1. Crop Protection and Management Research Unit
Should I Stay or Should I Grow? The nutsedge dilemma in polyethylene mulch systems
Theodore M. Webster
Crop Protection and Management Research Unit
USDA-ARS, Tifton, GA

2. Low-Density Polyethylene Mulch is a Great Physical
Weed Control Barrier…

3. Low-Density Polyethylene Mulch is a Great Physical
Weed Control Barrier…
…In the Absence
of Methyl Bromide,
Mulch Will Be a
Critical Component
of Weed
Management
Systems

4. …But
Nutsedges
Will Pierce
This
Physical
Barrier
and
Interfere
With
Crop
Growth

5. … 40 Acre Watermelon Field Without Methyl Bromide TreatmentX X X

6. Hypotheses:
Polyethylene mulch will hinder nutsedge shoot growth, tuber production, and patch expansion
Purple and yellow nutsedge will be affected by mulches in a similar manner
Purple and yellow nutsedge will have similar growth habits in the absence of mulches.

7. 16 Wks
59 cm Diam.
23 cm Deep
1.25 mil
Drip Irrigation
Black Mulch
No-Mulch
Clear Mulch
Temporal Patterns of Emergence

8. Nutsedge Shoots/Pot
by mulch and species
146 15 6 2

9. Previous Studies:
Nutsedge Population With and Without Black LDPE Mulch

10. Purple Nutsedge Growing Under Black LDPE –
Minimal Shoot Penetration Through The Mulch
(shoots growing under black mulch in previous slide)
…So we evaluated nutsedge shoot numbers
trapped beneath mulch in the greenhouse study

11. Nutsedge Shoots/Pot Below Mulch
by mulch and species 73 39 14 12
58%
92%
80%
95%

12. Soil Sieved for tubers

13. Nutsedge Tubers/Pot
by mulch and species
366
188
179 47

14. How does mulch affect nutsedge patch expansion in the field?

15. There were differences due to mulch!
Black Plastic
Clear Plastic
No Plastic
Purple Nutsedge

16. Grid System Used To Quantify
Yellow Nutsedge And Purple Nutsedge (<16 WAP) Shoot Populations
12.7 cm

17. Purple Nutsedge Shoot Populations After 8 WAP
Grid System (12.7 cm X 12.7 cm) Used To Quantify
Purple Nutsedge Shoot Populations After 8 WAP
12.7 cm

18. Unable To Evaluate Purple Nutsedge In Clear Mulch:
This Is The Only Plot That Survived Establishment

19. Purple Nutsedge Shoots/Patch
3439
1548
1858
794

20. Purple Nutsedge
Non-Mulched Control
16 Weeks After Planting

21. Purple Nutsedge
Non-Mulched Control
24 Weeks After Planting

22. Purple Nutsedge
Non-Mulched Control
32 Weeks After Planting

23. Purple Nutsedge
Non-Mulched Control
60 Weeks After Planting

24. 16 WAP
24 WAP
Purple Nutsedge
Non-Mulched Control
32 WAP
60 WAP

25. Purple Nutsedge
Black LDPE Mulch
16 Weeks After Planting

26. Purple Nutsedge
Black LDPE Mulch
24 Weeks After Planting

27. Purple Nutsedge
Black LDPE Mulch
32 Weeks After Planting

28. Purple Nutsedge
Black LDPE Mulch
60 Weeks After Planting

29. 16 WAP
24 WAP
Purple Nutsedge
Black LDPE Mulch
32 WAP
60 WAP

30. 32 Weeks After Planting Purple Nutsedge Black LDPE Mulch
Non-mulched control

31. 60 Weeks After Planting Purple Nutsedge Black LDPE Mulch
Non-mulched control

32. Purple Nutsedge Patch Area
22.1
16.1
11.6
8.1

33. Clear Plastic
Black Plastic
No Plastic
Yellow Nutsedge: a different growth pattern

34. Yellow nutsedge was sensitive to cool autumn temperatures,
therefore there is no data beyond 24 WAP

35. Yellow Nutsedge Shoots/Patch
208
137
73 & 76
36 & 39

36. 177 Yellow Nutsedge Shoots
Patch Expansion:
24 Weeks of growth
from a single tuber
Patch Area: 0.18 m2
177 Yellow Nutsedge Shoots

37. Number of Yellow Nutsedge Quadrats/Patch
9.3
5.3

38. 24 WAP Non-mulched controls
Yellow nutsedge
Purple nutsedge
0.18 m2
5.5 m2
24 WAP
Non-mulched controls

39. Conclusions: Greenhouse
Non-mulched control: Relative to Purple Nutsedge, Yellow Nutsedge produced:
9x’s more shoots
7x’s more tubers
Mulches: Reduced Yellow Nutsedge
Shoot #’s by 96%
Tuber #’s by 50%
Differences in purple nutsedge shoot #’s and tuber #’s could not be detected among treatments

40. Conclusions: Field Purple Nutsedge in Black Mulch Plots:
2x’s MORE shoots at 32 and 60 WAP compared to Non-Mulched Control
2x’s MORE patch area at 32 and 60 WAP compared to the Non-Mulched Control
Yellow Nutsedge in Black Mulch Plots:
3x’s LESS shoots at 16 and 24 WAP compared to Non-Mulched Control
2x’s LESS patch size (in terms of quadrat #’s) compared to Non-Mulched Control

41. Take Home Message: Yellow Nutsedge: Purple nutsedge:
Growth SUPPRESSED by black mulch
Does not distribute itself far from the mother tuber
Confirms the predictions of a spatial model of yellow nutsedge growth: farming operations are the main cause of yellow nutsedge dispersal in the field (Schippers et al. 1993).
Purple nutsedge:
Growth PROMOTED by black mulch
Well suited to distribute itself through its environment.

42. Acknowledgements Eddie Sklany (Study Coordinator) Aaron Wise
Dustin Taylor
John Bennet
Amy Davis
Stefanie Cross
Contact Information: