Prof. Bob Hartzler

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  wallacesfarmer.com/story.aspx?s=17112&c=9 - [Cached Version]
  Published on: 5/5/2008    Last Visited: 8/17/2009  

  There are several advantages of including 2,4-D in with the glyphosate, says Bob Hartzler, Iowa State University Extension weed management specialist. It provides better activity on dandelion, horseweed and many winter annual broadleaf weeds than glyphosate alone. It provides more consistent control than glyphosate used along during cool conditions. It reduces the selection pressure for glyphosate resistant horseweed.
  
  "The risk associated with 2,4-D use is injury to emerging corn or soybean plants," notes Hartzler. For soybeans, a seven-day interval between application of 0.5 pounds 2,4-D/A (2/3 part of a 6 pounds LVE formulation) and planting is required.
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  Hartzler says this is determined by several factors, including--depth of planting, 2,4-D rate and formulation, soil type and rainfall.
  
  "Planting seed at proper depth reduces the risk of injury by providing a more favorable environment for germination and minimizing the amount of herbicide reaching the seed," says Hartzler.
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  Corn is most sensitive to 2,4-D when the herbicide is present in the water that is initially imbibed by the seed, this is why 2,4-D can be applied shortly after planting, says Hartzler.
  
  "2,4-D is a valuable tool in no-till systems, but it must be used properly to manage the risk of crop injury. In situations where the planting interval restrictions cannot be followed, alternative herbicide products are available," he adds.

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  www.lesspub.com/cgi-bin/site.pl?332&ceNews_newsID=6970 - [Cached Version]
  Published on: 5/8/2009    Last Visited: 5/8/2009  

  The primary cost associated with these weeds is interference with crop establishment and early season growth, says Bob Hartzler, Iowa State University weed specialist.
  
  He says some no-tillers question whether it's better to control winter annuals prior to planting or just wait to deal with them at planting. In most situations, the best option will be to control winter annuals as soon as it's fit to get into the field.
  
  "Winter annuals become more difficult to control as they mature, therefore increasing herbicide costs," Hartzler says. "For some weeds, herbicide rates may simply need to be increased. Whereas, some weed species will require additional herbicides."
  
  For example, Hartzler says horseweed (marestail) can be controlled consistently with glyphosate and 2,4-D when in the rosette stage.
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  However, Hartzler says delays in control may allow winter annuals to go to seed prior to the burndown treatment. Therefore, early spring applications will prevent increases in the winter annuals that can reduce problems in future years.
  
  Another advantage with early spring applications is eliminating concerns with the planting interval required following 2,4-D applications, Hartzler says. Corn or soybean should not be planted until 7 days after application of 1 pint of 2,4-D.
  
  Ester formulations are recommended over amines due to a shorter planting interval for esters (15-day interval when soybeans are planted following 1 pint 2,4-D, 4 lb amine). In addition, esters often perform better under the cool conditions commonly encountered with spring applications.
  
  "Inclusion of residual herbicides with the burndown treatment should provide a weed-free seedbed at planting, therefore eliminating the need for applying herbicides at planting," Hartzler says.

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  www.lesspub.com/cgi-bin/site.pl?332&ceNews_newsID=7314 - [Cached Version]
  Published on: 5/19/2009    Last Visited: 5/19/2009  

  Poison hemlock, a biennial in the carrot family (Apiaceae), is becoming more common in crop fields as no-till acres increase, says Bob Hartzler, Extension weed specialist for Iowa State University.
  
  Infestations typically start in fencerows or other less intensively managed areas and creep into production fields, he says. Like other biennial weeds, its tolerance to control tactics increase rapidly as the plant moves from a vegetative rosette to reproductive stages in early spring.
  
  "The simplest method of controlling poison hemlock is to eliminate seed sources in areas adjacent to the field," Hartzler says. "Fall applications of 2,4-D plus dicamba are highly effective against the plant. Applications to these areas can be made following corn or soybean harvest, and infested areas of crop fields should be treated at the same time."
  
  Poison hemlock will not be controlled consistently by the standard burndown program of glyphosate + 0.5 pounds per acre of 2,4-D LVE (1 pint per 4 pound a.e./gallon), Hartzler says. Increasing the rate of 2,4-D LVE to 1 pound will improve control, but this requires a 15-day planting interval for soybeans and 7- to 14-day interval for corn.
  
  Alternatives to the standard glyphosate + 2,4-D burndown treatment include dicamba (14-day planting interval is required before planting soybeans following an 8 ounce application of Clarity) or Basis (corn only). Field observations suggest that mesotrione (Callisto, Lumax, etc.) has activity on poison hemlock, but Hartzler says he is unaware of any research documenting the products' effectiveness on poison hemlock.
  
  "Poison hemlock in no-till fields may have reached a stage where consistent control will not be achieved by any registered treatment," Hartzler says.

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  www.dtnag.com/dtnag/common/link.do?symbolicName=/ag/blo - [Cached Version]
  Last Visited: 11/21/2007  

  Bob Hartzler, weed scientist at Iowa State University said "Atrazine isn't labeled for fall applications (except for Kansas where they have a Special local need label).

