PREFACE TO CHAPTER 7. strong deep taproot that can regenerate. Dandelion physiology, phenology and

Transcription

1 PREFACE TO CHAPTER 7 Dndelion hs een reognized s signifint weed with ompetitive nd dptle ilities. Dndelion hs two mjor ompetitive fetures: the high seed prodution nd the strong deep tproot tht n regenerte. Dndelion physiology, phenology nd reprodutive ility flutute within the growing seson. Applition time is often the key to suess with ny ontrol option. Timings tht mth the sesonl limte onditions for superior effiy of S. minor nd the wekest stge in the life yle of the host plnt re prmount to suessful weed ontrol. Moreover suessful ioontrol gent should ontrol oth the oveground plnts nd elowground reprodutive prts. In Chpter 7 the popultion dynmis of dndelion, inluding the dndelion seednk nd root regrowth nd dynmis of other rodlef speies were investigted in three-yer field study. The timing of two weed ontrol methods, the S. minor ioontrol nd the stndrd hemil heriide were ompred. The results of Chpter 7 hve een prepred in mnusript form to e sumitted to Weed Siene. The mnusript is o-uthored y Professor Aln K. Wtson, my supervisor. I designed the experimentl set-up, performed the experiments nd the sttistil nlysis, nd wrote the mnusript. Professor Wtson supervised the work, provided finnil nd tehnil resoures, nd orreted the mnusript. 148

2 CHAPTER 7 Popultion dynmis of Trxum offiinle nd other rodlef weeds in turfgrss s influened y hemil nd iologil ontrol methods nd different sesonl pplitions MOHAMMED H. ABU-DIEYEH nd ALAN K. WATSON Deprtment of Plnt Siene, MGill University, 21,111 Lkeshore Rod, Ste.-Anne-de-Bellevue, Quee, Cnd, H9X 3V9 149

3 7.1. Astrt A three yer field study ws onduted to determine the effet of iologil ontrol gent, Slerotini minor nd ommon heriide on the popultion dynmis of dndelion, on the dndelion seednk, nd on the popultion dynmis of other rodlef speies. Tretments were pplied s one spring, one fll, or one spring plus one fll tretment per yer. The response of the dndelion popultion to spring heriide tretment ws similr to two pplitions (spring & fll) per yer. Signifintly less dndelion ontrol ourred fter the first fll pplition. A similr redution in the dndelion popultion density ws otined two weeks fter S. minor pplition with either spring or fll tretments, inditing no effet of sesonl limte vrition on effiy of S. minor nd ny progressive effet on the dndelion popultion ws more likely to e explined y the physiology nd phenology of the plnt. Compred to the heriide tretment effet, S. minor hd similr effets on the dndelion popultion size strting from the seond yer under the two pplitions of S. minor per yer tretment nd dely up to the third yer under the one spring pplition of S. minor. One fll pplition of S. minor ws similr to the heriide ross the study period, ut it ws the lest effetive during the seond yer ompred with spring nd spring & fll pplitions. The S. minor tretments signifintly redued the dndelion seednk nd this effet ws not signifintly different from Killex heriide tretment effet. The rte, frequeny nd sesonl timing of pplition hd no effet on the dndelion seednk size, ut terminting the pplition would grdully replenish the seednk. Popultions of Trifolium repens, Plntgo mjor, Lotus orniultus nd Amrosi rtemisifoli were similrly suppressed y either the S. minor or the heriide tretments. 150

4 Oxlis strit signifintly inresed fter one yer of heriide tretment ompred with the S. minor nd untreted ontrol tretments, inditing the risk of speies shift towrd more heriide tolernt weed speies. Turf qulity ws improved due to heriide nd S. minor tretments, ut grss injury nd rgrss invsion were reorded in three (out of 18) heriide treted plots. Keywords: 2,4-D, iologil ontrol, popultion dynmis, Oxlis strit, Slerotini minor, seednk, Trxum offiinle, turfgrss 7.2. Introdution Turfgrss is vegettive ground over tht prevents soil erosion nd offers reretionl nd estheti enefits for the soiety (Berd & Green 1994). Most turfgrss environments hve weed prolems nd require degree of mngement to e funtionl nd esthetilly plesing (Mono et l. 2002). The need for regulr mngement nd mintenne of these res retes mssive turfgrss industry in North Ameri nd Europe. The nnul expenditure ws estimted to e $ illion in the United Sttes (Berd & Green 1994) nd the lwn re industry in North Ameri is expnding t rte of 5-8% per yer (United Sttes Environmentl Protetion Ageny 1999). Dndelion, strong olonizing nd ompetitive plnt, hs een reognized s signifint weed of lwns nd other turfgrss environments (Stewrt-Wde et l. 2002). It overwinters in the soil s seeds or perennil roots whih n resprout in the following spring (Cyr et l. 1990). My nd Septemer re peking months of nerly yer-round emergene of dndelion (Chepil 1946). 151

5 Repeted pplitions of dim (3,6-dihloro-2-methoxyenzoi id), phenoxy heriides suh s 2,4-D (2,4-dihlorophenoxy eti id) nd meoprop ((±)-2-(4- hloro-2-methylphenoxy) propnoi id), or omintion produts suh s Killex hve een widely used for dndelion nd other rodlef weed ontrol (Anonymous 1997). Despite the suess of the ove mentioned heriides in ontrolling rodlef weeds (Emmons 1995) their use on lwns hs ome under severe pressure from environmentl nd puli helth perspetives resulting in vrious levels of government enting legisltion inhiiting or nning the use of pestiides in urn res (Cisr 2004). Over reline on suessive nnul heriide pplitions in turfgrss is eologilly inevitle. There re ses of weeds with no known seletive heriide tretment, heriide resistne, nd shifts in weed popultion towrds more tolernt speies (Busey 2003). Consequently, reserh onto lterntive pprohes of ulturl nd iologil methods of ontrol hs een intensified (Kennedy & Kremer 1996; Hther & Melnder 2003; Lresen et. l. 2004). Slerotini minor hs een studied s possile ioontrol gent for dndelion (Ciotol et l. 1991; Riddle et l. 1991; Brière et l. 1992; Shnik et l. 2002; Stewrt- Wde et l. 2002). Studies hve een onduted with rley sed formultion of S. minor (IMI ) to evlute its effetiveness on rodlef weeds nd quntify possile eologil onsequenes in turfgrss environments. Field studies hve onfirmed the effiy of S. minor in ontrolling dndelion nd reduing rodlef weed ground over (Au-Dieyeh & Wtson 2006: Chpter 5). More over its effetiveness on dndelion seeds nd seedling estlishment without negtive impts on turfgrss ws lso explored (Au-Dieyeh et l. 2005: Chpter 9; Chpter 8). 152

