Management of Vegetation Under Texas Highways Guardrails

Home , Dithiopyr

111111111 mill IIIIII mi HIM 11 m °ioz-i3 Technical Report Documentation Page 1. Report No. 2. Government Accession No. 3. Recipient's Catalog No. TX-95/902-13 4. Title and Subtitle 5. Report Date MANAGEMENT OF VEGETATION UNDER TEXAS HIGHWAYS January 1992 GUARDRAILS Revised: January 1995 6. Performing Organization Code

7. Authors) 8. Performing Organization Report No. Robert E. Meyer, Cynthia L. Benner, Ernest S. Motteram, and Wayne Research Report 902-13 G. McCully 9. Performing Organization Name and Address 10. Work Unit No. fTRAIS) Texas Transportation Institute The Texas A&M University System 11. Contract or Grant No. College Station, Texas 77843-3135 Study No. 7-902 12. Sponsoring Agency Name and Address 13. Type of Report and Period Covered Texas Department of Transportation Interim: Research and Technology Transfer Office April 1991-January 1995 P. 0. Box 5080 14. Sponsoring Agency Code Austin, Texas 78763-5080

15. Supplementary Notes Research performed in cooperation with the Texas Department of Transportation Research Study Title: Roadside Vegetation Management Research Program 16. Abstract Guardrails present particular vegetation management problems along highways. The goal of this study was to test chemical methods for controlling winter annual and biennial vegetation under guardrails at a site each in the Pineywoods, Blackland Prairie, and Edwards Plateau areas of Texas. This study tested several chemical herbicides alone and in combination to determine their effectiveness for controlling vegetation around guardrails when applied in February, 1991. Roundup (glyphosate) controlled vegetation adequately for 2 to 4 weeks. Arsenal (imazapyr) controlled vegetation 5 to 10 weeks. Arsenal and Roundup alone were usually equally effective as when mixed with other herbicides. Dimension (dithiopyr), Pennant (metolachlor), Poast (sethoxydim), Snapshot (oryzalin+isoxaben), Stomp (pendimethalin), Surflan (oryzalin), and Whip (fenoxaprop-ethyl) did not provide consistent, effective vegetation control.

17. Keywords 18. Distribution Statement Arsenal, Dimension, Dithiopyr, Fenoxaprop-Ethyl, No restrictions. This document is available to the Glyphosate, Guardrail, Herbicide, Imazapyr, public through NTIS: Isoxaben, Metolachlor, Oryzalin, Pendimethalin, National Technical Information Service Pennant, Poast, Roadside Vegetation Management, 5285 Port Royal Road Roundup, Sethoxydim, Snapshot, Stomp, Surflan, Springfield, Virginia 22161 Whip.

19. Security Classif.(of this report) 20. Security Classif.(of this page) 21. No. of Pages 22. Price Unclassified Unclassified 43 Form DOT F 1700.7 (8-72) Reproduction of completed page authorized MANAGEMENT OF VEGETATION UNDER TEXAS HIGHWAY GUARDRAILS

Robert E. Meyer, Ph.D. Research Scientist Texas Transportation Institute

Cynthia L. Benner Research Associate Texas Transportation Institute

Ernest S. Motteram Research Assistant Texas Transportation Institute

and

Wayne G. McCully, Ph.D. Department of Vegetation Management Texas Transportation Institute

Research Report 902-13 Research Study 7-902 Research Study Title: Roadside Vegetation Management Research Program

Sponsored by Texas Department of Transportation

January 1995

TEXAS TRANSPORTATION INSTITUTE The Texas A&M University System College Station, Texas 77843-3135 IMPLEMENTATION STATEMENT

The findings reported here are offered for the guidance of District and Section personnel involved with managing vegetation under guardrails and around fixtures, particularly near Kerrville, Lufkin, and Somerville. These findings confirm the effectiveness of Roundup for providing adequate control of emerged vegetation for 2 and maybe 4 to 5 weeks. Arsenal shows promise for controlling most vegetation for 5 to 10 weeks or more where desirable woody vegetation is more than about 30.5 m (100 ft) away. Further research is needed with Arsenal to confirm its usefulness for vegetation management along highways throughout Texas.

v DISCLAIMER

The contents of this report reflect the views of the authors who are responsible for the facts and accuracy of the data presented herein. The contents do not necessarily reflect the official views or policies of the Texas Department of Transportation. This report does not constitute a standard, specification, or regulation.

Tradenames are used for convenience only and do not constitute an endorsement of the materials named by either the Texas Department of Transportation or Texas Transportation Institute, nor is it a recommendation over comparable products not named.

vii TABLE OF CONTENTS

LIST OF TABLES x

LIST OF ABBREVIATIONS AND SYMBOLS xi

SUMMARY xiii

INTRODUCTION 1

THE PROBLEM 5

MATERIALS AND METHODS 7

RESULTS 9 Kerrville 9 Lufkin 14 Somerville 15

DISCUSSION 21

REFERENCES 25

APPENDIX A 27

APPENDIX B 29

ix LIST OF TABLES

Table 1. Overall whole plot vegetation injury caused by nine herbicides applied under highway guardrails near Kerrville, Lufkin, and Somerville, Texas, on February 6, February 26, and March 5, 1991, and rated two or three times later 10

Table 2. Injury to individual species caused by nine herbicides applied under highway guardrails near Kerrville, Texas, on February 6, 1991, and rated 2, 4, and 10 wk later 12

Table 3. Injury to individual species caused by nine herbicides applied under highway guardrails in Lufkin, Texas, on February 26, 1991, and rated 2 and 5 wk later 16

