Weed biology: importance to weed management
Transcrição
Weed biology: importance to weed management
W'eedScìence,45:349 356. 1997 SlmPosium:ImPortanceof ueed bUlogy t0 ueed mãnag€ment \l/eedScienceSocierlof America, Norfolh, Virginia, 1996 Weedbiology: importanceto weed management Prasanta C. Bhowmik Dcpaíncr( uf Pld rìd Soil S.ictrcci UniÌc.ritl òf Masgchusets, Amhei*, Ì\4À 01003 Knowledge of {ed bioios/ is essendil for dseÌÒpment of borh €coronicãÌll ànd cnviroDnent lly .cc€poblc weed man?gêmêntsysems. lic€ì biôÌÕ$' reììresrô l,Ì3nt rtributcs such * Áorpholog,', seed dormmcy and gerninarion, phpiology of growih, @nìpetirive abilitr, rnd reproductive biology. Concepts ofpopulãtion biol.nn'r- a' d oor r*en- J"r r"n.q and or ;s) - .c.dtr \ dyrrrrig * i r"yr .hr ' g " o , ' " "p , o p " Ae. o "p J . r n , l . , n b e u e d t o t ' " d i, - . . J i , G i ' i ^ t u n e " e r" n J r " e ' , l u _ c u ' , i n , b l " r n r n , g e m e n. rtn r e g r c .T , e g , r . " d' o p , u r h b h give p.ioritr to deplerion of reot rerrves or seedbrnis rlìrcugh inÈrfsing with doimancy or sernÌinâtion reqúiremenrshave grcat potentiãÌ to úlDnce weed mxnrs€m€nt sÈtegies in the future. Nomenclature Conmon hilkweed, Á.á?@ rye.z L. ASCSÍ purple nltsedgc, C!?c/u ntanà,s L. C\PKO; ycllorv nursedge,Cyü^ 6tu1Ì"r* L. CvPEï v.1\.Í' ],àÍ, Ábunlofl thco?h6tì }l€dí s ABlrTH. Key words: wed biology, weed managenent, popuÌaÌion biologr',ASCSX CWRO, CYPES,ABUTH. For cenruries, namLal vegetation has been changed by g r o r i n g u , , o ' ì \ ì , t l r r ô Í r g r i , , , ì , , , r eC, , n t t , ' r d ' xr i ô n p r . r i . c ' , u c h a . . u l , i \ J r ì o n .r ' e o t r e n l i z e r . i. n , r o d u . r i o n of crops, use ofmonoculure, and ctensive use ofpesticides h J v e r f f e . . c d , g r i . u ì r u r u ì e c o . y s t e m .\.f e e d r p e . , e ' i r c p i oneers thât increaxe diversiry of agricuhumÌ ecosystems by usilg rheir envirormentaÌ potential. The divcmity is graduaìly increred by cropping systems targeted towards mximizing crop production. k is time for us to Ìook ìnto a31r i . u h u u l e . o . y . r e m ' r o m n i m , r p - o d u .r i o n i - p u , ' . Considcrable literature is amìlable on weed biolog/, including úe characteristics, phenoÌogy, and life cycÌes of many spccìcs.This pap* summarizessome of the literaturc on úe biology of annuJ and perennial weeds with speciaÌ referena to cornrnon rnillweed and nuaedges. k will high' light some ìmporant attributes of weed biologl as they rerate to weed marÌâgement systems, HistoricalPerspectives ì Studiesof weed biology stated as early as the 1930s. (1937)perÍormeda seriesofquantitatìvesudPavÌychenko ìes on rhe rooting characteristÌcsof weedsand crops grown in comperitiveand noncompetitive associations. Thoscearly studies demonstrated the imporrance of weed<rop interactionsin reladonto rhe root systemof weedsd1d cÌops. In the northeast,â seriesof publicâtìonson the life history of soeral weed specics,including nuaedgc,was publishedin the 1960s(Bell et aÌ. 1962).The publicationof r seriesof weedspecies in "The BiologyofCanadianVeedí' was aúcn,pr o jnLily thc nnportanccof wcc<lL'iolosy in weedsciencein the early1970s.This seriesincludednore -er;ew'.in rhan I00.pecie'*iú compr.h.n'i'. literarure (Bhowmik cluding common milkweed anclBârÌdeen1976) ud yellow nutsedge(Mull;gao md Junkins i976). IrÌ the I980s, púbìicâtiônof "Ihe Biolosr of ÂustralianVeeds" resulred ìn thorough Ìiterature reviews wÌtlì emphdis on ecologicaìaspects. rn spite of all the litcratuLeavailable,researchon wced biology and its potential usesin weed mãn €ement sysrcmshas been limited. roiew of Leferences to weeds,AberIn a comprchcnsivc nathy and Br;dscs(1996) indicatcdthar weedbiology/ecoÌof ogy hrs conrinuerlro increse in termsofthe percentage in th€ pre'1970s total publicationsper decadefrom 14.3%0 ro l8.8ooi" rhe 9o0'. Tn ,orrrra.r.rhc per,ep.ionconcerningthe inìporlanceof weed bioÌogy to weed managcment h€Ìdby weedscientists is slighdydifferenr,asindicãted by úe surveyof Norris (1997). This suwey said the importanceof weed biologywas moderate(3.1 on a scaleol 5.0). Earlier research included weed phenolosy, weed<rop competition,ând repÌoductivebiology.DeveÌopment of economic úresholds lor weedspecieshasmadesignificant progress in ihe lait d€càde. lntegrâted weed managementhas focused