EEDS
`
`JOURNAL OF
`
`�3()
`THE WEED SOCIETY OF AMERICA
`
`Poge
`
`CONTENTS
`.
`A Technique
`for Studying
`Weed Competition
`in Forage Legume Eatabliahment.
`Marvin M. Schreiber
`. . . . . . . . . .
`. • . . . . . • . . . • • . . . . . . . . • • • . . . . . . • . . . • . . . • • • • . • • .
`©
`Water Lettuce-Nature,
`Problem,
`and Control.
`Lyle W. Weldon and Robert D.
`Blackburn
`.. .. .. .. .. .. . . .. .. .. . .. . . .. .. . 5
`.. . .. . .. .. . . . . .
`.. . .. . .. . .. . . .
`.. . . . .
`Elfect of Moisture
`Streu on Absorption
`and Movement
`of Picloram
`and 2,4.S•T
`in
`Beans. M. G. Merkle and F. S. Davia . . . . . . . . . . • . . . • . . • . . . . . . . . • . . . . . . . . . . . .
`10
`Anenic Translocation
`in Nutaedge
`Tuber Systems
`and its Effects on Tuber Vi•
`and C. G. McBee • • • . • . . .
`13
`ability.
`Ethan C.
`Holt, J. L. Faubion,
`W. W. Allen,
`Control of Jobmon�ss in Corn. Raymond D. Hicks and 0. Hale Fletchall
`. . 16
`• . . .
`Calculating
`Synergistic
`and Antagonistic
`Reaponsea
`of Herbicide
`Combinatio111.
`S. R. Colby • • • • . . . . . . . . . . . . . . • . . . . . . . . . . . . . . . . . . . . . . . • . . . . . . • . • . . . . . . . . • . . .
`!O
`Seasonal
`Variation
`in Sprouting
`and Available
`Carbohydrate
`in Yellow Nutaedge
`Tubers.
`R.. B. Taylonon . • . . . . . • . . . . . . . . . . . . . . . . . . . . . . . . . . . . • • . . . . . . . . . . . .
`22
`Height Differential
`of Com and Giant Foxtail
`in Relation
`to Poatemergence
`Weed
`Control. Ellery
`L. Knake and Fred W. Slife . . .
`.. . . . . .
`.. .. . .. • . .
`.. . . . • • . • •
`.. • 24
`Silver
`Dollar Fish for Biological
`Control
`of Submened Aquatic
`Weeda. R. R.
`Yeo •••.••••.••.•...••••••••••••••••••.•••••••••••••••.••••••.•••••••••••••
`rt
`of Simazine. Qn Chloroplast Ribonucleic Acid,
`Influence
`and Protein
`Metabolism.
`R. P. Singh'1nlaS.
`H. West . . . . . • . . . . . . . . . . . . . . . . . . . . . • . • . . . . . . . . . . . . • . . . . . •
`31
`Extraction
`and Determination
`of Atrazine
`from Soil. Manha} D. McGlamery,
`35
`Fred W. Slife,
`and Harold Butler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
`Vegetation
`Control
`Along Fence Unes with Maleic Hydrazide.
`L. E. Foote and
`. . S8
`B. F. Himmelman
`. . . . . . . . . . . . . . . . . .
`.. . . . . . .
`.. . . . • . . . . . . • . • . . . . . . . . . . . . . . .
`Dissipation
`of Diquat and Paraquat,
`and Effects on Aqua,tic Weeds and Fish.
`R.R. Yeo ..............................................
`...................
`42
`Influence
`of Environment
`on Shoot Growth and Total Carbohydrate
`Reserves of
`Saltcedar.
`Eugene E. Hughes . . . . . • . . . . . • . . . . . . . . • . . . • . . • . . . . . • . . . . . . . . • . . . .
`46
`Wheatgrass Establiahment
`with Paraquat
`and Tillage
`on Downy Brome
`Ranges.
`E. Eckert, Jr., and Burges L. Kay . . • . . • . . . • • . . •
`Raymond A. Eva111, Richard
`!SO
`Histological Abnormalities
`Induced
`by Picloram on Canada Thistle
`Roots. Lester
`B. Kreps and Harold P. Alley . .. .. . . .. .. . . .
