herbicidal management of the invasive king ranch ( ) and...

Herbicidal Management of The Invasive King Ranch (Bothriochloa ischemum) and Kleberg Bluestems (Dichanthium

annulatum) in South Texas

Morgan McCutchen¹, Joshua McGinty², Megan K. Clayton², and Alinna M. Umphres¹¹Texas A&M University-Kingsville, ²Texas A&M AgriLife Extension Service

OBJECTIVES

MATERIALS AND METHODS

RESULTS AND DISCUSSION

CONCLUSIONS

ACKNOWLEDGEMENTS

INTRODUCTION

FURTHER RESEARCH

Land graciously provided by: Bud Keonning

• King Ranch (KR) bluestem (Bothriochloa ischemum (L.) Keng) and Kleberg bluestem

(Dichanthium annulatum Forssk.) are invasive grass species that were originally

introduced for hay production, erosion control, and revegetation in pastures or

rangelands (Alderson and Sharp 1994).

• Typically used on the southern plains for livestock production these bluestems are

highly competitive and are drought tolerant allowing them to outcompete native

grasses (Coyne and Bradford 1989, Gabbard and Fowler 2007, Fulbright et al.

2013).

• Prior research conducted of mechanical management practices like mowing, or

summer fire can promote bluestem growth (Lesak 2016).

• Several studies have been done to determine the most economical and effective

herbicide treatments to control theses bluestems (Harmony 2016). Harmony et al.

(2010) showed that when glyphosate was applied in sequential applications reduced

bluestem frequencies by 87%.

Site Location

• The study was conducted in 2019 Nueces county on the Coastal Prairie Region

(27°44'08.1"N 97°49'53.9"W) on Victoria clay soil.

Plot Design

• Plots were organized into a randomized complete block design (RCBD) with 3x6-meter

plots with three replications of each treatment

Herbicide Applications

• There were 15 herbicide treatments tested as well as a nontreated check (NTC; Table

1).

• Applications were applied using a CO2–pressurized backpack using Teejet TTI 11002

nozzles to deliver 15 GPA total spray volume at 38 PSI.

• First applications (Timing A) were applied in April 2019.

• For treatments 1-7 glyphosate was re-applied as bluestems began to recover in June

and October 2019.

Data

• Bluestem density counts were collected by randomly selecting an area with a 0.3x0.3

m2 quadrat (3 counts per plot) performed biweekly.

• Post-treatment bluestem density data was compared to pre-treatment means for each

plot to measure stand reduction over the season.

• An ANOVA analysis of percent plant reduction at 39 DAT A, 35 DAT B, and 35 DAT C

was done on SAS.

Alderson, J., & Sharp, W. (1994). Grass varieties in the United States. U.S. Department

of Agriculture Agriculture Handbook, (170), 20–69. doi: 10.5962/bhl.title.97052

Coyne, P. I., & Bradford, J. A. (1989). Biomass Partitioning in ‘Caucasian’ and ‘WW-

Spar’ Old World Bluestems. Range Management.

Gabbard, B. L., & Fowler, N. L. (2007). Wide Ecological Amplitude of a Diversity-

Reducing Invasive Grass. Biological Invasions, 9(2), 149–160. doi: 10.1007/s10530-

006-9012-x

Harmoney, K. R., Stahlman, P. W., Geier, P. W., & Hickman, K. R. (2010). Rate and

Timing of Glyphosate Application to Control Caucasian Old World Bluestem

(Bothriochloa bladhii). Invasive Plant Science and Management, 3(3), 310–314. doi:

10.1614/ipsm-d-10-00006.1

Harmoney, K. R. (2016). Old World Bluestem Seedling Emergence and Vegetative

Cover Following Glyphosate Treatment. Kansas Agricultural Experiment Station

Research Reports, 2(2). doi: 10.4148/2378-5977.1182

Leask, M. (2016). Management of Invasive Old World Bluestems to Restore Native

Grasslands. Texas A&M University-Kingsville Thesis.

References

• A second year of data currently being conducted to corroborate these results.

• Evaluate the efficacy of different rates and timings for glyphosate paired with pre-

emergent herbicides.