on the effects of crop planting dates,row spacing, cuÌtivators, ure of cover crops, ând reduced herbicide râtes. Culent studies of weed biolosr are in nansition, Ìargely due to the efTectsof agLìcuituLalpractices on weeds,cLop' ping systems,and thc cnvironmenr.The reseuchemphasis has changcdba;ed on the need to undersnnd basicweed populabiology.ft is our job ro predicthow weedspecies, tions, aÌÌd biorypesevolvein response to selecrionpressufe pLimarily due to agricuìtuLa1pLacrices.This klowledge wìll hclp dwclop vccd managcmcntpracticcs.Curcnt rcscarch in weedbiologr continuesto exploreweedseedbank dynrmics, root Ìeserves, tuber dormancy,evoÌurioDof weeds,úd modclingof weedseedlinseneÌsence. BhowmikWeedbiology:irìporrancc to wcednÌãnâgenet . 349 encesin two yeÌlow nutsedgevarieties, C. escabnta.s L. var. $&h,t'! L. aná C. esc*lznt* L. et lz?Ìo'tãcb]ú' Roe.A. Cornrnon Milkweed They found that .ar. escubntu:had longcr, narrorver, and Common milkweed,a perennialweed nâdvero eâstern ro,c uprighrh"'e. ano Êewer ruber..rLizorer.r.d,eed headsrh-n 'ar. bpton,\u, rhey rì,o rrporcd ditÌcrenLial Norrh America is limired to the regionboundedby 35 and r0 degree" N Lrirude.rndo0 and t0J dcgrees ro severaÌherbic,des. W longj,ud( suscepribiÌiry (Bhowmik199-l). In a comprehensive studn differcnces in growú ofpurpÌe Comnon niÌkveed sedlings becoÌne perennial wnhin nutsedge from tubersreceived lrom 14 stateswirhin rheU.S. 18 ro 21 d atìergeÍminâtioDb€causc planrsbecomecapabÌe and from 21 locations around the world were noted fVills ofproducingnevÌshootsfrcm buds(Biowmik 1993rBiow1978). Ditrerencesoccurredin the numbeLof shoos prornik and Bmdeen 1976; Evettsând Bumside 1972). The duced from singÌe tubers, the number of leavesper shoot, parent root survivesfor and the lengrh and width of leaves.Differelces were also growingseasons, depenclingon soiÌ condirionsand ftequencyof rÍhge. iounJ among,hr c.oDp.sfnr Roqe,,ng.lengrlrol rhe ra .his Jnd rhenumber.ÌeneÌh.andw,d,hof i"volu.rallele, PhenoÌogicaÌgrowth stase of cach speciesdescribesits growth and subsequenrresponseto environmertal condi ât the âpexofrhe rachis.Flowerpnrts,includingrhe number tions, incÌuding growing degreedays. Common milkweed ãnd lengú of seed staÌLsand the lengrh ol seedspikelets, undergos nine phenologiol stagesto completeirs life cycle vried rmong ecotypes.Ìn general,greatervaÍetronswere (Sinard et aÌ. 1988).Thesesascsincludcshootcncrgcncc, found mong thc plants from diFerent Ìocationsoutsidc dr '<gerrrivc srowh. bud{:se. umbel.honing.Íìsr Íloucnng. contìnenuÌ U.S. than from diflerent locationswithin the ÍulÌ bÌoom.Ílowo *n-..n.e. 'malì ,cedpod. mrrure.ee,J pod, and ripe seedpod. Simardet aÌ. (1988)idendlìcdrhese phenological growth stagesand establishedrhe required de, Population Biology gree days lor each stage.The degreedays for each pheno, logical growth stagecouÌd be ìmportant in predicring seasonal developmentof this specics.Thus, a degreeday rnodeÌ ,4..Annua.ts bxed on phenologicalstagesof perenniaÌweedscould be deveÌopedmd couÌd be usedin makingwcedmanagement decisionsfocu.singon culural practices.The model could Annual weed speciesreprodue by seedsand spread alsobe usedto predicttiming ofchemicalconrrolpracrices. through dnpcrsalofsecds.The imponanceofshort distance AeriaÌ shoots emergein spring (&ÌiÌ ro May) frcm uDweed spread in and bemeenarablefieldsha; beendescribed dergtound adventirious root buds. Adventitious root buds in this symposium by ThilÌ et aÌ. (1997). They explained arise eiúer on the stem base neâr the soil suface or on some causes of sprcad and subsequent elfectson crop prolareralroom (Bhowmikand Bandeen1976). en rhereis ductìon. They indicated that specÌÊc weed muagement opsufficicnr foliagc, root dwclopmcnt bccomcs activc. Root growth terrninates during mid-Augüst to mid-September tions can be used to reduce nan-câused lveed seedspÌeed and betweennearby6elds.Jordm (1992)emphcized whcn most shootssenesce. Most .oor buds remainviable within q< krou ,oo Ìinle abou, unpre.li.r"ble q,ia,ion. in rhrr throughoutthe severewinter months and sprout with the seedd;spersalto do more rhm speculareabour the conrriadvent of spring. FÌoweringoccun in lateJuneor earlyAugustdepending bution ol suchvariationsto weed managernenrThercforc, the factorsúat controlseeddispeÌsâl,seedpÌoduction,and on initiâÌ emergenc€and