Mechanical and chemical control of the invasive cordgrass Spartina densiflora and native plant community responses in an estuarine salt marsh

106 J. Aqua . Plan Manage. 50: 2012. J. Aqua . Plan Manage. 50: 106-111 Mechanical and chemical con ol o he in asi e co dg ass Spa ina densi lo a and na i e plan communi y esponses in an es ua ine sal ma sh En iquE Ma Eos-na anjo, jEsús CaMb ollé, juan Ga Cía dE loMas, aquEl Pa a, and susana Edondo-GóMEz* Abs Ac he sou h ame ican co dg ass, Spa ina densi lo a, has in- aded a wide ange o sal ma sh a eas in sou he n spain. a ield expe imen o examine physical and chemical con ol o S. densi lo a, including mowing, he bicide (glyphosa e), mowing plus he bicide combina ion, and he b eaking o hizomes, was conduc ed in low-g adien ma sh in aded by S. densi lo a o ind a means o con olling his in asi e spe- cies. he g ow h pa ame e s o densi y, as well as species ich- ness and di e si y, we e used o assess he e icacy o di e - en ea men s in decembe 2007 and 2008. all ea men s educed li e ille densi y o S. densi lo a a e 1 and 2 yea s o ea men . Compa ed o he con ol, he educ ions in ille densi y wi h hizome b eaking, mowing plus he bicide, mow- ing, and he bicide applica ion we e 85, 65, 56, and 38% and 66, 70, 52, and 52% a e 1 and 2 yea s o ea men espec- i ely. despi e a educ ion in S. densi lo a abundance, none o he ea men s e adica ed his species comple ely. Howe e , hizome b eaking and mowing plus he bicide ea men s p o ed o ha e he highes con ol e iciency, and plo s ea - ed wi h hese ea men s con ained he highes alues o na- i e species ichness and di e si y. Key wo ds: b eaking hizomes, he bicide, in asi e species, ma shes, mowing In oduc Ion he sou h ame ican co dg ass, Spa ina densi lo a b ongn. (Poaceae), is in ading sal ma shes om sou he n Eu ope (Figue oa and Cas ellanos 1988), no h a ica (Fennane and Ma hez 1988), and no h ame ica (Ki elson and boyd 1997). in i s na i e sou h ame ica, S. densi lo a is a sal -ma sh dominan o e a wide la i udinal ange and exhibi s consid- e able mo phological a ia ion (bo olus 2006). i has been pos ula ed ha his species was acciden ally in oduced in o sou hwes spain by means o lumbe ade om sou h ame - ica. in sou hwes spain, S. densi lo a has eme ged as a igo ous in ade and ecosys em enginee ha sp eads by p oli ic seed p oduc ion and consolida es i s s ands by clonal g ow h. i can be a o midable compe i o ; i p oduces dense ussocks wi h all canopies and pe sis en ly high abo e- and below- g ound biomass (Figue oa and Cas ellanos 1988, Cas illo e al. 2008, Ma eos-na anjo e al. 2008). in asion by S. densi lo a is one o he mos impo an con- se a ion p oblems a ec ing he Gul o Cadiz in he sou h- wes e n ibe ian Peninsula because his species al e s he com- posi ion o plan and animal communi ies, educing hei biological di e si y (Ki elson and boyd 1997). i has become he dominan plan species on ecen idal ma sh es o a ions in he doñana na ional Pa k (Gallego-Fe nández and Ga cía- no o 2007), h ea ening o sp ead o o he ma sh sys ems in sou he n Eu ope. lea ning how o e ec i ely manage popu- la ions o S. densi lo a is i al; hus, esea ch mus be conduc - ed o ind me hods ha will ei he con ol o e adica e his species, as has been al eady sugges ed o o he species o Spa ina (an e al. 2007). Chemical and mechanical me hods may cons i u e an impo an ool o he con ol o S. densi lo a, as hey ha e o o he species o Spa ina (Pa en 2004, obe s and Pul- lin 2008). Hedge e al. (2003) explained he es ablishmen and conside able limi a ions o a wide ange o con ol ech- niques, including physical emo al, mowing, and he bicide, o he managemen o nonna i e Spa ina plan s (S. al e - ni lo a, S. anglica, and S. pa ens) in Washing on s a e. hey indica ed ha he combina ion o mowing and he bicide applica ion p o ided he g ea es con ol e icacy. Fo S. den- si lo a only long- e m looding and glyphosa e applica ion unde con olled en i onmen al condi ions ha e been s ud- ied as con ol echniques (Ma eos-na anjo e al. 2007, 2009). he e o e, he aims o his s udy we e o (1) e alua e he e - ec s o di e en me hods on he con ol o S. densi lo a un- de ield condi ions and (2) de e mine whe he hese con ol me hods lead o enhanced plan di e si y in he long e m o es o a ion o in aded a eas. MA e IAl And Me hods s udy loca ion his expe imen was pe o med a in o Ma shes, si ua ed on he join es ua y o he odiel and in o i e s nea he *Fi s , second, ou h, and i h au ho s: depa amen o de biología Veg- e al y Ecología, Facul ad de biología, uni e sidad de se illa, apa ado 1095, 41080 se illa, spain; second au ho : depa amen o de biología. Facul ad de Ciencias del Ma y ambien ales, uni e sidad de Cádiz. io san Ped o s/n, 11510 Cádiz, spain. Co esponding au ho email: [email p o ec ed]. ecei ed o publica ion july 7, 2011 and in e ised o m Feb ua y 7, 2012. J. Aqua . Plan Manage. 50: 2012. 107 own o Huel a, on he a lan ic coas o sou hwes e n spain (37°15’n, 6°58’W). he sal ma sh is subjec o a Medi e a- nean clima e wi h oceanic in luences. Win e is we and mild (mean empe a u e abou 11 °C in janua y) and summe is long and d y (mean empe a u e abou 25 °C). Mean annual ain all is 510 mm, wi h an in e annual a ia ion coe icien o 31%. he semidiu nal ides ha e a mean ange o 2.10 m and a mean sp ing idal ange o 2.97 m, ep esen ing 0.40 o 3.37 m abo e spanish Hyd og aphic ze o (sHz). Mean sea le el is +1.85 m ela i e o sHz (Ma eos-na anjo e al. 2008). o es he e icacy o he di e en me hods in he con- ol o Spa ina and he damage o na i e plan s, we es ic ed ou expe imen o low-g adien ma sh in aded by S. densi lo a wi h an a ea o 0.5 ha wi h a heigh di e ence o 40 cm be- ween i s lowe (+2.8 m sHz) and uppe (+3.2 m sHz) limi o s udy a ea. in his loca ion, S. densi lo a sha ed habi a wi h he na i e species Halimione po ulacoides, A h ocnemum mac- os achyum, Sa coco nia pe ennis, and Salico nia amosissima. [a de ailed examina ion o he physicochemical p ope ies o he s udy si e is gi en in able 1.] en i onmen al measu emen s En i onmen al soil cha ac e is ics we e analysed. Measu e- men s o sedimen conduc i i y, pH (n = 15), and edox po- en ial (n = 10) we e made in low ide on he uppe 10 cm a he sedimen in decembe 2006. Conduc i i y o sedimen was de e mined in he labo a o y wi h a conduc i i y me e (C ison-522, spain) a e mixing he sedimen wi h dis illed wa e (1:1; edondo-Gómez e al. 2007). edox po en ial and pH o he sedimen we e ob ained wi h a po able me- e and elec ode sys em calib a ed in he ield (C ison pH/ mV p-506, spain). soil wa e con en was de e mined om samples aken om he uppe 10 cm o sedimen (n = 15). samples we e weighed be o e and a e d ying a 80 C o 48 h. expe imen al design and ea men s in decembe 2006, nine eplica e plo s o 2.5 by 2.5 m we e posi ioned 2 m apa in he s udy a ea, and ou ea - men s (mowing, he bicide, mowing plus he bicide combina- ion, and he b eaking o hizomes) and one con ol we e andomly assigned o each