6 It is diffiult tsk to hieve suessful weed ontrol due to ontinul hnges in weed popultions (Hrtzler 2000). In generl, ny weed ontrol method removes or suppresses trget speies, ut this tivity my result in modifition or disruption of the hitt of other orgnisms (Rdosevih et l. 1997). Bsilly n eologil pproh rodens mngement options nd dereses the proility of filure (Booth et l. 2003). Reserhers emphsized the importne of studying the dynmis of weed popultions or ommunities to roden the funtion of ulturl nd iologil ontrol options (Burpee 1990; Kennedy & Kremer 1996; Rdosevih et l. 1997; Cousens & Croft 2000; Hedrik & Goeden 2001; Busey 2003). The ioheriide pproh hs hd limited ommeril or prtil suess due to prolems with mss prodution, formultion nd ommeriliztion, nd persistene under hrsh environmentl onditions (Kennedy & Kremer 1996; MFdyen 1998; Chrudttn & Dinoor 2000; Hllett 2005). Bioontrol is suessful when the ioti omponents nd the environment intert in suh mnner tht weed ontrol or suppression ours (Kennedy & Kremer 1996). Applition timing is key ftor in ioheriide performne, not only euse of the need to mth the proper meteorologil onditions for miroil growth ut lso the need to mth the wekest eo-physiologil time of the trget plnt speies. The proper time is determined y interting ftors of pthogen, host nd environment. Given the high osts of suh progrms, the suess rte should e mximized nd this tsk nnot e hieved without understnding the popultion dynmis of the host plnt (Cousens & Croft 2000). Generlly few studies hve een done on popultion dynmis of dndelion under the effet of ontrol or mngement prtie (Drwent & Elliott 1979; Blkshw et l. 153

7 1994; Hrker et l. 2000; Crlssre & Krsten 2003; Froese & Vn Aker 2003). The eology nd popultion dynmis of dndelion in turfgrss systems under the influene of ioontrol gent hve never een investigted. In this study, we investigte the effet of S. minor (IMI ) rley sed formultion on the popultion dynmis of dndelion nd the onsequenes on ssoited rodlef turf speies with respet to sesonl timing nd in omprison with stndrd hemil tretment Mterils nd Methods Fungus formultion Slerotini minor (IMI ) ws isolted from disesed lettue plnts (Ltu stiv L.) from southwestern Quee nd the stok ulture ws mintined s sleroti t 4 o C. The myeli of the germinted sleroti were used to inoulte utolved rley grits ( mm dimeter) s desried in Au-Dieyeh nd Wtson (2006: Chpter 5). The S. minor grnulr formultion ws freshly prepred two weeks prior to tretment pplitions. Viility nd virulene of the fungl inoulum were ssessed prior to use on potto dextrose gr (PDA) pltes nd on exised dndelion leves. The dimeter of olonies nd lesions used y the fungus were mesured fter 24 nd 48 h of inution. Previous unpulished qulity ontrol studies indite vile thes to hve olony dimeters of mm fter 24 h nd mm fter 48 h nd virulent thes to hve n verge lesion dimeter >15 mm fter 48 h of inution. 154

8 Site desription The study site ws represented y lwn re of round 900 m 2 loted in the Mdonld Cmpus of MGill University, in Ste-Anne-de-Bellevue, QC (45 o 25'N ltitude, 73 o 55'W longitude, m elevtion). The field ws permnently demrked with metl posts nd plsti ropes for period of three growing sesons (2003 to 2005). The seleted lwn re ws on lomy snd soil (orse snd = 9%, fine snd = 82%, silt= 5%, ly= 4%), with ph of 6.6 nd 6.3% orgni mtter. The lwn hd reeived miniml mintenne mngement throughout its history exept for repeted mowing during the growing seson (My to Otoer). The grss swrd ws pproximtely 90% Kentuky lue grss (Po prtensis L.) nd out 10% red fesue (Festu rur L.). The lwn flor ws highly diversified with 18 rodlef weed oserved throughout the study period nd the dominnt weed speies ws dndelion (Trxum offiinle Weer ex Wiggers). The level of infesttion rnged from medium (40 to 60 dndelion plnts per m 2 nd 30 to 60% grss ground over ) to severe ( dndelion plnts per m 2 nd 10 to 20% grss ground) Experimentl design The experiment ws rndomized omplete lok design with six replitions nd two ftors. The first ftor ws time of pplition with three levels; () spring (15 My); () fll (15 Septemer) nd () spring & fll pplitions per yer. The seond ftor ws weed ontrol tretment with four levels; () untreted ontrol, () rodst folir pplition of KILLEX [2,4-D (95g/L); Meoprop (isomer-d 50g/L); Dim (9 g/l) ll present s mines. The Solris group, Ontrio Cnd] heriide t 1.7 kg.i. h

9 (200 ml m -2 of 0.6% of originl onentrtion), () rodst pplition of grnulr formultion of S. minor t 60g m -2, nd (d) the S. minor formultion t 120g m -2. The heriide ws rodst pplied onto the grss surfe using 1.18 L vuum spryer (Home nd Grden spryer. Model no RLF10-Mster Premium. Root-Lowell Mnufturing Co, Lowell, MI). The S. minor formultion ws rodst pplied using 200 ml plsti ottle fitted with perforted lid (~10 mm dimeter) with suitle openings to pss the rley grits. If there ws no rinfll on the dy of pplition or the grss ws not wet, the entire field ws sprinkler irrigted for two hours prior to lte fternoon tretment pplitions. The tretments were pplied during 2003 nd 2004, ut in 2005 the tretments were modified to 40g m -2 of the S. minor formultion insted of either 60g or 120g m -2 nd no heriide ws pplied. The rtionle of these hnges in the third yer were to evlute lower ioheriide rte fter dndelion suppression to more norml levels enountered in weedy home lwns (20 to 40 plnts m -2 ), while esstion of the heriide pplition ws to evlute the re-oloniztion of weeds fter two yers of hemil tretment. The experimentl unit (plot) ws 1.0 m 2 with 0.8m lleys etween ny two plots. The distne etween ny two loks ws 4 to 5m. The orners of eh plot were permnently mrked to mintin plot integrity for the durtion of the study. Plots were mowed regulrly s needed t medium utting height of 7 to 10m with gs powered rotry push mower. Grss lippings were returned during July nd August to t s soure of nitrogen (Kopp & Guillrd 2002), ut removed during other months during the six-weeks-post tretment periods to prevent ontmintion of djent plots. The field reeived one fertilizer (C-I-L Golfgreen Lwn Fertilizer , Nu-Gro IP In., 156