grorvth, weather conditions, and seedsurvivaÌ may inÍìuence úe weed populatron. habitaa. Plan* grown fron seedsseÌdom lìower until úeir secondsummer (Bhowmik 1970; Bhowmik and Bandeen 1976). Àlso, newÌy d*eloped shootsfrom the sameroot .y.rem normrily flo$er durtnCrhe ne\Í grôwing,caon. to Seedpods matureand spÌit open in eârÌyfâll (September T\e pre"en.eo' J \ rop cúop) cu .hag. rhe.omperi. October) and úe seedsare dispersedby wind, carricdby growth and detive abiliry of weedspeciesand subsequent the tufts of floss. Mature pods are found artached to dead velopment of weed species.Also, it can reduce production stalks unril late fall (November to December) md wen the of seeds.The presenceof corn (Zca nals L.) reducedseedfollowing spring. rain ofvelvedeaf50%. This seed'raintcachedits maximum Ìev€Ìat 20 to 30 plantsm '?in corn, and at 30 to 35 plânts m'? in velvcdeafmonocuÌture(Zanin ând Sattin 1988). Ecotypes However, wiú only 4 to 5 plants m 2, velvedeafproduced Nutsedge 8,000 ro 10,000seedsm 'zin competitionwirh corn. Âccording to Grirneì model, velvcdeaf can be cÌasified speciesdiversit/ has beendevelopedstodily under dispc.ics(Grihc 1177).Its bioÌosicâl conditions. asa competitive+uderal versecroppingslstemsandvariedenvironmenlaÌ m.ke i. prnì.uJarìy competi rn,J ..olog.rl chrrrcrcrlri., h.r'e Ecorypi.rnìarion.r-"ng purprernd 'eììou nut'edge I rt p c n r r c n ; r n , u l r i r a r e Ê J e l d . . h c c c o n o mti \rr e . h r i r c a n d becn r.porred o'ra and Appìeb1l9-6r Hruser Irú8: plants bâsis, varies between 0.3 and 1.7 old, on a sìngle'year 1974). The vaLiations have been identiStollerand Weber ' m tZ;nin rnd 5J|lr- ìq88). Ba'edon rhe competi"rc Íìed by name or physìcalcharacteristics. abiÌity during úe vegetativephae ofvelvetleal the concept YclÌow nutsedg. pl.nts froo Ceorgia grew mller, flowered of growing degreedayscould be used to predict height, leal larer, and produced larger tubers than plan$ from Delawire (Hauser1968).Cosraand Àppleby (1976)describeddifferarea,and overalÌ production of biooass. Phenology u.s. 350 . 45, Mây-Jüne1997 WeedScience Seedbanl Dynarnics in anble The vrst malorityofscedsenternrgrheseedbank (Hune Ar.hiháÌd 1986r and -eeds l"nd co-. f'"n """.,1 RobertsI9sl). Only 47o of the weedspeciesin arableland aredescribedasperénnial(KÌopac196ô rimited dataexist on rln r"r"l i'rpuror rll 'ccdr l,ro rnble ""iÌ Dìfferenrral dare'^l lp.nine heNe(nând$irh'r .P(:es'\rcvcn' lr).ì') upi.l <eic oiripe 'eed' and dlruge ro rìperrrrg'eeds ' i Ê ì c u l \r ,' ' e ' h a ' . m a d c' u c h ' . u d r c d dur'ne,oll(.uon rhelesi.Chancellor(in RobeÌts1970)estim.tteddìat a dense stmd of weedsproducedmore than 1,235,000seedsm 'z. ifhc posidonof-weedseedsin soil is likeìyto influencetheir o o o u : r r u nd y n : - i . ' . | \ e ' p e c i e . . n m p u . i r iror r 'dr J c n ' i r y ;, *...1 '..J i" .oilq Ë.e,(,rl) bu' ''.lo*1, inled . rl-. pr:nrary,oune of newiire"rari"n.ol "nnu,l *te.l' ea.h 1e.ri,no i.p'e'en'r rhc nr,oriq of "ccd .p<.ie' íelc ì'r8JJ.\ecd;anl dynami..Íìu',u:rewdcly depcndìg on rnd ìo*es(Burt rhc m"enirudcor ncu 'eedirrrrodu.rions sicleet d. l9s6j Wìbon 1988).The forrnationofseedbanks of annual weed speciesand úe effccrs of selectedmanagement pllctic€s on those weed seedbank were reviewed jr derailby Buhlerct al. (1997). L a . r c r u o o n e . v v . mh c ' i r . o w n p r r t u l a r a " ' o cl i o n s i r h w e d . ; - i e i . u . h r " r * d ' : n ì o u b u r hl i u c b e r rrl l a , ciniun anguxi:fol'an À1r.) (Yarbotough 3nd Bhowmik 1989), rca lCanellìa sínazos(L.) Kuntzel, sugar beet (Baz wlgaris L.) , and soybeanlc\cine n,Lt (r.) Metr.) (Horzner in a croppingsystemaJeâlsorep1982).Most veed specìes resentedin the sccdbanL.Robens(1981) noted úac some ol the greatestdiflerences;n weed floras are bctween ctops in the lall and winter (i.e, winter that haveweedseedÌings appcaringìn thc ceLeal)and cropsthar iiaveweedseedlnrgs (e.g., coLn, soybean, and springcetcals) springúd Nrnmer \eedbi-k' .J,/ fiom cÍoppi g 'y.rem ro croppinb'n' rcm. Avenee total sccdbankdensitiesof aDnuâl weeds rangedf."- 6OOto 162,000viableseedsrn 'zamongwiouslocationsin rhe Corn BeÌr(Forcellaet ai. 1992).Percent ofviable scedthat emergedu seedlilgsin fieÌd pÌotsranged fron lcs than tvo for ycÌlow Íó.k t (&arbarcd Mlsàf* R Br.7ro rnoofo slat toxrail(narìa [ab".lHerrm.