ISU Weed Science Online - Weed Management Resources

Weed Management and News Archives

Weed management is an ever-changing topic. Below are articles, photos, and updates from ISU brought to you by the Weed Management Extension team. Much of the information included here may be specific for Iowa conditions.

INDEX

Weed biology and ecology
   Competition
    Seedbanks and Emergence
    General Biology/Ecology
    Weed Identification

Herbicides
   Application
    Adjuvants
    Drift and injury
    Performance
    General information
    Resistance
    Herbicide Resistant Crops
    Glyphosate

Weed management
   Corn
    Soybeans
    Pasture / CRP
    Waterhemp
    Woolly cupgrass
    Other

Toxicology, environment, water quality, regulatory

Weeds in the News

Weed biology and ecology

Competition

Timeliness is critical, by Bob Hartzler, May 23, 2008
Power of the crop canopy, by Bob Hartzler, January 25, 2007
Role of preemergence herbicides in reducing early-season competition, by Bob Hartzler, February 13, 2006
Importance of timely scouting by Bob Hartzler, May 8, 2005
The importance of an even start , by Bob Hartzler, April 12, 2005
Evaluating risks with total post programs, by Bob Hartzler, Dec.9, 2004
Non-competitive effects of weeds on corn, by Bob Hartzler, Dec. 7, 2004
Managing weeds to protect crop yields, by Bob Hartzler, October 20, 2004
Born to be bad?, by Bob Hartzler, Sept. 2, 2004
Protecting corn yield with postemergence programs, by Bob Hartzler, February 20, 2004
Is your weed management program reducing your net return?, by Bob Hartzler, November 21, 2003
Influence of corn on waterhemp growth, by Dawn Nordby, January 25, 2003
Critical periods of competition, by Bob Hartzler, March 4, 2003
Why two if one will do? by Bob Hartzler, February 18, 2003
Influence of corn on waterhemp growth, by Dawn Nordby, January, 29, 2003
Weed control in Roundup Ready corn, by Bob Hartzler, December 12, 2002
Effect of waterhemp on soybean yields, by Bob Hartzler, September 23, 2002
Preventing early season competition, by Bob Hartzler, May 8, 2002
Effect of woolly cupgrass emergence date, by Bob Hartzler, December 30, 1999
Critical periods of competition in corn, by Bob Hartzler, April 26, 1999
Is One Pass Weed Control a Realistic Goal? - Bob Hartzler
Do farmers know how much weeds reduce yields by Bob Hartzler, Jan. 28, 1997
Optimum yields with total post programs, by Bob Hartzler, October 22, 1997
Early Season Weed Competition by Bob Hartzler, Nov. 18, 1996

Seedbanks and emergence
Seed predators in agricultural fields, by Bob Hartzler, Matt Liebman and Paula Westerman, February 10, 2006
Waterhemp response to mowing, how a weed beats crop rotation, by Bob Hartzler, Dec. 30, 2004
Impact of late-season glyphosate applications on weed seed production, by Bob Hartzler, Aug 9, 2004
Giant ragweed emergence patterns: Part II , by Bob Hartzler, June 5, 2003
Giant ragweed emergence patterns , by Bob Hartzler, January23, 2003
Horseweed emergence influences management, by Bob Hartzler, April, 24, 2001
Fate of weed seeds in the soil, Bob Hartzler, January 6, 2000
Air pollution and seed germination, Science, 23 May, 1997
Larch watch - 1999, by Bob Hartzler, April 1
Weed emergence patterns - 1998, by Bob Hartzler, Nov. 20, 1998
Weed emergence hotline, by Bob Hartzler, April 3, 1998
Weed emergence research, by Bob Hartzler and Doug Buhler, November 26, 1997
Success with bioindicators!!!, by Bob Hartzler, May 1, 1997