`.. . . .. . .. . .. .. .. .. .. . . .. .. .. .. .. 56
`60
`Evaluation
`of Herbicide-Impregnated
`Cloth. L. L. Danielson
`. . • . . . . . . . . . . . . . . .
`Chemical Control
`of Three Chihuahuan
`Desert Shrubs.
`Ervin M. Schmutz . . . . . .
`62
`..Jfuteractio111
`of Several
`Paraquat-Surfactant
`M�ures. L. W. Smith and
`C. L. Foy fr1
`f'Toxidty of DSMA Soil Residues to Cotton and Rotational
`Crops. E. E. Schweuer
`72
`R. Johnson,
`Arsenic Residue
`Studies on Coastal
`Bermudagrass.
`G. G. McBee, P.
`and E. C. Holt . . . . . . . . . . . . . . . . . . . . . . . • . . . . . . • . . . . . . . . . . . . . . . . . . . . • • . . . . . . .
`77
`Brief Papen:
`Toxicity of Root Residues of Weed Grass Species.
`Marvin M. Schreiber
`and J.
`L. Williama,
`Jr. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . • . . . . . . . . . . . . . . . . . . . • . • .
`80
`J. Hopen 82
`Respo111e of Bentgrass to Siduron.
`Walter E. Splittstoesser
`and Herbert
`The Influence
`of DMPA on Peanut Yields.
`Ellis W. Hauser . . . . . . . . . . . . . . . . . . . .
`84
`L.). Robert N.
`in Flax (Lin um witati.uimum
`A Search for Atrazine Resistance
`Andenen and Richard
`Behre111 .. .. . .. .. .. .. . .. .. • .. • .. .. .. .. .. . .. . .. .. .. .. 85
`VOLUME 15
`Herbicidal Enhancement
`by Certain
`New Biodegradable
`Surfacta
`nts. L. W. Smith,
`C. L. Foy, and D. E. Bayer . . . . • . . . . . . . . • . . . . . . . . . . . . . • . . . . . . . . . . . . . . . . . . . .
`87
`JANUARY 1967
`A Laboratory
`Sprayer
`for Potted Plants.
`L. F. Bouse and R. W. Bovey • . . . . . . . • •
`89
`WSA Placement Service
`. . . . . . . . . . • . . . . . . . • . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . • . . . . .
`92
`Suataining
`Members . . . . . • . . . . . . • . . . . . . . . . . . . • • . . . . . . . . . . . • . • . . . . . . . . . . . . . . . • .
`95
`
`t-tB 71957
`
`TEXAS A&M U'
`
`NUMBER 1
`
`SYNGENTA EXHIBIT 1012
`Syngenta v. UPL, PGR2023-00017
`
`

`

`WEEDS
`
`Issued Quarterly by the Weed Society of America
`EarG, Ropcrrs, Editor, Department of Agronomy, University of Florida,
`Gainesville, Florida 32601
`
`Frep W. Sure, Treasurer-Business Manager, Department of Agronomy,
`University of Illinois, Urbana, Illinois 61801
`
`EDITORIAL. COMMITTEE
`
`W. R. Byrnes, Departmentof Forestry
`and Conservation, Purdue Universi-
`ty, Lafayette, Indiana 47907
`D. E. Davis, Department of Botany
`and Plant Pathology, Auburn Uni-
`versity, Auburn, Alabama 36830
`L. A. Derscnem, Department of
`Agronomy, South Dakota State Uni-
`versity, Brookings, South Dakota
`57007
`
`C. L. Foy, Department of Plant Path-
`ology and Physiology, Virginia Poly-
`technic Institute, Blacksburg,
`Virginia 24061
`K. C, Hamirtron, Department of
`Agronomy, University of Arizona,
`Tucson, Arizona 85721
`
`J. B. Hanson, Department of Agrono-
`my, University of Illinois, Urbana,
`Illinois 61801
`
`J. L. Hiton, Crops Research Divi-
`sion, ARS, USDA,Beltsville, Mary-
`land 20705
`
`Innicx1, Department of Soils
`R. D.
