone football team, I spent the Saturday of Labor Day weekend touring several Palmer amaranth infestations in western Iowa. This is the 6th year of this trek, the first stop is always Harrison County at the first reported Iowa...

Weeds
August 13, 2019 9:48 AM

The current approach to weed management in Iowa is at risk due to rapid expansion of herbicide-resistant weeds. In order to preserve the efficacy of herbicides two things must happen: 1) adoption of integrated weed management, and 2) shift the goal of weed management from protecting crop yields...

Herbicide Resistance
August 12, 2019 2:28 PM

The 2019 Iowa State University Extension and Outreach Iowa State Fair Weed Identification Contest was held on August 9 outside the John Deere Agriculture Building.  Contestants need to identify live samples of weeds of agricultural, horticultural, and natural habitats in Iowa.  Youth are tasked...

Weeds
July 17, 2019 7:49 AM

Question: If the state and county are so concerned about wild parsnip, why aren’t they out spraying it? The ditches and county roads are full of it.1

...

Weeds
July 17, 2019 6:29 AM


Contestants at the 2018 State Fair Weed Identification Contest

The annual ISU Extension &...

Weeds
June 21, 2019 12:06 PM

Wild parsnip is a biennial that was introduced to North America by the earliest European colonists, it is documented to have been grown in Virginia as early as 1609 as a food crop. In his 1913 book The Weed Flora of Iowa, L. H. Pammel described wild parsnip as ‘common on roadsides in...

Weeds
June 5, 2019 8:42 AM

Corn planting has been start and stop, and generally delayed this spring. In some situations the decision was made to plant and not apply nitrogen, or planting progressed so quickly that UAN (urea-ammonium nitrate solution) and herbicide applications couldn’t keep up with the planters, and now...

Weeds

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