ì. Fedroor p'e*eeJ rr'ryaunrtts ra,oflau L.t and common ìrmb' qÁ,r. 1chül1od,unntbuq l.t tac,he rort fr"qJ.nrl) encounteredspeìies.This study also indicat€d thât lìom t0 werenonviablc.Àgain, ro 907ooftotal seedil rhe seedbaok rhis nìformadon on weed speciesnumber, mortâlity, emerg.nce,rnd orh.. p-""*tere couÌd be ued in biocconomic weed managemcntmodels. moreproductiveon fcnile soils,addVeeds m geneLally ing morc seedsto the seedbanki for *amplc Anaranthu pouquií S.Wars ard Amaranthus retroflexrr L. respondedto increascd soil fertiÌity with increasedsccd production rHauprli lr)-8ì. f'rr mlurc. 'pread* 'enrliz,r "nd Jai" c,n be rn imp"n,n, ,",r," of.""d, .ô, rhê ,""dh)nt o' anble soils.Seedsof many weedspe.iescàn piss through the digestive tracrs of cattle, shcep, horses,pigs, and goats to be depositedin a viable state in the feces(Dore and Râymond 1942; SalisburyÌ964). The seedbankof Clszapodiun 'pp. wu ,ignifrcJn,h highcÌ,inJ held re.eiv,ngm. neignborinB 6cld rc' rhan r a .omparablc ceivingnone (BenÒit1986). oí q.e'ì lilìaeeere.'.r infl:"".4 rhero ì, rl di.rr:l-rrrion 'o .-d i"ìh;'o'1. Ch,"ge. in reed 'eeddcp h in I ph' a role in weed speciesshifts ãs dllxge Prãcticesâre altered (BuhÌcr 1995rBúÌer et al. 1997).ln a srudyin MassacnuCronq ) planrsProduced sens,horscweed(Cazlza .zurl'r'l asmrny d 200,000secdsplart ' iI a no-tillagesitc (Bhow mik and Bekech1993).The soil from the norillage sitehad seedsof the toÉl seedsin the 80% eerminablehorseweed r"p 2-.m. Th, ,,urnb.rot 'ecdslound oecli-.d ^ deprh inir*'ed. \" germinrblered. *ere rourd below6.r ar the norillage site. ln contrast,the converÌtionaltillagesite had feweLhorsewecdreds than the no-tilÌage site. How*er, througlÌoutthe surfacc14 the seedswere cvenly<listLibuLed cm of soil in the conventionalsite. In a pasture,ForceÌla and GllÌ (1986) showeddrat annualtiming of cultiration such composition.Species had a dramaticeffecton species as reá 6rcrc (Rronw ruben L.) and'si:l:vetgnss lvulpìa bro' (L.) s. F. Grayl arained dorninancein sunmer- and moìì.es early fall-tilled plots, whilc red sorrel ( Rand a&tosela L) aul prustraLekno*ccd (?olxgotun d"nakft \") vcÍc s;s nificanronly ìn plots cukiated in winter. Spàtiâl distribution of weedsis importdt in alÌ irÌterâcplanrsard betwccnplaritsand rheir environrio"i The lmportanceof spatiâldistributionof weedsúd mcnt."-one how spatial dhtribution influencespopulation and communiry dynmics has been presenredin lhis synPosium (cardnìa r997). d)"mi6 frrn,:ng pra.rite.inÊuen.cwccd puPuìa,,on .pec.' . o1,íIe.ring rhequ,,,"'i' t oÍ'eeJ' "mpo'irion "nd returnedto md removedfrom soil (wiÌson l98B). Culti' vatior playsa Ìnâjor role ìn depÌetiDgweedpopulationsin of inpur from seedproduction, arableland. In the absence dre seedbankdeclinesmore rapi<ìlywirh cultÌvadonthan without it (BhowmikaDdBclcch 1993;BridgesandlX'àÌker 1985; Brrhler 1995; Robens 1966). In England,seedling on undisturbedsoil deplctedonÌy 17oof rìrcviemergence abÌeieedbanL (Froud-wiÌliams .l tcs3; Robertsand "ì Dawk;ns 1967). The use of herbicidesro complementstandardcultirztion pracdca ca drroticalÌyreduceweedpopulatiotx itt soiÌ (Rob efts and Ncilson 1981). For *amplc, anzinc t6-úloro-,4/usedin erhyll/-(ì-methylethyl)-1,3,t-triaziDe-2,4-disminel corn monocuhure reduced thc sccdbark 9870 úer 6 )Í (Schweizerand Zmdúl 1984). How*et, 3 yr atter ârrzine yr, rhe sccd' w had been disconúnucdin pÌors neatedfor 3'Ihe dynmia to ha1f ns orìgÌnal deruirÍ ban-khad reboundcd ;n a givcn field changeunder any integated wced of seedbanks mènascmcntsFtcm. Thc úangcs mut bc rccosniz€ddd have to be inregued as m inpur ofweed demognphy B, PeÍenniâls Many weedspossess an abiliry to colonìzereadiÌyin a wide r.mge of disturbed habitats. Vegctativereproducdon is 'l'here a common trait of perennialweeds. in exmpÌes of perenni:Ìweedsthat propagatevegetatively one or more wâys. Vegetâtivepropâgârion Dìâyitrclude stolons,rhi'zones,rubers,bulbs,corms,room,and rems. Common rnlll:weed and both nutsedgesproduce seedsand vegetativcpropãgulesthat hãve €normouspotentiaÌfor coÌoniatìon and reproducdon. Bhowmik\veedb;ology:importmc to weednanagement' 351 Root Bud Dgramics of Common Millqreed ,io,rÕuìd be,,rÍg(,(Ì J n,à, weeot. dro$| t .,h. po.r-Roue,inb {Jge or pe,(n- common mìtÌ,wrcd propâgJ r vc8.,Jr\et) b\ a crccpinS -oô' )\(m. .rndrce roor,u{rrll) g oh ro r dppr\ ut ìoLr Àhhough extensiveroor