General Biology/Ecology
White thistles invade Iowa , by Bob Hartzler, Sept. 11, 2006
Horsetail - Biology and Management , by Bob Hartzler, May 24, 2006
Biennial thistles of Iowa, by Bob Hartzler, March 29, 2006
Scout for winter annuals now, by Bob Hartzler, March 22, 2005
A brief history of Canada thistle, by Bob Hartzler, March 17, 2005
Seed predators in agricultural fields, by Bob Hartzler, Matt Liebman and Paula Westerman, February 10, 2006
Where will our next big weed come from? by Bob Hartzler, December 21, 2005
Seed production following mowing by a summer annual , by Bob Hartzler, Jan. 5, 2005
Non-competitive effects of weeds on corn, by Bob Hartzler, Dec. 7, 2004
Giant ragweed: Return of a native, by Bob Hartzler, Nov. 4, 2004
Born to be bad?, by Bob Hartzler, Sept. 2, 2004
Wind-blown weed seed, Bob Hartzler, May 26, 2004
Waterhemp - the perfect weed? Bob Hartzler, Dec. 18, 2003
Small things do matter, by Bob Hartzler, November 19, 2003
Immune to herbicidal battering, by Bob Hartzler, August 29, 2003
When did that weed emerge?, by Bob Hartzler, April 4, 2003
Multiflora rose and the rose rosette disease. by Bob Hartzler, February 5, 2003
Transfer of herbicide resistance from Clearfield canola, by Bob Hartzler, Sept. 4, 2002
Adaptation in Weeds - Dandelion, by Bob Hartzler, January 31, 2002
Distribution of Common Milkweed in Iowa, by Dawn Refsell, December 14, 2001
Common buckthorn control and the soybean aphid, by Bob Hartzler, August 24, 2001
Introduced species, by Bob Hartzler, Dec. 19, 2000
Sublethal herbicide effects, by Bob Hartzler, June 2, 2000
Changing corn cuticles, by Bob Hartzler, March 26, 2001
Weed population dynamics, by Bob Hartzler, Nov. 6, 2000
Problems with biological control, by Bob Hartzer
Common milkweed in Iowa, by Bob Hartzler, February 3, 2000
Spatial stability of weed populations, Weed Science, Feb. 1997
Spatial weed distributions, by Bob Hartzler, November 14, 1999
Influence of row spacing on weed management, by Bob Hartzler, April 8, 1997
Weed Emergence Patterns by Bob Hartzler, Dec. 31, 1996
Problems with biocontrol, Science, August 22, 1997

Weed ID
New weed ID tool available, by Bob Hartzler, Sept. 16, 2004
Amaranthus Identification Guide, By Mike Owen
Dayflower: A weed to watch?, by Bob Hartzler, May 27, 2003
Weed Identification Resources, by Bob Hartzler
New version of Weed ID CD-ROM available, by Brent Pringnitz, Sept 30, 1998
Purslane speedwell by Brent Pringnitz, May 20, 1999
Weed Seedling ID bulletin by Bob Hartzler, December 11, 1998
Weed seed identification book available, from ICM newsletter, Feb 4, 1997

Herbicides

Application

Evaluating risks with total post programs, by Bob Hartzler, Dec.9, 2004
Managing weeds to protect crop yields, by Bob Hartzler, October 20, 2004
Apply when actively growing? by Bob Hartzler, Dec. 23, 2003
Effect of application timing on herbicide efficacy, by Bob Hartzler, Dec. 5, 2003
Effect of nozzle type on spray retention, by Bob Hartzler, May 8, 2003
Why two if one will do? by Bob Hartzler, February 18, 2003
Drift-reduction nozzle and herbicide efficacy, by Brent Pringnitz, April 29, 2002
Windy days and herbicide drift, by Todd Vagts, April 29, 2002
Performance of Drift-Control Nozzles, by Bob Hartzler, Oct. 15, 2001
UAN as herbicide carrier in emerged corn, by Bob Hartzler, May 3, 2001
Venturi nozzles for drift reduction, by Bob Hartzler, March 23, 2000
Pesticide applications require prior informed consent, by Micheal D. K. Owen, Sept. 30, 1998
Crop canopy and spray coverage, by Bob Hartzler, May 31, 2000
Effect of late-season herbicide applications on weed seed production, by Bob Hartzler, Sept. 14, 1998
Variable rate herbicide application, by Bob Hartzler, August 20, 1998
Time of day influence on Roundup activity, by Bob Hartzler, October 18, 1999
Fall applications: Risks vs. Benefits, by Bob Hartzler,September 21, 1999
Frost and herbicide efficacy, by Bob Hartzler, September 21, 1999
Herbicide application during cool temperatures, by Bob Hartzler, June 3, 1998
Environmental conditions and weed management timing, by Micheal D. K. Owen and Bob Hartzler, May 18, 1998
Late season weed control, by Bob Hartzler and Mike Owen, July 22, 1997
Timing applications of preemergence herbicides, ICM Newsletter, April 7, 1997
Fall Herbicide Application: Risks vs. Benefits from ICM Newsletter, Oct. 7, 1996