10 Brntford, ON, Cnd) pplition per yer (t the eginning of Otoer) t 7 kg per 400 m 2 s reommended y the mnufturing ompny. The numers of dndelions nd other rodlef weed speies were ounted nd the totl perentge ground over of rodlef weeds were estimted in eh plot the dy efore the weed ontrol tretments nd the lst week of eh month therefter. For Trifolium repens L. (white lover), the numer ws estimted y mesuring how mny 10 m dimeter pthes of white lover overed the ground of plot. In order to monitor post tretment reovery of dndelions, 10 dndelion plnts in eh of the fungl treted plots were rndomly mrked using white olored pins prior to tretment pplitions. In eh monthly ssessment survey, turfgrss qulity ws visully ssessed using growth rting of 0 to100 sed on omintions of olour nd density where 0 = no growth nd 100 = ompletely uniform turf (Johnson nd Murphy 1992). As the study sites re lowmintined turf, the eptle visul qulity ording to the sle used is 50%. No mowing ws done in 2005 prior to the 15 th of My to void utting the florl spes of dndelion. The numer of flowering spes in eh plot ws ounted to investigte the extent of the impt of the pst two yers of tretment on the predispersed reprodutive efforts of dndelions Effet of S. minor tretment on dndelion seed nk To investigte the effet of weed ontrol tretments on the dndelion seed nk, Soil smpling ws done in the middle of August 2004 nd This ws to void pek periods of dndelion seed prodution, whih re expeted minly during My to June nd infrequently in Septemer with very rre sttered fruits formed in the summer (July to 157

11 August). Ten soil ore smples per plot ( totl of 72 plots) were tken rndomly with 2 m dimeter uger down to 10 m depth. Soil smples were spred in trys nd left to dry t room temperture for one week period then onentrted y sieving through ourse (2 mm mesh size) nd fine (0.355 mm mesh size) sieve, to remove root nd vegettive prts nd needless orse nd fine soil mterils (Ter Heerdt et l. 1996). This methodology retrieved ll dndelion seeds whih were previously mixed with soil in positive ontrol tretment. Eh of the onentrted smples ws then spred out into lyer of pproximtely 5 mm thikness onto trys (45 x 25 x 8 m) filled with 2 m depth of moistened pro-mix soil (Premier Promix, Premier Hortiulture Ltee, Riviere-du- Loup, QC). The trys were ompletely rndomized nd left under greenhouse onditions t 24 ±2 o C with 15 hr of light/dy t minimum photon flux density of 350 ±50 µ mol m - 2 s -1. The soil ws mintined moist y regulrly misting wter over the soil. Four ontrol trys ontining only the pro-mix potting soil were distriuted rndomly to test for possile soil ontmintion y dndelion seeds (dt not presented sine no seedlings germinted). To ssess for the effet of the soil nd experiment onditions on seed germintion, 25 dndelion seeds were sown in eh of four positive ontrol trys ontining the pro-mix potting soil. Eighty to 90% germintion ws otined from the positive ontrol trys nd this rte is within the norml germintion rte reported for dndelion seeds from severl studies s reviewed y Stewrt-Wde et l. (2002). The trys were heked dily nd emerged dndelion seedlings were ounted nd removed. The experiment lsted for one month s no further seedlings emergene ws reorded. The whole experiment ws repeted for soil smples olleted from the sme plots in August

12 Sttistil dt nlysis Sttistil nlyses were onduted using the SAS sttistil pkge (SAS Institute In., Cry, NC, USA, 2002). To overome the differenes in the dndelion density ross loks, dt were djusted s perentge of pre tretment dt olleted on 15 My Normlity for eh prmeter ws tested on model residuls using the Shpiro- Wilk test. Dt of the three-yer-monthly ssessments for weed ounts nd plot diversity were nlyzed using GLM proedure of repeted mesures to determine the signifint intertions mong tretment ftors through time. White lover density dt were trnsformed s (log ) to hieve normlity. Dndelion regrowth nd florl spe ount dt were nlyzed using ANOVA for rndomized lok design. The seednk density dt were squre root trnsformed to hieve normlity, then min effets of pplition time nd weed ontrol tretments were tested using ANOVA of SAS. A pired t-test ws used to ompre the seednk density dt etween the two yers for eh tretment omintion. Tukey s test (SAS) t P = 0.05 ws used to seprte the mens for ll nlysis with signifint effets (SAS Institute In., Cry, NC, USA, 2002) Results nd disussion Dynmis of dndelion popultion under no weed ontrol tretment Meteorologil dt of the study sites reveled slight monthly vrition in temperture nd reltive humidity etween the three studied yers. The totl mount of rinfll from My to Otoer ws 1308, 1286 nd 1523mm for 2003, 2004 nd 2005 respetively. However the monthly rinfll vried gretly etween the three yers (Tle 7.1). July nd August were the months of highest temperture with minimum temperture of 7.7 o C, 159

