Herbicide resistance. problem? Micheal D. K. Owen. Ames, IA USA

Transcription

1 A National Summit on Strategies to Manage Herbicide-Resistant Weeds Herbicide resistance in weeds: What is the nature of the problem? Micheal D. K. Owen Iowa State University Ames, IA USA edu May 10, 2012

2 Introduction Weeds represent the most important pest complex impacting global food security More food is lost due to weeds than all other pest complexes combined More herbicides are used globally than all other pesticides combined Pest resistances to pesticides id occurs in all pest complexes Strategies for managing resistance are pest complex specific The refuge tactic used for insects will not work for weeds

3 Introduction Herbicide resistance is not a new problem Concern for herbicide-resistant resistant weeds predates glyphosate by more than 50 years The USA has a long history of herbicide- resistant weeds Triazine resistance and ALS resistance are most common Globally, resistance has evolved for all herbicide MOAs in 208 weed species represented by 382 weed biotypes (and counting!)* * com Accessed 25 April 2012

4 Herbicide-resistant weeds: What is the nature of the problem? The evolution of herbicide resistance is not a herbicide problem The evolution of herbicide resistance is not a GE crop trait problem The evolution of herbicide resistance is a behavioral problem

5 Stewardship programs and practices: Crop management Production of crops has simplified with regard to the diversity of production practices and tactics used We have excelled in creating an economically profitable agro-ecosystem but one that favors only a few ecologically adapted pest species We have essentially selected for the pests that are best adapted to the crop production systems we created Darwinian Evolution in fast-forward

6 Evolution of row crop weed management Cultural + Chemical + mechanical mechanical Chemical

7 Grower response to a simple question in 2005: Do you believe you have herbicide-resistant weeds?

8 Causes of herbicide resistance Herbicides do not cause weeds to evolve resistance per se How herbicides are used causes weeds to evolve resistance (e.g. management) Factors to consider Frequency of the resistance trait in weeds Effectiveness of the herbicide Management strategies Others (e.g. herbicide marketing)

9 All herbicides are at risk! Herbicide Group 1 HRAC Group Total species 2 ALS B 121 PS II C1 69 ACCase A 42 Auxins O 29 Bipyridiliums D 25 Ureas and C2 22 amides Glycines G 23 DNA K1 11 Other 3 various 39 Total number of HR biotypes accessed 23 April herbicide groups with <10 species

10 An important example: Herbicide resistance mechanisms in waterhemp Family Herbicides Mechanism Triazines Atrazine, metribuzin Altered target site, Enhanced metabolism ALS inhibitors Pursuit, Classic Altered target site PPO inhibitors Blazer, Cobra, Reflex Altered target site Glyphosate Roundup Target site amplification, perhaps others HPPD inhibitors Callisto, Laudis, Unknown (metabolism?) Impact Growth regulators 2,4-D,, dicamba Unknown, altered porter

11 Soybean in a common waterhemp field

12 Strategies to manage herbicide resistance Clearly simplicity and convenience are not working Current strategies include: Multiple mechanisms of action Rotation ti of mechanism of action These strategies can be effective but will inevitably fail if they are all that is done

13 What does it all mean (according to me)? It is obvious that agriculture generally is not widely responding to the message The evolution of herbicide resistance is an inevitable consequence of fherbicide id use There is a disconnect between research and marketing different messages and perspectives Can/should the problem be regulated? Perhaps Can/should the problem be managed? YES! Stewardship must be considered every year

14 One perspective* Growers say they are taking allthe necessary actions to prevent weed resistance, but do not have the same optimism about their neighbors' efforts, according to a recent survey of 2011 Commodity Classic attendees. Sponsored by DuPont Crop Protection, the survey polled 150 thought leader growers during the conference in early March. *

15 Giant ragweed harvest"* *Courtesy of Bill Johnson, Purdue

16 Questions?