PRE Weed Management Strategies

1. PRE Weed Management Strategies When Do Weeds Emerge? SUMMER ANNUAL weeds can germinate in late winter (late February – early March) and on into spring and summer if conditions are right. PRE herbicides must be applied and activated before weed emergence.

2. Smooth Crabgrass Goosegrass Summer Annual Grasses Sandbur Yellow Foxtail

3. PRE Weed Management Strategies When Do Weeds Emerge? Most PRE herbicides used in turfgrass are for smooth crabgrass and goosegrass control. Many products are available that do a good job if they are applied on time. Many in the lawn care industry apply TOO LATE!

4. PRE Weed Management Strategies When Do Weeds Emerge? Soil temperature in the upper 0.5 inch of the soil profile needed for the following germination… Smooth crabgrass 55 degrees (mid to late March) Goosegrass 60 degrees (2 to 3 weeks later) Barnyardgrass 60 degrees (2 to 3 weeks later) Foxtail species 65 degrees (3 to 4 weeks later)

5. PRE Weed Management Strategies When Do Weeds Emerge? Many in the turf industry use biological indicators as guides for applying PRE crabgrass herbicides. This can lead to problems! When dogwoods are in bloom – smooth crabgrass may already be germinating. This is too late!

6. PRE Weed Management Strategies When Do Weeds Emerge? A better biological indicator would be to apply PRE crabgrass herbicides when forsythias are blooming. These tend to begin flowering in January – February in the Raleigh area.

7. PRE Weed Management Strategies When Do Weeds Emerge? Some turf areas will warm more quickly in the spring than others. Pay attention to turf grown on sandy soils or south facing slopes. Grassy weeds will germinate sooner in these areas. Unless the herbicide label states differently…only apply herbicides to well established turfgrass!!!

8. PRE Weed Management Strategies When Do Weeds Emerge? Applying PRE crabgrass herbicides early (January or sooner) usually will not affect the length of control, because the soil microbes that will eventually break down the herbicides are not active until soil temperatures increase. PRE crabgrass herbicides are effective for approximately 200 days once microbial activity begins.

9. PRE Weed Management Strategies Herbicide Families Dinitroanilines (DNA’s) Excellent crabgrass, good goosegrass herbicides Usually inexpensive and yellow in appearance Absorbed by roots and shoots growing through treated zone Affect cell division – sensitive plants don’t survive Are root inhibitors

10. PRE Weed Management Strategies Herbicide Families Dinitroanilines (DNA’s) Tolerant turfgrasses display root stubbing or root clubbing symptoms. Do not use these herbicides on athletic fields because of this. Roots can be sheared off due to heavy traffic and death can occur.

11. Photo Taken 10-29-01 St. Augustinegrass Nontreated St. Augustinegrass Barricade 65WG Spring, 2001 Clubbed roots

12. PRE Weed Management Strategies Herbicide Families Dinitroanilines (DNA’s) Have PRE and POST activity Will control crabgrass and goosegrass in the one leaf stage if watered in immediately (are forgiving herbicides if you apply a little too late)

13. PRE Weed Management Strategies Herbicide Families Dinitroanilines (DNA’s) Benefin (Balan 2.5G) Benefin + trifluralin (Team 2G, Team Pro 0.86%) Benefin + oryzalin (XL) Prodiamine (Barricade 65WG) Pendimethalin (Pre-M, Pendulum WDG) Oryzalin (Surflan A.S.)

14. PRE Weed Management Strategies Herbicide Families Pyridines Dithiopyr (Dimension, Dimension Ultra WSP) Are not DNA herbicides but have the same mode of action (excellent crabgrass, good on goosegrass) Somewhat volatile – works better as a granular Controls crabgrass and goosegrass up to 3-4 leaf stage

15. PRE Weed Management Strategies Herbicide Families Oxadiazoles Oxadiazon (Ronstar G, Ronstar 50WSP) Absorbed by shoots only, inhibits photosynthesis Does not inhibit root growth Therefore, use this product in worn turf or where additional grow-in is desired (athletic fields)

16. PRE Weed Management Strategies Herbicide Families Oxadiazoles Oxadiazon (Ronstar G, Ronstar 50WSP) Expensive (good crabgrass and goosegrass control) Provides NO POST crabgrass or goosegrass control Apply 10-14 days prior to weedy grass germination Can use during sprigging or sodding of bermudagrass or zoysiagrass: NOT seeding

