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 19, 2016 6:42 AM

I tell students in my ID class that weed identification is easy since very few species have traits that allow them to persist in disturbed habitats, thus you run into the same weeds over and over. After a few years in the business, you seldom encounter a weed you haven’t dealt with before. That...

September 12, 2016 12:48 PM

As you venture around the countryside this time of year you might notice the presence of a plant with white flowers along the edge of woodlands. There is a good chance this plant is white snakeroot, a perennial in the Asteraceae (sunflower family). The plant is adapted to shady areas with low...

September 6, 2016 2:00 PM

I took my final Labor Day Palmer amaranth tour on Saturday, visiting the first three known sites of Palmer amaranth in western Iowa. First stop was Harrison County, ground zero for Iowa Palmer amaranth. The Palmer was identified in the summer of 2013 in a 50 acre fallow field; because of the...

August 30, 2016 8:35 AM

The first step in managing any pest is correct identification. For Palmer amaranth, we have stressed the need to examine the inflorescences of female plants for the presence of the large, sharp bracts. Farmers/agronomists are not accustomed to examining flowers since almost all weeds can be...

August 25, 2016 2:37 PM

Most people are aware of the multiple findings of Palmer amaranth across Iowa this month.  Palmer amaranth has been identified both in crop fields and in conservation plantings using native seed mixes.  Early detection is essential in order to prevent the new weed from getting permanently...

August 14, 2016 10:13 AM

Although rain moved us indoors, we had a great turnout for the 2016 Weed Identification Contest.  This year's winner in the Professional Division is long-time participant Cindy Recker of Peosta, IA.  Cindy, a member of ISU's Crop Judging Team when she was a student, correctly identified 37 of 40...

July 29, 2016 7:51 AM

Iowa Code 317 is the section of the Iowa Code that defines the Iowa Noxious Weed Law.  Chapter 317.1 is the piece of legislation that actually defines which...

July 25, 2016 12:35 PM

Japanese knotweed is one of the most difficult weeds to eradicate due to its extensive woody root system.  In England it is notorious for caving in basement walls where it was planted as a foundation plant.  At least 15 years ago I discovered a 'nice' patch of Japanese bamboo along the banks of...

July 18, 2016 11:14 AM

I’ve seen more people walking beans and had more comments about it than I can remember in a long time.  Perhaps it's time for Greg Brown to re-release his classic ‘Walking the Beans’, first released on ‘The Iowa Waltz’ album in 1981....

July 13, 2016 1:56 PM

The current epidemic of wild parsnip has garnered much attention due to the toxins present in the plant.  Since wild parsnip is a biennial, mowing is often recommended as a control option.  The theory is that by preventing seed production, mowing can eliminate future infestations.  In practice,...

July 6, 2016 7:36 AM

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. In his 1913 book The Weed Flora of Iowa, L. H. Pammel described wild parsnip as ‘common on roadsides in every part of...

June 10, 2016 4:11 PM

One of the less rewarding tasks of pest management is gleaning information from pesticide labels. Because of the complexity of labels, many people rely on guides produced by universities or distributors to identify solutions for pest problems. While these guides are convenient, they are not...

Pesticide Education
May 27, 2016 6:27 AM

Researchers at the University of Illinois recently published a paper identifying the PPO resistance mechanism in Palmer amaranth.  It turns out that both Palmer and waterhemp have an unusual type of mutation providing resistance to the group 14 herbicides (PPO inhibitors).  Rather than a...

Herbicide Resistance
May 26, 2016 7:12 AM

Plants with yellow flowers are a common sight in roadsides and other grassy areas as one drives across Iowa at this time of year. There's a good chance these plants are one of the weedy mustards (wild mustard, yellow rocket, hedge mustard, etc.), golden alexander, or wild parsnip. The mustards...

May 24, 2016 12:56 PM

While I don't have a bucket list of weeds, it's always nice to find a new one. Today I had my first encounter with blue mustard (Chorispora tenella). Like all mustards, this plant has four petals, but the petals of blue mustard are pink to purple in color and very narrow, relative to...

May 20, 2016 9:47 AM

I've had several questions on how long to wait following the frost event this past weekend before making a postemergence application. The answer depends on several factors, including 1) stage of corn at frost injury, 2) vigor of corn at time of frost, 3) weather following the frost, and 4)...

May 19, 2016 1:08 PM

While driving to a field plot in Webster County earlier this week I saw a land roller being used in a field. My first thought: "If we have time to roll fields, why is there such resistance to the suggestion of mechanical weed control?"

Most farmers of my age have...

May 18, 2016 6:26 AM

Scouring rush and field horsetail are two species in the Equisetum genus. These are primitive plants that produce spores rather than seeds, but they spread primarily by underground rhizomes. Until recently these two weeds were found primarily in roadside ditches, but the reduction in...

April 23, 2016 9:48 AM

Had a question why winter annuals, specifically henbit, are so thick this year.  Two main factors: 1) ample moisture at the end of last year's growing season, and 2) a relatively mild winter.  Most winter annuals emerge in late August-September, in many years we don't have enough soil moisture...

April 19, 2016 9:49 AM

The focus has been on planting corn, but don't forget about the weeds. In addition to getting preemergence herbicides applied to the corn acres, burndown applications on no-till soybean fields should be a top priority. Timely application of burndown herbicides simplifies controlling many winter...

April 9, 2016 12:36 PM

A 'true' weed ecologist probably would have shuddered at my explanation to young 4-H'ers how weeds survive our control efforts:  

1) shake them off (giant ragweed) or 2) overrun them with numbers (waterhemp).


April 5, 2016 8:13 AM

The rapid spread of herbicide resistant weeds threatens the current Midwest production system. Introduction of new herbicide resistance traits will provide additional management options for resistant-prone weeds such as waterhemp, giant ragweed, and marestail; however, these systems must be used...

Herbicide Resistance
March 16, 2016 10:37 AM

While walking through the Memorial Union a painting caught my eye. The resemblance between Palmer amaranth seedheads and the artwork was striking, my photography skills not so much.


March 13, 2016 7:29 AM

Question: What was the most popular POST herbicide program for corn in Iowa Crop Reporting Districts 1 and 2 (NW and NC Iowa) in 1985?

Answer: 2,4-D + Banvel (dicamba), with 78 and 64% of the acres treated, respectively.

Every time I see an...

February 28, 2016 9:11 AM

The overwintering monarch population in Mexico was reported last week and has increased for the second consecutive year (Figure 1). Four hectares of forest (9.9 acres) were covered with monarchs, up from the low of 0.7 hectares in the winter of 2013-14. While this is good news, the low numbers...

Insects and Mites