Table 4. Injury to individual species caused by nine herbicides applied under highway guardrails near Somerville, Texas, on March 5, 1991, and rated 2 and 5 wk later 19

x LIST OF ABBREVIATIONS AND SYMBOLS

Abbreviations and symbols Item

A Acre(s) ft Foot (feet) gal/A Gallon(s) per acre in Inch(es) kg/ha Kilogram(s) per hectre km Kilometer(s) kPa Kilopascal(s) L/ha Liter(s) per hectare m Meter(s) mi Mile(s) mm Millimeter(s) oz/A Ounce(s) per acre psi Pound(s) per square inch pt/A Pint(s) per acre qt/A Quart(s) per acre SH State Highway US United States (highway) wk Week(s)

xi SUMMARY

Vegetation management under guardrails is a year-long process. Guardrail areas consist of long metal plates, supported by wood posts, and often accompanied by delineator posts. Also, the guardrails are mounted at different distances from the pavement. These factors affect the ease in attaining complete spray coverage. This study was undertaken to develop herbicide treatments primarily for the control of winter annual grass and broadleaf vegetation at Kerrville, Lufkin, and Somerville. Roundup (glyphosate) at 1.17 L/ha (1 pt/A) alone and in mixtures with Dimension (dithiopyr), Pennant (metolachlor), Snapshot (oryzalin + isoxaben), and Surflan (oryzalin) generally gave the best vegetation control after 2 wk. Arsenal (imazapyr) at 4.68 L/ha (2 qt/A) either alone or in a mixture with Stomp (pendimethalin) controlled the vegetation most effectively after 4 to 5 and 10 wk. Arsenal or Roundup applied alone was usually equally effective as when mixed with other herbicides. Under the conditions of this study, Dimension, Pennant, Poast (sethoxydim), Snapshot, Stomp, Surflan, and Whip (fenoxaprop-ethyl) alone controlled vegetation somewhat, but not sufficiently enough for commercial spraying of guardrail vegetation. Results of this study indicate that winter applications of pre- or postemergence herbicides have limited usefulness unless the chemical has some soil activity such as Arsenal. Otherwise, an early spring spray of a nonselective herbicide, such as Roundup, would provide vegetation control until application of summer treatments.

xiii MANAGEMENT OF VEGETATION UNDER TEXAS HIGHWAY GUARDRAILS

INTRODUCTION

The Texas Department of Transportation (TxDOT) has the responsibility for providing attractive and safe conditions, including vegetation management, on the highways of Texas. Various procedures are used to manage vegetation, including mechanical methods such as mowing, chemical methods with the use of herbicides, and propagation methods including planting of grasses, wild flowers, shrubs, and trees. Vegetation along highways is desirable to provide a pleasing appearance and to minimize erosion. Several relatively new herbicides have been considered for vegetation management on highways. Arsenal1 (imazapyr) is a nonselective herbicide that is effective either preemergence or postemergence to control weeds because of its extended soil residual activity (Colby et al., 1989; Thomson, 1986). Arsenal has demonstrated excellent control of a wide variety of annual and perennial weeds, deciduous trees, vines, and brambles in noncrop situations. It also has promise for pine release applications in forestry (Van Cantfort et al., 1985) . Both the foliage and roots absorb Arsenal, and it may persist in the soil 3 to 12 months depending on dosage and rainfall. Dimension (dithiopyr) is primarily effective for preemergence or early post emergence control of annual grasses and annual broadleaf weeds in established turfgrasses. In the South, Dimension has controlled large crabgrass2 in

1Appendix A presents herbicide tradenames, common names, and chemical names.

2Appendix B presents common and scientific plant names listed by Hatch et al., 1990 and Patterson, 1989.

1 Kentucky bluegrass, tall fescue, and perennial ryegrass turf {Enache and llnicki, 1991). Also, Dimension has controlled or suppressed the growth of annual bluegrass, Carolina geranium, common chickweed, foxtail, goosegrass, henbit, prostrate spurge, lespedeza, dandelion, and yellow woodsorrel (Dutt et al., 1990; Enache and llnicki, 1991; Higgins et al., 1991; Jacqschitz and Sawyer, 1989). Pennant (metolachlor) is a selective herbicide for the control of annual grass weeds and certain annual broadleaf species in numerous crops (Colby et al., 1989). Pennant is usually applied preemergence at rates of 2.40 to 4.80 L/ha (0.26 to 0.51 gal/A). Mixtures of Pennant with other herbicides are effective for control of most annual grass and broadleaf species.

Poast (sethoxydim) selectively controls annual and perennial grass weeds in more than 200 broadleaf crops for food and non-food uses (Colby et al., 1989). Poast is generally applied postemergence because of its fairly rapid absorption into plant foliage. However, Poast does have some short-term soil persistence that prevents grass seed germination. On rights-of-way, Poast suppressed seedhead formation in bermudagrass in Oklahoma (Montgomery et al., 1989) and tall fescue in Alabama and Georgia (Evans et al., 1987).

Roundup (glyphosate) is a widely used, broad-spectrum herbicide useful for crop and non-crop control (Colby et al., 1989). It is absorbed primarily through the foliage and has very little soil activity. Roundup is used alone on Texas highways for total vegetation control on paved shoulders and paved medians; pavement edges and curbs; and around guardrails, sign posts, delineator posts, and rip-rap (Anonymous, 1991; Trans. Res. Board, 1988). Roundup is used alone to control wild oats and jointed goatgrass and with or without Oust (sulfometuron methyl) to control johnsongrass. Researchers recommend Roundup for use in a ropewick apparatus to control tall grass and broadleaf weeds (Anonymous, 1991). A rainfree period of 4 hours is sufficient for maximum johnsongrass control with Roundup (Barrett and Olsen, 1985).

2 Roundup is used to control actively growing bermudagrass, but it also can be used to kill only winter weeds when the bermudagrass is dormant (Johnson and Ware, 1978). Surflan (oryzalin) effectively controls many annual and broadleaf weeds in crops at rates of 1.75 to 3.51 L/ha (0.75 to 1.50 qt/A) primarily as a preemergence herbicide (Colby et al., 1989). Surflan also controls annual grass and broadleaf weeds in bermudagrass and in fruit or nut crops, vineyards, ornamentals, and non-crop areas.

Snapshot is a mixture of oryzalin+ isoxaben designed to control many grass and broadleaf weed species. Isoxaben is used primarily as a preemergence herbicide to control a wide spectrum of broadleaf weeds including: buckhorn plantain, Carolina geranium, henbit, hop clover, and shepherds-purse (Colby et al., 1989; Grant et al., 1990). Isoxaben, however, has been ineffective for controlling bermudagrass and bahiagrass .

Stomp (pendimethalin) is primarily a preemergence herbicide used for weed control in corn and a number of broadleaf crops at rates of 3.74 to 7.47 kg/ha (53.3 to 107 oz/A). Stomp controls several grasses including foxtail and crabgrass species and selected broadleaf species such as lambsquarters and purslane. Stomp is ineffective on morningglory species and ragweed species (Thomson, 1986).

Whip (fenoxaprop-ethyl) is a selective postemergence herbicide for the control of many annual and perennial grassy weeds, including bermudagrass and johnsongrass (Colby et al., 1989; Thomson, 1986). Annual grasses should be treated when 76 to 152 mm (3 to 6 in) tall and johnsongrass when 254 to 381 mm (10 to 15 in) tall. Most broadleaf crops tolerate applications of Whip.