plo . Mechanical ea men s (mowing and b eaking) o plo s we e ca ied ou by pe sonnel om he uni e si y o se ille using a ious hand-held b ush cu e s and sho els. all mow- ing plo s we e mown o wi hin 10 cm o he subs a e. Fo he b eaking o hizomes ea men , he abo e-g ound po ions o he plan s in he plo s we e emo ed and hen he below- g ound sedimen s, hizomes, and oo s we e dissec ed in o 20 cm long sedimen s wi h sho els. He bicide was applied homogeneously o he plo su ace using a backpack ag icul u al sp aye (Ma abi 5-l, Goizpe s.C., spain) wi h a hand-held wand and an adjus able b ass nozzle a a speed o 1 m s-1 and a a p essu e o 200 kPa (250 ml o sp ay olume). he he bicide used was glyphosa e a 7200 g a.i. ha-1 (Glialka® 36; 360 g a.i. l-1, P esma sl, spain). in he mowing plus he bicide ea men , glyphosa e was applied immedia ely a e 24 h o mowing a he lowes idal le el o p o ide he necessa y ime o he bicide up ake and ansloca ion. he chemical ea men was likewise pe - o med a low ides, allowing 3 o 6 h o d ying ime be o e inunda ion o 50% o he plan . Wea he condi ions we e op- imal, wi h ai empe a u es anging be ween 12 and 15 C and wind speeds om 0 o 5 Km h-1. also, in decembe he applica ion pe iod coincided wi h a pe iod o neap ides and wi h plan s d opping seeds and en e ing senescence (nie a e al. 2005). da a collec ion o es ima e he con ol e icacy, ou 0.2 by 0.2 m quad- a s we e andomly selec ed in each plo in decembe 2007 and 2008, and he numbe o li e ille s o S. densi lo a was eco ded. na i e species ichness and plan species di e si y we e measu ed o each ea men . species di e si y was cal- cula ed using shannon’s index (H’; shannon and Wea e 1949) o mula H’= −Σpi · lnpi, whe e pi = ela i e abundance o each species di ided by he o al numbe o species obse ed in each plo . s a is ical analysis s a is ical analyses we e ca ied ou using s a is ica . 6.0 (s a so inc.). da a we e analyzed using a one-way analysis o a iance (F- es ). da a we e i s es ed o no mali y wi h he Kolmogo o -smi no es and o homogenei y o a i- ance wi h he b own-Fo sy he es . We used a no mal e o dis ibu ion, so ali e ille densi y and na i e species ichness we e ln (x) ans o med, espec i ely, o one-way analysis o a iance. signi ican es esul s we e ollowed by ukey es s o iden i ica ion o impo an con as s (P < 0.05). esul s con ol o in asi e S. densi lo a all mechanical and chemical ea men s had signi ican e ec s on he con ol e icacy o S. densi lo a a e 1 and 2 yea s o ea men , wi h all ea ed plo s showing lowe li e ille densi y han con ol plo s ( able 2; Figu e 1). b eak- ing hizome ea men eco ded he lowes ille densi y o S. densi lo a a e 1 yea o ea men , ollowed by mowing plus he bicide, mowing, and he bicide ea men (Figu e 1). Compa ed o he con ol, he educ ions in ille densi y wi h hese ea men s we e 85, 65, 56, and 38% espec i ely. Table 1. Physicochemical P oPe Ties o The Th ee conT asTing siTes om TinTo ma shes. Values a e mean ± se o 15 ePlicaTes. excePT o edox PoTenTial (Val- ues a e mean ± se o 5 ePlicaTes in The uPPe and lowe limiT o sTudy a ea). Pa ame e alues Conduc i i y (ms cm-1) 15.6 ± 0.8 pH 6.7 ± 0.1 edox po en ial (mV) 87 ± 6.3 -146 ± 19.9 soil wa e con en (%) 27 ± 0.4 108 J. Aqua . Plan Manage. 50: 2012. Table 2. esulTs o a one-way analysis o Va iance (anoVa) o di e enT conT ol T eaTmenTs on s. densi lo a liVe Tille densiTy and sPecies ichness and naTiVe PlanT diVe siTy o T eaTed PloTs (shannon’s index, h´) one and Two yea s a Te T eaTmenT. T eaTmenTs: c, conT ol PloT; h, he bicide; b, b eaking hizome; m, mowing; and m+h, mowing Plus he bicide combinaTion. asTe isk indicaTe signi icanT di e ence; Tukey TesT, P < 0.05). 1s yea one way ano a d. . F P 2nd yea one way ano a d. . F P a iable ille densi y ( ille m-2) 4 67.60 0.000 a iable ille densi y ( ille m-2) 4 37.32 0.000 ea men C H b M ea men C H b M H 0.000* — — — H 0.000* — — — b 0.000* 0.000* — — b 0.000* 0.025* — — M 0.000* 0.006* 0.000* — M 0.000* 1.000 0.018* — M+H 0.000* 0.000* 0.000* 0.616 M+H 0.000* 0.000* 0.619 0.000* 1s yea one way ano a d. . F P 2nd yea one way ano a d. . F P a iable species ichness 4 9.59 0.000 a iable species ichness 4 8.40 0.000 ea men C H b M ea men C H b M H 1.000 — — — H 0.998 — — — b 0.002* 0.002* — — b 0.002* 0.004* — — M 0.006* 0.006* 0.986 — M 0.133 0.234 0.341 — M+H 0.007* 0.007* 0.976 1.000 M+H 0.003* 0.007* 0.999 0.473 1s yea one way ano a d. . F P 2nd yea one way ano a d. . F P a iable na i e plan di e si y 4 13.04 0.000 a iable na i e plan di e si y 4 6.55 0.001 ea men C H b M ea men C H b M H 0.954 — — — H 0.880 — — — b 0.000* 0.000* — — b 0.005* 0.041* — — M 0.011* 0.049* 0.341 — M 0.101 0.472 0.657 — M+H 0.001* 0.004* 0.941 0.803 M+H 0.004* 0.033* 1.000 0.597 J. Aqua . Plan Manage. 50: 2012. 109 Howe e , hizome b eaking ea men showed a ille densi y simila o mowing plus he bicide ea men a e 2 yea s o ea men (Figu e 1). a e 2 yea s, b eaking and mowing plus he bicide ea men s eco ded he lowes ille densi- ies (Figu e 1), wi h pe cen age educ ions compa ed o he con ol o 66 and 70%, espec i ely. He bicide and mowing ea men s each showed a ille educ ion o 52% and we e no s a is ically di e en ( able 2). ecoloniza ion by na i e ege a ion b eaking, mowing, and mowing plus he bicide ea men s showed he highes na i es species ichness a e 1 yea o ea men ( able 2; Figu e 2); howe e , di e si y alues we e no simila o hose o he mowing ea men due o he p es- ence o dominan species ( able 2; Figu e 3). a e 2 yea s, hizome b eaking and mowing plus he bicide ea men s showed he highes na i es species ichness (Figu e 2). hese ea men s also eco ded he highes di e si y alues ( able 2; Figu e 3). Finally, species ichness and di e si y alues o plo s ea ed wi h he bicide we e simila o he con ol plo as a consequence o he wide co e age by S. densi lo a. dIscussIon ou esul s show ha b eaking hizomes and mowing plus he bicide combina ion ea men s had he highes con ol e icacy on li e ille densi y o S. densi lo a compa ed o he con ol plo . Glyphosa e applica ion was he leas e icacious ea men (in e ms o au och honous plan species coloniza- ion), especially in some plo s whe e he co e age by S. densi- lo a was 100% (as happened in he con ol plo ). al hough glyphosa e did educe li e ille densi y, he shading e ec o he la ge numbe o dead and e ec ille s o S. densi lo- a migh accoun o he lowe p esence o o he species in he bicide ea men plo s. his species exhibi s a phalanx ype o g ow h cha ac e ized by he p oduc ion o dense us- socks, which can educe ligh a soil su ace and he eby in- hibi coloniza ion by na i e species (Cas ellanos e al. 1998). Ma eos-na anjo e al. (2009) demons a ed ha glyphosa e a doses as high as 7200 g a.i. ha-1 has a nega i e e ec on he pho osyn he ic appa a us and g ow h o S. densi lo a un- de con olled en i onmen al condi ions, so his may educe Figu e 1. li e ille densi y in ea ed plo s a in o ma shes 1 and 2 yea s a e ea men . ea men s: C, con