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  www.farmnews-iowa.com/news/articles.asp?articleID=6005 - [Cached Version]
  Published on: 7/28/2008    Last Visited: 7/28/2008  

  Dr. Bob Hartzler, ISU Extension Weed Specialist shared with the group research done on weed competition management at the Northern Research and Demonstration Farm field day held recently near Kanawha.
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  Dr. Bob Hartzler, extension weed specialist, was on hand to discuss weed issues affecting crops this year with the emphasis being on weed competition management.
  
  There are two primary factors in how weeds impact crops, Hartzler said.These are competition — how weeds tie up water and nutrients making them unavailable to the crop — and how certain plants can release a chemical into the soil that affects row crop plant growth.
  
  This second factor, he said, is not a huge significance in annual crop production, but something to consider and is a subtle influence.Plants react when they sense other types of plants are growing near them.
  
  He then provided research results explaining the effect weeds have on corn.
  
  ‘‘The purpose of the research being conducted was to illustrate the timeliness in weed control and how differences can really hurt you," said Hartzler.
  
  For this project, Hartzler said, researchers planted the crop and then put grass seed over the top, which resulted in a higher density of weeds than they expected.However, research showed that weeds have a significant impact on corn in just six days.
  
  Hartzler continued on with the complications of weed competition in corn explaining how weeds tie up nitrogen from corn, but concluded that with the products and machines available to producers today, weeds should be manageable.
  
  ‘‘Manage weeds.There are more tools available now.Use properly to manage risk.Use them to manage weeds and protect yields," Hartzler said.

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  www.biotechknowledge.com/BIOTECH/knowcenter.nsf/ID/A5D3 - [Cached Version]
  Published on: 1/2/2000    Last Visited: 2/3/2004  

  Dr. Doug Buhler, research agronomist at the USDA-ARS, and Dr. Robert Hartzler, associate professor and Extension weed scientist in the Agronomy Department at Iowa State University, found that Iowa roadsides had 48 common milkweed patches per hectare, while corn and soybean fields had only seven patches per hectare.
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  In another survey, Hartzler and Buhler also found that the majority of milkweeds along roadsides were distant from field edges.

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  www.native-landscaping.com/invasives.htm - [Cached Version]
  Published on: 4/6/2007    Last Visited: 4/6/2007  

  - Bob Hartzler, Extension Weed Management Specialist, Dept. of Agronomy, ISU

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  www.lesspub.com/cgi-bin/site.pl?332&ceNews_newsID=4763 - [Cached Version]
  Published on: 7/1/2008    Last Visited: 7/1/2008  

  Iowa State University research has found that less than 1% of waterhemp emerging at the V8 corn stage survives, says Bob Hartzler, professor of weed science at Iowa State.
  
  While there was higher survival at earlier emergence dates, biomass and seed production of waterhemp emerging at the V5 corn stage was suppressed more than 90% compared to plants emerging with corn.
  
  Hartzler says any corn fields across Iowa and parts of the Midwest are likely to have greater problems with late-emerging weeds than normal.He says there are two primary causes for these infestations:1) The heavy rain in May and early June will reduce the length of control provided by residual herbicides, and2) Poor canopy development due to cool temperatures, saturated soils and reduced stands will provide a favorable environment for weed growth.
  
  "Fields should be carefully evaluated prior to spraying weeds in large corn," Hartzler says."Weeds that emerge significantly later than the corn--anytime beyond the V3 stage--are at a tremendous competitive disadvantage with the crop due to the crop's head start.While these weeds may survive and produce seed, their impact on the corn yield should be minimal unless they are thick enough to create a sod."
  
  As a result, Hartzler says if you have 3- to 4-inch weeds in 30-inch corn, it probably does not warrant an additional weed control trip.Spraying corn beyond the V8 stage may cause more damage to the crop than would be gained by eliminating late-emerging weeds.
  
  He adds that the majority of herbicide labels prohibit application to larger corn due to problems with crop tolerance or efficacy.Glyphosate restricts applications to corn less than the V8 stage or 30 inches in height.
  
  "While everyone likes to see a weed-free field at harvest, sometimes it's best simply to live with the hand that has been dealt," Hartzler says.

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  www.farmnews-iowa.com/printPage.asp?articleID=5990 - [Cached Version]
  Published on: 7/11/2008    Last Visited: 7/28/2008  

  Standing in front of a bean plot with weeds, Bob Hartzler, extension weed scientist, posed the question, ‘‘Are these weeds causing a yield reduction?"
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  Plants only have so much energy, Hartzler said.In order to grow taller the plant scavenged resources from the roots to produce more leaf and stem biomass.The sacrifice in roots could be detrimental as the season progresses, he explained.
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  Hartzler differs from Palle Pederson in plant population thinking.

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  www.desmoinesregister.com/article/20091008/BUSINESS01/9 - [Cached Version]
  Published on: 10/8/2009    Last Visited: 10/8/2009  

  Atrazine is used widely in combination with other herbicides because it stays in the soil and can kill weeds that other chemicals miss, said Bob Hartzler, a weed specialist at Iowa State University.

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