Effects of Postemergence Herbicides on Centipedegrass

Seed Production

J. A. Ferrell, T. R. Murphy, W. K. Vencill

University of Georgia

Centipedegrass popularity

• Propagated via seed or sod

• Low maintenance– Slow growth– Low nitrogen requirement

• Herbicide tolerance– Sethoxydim and clethodim– Halosulfuron

Changing Needs

Traditional Emphasis

• Color• Seedhead

Suppression• Weed Control

Production Emphasis

• Seed Yield• Seed Quality• Weed Control

Digitaria sanguinalis

Cyperus esculentus

Objectives

Determine the impact of herbicide and treatment timing on:

• Seedhead suppression• Seed yield• Seed quality

Herbicide Treatments

Herbicides• Clethodim • Sethoxydim• Halosulfuron

Spray Timing• -4 WPS*• -2 WPS • 0 WPS (Late July)• 2 WPS• 4 WPS

* Weeks post seedhead emergence

Materials and Methods

• Macon County, Georgia seed farm– Greenville clay loam

• Established centipedegrass (cv. ‘TifBlair’)

• Irrigated, weed-free site• Plot size – 6’ X 20’• 3 replications

Materials and Methods

• Clethodim – 0.25 lb ai A-1 + 0.25% v/v NIS• Sethoxydim – 0.28 lb ai A-1

• Halosulfuron – 0.062 lb ai A-1 + 0.5% v/v NIS• 25 GPA, flat fan nozzles, CO2 backpack• Seedhead suppression –0 to 100 scale• 3 x 5 factorial• Analysis: herbicide within treatment timing

Seedhead Suppression

Seedhead Suppression

Timing Clethodim Sethoxydim Halosulfuron

4 WBS NS NS NS

2 WBS NS NS NS

0 WBS NS

2 WPS NS

4 WPS NS NS NS

NS – non significant

Seedhead Suppression (0 WPS)

Herbicide 2 WAT 4 WAT

2001 2002 2001 2002%

Clethodim 50 12 31 0

Sethoxydim 21 3 3 3

Seedhead Suppression (2 WPS)

Herbicide 2 WAT 4 WAT

2001 2002 2001 2002%

Clethodim 33 16 23 5

Sethoxydim 18 0 13 0

Seed Yield

•October 10, 2001

•Harvested 2 randomly selected m2 quadrants

•Seeds removed from heads with mechanical thrasher

Seed Yield

20

40

60

80

100

120

-4 -2 0 2 4

Weeks Before Seeding

% o

f unt

reat

ed

ClethodimSethoxydimHalosulfuron

Seed Germination

• Conducted by Georgia State Seed Test Lab

• Conditions:– Covered petri dish with moist paper– Temperature – 20 to 35o C– Counts – 7 and 21 days

Seed Germination

70

80

90

100

110

-4 -2 0 2 4

Weeks Before Seeding

% o

f unt

reat

ed

ClethodimSethoxydimHalosulfuron

Conclusions

• Halosulfuron does not affect centipedegrass seed yield or germination

• Apply clethodim or sethoxydim as early as possible (minimum 4 WBS)

• Once seedheads emerge, use of clethodim or sethoxydim is not advisable

Future Centipedegrass Research

• Investigate effect of clethodim and sethoxydim in salvage situations (6, 8, 10 WPS)

• Effect of other commonly used herbicides on seed yield and quality

• Develop weed management systems in seedling centipedegrass

Acknowledgements

• Valent USA

• The Turfgrass Group

• Bill Nutt - technical assistance

www.bmen.tulane.edu/~mroberts

Any Questions?