ol plo ; H, he bicide; b, b eaking hizome; M, mowing; and M+H, mowing plus he bicide combina ion. Values ep esen mean ± sE, n = 36. di e en le e s indica e means ha a e signi i- can ly di e en om each o he (capi al le e s o i s yea and lowe case o he second yea o ea men ; ukey es , P < 0.05). Figu e 2. Mean species ichness in ea ed plo s a in o ma shes 1 and 2 yea s a e ea men . ea men s: C, con ol plo ; H, he bicide; b, b eaking hizome; M, mowing; and M+H, mowing plus he bicide combina ion. Values ep esen mean ±sE, n = 18. di e en le e s indica e means ha a e signi i- can ly di e en om each o he (one-way anoVa, species × ea men , p < 0.05). Figu e 3. na i e plan di e si y (shannon’s index, H´) in ea ed plo s a in o ma shes 1 and 2 yea s a e ea men . ea men s: C, con ol plo ; H, he bicide; b, b eaking hizome; M, mowing; and M+H, mowing plus he - bicide combina ion. Values ep esen mean ± sE, n = 36. di e en le e s indica e means ha a e signi ican ly di e en om each o he (capi al le - e s o he i s yea and lowe case o he second yea o ea men ; ukey es , P < 0.05). 110 J. Aqua . Plan Manage. 50: 2012. i s compe i i e abili y. Howe e , Pa en (2002) ound ha he ime be ween applica ion and idal inunda ion o e he canopy a ec ed he e icacy o glyphosa e in he con ol o S. al e ni lo a, and zana a e al. (2007) obse ed ha soil wa e con en in luenced he glyphosa e e icacy in he con ol o Eupho bia he e ophylla. hus, he e ec o en i onmen al ac- o s such as idal in luence and soil wa e con en could al e he e icacy o glyphosa e applica ion and pa ly explain ou esul s. in addi ion, o inc ease he e icacy o glyphosa e ap- plica ion, epe i ion o he ea men in subsequen seasons is necessa y, as p e iously sugges ed o di e en Spa ina spe- cies ( obe s and Pullin 2008) as well as o he in asi e species o we land ecosys ems (ails ock e al. 2001). Many s udies ha e demons a ed a iable esponses o Spa ina o mowing, depending on he species (li and zhang 2008, obe s and Pullin 2008). acco dingly, S. al e ni lo a showed a signi ican educ ion in he densi y wi h an o e all mean pe cen age decline o 68%, whe eas S. anglica and S. ownsendii showed an o e -compensa ion e ec wi h a mean inc ease o 42.8 and 14.7%, espec i ely ( obe s and Pullin 2008). Fo S. densi lo a, we eco ded mean pe cen age educ- ions o abou 56 and 52% a e 1 and 2 yea s o ea men , espec i ely. he emo al o abo e-g ound pa s by mowing migh ha e g ea ly educed he ene gy alloca ion o i s below- g ound s uc u es, leading o a educed eg ow h po en ial (Ha e kamp and Ka l 1999). Mowing was pe o med only once a he beginning o he expe imen , al hough epea ed mowing has been shown o e ec i ely educe g ow h in o h- e Spa ina species (li and zhang 2008). Majo e al. (2003) showed ha mowing migh be he leas e icacious con ol ea men o Spa ina al e ni lo a, he mos labou in ensi e, and he mos des uc i e o he su ounding mud la . Mo e- o e , i s e icacy inc eases wi h he equency o mowing and he use o la ge machine y, wo aspec s ha add up o g ea - e damage o he associa ed mud la . in addi ion, mechani- cal con ol me hods a e cos ly and equi e highly specialized equipmen (li and zhang 2008). he e o e, u he es ing o epea ed mowing is needed o be e assess he con ol o S. densi lo a wi h his me hod and asce ain whe he i cons i- u es a easible op ion. Finally, hizome b eaking and mowing plus he bicide ea men s educed he densi y o S. densi lo a be ween 85 and 65% a e 1 yea o ea men , and be ween 66 and 70% a - e 2 yea s. li and zhang (2008) obse ed simila educ ions o S. al e ni lo a ea ed wi h hizome b eaking in he i s season, bu g ow h had almos eco e ed o he con ol le el by he end o he second g owing season. o he echniques such as he use o o o- illing, has p oduced >90% e icacy o he con ol o S. al e ni lo a du ing win e ials bu was <70% e ec i e du ing sp ing ials (Hedge e al. 2003). in compa i- son, obe s and Pullin (2008) ound ha he use o mow- ing ollowed by glyphosa e applica ion dec eased he densi y o S. al e ni lo a by 91%. in con as , he same in e en ion, when used o con ol S. anglica, inc eased densi ies by 19% pe plo . Majo e al. (2003) ound ha one- ime mowing seemed o yield a mo e consis en ly uni o m applica ion o he he bicide and was likely o p o ide an ini ial educ ion in he plan ’s ene gy ese es be o e chemical ea men . Fu - he mo e, in hizome b eaking and mowing plus he bicide plo s, S. densi lo a was eplaced by a highe numbe o na i e species han in he bicide, mowing, and con ol plo s, esul - ing in he highes di e si y alues. conclusIons ou da a indica ed ha S. densi lo a has a s ong capac- i y o esis mechanical and chemical con ol in e en ions; a single applica ion o he a ious con ol echniques es ed in his s udy seemed incapable o e adica ing S. densi lo a and e u ning in aded ma shes o a p e-in asion s a e. Howe e , his s udy p o ides aluable in o ma ion o he managemen o his exo ic species in he in aded habi a s. hizome b eak- ing and mowing plus he bicide applica ion could be use ul o he con ol o he in asion o his species; bo h ea men s dec eased S. densi lo a biomass and a o ed an inc eased di- e si y and na i e species ichness. AcknowledgMen s We a e g a e ul o an onio j. uiz ico o e ision o he English in he manusc ip . We also hank he spanish En i- onmen al and science and echnology Minis ies o hei suppo (p ojec 042/2007 o ganismo au ónomo Pa ques nacionales and p ojec C M2008-04453). lI e A u e cI ed ails ock Ms, no man CM, bushmann Pj. 2001. Common eed Ph agmi es aus alis con ol and e ec s upon biodi e si y in eshwa e non idal we - lands. es o . Ecol. 9:49-59. an sq, Gu bH, zhou CF, Wang zs, deng zF, zhi Yb, li Hl, Chen l, Yu dH, liu YH. 2007. Spa ina in asion in China: implica ions o in asi e species managemen and u u e esea ch. Weed es. 47:183-191. bo olus a. 2006. he aus al co dg ass Spa ina densi lo a b ong.: i s axono- my, biogeog aphy and na u al his o y. j. biogeog . 33:158-168. Cas ellanos EM, He edia C, Figue oa ME, da y aj. 1998. ille dynamics o Spa ina ma i ima in successional and non-successional Medi e anean sal ma sh. Plan Ecol. 137:213-225. Cas illo jM, Ma eos-na anjo E, nie a Fj, Figue oa E. 2008. Plan zona ion a sal ma shes o he endange ed co dg ass Spa ina ma i ima in aded by Spa ina densi lo a. Hyd obiologia. 614:363-371. Fennane M, Ma hez j. 1988. nou eaux ma é iaux pou la lo e de Ma oc. na u alia Mon speliensia. 52:135-141. Figue oa ME, Cas ellanos EM. 1988. Ve ical s uc u e o Spa ina ma i ima and Spa ina densi lo a in Medi e anean ma shes, pp. 105-108. in : M. j. a. We ge , P. j. M. Van de aa , H. j. du ing, and j. . a. Ve hoe en (eds.). Plan o m and ege a ion s uc u e. sPb academic Publishing, he Hague. Gallego-Fe nández jb, Ga cía-no o F. 2007. 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Ma eos-na anjo E, edondo-Gómez s, luque Cj, Cas ellanos EM, da y aj, Figue oa ME. 2008. En i onmen al limi a ions on ec ui men om seed J. Aqua . Plan Manage. 50: 2012. 