`and Crops, Rutgers University, New
`Brunswick, New Jersey 08903
`
`R. E. Nytunp, Department of Horti-
`culture, University of Minnesota,
`St. Paul, Minnesota 55101
`
`R. A. Peters, Department of Plant
`Science, University of Connecticut,
`Storrs, Connecticut 06268
`
`R. P. Upcuurcn, Monsanto Company
`V_ Building,
`800 N. Lindbergh
`Blvd., St. Louis, Missouri 63166
`
`A. D. WorsuaM, Department of Crop
`Science, North Carolina State Uni-
`versity, Raleigh, North Carolina
`27607
`
`WEEDSis a quarterly journal published by the Weed Society of America. The sub-
`scription price is $12.00 yearly for four issues; single copies $3.00.
`'
`Address all communications regarding subscriptions and reprints to F, W. Slife, Depart-
`ment of Agronomy, University of Illinois, Urbana, Illinois, All checks, money orders,
`and other remittances should be made payable to the Weed Society of America.
`The editorial office is located at Department of Agronomy, University of Florida,
`Gainesville, Florida 32603. Inquiries concerning manuscripts and other materials for
`publication should be addressed to the editorial office.
`Printing is by the W. F. Humphrey Press, Inc., Geneva, New York.
`
`To join the Weed Society of America, send remittance of $10.00, payable to the
`Weed Society of America,
`to Dr. F. W. Slife, Department of Agronomy, University of
`Illinois, Urbana, Illinois. Give name, official position (if any), and complete address.
`Dues are for the calendar year only.
`
`The Conference Members of the Weed Society of America (WSA) and the abbrevia-
`tions by which they may be designated in its publications, are the following:
`WWCG
`Western Weed Control Conference
`NCWCC
`North Central Weed Control Conference
`NEWCC
`Northeastern Weed Control Conference
`SWC
`Southern Weed Conference
`National Weed Committee of Canada
`—
`
`Entered as second-class matter at the post office at Urbana, Illinois,
`with additional entry at Geneva, New York.
`
`

`

`W E E D S
`
`2. l7RA,s, R. E. 1961. Prcplanling herbicides for controlling
`
`
`5. PA�IMl·.L, J. II. and C. ;\[. K1Nc. 1919. Johnsongrass as a weed
`
`
`
`Johnsongrass in field crops. Proc. SW 14:37-13.
`
`in Southwestern Jowa. Iowa Agr. Expl. la. Cir. 25. '1 p.
`
`1963. Combination treat­
`3. l7Rl·HIAN, .J. F. and T. \V. \VAU>Rl•I'.
`
`
`
`6. REA, H. E. 1955. The effectiveness oE clalapon in controlling
`
`
`ments o[ clalapo11 grass killer prcplow and EPTC prccmergence
`
`Johnsongrass. Proc. S\\'C 8:391-396.
`
`
`for control of Johnsongrass in corn. Down lo Earth 18(1):20-
`
`GORDON J. and C. J· \V1u..ARD. 1956. You can control
`7. RYDl·R,
`23. 1963.
`
`Johnsongrass. Ohio Agr. Exl. crv. Bull. 312.
`I. H,\lYSFR, E1.us \V., .J. T. T110�1PSON, and S. V. S1AcY. 1955. The
`
`
`
`8. WATSON, A. J. 1954. Field performance of dalapon, a new grass
`
`
`effect o[ chemicals on the ontrol o[ Johnsongrass and nutgrass
`
`
`
`comrolling herbicide. Proc. SWC 7:200-20 l.
`
`with and without disking. Proc. WC 8:399--10 l.
`
`Calculating Synergistic and Antagonistic
`Responses of Herbicide Combinations1
`s. R. COLBY2
`
`IN
`
`Let X1 growth as a percent-of-control with herbicide
`
`growth as a pcrcent-of-conLrol with herbicide
`
`expected growth a a percent-of-control with
`
`XY)
`hence E1 = 100 -(X + Y
`inhibition of growth by herbicide
`100
`and E1 = 100 ((100 Xi) + (100 Y1) -
`of growth by herbicide and Y = the percent inhibition
`(100 X1) (100-Yi))
`100
`
`of growth by and E = the expected percent inhibition
`
`(III)
`
`Abstract. The responses o[ herbicides applied singl) arc used in
`
`
`
`vVhen the observed respon e is greater than expected, the
`
`
`
`
`
`
`the ·'expected" response when they arc combined. The
`calculating
`
`
`
`combination is synergistic; when less than expected, it is
`
`
`
`
`e,pccled response for a combination is obtained by laking the
`
`
`
`
`antagoni tic. If the observed and expected responses are
`
`
`product of the percent-of-control ,alucs for herbicides applied
`
`equal, the combination is additive.
