How Herbicides Work and How to Manage for Resistance. Harry Quicke Stewardship and Development Manager, VM Bayer CropScience

Transcription

1 How Herbicides Work and How to Manage for Resistance Harry Quicke Stewardship and Development Manager, VM Bayer CropScience

2 Topics 1. How herbicides work 2. Current state of herbicide resistance 3. Current state of herbicide discovery 4. Rights-of-way as vectors for spread of resistant weeds 5. How herbicide resistance happens 6. Principles of resistance management

3 How Herbicides Function The herbicide molecule reaches the site of action Here it inhibits one step within a biochemical pathway This results in death of the weed Generally, many processes must occur before the herbicide reaches the site of action

4 Many processes must occur before the herbicide reaches the site of action The sum of individual processes determines overall activity

5 Herbicide Movement to the Target Root pathway Herbicide enters via root Upward movement via xylem Driven by transpiration Foliar pathway Herbicide enters via leaves Translocation via the phloem Driven by photosynthesis

6 Herbicide Movement to the Target Systemic versus Contact Systemic herbicides Translocated in foliar path Uptake is critical Contact herbicides Not translocated out of leaf Coverage is critical

7 Herbicide Binding Each plant cell is multi-site chemical factory Thousands of biochemical reactions are carried out simultaneously Inhibition of a single step in a biochemical pathway can kill the cell Most herbicides are designed to inhibit one step Some herbicides inhibit complex processes Nucleus DNA Cell wall Structure Vacuole Waste, storage Mitochondria Energy center Chloroplast Photosynthesis Amino acid synthesis

8 Herbicide Binding - The Lock and Key Analogy Herbicide molecule Binding site Target enzyme Normal function Target enzyme Target + herbicide bound Non-functional A biochemical process is stopped

9 Herbicide Binding Stops Normal Function Cellular precursors Cellular products Cellular precursors No products Target enzyme Target enzyme Unbound target Normal function Bound target Non-functional

10 The success story The success of Roundup Ready system was unprecedented in agricultural history but nature struck back Eventually resulted in massive development of resistance dose rate x 2 x 4 x 8 x This also led to changes in the agricultural chemical industry 2008

11 Glyphosate-resistant Amaranths in the USA Palmer amaranth Millington, TN 2009 Palmer amaranth Marianna, AR Waterhemp Moberly, MO 2011 Multiple-resistant waterhemp DeSoto, IL 2009 Problems are not just found in South growing in Midwest & West

12 Glyphosate resistant Palmer amaranth Macon County, GA 2009 This is how bad it can get Dr. Stanley Culpepper, University of Georgia Even this is not good enough control This is what we are looking for zero Absence of diversity in weed control program led to problems

13 Glyphosate resistant waterhemp Fernald, IA 2012 Liberty Link / Liberty vs. Roundup Ready / Roundup : RtR Site

14 Glyphosate resistant kochia Rugby, ND 2012 Also resistant to fluroxypyr (and ALS)

15 Multiple resistance Missouri, 2011 Waterhemp populations with resistance to multiple MoAs (ALS, PPO, Glycine)

16 Documented Weed Resistance - Global 471 unique cases (species x site of action) 250 species 145 dicots 105 monocots Weeds have evolved resistance to 160 different herbicides Weeds have evolved resistance to 23 of 26 known herbicide sites of action Heap, I. The International Survey of Herbicide Resistant Weeds. Online. Internet. Sunday, October 2, Available

17 International Survey of Herbicide-Resistant Weeds WSSA CODES Graphs in this PowerPoint were made from data accessed from the survey website at on February 7 th, The Site of Action codes used in this slide set are from the Weed Science Society of America (WSSA). Another version for HRAC codes can be downloaded from the website. Ian Heap IanHeap@weedscience.org

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23 Kochia Lambsquarter Pigweed, Palmer Mustards Rigid Ryegrass Barnyardgrass Italian Ryegrass Annual Bluegrass Johnsongrass Marestail Thistles Prickly Lettuce

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26 Herbicide active ingredient launches Source: Phillips McDougall database

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29 The Herbicide Tool Box 292 herbicides, 21 MoA Diversity of compounds and Mechanisms of Action. Why worry?

30 World Herbicide Market by MOA Six MoA groups = 77% of market

31 US Pipelines

32 Railroad Network

33 Electric and gas transmission rights of way cover 12 million acres in US

34 U.S. Freight Rail Network 140,000 miles of total track National Highway System 160,000 miles of total roadside

35 Consequence of basic evolutionary process Resistant individuals are present within weed populations At very low initial frequency Any trait that allows an individual to survive will be selected

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37 Herbicide Resistance Ability to survive and reproduce following exposure to a dose normally lethal to the wild type May be naturally occurring May be induced by genetic engineering May be selected from variants produced by tissue culture or mutagenesis Herbicide Tolerance Inherent ability to survive and reproduce after herbicide treatment No genetic manipulation or selection used to make the plant tolerant The plant is naturally tolerant