Adjuvants
Alternative additives for glyphosate, by Bob Hartzler, Sept. 24, 2003
Effect of water pH on Accent activity, by Bob Hartzler, July 31, 2002
Does adding surfactant improve glyphosate performance, Bob Hartzler, January 2, 2001
Spray adjuvants, a review, by Bob Hartzler, March 13, 2001
Changing corn cuticles, by Bob Hartzler, March 26, 2001
Absorption of foliar-applied herbicides, a review by Bob Hartzler, March 2, 2001
AMS and glyphosate products, by Bob Hartzler, Jan 29, 2001
Clearing up adjuvant confusion, by Brent Pringnitz, April 28, 1998

Drift and injury
Drift management: Nozzles or Drift Retardants
Soil-applied PPO injury to soybean, by Bob Hartzler, May 18, 2005
Herbicide drift versus cold temperature injury , by Bob Hartzler, May 8, 2005
Herbicide residues in soybean following drift, by Bob Hartzler, March 17, 2005
Dealing with drift, by Bob Hartzler, June 28, 2004
Sulfentrazone and flumioxazin injury on soybean, by Bob Hartzler, June 8, 2004
Yield enhancing herbicides, by Bob Hartzler, February 6, 2003
Drift-reduction nozzle and herbicide efficacy, by Brent Pringnitz, April 29, 2002
Windy days and herbicide drift, by Todd Vagts, April 29, 2002
Performance of Drift-Control Nozzles, by Bob Hartzler, Oct. 15, 2001
Dicamba volatility, by Bob Hartzler, July 23, 2001
Effect of glyphosate drift on corn, by Bob Hartzler, May 21, 2001
Venturi nozzles for drift reduction, by Bob Hartzler, March 23, 2000
Sulfentrazone behavior in soil, By Bob Hartzler, Jan. 15, 2001
Crop responses to herbicides, by Bob Hartzler, June 11, 2000
Flexstar carryover, by Bob Hartzler, May 12, 2000
Effect of dicamba on soybean yields, by Bob Hartzler, July 12, 1999
Malformed soybean leaves, by Bob Hartzler, July 10, 1999
Strategies for reducing herbicide drift, by Brent Pringnitz, June 14, 1999
Rootless corn, by Bob Hartzler, June 4, 1999
Balance injury , by Bob Hartzler, June 2, 1999
Trees and herbicide drift, by Bob Hartzler, May 26, 1999
Corn brittleness and growth regulator herbicides, by Bob Hartzler, July 6, 1998
Buggy-whipping in corn, by Bob Hartzler and Brent Pringnitz, August 6, 1997
Drift injury to corn and soybeans, ICM Newsletter, June 16, 1997
Crop Responses to Herbicides from ICM Conference, Bob Hartzler, Nov. 22, 1996
Drift of Sulfonylurea Herbicides, Organic Gardening, Dec. 1996

Performance

The importance of glyphosate translocation, by Bob Hartzler, December 22, 2006
Dust and glyphosate, by Bob Hartzler, December 13, 2006
Herbicides and Temperature, by Bob Hartzler, May 3, 2005
Impact of late-season glyphosate applications on weed seed production, by Bob Hartzler, Aug 9, 2004
Insect interactions with herbicides, by Bob Hartzler, May 13, 2004
Are all metolachlor products equal? Bob Hartzler, January 6, 2004
Apply when actively growing? by Bob Hartzler, Dec. 23, 2003
Cold temperatures and herbicide performance, by Bob Hartzler, May 21, 2003
Effects of weather on herbicide performance, Bob Hartzler, April 11, 2003
Waterhemp control with amide herbicides, by Bob Hartzler, April 1, 2003
Drift-reduction nozzle and herbicide efficacy, by Brent Pringnitz, April 29, 2002
Variable glyphosate tolerance in Iowa waterhemp, Bob Hartzler, March 15, 2002
Absorption of Soil-Applied Herbicides, by Bob Hartzler, March 7, 2002
Variable herbicide performance, by Bob Hartzler, September 25, 2001
Resolved isomers explained, by Bob Hartzler, 2000
Velvetleaf response to Roundup, by Bob Hartzler, Dec. 15, 2000
Herbicide performance and alternative weed management, by Micheal D. K. Owen, May 7, 1998
Volunteer corn control following PP corn, by Bob Hartzler, Dec 21, 1997
Realistic expectations for herbicide performance, ICM Newsletter, May 8, 1997

