AGRICULTURAL EXPERIMENT STATION R. DENNIS ROUSE, Director DECEMBER 1977 AUBURN UNIVERSITY AUBURN, ALABAMA CIRCULAR 239 Control of Buttercup in Dallisgrass- Clover Pastures in Alabama h ---- 4 . SN N e 44 r "S cl 4L ;i As; CONTENTS Page EXPERIMENTAL PROCEDURES....................3 Field Experiments.............................3 Greenhouse Experiments.........................4 Laboratory Experiments.........................4 RESULTS.....................................5 SUMMARY AND, CONCLUSIONS ..................... 9 LITERATURE CITED........................... APPENDIX................................... 10 11 First Printing 4M, December 1977 Information containedherein is available to all without regard to race, color, or national origin. Control of Buttercup in Dallisgrass-Clover Pastures in Alabama C. Wayne Smith, G. C. Weed, C. C. King, G. A. Buchanan, L. A. Smithl/ WEEDS IN PASTURES compete with forages for nutrients and sunlight thereby decreasing the production of desirable forage plants. Animals may also be forced to graze selectively and expend more energy obtaining forage. There are at least 19 species of "buttercup" (Ranunculus spp.) found in the Southeastern United States (12). Two species, R. abortivus L. and R. sardous Crantz, occur in the pastures of the Black Belt region of central Alabama. These weeds are winter annuals and therefore compete with white clover in dallisgrass-white clover (Paspalum dilatatum Poir. and Trifolium repens L.) mixtures at a time when forage production is critical. Several Ranunculus species are reported to cause livestock poisoning (3, 4, 5, 11). Although actual feeding trials have not indicated that these plants are poisonous, a toxic irritant, ranunculin, has been isolated from Ranunculus plants (2, 6, 7,9). Ranunculus abortivus and Ranunculus sardous are winter annuals, usually 6 to 25 inches tall, with kidney shaped basal leaves and stem leaves divided into three segments. Flowers are yellow, while the mature seeds are brownish. R. abortivus seed are somewhat flattened with a slight beak or protrusion (12). R. sardous seed are round with a rim extending around the seed, and covered with small wart-like protrusions. Ranunculus sardous is controlled by MCPA (see Appendix table 1 for chemical names), MCPB, 2,4-D, or combinations of these (1). It is difficult to control buttercup in dallisgrass-white clover pastures without damaging the white clover, which is injured by phenoxy-type herbicides. The objectives of the studies reported herein were to determine the effectiveness of selected herbicides in control of buttercup and the tolerance of white clover to these herbicides. EXPERIMENTAL PROCEDURES Field Experiments Experiments were conducted at the Black Belt Substation, Marion Junction, Alabama, in 1970, 1971, 1975, and 1976 to determine the effectiveness 1Former Graduate Assistant, now Assistant Professor, University of Arkansas; former Research Associate, now with Chemagro Corp; Professor, Alumni Professor, Department of Agronomy and Soils, and Black Belt Substation Superintendent, respectively. of herbicides for the control of buttercup. A randomized complete block design with four replications was used in all experiments. Treatments were applied to an established pasture that was heavily infested with buttercup. Other species present included dallisgrass, white clover, primrose, and johnsongrass. Herbicides were applied broadcast in 15 to 25 gallons of water per acre with either a hand or tractor mounted sprayer. Plots were 5 x 25 feet in 1970 and 1971 and 12 x 20 feet in 1975 and 1976. Surfactant WK® was added to all spray mixtures at 0.5% v/v. Experiments were also conducted on the same area to determine the optimum herbicide application date for control of buttercup. An experimental design similar to that described above was used. Treatments were evaluated by ratings and plant counts. Greenhouse Experiments Experiments were conducted in the greenhouse to determine the