111 in in asi e Spa ina densi lo a on a sou he n Eu opean sal ma sh. Es ua . Coas . shel s. 79:727-732. Ma eos-na anjo E, edondo-Gómez s, Cox l, Co nejo j, Figue oa ME. 2009. E ec i eness o glyphosa e and imazamox on he con ol o he in asi e co dg ass Spa ina densi lo a. Eco ox. En i on. sa e. 72:1694-1700. nie a Fjj, Cas ellanos EM, Cas illo jM, Figue oa ME. 2005. Clonal g ow h and ille demog aphy o he in ade co dg ass Spa ina densi lo a b ongn. a wo con as ing habi a s in sw Eu opean sal ma shes. We lands. 25:122- 129. Pa en K. 2002. smoo h co dg ass (Spa ina al e ni lo a) con ol wi h imaza- py . Weed echnol. 16:826-832. Pa en K. 2004. Compa ison o chemical and mechanical con ol e o s o in asi e spa ina in Willapa bay, Wa, epo . he Washing on s a e de- pa men o ag icul u e. edondo-Gómez s, Ma eos-na anjo E, da y aj, Fe nández-Muñoz F, Cas- ellanos EM, luque , Figue oa ME. 2007. G ow h and pho osyn he ic esponses o salini y o he sal -ma sh sh ub A iplex po ulacoides. ann. bo -london 100:555-563. obe s Pd, Pullin as. 2008. he e ec i eness o managemen in e en ions o he con ol o Spa ina species: a sys ema ic e iew and me a-analysis. aqua . Conse . 18:592-618. shannon CE, Wea e W. 1949. he ma hema ical heo y o communica ion. uni e si y o illinois P ess, u bana, il. zana a jF, P ocopio so, Manica , Paule o Ea, Ca nelu i a, Va gas l, sganze la dC, osen hal Mda, Pin o jjo. 2007. soil wa e con en s and glyphosa e e icacy in con olling Eupho bia he e ophylla. Plan a daninha. 25:799-811. J. Aqua . Plan Manage. 50: 111-116 Response o a ge and non a ge loa ing and eme gen aqua ic plan s o lumioxazin CH is oPHE . MudGE and WilliaM . HallE * Abs Ac he e ec s o subsu ace and olia lumioxazin {2-[7- lu- o o-3,4-dihyd o-3-oxo-4-(2-p opynyl)-2H-1,4-benzoxazin- 6-yl]-4,5,6,7- e ahyd o-1H-isoindole-1,3(2H)-dione} ea - men s we e e alua ed on he loa ing weeds wa e hyacin h (Eichho nia c assipes (Ma .) solms), wa e le uce (Pis ia s a- io es l.), and landol ia (Landol ia punc a a [G. Mey] d.H. les and d.j. C aw o d) as well as he non a ge eme gen species eleocha is (Eleocha is in e s inc a (Vahl) oem & j.a. schul ), maidencane (Panicum hemi omon schul .), picke elweed (Pon- ede ia co da a l.), and sagi a ia (Sagi a ia lanci olia l.). all subsu ace ea men s (≥100 µg a.i. l−1) and olia applica ion a es >143 g a.i. ha−1 p o ided comple e wa e le uce con ol. Con e sely, bo h lumioxazin applica ion echniques p o id- ed <30% con ol o wa e hyacin h. no inju y symp oms we e exhibi ed by landol ia ea ed wi h olia lumioxazin applica- ions, and in wa e , concen a ions ≥200 µg a.i. l−1 we e e- qui ed o p o ide mo e han 50% con ol. sagi a ia was he mos sensi i e non a ge eme gen species o subsu ace lu- mioxazin applica ions, ollowed by maidencane, eleocha is, and picke elweed. sagi a ia d y weigh was educed 100% a he bicide concen a ions ≥800 µg a.i. l−1 compa ed o a 73 o 83% d y weigh educ ion in eleocha is, maidencane, and picke elweed. Con e sely, all eme gen species we e highly ole an o olia lumioxazin ea men s, yielding calcula ed EC50 alues ≥1320 g a.i. ha−1 o d y weigh . esul s o his s udy indica e di e en ial e icacy and selec i i y among loa - ing and eme gen a ge and non a ge aqua ic plan species when ea ed wi h lumioxazin. Key wo ds: chemical con ol, dose esponse, EC50: E ec i e Concen a ion 50, Eichho nia c assipes, Eleocha is in e s inc a, Landol ia punc a a, Panicum hemi omon, Pis ia s a io es, Pon ede- ia co da a, p o opo phy inogen oxidase inhibi o , Sagi a ia lanci olia, selec i i y In oduc Ion in asi e loa ing aqua ic plan s, including wa e hyacin h (Eichho nia c assipes (Ma .) solms) and wa e le uce (Pis- ia s a io es l.), sp ead by ege a i e ep oduc ion, o ming ex ensi e ee loa ing ma s ha o en in e e e wi h na i- ga ion, hyd oelec ic gene a ion, i iga ion, and ishing as well as lowe ing he dissol ed oxygen and pH o he wa e (Weldon and blackbu n 1966, Ha ley e al. 1984, owens and Madsen 1995). hey may also ha bo mosqui oes, which a e ec o s o diseases like dengue e e , mala ia, and encepha- li is (Holm e al. 1977). Con e sely, na i e eme gen aqua ic plan s may p o ide a di e se and aluable ood sou ce and habi a o animals, can imp o e wa e cla i y and quali y, e- in o ce sho elines, and p o ec soil agains e osion om wind and wa e ac ion (sa ino and s ein 1982, Hei meye and Vohs 1984, sma 1995, dibble e al. 1996). damage o eme gen non a ge and na i e plan s species is a majo conside a ion in he bicide selec ion; a o able aqua ic he bicides a e able o selec i ely emo e unwan ed plan s while minimizing dam- age o non a ge na i e plan s. one o he p ima y goals o aqua ic weed managemen is o con ol in asi e plan s while main aining a di e se na- i e plan communi y. na i e plan densi y and di e si y ha e been shown o inc ease when canopy- o ming exo ic plan s *Fo me G adua e esea ch assis an and P o esso , Cen e o aqua ic and in asi e Plan s, ins i u e o Food and ag icul u al sciences, uni e si y o Flo ida, Po box 110610, Gaines ille, Fl 32611. Cu en add ess o i s au ho : us a my Enginee esea ch and de elopmen Cen e , Vicksbu g, Ms 39180. Co esponding au ho ’s E-mail: Ch is ophe . .Mudge@usace. a my.mil. ecei ed o publica ion Feb ua y 10, 2012 and in e ised o m june 28, 2012. 112 J. Aqua . Plan Manage. 50: 2012. a e emo ed (Ge singe e al. 1997), and con inued p esence o na i e ege a ion allows di e si y o in e eb a e and ish habi a s o be main ained (dibble e al. 1996). he e o e, i is bene icial o selec i ely emo e loa ing in asi e species o main ain na i e ege a ion and, in u n, wildli e habi a . in 2010, lumioxazin ecei ed FiF a-sec ion 3 egis a- ion o con ol o subme sed, eme gen , and loa ing aqua ic weeds in he uni ed s a es (Valen usa Co po a ion 2011). Flumioxazin is a e y as -ac ing con ac he bicide ha in- hibi s p o opo phy inogen oxidase (PPo; p o opo phy in iX:oxygen oxido educ ase, EC 1.3.3.4). i inhibi s chlo o- phyll biosyn hesis by p e en ing ans o ma ion o p o o- po phy inogen iX in o p o opo phy in iX, a p ecu so o heme and chlo ophyll p oduc ion (Ma inge e al. 1989, Cobb 1992, aizawa and b own 1999). i has been e alua ed in g eenhouse and ield s udies o con ol o hyd illa (Hy- d illa e icilla a [l. .] oyle) and o he in asi e aqua ic spe- cies (Mudge 2007, icha dson e al. 2008, Mudge e al. 2010). he high cos s associa ed wi h egis e ing an he bicide o a new ma ke (i.e., aqua ics) may be o e come by maxi- mizing he ma ke po en ial; he e o e, one objec i e o his esea ch was o de e mine i lumioxazin has u ili y as a olia o a subsu ace ea men o con ol loa ing aqua ic weeds. Eme gen non a ge aqua ic plan s could be impac ed by lumioxazin applica ions, so he second ob- jec i e was o quan i y he e ec s o olia and subsu ace lumioxazin ea men s on common non a ge eme gen aqua ic plan s. MA e IAls And Me hods Floa ing aqua ic plan s. Wa e hyacin h and wa e le uce. Plan s we e collec ed om odman ese oi nea in e - lachen, Flo ida, and es ablished in 95 