13 mximum of 32.1 o C nd n verge rnged etween 19.3 to 22.2 o C. However the high nd repeted preipittion in those two months uffered the verge reltive humidity to round 70%. The high rnges of temperture nd reltive humidity previled within eh of ll studied months (Tle 7.1). The dndelion popultion remined reltively stle ross the three yers with two mjor peks in My nd Septemer (Figure 7.1). In 2005, there were no frosts in April (verge monthly temperture ws 7.5 o C) so dndelions emerged erlier from the over wintered perennil roots thn in the previous yers. In April 2005 the dndelion popultion size ws similr to wht ws reorded in July nd Novemer 2004 nd round 50% of the popultion reovered fter the winter. In My the popultion ws omposed of well estlished plnts nd seedlings. Seedling reruits were the highest in My followed y erly June (Au-Dieyeh & Wtson 2006: Chpter 5) nd this inresed the popultion drmtilly during My forming the first pek. As temperture inresed in July the popultion ws redued y pproximtely 40 to 60%, susequently the popultion inresed grdully to form nother pek in Septemer. In Septemer dndelions were more roust thn in other months nd the popultion ws of mixed ges nd it ws diffiult to distinguish newly estlished dndelions from old plnts. A grdul derese in the popultion ourred in Otoer followed y prominent redution in Novemer due to the old (verge temperture ws 2.5 o C for Nov 2005). While the low popultion size in Novemer nd April is minly due to old tempertures, the popultion redution in July nd erly August ould not only e explined y high tempertures. In 2005, smll redution in dndelion density ourred in July (pproximtely 20%) ompred with the sme month in the 160

14 previous yers. This redution ould e ttriuted to the high preipittion reported in June 2005 (Tle 7.1) whih enourged new seedling reruits into the popultion. Mture dndelion seeds n germinte nd produe seedlings throughout the yer (Chepil 1946; Mrtinková & Honëk 1997; Collins 2000). Dndelion seeds germinte over wide rnge of temperture from 5 to 35 o C (Mezynski & Cole 1974; Hoy et l. 2004) with est germintion under lternting tempertures nd light (Stewrt-Wde et l. 2002). The survivl of dndelion seedlings deresed with high tempertures with 30% survivl t 31 o C nd 20% t 36 o C (Hoy et l. 2004). Even though the high temperture in July nd August ould e hrmful to the dndelion seedling popultion, frequent high rinfll events during the seson my intert positively fvouring dndelion germintion nd seedling estlishment. Vegettive reprodution from tp root frgments n lso ontriute to the inrese in dndelion popultions (Mnn & Cvers 1979). In ropping systems tht involve soil mnipultion prties, root frgmenttion n signifintly inrese dndelion popultions. Seprtion of rmets ours nturlly fter dey of the tissues tht onnet them nd the longevity of onnetions etween rmets determines the suess of persistene of the genet (Booth et l. 2003). Vegettive reprodution of dndelion from tp roots in turfgrss environment my id in dndelion persistene s result of mowing, mnul erdition of tp roots, nd frost. Other studies reported dndelion emergene nerly yer-round with two peks in My nd Septemer (Chepil 1946), ut the rte of inrese for n entire popultion ws the highest in fll (Vvrek et l. 1997). Our results from three yers dt reveled tht dndelion densities were similr in My nd Septemer regrdless of ioti or ioti 161

15 ftors. This implies tht the vulnerility of the popultion to environmentl seletive pressures is very low nd even thought the popultion flututed within the yer it ws mintined ross the three yers. No signifint redution in the dndelion popultion ourred under two suessive growing sesons of regulr mowing t different heights (Chpter 6). Geneti vriility within dndelion popultions ws found to e n effetive tool in regulting the popultion through different degrees of ompetitiveness nd survivl in response to pressures from interspeifi ompetition (Vvrek 1998) nd disturnes (Solrig & Simpson 1974) Effet of hemil heriide tretments on the dndelion popultion The spring heriide tretment hd n immedite diret effet in the first yer, while the fll tretment redued the popultion drmtilly in Otoer, ut out 70% of dndelion popultion reovered in the following spring (My 2004) (Figure 7.1). The result of the seond fll pplition ws effetive nd not signifintly different from other heriide tretments (Figure 7.1). Importntly, fter the seond fll pplition, the popultion size inresed in mid My of the following yer (2005) nd then diminished t the end of the month without ny weed ontrol tretment. This mortlity ws more likely to e explined y persistene of the heriide residuls from lst fll tretment. The response of the dndelion popultion to two pplitions per yer (spring & fll) of Killex ws lmost similr to one spring pplition (Figure 7.1). Applitions of 2,4-D use severl metoli hnges in ommon dndelion root tissues prtiulrly the depletion of rohydrte reserves (Deon & Rutherford 1972) Perennils rely on these reserves to overwinter (Wilson & Mihiel 2003) nd dndelion 162

16 llotes more resoures for flowering nd vegettive growth in the spring (Cyr et l. 1990). Sesonl hnges in rohydrtes of dndelion roots hve een reported y Wilson et l. (2001) with more monoshrides s perentge of totl sugr in spring nd more frutn polymers s the seson progressed towrds the fll. However, freezing soil tempertures re ssoited with inresed frutose nd deresed frutn s perentge of totl sugr (Wilson et l. 2001). The vilility of rohydrte reserves in dndelion roots limited the response of these roots to 2,4-D throughout the seson, therefore optimum ontrol of dndelion in lwns ws hieved y spring pplition of 2,4-D omined with spudding (Mnn 1981). Our results indited tht more suessful hemil ontrol of dndelion ould e hieved y spring thn fll pplition. The sesonl hnges of rohydrtes in the root system is resonle explntion ut other fts ould lso e involved suh s younger plnts trnslote heriides fster thn do older plnts (Crfts 1961), nd the response of plnts to 2,4-D depends ritilly on the stge of development whih determines the rte of penetrtion nd trnslotion of the heriide (Tomkins & Grnt 1974). Unfortuntely the ge struture of the popultion ws not investigted, ut similr to wht ws reported y Roerts & Nelson (1981), more seedlings onstituted the popultion in My nd June thn in lter months nd this supports the effetiveness of spring pplition. Wilson & Mihiel (2003) suggested ontrol strtegy for dndelion nd Cnd thistle y pplying heriides, like dim nd 2,4-D in lte fll, 10 dys fter the first frost whih ws ompnied y redued quntities of low degreepolymerizing frutns nd onsequently hieved etter ontrol thn when dim ws pplied 11 dys efore the frost. Even though this pplition time is not omprle to 163