tolerance of established Regal-Ladino white clover to different formulations and rates of 2,4-D. Clover was grown in 8-inch pots in a conventional greenhouse potting mixture. Herbicides were applied as described for field experiments except that a conveyor belt sprayer was used. Dry matter yield of clover was used as an indicator of the effect of the herbicide. Plants were harvested 28 days after treatment and at 2-week intervals thereafter for a total of three harvests. Laboratory Experiments Hand-harvested Ranunculus seed were used to determine the conditions necessary for germination. The influence of mechanical scarification, temperature and germination medium was evaluated. Mechanical scarification consisted of mechanically scarifying seed for different periods of time. Temperatures were established in controlled cabinets ranging from 50 to 73°F and germination medium was either water or KNO3 water solution. Experiments were conducted in petri dishes using 100 seed per dish. Seed were kept in darkness except when being watered (usually after 5 days) and counted. Germinated seed were counted on the seventh day and every other day thereafter, through the seventeenth day. The effect of 2,4-D amine on the water soluble sugar content of mature buttercup was determined since 2,4-D has been shown to increase the sugar content of some plants. If this were the case with buttercup, then cattle might find the weed more palatable and consequently consume it in greater amounts. The entire above ground portion of the plant was used for analysis. The water soluble sugars were extracted by the method outlined by Smith, et al. (13) and the content was then determined by the anthrone reagent method described by Morris (10). [4] The protoanemonin-phenylhydrazone complex procedure outlined by Mahran, et al. (8), was used to determine the ranunculin content of the two species being studied. Plants from the Black Belt Substation and from Montgomery County, Alabama, were evaluated. RESULTS Results of the experiment initiated in April 1970 revealed substantial control of buttercup by the dimethyl amine salt and the butyl ester formulation of 2,4-D, table 1. These experiments indicated that essentially no control was obtained with later application when pastures were not grazed or clipped before the application of the herbicides. In the fall 1970 and winter-spring 1971 experiments, excellent control of buttercup was obtained with application of 2,4-D amine in November or January at rates as low as 0.25 lb./A. When treatment was delayed until late March, a higher rate of 2,4-D amine was required to obtain acceptable con- TABLE 1. CONTROL OF BUTTERCUP, BLACK BELT SUBSTATION, MARION JUNCTION, ALABAMA, 1970 Treatment Herbicide and formulation 2,4-D, dimethyl amine salt....... 2,4-D, dimethyl amine salt. ...... 2,4-D, dimethyl amine salt. ..... Rate/acre active ingredient Lb. 0.5 1.0 2.0 0.5 1.0 2.0 0.5 1.0 .. 0.5 1.0 0.5 1.0 0.2 0.4 0.8 - Date herbicide applied April 3 April 30 Pct. control Pet. control 781/ abcd2/ 90 abc 95 ab 73 88 98 50 75 48 60 15 55 10 35 48 0 abcde abc a de abcde de cde fg de fg ef de g 25 abcd 43 a 40 ab 30 abcd 22 abcd 30 abcd 10 bcd 25 abcd 13 abcd 12 bcd 20 abcd 7d 22 abcd 10 bcd 32 abc 0 d 2,4-D,butyl ester ............ 2,4-D, butyl ester ....... . . .. 2,4-D, butyl ester ... . . . ...... 2,4-D, iso-octyl ester ... . . ..... 2,4-D, iso-octyl ester .......... 2,4,5-T, butyl ester .. 2,4,5-T, butyl ester.. . . ...... ... . .. 2,4,5-T, oleyl diamine salt ...... 2,4,5-T, oleyl diamine salt ....... dicamba.................... dicamba..................... dicamba................... control (untreated). . . . . ...... 1/0 = no control; 100 = complete control of buttercup. Ratings made approximately 4 weeks after application. 