Herbicide Resistant Weeds & NRCS Approach

1. Herbicide Resistant Weeds & NRCS Approach Josh Spencer Water Quality Specialist April 18, 2011 May 5, 2011 Darryl Harrington District Conservationist January 9, 2012 (All credit goes to Josh)

2. What are herbicide resistant weeds? • Weed Science Society of America definition (2001): • “The evolved capacity of a previously herbicide-susceptible weed population to withstand a herbicide and complete its life cycle when the herbicide is used at its normal rate in an agricultural situation.” • Translation: • Weed populations don’t die when labeled control amounts of known effective herbicides are applied • In NC, the most concerning problems in recent years are with previously glyphosate (Roundup) susceptible populations of horseweed, ragweed, and Palmer Amaranth

3. Herbicide Resistant Biotypes in NC • There are currently 10 different biotypes of herbicide resistant weeds confirmed in NC • First reported was Goosegrass in 1973 (Trifluralin) • Others followed—Atrazine resistant Lambsquarters (1980), resistant ryegrass, cocklebur, bluegrass • Most widespread resistant weed is Palmer Amaranth—resistance to ALS inhibitors (1995) AND glyphosate (2003). • Coincidence that glyphosate-resistant PA spread after producers began exclusive use of RR corn, soybeans, cotton?

4. Palmer Amaranth—Why Such a Problem? • Prevalence—NCSU estimates that 1/2 of all Palmer Amaranth populations in eastern NC are resistant to glyphosate, ½ are resistant to ALS inhibitors, and 1/4 are resistant to BOTH modes of action • Mode of action = the way a herbicide attacks a susceptible plant’s physiology and kills it • Because PA is now resistant to multiple herbicide MOA, only ONE non-resistant MOA remains that provides >90% control—PPO inhibitors

5. Palmer Amaranth—Why Such a Problem? • ECONOMIC—Not only resistant, but a primary plant pest in NC’s most economically important production crops (corn, cotton, soybeans) • In counties where resistant PA has been confirmed, assumption should be that ANY individual is resistant • Plant Properties—PA thrives on SE US summer heat, growing up to 2”/day during peak, and propagating massive amounts of seed

6. Palmer Amaranth—Why Such a Problem? • Growth rate and height of PA outcompetes soybeans, early corn, and cotton • Because of size, rapid proliferation, and amount of seed produced, 99% PA control can still lead to substantial crop yield losses • For remaining effective herbicides, growth stage TIMING of application is paramount for kill, but difficult because of rapid growth rate. “Half-effective” applications occurring at wrong time can harm efforts to curb resistance—PA continues to propagate seed

7. Palmer Amaranth—Conservation Agronomy Issues • Resistant Palmer Amaranth is perhaps the most important—and challenging—conservation agronomy issue faced by NRCS in the Southeast US • WHY? • Perfect ‘superweed’ for NC climate • Occurs on extensively used & economically essential NC crops—corn, cotton, soybeans • Crops that have adopted conservation tillage or ‘no-plow’ management systems • Tillage is being promoted by some as dominant control method • Threatens to undermine soil quality gains of 25 years!!

8. If herbicide resistant weeds are such a conservation problem, shouldn’t NRCS be doing something? • YES—at the national level, NRCS issued National Bulletin 450-11-2 Herbicide Resistant Best Management Practices • Promote CIGs that focus on rotating herbicide modes of action • Through EQIP, promote IPM and IPM Herbicide Resistant Weed Conservation Activity Plans (CAPs) • Promote and plan 595 Integrated Pest Management • Plan conservation systems to address crop rotations, cover crops, and conservation tillage • NRCS to partner with industries, universities, chemical companies and other technical specialists to address herbicide resistance • Issued WSSA publication BMPs for Weed Management as part of bulletin to provide employees some technical guidance

9. NC NRCS Strategy for HRWs • Conservation Planning—Field planners should discuss potential HRW issues w/producers during planning • 595 planning discussions should include dialogue about producer-selected herbicides, and importance of use of multiple herbicide modes of actionwithin each crop • Planners should provide information to producers from NC Ag Chemical Manual on herbicide brands, active ingredients, and their respective modes of action (see NC Sharepoint HRW Folder)

