FINAL REPORT
SUSTAINABILITY IN TURFGRASS SYSTEMS:
ASSESSMENT OF NEW STRATEGIES FOR WEED CONTROL AND SPECIES
SELECTION
Principal Directors:
Travis Gannon
(Assistant Professor, NC State University, Department of Crop Science)
Danesha Seth-Carley
(Coordinator of Sustainability Programs, College of Agriculture and Life Sciences)
Fred Yelverton
(Professor, NC State University, Department of Crop Science)
Thomas Rufty
(Professor, NC State University, Department of Crop Science)
Project type: Seed
This project does not primarily address a 2013 Special Priority
Turfgrasses are one of the most important agricultural commodities in the
southeast United States. By the traditional measures of economic impact and total
acreage, they rank among the leading agricultural crops in most southeastern states. As
the base for recreational facilities like parks, athletic fields, and home lawn play spaces,
turfgrasses provide the infrastructure for increasing physical activity - now imperative
with the national initiatives to control obesity.
Although weed, pathogen, and insect management in turfgrass systems leads to
frequent pesticide applications, herbicides are the most common intervention. Some of
the pesticides that are used have been linked with harmful effects on human health and
water quality. Turfgrasses are typically a monoculture that must grow aggressively to
maintain density and durability under intense physical activity. The intensive
management in these systems, as in traditional agricultural systems, presents risks
associated with chemical application.
In this research, we investigated the first phase of a comprehensive research
program to develop new integrated pest management (IPM) strategies for pest control in
turfgrass systems that will minimize or eliminate the health and environmental problems
posed by pesticide use. The initial focus is developing strategies that reduce synthetic
pesticide inputs for weed management, one of the most difficult challenges for an
effective IPM program in turfgrass systems.
The effectiveness of non-pesticide weed-control treatments were evaluated alone
and compared to synthetic herbicides. The focus was on new, recently registered
herbicides that have improved modes of action and very low use rate herbicides. The
effect of turfgrass mowing heights was also evaluated as well as comparing native and
non-native turfgrass species. Field plots were located at the Lake Wheeler Turfgrass Field
Laboratory, and the Horticultural Field Laboratory at N.C. State. These research facilities
are located in the ‘transition zone’ for turfgrasses, so they are well situated for extensive
turfgrass research.
Because weed control is the most difficult hurdle for an effective IPM program,
results gathered in this research will provide the base information substantiating that
alternative approaches to pest control are workable in turfgrass systems. Further, these
data will be utilized to accomplish the goals of the National IPM Roadmap by offering
new IPM strategies to turf managers and other stakeholders and help to increase adoption
rates of these strategies.
Objectives
1. Evaluate the efficacy of alternative “pesticide-free” and reduced pesticide input
strategies for weed control in recreational turfgrass systems.
Treatments with partial and total replacement of synthetic pesticides will be
compared to traditional, widely-used synthetic herbicides that may pose a threat to
human health and the environment. The treatment comparisons will include new
synthetic herbicides with lower application rates that may pose a lower risk (Table
1). The research will be conducted with warm- and cool-season grasses commonly
grown in the Southeast and will include conditions simulating highly managed and
residential turfgrass systems.
2. Determine the effect of turfgrass mowing height on weed populations and
herbicide efficacy to determine if reduced application rates may provide acceptable
results.
Turfgrass will be managed at different mowing heights to determine if reduced
herbicide rates may be utilized under varying mowing heights without compromising
weed control. Previous research suggests weed incidence may be affected by
turfgrass mowing height in the southeastern U.S. These mowing heights and weed
infestation incidence will be tested against other published recommendations for
both cool- and warm-season turfgrasses.
3. Evaluate various native turfgrass species for survivability and performance in the
transition zone with reduced inputs. Alternative pest management programs
(organic and conventional) will also be evaluated.
Native turfgrass species will be established and evaluated under reduced or minimal
inputs to determine if they represent a viable option in the transition zone. These
species will be compared to commonly used non-native species.
Procedures
Objective 1. Plots will be located in established turf-type tall fescue (Festuca
arundinacea) or bermudagrass (Cynodon dactylon) at the Lake Wheeler Turfgrass
Research Laboratory. Plots will be established in turfgrass areas with natural crabgrass
(Digitaria spp.) or goosegrass (Eleusine indica) infestations simulating home lawns,
athletic fields, parks, golf courses, etc.