The goal of this study was to develop a usable method for controlling winter annual and biennial vegetation under highway guardrails at three sites in Texas. The objectives of the study were to evaluate vegetation response to

3 herbicides (a) at Lufkin in the East Texas Pineywoods, (b) near Somerville in the Blackland Prairies, and (c) near Kerrviiie on the Edwards Plateau.

4 THE PROBLEM

Winter annual and biennial vegetation germinate in late fall to early spring after summer annual and perennial vegetation have been controlled by summer applications of herbicides. Some of these winter annual and biennial species may grow more than 305 mm (1 ft) tall causing an unsightly appearance before the summer annual and perennial species produce much top growth. Also, the winter annual vegetation may become a fire hazard after it dies in the spring. Winter applications of herbicides could be an efficient vegetation management tool. Appropriate herbicide treatments could control winter vegetation. If the herbicide had adequate persistence in the soil, it might remain long enough to control germinating summer annuals and some perennial species. Also, the spraying equipment could be used for a longer period in the year.

5 MATERIALS AND METHODS

Researchers selected three guardrail sites for this study. About 8.0 km (5 mi) east of Kerrville, guardrails were used in a hilly area overlooking steep drop-offs on both the eastbound and westbound lanes of US 290. In Lufkin, both ends of a railroad-highway overpass on US 59 were selected with guardrails being used on both the northbound and southbound lanes. About 4.8 km (3 mi) south of Somerville, we used guardrails next to low areas south of Yegua Creek on both the northbound and southbound lanes of SH 36. Because the guardrails were not long enough for the entire test, some of the plots had to be established beyond the end of the guardrails.

At each site, the test consisted of 66 plots 1.5 by 9.3 m (5 by 30.5 ft) for three groups of 22 herbicide treatments. Complete sets of treatments were established together on one side of the road at Lufkin and Kerrville to minimize variation among plots. Because of insufficient guardrail length near Somerville, one set of plots had to be divided between the northbound and southbound lanes.

Herbicide treatments included: 9.35 and 18.71 L/ha (1 and 2 gal/A) rates of Dimension (dithiopyr); 2.40 and 4.80 L/ha (0.26 and 0.51 gal/A) rates of Pennant (metolachlor); 3.12 and 6.24 L/ha (0.33 and 0.67 gal/A) rates of Poast (sethoxydim); 2.80 and 5.60 kg/ha (40 and 80 oz/A) rates of Snapshot (oryzalin + isoxaben); 3.74 and 7.47 kg/ha (53.3 and 106.7 oz/A) rates of Stomp (pendimethalin); 1.75 and 3.51 L/ha (0.75 and 1.5 qt/A) rates of Surflan (oryzalin); 1.56 and 3.12 L/ha (21.3 and 42.7 oz/A) rates of Whip (fenoxaprop- ethyl); 1.17 L/ha (1.0 pt/A) of Roundup (glyphosate) alone and with the low rates of Dimension, Pennant, Snapshot, and Surflan; and 4.68 L/ha (2 qt/A) rate of Arsenal (imazapyr) alone and with 3.74 kg/ha (53.3 oz/A) of Stomp.

7 Untreated plots were also included. Sprays were applied in 1991 near Kerrville on February 6-7, Lufkin on February 26-27, and Somerville on March 5-6. A wheel mounted sprayer with a three-nozzle boom applied herbicides to a swath 1.5 m (5 ft) wide at the rate of 233.8 L/ha (25 gal/A) with a compressed air system held at 207 kPa (30 psi). The spray swath edge was held at the edge of the paved shoulder; one to three nozzles were held between the pavement edge and the guardrail depending on the location of the guardrail. The nozzles, which sprayed an 80 degree angle, were held just high enough so that the spray did not hit the guardrail. Drop pipes 610 mm (2 ft) long held nozzles, where necessary, to allow the boom to clear guardrail and delineator posts.

Vegetation response ratings were made 2 and 5 wk after spraying at Lufkin and Somerville and 2, 4, and 10 wk after spraying at Kerrville. The presence and response to herbicides by all species were recorded in 10 quadrats 305 mm (1ft) square placed randomly in the plot. Plant injury ratings varied from 0% being no injury to 100% being death of the plant. Also, a single overall visual whole plot rating was made averaging the response of all vegetation in each plot at each rating date.

The data were subjected to analyses of variance. The Duncan multiple range test separated means at the 5% level for each species at each rating date.

8 RESULTS

KERRVILLE

The research area became progressively drier during the test as shown by increasing injury on untreated plants at 5, 15, and 20% after 2, 4, and 10 wk, respectively. Only about 89 mm (3.5 inches) of rain fell during the 10-wk period following spraying. At 2 wk after spraying, Arsenal alone and all treatments with Roundup caused the most whole plot foliar injury (38 to 65%) (Table 1). After 5 wk, Arsenal alone and Roundup alone and in mixtures with Dimension, Pennant, or Snapshot were the most effective treatments (60 to 88%). After 10 wk, Arsenal and Stomp + Arsenal had killed essentially all vegetation (99%), and Dimension or Surflan plus Roundup had caused 62% foliar injury. On grasses 2 wk after spraying, treatments of Roundup alone and in a mixture with Dimension were the most injurious to rescuegrass (51 to 55%), followed by Roundup + Pennant, Snapshot, or Surflan (Table 2). After 4 wk, Arsenal alone and Roundup + Pennant were the most effective treatments followed by Roundup alone. After 10 wk, Arsenal alone and with Stomp had killed all the rescuegrass. One rate, but not always the highest rate, of Poast, Snapshot, Stomp, and Surflan also caused slight foliage injury compared with the untreated plots. Roundup alone was the most injurious treatment followed by Roundup mixtures to Japanese brome 2 wk after spraying (Table 2). After 4 wk, Arsenal alone, Roundup alone, and Roundup plus either Pennant or Surflan were the most effective treatments. After 10 wk, Japanese brome plants had died and disintegrated in the two Arsenal treatments. Roundup alone was the next best

9 Table 1. Overall whole plot vegetation injury caused by nine herbicides applied under highway guardrails near Kerrville, Lufkin, and Somerville, Texas, on February 6, February 26, and March 5, 1991, and rated 2 or 3 times later.