l high-densi y polye h- ylene (HdPE) anks illed wi h 80 l o ap wa e (pH 8.0) in ap il 2006 a he uni e si y o Flo ida (Cen e o aqua ic and in asi e Plan s) in Gaines ille, Flo ida. ap wa e was supplemen ed wi h 1 ml o Chela ed i on Plus1 (12-0-0) and 150 mg l−1 Mi acle-G o®2 (24-8-16) e ilize p io o he bi- cide ea men . nu ien s we e added again a 1 and 3 weeks a e ea men . Wa e hyacin h (5 plan s pe ank) and wa e le uce (20 plan s pe ank) we e allowed o acclima e o 3 weeks be o e ea men . his s udy was epea ed in augus 2006 on he main campus o he uni e si y o Flo ida wi h wa e om bi en’s a m lake (pH 7.5). bo h s udies we e comple ely andomized designs wi h 4 eplica ions ( anks) o each ea men . all s udies we e conduc ed unde ull sunligh . Fo he olia ea men s, lumioxazin3 was applied o he oliage wi h a o ced ai Co2-powe ed sp aye calib a ed o deli e a sp ay olume o 935 l ha−1 h ough a single ee- je ®4 80-0067 nozzle a 0, 36, 72, 143, 286, 572, and 1144 g a.i. ha−1 plus a non-ionic su ac an 5 (0.25% / ). subsu ace lumioxazin ea men s we e conduc ed concu en ly a each loca ion. Flumioxazin was applied a 0, 100, 200, 400, 800, and 1600 µg a.i. l−1 as s a ic ea men s. all li e wa e hyacin h and wa e le uce issue was ha - es ed 34 d a e ea men (da ), placed in a d ying o en a 90 C o abou 1 week, and weighed. Plan d y weigh da a we e analyzed using nonlinea eg ession (exponen- ial decay, y = b0e−bx) wi h he P oC nlin p ocedu e (sas ins i u e 2002), and eg ession models we e used o de e - mine he e ec i e concen a ion 50 (EC50), which is he concen a ion o lumioxazin equi ed o cause a 50% e- duc ion in d y weigh compa ed o con ol plan s. because he e we e no di e ences be ween he slopes o he eg es- sion lines a he 95% con idence le el, da a we e pooled o each epea ed s udy. Landol ia. a popula ion o landol ia (Landol ia punc a a [G. Mey] d.H. les and d.j. C aw o d) was collec ed om a pond wi h no his o y o he bicide ea men s in alachua Coun y, Flo ida, and cul u ed a he Cen e o aqua ic and in asi e Plan s in 266 l ibe glass anks in a g eenhouse (ligh in en- si y o 1200 µmol m−2 s−1). Plan s we e cul u ed in ap wa e (pH 8.2) amended wi h Mi acle-G o (24-8-16, 150 mg l−1) and allowed o acclima e o 2 weeks be o e ea men . a 10 g aliquo ( esh weigh ; 1.3 ± 0.07 g d y weigh ) o landol ia was placed in 3 l HdPE (17.1 cm diame e by 13.3 cm deep) po s illed wi h ap wa e (pH 8.0) and Mi acle-G o. Plan s we e allowed o acclima e in he po s o an addi ional 2 d p io o he bicide ea men . all po s we e amended wi h Mi acle- G o a 2 and 14 da . he subsu ace expe imen was conduc ed in ap il and May 2007. landol ia was ea ed wi h lumioxazin a 0, 10, 25, 50, 100, 200, 400, 800, and 1600 µg a.i. l−1 as s a ic ea - men s. as a compa ison ea men , diqua 6 was applied as a olia ea men a 1.1 kg a.i. ha−1 using he desc ibed me h- ods o olia lumioxazin ea men s. his expe imen was a andomized design wi h i e eplica es. Folia lumioxazin ials we e conduc ed in oc obe 2005, ap il 2007, and May 2007. Flumioxazin was applied o landol ia a 0, 36, 72, 143, 286, 572, and 1144 g a.i. ha−1 plus a non-ionic su ac an (sun- s eam; 0.25% / ) using he same me hods as desc ibed in he wa e le uce and wa e hyacin h s udies. due o he di icul y o emo ing la ge quan i ies o nec o - ic o chlo o ic and dead landol ia plan s, isual es ima es o con ol (% con ol) we e de e mined on a scale o 0 o 100%, whe e 0 = no chlo osis o nec osis and 100 = plan dea h. Pe cen con ol a ings we e based on non ea ed con ol plan s. he e we e no di e ences in con ol be ween he wo expe imen s (Fishe ’s P o ec ed lsd, p ≤ 0.05); he e o e, he da a om he wo expe imen s we e pooled o analysis and means we e sepa a ed using 95% con idence in e als. Eme gen aqua ic plan s. he sensi i i y o he non a ge eme gen aqua ic plan s eleocha is, maidencane, picke el- weed, and sagi a ia we e simila ly e alua ed agains subsu - ace and olia lumioxazin applica ion echniques. all plan s we e pu chased om a local plan nu se y in augus 2006 and ap il 2007 o he subsu ace and olia s udies, espec- i ely. wo heal hy s ems (30 o 38 cm) o each species we e plan ed in a mix u e o 2:1 po ing media7 o mason y sand in 3 l HdPE po s amended wi h osmoco e®8 (15-9-12) e il- ize a a a e o 1g kg−1 soil. he subsu ace lumioxazin expe imen was a andomized design wi h i e eplica es ( anks). Each species was cul u ed ou doo s unde shade clo h (70% sunligh ) o 4 weeks in 95 l HdPE anks. Wa e le el in he anks was main ained a 25 cm, and pH emained a o nea 7.5 h oughou he s udy. Plan s we e cul u ed o 1 mon h when lumioxazin was ap- plied a 0, 50, 100, 200, 400, 800, and 1600 µg a.i. l−1 as s a ic J. Aqua . Plan Manage. 50: 2012. 113 ea men s. in he olia lumioxazin ial, all i e eme gen eplica es (po s) we e placed in one 266 l ibe glass ank (72 by 82 by 45 cm) p io o ea men . Flumioxazin was applied as a olia ea men a 0, 36, 72, 143, 286, 572, and 1144 g a.i. ha−1 wi h a non-ionic su ac an (suns eam; 0.25% / ) us- ing he same me hods as he loa ing plan s. a 40 da , all li e issue om he olia and subsu ace i- als was ha es ed a he soil line, placed in a d ying o en a 90 C o abou 1 week, and weighed. Plan d y weigh da a was analyzed using no-linea eg ession (P oC nlin, sas ins i- u e 2002), and EC50 alues we e de e mined o d y weigh . da a we e pooled ac oss expe imen al uns when no s a is i- cal di e ences be ween he slopes o eg ession lines we e obse ed. esul s And dIscussIon Floa ing aqua ic plan s. Wa e hyacin h and wa e le uce. Wa- e le uce was much mo e sensi i e o olia applica ions o lumioxazin han wa e hyacin h, wi h EC50 alues o 69 and 1435 g a.i. ha−1, espec i ely (Figu e 1). all olia a es ≥286 g a.i. ha−1 esul ed in comple e con ol o wa e le uce. ea - ed wa e le uce plan s exhibi ed chlo osis and nec osis on he lea es 3 o 5 da and de olia ion 12 o 15 da . Folia lumioxazin a es ≥286 g a.i. ha−1 esul ed in comple e plan decay 21 da , whe eas suble hal a es (36 o 143 g a.i. ha−1) esul ed in eg ow h o young plan s o wa e le uce ( ame s) om he cen al me is ema ic egion. P e ious esea ch ( icha dson e al. 2008) demons a ed lumioxazin p o ided 97% con ol o wa e le uce plan s (9 cm diame e ) wi h 34 g a.i. ha−1 and 100% wi h highe a es. ou esea ch e alua ed lumioxazin on la ge and mo e ma u e plan s (15+ cm diam- e e ), which likely explains he lowe le el o lumioxazin sen- si i i y in ou esea ch compa ed o ha o icha dson e al. (2008). Wa e hyacin h biomass was educed by only 41% o he non ea ed con ol a he highes olia lumioxazin a e e alua ed (1144 g a.i. ha−1) 34 da . he p ojec ed EC50 was 1435 g a.i. ha−1 (Figu e 1), abou h ee imes he maximum label a e. ea ed wa e hyacin h plan s exhibi ed blackening on younge lea es only, which is simila o inju y symp oms no ed on wa e le uce and wa e hyacin h ea ed wi h he PPo inhibi o ca en azone-e hyl (Koschnick e al. 2004). subsu ace lumioxazin applica ions p o ided 100% wa e le uce con ol a concen a