Post on 12-Feb-2017
The importance of herbicides, biotechnology and evolved herbicide
resistance in weeds on crop production – the need for continued innovation
Micheal D.K. OwenUniversity Professor
Agronomy DepartmentIowa State University
Introduction• Weed management tactics, in a general
sense, have not changed appreciably in several decades– Tactics include cultural, mechanical, biological
and herbicidal• Specific tactics however have seen many
changes reflecting not only technological improvements but also addressing social and economic considerations
Introduction
• Despite the fact that evolved resistance to herbicides has been a concern for four decades, new resistances have tipped the cart
• There are a number of problems in managing herbicide resistant weeds– Grower knowledge– Time management– Economic concerns– Lack of new herbicides
Evolution of row cropweed management
1900 1920 1940 1960 1980 2000 2010
Cultural + Chemical + mechanical mechanical Chemical
New herbicides
• No truly new herbicides have been introduced within the last several decades
• Recent “new” products represent existing herbicide groups
• Most are introductions of generic materials by different companies and/or in different pre-mixtures
• The need for new herbicide “sites of action” is critical
New GE crop traits
• The HG 4 traits are now or soon will be commercially available in the US
• Commercial introduction will likely be slow and deliberate
• HG 27 traits are likely several years off• Are new GE crops the answer to current
herbicide resistance in weeds?
Weed “resistances”
• Weeds with evolved resistance to herbicides is the most widespread pest issue– Waterhemp (Groups 2, 4, 5, 9,14, and 27)– Horseweed/marestail (Groups 2 and 9)– Giant ragweed (Groups 2 and 9)– Palmer amaranth (Groups 2, 5, 9, 14, and
27)• Weeds have also adapted to tillage systems
and other mechanical control practices
Considerations
• Most populations are in transition – from primarily sensitive to resistant
• A majority of the fields are not “train wrecks” but rather scattered plants or pockets of weeds
• If observed and appropriate diverse management is undertaken, the problem(s) will be mitigated successfully
The key to herbicide resistance management: Many little hammers
seedbed prep tillage Cover crops
Post-plant tillage Field border management
Community-based programs to manage a “common pool” resource
• “Top down” weed management information has not been successful
• There has been success with “bottom up” programs (e.g., bollworm in cotton)
• Pilot programs are being considered in several crops
Conclusions
• Diversity of tactics is key• Innovation in technologies is nessary• Development of new herbicide sites of
action is critically important• Agriculture must take a longer-term
management perspective• Use all available tactics