Herbicide1 Rate2 Location and weeks after spraying3 Kerrville Lu kin Somerville 2-Weeks 4-Weeks 10-Weeks 2-Weeks 5-Weeks 2-Weeks 5-Weeks Amt/ha Percent plant injury Arsenal 4.68 L 45 ab 88 a 99a 62 ab 85 a 30 cd 75 a Dimension 9.35 L 7d 17 de 32 be 5c 7 cde 13 de lOdef Dimension 18.71 L 7d 18 de 42 be 18 c 10 cde 10 e 17c-f Dimension 9.35 L+ 65 a 62 abc 62 b 53 ab 32 b 62 a 45 b + Roundup 1.17 L Pennant 2.40 L 5d 10 e 25 be 8c 10 cde 7e 7ef Pennant 4.80 L 10 cd 15 de 40 be 7c 8 cde 13 de 15c-f Pennant+ 2.40 L+ 57 a 83 ab 38 be 70 a 25 be 62 a 23c-f Roundup 1.17 L Poast 3.12 L 17 cd 20 de 45 be 10 c 8 cde 7e lOdef Poast 6.24 L 18 bed 18 de 48 be 12 c 8 cde 13 de 8ef Roundup 1.17 L 62 a 80 ab 50 be 57 ab 25 be 57 ab 30 be Table 1. Cont. Overall whole plot vegetation injury caused by nine herbicides applied under highway guardrails near Kerrville, Lufltin, and Somerville, Texas, on February 6, February 26, and March 5, 1991, and rated 2 or 3 times later.

Snapshot 2.80 kg 10 cd 20 de 40 be 7c 8cde 2e 5f

Snapshot 5.60 kg 13 cd 12 e 40 be 8c lOcde 3e lOdef

Snapshot + Ro 2.80+ 57 a 60abc 28 be 57 ab 22 bed 43 be 25 cde undup 1.17 L

Stomp 3.74 kg 8d 17 de 30 be 7c 17 e 5e 13 c-f

Stomp 7.47 kg 12 cd 3e 40 be 8c 12 cde 7e lOdef

Stomp+ 3.74 kg+ 25 bed 55 be 99 a 63 ab 83 a 33 c 82 a Arsenal 4.68 L

Surflan 1.75 L 3d 10 e 22 c 5c 8 cde 2e 8ef

Surflan 3.51 L 13 cd 15 de 42 be 12 c 5de 3e lOdef

Surflan+ 1.75 L+ 38abc 43 cd 62 b 47 b 18b-e 62 a 28 cd Roundup 1.17 L

Whip 1.56 L 17 cd 17 de 50 be 15 c 5de 5e lOdef

Whip 3.12 L 20 bed 23 de 35 be 15 c 8 cde 10 e 8ef

Untreated 5d 15 de 20 c 8c 7 cde 2e 8ef 'Herbicides: Arsenal=imazapyr, Dimension=dithiopyr, Pennant=metolachlor, Poast=sethoxydim, Roundup=glyphosate, Snapshot = oryazlin+isoxaben, Stomp=pendimethalin, Surflan=oryzalin, Whip=fenoxaprop-ethyl. 2Metric to English conversions: 1.17, 1.56, 1.75, 2.40, 3.12, 3.51, 4.68, 4.80, 6.24, 9.35, and 18.71 L/ha=16.0, 21.3, 24.0, 33.0, 42.7, 48.0, 64.0, 65.6, 85.4, 128.0, and 256.0 fluid oz/A; 2.80, 3.74, 5.60, and 7.47 kg/ha=40.0, 53.3, 80.0, and 106.7 dry oz/A, respectively. 3Values in columns followed by the same letter are not significantly different at the 5% level using Duncan's multiple range test. Table 2. Injury to individual species caused by nine herbicides applied under highway guardrails near Kerrville, Texas, on February 6, 1991, and rated 2, 4, and 10 wk later.

Treatment1 Rate2 Plant species3

Rescuegrass Japanese brome California burclover Carolina geranium4

2 Wk 4 Wk 10 Wk 2 Wk 4 Wk 10 Wk 2 Wk 4 Wk 10 Wk 2 Wk 4 Wk Percent plant injury

Arsenal 4.68 L 24 c 87 a 47 d 97a 18 cd 71 a 20 a 30 be

Dimension 9.35 L 5g lOfgh 25c-f 8ijk 16 e 32 gh Of 4gh 17 b-e 1 be 10 e-h Dimension 18.71 L 4g 9gh 26c-f 9ijk 10 ef 38 ef 2ef 4gh 20 bed 6bc 16d-g Dimension+ 9.35 +1.17 51 a 58 c 20def 66 be 78 b 171 35 a 58 be 20 be 10 be 20cde Roundup L

Pennant 2.40 L 3g 8gh 22def 6jk 10 ef 23 j 1 f 3gh lOhij 10 eh Pennant 4.80 L 5g ii m 20def 8ijk 13 ef 36 ef 8e 6gh 16c-f 6bc 7fgh Pennant+ 2.40+ 1.17 44b 88 a 15 f 72 b 95 a 19 kl 24 b 54 d 17 c-f 10 be 22 cd Roundup L

Poast 3.12 L 12def 14 fg 43 a 19 efg 16 e 46c 1 f 11 g 12 f-i 10 be 6fgh Poast 6.24 L 14 de 18 ef 17 ef 20 ef 31 d 32ghi 5ef 18 f 14 e-h 10 be 6fgh Roundup 1.17 L 55 a 79 b 30b-e 80a 94a 54 a 36 a 64 be 21 be — 50 a Table 2. (Cont.) Injury to individual species caused by nine herbicides applied under highway guardrails near Kerrville, Texas, on February 6, 1991, and rated 2, 4, and 10 wk later.