17 our study, the results we otined in the third yer support the importne of the umultive effets of heriide residuls nd frost on well estlished dndelions Effet of S. minor tretments on dndelion popultion The meteorologil dt for the 14 dys fter tretment pplition re summrized in Tle 7.2. The differenes etween spring nd fll tretments in temperture, reltive humidity (RH), dew point, nd even rinfll did not use signifint differenes on the effiy of dndelion ontrol two weeks fter pplition of S. minor. The rinfll ws the most vrile ftor, ut the field ws irrigted when there ws no rinfll on the dy of pplition nd two dys lter. In generl, moisture is n importnt requirement for mny pthogens nd is known to enhne the effiy of S. minor (Melzer & Bolnd 1994). Thus ording to our limte dt, the S. minor formultion ws effetive in field onditions with men dily tempertures from 9 to 20 o C; men dily RH ove 58%, nd dew point rnge from 3.6 to 17.4 o C. Unfortuntely, soil moisture ws not monitored in this study, ut plots were irrigted during dry periods to void moisture stress. In the fll of 2003 nd 2005, hevy rinfll events ourred four to five dys fter pplitions nd there ws no effet on the effiy of S. minor s y tht time the infetion ws lredy estlished. The ioontrol produt ws rinfst nd ws not moved off trget. In the first yer, the spring Killex tretment ws signifintly more effetive thn the S. minor tretment (Figure 7.2). Unlike the heriide, the fungus hs no residul tivity nd hs mostly disintegrted within 10 dys fter pplition. Therefore lering oveground popultion two weeks fter pplition indued seedling reruitment from the soil seednk (Au-Dieyeh & Wtson 2006: Chpter 5). A perentge of vegettive 164

18 regrowth from the non killed roots ould lso ontriute to popultion size. The reruitment size ws round 40 to 50% of the pre-treted popultion size nd diminished during the summer (Figure 7.2). Estlishment of dndelion seedlings deresed when tempertures inresed to 30 o C or more (Hoy et l. 2004) nd this temperture ws enountered in mny dys during July nd August. Interestingly August, insted of Septemer, ws the pek month nd then the popultion size diminished even though there ws no S. minor fll pplition. This redution ws more likely due to mortlity s result of dry onditions tht previled in August 2003 (53 mm totl rinfll) or improvement of grss vigour fter lering most of the well estlished ompetitive dndelions y spring S. minor pplition. Dndelion seedlings re less ompetitive in superior grss qulity turf (Molgrd 1977; Ford 1981). In the seond yer nd prior to the spring pplition of S. minor, seedling reruitment ws expeted ut seond pplition resulted in level of suppression tht ws not signifintly different from the heriide nd previled ross 2004 nd 2005 (Figure 7.2). The effet of the fll tretment strted within two weeks fter the Septemer pplition nd signifintly redued the dndelion popultion ompred with the untreted ontrol (Figures 7.1 & 7.2). In the seond yer, signifint level of popultion suppression (pproximtely 60%), similr to the Killex tretment, ourred from My to July, ut in August the suppression ws miniml (Figures 7.1 & 7.2). However, the seond fll pplition ws effetive into the following yer (2005) nd ws not signifintly different from the heriide tretment. Clerly, spring & fll tretment per yer of S. minor ppers neessry initilly for the high level of infesttion enountered 165

19 in the studied field, ut susequent pplitions ould e minimized in frequeny or rte to ontrol future reruited popultion. In nother study exmining the effet of pplition time on the effiy of S. slerotiorum on Cirsium rvense (Hurrell et l. 2001), less effetive ontrol ourred with lte summer nd utumn pplitions thn with spring pplitions. The uthors suggested tht free moisture in the utumn promoted effiy, ut the intense rinfll fter tretment redued effiy through wsh off (Hurrell et l. 2001). In our study s the S. minor hd similr effiy on dndelion 2-weeks post spring nd fll pplitions thus ny progress differene in dndelion popultion ould e ttriuted to the physiology nd phenology of dndelion rther thn sesonl limte vritions. Our results illustrted tht some dndelions hd the ility to regrow fter omplete oveground dmge nd the extent of regrowth ws signifintly lower fter spring (pproximtely 10% of the popultion) thn fll pplition (Figure 7.3). While no signifint redution on regrowth perentge ws reorded ross the yers for spring tretments, the redution ws signifint fter fll tretment in 2005 nd redued to 10% ompred with the pst two yers (2003 & 2004) when the regrowth ws 20 to 25%. However, vritions mong plots of the sme tretment were oserved to e importnt nd the regrowth perentge ws highly determined y grss qulity nd density, thus we seprted the first yer regrowth (%) dt ording to first yer verge turf qulity (%) vlues to two sets of dt, visully epted turf qulity ( 50%) nd poor turf qulity (30 to 40%). In superior grss qulity plots the regenertion of dndelion roots redued signifintly in either of spring or fll tretment pplition (Figure 7.4). 166

20 Previously, we presented the impt of grss ompetitive environment ompred to grss free environment on root regrowth of dndelion fter S. minor infetion under greenhouse onditions (Chpter 3) nd lso the effet of seson-long mowing t the lose height (3-5 m) followed y S. minor tretment on reduing root regrowth even though this tretment ws ompnied y signifint inrese of dndelion reruitment. Supporting our results, dndelion root frgments derived from soure plnts t the time of flowering in My, hd very little survivl (Mnn & Cvers 1979). Fll tretment pplition seems to intert with S. minor effiy in similr mnner to wht ws explined for 2,4-D effiy nd the previously disussed sesonl hnges of root resoure llotions of rohydrte reserves were the mjor explntion (Mnn 1981; Cyr et l. 1990; Wilson et l. 2001). Our results re onsistent with Green et l. (1998) who studied the regenertive pities of four phenologil stges of Rnunulus ris, gint utterup (perennil weed) rowns fter S. slerotiorum infetion nd found tht regenertion ws lest fter tretment t pre-flowering stge nd gretest t 32 to 38 weeks post onset of flowering. The uthors orrelted the lowest regrowth of preflowering stge to depletion of rohydrte reserves in the rown (Green et l. 1998). In greenhouse onditions, we reported less survivl of flowering plnts thn vegettive 13- week-old plnts fter S. minor spot pplition even though the tested flowering plnts were older (Chpter 3) nd similr results were otined with Phom glomert on dndelion (Neumn & Bolnd 2002). Regrown plnts fter S. minor tretment hve shown to e wek with short tp roots (Au-Dieyeh & Wtson 2006: Chpter 5) nd ompnied y severe redution in lef nd root iomss even for 13-week-old plnts (Chpter 3). Our results stress the need of 167