General information

Resistance isn't the only way to beat a herbicide, by Bob Hartzler, Feb. 14, 2006
Absorption of soil-applied herbicides, by Bob Hartzler, March 7, 2002
Absorption of foliar-applied herbicides, a review by Bob Hartzler, March 2, 2001
Resolved isomers explained, by Bob Hartzler, 2000
Herbicide sites of action, by Bob Hartzler, March 17, 1998
History of herbicide manufacturers, Arnold Appleby, Sept. 23, 1997
Amide wars II - sorting out the facts, by Bob Hartzler, Feb. 27, 1997

Herbicide Resistance

Role of preemergence herbicides in reducing glyhosate selection pressure , by Bob Hartzler, Feb. 13, 2006
Glyphosate resistance in the Cornbelt, by Bob Hartzler, December 21, 2005
2-1-2 , by Bob Hartzler and Mark Loux, October 28, 2005
Glyphosate resistance management - Is it worth the effort , by Bob Hartzler, September 28, 2005
Preserving the value of glyphosate, by Bob Hartzler, Dec. 27, 2004
Are weeds getting harder to kill with glyphosate?, by Bob Hartzler, Dec. 20, 2004
Herbicide combinations to sustain glyphosate, by Bob Hartzler, March 10, 2004
A world apart, by Bob Hartzler, Jan. 14, 2004
Point - Counterpoint, by Bob Hartzler and Mike Owen, February 6, 2003
What, me worry?, by Bob Hartzler, May, 1, 2003
Are Roundup Ready Weeds in Your Future II , by Bob Hartzler, January 29, 2003
Waterhemp resistant to diphenyl ether herbicides, by Bob Hartzler, December 9, 2002
Movement of herbicide resistance from Clearfield canola fields, by Bob Hartzler, September 4, 2002
Farmer Perceptions of Herbicide Resistance, by Bob Hartzler, Feb. 25, 2002
Search for resistance mechanism in ryegrass, by Bob Hartzler, February 27, 2001
Herbicide exploitation, By Bob Hartzler, Aug 11, 2000
Glyphosate resistance update, by Bob Hartzler, December 6, 1999
Roundup Resistant Rigid Ryegrass, by Bob Hartzler, October 22, 1998
Roundup resistant weeds in Australia, May 15, 1998
Are Roundup Ready weeds in your future, by Bob Hartzler, Nov. 3, 1998
Herbicide resistance update, by Bob Hartzler, Oct. 30, 1998
Do reduced rates increase the risk of resistance? by Bob Hartzler, Jan.25, 1999
Herbicide resistance: who's resisting?, Weed Science, August 1997
Persistence of herbicide resistance, Weed Technology, June 1997
ALS resistant foxtail in Minnesota, by Bob Hartzler, March 17, 1997
ALS resistance - current status in Iowa by Bob Hartzler, Jan. 16, 1997
Antibiotic resistance: Road of no return, Science, October 24, 1997
Roundup Resistant Weeds - Can it happen?, Resistant Pest Management , Winter, 1996

Herbicide Tolerant/Genetically Modified Crops
Movement of herbicide resistance from Clearfield canola fields, by Bob Hartzler, September 4, 2002
Distribution of Common Milkweed in Iowa, by Dawn Refsell, December 14, 2001
Monarch butterflies and HRC's, Science, 8 Jan, 1999.
North American Developments in Herbicide Tolerant Crops, British Crop Protection Conference, Novemenber, 1997
Volunteer corn control following PP corn, by Bob Hartzler, Dec 21, 1997
Europe and transgenic crops, Science, 21 February, 1997
Purity of Liberty-Link seeds, by Bob Hartzler, June 6, 1997
Monsanto playing God?, Riverfront Times, 11 December, 1996
Can Transgenic Crops Create Superweeds?,Science, 11 Oct 1996
Give me Liberty, or give me . . .?, Dealer PROGRESS, March/April 1997