Evaluated treatments will include: traditional synthetic preemergence herbicides
pendimethalin and prodiamine [0.75 – 3 lb active ingredient (ai) per acre], a recentlyregistered preemergence herbicide, indaziflam, (0.1 lb ai per acre), a pesticide-free
product mix, and combinations of the pesticide-free mix with the new synthetic herbicide
at lowered rates. As indicated, the traditional synthetic herbicides are applied at higher
use rates (greater ai), and their efficacy has not been compared to the recently-registered
herbicide which has a lower use rate, and certainly not when the new herbicide is applied
at lower than labeled rates. The pesticide-free weed control mix will include corn gluten
and recaptured carbon dioxide applied in spot sprays. The recaptured carbon dioxide
component is a new method of organic weed control that utilizes applications of liquid
carbon dioxide that quickly converts to frost when expelled.
Treatment list:
1. Nontreated
2. Organic/alternative approach
a. Corn gluten
b. Recaptured liquid carbon dioxide
3. Organic approach supplemented with synthetic herbicide
a. Corn gluten + indaziflam (0.25 X rate)
b. Corn gluten + indaziflam (0.5 X rate)
c. Corn gluten + indaziflam (1 X rate)
4. Traditional synthetic herbicides – higher labeled use rate
a. Prodiamine
b. Pendimethalin
5. Recently-registered herbicides – lower labeled use rate
Indaziflam
Objective 2. Research will be initiated in established turf-type tall fescue (Festuca
arundinacea) or bermudagrass (Cynodon dactylon) at the Lake Wheeler Turfgrass
Research Laboratory. Plots will be established in turfgrass areas with natural weed
infestations to evaluate preemergence herbicide efficacy as affected by turfgrass mowing
height.
Evaluated treatments will include: traditional synthetic preemergence herbicides
dithiopyr, oxadiazon, pendimethalin and prodiamine [0.5 – 3 lb active ingredient (ai) per
acre] as well as a recently-registered preemergence herbicide, indaziflam, (0.1 lb ai per
acre). Each herbicide will be evaluated under at least two mowing heights to compare
efficacy as affected by mowing height which has not previously been conducted.
Treatment levels:
1. Synthetic herbicides
a. Dithiopyr (0.25 or 0.5 lb ai)
b. Indaziflam (0.05 or 0.1 lb ai)
c. Oxadiazon (1.5 or 3 lb ai)
d. Pendimethalin (1.5 or 3 lb ai)
e. Prodiamine (0.5 or 1 lb ai)
f. Nontreated
2. Mowing heights
a. 0.5”
b. 2”
Objective 3. Research will be initiated at the Horticultural Field Laboratory in Raleigh,
NC. There will be four replications of plots measuring approximately 20’x 40’ (each
turfgrass species will be 10’ x 20’ with a 1’ space separating each).
Treatment levels:
1. Native turfgrass species
a. Bouteloua gracilis (sideoats grama)
b. Danthonia spicata (poverty oatgrass)
2. Non-native turfgrass species
a. Cynodon dactylon (bermudagrass)
b. Festuca arundinacea (tall fescue)
3. Pest management programs
a. Bayer Natria Grass and Weed Killer and Bayer Natria Disease Control
b. Earthworm Castings from Circle Organics
Scott’s synthetic fertilizer and pesticide products per recommended program
During June, 2013, tall fescue and bermudagrass were planted in the form of sod,
and side oats grama and poverty oatgrass were planted as plugs 6” apart. Each plot area is
approximately 25 sq ft. Treatments are as follows:
 Scott’s Annual Lawn Care Program
o Four step program including weed and feed applications in spring,
early summer, late summer/early fall, and late fall; rates applied
per label specifications
 Circle Organics Lawn Care Program
o Four step program including initial inoculation of mycorrhizae at
planting, monthly applications of Eco-Boost, and bi-monthly
applications of organic turf fertilizer; rates applied per label
specifications and manufacturer recommendations
 Natria Herbicide Program
o Monthly applications of post-emergent contact herbicide for weeds
in the turfgrasses; rates applied per label specifications
 Espoma Annual Lawn Care Program
o Weed and feed program including applications of organic fertilizer
in spring, summer, and fall with monthly post-emergent contact
herbicide applications; rates applied per label specifications
Plots are mowed weekly during the growing season. Visual observations are made
weekly. Chlorophyll, brightness, and weed count data are collected monthly during the
growing season. Irrigation is applied at 1” per week for half the plots and natural
precipitation for the other half. If there is not any rainfall recorded, then no more than ¼”
additional irrigation is applied to the turfgrasses receiving natural precipitation.