At 49 days after application A (DAA), treatments of Roundup WM (Weathermax) 3.3

qt, Arsenal 1 pt + Roundup WM 1 qt, Roundup WM 1 qt + Prowl H2O 3 qt, Roundup

WM 1 qt followed by (fb) Liberty 280 SL 1 qt, Roundup WM 1 qt, Esplanade 200 SC

3 fl oz, and Roundup WM 1 qt + Esplanade 200 SC 5 fl oz resulted in a significant

decrease in bluestem density of 41 to 80% versus the NTC of 8%.

At 47 DAB there was a 43-55% decrease in bluestem density with treatments of

Roundup WM 1 qt + Prowl H2O 3 qt (A) fb Roundup WM 1 qt (B), Roundup WM 1

qt + Esplanade 200 SC 5 fl oz (A) fb Roundup WM 1 qt (B), Roundup WM 1 qt +

Esplanade 200 SC 3 fl oz (A) fb Roundup WM 1 qt (B), Roundup WM 1 qt +

Esplanade 200 SC 3 fl oz (A) fb Roundup WM 1 qt + Esplanade 200 SC 3 fl oz (B),

Roundup WM 1 qt (A) fb Roundup WM 1 qt (B), Roundup WM 1 qt + Esplanade 200

SC 5 fl oz (A) fb Roundup WM 1 qt (A) fb Roundup WM 1 qt (B), Roundup WM 1 qt

+ Esplanade 200 SC 5 fl oz (A) fb Rounup WM 1 qt (B), Roundup WM 1 qt + Prowl

H2o 3 qt (A) fb Roundup WM 1 qt (B) and Roundup WM 3.3 qt (A).

Finally, at 25 DAC there was a 67 to 79% decrease in bluestem density with

treatments of Roundup WM 1 qt + Esplanade 200 SC 5 fl oz (A) fb foundup WM 1

qt (B,C), Roundup WM 1 qt + Esplanade 200 SC 3 fl oz (A) fb Roundup WM 1 qt

(B,C), Roundup WM 1 qt (A,B,C) and Roundup WM 1 qt + Prowl 3 qt (A) fb

Roundup WM 1 qt (b,C)

Figure 1. Percent reduction in bluestem density at 49 days after application A (DAA),

47 days after application B (DAB), and 25 days after application C (DAC), Banquete,

Tx, 2019. Treatment numbers refer to treatments listed in Table 1.

• This study revealed several treatments for effective season-long management of KR

and Kleberg bluestem. These included treatments of sequential applications of

Roundup WM often paired with preemergence herbicides such as Prowl H2O or

Esplanade 200 SC to prevent new seedlings from emerging.

• Single applications of Arsenal, Roundup WM at 1 qt, Roundup WM + Arsenal,

Pastora applied in the fall, or sequential applications of pastora made in the

spring/summer did not provide lasting control of these bluestem species.

Table 1. Products, active ingredients, rates, and application timings applied to study

site, Banquete, Tx, 2019.

Figure 2. Photos of the study site, Banquete, Tx, 2019.

• Evaluate the efficacy of several herbicide treatments and timings for eliminating

existing stands and preventing new seedlings of KR and Kleberg bluestem in South

Texas rangelands and pastures

Treatment Chemical Name Active Ingredient Rate Timing

1 Roundup WM Glyphosate 32 fl oz A,B,C

2Roundup WM Glyphosate 32 fl oz A,B,C

Esplanade 200 SC Indaziflam 5 fl oz A

3

Roundup WM Glyphosate 32 fl oz A,B,C


Esplanade 200 SC Indaziflam 3 fl oz B


Prowl Pendimethalin 3 qt A






Prowl H2O Pendimethalin 3 qt A

8 Arsenal Imazapyr 1 pt A

9 Roundup WM Glyphosate 32 fl oz A

10 Roundup WM Glyphosate 3.3 qt A

11Roundup WM Glyphosate 32 fl oz A

Liberty 280 SL Glufosinate-ammonium 32 fl oz 5-7 days later

12Arsenal Imazapyr 1 pt A

Roundup WM Glyphosate 32 fl oz A

13

Pastora Nicosulfuron + metsulfron-methyl 1.5 oz A

Pastora Nicosulfuron + metsulfron-methyl 1 oz B

14

Pastora Nicosulfuron + metsulfron-methyl 0.5 oz A

Pastora Nicosulfuron + metsulfron-methyl 0.5 oz B

15 Pastora Nicosulfuron + metsulfron-methyl 1.5 oz C

16 NTC Control 1 oz

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