`1 \\here n is the number of herbicides
`
`alone and di,iding b) (100)"-
`
`
`In the use of equation II, original unit of data, uch as
`in the combination.
`
`
`weed count or fresh or dry weights of plants, are converted
`
`
`
`to "percent inhibition" values. Once this is clone, it is
` spite of the tremendous increase in testing of herbicide
`
`
`
`
`
`
`necessary to perform one addition, a subtraction, a mulLi­
`
`
`combinations, the words "synergi tic" and "antagon­
`
`
`
`plication, and one division to obtain each expected respon e
`
`
`i tic" have been largely avoided in publication of results.
`
`(equation II).
`
`
`
`
`Uncertainty in determining "expected" responses for herbi­
`If in tead, we convert the original data to "percent-of­
`
`
`
`
`cide combinations may be partially responsible for the
`
`
`
`
`control" values, the number of arithmetic operations re­
`
`
`failure of workers to report ynergism and antagonism.
`quired to obtain "E" is reduced.
`
`
`
`nother difficulty frequently encountered is that the herbi­
`
`
`cides used in combination arc not applied singly in the
`A at p lb/A
`
`
`same tudy. When herbicide have not been applied singly,
`
`
`
`there is no ba is for predicting the response when they are
`Batqlb/A
`
`applied in combination.
`
`
`Several mathematical methods are available for testing
`
`
`
`herbicides
`
`
`
`the additivity of herbicide combinations (3, 6). This paper
`A +Bat p + q lb/A
`
`
`
`presents a method which facilitates calculating "expected"
`100 - E
`
`
`
`responses of herbicide combinations. The ·'expected"
`100-X
`
`
`
`response for a given combination of two herbicides can be
`100 -Y
`
`calculated as follows (3, 5):
`If X = the percent
`
`A at p lb/A
`
`
`Bat q lb/A
`
`
`herbicides
`A + B at p + q lb/
`
`then, according to Gowing (3):
`E = X + Y (100-X)
`100
`
`
`
`
`tion II, the form used by Limpel et al. (5):
`E = X + y
`
`(I)
`
`XY
`100
`
`The use of formula III as compared with formula II
`
`
`
`
`eliminates the addiLion and sul)lraction, thus reducing the
`
`
`number of operations required to obtain an "expect d"
`response.
`Algebraic manipulation of terms in equation I yields equa­
`Colby (2) extended formula I to apply to three-way
`
`combinations.
`(II)
`Thus, if Z = the percent
`inhibition of growth by
`
`herbicide
`Cat r 11)/A
`'Received for publication April 11, 1966. Contribution No. 3796
`
`
`
`then E X + Y + Z -(XY + XZ + YZ)
`
`
`and Scientific Article No. A 1 271 o[ the l\laryland Agricultural
`
`
`
`
`
`Experiment Station, Department of Agronomy, Uni,ersit) of ;\lary­
`100
`land, College Park.
`
`
`
`land, College Park.
`
`
`
`2.\ sistant Professor, ,\gronom) Department, University of Mary­
`
`
`
`XYZ
`(IV)
`+ 10,000
`
`20
`
`

`

`COLBY : CALCULATING HERBICIDAL RESPO SES
`Now if Z1
`
`growth as a percent-of-control with
`termine the statistical significance of the differences between
`
`
`
`
`herbicide
`
`
`
`
`observed and expected values. Even without the chi-square
`Cat r lb/A
`
`
`
`test, several conclusions seem probable from the data in
`X1Y1Z1
`
`
`Tables 1 and 2. First, the combinations appear antagonistic
`then E1 =
`(V)
`10,000
`
`
`
`on dandelion. Furthermore, the antagonism seems to be
`
`
`
`
`
`greater with increasing combined rates, especially when the
`Obviously, the use of formula V instead of IV reduces
`
`
`
`
`
`herbicides were applied in 1964. Possibly this antagonism
`
`
`
`the number of arithmetic operations required to obtain the
`
`
`is caused by greater contact injury or more plant tops
`
`
`
`expected response since the subtractions and additions are
`
`
`
`being killed at higher rates resulting in less translocation of
`
`
`
`
`eliminated. In general, the expected response for any com­
`
`
`
`herbicide into the dandelion roots. It also appears from
`
`
`
`bination of herbicides may be obtained by taking the
`
`
`
`Table 2 that different weeds respond differently to the same
`
`product of the percent-of-control values for herbicides
`
`
`
`applied alone and dividing by (100)11-1 where n is the num­
`
`
`
`ber of herbicides in the combination. Each herbicide must
`
`
`be applied singly at the same rate as used in combination.
