Advanced Weed Management and Growth Regulators

1. Advanced Weed Management and Growth Regulators Matt Fagerness Kansas State University

2. Topic Outline • Review of Weed Science Terminology • Rethinking Annual Grass Control • Perennial Grass Control Options • Plant Growth Regulators and Their Uses

3. Types of Weeds • Biology Breakdown: • Broadleaf (e.g. dandelion, clover) • Grass (e.g. crabgrass, bermudagrass) • Nutsedge • Life Cycle Breakdown: • Annual (winter or summer) • Perennial (hardest to control)

4. Herbicides are either: • Preemergence: kill weeds before they get started OR • Postemergence:kill existing weeds • Selective: only kill certain types of plants OR • Nonselective: kill all plants • Contact: kill only tissue they directly contact OR • Systemic: move to all tissues to kill the whole plant

5. Pre- vs. Postemergence Herbicides • Preemergence herbicides, applied prior to when annual weeds germinate, form a barrier through which weeds can not pass. They do not prevent germination!! • Postemergence herbicides are absorbed by roots or leaves of existing weeds and are then moved to the part of the plant where they do their dirty work.

6. Selective vs. Nonselective Herbicides • Selective herbicides target certain types of plants so we select herbicides which target our weeds but not our turf (e.g. 2,4-D, MCPP, dicamba) • Nonselective herbicides are not picky about which plants they kill so we need to avoid them or use them with caution to prevent turf damage (e.g. most preemergence herbicides, Roundup, diquat)

7. Contact vs. Systemic HerbicidesPostemergence • Contact herbicides (e.g. diquat, bentazon) only kill plant tissues they directly encounter (less than ideal for perennial weeds) • Systemic herbicides translocate (move) up from roots or down from leaves to target sensitive tissues in the plant (e.g. “Roundup kills the root”)

8. Topic Outline • Review of Weed Science Terminology • Rethinking Annual Grass Control • Perennial Grass Control Options • Plant Growth Regulators and Their Uses

9. Current RecommendationsPreemergence Herbicides • Apply before weeds germinate [late summer (WA), early spring (SA)] • Before April 15 for crabgrass and goosegrass • Before April 1 with Barricade (takes longer to activate) • Use Dimension if application is late (only preemergence product with any postemergence activity) • Split applications 8 weeks apart may be necessary to cover germination window • Tupersan for winter annual weed control (proximity to fall seeding/renovation)

10. When PRE Herbicide Strategies Fail • Timing, timing, timing!! • #1 cause of failure for preemergence applications • Crabgrass germinates when soil temp.’s reach 55 F, goosegrass closer to 60 F. • Warm temperatures in late Feb./early Mar. 2000 • Is it the fault of the applicator or a loophole in current recommendations?

11. Solutions for Early Germinating Summer Annual Weeds • Apply at first sight of conditions conducive to crabgrass/goosegrass germination • Open to interpretation, poor consistency, hard to predict, etc. • Apply PRE herbicides in fall to catch early germinators • Good for PRE herbicides with good residual activity • Options for commercial and homeowner turf

12. Fall PRE Herbicide Efficacy on Crabgrass (1995) *Data collected at Rocky Ford Turfgrass Research Center ** All rates in lb. a.i./acre

13. Solutions for Early Germinating Summer Annual Weeds • Postemergence control of crabgrass/goosegrass • Commercial products available for use in our major turfgrass species • **Fewer products (e.g. Trimec Plus w. MSMA) available for selective use in cool-season home lawns

14. Postemergence Crabgrass Control in Bermudagrass * All herbicides applied at label recommended rates 7-1-99. *Data collected 8-19-99, courtesy of F.H. Yelverton, NC State University

15. Current/Future Research at KSU • Split fall/spring applications of PRE herbicides for optimum summer annual weed control • Crabgrass and goosegrass • Commercial formulations + fertilizer carriers • Residual herbicides (Barricade, pendimethalin) • DNA, Dimension split applications (fall/spring) for proper rotation of herbicide mode of action

16. Topic Outline • Review of Weed Science Terminology • Rethinking Annual Grass Control • Perennial Grass Control Options • Plant Growth Regulators and Their Uses

17. Problematic Perennial Grassy Weeds • Bermudagrass (love it or hate it) • Rhizomes and stolons • Orchardgrass • Bunch type but tillers aggressively, produces seed, and has a strong, perennial root system

18. Control of Perennial Grassy WeedsOption A – Mechanical Removal • Laborious and often disruptive • gaps where orchardgrass or bermuda patches used to be • Not always reliable • spreading nature of bermuda is such that physical removal usually does not eradicate all plant material

19. Control of Perennial Grassy WeedsOption B - Nonselective • Always an option but not always practical • Available products: • Roundup (glyphosate) • Finale (glufosinate) • Reward (diquat) • Vantage (sethoxydim)

20. Nonselective Bermuda Control *Data collected at Rocky Ford Turfgrass Research Center, Fall 1996

21. Control of Perennial Grassy WeedsOption C - Selective • Fewer products but the most desirable option • Bermudagrass only (no known options for orchardgrass) • Available products: • Acclaim Extra (fenoxaprop) w. Turflon Ester (triclopyr) • Fusilade II (fluazifop)

22. Selective Bermuda Control in Zoysia Note: Acclaim did not discolor tall fescue while Fusilade only discolored tall fescue 18% in a similar study. *Data collected at Rocky Ford Turfgrass Research Center, Fall 1996

23. Topic Outline • Review of Weed Science Terminology • Rethinking Annual Grass Control • Perennial Grass Control Options • Plant Growth Regulators and Their Uses

24. What Are Plant Growth Regulators? • Natural or synthetic substances which alter (they can promote or suppress) normal plant growth • Examples: • Biostimulants • 2,4-D and similar herbicides • **Commercial growth inhibitors (suppress growth)

25. Commercial PGRsTwo Main Categories • Type I: • Inhibit cell division (more severe mode of action) • Used for seedhead suppression or for growth suppression where quality is not a concern • Examples: Embark, Royal Slo-Gro or Retard • Type II: • Inhibit hormone production (benign mode of action) • Used more in fine turf • New uses for weed control • Examples: Turf Enhancer, Primo, Proxy, Cutless

26. Commercial PGRsA Third Category • Some herbicides (e.g. Plateau, Roundup) can be excellent regulators of growth when applied at sublethal rates • Applications usually confined to industrial or roadside turf and directed at suppressing seedheads

27. Use of PGRs to Control Poa on Creeping Bentgrass Greens *All PGRs applied twice in fall and twice in spring *Data collected 4-30-99, courtesy of F.H. Yelverton, NC State University

28. Future Directions in PGR Research • Investigating PGR suppression of Poa trivialis • PGRs for growth reduction in home lawns?? • PGRs to extend bermudagrass quality into fall on bermuda football fields • PGRs to facilitate bermuda field establishment

29. Bermuda Quality Extension Into Fall • Recent research has shown delayed fall dormancy following summer treatment of bermudagrass with TE (Primo). This type of effect was not found to reduce cold tolerance.

30. Fall Bermuda Shoot Density a a a a a a b bc ab b c b

31. Future Directions in PGR Research • Investigating PGR suppression of Poa trivialis • PGRs for growth reduction in home lawns?? • PGRs to extend bermudagrass quality into fall on bermuda football fields • PGRs to facilitate bermuda field establishment

32. Bermuda Cover 11 Weeks After Sprigging Sod Farm: Low maintenance Field Center: High maintenance

33. Bermuda Cover 11 Weeks After Sprigging (NC) PB=paclobutrazol EP=ethephon

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