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Effect of Herbicides on Newly-Installed Sod

 

Tim R. Murphy and Clint Waltz

Extension Agronomists

The University of Georgia

 

There has been only limited research on the tolerance of newly-installed (laid) sod to herbicides.   Research conducted in North Carolina showed that Surflan, pendimethalin and Betasan applied during the active growth season in May before sod installation reduced root strengths 55 to 84% for a tall fescue/Kentucky bluegrass blend, centipedegrass, >Tifway= bermudagrass and >Meyer= zoysiagrass.  If applied immediately after sod installation on July 2 these same herbicides reduced root strengths 32 to 64%.  Ronstar was the only herbicide that did not reduce root strengths among these four previously mentioned turfgrass species.  Bermudagrass sod is now routinely  installed during the winter months in Georgia.  Additionally, tall fescue sod is commonly installed during the late winter and spring months.  Only limited information is available on the tolerance of  sod installed during the winter and spring months to either preemergence or postemergence herbicides.  Therefore, experiments were conducted at the Georgia Experiment Station in Griffin to determine the tolerance of turfgrass sod installed during the winter months to preemergence and postemergence herbicides.

 

 In these studies, bermudagrass (cv. >Tifway II=) and tall fescue (cv. >Rebel II=) sod was  installed the first week of February in 2000 and 2001 on freshly rototilled soil.  Before the sod was installed, expanded steel mesh grids 12 in. by 12 in., were laid on the soil surface.  Sod was rolled immediately after installation and was watered on an as needed basis to prevent water stress.  Recommended rates of  preemergence (Ronstar 2G, Pendulum 3.3EC, Dimension 1EC) herbicides were applied approximately 30 days after installation.  Both single full and sequential 2 labeled rate applications were evaluated.  The sequential application was made 8 weeks after the initial application.   The single full rate application rate for Dimension used in these studies was 0.75 lb. ai/acre which is actually a 1.5X rate, and is not labeled or recommended for use on turfgrasses.  This rate was selected so that the sequential application rate of 0.375 lb. ai/acre applied twice would equal the 1.5X single application of 0.75 lb. ai/acre.  In 2001 only, 3X rates of Ronstar 2G and  Pendulum 3.3EC and a 4.5X rate of Dimension 1EC were applied to simulate an accidental Aoverdose@ situation. Postemergence herbicides (Trimec Southern, Confront, 2,4‑D ester, Vanquish, Princep, Kerb) were applied to bermudagrass at the 50% spring green-up growth stage or approximately 47 days after installation.  The previously listed postemergence herbicides, with the exception of Kerb and Princep, were applied to tall fescue 43 days after installation

 

The effect of herbicides on root development was determined by measuring the force (lbs./sq. ft.)  required to pull the sod installed over a 12 in. by 12 in. steel mesh grid from the soil with a dynamometer.  Root strength data were recorded at 2 and 4 months after the initial herbicide application. Two 1.0 sq. ft. samples were pulled per plot at each sampling date.

 

 

 

Tall Fescue. Preemergence herbicides applied at recommended rates 30 days after sod installation did not decrease tall fescue root strengths at either 2 and 4 months after application in either year (Table 1).  In 2001, only Dimension applied at a 4.5X rate (2.25 lbs. ai/acre) reduced tall fescue root strength at 2 months after application.  However, by 4 months after application Dimension at the 4.5X rate did not reduce tall fescue root development.  At first glance these results may seem surprising.  However tall fescue root strengths at 30 days after sod installation was 185 and 157 lbs./sq. ft.  In other words tall fescue quickly initiated root growth in the first 30 days after sod installation. Additionally, no preemergence herbicide adversely affected tall fescue quality during this time period.

 

Table 1.  Effect of preemergence herbicides on tall fescue root development in 2000 and 2001.

 

 

 

 

 

 

Tall Fescue

 

 

 

 

 

2000

 

2001

 

Herbicide

 

Rate

 

2 months

 

4 months

 

2 months

 

4 months

 

 

 

lbs. ai/acre

 

B-------------(% Root Strength Reduction1,2)-----------------

 

Ronstar 2G

 

4.0

 

3

 

0

 

0

 

0

 

Ronstar 2G

 

2.0 fb3 2.0

 

19

 

0

 

2

 

4

 

Ronstar 2G

 

12.04

 

--

 

--

 

9

 

10

 

Pendulum 3.3EC

 

3.0

 

0

 

0

 

0

 

0

 

Pendulum 3.3EC

 

1.5 fb 1.5

 

17

 

0

 

0

 

0

 

Pendulum 3.3EC

 

9.04

 

--

 

--

 

11

 

6

 

Dimension 1EC

 

0.75

 

0

 

0

 

5

 

9

 

Dimension 1EC

 

0.38 fb 0.38

 

11

 

0

 

0

 

2

 

Dimension 1EC

 

2.254

 

--

 

--

 

22

 

9

 

LSD (0.05)

 

 

 

NS

 

NS

 

14

 

NS

 

1Root strength reduction values in comparison to untreated (no herbicide) control plots.