17. PRE Weed Management Strategies Herbicide Families Acetanilides Metolachlor (Pennant Liquid) Used more in ornamental beds than turf Good crabgrass, fair goosegrass control An exception: A PRE herbicide that DOES affect perennial structures (yellow nutsedge only)

18. PRE Weed Management Strategies Herbicide Families Mixtures Are combinations of herbicide families that provide excellent crabgrass and good goosegrass control Oxadiazon + benefin (Regalstar) Oxadiazon + prodiamine (Regalstar II) Oxadiazon + bensulide (Goosegrass/Crabgrass Control)

19. Crabgrass sp. and Goosegrass (Preemergence Control) Check labels for turf tolerances Many Available Products benefin (Balan) benefin + trifluralin (Team Pro) bensulide (Betasan) dithiopyr (Dimension / Ultra) oxadiazon (Ronstar G) pendimethalin (Pre-M) prodiamine (Barricade 65WG)

20. PRE Weed Management Strategies Ken. Tall Fine Per. Blue Fescue Fescue Rye. Balan T T M T Team Pro T T M T Dimension T T T T Ronstar T T NR T (Pre-M, T T T T Pendulum) Barricade T T T T Pennant NR NR NR NR Surflan NR T NR NR

21. PRE Weed Management Strategies Bahia Bermuda Centipede St. Aug Zoysia Balan T T T T T Team Pro T T T T T Dimension T T T T T Ronstar NR T NR T T (Pre-M, T T T T T Pendulum) Barricade NR T T T T Pennant T T T T T Surflan T T T T T

22. Crabgrass sp. and GoosegrassPreemergence Control Athletic Fields and High Traffic Areas • Avoid dinitroaniline herbicides and Dimension Balan, Team Pro, Pre-M, Barricade 65WG Root inhibitors (affect turfgrasses also) Heavy traffic can shear roots • Options Ronstar G

23. PRE Weed Management Strategies Split Applications When using DNA herbicides and Dimension for summer grass control, turf managers have the option of making split applications. At the proper timing, apply ½ to 2/3 the single labeled rate, then apply the remainder 8 weeks later. Do not increase the TOTAL amount.

24. PRE Weed Management Strategies Split Application Advantages In normal seasons, no differences will be observed. When environmental stresses do occur, the advantage will go to split applications. South and east of Raleigh, splits are recommended because of earlier germination and longer growing season for summer annual grasses. (200 or more growing days)

25. PRE Weed Management Strategies Split Applications Do not split oxadiazon (Ronstar) applications since it has no POST activity!!! Even if you are a little late with the initial application, apply the full rate ASAP to obtain maximum PRE control for plants that have yet to germinate.

26. PRE Weed Management Strategies PRE Grass Herbicides on Fall Established Turf Unless the label says otherwise, apply PRE grass herbicides only to well established turf. Generally, if turf was overseeded after October 15, do not use a PRE herbicide in the spring. Turf tolerance depends on root growth below the treated soil layer.

27. PRE Weed Management Strategies PRE Grass Herbicides on Fall Established Turf Balan, Surflan, Team Pro labels advise against applications until 1 growing season has passed. (Pre-M, Pendulum) can be applied after the turf has been mowed at least 4 times. The chemical barrier is thick (0.75”) and the roots have to be below this barrier to ensure tolerance.

28. PRE Weed Management Strategies PRE Grass Herbicides on Fall Established Turf Barricade can be applied after the turf has been mowed at least 2 times or 60 days after overseeding. The chemical barrier is thinner than Pre-M, Pendulum (0.25”) and the roots grow below this barrier more quickly. Barricade is safer for newly planted grass than (Pre-M, Pendulum).

29. PRE Weed Management Strategies PRE Grass Herbicides on Fertilizer Carriers If PRE grass herbicides are used on fertilizer carriers, MAKE SURE that the herbicide and fertilizer timings are compatible to your turf situation. Example: For a warm season turf, why buy a crabgrass / fertilizer material for a January – February application. The grass is still DORMANT!! The nitrogen will not be utilized.