38 Herbicides do NOT cause resistance Lack of treatment diversity promotes resistant weeds Enhanced by repetitive and continuous use Some resistance mechanisms decrease the fitness In this case, stopping herbicide application can select resistant plants out of a population

39 Mechanism of action The site in a plant with which a herbicide interacts Also called Site of Action Mode of Action The sequence of events that cause death

40 Herbicide fits into target Inhibits enzyme Controls weed Herbicide Target enzyme Sensitive Population

41 Herbicide does not fit into target Does not controls weed Herbicide Altered site of action Target enzyme Target Site Resistance Selected more by high rates Specific to one Mechanism of Action

42 Herbicide structure altered by degradation process Does not control weed Herbicide Altered structure Target enzyme Metabolic Resistance Selected by low rates Not specific to one Mechanism of Action

43 Herbicide fits into target Too much enzyme present Weed not controlled Higher enzyme level Herbicide Target enzyme Increased Gene Copy Number

44 Sensitive Population Target Site Resistance: Selected more by high rates Specifc to one MoA Metabolic Resistance: Selected by low rates Not specifc to one MoA Increased Gene Copy Number

45 Target-site mutation Enhanced metabolism Increased gene copy number Differential uptake Differential redistribution Sequestration Delayed germination Rapid necrosis / defoliation Most Common Weeds are constantly evolving new mechanisms of herbicide resistance

46 In Asian rice fields, weeds were hand pulled Hand pulled weeds looked different from rice Watergrass biotypes that looked similar to rice were missed These biotypes eventually became dominant

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48 What is Observed in Field

49 Once there, it takes a long time to dissipate Managers think resistance will dissipate in a few years

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51 Use tank mixtures Tank mix multiple modes of action Resistance is delayed more by tank-mixtures than by rotating modes of action between years Use sequential treatments Pre-emergence, followed by post-emergence with different modes of action Don t cut rates Control escapes Apply at recommended weed size Diversity is the key to disrupting the life cycle of weeds

52 Trade Name Active Ingredient Mode of Action Esplanade indaziflam CBI Plateau / Panoramic imazapic ALS inhibitor Arsenal imazapyr ALS inhibitor Matrix rimsulfuron ALS inhibitor Oust Extra suflometuron + metsulfuron ALS inhibitor Oust sulfometuron ALS inhibitor Landmark sulfometuron + chlorsulfuron ALS inhibitor Method aminocyclopyrachlor Synthetic auxin Milestone aminopyralid Synthetic auxin Tordon K picloram Synthetic auxin Opensite aminopyralid + metsulfuron (MSM) Synthetic auxin + ALS Viewpoint aminocyclopyrachlor + imazapyr + MSM Synthetic auxin + ALS Streamline aminocyclopyrachlor +MSM Synthetic auxin + ALS Perspective aminocylopyracholor + chlorsulfuron Synthetic auxin + ALS Pendulum EC/AquaCap pendimethalin Dinitroanaline Endurance prodiamine Dinitroanaline Frequency topramazone HPPD inhibitor Hyvar bromacil Photosynthetic inhibitor - PSII Karmex diuron Photosynthetic inhibitor - PSII Krovar diuron+bromacil Photosynthetic inhibitor - PSII Spike tebuthiuron Photosynthetic inhibitor - PSII Piper flumioxazin + pyroxasulfone PPO + cell division inhib. Payload flumioxazin PPO inhibitor Portfolio sulfentrazone PPO inhibitor Cleantraxx penoxsulam + oxyfluorfen ALS inhibitor + PPO

53 1. ALS inhibitors 2. Synthetic auxins 3. Dinitroanalines 4. HPPD inhibitors 5. PSII inhibitors 6. PPO inhibitors 7. Cellulose bisynthesis inhibitors

54 Synthetic auxins (Group 4) Method Milestone Garlon ALS inhibitors (Group 2) Imazapyr Escort Telar Oust Esplanade (Cellulose biosynthesis inhibitor) Diversity between groups Not brands within a group

55 Esplanade is an important tool for managing herbicide resistance No reported cases of herbicide resistance to CBI s worldwide Probability for single-point mutations conferring resistance to Esplanade appears to be very low BUT The potential for herbicide resistance must always be anticipated and respected Esplanade should be part of an integrated weed management strategy which includes: Diverse herbicide program utilizing more than one effective mode-ofaction for a particular weed species either in tank-mix or sequential application. Zero Tolerance Control weed escapes prior to setting seed using a postemergence herbicide program or mechanical removal.

56 1 MOA 4 MOA Accord XRT II Perspective + Esplanade + Accord XRT II Synthetic auxin + ALS + CBI + EPSPS

57 Summary Rights of way and bareground sites are vectors for the spread of resistance Lack of herbicide diversity promotes resistant weeds Tank mix multiple mechanisms of action Diversify between mechanisms of action, not between brands within a mechanism of action group

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