growrh occursduring thc firstru ì20 ,m íBhúsmika d tsrnJren o-r,t. Numcrnu.rdyea,grumh oi.ormon m:tlvcpd \hoo,\ io,n ì e âd"envdrririousroot budsappeardúouslÌourrhe roo! sl$rern,rhe ririou' -oor butl, d" no. cìe,ge ||ú- 'o I un,il ,h(,e.ond najority remainìngdormant (Bhowrnik Ì993; Bhownik y€ (Bhowmik and Bandeen1976). The growth of roor ând Bãndeer1976; Gcrlardt 1929;Groh 1943) until conbuds is smonglyinhibited by the parent stioot (Bhowmik ditions favor dreir grorvth. and Bândeen1976i Evett! dìd BurnsideÌ972; Jefïeryald SeedÌingsproducebuds on rhe main roor closeto tlÌe Robinson 1971), but rhc mechanismof nrhibitìon is un, ground surfi.e wirhin r petiod of 18 to 21 d alìer emer- knowo. Apical dominance,hormonal conrrol,and Ìoor regence(Bhowmik and Bandeen1976). In a clipping stLrdy servescould be responsibÌefor adventitious rcot bud doru f . o q o n m i l k u c . J. e , d l i n s .,.h e . p - , r ;" (Bhowmik nancy and Bandeen 1976; Everrs and Burnside tj,ri,iD . rúed JnJ ,hc nu,',ì'e.of.lr). 'cqu:,edlo," .pfou, nBde. 1973). . , < r . F dr , d a ) . r , ú mp ì r n ,n b , o . t i i p i n s i ' , . * ; t e d' B I o * In general,roor bud clormancyin cornnon millveed 'o mik arìd tsdnJ(er 6: tverr. md Burn,ideto 2r. Rc increased a the tot:ì sugarleveÌin roosrocl<sincreâsedin moval of top gfowth lroD 2l-d-old seedlingsresultedin rheirJlíBh"wm'k o-0r. Roo,hud.oloo, irgmcrrr.were 28oloresprouringof roor buds (EvcÍs and Burnside1972). Ìea.srdormant irÌ MaÍ An averageof 13.2ok ol íoot frígThc 'uru'rJ and rrgrumlrof,eedlìn9:n.rcnedas.eedl:ng, ments wirh a visible bud remain-ed dormant in May coni de'(1"trd âddj'onrl leat pn-. rhi -umb.' or ,p'nu'ú parcdro 52.2oloin Seprember (Bhowmik Ì970). High renÈ buds ianged from 5 ú i00o/o when tlìc seedlinls were peraturebrokc root bud dormancy.\7hen incubatedat 27 clipp.,Ì d"*" !o 2 ro 3 cm comparedro 7.t ro I2.o cm C, 80 to 95olo of roor lngments colÌected lrom May to raÌl (Bhowmik ancl Bandcen1976). Thus, sprouringdoes AugLrsr 'proured.u 1,,1, n,ìlyu-oo roor -)oo n o ro . . u r i r h c e d l i r r ug n' ' ì r h e ). , , e . l . p p . d . ; n J ì . a r ; n g , h ae,d q h ( n , o U c . r c di r r < " t ' r e m b c"f Ar r. l 1 ( 2 s r o oT api.J .lom nân.c doer pìa1r ,uìr. AÍer . yr of nrurrJ Ìoot fragmenrscollectedfrom May ro July sprouted.Howiund:,'u,bed)e.rrbli.hmcr. one .etJling produ.ed str ever, rherewas no sprouring acrivity in Augusr and Seprcm ; r l l . ' . g e ' . ' , , c 1. ' n d0 4 ' " Ê , l l i n tis_. r I r - : r e r . L,eraL 15 C. Root Íìagrnents in rclarion to size, length, and maturiry alsoplay an important roÌe in sprouringactiviryin relation to the time neededfor sprouting.Smaìlerroot fLagrnents Tuber Dynamics of Nutsedges reqüircda longerrilÌe for spÌouring(Minshall1977).Ninethber funanìcs ry to 10070of root fragmenrs30 ro 45 cm in tengrhsprour BõaÌ buÌbs úd tubersfunction borh s srorageand r<, eJ. bur ,Ì.orreloor frâgmen''l'a'lcJ.o well rcer-.5 productive organsfor nursedge(Horowitz 1992).They d;Ê "p-ou' h'rdr lo2i)ì Onil 360ooi rl,c roor ir,rgmenr. .m in prirnariÌy fèr by their posìrioDin relation to the rnother Ìfnslh fon,,ed,\ous -e&hìngr" or s-owrrgrboverhe,urpÌant. BasaÌ bulbs arc direcrlyconnectedto an aerialshoor. Í r c e o í r h e g r o u nìJ - ú J i , c r p l J n ,n s { M i n s h J ìl lt , . As rhizomes clongare, tubers are produad on rhizomes. They consistof rhizomatoustissuewirh numeroushúds (ViÌls 1987;\íills and Briscoe1973).Thesebudshaverhe potenriaÌ to sprout and initiate rhimmatom growth rhar de The roor rcscrves ofcommon milkve€denablelons'term velopsinto seedlings and cvenually,maturepÌants. survivaÌand vary overrhe gÌowhg scason(Bhowmik1993). The percnt total cabohydnre of rooa (sampÌedto a depth TuberInítìarkn and Farnation of r n) of 6c1d-growncomoon milkwccd d..tincd fam Ìate May to June,with a shup decline to about I 07o in JuÌy, Undersuitablegrowingcondidons,a shootemerges from ud jncrearedto â plât€âu (25olo)in octobcr (Bhownik a ruber 4 to 7 d after planting. Tuber formation beginsfrom r970). 