30. Annual Sedge Common Lespedeza Summer Annual Broadleaf Weeds and Annual Sedge Spotted Spurge Prostrate Knotweed

31. PRE Weed Management Strategies Summer Annual Broadleaf Weeds and Annual Sedge Many of the PRE summer annual grass herbicides have activity on small-seeded summer annual broadleaf weeds and annual sedge. The timings are ideal for controlling many types of weeds with one product at one time if you can identify weed populations correctly.

32. PRE Common Lespedeza Control Dimension

33. PRE Spotted Spurge Control Dimension Ronstar Surflan Team Pro XL Pre-M, Pendulum Barricade

34. PRE Prostrate Knotweed Control Dimension Pre-M, Pendulum Surflan Team Pro XL Barricade

35. PRE Annual Sedge Control Ronstar

36. PRE Weed Management Strategies Isoxaben (Gallery Dry Flowable) Gallery Dry Flowable is the only TRUE PRE broadleaf herbicide labeled in turfgrasses. This herbicide has very limited activity on grass plants. All established turfgrasses (cool and warm season) are tolerant.

37. PRE Weed Management Strategies Isoxaben (Gallery Dry Flowable) Gallery Dry Flowable provides PRE control of summer annual broadleaf weeds such as spotted spurge and prostrate knotweed (late winter – early spring applications), along with many winter annual (late summer – early fall applications) and perennial broadleaf weeds germinating from seeds when properly applied.

38. PRE Weed Management Strategies When Do Weeds Emerge? WINTER ANNUAL weeds can germinate in late summer (late August – early September) and on into winter and spring if conditions are right. PRE herbicides must be applied and activated before weed emergence.

39. Weed Biology Winter Annual Weed Examples GrassesBroadleaves Annual bluegrass Chickweed species (Poa annua) Henbit Lawn burweed Speedwell species Knawel Hop clover

41. PRE Poa annua Control in Warm-Season Turf Overseeded With Perennial Ryegrass Balan 120 lb/acre Apply 6 weeks before overseeding Dimension Ultra WSP 1.25 lb/acre Apply 8 weeks before overseeding (NCSU data suggest 6 weeks before better) Target early to mid October for overseeding

42. PRE Poa annua Control in Warm and Cool-Season Turf If warm-season grasses are already overseeded, or cool-season grasses already reseeded or newly seeded, do not apply PRE poa annua herbicides Germinating seedlings will be affected!

43. PRE Poa annua Control in Established Warm and Cool-Season Turf Team Pro 100 lb/acre Pre-M, Pendulum 3.34 lb/acre Betasan, Bensumec, PreSan 12.5 lb ai/acre Barricade 65WG 0.75 lb/acre Ronstar G 100 lb/acre Along with Balan and Dimension / Ultra WSP, these products are all labeled in established tall fescue, Kentucky bluegrass, perennial ryegrass, bermudagrass, St. Augustinegrass and zoysiagrass.

44. PRE Weed Management Strategies Winter Annual Broadleaf Weeds Many of the PRE summer and winter annual grass herbicides have activity on small-seeded winter annual broadleaf weeds. The timings are ideal for controlling many types of weeds with one product at one time if you can identify weed populations correctly.

45. Common Chickweed Barricade (Pre-M, Pendulum) Surflan Team Pro, XL Henbit Barricade (Pre-M, Pendulum) Surflan Dimension, XL

46. Lawn Burweed None of the PRE grass herbicides are effective. Corn Speedwell (Pre-M, Pendulum) Dimension ***Barricade and Ronstar control some speedwell sp.

47. Knawel None of the PRE grass herbicides are effective. Hop Clover (Pre-M, Pendulum)

48. PRE Weed Management Strategies Winter Annual Broadleaf Weeds Gallery Dry Flowable provides PRE control of winter annual broadleaf weeds such as… Henbit Common chickweed Speedwell species

49. PRE and POST Weed Management Strategies for Poa annua Control Herbicide Families Amides Pronamide (Kerb WSP) Kerb WSP enters poa annuamainly by root absorption but also is absorbed through shoots.

50. PRE and POST Weed Management Strategies for Poa annua Control Kerb WSP • 2 to 3 lb/acre • Apply September 15 through February 1 • Do not overseed for 90 days • Tolerance in bermudagrass, zoysiagrass, centipedegrass and St. Augustinegrass • Product is mobile if heavy rain or irrigation!