21 mnipulting interspeifi ompetition to fvour turfgrss over dndelion nd onsequently inrese the ompetitive pressure on dndelion roots pre nd post S. minor infetion. This ould e hieved y inresing grss density nd hoosing highly ompetitive turf speies or ultivrs. In generl, n dditionl ontrol mesure my e needed to inrese stress on weeds using ioheriide-sed ontrol (Hsn & Ayres 1990; Hther & Melnder 2003). However, regrowth should e investigted with respet to ntomil nd iohemil hnges in the rown nd root of dndelion due to S. minor infetion Effet of S. minor pplition rte The preliminry unpulished dt out the reommended field rte of S. minor rleysed formultion ws 40 to 60g m -2 depending on the level of the dndelion infesttion. The infesttion in our field rnged from medium, 40 to 60, to severe, 80 to 120 dndelion plnts per 1.0 m 2 nd so we pplied 60g s relile rte for extremely infested lwns with history of low-mintenne. The urrent populrity of inundtive iologil ontrol my result in prolems, s n inresing numer of tivities will e exeuted y untrined people (vn Lenteren et l. 2003). Due to the ove reommendtion we introdued 120g m -2 to evlute ny onsequenes for misusing the formultion. No importnt signifint differenes were otined in ny of the studied prmeters y using 120 insted of 60g m -2 (Figure 7.2). No impts on turfgrss or onsequenes on weed speies omposition were oserved due to the 120g m -2 tretment. Moreover, pplying the lower rte (40g m -2 ) in the third yer on ll S. minor treted plots, fter the popultion hs een suppressed to round 20 dndelions m -2, hd similr effets to wht ws 168

22 otined with the higher onentrtions in the pst two yers (Figure 7.1). Our suggestion is tht, the field reommended rte of S. minor is highly determined y the level of dndelion infesttion nd turfgrss qulity nd lthough 60g is n effetive rte in the worst turf qulity, the minimum optimum rte is diffiult to predit ut should e lower Consequenes of tretments on popultion dynmis of other weeds July ws the month of the highest diversity of rodlef weeds with rnge of 3 to 8 speies m -2 nd n verge of 4 to 5 speies m -2 (Figure 7.5). Reltively high temperture nd rinfll were reorded during July nd these ftors ould e involved in flourishing other rodlef weeds prtiulrly fter the ompetitive pressure hd een relesed from dndelion s dominnt speies during this month. Even though Trifolium repens nd Plntgo mjor were less undnt thn dndelion, they still hd high temporl nd sptil frequeny even when dndelion popultion size ws in its pek (Figure 7.6). These two speies were shown to exert ompetitive responses nd ompetitive effets with dndelion nd my e lssified s importnt ompetitors due to similr rosette growth form of plntin nd tp root of white lover to dndelion (Vvrek 1998). Both S. minor nd heriide tretments signifintly redued the diversity of rodlef weeds (Figure 7.5), prtiulrly in the third yer nd under the spring & fll per yer tretment. However, tendeny of inresing diversity ws oserved in August 2005 in the Killex tretment. It is importnt to note tht there ws no pplition of Killex in 2005 nd so the dte from lst spring tretment ws 14 months nd from the fll tretment ws 10 months. The reported dt for 2,4-D hlf-life persistene in soil is 169

23 vrile nd rnged etween 2 to 269 dys (Cox 1999). The inresed plot diversity of heriide treted plots ws minly due to grdul disintegrtion of heriide residuls whih my enourged other weed speies to germinte under new environment of no or limited undne of dndelion. S. minor nd heriide tretments were highly effetive, not only in suppressing dndelion popultion, ut lso in signifintly reduing other perennil weeds like Trifolium repens, Plntgo mjor, Lotus orniultus nd Amrosi rtemisifoli (Figure 7.6). The suppression of the ove mentioned weeds ould e ttriuted to the diret effet of the tretment or to the new improved grss qulity or more likely to oth ftors. However, ll speies were reorded to e suseptile to spot pplition of S. minor (Chpter 4). Other rodlef speies like Medigo lupulin (lk medi), Pyrrhopppus rolininus (Crolin flse dndelion), Cerstium fontnum (mouseer hikweed), nd Vii stiv (ommn veth), were suppressed under oth S. minor nd Killex tretments, ut the rre sptil or temporl undne of these speies mde their dt not llowle for sttistil nlysis. Importntly, the undne of Oxlis strit signifintly inresed under the heriide tretment (Figure 7.6). We reported erlier from nother study site the signifint inrese of Mlv neglet density nd the inrese in men vlues of Oxlis strit nd Polygonum viulre under heriide tretment (Chpter 6). A shift in weed popultion under heriide tretment in turfgrss ws reported y Johnson (1982) who found minor weeds hnged to mjor weeds due to suessive nnul heriide tretment. The frequent use of 2,4-D s erly s 1950 hd shifted ropping systems from rodlef weed to nnul grss domintion (Aldrih 1984). Weed shift ours when 170

24 weed mngement prties re not eqully effetive nd so ertin iotypes or speies survive, however ftors tht ffet germintion, emergene, seedling survivorship nd seed prodution ould e ontriuted to weed shift mehnism (Hilgenfeld et l. 2004). Even though weed shift fter hemil mngement prtie hd reeived more onerns due to the possiility of weed resistne or tolerne, however weed shift ould our s result of periodi ulturl mngement prties like mowing nd fertiliztion in turfgrss (Busey 2003) nd tillge in other ropping systems (Bll 1992). Oxlis strit is prominent her with underground perennil rhizomes nd n eret hit (Doust et l. 1985). Comintion of the sme heriides s in Killex ws found to e ineffetive in ontrolling Oxlis strit in turfgrss (Bing & O Knefski 1980). This evidene my explin the inresed undne of this weed in the heriide treted plots nd indite risk of weed shifts due to repeted Killex pplitions Consequenes of tretments on turfgrss Within eh of the three tretments: spring, fll nd spring & fll, S. minor nd Killex pplitions improved the turfgrss qulity in similr mnner (Figure 7.7). With the spring nd spring & fll tretments, signifint improvements of turf qulity ourred diretly six weeks fter pplition while the fll tretment ws delyed to Septemer 2004 (Figure 7.7). Turf qulity improvement ws more likely to e orrelted with mgnitude of suppression of dndelion popultion rther thn pplition timing, frequeny, or S. minor onentrtion. Bsilly, vegettive turfgrss growth ilities inrese fter weeds hve een ontrolled (Turgeon 1985). Grss injuries due to Killex pplition were oserved in two plots (out of six) fter spring & fll tretment nd in 171

