Turfgrass Weed Management II. Broadleaf Weed Control

1. Turfgrass Weed ManagementII. Broadleaf Weed Control Tim R. Murphy Crop and Soil Sciences The University of Georgia

2. Broadleaf Control • Most broadleaf control is done with postemergence herbicides. • The essential broadleaf herbicides are: • Postemergence - growth regulators and sulfonylureas • Pre and post – atrazine, simazine, metribuzin. • Pre only - Gallery

3. Growth Regulator Herbicides

4. Broadleaf Herbicides • There are many growth regulator combinations on the market. • Mixtures of broadleaf-active herbicides tend to control more weed species than each individual component herbicide.

5. Phenoxy + Dicamba Herbicides

6. Phenoxy + Dicamba Herbicides

7. Phenoxy, Dicamba, Picolinic Herbicides

8. Post Herbicide Use Guidelines • Try to avoid spraying warm-season grasses during transition. • Shade grasses are less herbicide tolerant than grasses growing in full sun. • Spray when wind speeds are less than 5 mph.

9. Post Herbicide Use Guidelines • Avoid stress conditions (> 90 F.) • Avoid spring transition on warm-seasons • Repeat applications • Do not mow 24 to 48 hours before or after application • Rainfall and irrigation effects

10. Post Herbicide Use Guidelines • Do not water for 12-24 hours. • Need a rain free period of at least 6 hours. • Avoid extreme temperatures. Apply when temperatures are between 40 and 80°F.

11. Examples of Rain-Free Periods • MSMA - 24 hours • Trimec Classic - 24 hours • Basagran T/O - 8 hours • Finale - 4 hours • Vantage - 1 hour

12. Post Herbicide Use Guidelines • Annual weed control is excellent in the seedling stage and poor as the weed matures • Perennial weeds are more susceptible in the Spring or Fall because root reserves are usually depleted and the weed has less recovery potential • Apply to actively growing weeds - the cuticle is more easily penetrated • Sprays give better control than granules.

13. Post Herbicide Use Guidelines • Repeat applications are most effective for tough perennials. • Apply during good growing conditions when adequate soil moisture is present. • Add a surfactant if called for on label.

14. Low growing winter annual fruit lawn burweed Pre or postemergence atrazine or simazine in mid-fall. Prompt and Sencor are also effective on tolerant turfgrasses. Repeat applications of 2 or 3-way 2,4-D type herbicides. The key is applying in the fall when the weeds are small

15. winter annual common chickweed

16. winter annual sticky chickweed

17. henbit Henbit winter annual

18. winter annual Purple deadnettle

19. winter annuals henbit purple deadnettle

20. winter annual hairy bittercress

21. winter annual shepherd’s purse fruit

22. annual or biennial purple cudweed

23. winter annual parsley-piert

24. seedling corn speedwell winter annual

25. Virginia buttonweed • Difficult to control. Try digging if there are only a few plants. • Repeat applications of 3-ways or 2,4-D about 4 weeks apart are needed for adequate suppression. • 2,4-D seems to have the most activity.

26. Dandelion - Perennial 2,4-D Trimec Confront Drive

27. wild violet - perennial • Triclopyr-containing formulations (Turflon, Confront) • Some think dichlorprop is better on violet. • Confront requires careful use in warm-season. Safe in fescue.

28. white clover - perennial • Confront, Lontrel and Manor are very effective. Warm-season grasses should be dormant or fully greened-up.. • Lontrel and Manor have greater turf safety than Confront. • Trimec or other 3-ways are effective. May take two applications.

29. Spotted burclover winter annual

30. Annual lespedeza Summer annual

31. Chamberbitter, niruri Brought to Georgia in ornamental container plants. Summer annual • Atrazine or simazine applied twice, 30 days apart. • Prompt also works well. • 2 or 3-way broadleaf mixtures applied 7 days apart are also effective in tolerant turfgrasses.

32. prostrate spurge - summer annual Postemergence: Manor, Sencor, Trimec Preemergence: Simazine, atrazine, Gallery

33. fireweed American burnweed (fireweed) The 2 and 3-way growth regulator herbicides and Manor. Preemergence products are not very effective or provide only short term control. summer annual

34. perennial Pennywort or dollarweed • Atrazine or simazine applied twice, 30 days apart. • Prompt also works well. Image, Drive and Manor. • 2- or 3-way broadleaf mixtures applied 7 days apart are also effective in tolerant turfgrasses.

35. Controlled by repeat applications of atrazine, 30 days apart. 2 and 3-way growth regulator herbicides. Confront is a little better than Trimec related compounds. Dichondra, rhizomatous perennial

36. perennial ground ivy

37. perennial buckhorn plantain

38. perennial 100% Control Confront 2 pts/acre Trimec 4 pts/acre blackseed plantain

39. perennial woodsorrel (Oxalis spp.)

40. Non-Target Plants • Check for restrictions on the use of herbicides around trees and shrubs. • Be very careful around vegetables and ornamentals with growth regulator herbicides. • Avoid applying dicamba and atrazine under shallow rooted ornamentals such as azalea and rhododendron.

41. Nonselective Control • Roundup Pro - Do not tank mix with Reward or Finale if you are trying to control perennials. • Rapid burndown prevents translocation of Roundup through the plant.

42. Nonselective Broadleaf Control • Roundup Pro - slow acting (7-14 days) but provides the best control of perennials. • Reward - fastest burndown, poor perennial control, poor grass control. • Finale - Almost as fast as Reward, will leave a straight edge, very good on white clover and other legumes. Not good on perennials.

43. Lack of Post Herbicide Performance • Environmental stresses • Weed growth stage • Rain/irrigation wash-off • No adjuvant • Poor spray coverage

44. Lack of Post Herbicide Performance • Wrong rate • Wrong herbicide • No follow-up application • Mowing effects