`
`
`
`Data published by Jagschitz and Skogley (4) are used to
`Chickweed
`Dandelion
`
`
`
`
`illustrate the calculation of expected responses for herbicide
`rcsponsc1
`response,
`%-of-con1rol,
`10-19 65" 10-19 65h
`%-of-control,
`
`
`
`
`combinations. Four herbicides were applied singly and in
`0.125
`40
`66
`
`
`
`
`certain combinations for the control of several weeds in
`0.25
`53
`0.5
`0
`49
`
`
`
`turfgrass. The data as originally presented have been con­
`16
`Mecoprop . . . . . . . . . . . . . 0.5
`87
`
`
`verted to percent-of-control values and are shown in Tables
`1.0
`j0
`62
`1.5
`0
`
`
`1 and 2. Expected values for the combinations are shown in
`0.5
`51
`2,4-D .. ...............
`75
`1.0
`64
`71
`1.5
`36
`I (6) + 5 70 (57) -13
`dicamba + mccoprop ... 0.125 + .5
`28 (4 I) +13
`0.125 + 1.0
`0 (0)
`9 (20) +11 67 (50) -17
`0.125 + .5
`3 (13) +10 21 (42) +21
`0.125 + 1.0
`0 (3) + 3 41 (34) - 7
`0.25 + 1.0
`53 (31} -22
`0.5 + 1.0
`0 (0)
`0.5 + .5
`(8) + 7 77 (65) -12
`(5) + 4 68 (56) -12
`0.5 + 1.0
`(0) I 70 (47) -23
`1.0 + 0.5
`(0) -I 55 (40) -15
`1.0 + 1.0
`(0) -I 69 (46) -23
`1.5 + 1.0
`57 -14
`dicamba + mccoprop 0.125 + 0.5 + 0.5 (3) + 2
`+ 2,4-D ......
`(43)
`64 (31) -33
`0.125 + 1.0 + 0.5 0 (0)
`) + 2 54 (37) -17
`0.125 + 0.5 + 1.0 0
`29 (26) -3
`0.125 + 1.0 + 1.0 0 0)
`
`Table I. Dandelion control in fairway turf treated with various
`herbicides October 8, 196 l.•
`
`lb/A
`
`Dandelion response, %-of-
`con1rol 1 10 7-6Sh
`
`Table 2. Chickweed and dandelion control in [airway turf treated
`with various herbicides l\lay 25, 1965.•
`
`I lcrbiciclc
`
`lb/A
`
`dicamba ....
`
`72
`
`I
`
`32
`
`12
`
`I
`
`dicamba + 2,4-D
`
`mecoprop + 2,4-D.
`
`I.Jerbicidc
`
`dicamba ...... .
`
`picloram
`
`55 25 43
`. . . 0.125
`0.25
`0.5
`97 81 79
`mccoprop .............. 0.5 1.0 1.5
`63 54 44
`
`2,4-0 . .. . . .... . .. . . . . . 0.5
`1.0 1.5
`40 10
`0.0625
`0.25
`51 (53) + 2
`0. 12<; + .5
`33 (45} +12
`0.125 + 1.0
`dicamba + mccoprop
`51 (35) -16
`clicamba + 2,4-D ....... 0.125 + 0.5
`
`64 (30) -34
`0.125 + 1.0
`58 (14) -44
`0.25 + 1.0
`46 (23) -23
`0.5 + 1.0
`56 (61) + 5
`0.5 + 0.5
`0.5 + 1.0
`47 (52) + 5
`43 (51) + 8
`1.0 + 0.5
`57 (44) -13
`1.0 + 1.0
`76 (43) -33
`1.5 + 1.0
`63 (34) -29
`clicamba + mecoprop +
`2,4-D . .. . . . ......... 0.125 + 0.5 + 0.5
`31 (28) -3
`0.125 + 1.0 + 0.5
`52 (29) -23
`0.125 + 0.5 + 1.0
`54 (24) -30
`0.125 + 1.0 + 1.0
`77 (13) -64
`dicamba + mecoprop +
`2,4-D + picloram . ... 0.125 + 0.5 + 0.5 + 0.0625
`
`•Adapted from the data of Jagschit, and Skoglcy (4).