2/Numbers within a column followed by the same letter are not significantly different at the .01 level of probability. [5] TABLE 2. EFFECTIVENESS OF 2,4-D AMINE IN CONTROLLING BUTTERCUP WHEN APPLIED AT 3 DIFFERENT TIMES. BLACK BELT SUBSTATION, MARION JUNCTION, ALABAMA, 1970 AND 1971 Date of herbicide application Rate/acre 13 29 31 Treatment active ingredient November January March Herbicide and formulation Lb. Pct. control Pct. control Pct. control 2,4-D, dimethyl amine salt ..... 2,4-D, dimethyl amine salt. .... 2,4-D, dimethyl amine salt ..... Control (untreated). ........ 0.25 0.50 1.00 0 851/ 88 100 0 b/ b a c 100.0 100.0 100.0 0 a a a b 57.5 77.5 90.0 0 c b a d 1/0 = no control; 100 = complete control of buttercup. Ratings were made approximately 4 weeks after application. 2/Numbers within column followed by the same letter are not significantly different at the .01 level of probability. trol, tables 2 and 3. Control was obtained using only 0.25 lb./A. in January despite below freezing temperatures for two nights following treatment, table 4. Results of experiments initiated in April 1975 indicated that acceptable control resulted with treatment of 2.0 lb./A. of 2,4-D amine or dicamba + 2,4-D at 0.5 + 1.5 lb./A., table 5. Effective control of buttercup was obtained with each formulation of 2,4-D in 1976, table 6. Dicamba was ineffective even at rates as high as 1.0 lb./A. All of the above treatments were substantially more effective in 1976 than in 1975. The dicamba + 2,4-D mixture included in the 1976 experiment was highly effective at rates as low as 0.12 + 0.37 lb./A. Bentazon and metribuzin also were included as foliar treatments in 1976. Metribuzin was TABLE 3. NUMBER OF BUTTERCUP PRESENT PER SQUARE FOOT BEFORE AND AFTER THE NOVEMBER 13 APPLICATION DATE Rate/acre Treatment active ingredient Herbicide and formulation Lb. 2,4-D, dimethyl amine salt..... 2,4-D, dimethyl amine salt..... 2,4-D, dimethyl amine salt. ... 0.25 0.50 1.00 Time of count Number of plants ft 2 plants/ft 2 341/ 2 51 2 39 1 37 29 b a b a b a b b Control (untreated)......... .0 Before Nov., 1970 After April, 1971 Before Nov. 1970 After April, 1971 Before Nov., 1970 After April, 1971 Before Nov., 1970 After April, 1971 1/Numbers in column followed by the same letter are not significantly different at the .01 level of probability. [6] DAYS TABLE 4. DAILY MAXIMUM AND MINIMUM TEMPERATURES FOLLOWING EACH APPLICATION OF 2,4-D AMINE, BLACK BELT SUBSTATION, MARION JUNCTION, ALABAMA FOR 7 Nov. 13, 1970 Day Max. F Min. F Jan. 29, 1971 Max. F Mn. March 31, 1971 Max. Min. F 0F0F 23 31 40 23 23 27 43 74 71 71 61 68 70 59 1 .......... 57 2 .......... 62 3 ..... ..... 58 4..........47 5 ......... 48 6 .......... 56 7 .......... 69 39 42 43 30 24 25 47 55 -68 73 47 43 44 54 37 42 44 33 33 38 36 ineffective at rates below 1.0 lb./A. whereas bentazon effectively controlled buttercup at rates as low as 1.0 lb./A. Greenhouse results indicated that Regal Ladino white clover will withstand low rates of 2,4-D amine, butyl ester, and iso-octyl ester if application is delayed until. after stolon development. Over all harvests, treatment with TABLE 5. CONTROL OF BUTTERCUP WITH SELECTED HERBICIDE APPLIED MARCH 5, 1975 AND CONTROL ESTIMATES MADE APRIL 2, 1975, BLACK BELT SUBSTATION, MARION JUNCTION, ALABAMA Treatment Herbicide and formulation Rate/acre active ingredient Lb. Control Pct. 2,4-D dimethyl amine........... 2,4-D dimethyl amine........... 2,4-D dimethyl amine........... 0.25 0.50 1.00 2,4-D dimethyl amine ........... 2,4-D iso-octyl ester............ 2,4-D iso-octyl ester............ dicamba +2,4-D.............. 0.50 .1.00 0.12 0.25 0.50 1.00 2.00 33 95 50 3 o1/ e?/ e bc a de 10 0 dicamba +2,4-D.............. dicamba + ...... dicamba + 2,4-D............... 2,4-D ......... 0.12+0.37 0.25 +0.75 0.50 +1.50 b e .......... ...... dicamba .... ... ............ dicamba .... ... .......... dicamba ....... dicamba.................... 1.00 +3.50 45 85 100 b a a 0 0 0 0 e e e e control (untreated) ........................... e 1/0 = no control; 100 = complete control of buttercup. 