Snapshot 2.80 kg 9efg 14 fg 32a-d 12g-k 17 e 22 jk 2ef 3gh 22 b 6bc 9e-h

Snapshot 5.60 kg 13def 9gh 22def 12g-k 13 ef 43 d 2ef lh 29 a 9bc 9e-h Snapshot+ 2.80 kg+ 42 b 56 c 20def 63 c 79 b 37 ef 17 d 43 e 20 bed 14 ab 33 b Roundup 1.17 L

Stomp 3.74 kg 4g 7gh 36 abc lOh-k 14 ef 28 i 1 f 2h 16c-f 9bc 4gh Stomp 7.47 kg 7fg 8gh 21 def 15 f-i 10 ef 30 hi 4ef 3gh 16c-f 10 be 5gh Stomp+ 3.74 kg+ 18 d 48 d - 25e 64c - 21 bed 55 d - 13 ab 18 def Arsenal 4.68 L

Surflan 1.75 L 3g 6h 18 ef 5k 4f 10 m Of lh 9 hij 7bc 9e-h Surfian 3.51 L 9efg llfgh 40 ab 13 f-j 10 ef 39 e 1 f 6gh 15d-g 8 be 9e-h Surflan+ 1.75 + 39 b 48 d 18 ef 65 c 100 a 35 fg 23 be 68 ab 28 a 11 ab lOe-h Roundup 1.17 L

Whip 1.56 L 17 d 14 fg 30b-e 20 ef 11 ef 50 b 5ef 5gh 8ij 10 be 4gh

Whip 3.12 L 15 de 22 e 15 f 17fgh 18 e 35 fg 3ef 2h Si Oc 10 e-h

Untreated 3g lOfgh 19 def 4k 14 ef 20jkl 1 f 3gh lOg-j 9bc 9e-h 'Herbicides: Arsenal=imazapyr, Dimension=dithiopyr, Pennant=metolachlor, Post=sethoxydim, Roundup=glyphosate, Snapshot=oryazlin+isoxaben, Stomp=pendimethalin, Surflan=oryzalin, Whip=fenoxaprop-ethyl. 'Metric to English conversions: 1.17, 1.56, 1.75, 2.40, 3.12, 3.51, 4.68, 4.80, 6.24, 9.35,and 18.71 = 16.0, 21.3, 24.0, 33.0, 42.7, 48.0, 64.0, 65.6, 85.4, 128.0, and 256.0 fluid oz/A; 2.80, 3.74, 5.60, and 7.47 kg/ha=40.0, 53.3, 80.0, and 106.7 dry oz/A, respectively. 'Values in columns followed by the same letter are not significantly different at the 5% level using Duncan's multiple range test. 4Arsenal alone or with Stomp killed all plants. No other treatment caused plant injury to exceed that of the untreated plants (32%) after 10 weeks. treatment, but it was less effective than at 4 wk indicating that some regrowth had occurred. Of broadleaf species present, only California burclover and Carolina geranium occurred frequently enough to analyze statistically. After 2 wk, Roundup either alone or with Dimension was most effective on California burclover (35 to 36%) (Table 2). After 4 wk, Arsenal alone and Roundup + Surflan were most effective.

After 10 wk, California burclover had died in the Arsenal plots leaving either Snapshot at 5.60 kg/ha (80 oz/A) or Surflan + Roundup the next most effective treatments (28 to 29%). Carolina geranium showed only 20% or less injury at 2 wk (Table 2). After 4 wk, Roundup alone caused the most injury at 50%. At 10 wk, no Carolina geranium plants were present in the Arsenal plots (data not shown), but the plants in the untreated plots showed 32% injury indicating that the plants were naturally drying out.

LUFKIN

Overall, whole plot ratings showed that Dimension, Pennant, Poast, Snapshot, Stomp, Surflan, and Whip alone had little effect, causing injury ratings of 18% and 17% or less at 2 and 5 wk, respectively (Table 1). Arsenal and Roundup were equally effective for injuring vegetation 2 wk after spraying (Table 1). Arsenal or Roundup alone or in combination with other herbicides caused overall whole plot ratings of 47% to 70% 2 wk after spraying. By 5 wk, Arsenal alone and with Stomp continued to increase vegetation injury from 83 to 85%. Stomp had no effect on the Arsenal activity. Roundup additions to other herbicides caused slightly increased, but not statistically significant, injury compared with the other herbicides alone, except for Dimension.

14 Injury to the most frequent species at Lufkin caused by herbicides (Table 3) was similar to that of the whole plot rating after 2 and 5 wk (Table 1). At 2 wk, Pennant + Roundup caused the most rescuegrass injury (37%) followed by the two treatments with Arsenal and with Roundup plus Dimension, Snapshot, or Surflan. The two Arsenal treatments injured Carolina geranium the most (37 to 43%). California burclover was injured most by Pennant + Roundup (34%) followed by treatments of Roundup or Arsenal either alone or in mixtures. Prairie bishop, a carrot-like species of the Umbelliferae, was severely injured by Arsenal alone and Roundup either alone or in mixtures (73 to 81 %). Common vetch was most injured by Snapshot + Roundup (21%) followed by other Arsenal, Stomp + Arsenal, and Roundup mixtures. Five wk after spraying (Table 3), Arsenal or Stomp + Arsenal treatments were more injurious to all species (rescuegrass 73 to 86%, Carolina geranium 66 to 83%, California burclover 50 to 53%, prairie bishop 79 to 84%, common vetch 68 to 75%) than any of the other treatments, including those with Roundup. Pennant and Snapshot were slightly injurious to Carolina geranium. At least the high rate of Dimension, Poast, and Snapshot were slightly injurious to prairie bishop. Dimension was slightly injurious to common vetch. These results indicate that Arsenal and Roundup were about equally effective for controlling vegetation at 2 wk. Thereafter, Arsenal caused progressively more vegetative injury through 5 wk, whereas, control with Roundup either remained about the same or decreased. Dimension, Pennant, Poast, Snapshot, Stomp, Surflan, and Whip generally had limited effect on the vegetation compared with the untreated plots.

SOMERVILLE

On whole plot ratings, treatments having Roundup caused the most vegetative injury (43 to 62%) 2 wk after spraying (Table 1). Treatments with

15 Table 3. Injury to individual species caused by nine herbicides applied under highway guardrails in Lufkin, Texas, on February 26, 1991, and rated 2 and 5 wk later.