`hExpectcd responses for combinations arc shown in parentheses following each
`observed response. The differences between observed and expected values also arc
`shown by a plus sign to indicate synergism and a minus1 antagonism.
`
`mrcoprop + 2,4-D
`
`combination. Thus, combinations which were about addi­
`
`
`
`
`
`tive or possibly ynergistic on chickweed were antagonistic,
`
`in general, on dandelion.
`
`
`
`The calculations involved in determining the expected
`
`
`
`response of one three-way combination from Table 1
`
`
`
`
`illustrate the efficiency of formula V compared to formula
`
`IV. For example, using dicamba at 0.125 lb/A in com­
`
`
`bination with mecoprop at 0.5 lb/A and 2,4-D at 0.5 lb/A
`
`
`
`the expected response is calculated as follows using formula
`
`
`IV and the data in terms of percent weed control as
`
`
`
`originally reported by Jagschitz et al. (4).
`E = 45 + 3 + 37 _ (45(3) + 45(37) + 3(37))
`
`100
`parentheses following each observed value. To the right of
`
`
`
`
`+ (45) (3) (37)
`
`
`
`each expected value, the difference between observed and
`10,000
`
`
`
`expected values is shown. A positive value is indicative of
`_(135+1665+111)
`+ 4995
`85
`
`
`
`a synergistic response while a negative value i indicative
`10,000
`100
`
`
`
`of an antagonistic response. If the observed and expected
`85
`-19.11+ 0.50
`
`values had been computed individually for each replica­
`
`66.39% weed control expected
`
`tion, then a chi-square test could have been used to de-
`21
`
`•Adapted from the data of Jagschitz and Skogley (4).
`h£xpected responses for comhinntions are shown in parentheses following each
`observed response. The differences bc-twecn observed and expcc1cd values also arc
`shown by a plus sign to indicate synergism and a rninus, antagonism.
`
`

`

`W E E D
`
`1 -
`
`
`
`the dose-response curves deviate least from linearity at the
`
`
`
`Using formula V and percent-of-control values, the com­
`
`
`
`putation is
`50% level.
`E _ (55) (97) (63)
`LITERATURE CITFO
`1 0,000
`. R. and G. F. lVARREN.
`1 963. Herbicides: combina-
`I . COLBY,
`= 33.61 percent-of-control
`tion enhances selectivity.
`cience 1 1 1 : 357 .
`
`and 33.61 %-of-control is equal to 66.39% weed control.
`2. CoulY, S. R.
`l 965. Green house eval uation o[ herbicide combi­
`
`
`Obviously, there are practical limitations in using mathe­
`nations. Proc. N E \VCC 1 9 : 3 12-320.
`3. Gow1NG, D. P.
`l 960. Comments on tests of herbicide mixtures.
`
`
`matical formulas in predicting the responses for herbicide
`Weeds 8: 379-39 1 .
`
`
`
`combination . The methods described here arc approxi­
`1 966. Dicamba, m ecoprop
`4 . JAc:sc1 1 1TZ, J . A . a n d C . R . SKOCLEY.
`
`mations, but they represent an improvement over no at­
`and 2,4-D combinations [or t h e control o[ clover, chickweed
`
`
`described tempt to predict responses. The computation
`and dandelion in t urrgrass. Proc. N EW C 20: 496--50 1 .
`
`
`should most effectively be applied to population of single
`5 . L1 M P� L, L . E., P . H . C I I U LDT, and D . LAMONT.
`1 962. \Veed
`con t rol by dimeth y l tetrachloroterephthalate alone and in
`
`species although this would not seem to be an absolute
`cer tain combinations. Proc. N E\VCC 1 6 : I -53.
`
`requirement. Furthermore, the formulas are most accurate
`6. TA�I M I·.
`, P. M. L.
`1 96 1 .
`Jsoboles, a graphic representation of
`when values of X, Y, and Z are near the 50% level since
`synergism in pesticides. Neth. J. Plant. Pat h . 70: 73-80.