2/Numbers within a column followed by the same letter are not significantly different at the .01 level of probability. [7] TABLE 6. CONTROL OF BUTTERCUP WITH SELECTED HERBICIDES, BLACK BELT SUBSTATION, MARION JUNCTION, ALABAMA, APRIL, 1976 Treatment Herbicide and formulation Rate/acre active ingedient Lb. Control Pct. 2,4-D, dimethyl amine........... 2,4-D, dimethyl amine............. ........ 2,4-D, dimethyl amine. ......... 2,4-D, dimethyl amine. .0.56 2,4-D,iso-octylester ......... . 2,4-D, iso-octylester ......... dicamba + 2,4-D............. dicamba + 2,4-D.................0.25 dicamba + 2,4-D.................0.50 dicamba + 2,4-D................. dicamba ................... dicamba.....................025 dicamba ................. dicamba .. ............... 2,4-DB, amine................... .. 2,4-DB, amine.................. ... 2,4-DB, amine.............. bentazon ..................... bentazon ..... ......... . ....... metribuzin . ........ metribuzin....................0.50 . metribuzin ............... control (untreated) . 0.28 0.56 1.12 2.24 1.12 0.12 + 0.37 + 0.75 + 1.50 901/ ab2/ 90 93 73 88 99 100 99 ab a abc ab a a a 100 99 1.00+3.50 0.12 0.50 1.00 0.25 0.50 1.00 1.00 2.00 0.25 1.00 20 41 23 a a fg fg def cde 56 81 90 96 90 90 35 45 abc ab 1/o 650 a ab ab ef f bcd g = no control; 100 = complete control of buttercup. Ratings were made approximately 4 weeks after application. 2 /Numbers within a column followed by the same letter are not significantly different at the .01 level of probability. 0.50 lb./A. of these formulations reduced dry weight yield of white clover 30 to 40 percent, while 0.25 lb ./A. of the amine formulation reduced yield 20 percent. Higher rates reduced yield more, but rates as high as 1.0 lb./A. did not destroy the stand of clover, table 7. Germination experiments indicated that buttercup seed germinate well at temperatures of 62 to 73°F. However, since scarification of seeds was required for good germination, a hard seedcoat is indicated. This is considered to support previous work (1) indicating that application of herbicides for more than 1 year will be required to eliminate buttercup as a problem weed in pastures. The amine formulation of 2,4-D when used at rates up to and including 1.0 lb ./A. did not increase water soluble sugar content of above ground parts of the two buttercup species; therefore, no selective grazing of herbicide treated buttercup would be expected and cattle could be safely returned to [8] TABLE 7. YIELD OF ESTABLISHED REGAL LADINO WHITE CLOVER FOLLOWING APPLICATION OF 2,4-D Yield as percent of untreated control Rate/acre First Second Third Total Treatment active ingredient harvest harvest harvest yield Herbicide and formulation Lb. Pct. Pct. Pct. Pct. 2,4-D dimethyl amine salt .. 2,4-D dimethyl amine salt .. 2,4-D dimethyl amine salt .. 2,4-D dimethyl amine salt .. 2,4-D butylester ....... 2,4-D butyl ester ....... 2,4-D butyl ester ....... 2,4-D iso-octyl ester...... 2,4-D iso-octyl ester ..... control (untreated) .......... 0.25 0.50 1.00 2.00 0.50 1.00 2.00 0.50 1.00 82 63 49 47 67 49 39 55 55 100 abl/ bcd cd cd bc cd d cd cd a 74 63 37 23 83 40 29 74 63 100 b b c c ab c c b b a 83 42 25 8 67 17 8 67 50 100 ab bc c c abc c c abc abc a 80 61 44 38 71 44 34 61 57 100 b bcd defg fg be defg g bcde cdef a 1/Values within each column followed by the same letter are not significantly different at the .01 level of probability. treated pastures within a few days. Also, the ranunculin compound was found only in trace amounts. SUMMARY AND CONCLUSIONS Both species of buttercup were controlled with selected formulations of 2,4-D, dicamba + 2,4-D, and bentazon. Generally, the older the buttercup plants (or the later in the spring when herbicides are applied) the higher the rate of herbicide required for control. In these experiments effective control was obtained with late fall or winter application of 2,4-D amine provided there is sunshine and moderately warm (60'F) temperatures at application time. While rates of 2,4-D as low as 0.25 lb./A. gave effective control of buttercup in some experiments, consistent control could be expected with an application rate of 0.5 lb./A. This rate of 2,4-D amine should selectively control buttercup on established white clover. Because buttercup seed has a hard seedcoat, a 3-to 4-year intensive spray program will probably be required to eliminate buttercup as a problem weed in pasture. [9] LITERATURE CITED (1) ANONYMOUS. 