Results and Discussion
In established bermudagrass turf, treatments that did not include a synthetic
herbicide did not provide acceptable weed control through 16 weeks after treatment while
label rates of commercially available products provided complete crabgrass control
(Tables 1, 2, and 3). Full label application rates of Barricade (prodiamine) and
Dimension (dithiopyr) provided acceptable crabgrass control regardless of tall fescue
mowing height (Table 4). However, Pendulum (pendimethalin) provided greater control
at the higher mowing height. Utilizing split applications, Barricade provided complete
control regardless of the mowing height; however, split applications of Dimension and
Pendulum provided less control at the lower mowing height. Full label application rates
of Barricade (prodiamine), Dimension (dithiopyr), Specticle (indaziflam), Ronstar
(oxadiazon), and Echelon (prodiamine + sulfentrazone) provided acceptable crabgrass
control in established bermudagrass (Table 5).
The grasses that were planted by plugs, poverty oatgrass and side oats grama, are
demonstrating high weed counts due to more soil being exposed. The grasses planted by
sod, tall fescue and bermudagrass, are showing little to no weeds, usually no more than
three or four weeds if any are present. The poverty oatgrass has not shown capacity to
outcompete weeds whereas the side oats grama has shown the ability to outcompete
weeds, doubling in size throughout the 2013 growing season. The poverty oatgrass is
extremely slow to establish and very slow in increasing in size. The poverty oatgrass has
shown a tendency to favor drier soils, which was listed as one of its characteristics in
cultural requirements. After initial planting, all the grasses received irrigation twice
weekly, during which time the poverty oatgrass became yellowed and did not show signs
of growth. When the irrigation was reduced for the half receiving natural precipitation,
the poverty oatgrass began developing a greener color and signs of growth. As seen in
Figures 1 and 2, chlorophyll readings varied in irrigated and nonirrigated turfgrass
species with alternative turfgrass species having significantly lower readings compared to
current turfgrass species. Further, no consistent differences were observed among
evaluated species managed under different management plans (Figures 3 through 6).
Results from this research will allow future investigations to elucidate the effectiveness
of various pest management plans and alternative species integrated towards the national
integrated pest management roadmap.
Table 1. The effect of weed management practice on crabgrass control in
bermudagrass turf (2013).
8
12
16
WAIT
WAIT
WAIT
________ % crabgrass cover
Treatment
reduction ________
CO2 spot apps.
13
0
0
Corn Gluten (20 lb / M)
23
17
13
CO2 spot apps. + Corn Gluten (20 lb / M)
18
17
4
CO2 spot apps. + Corn Gluten (20 lb / M) + Specticle
100
100
97
20 WP (3.75 oz / A)
CO2 spot apps. + Corn Gluten (20 lb / M) + Specticle
82
97
95
20 WP (1.88 oz / A)
CO2 spot apps. + Corn Gluten (20 lb / M) + Specticle
30
25
35
20 WP (0.94 oz / A)
Specticle 20 WP (3.75 oz / A)
100
100
100
Barricade 4 FL (0.75 lb ai / A)
100
100
100
Pendulum AquaCap 3.8 FL (3 lb ai / A)
100
84
95
Ronstar 3.17 SC (3 lb ai / A)
100
100
100
LSD0.05
33
33
19
Corn gluten treatments applied 06/22/13. CO2 spot treatments applied 07/17/13,
08/01/13, 08/15/13 and 09/16/13.
Table 2. The effect of herbicide and application rate on preemergent herbicide
efficacy 8 WAIT (2013)
App
Barricade
Dimension
Pendulum
rate
_____________________________________ % crabgrass cover reduction __________________________________
1X
100
83
90
0.5X fb
99
87
89
0.5X
0.5X
98
55
45
______________________________________________________
_________________________________________________________
LSD0.05
10
0.5X and 1X treatments applied 06/15/13. 0.5X sequential applied 07/14/13.
