1. Basics of Turfgrass Weed Management
Tim R. Murphy
Crop and Soil Sciences
The University of Georgia

2. What is a Weed? A plant out of place
A plant whose virtues have yet to be discovered
A flower in disguise

3. Is this plant a weed??? Common ragweed Poison ivy Tall fescue
decreases crop yields, allergen
Poison ivy
skin rashes, fruit consumed by birds
Tall fescue
desirable turf and forage grass
a weed in warm-season turfgrasses

4. Human beings decide which
plant is a WEED!!!!

5. Why are weeds an annual problem?
Seed and vegetative structure dormancy
Prolific seed producers
Spread of seed

7. Weed seed survival insured by:
Hard seed coat (testa)
Deep burial
After ripening mechanisms
Germination inhibitors

8. Weeds are prolific seed producers.
Seed/Plant
Broadleaf plantain 36,000
Lambsquarters >30,000
Crabgrass ,000
Texas Panicum ,000
Annual Bluegrass ,000

9. X Weeds - Nutsedge Spring 1 ft. 43,560 Fall 3,000,000 Plants Acre
4,000,000 Tubers
Acre
Acre

10. Introduced weeds Johnsongrass Common lespedeza Crabgrass
Broadleaf plantain
Water-hyacinth

11. Factors affecting seed germination
Oxygen
Light
Scarification
Temperature
Water

12. Why control weeds?

13. Control vs. Eradication
-Process of limiting a weed infestation to a
level that is economically or aesthetically
beneficial.
Eradication
-Elimination of all plants and plant parts of
weed species from an area.

14. Weeds
Compete with desirable plants for sunlight, moisture and nutrients
May exert allelopathic effects
Reduce yields or quality of harvested product

15. Why do we control weeds in turfgrasses?

16. Turfgrass Weeds Reduce quality - leaf width, shape, color differences
Reduce density
- outcompete turfgrasses, can lead to erosion
Decrease aesthetic value or utility of the turfgrass.
- difficult to mow, disrupt uniformity of playing surfaces, safety considerations, attract insects

18. Develop A Plan
Goals
Methods
Economics
Alternatives
Benefits

19. The Goal
Establish and maintain a high quality, nearly weed-free turfgrass.

20. Integrated Weed Management
Methods
Preventive
Cultural
Biological – not available in turfgrasses
Mechanical
Herbicides

21. Preventive Methods State and Federal laws Weed-free seed, sod, sprigs
Weed-free topsoil, topdressing
Clean equipment
Field borders

22. Cultural Methods Adapted turfgrasses Fertility Cultivation
Water management
Insect and disease control

23. Southeast U. S. Turfgrasses
Cool-Season
Warm-Season
Tall Fescue
Hybrid Bermudagrass
Kentucky Bluegrass
Common Bermudagrass
Perennial Ryegrass
Centipedegrass
Creeping Bentgrass
St. Augustinegrass
Zoysiagrass
Seashore Paspalum
Buffalograss

27. Soil Fertility Effects on Weeds
Low N - legumes, mosses, speedwell
High P - annual bluegrass
High N - common chickweed, ryegrass, annual bluegrass
Low soil pH - red sorrel, broomsedge

29. Weeds Favored by High Soil Moisture
Sedges - purple nutsedge, green kyllinga
Rushes
Annual bluegrass
Mosses, algae
Alligatorweed
Pennywort

30. Weeds Favored by Low Soil Moisture
Prostrate spurge
Poorjoe
Common lespedeza
Prostrate knotweed

31. Weeds Favored in Compacted Soils
Annual bluegrass
Goosegrass
Prostrate knotweed
Common lespedeza
Path rush

33. Weeds may indicate a nematode problem
spurges
Florida pusley
prostrate knotweed

34. Mechanical Methods
Mowing
Hand removal

37. Why does mowing control tall-growing weeds?
Reduces apical dominance of main stem
Basal buds initiate growth
Continued clipping depletes root carbohydrates
Prevents weed seed formation

38. Why does mowing not control low-growing weeds?
Primary growing point is located beneath the mower blade.

39. Kentucky
Bluegrass

40. Herbicides
Herbicide – a chemical used to control, suppress or kill plants.
Preemergence – applied before weed seeds germinate
Postemergence – applied to emerged weeds

41. Herbicides Turf species vary in tolerance
Weed species vary in susceptibility
Turfgrass species and weed identification is critical to herbicide selection!!!!

42. Maintain Healthy Turfgrass
Manage the roots to have good shoots
Soil testing is a must!
Utilize cultural practices (fertility, irrigation, mowing height, etc.) to improve stress tolerance
Keep mower blades sharp !
Use the best species and cultivars for your location

43. Identify the Weed Problem
READ textbooks and periodicals
Keep a diagnostic tool kit - hand lens, etc.
Know the life cycle of the pest (What temp. does a specific weed seed germinate?)
Is the weed the cause or effect of the problem?
Confirm your diagnosis

44. Weed Thresholds - ?? Site - putting green, lawn, etc.
People - expectations
Weed - population dynamics
Budget - dollars

45. Scouting Sites
Use zig-zag pattern
Make random stops

46. Scouting Sites Identify weeds and life cycle
Record observations by area
- ornamental beds
- turfgrass areas
* front lawn
* back lawn

47. Scouting Sites Record density by species Low - 1 to 10%
Medium - 11 to 20%
High - > 20%

48. When to Scout? Mid-winter months - winter weeds
Late-April to July - summer weeds
Late summer - assess summer program
Late spring - assess winter program

49. Developing a Weed Management Program
Prevent weed introduction
Properly maintain turfgrasses
Identify weeds and learn life cycle
Initiate control practices
Preventive
Cultural
Mechanical
Herbicides