10. NC NRCS HRW Strategy • Conservation Planning • Planners should incorporate technical guidance and essential elements of HRW CAP in planning 328, 340, 344, and 595 • Frequent in season scouting, use of crop specific thresholds for determining herbicide use need • Use of long term rotations with non-repeating crops to minimize weed seed bank, and force herbicide rotation • Consistent, long term use of cover crops left to appropriate levels of maturity to suppress early season weeds • Consistent crop residue management to suppress weed growth • Encourage IPM systems—biological and cultural controls

11. NC NRCS HRW Strategy • Program Integration—Beginning with 2012 EQIP • Develop integrated weed management techniques to address HRW issues • Promote comprehensive approach to addressing HRW issues • Assess current EQIP practice scenarios in 328 and 340 to assess potential effectiveness as HRW plan components • Work with partners to develop new EQIP practice scenarios to address HRW concerns • Be proactive in promoting conservation-minded alternatives to tillage in HRW control strategies

12. Potential EQIP HRW-related Scenarios--2012 • Existing EQIP Scenarios • 154—IPM Herbicide Resistant Weed CAP • Comprehensive, multi-faceted planning approach • Need to get TSPs certified to write them! • 340—Cover Crop Legume/Small Grain Mixture • Heavy biomass producing cover crops mixtures left to maturity • Addition of HRW purpose in Practice Guidelines

13. Potential EQIP HRW-related Scenarios--2012 • Existing EQIP Scenarios • 328—Sod-based Rotation • Would break repetitive crops and weed seed bank • Would reduce uses of herbicides • 340—Cover Crop Crop Roller Crimper • Promote management of cover crops to late maturity level needed for effective termination by rolling • Large residue quantities to suppress early season weed growth

14. Potential EQIP HRW-related Scenarios--2012 • NEW EQIP Scenarios— • 328—Crop Rotation > 3 years • At least 3 years required between use of crops susceptible to Palmer Amaranth • Intent to curb continuous cotton, soybeans, corn ‘rotations’ • Promote overall HRW strategy essential component of crop diversity and herbicide rotation

15. 328—Crop Sequence excluding repeated G-T cotton & soybean crops • Premise is crop rotation and herbicide rotation are essential components of herbicide resistant weed management strategy • Eligibility: Producer must have grown glyphosate-tolerant soybeans OR cotton in 2011 crop growing season • This is our first attempt to address herbicide-resistance in weeds in EQIP, be patient!!

16. 328—Crop Sequence excluding repeated G-T cotton & soybean crops • Scenario requirements • G-T soybeans OR cotton is allowed once in 3-year contract period (either 2013 or 2014 crop years) • Genetically engineered cotton/soybeans that are NOT herbicide resistant (such as Bt cotton) are acceptable substitute crops (and yes, I know these are getting harder to find) • G-T corn in good production environments is allowed • Glufosinate-tolerant (Liberty Link) crops may be planted, but not the same crop in consecutive years • Producer must implement scouting plan • Selected crop rotation must meet 328 criteria!! • Must produce a ‘Positive SCI’ with the rotation

17. Potential EQIP HRW-related Scenarios--2012 • NEW EQIP scenarios • 328—Crop Rotation w/ Grain Sorghum • Substitution of grain sorghum for susceptible crop types—especially corn, cotton, and soybeans • Promote overall HRW strategy essential component of crop diversity and herbicide rotation • 328 standard requires “Positive SCI”

18. 328—Sorghum Substitute for G-T cotton & soybean crops • Purpose to disrupt continuous cycle of glyphosate-tolerant cotton and soybeans crops, and produce a marketable alternative • For FY 2012, one year practice only • Eligibility: Producer must have grown glyphosate-tolerant soybeans OR cotton in 2011 crop growing season

19. 328—Sorghum Substitute for G-T cotton & soybean crops • Scenario Requirements (meet 328 criteria!!): • During 2012 growing season, Grain Sorghum must be grown on enrolled land (only where G-T soybeans or cotton grown in 2011) • Only grow Grain Sorghum on soils that have established RYE • Planting dates, rates, and mgmt of pests should follow NCSU/NC CES recommendations • After harvest, producer must ensure no fall Palmer Amaranth emergence and seed production occurs!!

20. More Information • Where is more technical and planning guidance available? • Sharepoint HRW Folder • NC Ag Chemical Manual • WeedScience.org • NCSU specialists (Alan_York@ncsu.edu OR David_Jordan@ncsu.edu) • Stay tuned for more guidance for 2012 EQIP scenarios