ions ≥100 µg a.i. l−1 (da a no shown). in con as , lumioxazin applied o he wa e column ailed o educe wa e hyacin h biomass by mo e han 30% o he non ea ed con ol plan s a any a e e alua ed (da a no shown) and con i ms ha wa e hyacin h is mo e ole an o lumioxazin han wa e le uce. hese esul s a e simila o hose epo ed o wa e hyacin h and wa e le uce ea ed wi h he PPo inhibi o ca en azone-e hyl (Koschnick e al. 2004). Landol ia. he e ec s o a subsu ace applica ion o lu- mioxazin o landol ia (Figu e 2) show ha mos lumioxazin ea men s caused olia bleaching wi hin 7 o 10 da , bu none o he ea men s esul ed in comple e con ol o land- ol ia. Each lumioxazin ea men was di e en as indica ed by he 95% con idence in e als. landol ia colonies ea ed a concen a ions >25 µg a.i. l−1 began o sepa a e, and oo s became de ached om indi idual onds. Koschnick (2005) epo ed landol ia ea ed in he da k wi h diqua unde wen oo de achmen wi hou chlo osis. he p ima y unc ion o oo s o plan s in he lemnaceae amily is s abiliza ion o onds (landol 1986). diqua applied as a compa ison ea - men esul ed in 100% con ol less han 5 da when he he bicide was olia applied a 1.1 kg a.i. ha−1. duckweed is ex emely sensi i e o diqua and has a ypical EC50 o 4 µg a.i. l−1 (Pe e son e al. 1997), he cu en indus y s anda d o duckweed con ol. he olia applied lumioxazin landol ia s udy was con- duc ed h ee imes; ea ed plan s we e isually simila o con ol plan s a all a es up o 1144 g a.i. ha−1 and showed no dose esponse, and he e o e we e no ha es ed (da a no shown). he olia ea men s o landol ia and wa e hya- Figu e 1. he e ec o a olia lumioxazin applica ion on he d y weigh o wa e hyacin h and wa e le uce 34 d a e ea men . da a a e shown as d y weigh means ± s anda d e o (n = 8). EC50 = e ec i e concen a ion 50, concen a ion o lumioxazin (g a.i. ha−1) equi ed o educe wa e hyacin h and wa e le uce biomass by 50%. Figu e 2. Pe cen con ol ( isual) o landol ia 21 d a e a olia diqua (kg a.i. ha−1) and subsu ace lumioxazin applica ion (µg a.i. l−1 a.i.). Pe cen con ol ±95% con idence in e al (n = 10). o e lapping con idence in e al ba s indica e no signi ican di e ence. 114 J. Aqua . Plan Manage. 50: 2012. cin h we e unsuccess ul, and olia a es ≥286 g a.i. ha-1 we e needed o con ol wa e le uce. hese esul s sugges ha lumioxazin up ake is limi ed by he lea cu icle o occu s p i- ma ily h ough oo up ake o abso p ion by he unde side o he plan . Fu he esea ch is needed o de e mine i lumioxazin applied as a subsu ace ea men is as e icacious o wa e le uce in highe pH wa e (9.0). Mudge e al. (2010) dem- ons a ed lumioxazin in neu al pH wa e is mo e inju ious o subme sed aqua ic plan s han when applied o high pH (9.0) wa e . Eme gen aqua ic plan s. Eme gen aqua ic plan s had highly a iable sensi i i y o lumioxazin aqueous concen a- ions up o 1600 µg a.i. l−1 (Figu e 3). sagi a ia d y weigh was educed 100% a concen a ions ≥800 µg a.i. l−1 com- pa ed o a 73 o 83% d y weigh educ ion in eleocha is, mai- dencane, and picke elweed. sagi a ia was he mos sensi i e species o a subsu ace lumioxazin ea men ollowed by maidencane, eleocha is, and picke elweed based on calcula - ed EC50 alues o d y weigh ( able 1). hese da a indica e eleocha is, picke elweed, and maidencane would be inju ed by he maximum lumioxazin concen a ion o 400 µg a.i. l−1; howe e , eleocha is and picke elweed would likely eco e om he ea men . Visual inju y symp oms obse ed 2 weeks a e he subsu - ace lumioxazin applica ion o eme gen plan s included in- e einal chlo osis (sagi a ia and picke elweed), eddening on lea ma gins (maidencane), and mino chlo osis (eleocha- is). Flumioxazin and o he PPo-inhibi ing he bicides a e ab- so bed p ima ily by plan oo s wi h some abso bance in he shoo s when applied o he soil, bu ansloca ion is limi ed once he bicides a e abso bed in o olia issue because o he apid desicca ion (Fadayomi and Wa en 1977, i e and Co- ble 1981, unland e al. 1999, senseman 2007). Po s wi hou holes we e used in hese s udies, and ew oo s we e isible abo e he soil line. he e o e, lumioxazin up ake occu ed ei he h ough he unde wa e s em, subme sed lea es, o oo s. P e ious esea ch (Fadayomi and Wa en 1977, i - e and Coble 1981) ound li le ansloca ion o PPo-inhib- i ing he bicides in plan s, bu he subsu ace ea men o eme gen aqua ic plan s in his s udy sugges ed mo emen o lumioxazin om he soil o lowe s em in o he lea es. i ansloca ion o lumioxazin was limi ed, his he bicide should ha e gi dled he plan a he soil line and p oduced inju y symp oms such as nec osis o he s em and lea es wi h- ou einal chlo osis i s appea ing in he lea es. Fe ell e al. (2007) showed lumioxazin in combina ion wi h MsMa (monosodium sal o Maa) esul ed in a 94% yield educ ion when applied as a high pos -di ec ea men o 20 cm all co on. symp omology o lumioxazin- ea ed co on includ- ed nec o ic lesions on lea es, eddening s ems, s em gi dling, and e en ual lodging. P e ious esea ch also ound ha as co on ma u es, plan s become mo e ole an o lumioxazin because o g ea e ba k de elopmen and me abolic capaci y (Fe ell and Vencill 2003). Folia lumioxazin ea men s we e much less inju ious o eme gen aqua ic plan s han subsu ace ea men s (Figu e 4). Maidencane and sagi a ia would equi e olia applica- ion a es >1884 and 1320 g a.i. ha−1, espec i ely, o educe d y weigh by 50% based on he calcula ed EC50 alues ( able 1). an EC50 alue could no be calcula ed o d y weigh o bo h eleocha is and picke elweed because inc eased lu- mioxazin concen a ions esul ed in an inc ease in d y weigh (posi i e eg ession slope). Pos eme gen applica ions o lu- mioxazin a e gene ally ecommended o ac i ely g owing weeds <5 cm in heigh (Valen usa Co po a ion 2009), so he minimal olia inju y and subs an ial lack o educ ion in biomass obse ed in his olia s udy we e p obably due o he ad anced ma u i y o hese plan s. inju y symp oms (includ- ing chlo o ic and nec o ic lesions on he lea es) we e simi- la o hose desc ibed o o he PPo-inhibi ing he bicides (Pe e son e al. 2001). ole an species ha e educed o no symp oms, whe eas he lea es o suscep ible species apidly desicca e and die (Pe e son e al. 2001). he limi ed inju y symp oms exhibi ed by plan s in he olia expe imen we e simila o plan s exposed o subsu ace ea men s. selec i e con ol o in asi e weed species is he goal o aqua ic weed manage s. He bicide applica o s a ge in asi e plan s h ough he use o speci ically o mula ed he bicides, seasonally imed he bicide applica ions, and/o p eemp i e spo ea men s be o e weeds become a p oblem (uni e - si y o Flo ida 2011). he na i e eme gen plan s es ed in his s udy we e ole an o olia lumioxazin applica ions, e idenced by no obse ed mo ali y. in con as , subsu ace applica ions esul ed in mo e inju y o non a ge plan s, es- pecially when ea men s we e made in low pH wa e . Flu- mioxazin is apidly deg aded by hyd olysis, wi h an a e age hal -li e o 4.1 d, 16.1 h, and 17.5 min a pH 5.0, 7.0, and 9.0, espec i ely (Ka agi 2003, senseman 2007). Mudge e al. (2010) demons a ed ha wa e pH does no di ec ly in lu- ence lumioxazin ac i i y, bu h ough an impac on aque- ous lumioxazin deg ada ion a es, pH o he ea ed wa e can ha e a p o ound impac on e icacy. Mesocosm and ield ials ha e demons a ed di e ences in lumioxazin e icacy and selec i i y when applied o wa e wi h a pH >8.0 (Mudge 2007, Mudge and Halle 2010). Figu e 3. he e ec o lumioxazin concen a ion on he d y weigh o he non a ge eme gen aqua ic plan s eleocha is (), maidencane (▫), pick- e elweed (), and sagi a ia () 40 d a e ea men . da a a e shown as ac ual d y weigh means ± s anda d e o (n = 10). J. Aqua . Plan Manage. 