Treatment1 Rate2 Plant species3 Rescuegrass Carolina California Prairie bishop Common vetch geranium burclover 2 wk 5 wk 2 wk 5 wk 2 wk 5 wk 2 wk 5 wk 2 wk 5 wk t plant injui -y Arsenal 4.68 L 20 b 73 b 43 a 66b 21 b 50 a 80 a 84 a 17 b 75 a Dimension 9.35 L U Oe 11 f-i 13 d-e 1 d 1 e 12def 21 e-h Od 14 be Dimension 18.71 L 4fg 1 de 15 efg 9 e-i 8c 3e 15 d 25 ef 2d 10 bed Dimension 9.35 16 be 6 cde 21 c 28 c 22 b 19 c 75 ab 40 c 17 b 15 b +Roundup + 1.17 L Pennant 2.40 L li 1 de 9hij 16d-g Od Oe 12def 22 e-h 1 d 1 e Pennant 4.80 L lg Oe 8hij 15 d-h 1 d Oe 8def 20fgh Od 1 e Pennant+ 2.40+ 37 a 9c 22 c 10 e-j 34 a 15 d 73 be 23e-g 14 be 15 b Roundup 1.17 L Poast 3.12 L 8ef 2de 8hii 7hij Od Oe 12def 20fgh 2d Oe Poast 6.24 L 10 de 5 cde 7ij 7hij 2d 1 e 12def 34 ef Od 5de Roundup 1.17 L 12 cd 4 cde 24 c 20 cd 18 b 36 b 79 a 39 c 12 c 14 b Table 3. (Cont.) Injury to individual species caused by nine herbicides applied under highway guardrails in Lufkin, Texas, on February 26, 1991, and rated 2 and 5 wk later.

Snapshot 2.80 kg 2g Oe 10 g,j 18 de 1 d Oe 11 def 22 efg Od 5 cde Snapshot 5.60 kg 0g 2de 8 hij 15 d-h Od 1 e 11 def 24 ef Od 3de Snapshot+ 2.80 kg + 19 b 6cd 20 cd 11 e-j 22 b 19 c 79 a 26 e 21 a 4de Roundup 1.17L

Stomp 3.74 kg 2g 1 de 10 g-j 8 g-j 1 d Oe 7f 14 ij Od 8b-e Stomp 7.47 kg lg 1 de 17 de 15 d-h 1 d 3e 14 de 21 e-h 1 d 3de Stomp+ 3.74 kg+ 20 b 86 a 37 b 83 a 17 b 53 a 68 c 79 b 16 b 68 a Arsenal 4.68 L Surflan 1.75 L 0g 1 de 10 g-i 17def Od 2e 11 def 22e-g 1 d 5 cde Surflan 3.51 L 0g 1 de 6i 4j 1 d 1 e 10 de 11 j Od Oe Surflan+ 1.75 + 18 b 1 de 16 ef 6ij 18 b 21 c 81 a 32 d 14 be 6 cde Roundup 1.17 L Whip 1.56 L 2g 3de 13 e-h 17def Od Oe 14 de 15 ij Od Oe

Whip 3.12 L lg 1 de 10 g-i 8f-j Od 2e 12 de 18 g-i Od Oe Untreated 4fg 2de 8 hi j 6ij Od Oe 11 def 16 hi 1 d 1 e 'Herbicides: Arsenal=imazapyr, Dimension=dithiopyr, Pennant=metolachlor, Post=sethoxydim, Roundup=glyphosate, Snapshot=oryazlin+isoxaben, Stomp=pendimethalin, Surflan=oryzalin, Whip=fenoxaprop-ethyl. 2Metric to English conversions: 1.17, 1.56, 1.75, 2.40, 3.12, 3.51, 4.68, 4.80, 6.24, 9.35,and 18.71 = 16.0, 21.3, 24.0, 33.0, 42.7, 48.0, 64.0, 65.6, 85.4, 128.0, and 256.0 fluid oz/A; 2.80, 3.74, 5.60, and 7.47 kg/ha=40.0, 53.3, 80.0, and 106.7 dry oz/A, respectively. 3Values in columns followed by the same letter are not significantly different at the 5% level using Duncan's multiple range test. Arsenal caused intermediate injury (30 to 33%). Ratings for Dimension, Pennant, Poast, Snapshot, Stomp, Surflan, and Whip applied alone were similar to those of the untreated areas. Five wk after spraying, treatments with Arsenal caused the most vegetative injury (75 to 82%) (Table 1). Roundup alone and with Dimension and Surflan gave intermediate results (28 to 45%). All other treatments were similar to the untreated plots. Two wk after spraying near Somerville, Surflan + Roundup was the most injurious treatment to the two grasses (40 to 44%) (Table 4). Pennant + Roundup was equal with Surflan + Roundup on rescuegrass and only slightly less effective on Japanese brome. The two Arsenal treatments and Roundup either alone or with Dimension were most injurious to Carolina geranium . Treatments with Roundup plus Dimension or Pennant were more effective on California burclover than any other treatment.

At 5 wk, the two Arsenal treatments had caused the most foliar injury (40 to 73%) to the four species rated (Table 4). Roundup alone or in mixtures was generally the second most effective herbicide causing slight injury to all species except Japanese brome. Dimension + Roundup caused slightly increased injury to Carolina geranium and California burclover compared with Roundup alone. The other herbicide treatments had little effect on the vegetation.

18 Table 4. Injury to individual species caused by nine herbicides applied under highway guardrails near Somerville, Texas, on March 5, 1991, and rated 2 and 5 wk later.

Treatment1 Rate2 Plant species3 Rescuegrass Japanese brome Carolina California geranium burclover 2 wk 5 wk 2wk 5 wk 2 wk 5 wk 2 wk 5 wk

Arsenal 4.68 L 16 g 56 b 17 ef 50 a 17 ab 73 a 22 e 64b Dimension 9.35 L 33 cd 0g 1 i Od 12 c 10 ghi 7gh 6i Dimension 18.71 L 34 cd 3efg 22 d Od 6de 22 cde 3hi 12 g

Dimension 9.35 27 e 16 c 26 c ~ 20 a 43 b 49 a 43 c +Roundup + 1.17 L Pennant 2.40 L 30 de 0g Oi Od 6de 13fgh 11 g 2jkl Pennant 4.80 L 0j If Oi 8d 18c-g 18 ef 6ii Pennant+ 2.40+ 46 a 0g 33 b 5cd 13 c 19 c-f 41 b 20 f Roundup 1.17 L Poast 3.12 L 7i 5efg 9h 7de 15e-h Oi 5ijk Poast 6.24 L 34 cd 0g 12 gh Od 8de 8hi 1 i 2 jkl Roundup 1.17 L 21 f 7def 20 de — 17 ab 26 c 37 c 35 d Table 4. (Cont.) Injury to individual species caused by nine herbicides applied under highway guardrails near Somerville, Texas, on March 5, 1991, and rated 2 and 5 wk later.

