effects of postemergence herbicides on centipedegrass seed production j. a. ferrell, t. r. murphy,...

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 u

ntr

eate

d

Clethodim

Sethoxydim

Halosulfuron

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 u

ntr

eate

d

Clethodim

Sethoxydim

Halosulfuron

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?