4 to 6 wk after seedlingemeLgence. Usually, more rhan 95olo The disribution of totaÌ sugârsvâri€d betweenplâDr of purple ald ycllow nutscdgeubers are lormed in the uppârts.The total sugarconrcntiD the stcm bse repÍesenred per 45 cm oí soil (Belìet al. 1962:Tripathì 1969).In gen17.4 to 23.2o/oof the toral dry weighr of this plant pan er3Ì,more than 80o/ooftubers occurin úe uppeL15 cm of (Bhowmik 1970). Sugrs peüed in the stem basein July, soil. Rhircmes,in generaì,do nor penerraredeeplyin heary foÌÌowed by a sÌight reduction in Àugusr and September. The total reducingsugn (total glucoseand fructose)in The tuber productionofnutsedgeis remuLable,and the Ìootstocks of commorÌ rniÌkweed Lemainedfa;rly omtant crrcrr of,uber forma,i"nin J 8i\c,,s(r"oni. \(ry (\rcnrirc (Bhardwaj and Vermâ 1968; Hâoser 1962i HoÍowitz 1972. throughoutrhe growingseasonand rangedbetween0.48 to 2.2o/oof the total dry weight (Bhowmik 1970).The non plant produced Smirhdd Fick 1937).One yellownutsedge reducingsugãr(sucrose) conüibuteda mâjorponion of rotal i,900 shootsând 7,000 tubers in 1yr (TumbÌesonand susarsin common miÌkweedroo*tock (Bhowmik 1970). KonmedahÌ 1961). Under similar conditìons,fcwer and The seasonalvariarions in roor resenesclearly demonsrrare smallertubersareproducedby yellowthanpurplenutsedge. úe sourcc+ini!rlationsLip in coomon oilkwccd. Thc conHaNc (1962) found thar puryÌc truscfue plnlts fLom tuceprofsource-sinkrelationshipcould be ued to designsys- bers planted 90 cm apart overÌappeclin 5 wL. Áfter 20 wk rcoic heLbicidesfor perennial weed control. ï hen eppficaof growth, approximately5,700 km ha Ì of rhi.zoneshad 352 . WecdScience 45, May Jure 1997 becr produred.Bó<J o" our !udi" ì" Mo':.hu crs yeÌ pr"du.eds -any a. l0 'o l< rnìllionruber" low ' r Inur'edge t u p f c r. c L m . o i ) i n d g r o w ; n g . e à ' o n . VarioJs lactors influence überi'zâtioD of nutscdgesPecies. Tub€riation ìs the result of a responseof mrrsedgeplants regula.ed br gror.rh'ub'rrn.e" and rn eqe+,:.hohytlra-e. of Dho,ôpirioJrnd rcnrpera'urcluberÍor ro inLera.rionr shon m.rion,n velow nu'.edgeit inflrrened L1 da1rerrgrh. phororyrioJ'rimulrreJ reprodu.ri..gromh rtsel'ct 'ì ì962:lans! 1971).Iì}ìizonesdiffcrcntiatcinto tubersr*h uÉo ro 'h"n hulb' in pLnr. gruwnwirl, , phoropcrioJ "'| ' h, rrrJ rrouhiz"me' diÍ-crenriare i-'o ba-l bulb' under a p l ' o r n p c r i ol odn s c r h a nl 2 | . Ü d n . e nl r ) - l ) l o n g P h o roo-i..{,nd h,sh nìrroeenlcr<l' ìnhibircJrube'i2r:"nof f.ilo* nu''.dge'C,,g.i Jl. lr)o-i. H"he\er' low nirrogen prornor.dtubcriaiev.t'.ombin.d wirL hieh rc r,crarure .l-"' ro, tuberi-riÒnol r i-o""i", i .l.o -ron.Shadine (Kaley a;d Thullen i978) In an ÌÌlinois yello* '"nìy oi""tsàge on'inuou.,nnr qrrhuurrdcquac nur*dgecon' r r o l ,r u b e rd c n . i r i e . : n , r e r c 'da p i d y r r r r l r eÍ i n r ' c n o n : rhen, the densiq' rerminedat abãut 1,000 tub€rsm':fòr dre next 3 yr (StoÌlerer al. 1979). Day lengthdoesnot influencctuberforr:rationin purple * n'".h x nr yellow nnrìèdse.Hotowiú (1972) ".."ág" apparenteÍlec ofa naturâlphotoPeÌiodoí 10 to found no 14 h on túeriarion in purple nutsedgeln Isracl,establ'.herlpìanr.lormedmore,h,,, 200 new rube' rntl b,vi r H o , o w i r r/ ' , b 5 Jl.n L ' e n r g i P , .ì r n r e d , u ul b u , b .: bcrsol r,urplt nuoedecprodu.edl.(roubulb' ,ì-d 1.J00 )0.\ ,Êeì plrri"g. w,rh a dry wershr"lJ lg -1,",, (Mtr.rdô r979). m, rn ong rhc 'pecie.m.rybc rcLredro f:rru rcid'. ììpid' or and webcr lo74). ug.^ in rube^ iSroLler Ttber Sproutìng \pf,uí:ns o ruben i. .egulared b1 apirì d"mìnrn'e r u b e r ' n r h c . h a i r rr' p i " atlu J ' p u r p l ã r u r * d e e a l i c d \\rrfi of m"re ol rhe rrLer 'pr"ui trri,. ;'rhrhlingde'clopmenr distant buds. \íiú an intact nerwork,quiescenrbuds and chain tubem remin viabiliry while renÌainingdornÌant tor prolongedperiods(Mercado1979iStollcL€r â1 1979iWilÌs 1987). Y . l ì o wn u r * J e eb u d t . u r . r r r r t , c" p i r l e n d" f ' u b t n -u..dg. r"berubrei, rwill. r' :i. lo8'0t.BrJ. n 1el.o" order.rarrirrgwirh he olde't tb-r' dornr:n.r in a,ropcraJ peul) bud. turple nut'c,leebud'.lu"o "r rJ'cn"d- rìong i h e c n . i r el e n q r ht l " u . u l ò ' e . r . ì 1 < r r . l h ( b u d e \ r i h i r ' apic,rÌdominancesincc the most apical buds sprout and úhibit sproutingof the morc basìpetalbuds (Loustalotet al. 1954:Smith and Fick 1937). Under lavohble conditions, sprouting can ocou and a shooremergesin 4 to 7 d. Shootdoelopment is raPid ln lìeld studiei, shootsemergefrom tubers a lar as 45 cm ,oronr betowrìrc."iÌ surfa.crHorow ? tq65ì.Tngeneruì. e i. ,'a'er íio' i' hrgher:nd rhoor mergen. ing peicenrâgr ". c. lpíour,ngcd o(\ uÍ ruber.lora'edclo\en,o rhe\orl\urlr\ at differenttimesduring úe growingseasonYellownutsedqe rub"- , 'n .prnlr ,, le.nlhree.eprrrrcrime'.con.u-inS mor rhan<,0o"ofrh. dry reiglr r.rrbohydrrr,oil 'r"r.h and protein) on the Íìrst sproutìng fhe secondsptouting useslessther 1070 of theseconstiruentsduring rhe next rycle((StolleÌcr rì. lq72). sDroudne ' \ellownur*dgeruben. ìerì1 Ji.ph1 'c^onrì dornran.y. havingÌargenunbos of mbersoveminteringwìth a higher Tubet Langeu;tr percenrJqe rq rnanrnn'eprodr.