Snapshot 2.80 kg 38 b Og Oi Od 3e 8 hi 1 i 5ijk

Snapshot 5.60 kg 01 4 efg Oi 5de 12 f-i Oi 4i-l Snapshot+ 2.80 kg+ 12 gh 8de 13 fg Od 14 be 24 cd 33 cd 26 e Roundup 1.17 L

Stomp 3.74 kg Oj Og 1 Oi Od 8de 15 e-h 5 hi 10 gh

Stomp 7.47 kg 35 be 2fg Oi Od 7de 17d-g 1 i 8 hi

Stomp+ 3.74 kg+ 9 hi 69 a 14 fg 40 b 19 a 70 a 16 f 73 a Arsenal 4.68 L

Surflan 1.75 L Oj 3 efg Oi 2cd 5de 14 e-h Oi 1 kl i

Surflan 3.51 L Oj lg Oi Od 3de 19c-f Oi 6ii

Surflan+ 1.75 + 1.17 44a 12 cd 40a — 14 be 26 c 32 d 28 e Roundup L

Whip 1.56 L Oj 5g Oi Od 3e 12 f-i Oi 6ij

Whip 3.12 L 14 g 8de 17 ef 10 c 6de 5i Oi 4i-l

Untreated Oj Og Oi Od 5de 17d-g 1 i 01 'Herbicides: Arsenal=imazapyr, Dimension=dithiopyr, Pennant=metolachlor, Post=sethoxydim, Roundup=glyphosate, Snapshot=oryazlin 4-isoxaben, Stomp=pendimethalin, Surflan=oryzalin, Whip=fenoxaprop-ethyl. 2Metric to English conversions: 1.17, 1.56, 1.75, 2.40, 3.12, 3.51, 4.68, 4.80, 6.24, 9.35,and 18.71 = 16.0, 21.3, 24.0, 33.0, 42.7, 48.0, 64.0, 65.6, 85.4, 128.0, and 256.0 fluid oz/A; 2.80, 3.74, 5.60, and 7.47 kg/ha=40.0, 53.3, 80.0, and 106.7 dry oz/A, respectively. 3Values in columns followed by the same letter are not significantly different at the 5% level using Duncan's multiple range test. DISCUSSION

This discussion presents response ratings for both the overall whole plot and for the most frequently occurring individual species. From the management standpoint, overall whole plot ratings are the most useful in that they are easier to make, and they integrate the effects on all species, especially those like the grasses which naturally grow the largest. Individual plant ratings, however, are useful where the species is large and/or occurs as the most frequent invader. The most effective herbicide through 2 wk after spraying, and sometime through 4 or 5 wk, was Roundup. Because almost all vegetation had emerged prior to spraying, Roundup was the most effective herbicide. Roundup affects the vegetation through foliage within 1 wk but has little residual activity. Consequently, vegetation generally started to reinvade the area by 10 wk after spraying at Kerrville, and probably at the other sites as well. Vegetation response to mixtures with Roundup varied somewhat. However, for the most part, vegetation response was not much different from the treatment of Roundup alone, indicating that there was little additive or interacting effect. Arsenal was generally the most effective herbicide at the 5 and 10 wk ratings. Arsenal enters both the foliage and roots and has an extended residual life span in the soil. By 10 wk, almost all vegetation was dead at Kerrville. Although not rated at 10 wk, plots at Somerville seemed to respond similarly to that at Kerrville. Ground spurge was the first species to reinvade the Arsenal plots at Somerville. Long-term ratings were not taken because the guardrails were oversprayed with Roundup to control spring vegetation.

21 Arsenal has promise for winter annual vegetation control. It is reasonably fast acting, basically non-selective, and provides residual control through the soil. Further research could delineate the most ideal dosage to control vegetation until invasion by summer vegetation occurs requiring another herbicide treatment such as with Roundup. Guardrail sprays are generally applied to overpasses, bridges, and steep drop-offs which are usually some distance away from woody vegetation. Arsenal has some effect on woody vegetation, especially deciduous species. Therefore, Arsenal should not be used within 30.5 m (100 ft) of desirable woody vegetation, such as might occur particularly at Lufkin and Somerville.

The other herbicides generally showed little promise for use under the conditions of these experiments as shown by whole plot treatment ratings for these herbicides that were not different from the untreated plots (Table 1). Earlier spraying did not seem to be useful because the vegetation, especially at Kerrville, was small and did not present an aesthetic problem. Most vegetation, particularly at Somerville, had already emerged at time of spraying. In this study, therefore, these herbicides seemed to have little preemergence capability.

Another reason for lack of control by herbicides having all or mostly preemergence activity was limited rainfall, particularly at Lufkin and Kerrville. Lufkin had about 15 and 53 mm (0.6 and 2.1 inches) accumulative rainfall 2 and 5 wk after spraying, respectively. Somerville had about 38 and 132 mm (1.5 and 5.2 inches) after 2 and 5 wk, respectively. Kerrville had 8, 15, and 91 mm (0.3, 0.6, and 3.6 inches) after 2, 4, and 10 wk, respectively.

A number of treatments other than those with Arsenal and Roundup did, however, cause some statistical injury increases to individual species compared with the untreated plots. Using an increase of 15% over the untreated plots as a standard, Poast reduced prairie bishop at 5 wk at Lufkin. Near Somerville at 2 wk, Dimension at 18.71 L/ha (256 oz/A) reduced rescuegrass and Japanese

22 brome, and Pennant at 4.8 L/ha (85.4 oz/A) reduced California burclover. Poast at 6.24 L/ha (85.4 oz/A) and Snapshot at 2.80 kg/ha (40 oz/A) reduced rescuegrass, and Whip at 3.12 L/ha (42.7 oz/A) reduced Japanese brome. None of the species were injured 15% or more above the untreated plots at 5 wk after treatment. At Kerrville, at least one rate of Poast, Stomp, and Surflan injured rescuegrass at 10 wk; Dimension, Pennant, Poast, Snapshot, Surflan, and Whip injured Japanese brome, mostly at 10 weeks; and Poast at 5 wk and Snapshot at 10 wk injured California burclover.

Arsenal holds promise for controlling vegetation either pre- or postemergence under guardrails beginning in the winter. Roundup is useful for early post-emergence spraying before summer spraying regimes are started.