Weed management

Corn
Importance of timely scouting for weeds , by Bob Hartzler, May 12, 2005
Protecting corn yield with postemergence programs, by Bob Hartzler, February 20, 2004
Are all metolachlor products equal? Bob Hartzler, January 6, 2004
Weed management concerns in corn, by Bob Hartzler, May 9, 2003
Waterhemp control with amide herbicides, by Bob Hartzler, April 1, 2003
Callisto and organophosphate insecticides, by Bob Hartzler, December 3, 2002
Postemergence options for grass control in corn, by Bob Hartzler, May 13, 2002
Preventing early season competition, by Bob Hartzler, May 8, 2002
Timelines is everything, by Bob Hartzler, May 1, 2001
Effect of glyphosate drift on corn, by Bob Hartzler, May 21, 2001
UAN as herbicide carrier in emerged corn, by Bob Hartzler, May 3, 2001
Changing corn cuticles, by Bob Hartzler, March 26, 2001
Dicamba package mixes, by Bob Hartzler, Sept. 8, 1999
Amide Wars II, by Bob Hartzler, 1997 article updated on Jan. 17, 2000
Critical periods of competition in corn, by Bob Hartzler, April 26, 1999

Soybeans

Is your weed management program reducing your net return?, by Bob Hartzler, November 21, 2003
Dayflower: A weed to watch?, by Bob Hartzler, May 27, 2003
Effect of waterhemp on soybean yields, by Bob Hartzler, September 23, 2002
Common buckthorn control and the soybean aphid, by Bob Hartzler, August 24, 2001
Giant ragweed control with FirstRate, by Bob Hartzler, March 3, 2000
Effect of weeds on soybean harvest efficiency, by Bob Hartzler, August 17, 1998
Effect of dicamba on soybean yields, by Bob Hartzler, July 12, 1999
Malformed soybean leaves, by Bob Hartzler, July 10, 1999
2,4-D use in soybeans, by Micheal D. K. Owen, May 7, 1998

Pasture/CRP

Controlling eastern red cedar, by Bob Hartzler, April 28, 2006
Now's the time to control biennials, by Bob Hartzler, March 29, 2006
Biennial thistles of Iowa, by Bob Hartzler, March 29, 2006
A brief history of Canada thistle, by Bob Hartzler, March 17, 2005
Aminopyralid - a new herbicide for pastures, by Bob Hartzler, February 21, 2006
Multiflora rose and the rose rosette disease. by Bob Hartzler, February 5, 2003
Canada thistle management, by Bob Hartzler, Feb. 6, 2002

Waterhemp
Waterhemp response to mowing, how a weed beats crop rotation, by Bob Hartzler, Dec. 30, 2004
Waterhemp - the perfect weed? Bob Hartzler, Dec. 18, 2003
Amaranthus Identification Guide, By Mike Owen
Variable response of Iowa waterhemp to glyphosate, Bob Hartzler, May 1, 2003
Waterhemp control with amide herbicides, by Bob Hartzler, April 1, 2003
Influence of corn on waterhemp growth, by Dawn Nordby, January 25, 2003
Effect of waterhemp on soybean yields, by Bob Hartzler, September 23, 2002
Variable glyphosate tolerance in Iowa waterhemp, by Bob Hartzler, March 15, 2002
Waterhemp Research Results, by Bob Hartzler, December 14, 2001
Waterhemp and glyphosate, by Bob Hartzler, March 29, 2001
Late-emerging waterhemp, by Bob Hartzler, Dec.2, 1998
Waterhemp management, by Bob Hartzler, Dec. 24, 1997 (update of an earlier article)
Waterhemp Management by Bob Hartzler, Oct. 10, 1996