<Jin . u' o prouungLJprL In eeneral, rubers rernain dormant in soiÌ tor cxtended iu-- Lú' :ea" , d ú"|.", to-o; srn ln and V/ar lq-J, -I"mbles"";".ì p e r ì o d il." n g , ' i r r o f r u b e n i n r r e r o r ' d e p r hi n ' o i l i n Kommedahl 1961). In Minncsotâ, onÌy 4 arrd 6 'uben a ,lfìife oÉ rus,dgc had \.llo; i*^",. 12oloof fall-harvestedrubers sprouted comparedrvnh 95olo cly.irrr r'.n. rop. ', ironmen, ol tl'o- l'*csted io the sprins (Tuoblcson md Konnte ,"" ar l0 âno20, m. ,e.pecri. in Illinois (StoÌlerand \74 Ì973). Howevet,rn conutuous dahÌ 1962). Purple nutsedgedoes not show any seasonal corn, moderateÌyinfested with yellow nursedge,at least2 yr dormancy,as tuberscollectedall yearround from plantsof .ontroÌ *ere requiredro nJute tub" pnprno mo^rerrperrrr-c v 'ri^u.,e.. 'proutedundcrrrvorable "i.cr'"rJo'rg uìarion'ro 20ìoofrhe originrrden':ry.uhìleJ vr o rrcar- 'u'. .onJi'i"n.. N(wl) forìed rubcr ot purptenur.cdge nenr reducedtubersby another57o (StoÌÌcret aÌ. 1979). sprcutedreadilnshowingno season:rÌ dormancy(Horowitz Other studies have shown that ycllow nutsedgetubers do 1972). This rype of infòrmation on seâsonaldorDìancy nor li\e onc in 'oil /Thuli,n rd KeeÌello-<ì couÌd be ioportant in intesmtingapproaús thit mey diDnine tubcn lrom rheirn.,urrl rarc I 8<oowrrertro prioririeson depÌetingor inhibiting rect weedmanagement mois- speciâctubersthrough interferingwith dormmcy. aboui 15% ''.ist"re will kill úem, and intermediace rure contents resulted il reduced viability (Rao ard NagadcF râjân Ì962i Smirh and Fick 1937).IÌì yeÌlowrÌuts€dge, FutureResearchNeeds iccatione*ily kìlled tuben nr Illinois (Stoller 1981), but Às weedscientjstsmoveinto a transitionperiod,research did not aJIecttubersfrom California,Florida,or SouthAÊ rica ecotypes(Dav and Rrxsll I955; Thônd 1969). eflons mrxt focusto unde*tand the bcic bìologyofweeds. L"neme temp"',t"'." can ldlÌ both yellow ano purpre Biologicalattributesúar are*sociatedwith survivalofweed must be closelystudied.Methodsmust be developed nutsedgcrubers (Day and Russeil Ì955r Thomas 1969; species to predicthow wecdspeciesor populations,nrduding bioThomas and Hcnson 1968). Yellow nutsedgcruberscan withstand lower temperaturesúan purple ntttsedgetubers. rypes or ccot,?es, evolve in Ìespotse to selection PressüÌe DeLker(1997) via agricuÌturalpracticcs.In this syrnpos;urn, In a Ìaboratorystudy,50% of tlre purpÌe and yelÌow nutemphasized the importanceof weedcliversiryin wccd mansedgetuL,emwerc kiÌÌed at 2 xnd 7 C, tespecrìveÌy(Stolltubers agement systems.Uldersranding the genetic diversity and cr i973). Hôweveain rhe feld, someyellownutsedge Doeulari"nqenerL vrucrure miqhr Haideour deci.io-r tolerated-20 C during wìnrer (Stoller1973).Cold hardi' ,t. 'lei, or riìini"f ,he u'e of hcrbi.idc.. ness of variour ecorypesol yellow nutsedge may pl:ry an "t'.'' "rlo,"' piodu,ri"rr ol l""d an.l hL,enool'- ro"rrd À rhe within and imponant roÌeiD longevìtyoftubers.Diflerenc.es \íeed biology:lnponancero rvecdmanage'nent' Bhowmikr 353 grearer \u.,ain'biì'1.weedmdnagerenr ,y.rem,$iìi be.uh red ro mJn) in,ca,J dd e\rernrÌ,o-,.ninr.. t he,ema1 ',, 'h.rrpìylirNr rhe ,Jngcot $eeo(un,rol me,hod,. "varlabl< Thu'. re-ar,h mu.r dnelop <n!i,o ', enrJly .rlr wccd Ínrnagem.n,,y\rem,. The I nuledg<o, seed I,iolog] sould helpin dc,igning,omeot r\c,ã *y,rem,. R*eu-h ,ÍÌ"'r. mu.r be errc,ded ro idclrif rherol<oi auxins,.dbÒhrdrarc rcrcncs, od cnvironmental factors and to understandthc mechanismof roor bud dormancl of common rniÌkweed.Sinilar dormarcy Drech.rnhms ofveg er"rircpr"prgule.olurhcr pcre"nial 'pc.ic,.ouÌd be "..d erploì,(d.UndersrdnJing ,he ,ì,cchJni.m dormJn.yol "t veserârive p,opâsJler will Jllô$- i-ins ôf m.nrg-m.n, pry Ine\. Iniorm ion o- ,l,c incìden.eor cn,roachmenr oI mosrpeÌennialweedspecies in Do-lill or reduceddilagesystems is ÌimiÌed. Each cropping syÍem dealswith speci6c