1969. Technical bulletin of the Bio-Products Division of Ivon-Watking-Dow-Ltd. New Plymouth, New Zealand. (2) BREDENBERG, J. B.-SON. 1961. Conformation of the Structure of Ranunculin. Suomen Kemistilehti 34B:80-82. (3) CORBETT, R. B. 1942. Poisonous Plants of Maryland in Relation to Livestock. Md. Agr. Exp. Sta. Bull. A-10. pp. 268-269. (4) FREEMAN, JOHN D. AND HAROLD D. MOORE. 1974. Livestock-Poison- ing Vascular Plants of Alabama. Auburn University, (Ala.) Agr. Exp. Sta. Bull. 460. 80 pages. (5) GUNNING, O. V., DVM. 1949. Suspected Buttercup Poisoning in a Jer- sey Cow. Brit. Vet. J. 105:393. (6) HIDIROGLOU, M. AND H. J. KNUTT. 1963. The Effects of Tall Green Buttercup in Roughage in the Growth and Health of Beef Cattle and Sheep. Can. J. Animal Sci. 43:68-71. (7) HILL, R. AND RUTH VAN HEYNINGEN. 1951. Ranunculin: the Pre- cursor of the Vesican Substance of the Buttercup. Biochem. J. 49:332335. (8) MAHRAN, G. H., A. HIFNY SABER, AND T. EL-ALFY. 1968. Spectro- photometric Determination of Protoanemonin, Anemonin, and Ranunculin in Ranunculus scleratus L. Planta Medica 16:323-328. (9) MORAN, EDWARD A. 1956. Feeding of Small Flowered Buttercup not Noticeably Poisonous to a Steer and Sheep. Am. Vet. Med. Assn. J. 129:426. (10) MORRIS, D. L. 1948. Quantitative Determination of Carbohydrates with Dreywood's Anthrone Reagent. Science 5:254-255. (11) PAMMEL, L. H. 1929. Buttercup or Crowfoot Poisoning. Vet. Med. 24:540. (12) RADFORD, A. E., H. E. AHLES AND C. R. BELL. 1968. Manual of the Vascular Flora of the Carolinas. University of North Carolina Press. pp. 462466. (13) SMITH, D., G. M. PAULSEN AND C. A. RAGUSE. 1964. Extraction of Total Available Carbohydrates from Grass and Legume Tissue. Plant Physiol. 39:960-962. [10] APPENDIX TABLE 1. CHEMICAL, COMMON, AND TRADE NAMES OF HERBICIDES INVESTIGATED Common MCPA . . .. Chemical [(4-chloro-o-tolyl)oxy] acetic acid.....................Several butyric acid....................Several Trade MCPB..4-[4-chloro-o-tolyl)oxy] Several ... ....... 2,4-D...(2,4-dichiorophenoxy) acetic acid ... . ...... .. .Banvel .......... dicamba. . .3,6-dichloro-o-apisic acid........ ..... Sencor, Lexone metribuzin. .4-aniino-6-tert -butyl-3-(methylthio)-astriazin-5(4H)-one bentazon . .. 3isopropyl-1H-2, 1,3-benzothiadiazin-(4) as-triazin 3H-one 2,2-dioxide.. . Basagran ALBURN UlNIVERSIY With an agricultural research unit in every major soil area, Auburn University serves the needs of field crop, livestock, forestry, and horticultural producers in each region in Alabama. Every citizen of the State has a stake in this research program, since any advantage from new and more economical ways of producing and handling farm products directly benefits the consuming public. 0 , 0 O 00 ® ® * C 0 Research Unit Identification 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 16 19 20 Tennessee Valley Substation Belle Mina Sand Mountain Substation Crossville North Alabama Hort culture Substation, Cullman Upper Coastal Pain Substation, Winfield Forestry Unit Fayette County Thorsby Foundation Seed Stocks Farm Thorsby Chilton Area Horticuiture Substation Cianton Forestry Unit, Coosa County Piedmont Substation. Camp Hill Plant Breeding Unit. Tallassee Forestry Unit Autauga County Prattville Experiment Field, Prattville Black Belt Substation. Marion junction Lower Coastal Plain Substat on Camden Forestry Unit Barbour County Monroevi e Exper iment Field Monroeville W regrass Substation Headland Brewton Exper ment Field. Brewton Ornamental Horticulture Field Station. Spring Hill Gulf Coast Substation, Fairhope