25 nother plot fter fll tretment. These plots were lso invded y Digitri ishemum, (smooth rgrss) in 2004 nd The grss injury ws more likely to pper in plots with low grss qulity, during summer months nd fter the seond pplition. It is importnt to note tht the studied turf is low-mintined stnd nd the grss injury ws more due to stressful effet of exessive use (two pplitions per yer) on poor qulity grss. Grss injury ws not oserved in ny of S. minor treted plots ross the study period Consequenes of tretments on dndelion florl spes nd seed nk At the onset of flowering in My 2005 nd prior to ny tretment pplition or mowing prtie, dndelion florl spes were found to e signifintly redued in ll S. minor nd heriide treted plots ompred with the untreted ontrol (Figure 7.8). No further flowering ross the seson ws oserved in the treted plots. However sttered flowers, with more frequeny in Septemer, were oserved in the untreted plots. Dndelion hs mjor pek of seed prodution nd dispersl in spring nd with infrequent nd sttered flowers over the entire seson, ut minly in Septemer (Gry et l. 1973; Stewrt-Wde et l. 2002). The low numers of florl spes ws due to popultion size redution nd prtiulrly to the low proportion of well estlished plnts s reorded in the April 2005 ssessment (Figure 7.1 & 7.2). The results my indite shift in the surviving popultion towrds younger popultion due the tretments over the pst two yer. Newly emerged dndelions loom in the spring of the following seson nd some plnts n flower in their first yer under optimum onditions (s reviewed y Stewrt-Wde et l. 2002). The reprodutive stge of dndelion is mjor ontriutor in its weediness 172

26 nd the most undesirle prt of dndelion life yle euse of estheti prolems in lwns (Holm et l. 1997). A severe depletion in the dndelion seed nk in the upper 10 m soil lyer ourred fter S. minor pplitions (Figure 7.9). In 2004, the verge seednk density in untreted plots ws 2737 seeds per 1.0 m 2 while the seednk in S. minor treted plots ws signifintly redued (P = 0.001) ompred with untreted plots with n verge redution of 73%. Generlly, within S. minor tretments, no signifint differenes of seednk densities were otined due to the two inoulum onentrtions (60 nd 120 g m -2 ) or due to time or frequeny of S. minor pplition (Figure 7.9). The vrition in seed nk densities within S. minor tretments ws minly due to inter-lok vritions in infesttion level. The hemil heriide exerted the strongest impt on seednk density with n verge redution of 88% ompred to untreted plots. There were no differenes due to different pplition times. In most tretments, no signifint differenes were reported etween heriide nd fungl tretments (Figure 7.9). However removl of the heriide tretment in 2005 led to signifintly higher seednk densities thn 2004, lthough it ws still signifintly less thn untreted plots. The tretment pplitions were strted in spring 2003 thus treted plots reeived either one, two or three pplitions ut no signifint differenes were otined due to the numer of pplitions. Under the S. minor tretments, there ws no further signifint derese in seed nk size in 2005 ompred with We onluded tht one pplition of S. minor ws enough to redue dndelion seednk, ut to mintin long-term redution suessive nnul pplitions should e done. 173

27 2,4-D is the min effetive ingredient of Killex nd is known to persist for severl months in the soil (Ross & Lemi 1999) with hlf-life rnging from 2 to 269 dys (Cox 1999). Sine no heriide tretment ws pplied in 2005, the durtion from lst 2004 tretment ws 14 nd 10 months for spring nd fll, respetively. The signifint higher seednk otined under spring thn under fll tretment ws more likely to e due to differenes in the durtion from lst tretment. Spring is the seson of dndelion seed rin nd two sesons hd pssed fter the spring tretment while only one seson hd pssed fter the fll tretment. Dndelion seed nk ws estimted to e 1,575,000 seeds per h in the top 13 m of grsslnd re nd 2,350,000 seeds per h in the top 18 m of n rle field (Chmpness nd Morris 1948). Germintion of dndelion seeds ws fster nd more in light onditions thn in the drk (Lethmo & Gosselin 1996). The onditions of uried seeds re unfvourle to seedling development nd the light is neessry to indue their germintion (Noronh et l. 1997). The estlishment suess ws negtively orrelted with depth of seed uril (Bostok & Benton 1979) nd 1 to 6% of seeds remined vile fter four yers of uril in soil (Chepil 1946). The soil seednk is soil reservoir opened for oth proesses of deposits nd withdrwls (Hrper 1977). Seednk deposits our through seed prodution nd dispersl while withdrwls our through germintion, predtion, senesene nd deth (Rdosevih et l. 1997). Reduing dndelion densities in treted plots my led to less seed prodution ut this ould do minor nd temporry effets on seednk density sine dndelion seeds re wind-dispersed nd ompenstion from lose res ould shortly our nd replenish minor withdrwls. 174

28 We suggested tht S. minor my kill seeds present in the soil surfe lyer nd so redued further deposits in the seednk. This suggestion ws presented in other studies (Au-Dieyeh et l. 2005; Chpters 8 & 9). However seednk depletion ould lso our from extensive repeted withdrwls due to reruitment from dndelion seednk fter S. minor tretment. In onlusion, S. minor hs no residul tivity nd one month fter pplition dndelion popultion hs the ility to persist in suppressed level minly due to seedling reruitment. Root regrowth ws minor ompenstive for popultion size fter S. minor tretment with signifintly less vlues in superior turf qulity plots, fter spring thn fll tretment, nd in the third yer. Our findings demonstrted the effetiveness of S. minor tretment on dndelion seed output whih my ssist in reduing its estlishment through uilding strong perennil tp roots. Therefore sustntil ioontrol enefit n rise over long term fter reduing old dndelion popultion through repeted pplition of S. minor, susequent improved turfgrss ompetition nd ontinuous exhusting of seednk. 175