ril[9. ooeraüon,inLtrrdì-gpri a4 r:tìagr.,c.orrdarlriurge. or r.du.cd .,lLge.FÍÌe.r,or rLc,cril'rge,yvem, on coÌonizationand persisrence of perennialspecicsmust be exmined. The informationon sparialdistributionofspecies woulct be of grearvalue in making decisionsfor weed rnanagement systenx. Spccilìc managernent mcr;cs could be basedon spatialdisuiburion. IÌ1 gen€ÌâI, rhere ir a need to develop managementstraregies for perennid weed speciesundcr an integrated pesr managemenrsysrern.Th€ inrerâctionsof frequencyof mowing, cuaing height, covercrop residues,and living mulch on population bioloy ol perennialweedsneed to be explored. As curtent reserrchresulb on weedseedbankdlnam (mdgcn.c.Jnd d^rmJ"cy ic,. i,ìJud;ngred diwrìburion. tu.ror'.begin," uniold.se mu., fo.u, úur arrerrionrn undenranJrhc dlnamia o'vcgerarive prop.rgules oipcrrnnìJ weed,pe.ie'.\Ìrirh úe rdvrncemenr o'der riledl-ow. edge about perennial weeds,researchefTorrsmust connnue to develop.effctivemanagemcut strategies lor perenniaÌspec1esrn vânouscroPprngsysrems. Linite<ì researchhasbeendone on ecotypicor biotypic variations of weed speciesto identify ecotypesof weed sp€cìesand Ìheir inÌeractionswirh variousenvironmental factors.VâriousenvirorÌmentshave diversccÍltcts on the physiologicalrcsponseofa speci{ìcecorype.Effors shouÌd be made to deveÌopa systemto categorizerhe ecorypesof each species.A geographicaÌdistÌibution of ecotypes could be developcd in reÌar;on ro climaric regions, nations,and rcgionswithin a nar;on. Such identification of ecotypeswould allow us to developtargetedmanageMoÌccularbiolosic.l rechniqucscould be usedin rhe investigationof ecorypesor bior'"es (Deld.er 1997; MilleL 1996; Nissenet al. 1995). NÌssenet â1.(1995) indÌcaterl thât DNA-bâsed mârkeÌ systemscouÌ<Ìbe usedto determine genetic diversity of weedy species.The information Íiom theselypesof studiescouÌd be usedin biocontroÌpractices or ìl othcr alrcrnativemaìagementpÌacticesappropriat€foÌ Researchefforts must continúe to exploÌe weed seedtank dynamicsand its impÌicationsfôr predictìngweedseedling emeÍsence.AÌúoueh we havevarious models (Bridgeset al. 1989:Forcellaet al. 1996;HaLveymd ForceÌla1993rMohler Ì993) ro prcdict weed seedgerminationor seedÌing emergence,we need to redirect our eÍ+oftsro úe thesemodeh in designingweed managemenroptioDsthat rcsuli in 354 . 45, May-june1997 \íeed Science optimization of production inputs. Integraredapproaches that direct priorities toward dcplering weed seedbank rhroughin,.,le,in8s irh dormJncyor gcrm,ìarionrequiKT(n,. h've gredrpo,en,idlro c h.nce we(d mdJgemenr srrategresior agnculrurâl sl.srems, Finally, our researchefforts must focus on economrc dnát),:.n, weedminJgemcn,ry.,em. if wc rn ro n.rk< d c c r . ' o no' n g f a r r rìr, , p u r ,i , , \ - . r J i n i b l (J g r i . "p'imizir . , r r , u - c f. c o r o m i . . " ú . , , . , . i b e b a , c do n r h . e . r r o Ì d w€ed managcmenrmethods. These methods musr be basedon rhe effectsof rhresholdrnanasementon weed population dynamics.To deveÌoprhe populârion-dynamics models,we need der.il.d ìnlormâtion oD weed seed o r o d u c r ì o n . . e dc id, p c - , a s' .e e dl o n t s e \ i D r n. d m o \ e m e n , uÍ .erd. o. kgerâ"e p,op.,guìcr in .oiì. ì he.ea.pc.r.of $crd dc, ograph).on,ri,:re: prrr ofweeJbioio$. \xecd b i oo g y i . Í c b J , i . i " r .,n"g.-.", e".i .. tt. ",.d biolog1of wced. murr be unJenrood :nd rppropriare managemcntstrategiesmust be developedbasedon cur, rent and future knowÌcdge. Acknowlêdgment MssiclÌusetB AgrlcúlturãÌ E+ernnenr Shtìon Journ.l ArÌi.l€ No.3i16. LiteratureCited ÂberÌdÌt l. R. ând D. C. Bridg.s. Ìt96. ResearcÌì priorìq' dy&mi.s in veed 6cien.e.\íea1Te.1ìnôI.3:396 399. BeÌI, l{. s., \í. H. Ldrnd, E. M. Rilìn, rìd R. D. Swee..1962.Life Historf SrudicsâsR.litcd rô WeedConlol in the Northeët. Ì. nuË gns. KingsÌÒn, RI: RIo{Ìc Isltrnd ÁgÍicultuRl Expeinetrt Srârion Bú1. 364. 33 p, B€non,D. L, 1986.Methodsof snìpling s€edbantr in dhlc vìils rviú spaiãl Êfetei.e Ìa Che"apodi,z ç1. rh.D. úesis, Univdsiq ofve$ em Ontarìo,lotrdon, CâMdâ. 283 p. BlÈd*âj, R.B.r. ind R. D. Vcih!. 1968.Sasonald*elopmar of nu. sd$ lqrp?n' ní'nà* L.) úd{ Delhi con<litioN. Ìrìdìd J. Ágric5cì. l8:9t0 9t7. 'IlÌe BhoMrik, I C. 1970. bioloPJ:Õf únnóí ni,\kwccd Açkpi6:!iaú l.) ând its respors to 2,4-D. 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