Table 3. The effect of herbicide and application rate on preemergent efficacy
12 WAIT (2013)
App
Barricade
Dimension
Pendulum
rate
___________________________________ % crabgrass cover reduction _____________________________________
1X
99
63
75
0.5X fb
100
78
87
0.5X
0.5X
97
43
25
______________________________________________________
_________________________________________________________
LSD0.05
12
0.5X and 1X treatments applied 06/15/13. 0.5X sequential applied 07/14/13.
Table 4. The effect of tall fescue mowing height, herbicide, and application
rate on PRE efficacy 16 WAIT (2013)
Barricade
Dimension
Pendulum
App
1.75"
3.5"
1.75"
3.5"
1.75"
3.5"
rate
___________________________________ % crabgrass cover reduction ___________________________________
1X
100
99
56
63
44
79
0.5X fb
100
100
69
95
72
93
0.5X
0.5X
96
98
22
35
5
51
___________________________________________________________
______________________________________________________
LSD0.05
12
0.5X and 1X treatments applied 06/15/13. 0.5X sequential applied 07/14/13.
Table 5. The effect of herbicide treatment on crabgrass control in
bermudagrass turf (2013).
Treatment
Specticle FLO (0.25 oz ai / A)
Specticle FLO (0.375 oz ai / A)
Specticle FLO (0.75 oz ai / A)
Barricade 65 WG (0.75 lb ai / A)
Barricade 65 WG (1.5 lb ai / A)
Pendulum AquaCap 3.8 SC (1.5 lb ai /
A)
Pendulum AquaCap 3.8 SC (3 lb ai / A)
Dimension 2 EW (0.25 lb ai / A)
Dimension 2 EW (0.5 lb ai / A)
Ronstar 2 G (2 lb ai / A)
Ronstar 2 G (4 lb ai / A)
Echelon 4 SC (0.57 lb ai / A)
Echelon 4 SC (1.14 lb ai / A)
LSD0.05
Treatments applied 06/22/13.
8 WAIT
12 WAIT
16 WAIT
% crabgrass cover reduction ________
91
84
82
95
87
81
100
100
99
100
97
99
100
100
100
75
73
77
________
96
55
79
66
70
88
100
21
95
35
62
37
72
71
100
24
95
53
83
43
82
67
100
23
Figure 1. Chlorophyll readings in various nonirrigated turfgrass species.
Control (No Irriga on)
700
600
Chlorophyll Reading
500
Bermudagrass
400
Poverty Oatgrass
Side Oats Grama
300
Tall Fescue
200
100
0
Jul-13
Aug-13
Sep-13
Oct-13
Nov-13
Figure 2. Chlorophyll readings in various irrigated turfgrass species.
Control (Irriga on)
600
Chlorophyll Reading
500
400
Bermudagrass
Poverty Oatgrass
300
Side Oats Grama
Tall Fescue
200
100
0
Jul-13
Aug-13
Sep-13
Oct-13
Nov-13
Figure 3. Chlorophyll readings in nonirrigated bermudagrass under various pest
management regimes.
Bermudagrass (No Irriga on)
800.00
700.00
Chlorophyll Reading
600.00
500.00
Control
Natria
400.00
Circle Organics
Espoma
300.00
200.00
100.00
0.00
Jul-13
Aug-13
Sep-13
Oct-13
Nov-13
Figure 4. Chlorophyll readings in irrigated bermudagrass under various pest
management regimes.
Bermudagrass (Irriga on)
700.00
Chlorophyll Reading
600.00
500.00
Control
400.00
Natria
300.00
Circle Organics
200.00
Espoma
100.00
0.00
Jul-13
Aug-13
Sep-13
Oct-13
Nov-13
Figure 5. Chlorophyll readings in nonirrigated Poverty Oatgrass under various pest
management regimes.
Poverty Oatgrass (No Irriga on)
350.00
Chlorophyll Reading
300.00
250.00
Control
200.00
Natria
150.00
Circle Organics
100.00
Espoma
50.00
0.00
Jul-13
Aug-13
Sep-13
Oct-13
Nov-13
Figure 6. Chlorophyll readings in irrigated Poverty Oatgrass under various pest
management regimes.
Poverty Oatgrass (Irriga on)
400.00
Chlorophyll Reading
350.00
300.00
Control
250.00
200.00
Natria
150.00
Circle Organics
100.00
Espoma
50.00
0.00
Jul-13
Aug-13
Sep-13
Oct-13
Nov-13