29 Tle 7.1. Wether dt for Ste-Anne-de-Bellevue, Quee during the yers of study 2003, 2004, nd Environment Cnd Meteorologil Dt. Ste-Anne-de-Bellevue Sttion. Temperture o C Reltive humidity ( %) Rinfll (mm) Totl monthly Month / yer Averge Min Mx Averge Min Mx My My My June June June July July July August August August Septemer Septemer Septemer Otoer Otoer Otoer

30 Tle 7.2. Meteorologil summry during the 14 dys fter spring nd fll pplitions (verged ross the three yers 2003, 2004 nd 2005). Temperture Reltive humidity Dew point Totl Rinfll ( o C) (%) ( o C) (mm) Spring Fll Spring Fll Spring Fll Spring Fll Averge Min Mx

31 Figure 7.1. Effet of sesonl heriide nd ioheriide pplitions on dndelion popultion dynmis. Within eh grph, mens with ommon letter t eh time re not signifintly different t P = 0.05 ording to Tukey s test. Asterisks (*) refer to the pre-tretment ssessment in the middle of My. (1) Killex rte = 1.7 kg.i. h -1. (2) S. minor rte = 60 g m -2 Dndelion density (% of pretretment density) Killex (Heriide) (1) M* M J J A S O N M* M J J A S O A M* M J J A S O Untreted Fll Spring Spring & Fll S. minor (Bioheriide) (2) M* M J J A S O N M* M J J A S O A M* M J J A S O

32 Figure 7.2. Effet of spring versus fll weed ontrol tretments on dndelion popultion dynmis. (A) spring (B) fll nd (C) spring & fll per yer. Within eh grph, mens with ommon letter t eh time re not signifintly different t P = 0.05 ording to Tukey s test. Asterisks (*) refer to the pre-tretment ssessment in the middle of My. (1) Killex rte = 1.7 kg.i. h

33 A d d Untreted Killex TM(1) S. minor (60 g m -2 ) S. minor (120 g m -2 ) Dndelion density (% of pretretment density) M* M J J A S O N M* M J J A S O A M* M J J A S O B M* M J J A S O N M* M J J A S O A M* M J J A S O C M* M J J A S O N M* M J J A S O A M* M J J A S O

34 Figure 7.3. Regrowth pities of dndelion roots fter spring nd fll pplitions Slerotini minor. Error rs refer to stndrd devitions of the mens. Vlues re the mens of 12 plot replites. Brs with ommon letters re not signifintly different t P = 0.05 ording to Tukey s test After spring pplition After fll pplition Regrowth of dndelion (%)

35 Figure 7.4. Regrowth pities of dndelion roots ording to plot grss qulity. Error rs refer to stndrd devitions of the mens. Vlues re the mens of 5 plot replites. Within sesonl pplition time, rs with ommon letters re not signifintly different t P = 0.05 ording to Tukey s test After spring pplition After fll pplition Regrowth of dndelion (%) Low qulity grss High qulity grss 182

36 Figure 7.5. Effet of sesonl heriide nd ioheriide pplitions on rodlef weed speies diversity. (A) spring, (B) fll nd (C) spring & fll pplition (s). Within eh grph, mens with ommon letter t eh time re not signifintly different t P = 0.05 ording to Tukey s test. 183

37 184 M J J A S O M J J A S O M J J A S O Untreted Killex TM (1.7 kg.i. h -1 ) S. minor (60 g m -2 ) M J J A S O M J J A S O M J J A S O Brodlef weed diversity (No of speies m -2 ) M J J A S O M J J A S O M J J A S O A B C

38 Figure 7.6. Effet of heriide nd ioheriide pplitions on the popultion dynmis of seleted rodlef speies. Within eh grph, mens with ommon letter t eh time re not signifintly different t P = 0.05 ording to Tukey s test. (1) density ws estimted y mesuring how mny 10 m dimeter pthes of white lover overed the ground of plot. 185

39 Trifolium repens (1) Untreted Killex TM (1.7 kg.i. h -2 ) S. minor (60 g m -2 ) M J J A S O M J J A S O M J J A S O Plntgo mjor Popultion density (plnt m -2 ) M J J A S O M J J A S O M J J A S O Lotus orniultus M J J A S O M J J A S O M J J A S O Am rosi rtem isiifoli M J J A S O M J J A S O M J J A S O Oxlis strit M J J A S O M J J A S O M J J A S O

40 Figure 7.7. Effet of sesonl heriide nd ioheriide pplitions on turfgrss qulity. (A) spring, (B) fll nd (C) spring & fll pplition (s). Within eh grph, mens with ommon letter t eh time re not signifintly different t P = 0.05 ording to Tukey s test. (1) visul rnk sle of 0 to 100% ws used with 0% for no grss nd 100% for optimum grss qulity. 187

41 100 Untreted Killex TM (1.7 kg.i. h -1 ) S. minor (60 g m -2 ) S. minor (120 g m -2 ) A 0 M J J A S O M J J A S O M J J A S O 100 Turf qulity (%) (1) B 0 M J J A S O M J J A S O M J J A S O C 0 M J J A S O M J J A S O M J J A S O

42 Figure 7.8. Numer of dndelion florl spes enountered fter two yers of weed ontrol tretment (H = heriide; B1 = 60g m -2, nd B2 = 120g m -2 S. minor ioheriide) nd different sesonl pplitions (S = spring; F = fll, nd S & F= spring nd fll per yer). Averge of six replitions. Within eh yer, mens followed with the sme letter do not signifintly different (P = 0.05) y Tukey's test No of florl spes m Untreted S-H S-B1 S-B2 F-H F-B1 F-B2 S&F-H S&F-B1 S&F-B2 Tretments 189

43 Figure 7.9. Effet of heriide nd ioheriide pplitions on the dndelion seed nk in the upper 10 m soil lyer in 2004 nd (S = spring; F = fll nd S&F= spring nd fll pplition time) nd different weed ontrol tretments (H = heriide; B1 = 60g m -2 nd B2 = 120g m -2 S. minor ioheriide). Averge of six replitions. Within eh yer, mens followed with the sme letter do not signifintly different (P = 0.05) y Tukey's test. Dt etween 2004 nd 2005 re (*) signifintly different t P = 0.05 nd (**) t P = Dndelion seednk (seeds m -2 ) m no ** no n p * op no op n n 0 Untreted S-H S-B1 S-B2 F-H F-B1 F-B2 S&F-H S&F-B1 S&F-B2 190