23 REFERENCES

Anonymous. 1991. Vegetation management standards. Chapter 3-Herbicide Operations. State Dep. Highways and Public Trans. Austin, TX. 14 pp. Barrett, M., and G.L. Olson. 1985. Critical rainfree periods for postemergence johnsongrass control. Proc. South. Weed Sci. Soc. 38:453. (Abstract). Colby, S.R., E.R. Hill, L.M. Kitchen, R.G. Lynn, W.J. McAvoy, and R. Prasad. 1989. Herbicide Handbook of the Weed Science Society. 6th ed. Weed Sci. Soc. Amer. Champaign, IL. Dutt, T.E., S.H. Bundschuh, N.E. Jackson, D.C. Riego, and K.E. Kackley. 1990. Dimension® (MON-15151) turf herbicide update. Proc. South. Weed Sci. Soc. 43:390. (Abstract). Enache, A.J., and R.D. Ilnicki. 1991. BAS 514 and dithiopyr for weed control in cool-season turfgrasses. Weed Technol. 5:616-621. Evans, J.R., E.C. Ellison, C. Finley, J.S. Hardin, and J.L. Lloyd. 1987. Sethoxydim for seedhead suppression of tall fescue. Proc. South. Weed Sci. Soc. 40:268. (Abstract). Grant, D.L., R.B. Cooper, and H.L. Webster. 1990. Isoxaben for broad- spectrum weed control in warm season turf. Proc. South. Weed Sci. Soc. 43:145. (Abstract). Hatch, S.L., K.N. Gandhi, and L.E. Brown. 1990. Checklist of the vascular plants of Texas. Tex. Agric. Exp. Stn. Misc. Pub. 1655. 158 pp. Higgins, J.M., S.H. Bundschuh, T.E. Dutt, and N.E. Jackson. 1991. Winter weed control in turf with dithiopyr. Proc. South. Weed Sci. Soc. 44:179. (Abstract). Jacgschitz, J.A., and CD. Sawyer. 1989. Preemergence control of crabgrass, spurge and oxalis and pre-post, post control of crabgrass in turf. Proc. Northeast. Weed Sci. Soc. 43:96-97.

25 Johnson, B.J., and G.O. Ware. 1978. Dates of glyphosate treatments on weeds and bermudagrass (Cynodon dactylon). Weed Sci. 26:523-526. Kackley, K.E., D.C. Riego, T.E. Dutt, S.H. Buchschuh, and N.E. Jackson. 1990. MON 15151-turf herbicide: experimental use permit update. Proc. Northeast. Weed Sci. Soc. 44:37-38. Montgomery, D.P., M.P. Kenna, and L.M. Cargill. 1989. Growth regulation of bermudagrass on Oklahoma rights-of-way. Proc. South. Weed Sci. Soc. 42:251. (Abstract). Patterson, D.T. Chairman. 1989. Composite List of Weeds. Weed Sci. Soc. Amer. Champaign, IL. Thomson, W.T. 1986. Agricultural Chemicals-Book II Herbicides. Thomson Publ., Fresno, CA. 301 pp. Transportation Research Board. 1988. Use of herbicides in roadside maintenance. Prepared by W.D. Johnson, Chairman, Roadside Maintenance Comm. Trans. Res. Circ. 342. 27 pp. VanCantfort, A.M., J.C. Rabby, A.R. Hegman, and J.C. Dunn. 1985. Arsenal® herbicide update: new species controlled, forestry and grass release. Proc. South. Weed Sci. Soc. 38:356. (Abstract).

26 APPENDIX A

Chemicals Used in Guardrail Study

Tradename Common name Chemical name

Arsenal Imazapyr (±)-2-[4,5-dihydro-4- methyl-4-( 1 -methy lethyl)- 5-oxo-l H-imidazol-2-yl]- 3-pyridinecarboxylic acid

Dimension Dithiopyr S,S-dimethyl 2- (difluoromethyl)-4-(2- methylpropyl)-6- (trifluoromethyl)-3,5- pyridinedicarbothioate Oust Sulfometuron methyl 2-[[[[(4,6-dimethyl-2- pyrimidinyl)amino]carbon yl]amino]sulfonyl] benzoic acid

Pennant Metolachlor 2-chloro-N-(2-ethyl-6- methylphenyl)-N-(2- methoxy-1 -methylethyl) acetamide

Poast Sethoxydim 2-[1-(ethoxyimino)butyl]- 5-[2-(ethylthio)propyl]-3- hydroxy-2-cyclohexen-1- one

Roundup Glyphosate N-(phosphonomethyl) glycine

27 Snapshot Oryzalin + Isoxaben 4-(dipropylamino)-3.5- dinitrobenzene = sulfonamide + N-[(3-(1 -ethyl-1 - methylpropyl)-5- isoxazolyl]-2,6- dimethoxybenzamide

Stomp Pendimethalin N-(1-ethylpropyl)-3,4- dimethyl-2,6- dinitrobenzenamine

Surflan Oryzalin 4-(dipropylamino)-3,5- dinitrobenzene = sulfonamide

Whip Fenoxyaprop-ethyl (±)-ethyl 2-[4-[(6-chloro- 2-benzoxazolyl)oxy] = phenoxylpropanoate

28 APPENDIX B

Species in Guardrail Study

Annual bluegrass Poa annua L.

Bahiagrass Paspalum notatum Fluegge

Bermudagrass Cynodon dactylon (L.) Pers.

Buckhorn plantain Plantago lanoeolata L.

California burclover Medicago polymorpha L.

Carolina geraniumn Geranium carolinanum L.

Crabgrass Digitaria sp

Common chickweed Stellaria media (L.) Vill.

Common vetch Vicia sativa L.

Corn Zea mays L

Dandelion Tarxanum offininale Weber in Wiggers

Foxtail Setaria sp

Goldmane coreopsis Coreopsis basalis (Dietr.) Blake

Goosegrass Eleusine indica (L.) Gaertn.

Henbit Lamium amplexicaule L.

Hop clover Trifolium aureum Pollich

Japanese brome Bromus japonicus Thunb. Ex Murr.

Johnsongrass Sorghum halepense (L.) Pers.

Jointed goatgrass Triticum cylindrica Host

29 Kentucky bluegrass Poa pratensis L.

Lambsquarters Chenoporiium sp

Large crabgrass Digitaria sanguinalis (L.) Scop.

Lespedeza Lespedeza sp

Morningglory Ipomea sp

Perennial ryegrass Lolium perenne L.

Prairie bishop Bifora amerinana Benth. & Hook, ex S.

Prostrate spurge Euphorbia humistrata Engelm. ex Gray

Purslane Portulaca sp

Ragweed Amhrosia sp

Rescuegrass Bromus catharticus Vahl

Shepherds-urse Capsella hursa-pastoris (L.) Medicus.

Tall fescue Festuca arundinanea Schreb.

Wild oats Avena fatua L.

Yellow woodsorrel Oxalis stricta L.