`
`Seasonal Variation in Sprouting and Available Carbohydrate
`1
`in Yellow N utsedge Tubers
`
`R. B. TAYLORSON 2
`
`Two morphological types or tubers o[ yellow nutsedge
`bstract.
`(Cyperus esculentus
`L.) were collected over a 2-year period and were
`sprouted in t he laboratory. Tuber dor mancy occurred during late
`sum mer and early [al l . prouting was highest during the winter and
`spring. Mechanical distu rbance o[ the n u tsedge stand increased tuber
`sprouting. Available carbohydrates followed a pattern similar to
`sprouting; minimum levels were found during late summer. The
`two types of t ubers appeared to be similar in respect to the charac­
`teristics studied.
`
`relate carbohydrate levels with herbicide susceptibi lit1
`
`
`
`'
`have not been clearly
`successful (4, 5).
`
`J n these studies, l have attempted to characterize tube,
`
`dormancy and carbohydrate content and their possible
`relation to herbicide u t i l ization.
`
`:l\IATERIALS
`
`l ETHODS A 10
`_A dense stand of yellow n utsedge growi ng i n a field of
`} TRODUCTION
`
`Tifton loamy sand was the source of plant material. Sam
`
`pies were col lected at monthly interval from J u ly, 1 96�
`RMA N CY commonly occurs in various organs and al
`
`to June, 1 964. During J u ly, 1 962 to June, 1 963, samples
`
`
`different seasons of the year among species of h igher
`were randomly collected over the i n fested area. The stand
`plants (7). General ly, l ittle is known o( dormancy i n sub­
`
`was not disturbed mechanica l ly except for an early spring
`
`terranean organs of weeds, including tubers of yellow nut­
`plowing and harrowing. During the months o[ J u ly to
`sedge (Cyperns esculent us L.). Tumbleson and Kom­
`1 963, �he are� was subdivided i n to 25 by 5!1
`November,
`
`medahl (6) indicated that tubers were dormant when d ug
`ft plots. Three twice-repl icated treatments were imposed.
`
`in September but would germinate i n June. Breaking o(
`One treatment was a con tinuation o( the mechanicalh
`
`
`tuber dormancy was thought to be associated with low
`und isturbed stand mentioned above. Other treatment,
`
`
`
`has temperature and leachable inhibitors. Other research
`were (a) mowi ng approximately 2 weeks prior to the nex1
`dealt mainly with methods of breaking dormancy
`of
`sampli ng_ elate and (b) disk-h_arrowi ng approximately �
`
`
`tubers by chemical techniques (2). Control of yellow n u t­
`week prior to the next samplmg elate.
`A t the conclusion
`
`
`sedge with po temergence herbicides is partially de­
`
`
`of this sampling period, further collections were made
`pendent on tuber dormancy,
`
`since emergence of shoots
`only from the mechanically undisturbed plots.
`
`must be optimum when the herbicides are applied for
`maximum e fiects.
`At each sampling date, duplicate lots of approximateh
`
`often related to effectiveness o[ herbi­
`Another factor
`
`500 tubers were recovered by working the soi l through
`cides in the control of perennial weed species
`is the level
`a coarse screen. On several occasions during 1 963, u11
`washed tubers were recovered
`from mechanically undi�
`
`of reserve carbohydrates. H owever, studies attempting to
`
`turbed plot samples by searchi ng the soi l sample and
`1Received for publication February 24, I 966. Cooperative investi­
`brushing off most of the adhering
`soi l from the tubers.
`gations o[ the Crops Research Division, Agricultural Research Serv­
`Except for the unwashed lots, the tubers were sul}
`. S. Depart ment or Agric u l t u re, and the Coastal Plain Experi­
`ice,
`
`jectively graded into four types according to externa.
`ment Station, Tifton, Georgia.
`'Plant Physiologist, Crops Research Division, Agricul t ural Re­
`color and morphology, and then counted. Type A tuber,
`search Service, U . S. Department or Agriculture, Tifton, Georgia.
`and usually dead; type l'
`were black-skinned, shriveled,
`Present address is Crops Research Division, Agricultural Research
`were black but turgid; type C were brown and turgid.
`ervice, U. S. Department o[ Agriculture, Beltsville, Maryland.
`
`22
`
`DO
`
`