50: 2012. 121 he s udy; howe e , he low dose ollowed by he high dose ea men esul ed in an addi ional 50% dec ease in bio- mass compa ed o he a o emen ioned ea men (Figu e 2). hese esul s indica e addi ional penoxsulam may be applied a highe concen a ions a ew weeks a e ini ial ea men o inc ease con ol. he h eshold o ini ial and seconda y ea men s will need o be u he esea ched o de e mine he e ec i eness o high dose ollow up ea men s. bo h lu idone ea men s we e applied a 20 µg l−1 ol- lowed by 5 µg l−1 a 4 o 8 Wa ( able 4). al hough ini ial and ollow up ea men s we e he same concen a ion, he addi ional 4 wk exposu e a he highe concen a ion esul - ed in an addi ional 87% con ol. hese da a indica e he ex- a 4 weeks o lu idone exposu e a he highe concen a ion a e necessa y o con ol his weed, compa ed o he empo- a y g ow h egula ion obse ed wi h he low dose ollow up ea men a 4 Wa . Penoxsulam concen a ions we e 4 and 21.5 µg l−1 o he penoxsulam 5 and 20 µg l−1 s a ic ea men s, espec i ely, 1 da ( able 5). He bicide concen a ions emained ela i ely s able h oughou he cou se o he s udy o he 5 µg l−1 s a ic ea men , whe eas he 20 µg l−1 s a ic concen a ions declined a a much as e a e. he sho e hal -li e o he 20 µg l−1 ea men could be a ibu ed o g ea e e icacy o he highe dose as plan s we e con olled and desicca ed a a much as e a e, inc easing uV ligh pene a ion in o he wa e column and aiding he bicide deg ada ion. Flu i- done concen a ions dec eased o <1 µg l−1 by 8 Wa o he F20Ex4Fb5 ea men ; he e o e, expe imen al uni s in his ea men ecei ed an addi ional 3 µg l−1 o lu idone 9 Wa o supplemen he loss o he bicide (da a no shown). he lu idone e- ea men concen a ion was chosen based on he hal -li e o lu idone in he CE expe imen . signi i- can ain all occu ed in Vicksbu g h oughou he mon h o july, which may ha e con ibu ed o he apid dilu ion o he he bicide. Howe e , du ing his ime he P5Ex16 ea men concen a ion (2.8 ± 0.27) was less han he F20Ex4Fb5 con- cen a ion 4 Wa , and by 8 Wa , penoxsulam emained s a- ble while lu idone dec eased o <1 µg l−1. he gian sal inia ma emained in ac o he F20Ex4Fb5 ea men om 4 o 8 Wa ; hus, inc eased pho oly ic deg ada ion was unlikely o be he cause o apid lu idone loss. esul s om his expe imen indica e gian sal inia con- ol can be achie ed by implemen ing mul iple applica ions o main aining penoxsulam o lu idone concen a ions o an ex ended pe iod o ime (>12 wk). low dose epea ap- plica ions a e commonly used o manage hyd illa and Eu - asian wa e mil oil (My iophyllum spica um l.) wi h lu idone o penoxsulam (Ge singe e al. 2001, Koschnick e al. 2003). low dose s a ic penoxsulam ea men s (P5Ex16) can esul in 76% con ol and comple ely supp ess g ow h du ing he exposu e pe iod. inc eased con ol can be a ained by ex- posing plan s o highe penoxsulam concen a ions (10 o 20 µg l−1) o longe pe iods o ime (16 wk). low concen- a ions o slow-ac ing he bicides such as penoxsulam and lu idone may empo a ily g ow h egula e o s un gian sal inia o se e al weeks, bu plan s will ul ima ely eco e once concen a ions all below his h eshold. He bicides and plan g ow h egula o s ha e been p oposed and in es iga ed o achie e a balance o con olling in asi e aqua ic plan s while p e en ing nega i e ecological e ec s om unchecked g ow h o hese species (lembi and Chand 1992, ne he land and lembi 1992, nelson 1996, 1997, 2012 o hcoming). G ow h egula ing concen a ions o slow-ac ing he bicides may also be bene icial o aqua ic plan managemen , includ- ing gian sal inia. his o m o managemen may aid in p e- en ing de elopmen o dense in es a ions and hei nega i e e ec s, o by slowing he eco e y o a ge in asi e plan s om o he equi ed o ms o managemen . his could in- clude olia he bicide applica ions o s ess om biocon ol agen s, such as he gian sal inia wee il (Cy obagous sal ini- ae), in an in eg a ed pes managemen p og am (Mudge and Ha ms 2012). ecen wo k has shown posi i e esponse o in eg a ing penoxsulam ea men s and mul iple biocon ol agen s on wa e hyacin h (Mo an 2012). Subsu ace s. olia expe imen . a he conclusion o he s udy (11 Wa ), all subsu ace and olia he bicide ea - men s educed gian sal inia d y weigh 27 o 67% o he non ea ed con ol (Figu e 3). in pa icula , penoxsulam o- Table 4. he bicide concenT aTions measu ed om gianT salVinia T eaTed wiTh subsu ace aPPlicaTions o Penoxsulam and lu idone aT 20 µ g l−1 in The ceT exPe imenT. He bicide sampling Pe iod Concen a ion (µg a.i. l−1 ± s.E.) Penoxsulam 1 da a26.0 ± 0.08 1 Wa 24.6 ± 0.11 2 Wa 20.0 ± 3.37 4 Wa 20.3 ± 0.74 8 Wa 13.7 ± 0.46 Flu idone 1 da 10.8 ± 0.23 1 Wa 17.0 ± 0.27 2 Wa 15.6 ± 0.20 4 Wa 12.4 ± 0.68 Table 5. he bicide concenT aTions measu ed in T eaTed waTe ollowing sub- su ace aPPlicaTions o Penoxsulam To gianT salVinia in The single sTaTic Vs. mulTiPle aPPlicaTion exPe imenT. He bicide ea men asampling Pe iod Concen a ion (µg a.i. l−1 ± s.E.) Penoxsulam 5 µg a.i. l−1 1 da b4.0 ± 0.17 1 Wa 4.4 ± 0.16 2 Wa 3.3 ± 0.03 4 Wa 2.8 ± 0.27 8 Wa 3.7 ± 0.11 10 Wa 3.4 ± 0.25 12 Wa 2.7 ± 0.25 16 Wa 1.8 ± 0.11 Penoxsulam 20 µg a.i. l−1 1 da 21.5 ± 1.64 1 Wa 21.2 ± 1.69 2 Wa 18.3 ± 0.90 4 Wa 17.4 ± 0.73 8 Wa 11.8 ± 0.29 10 Wa 9.1 ± 0.79 12 Wa 7.3 ± 0.71 16 Wa 1.9 ± 1.85 aPenoxsulam applied as a one ime ea men and plan s exposed o 16 wk; n = 4. babb e ia ions: da , days a e ea men ; Wa , weeks a e ea men . 122 J. Aqua . Plan Manage. 