Woolly cupgrass
Management of woolly cupgrass, by Bob Hartzler, Nov. 2, 2001
Effect of woolly cupgrass emergence date, by Bob Hartzler, December 30, 1999
Management of Woolly Cupgrass by Bob Hartzler & Mike Owen, Dec. 3, 1996
Effect of woolly cupgrass emergence date, by Bob Hartzler, December 30, 1999

Other
Multiflora rose and the rose rosette disease. by Bob Hartzler, February 5, 2003
Weed control in tree plantings, by Bob Hartzler, April 10, 2002
Canada thistle management, by Bob Hartzler, Feb. 6, 2002
Velvetleaf response to Roundup, by Bob Hartzler, Dec. 15, 2000
Problems with biological control, by Bob Hartzer

Toxicology, environmental, water quality, regulatory
Dealing with drift, by Bob Hartzler, June 28, 2004
Changes in atrazine carcinogen rating, by Brent Pringnitz, January 30, 1999
Standpipe Setbacks on Tile-Outlet Terraced Fields by Mike Owen, Jan. 16, 1997
Changes in atrazine setbacks by Bob Hartzler, Jan. 3, 1997
Pesticide use trends in Europe, April 20, 1998
Air pollution and seed germination, Science, 23 May, 1997
Egg laying male carp, Science, 13 December, 1996

"Weeds in the News" and editorial articles
California bans handweeding, by Bob Hartzler, Oct. 1, 2004
The future of farming?, by Bob Hartzler, March 28, 2004
Concerns over Roundup Ready creeping bentgrass, by Bob Hartzler, March 12, 2004
Immune to herbicidal battering, by Bob Hartzler, August 29, 2003
A glimpse of the future?, by Bob Hartzler, January 23, 2003
How Low Can They Go?, by Bob Hartzler, March 4, 2002
It Ain't Chickenfeed, by Bob Hartzler, Feb. 20, 2002
Save the Monarch - Plant Milkweed!! , by Bob Hartzler, Feb. 4, 2002
Introduced species, by Bob Hartzler, Dec. 19, 2000
Plants without virtue, by Bob Hartzler, May 15, 2000
Dandelions, biological control, and extinct species, by Bob Hartzler, July 16, 1999
Prime time weeds, by Bob Hartzler, May 21, 1999
Herbicide Ad Hall of Shame, May 26, 1998
Promiscuity in transgenic plants, by Bob Hartzler, December 21, 1998
Position paper on prescription pesticide use issued by CAST, by Micheal D. K. Owen, Sept. 30, 1998
Philosophies in Extension Weed Management, North Central Weed Science Society, November 15, 1997
Poison Ivy home remedy?, by Bob Hartzler, July 9, 1997
Unsafe pesticide use, by Mike Owen, July 1, 1997
Agricultural chemical industry news: A synopsis, May 11, 1998
Pesticide use trends in Europe, April 20, 1998
Antibiotic resistance: Road of no return, Science, October 24, 1997
Leafy spurge - A Henry Kissinger for the 90's, Des Moines Register, August 1, 1997
Just the facts, Governor, Des Moines Register, July 22, 1997
A farmer's struggles with weeds, Des Moines Register, July 20, 1997
Use of pesticides down in Europe,by Micheal D.K. Owen, 5, June, 1997
Air pollution and seed germination, Science, 23 May, 1997
Report of global pesticides sales for 1996, by Micheal D.K. Owen, 26 March, 1997
He should have been in extension, Science, 7 March, 1997
We've come a long way, baby, Iowa State College, 1953?
Monsanto playing God?, Riverfront Times, 11 December, 1996
Give me Liberty, or give me . . .?, Dealer PROGRESS, March/April 1997
The invincibility of herbicides?, by Bob Hartzler, 10 February, 1997
Biosphere 2: Morningglories contribute to failure of ecosystem Science, 15 Nov 1996

For more information contact:
ISU Extension Agronomy
2104 Agronomy Hall
Ames, Iowa 50011-1010
Voice: (515) 294-1923
Fax: (515) 294-9985
http://www.weeds.iastate.edu

Submit questions or comments here.

Common chemical and trade names are used in this publication. The use of trade names is for clarity by the reader. Inclusion of a trade name does not imply endorsement of that particular brand of herbicide and exclusion does not imply nonapproval.