 

2Root strengths for tall fescue on day of initial herbicide application were 185 and 157 lbs./sq. ft. in 2000 and 2001, respectively.

 

3fb - followed by, second herbicide application was 8 weeks after the first application.

 

4This rate was applied only applied in 2001.

 

 

Postemergence herbicides applied approximately 45 days after sod installation did not decrease tall fescue root strength in either year (Table 2).  No postemergence herbicide visibly injured tall fescue (data not shown).

 

Table 2. Effect of postemergence herbicides on tall fescue root development in 2000 and 2001.

 

 

 

 

 

 

 

Tall Fescue

 

 

 

 

 

2000

 

2001

 

Herbicide

 

Rate

 

2 months

 

4 months

 

2 months

 

4 months

 

product/acre

 

B----------(% Root Strength Reduction1,2)-------------

 

Trimec Southern

 

2.0 pts.

 

0

 

0

 

12

 

0

 

Confront

 

2.0 pts.

 

0

 

0

 

2

 

0

 

2,4-D ester

 

2.0 pts.

 

0

 

4

 

5

 

0

 

Vanquish 4L

 

1.0 pt.

 

0

 

0

 

17

 

5

 

LSD (0.05)

 

 

 

NS

 

NS

 

NS

 

NS

 

1Root strength reduction values in comparison to untreated (no herbicide) control plots.

 

2Root strengths for tall fescue on day of initial herbicide application were 243 and 282 lbs./sq. ft. in 2000 and 2001, respectively.

 

Bermudagrass.  Preemergence herbicides applied 30 days after sod installation did not decrease bermudagrass root strengths at either 2 and 4 months after application in 2000 (Table 3).  However, in 2001, Dimension at 0.75 lbs. ai/acre reduced bermudagrass root strength 59% at the 2 month evaluation.  The maximum single application rate currently recommended on the Dimension 1EC label is 0.5 lbs. ai/acre (2.0 qts. product/acre).  Thus, the 0.75 lbs. ai/acre rate represents a 50% overdose relative to the maximum single rate application of 0.5 lbs. ai/acre.  Dimension applied at the sequential application recommended rates (0.38 + 0.38 lbs. ai/acre) did not reduce bermudagrass root strengths in either year.  In 2001, Pendulum at the 3X rate, or the simulated Aoverdose@ application rate, reduced bermudagrass root development 69% at 2 months after treatment, but not at 4 months after treatment.  Dimension at the 4.5X rate severely reduced bermudagrass root development at 2 and 4 months after treatment in 2001. Ronstar did not affect bermudagrass root strengths in either year of this study. No preemergence herbicide adversely affected bermudagrass spring transition (green-up) in 2000 (data not shown).  In 2001, only Pendulum at the 3X rate, and Dimension at the 1X and 3X rates affected bermudagrass spring transition at 2 months after herbicide application.  

 

 

 

Table 3.  Effect of preemergence herbicides on bermudagrass root development in 2000 and 2001.

 

 

 

 

 

 

 

Bermudagrass

 

 

 

 

 

2000

 

2001

 

Herbicide

 

Rate

 

2 months

 

4 months

 

2 months

 

4 months

 

 

 

lbs. ai/acre

 

B-------------(% Root Strength Reduction1,2)-----------------

 

Ronstar 2G

 

4.0

 

4

 

0

 

0

 

0

 

Ronstar 2G

 

2.0 fb3 2.0

 

0

 

0

 

0

 

0

 

Ronstar 2G

 

12.04

 

--

 

--

 

0

 

0

 

Pendulum 3.3EC

 

3.0

 

2

 

0

 

31

 

0

 

Pendulum 3.3EC

 

1.5 fb 1.5

 

0

 

3

 

16

 

0

 

Pendulum 3.3EC

 

9.04

 

--

 

--

 

62

 

0

 

Dimension 1EC

 

0.75

 

15

 

0

 

59

 

0

 

Dimension 1EC

 

0.38 fb 0.38

 

13

 

0

 

40

 

0

 

Dimension 1EC

 

2.254

 

--

 

--

 

70

 

60

 

LSD (0.05)

 

 

 

NS

 

NS

 

42

 

40

 

1Root strength reduction values in comparison to untreated (no herbicide) control plots.

 

2Root strengths for bermudagrass on day of initial herbicide application were 16 and 20 lbs./sq. ft. in 2000 and 2001, respectively.

 

3fb - followed by, second herbicide application was 8 weeks after the first application.

 

4This rate was applied only applied in 2001.

 

 

Postemergence herbicides applied approximately 45 days after sod installation did not decrease bermudagrass root strengths in either year (Table 4). Confront at 2.0 pts./acre was the only postemergence herbicide  to cause more than 20% injury to bermudagrass (data not shown).  Injury from this herbicide was > 20% for up to 48 days after application in 2000.  However, at 57 days after application injury was only 10%.  In 2001, bermudagrass injury with Confront was only 6% at 42 days after application, and no visible injury was apparent by 48 days after application.  Although, Confront did cause visible injury in both years, bermudagrass root development was not affected.

 

Table 4. Effect of postemergence herbicides on bermudagrass root development in 2000 and 2001.