50: 2012. lia (24 h) plus lu idone subsu ace, penoxsulam olia (24 h), and penoxsulam olia (s a ic) educed mean plan d y weigh o below p e ea men le el. he penoxsulam olia (24 h) plus lu idone subsu ace ea men p o ided be - e con ol han all penoxsulam o lu idone s and alone o combina ion subsu ace ea men s. al hough he glyphosa e plus diqua mix was ini ially highly e icacious, plan s began o eco e wi hin 3 Wa and displayed no inju y symp oms by 11 Wa . P e ious esea ch demons a ed diqua a a much highe olia a e (1.12 kg ha−1) plus a me hyla ed seed oil and o ganosilicone su ac an blend p o ided 100% con ol o a single laye o gian sal inia 6 Wa (nelson e al. 2001). he amoun o plan ma e ial and densi y o he ma in he subsu ace e sus olia expe imen was much g ea e (i.e., hicke ) a he incep ion o he expe imen compa ed o he single laye o gian sal inia ea ed in p e ious esea ch by nelson e al. (2001). he addi ional laye s o plan ma e ial in his s udy likely p e en ed some o he he bicide sp ay so- lu ion om eaching he plan ma e ial below he wa e su - ace. Flu idone concen a ions ailed o each he a ge dose o 20 µg l−1 and ne e exceeded 6.1 µg l−1 h oughou he cou se o he expe imen ( able 6). he eason o he low concen a ion, despi e he “bump” a 5 Wa is unknown. Con e sely, penoxsulam concen a ions emained abo e 30 µg l−1 o he i s week o he s udy; howe e , concen a ions dec eased o 22.8 µg l−1 a 2 Wa and emained ela i ely s able h oughou he emainde o he s udy ( able 6). he penoxsulam 59.57 g ha−1 olia a e (24 h and s a ic) was equi alen in amoun o ac i e ing edien o a 20 µg l−1 sub- su ace penoxsulam ea men . Pa ial mig a ion o he bicide in o unde lying wa e was a planned e ec o he s a ic olia ea men . al hough he heo e ical in-wa e concen a ion o 20 µg l−1 was ne e achie ed by his s a ic olia ea men , some o he he bicide solu ion was abso bed by he oliage, and he emainde eached he wa e column and was a ail- able o up ake by he subme sed oliage. he penoxsulam s a ic olia ea men was 12.0 µg l−1 a 1 Wa and dec eased o 7.8 µg l−1 by 11 Wa ( able 4). Gian sal inia ea ed wi h subsu ace o olia s a ic penoxsulam ea men s began o exhibi simila inju y symp- oms as ea ly as 2 Wa . Plan s ea ed wi h penoxsulam a 20 µg l−1 and 59.57 g ha−1 (s a ic) exhibi ed g ow h egula ion, and olde issue became nec o ic h ough 6 Wa . he penox- sulam olia (24 h) applica ion esul ed in wi ches b oom symp oms on all new issue in addi ion o nec osis o olde issue 2 Wa . Flu idone- ea ed plan s exhibi ed chlo osis by 1 Wa ; howe e , minimal bleaching o he oliage emained by 4 Wa , and plan s we e symp om ee by 6 Wa . he apid dec ease in inju y symp oms was p obably due o he low lu- idone concen a ions in he wa e . al hough he lu idone ea men was a ge ed a 20 µg l−1, he concen a ion was 5.9 ± 0.62 o 3.2 ± 0.20 be ween 1 da and 4 Wa , espec i ely ( able 6). he dec ease in inju y symp oms and concen a- ions p omp ed a bump ea men 5 Wa o inc ease he dose o 20 µg l−1 in all expe imen al uni s con aining lu i- Figu e 3. E ec o subsu ace and olia penoxsulam (P), lu idone (F), glyphosa e (G), and diqua (d) applica ions on ma u e gian sal inia mean d y weigh (± s.E.) 11 weeks a e ea men (Wa ). Plan s exposed o s a ic ea men s emained o he du a ion o he expe imen , while 24 h indi- ca es plan s we e emo ed om ea men and placed in esh wa e . Ho i- zon al line ep esen s p e ea men biomass o gian sal inia. Means wi h he same le e a e no signi ican acco ding o Fishe ’s p o ec ed lsd es a p = 0.05; n = 4. Table 6. he bicide concenT aTions measu ed ollowing sTaTic subsu ace o olia aPPlicaTions o Penoxsulam and lu idone To maTu e gianT salVinia in The subsu ace Vs. olia exPe imenT. He bicide ea men sampling Pe iod Concen a ion (µg a.i. l−1 ± s.E.) Flu idonea (20 µg a.i. l−1) 1 da b5.9 ± 0.62 1 Wa 5.2 ± 0.28 2 Wa 4.6 ± 0.24 4 Wa 3.2 ± 0.20 8 Wa 6.1 ± 0.53 11 Wa 4.6 ± 0.50 Penoxsulam (20 a.i. l−1) 1 da 30.3 ± 1.81 1 Wa 30.9 ± 3.55 2 Wa 22.8 ± 1.76 4 Wa 19.4 ± 4.79 8 Wa 16.2 ± 1.39 11 Wa 14.1 ± 1.32 Penoxsulam (59.57 g a.i. ha−1) 1 da 7.3 ± 0.36 1 Wa 12.0 ± 1.14 2 Wa 13.2 ± 0.78 4 Wa 14.8 ± 1.63 8 Wa 10.6 ± 0.86 11 Wa 7.8 ± 1.26 aFlu idone applied on day o ea men and eapplied 5 Wa o inc ease concen a ion o 20 µg a.i. l−1. babb e ia ions: da , days a e ea men ; Wa , weeks a e ea men ; n = 4. J. Aqua . Plan Manage. 50: 2012. 123 done. he lu idone bump esul ed in an inc ease in bleach- ing symp oms h ough he emainde o he s udy. he subsu ace penoxsulam plus subsu ace lu idone ea men esul ed in a a ie y o inju y symp oms h ough- ou he cou se o he expe imen . Plan inju y symp oms in- cluded nec osis and g ow h egula ion (1 o 2 Wa ) along wi h minimal chlo osis and wi ches b oom. he combina ion o glyphosa e plus diqua esul ed in as e and mo e in ense inju y symp oms han any o he he bicide ea men in his ial. Plan s ea ed wi h his he bicide combina ion exhib- i ed nec osis <1 Wa . he apid ac i i y o his combina ion was no su p ising because diqua inju es gian sal inia as ea - ly as 1 da (nelson e al. 2001). al hough his combina ion seemed o be highly e icacious a quickly desicca ing olde issue, new plan g ow h was obse ed as ea ly as 3 Wa . he single s a ic e sus mul iple applica ion s udy dem- ons a ed penoxsulam a 20 µg l−1 educed gian sal inia biomass 100% when plan s we e exposed o 16 wk, whe eas plan s in his s udy we e con inuing o die and lose buoyancy a 11 Wa . an addi ional 3 o 5 wks o exposu e should ha e esul ed in nea comple e o comple e con ol based on he esponse o gian sal inia o he penoxsulam in he single s a - ic e sus mul iple applica ions s udy. his no ion is suppo ed by p e ious esea ch, which indica ed ha als- and Pds-in- hibi ing he bicides penoxsulam and lu idone, espec i ely, a e ela i ely slow ac ing and equi e long exposu es (60+ d) o e ec i ely con ol a ge species (ne he land and Ge sing- e 1995, Koschnick e al. 2007b). he in en was o conclude he expe imen 16 Wa , bu i was sho ened because con ol plan s began o decline in heal h a e empe a u es we e un- usually coole han no mal in sep embe 2010. al hough lu idone- ea ed plan s we e minimally con- olled in his s udy (Fig. 3), he CE and single s a ic e sus mul iple applica ion s udies demons a ed he e ec i eness o his p oduc (Fig. 1 and 2). Flu idone was highly e icacious (99% con ol) when plan s we e exposed o 20 µg l−1 o a leas 8 wk (Fig. 2). he ocus o he hi d yea o esea ch was o ex end he exposu e ime beyond 8 wk o achie e 100% con ol, bu lu idone concen a ions ailed o each o be main ained a he a ge concen a ion ( able 6). he ank mix o glyphosa e plus diqua plus wo su ac- an s (nonionic and bu e ing agen + nonionic o gano-sili- cone) is cu en ly one o he ecommended olia ea men s o gian sal inia in louisiana (d. E. sande s and a. j. Pe e , 2012, pe s. comm.). one o wo plan laye s o gian sal inia a e con olled wi h his mix u e; howe e , mul iple le els o plan ma e ial a e di icul o pene a e wi h a single appli- ca ion o any olia applied he bicide o he bicide combina- ion; he e o e, mul iple applica ions a e o en necessa y o e ec i ely con ol o e adica e dense gian sal inia in es a- ion (nelson e al. 2007). bo h olia penoxsulam ea men s (s a ic and 24 h exposu e) p o ided simila con ol o he glyphosa e plus diqua ank mix e alua ed in his s udy. he penoxsulam 59.57 g ha−1 olia a e was equi alen o a 20 µg l−1 subsu ace ea men i all he he bicide sp ay eached he wa e column and ailed o come in con ac wi h he plan canopy. in compa ison, he 24 h olia penoxsulam ea men was designed o limi any po en ial he bicide up ake om he wa e column. al hough he d y weigh da a e lec ed no di e ences, many new heal hy lea es we e de eloping om plan s exposed o 24 h, whe eas only a ew heal hy onds we e wi nessed wi h he s a ic olia penoxsulam ea men . because penoxsulam was s ill p esen 11Wa (7.8 ± 1.26 µg l−1), an addi ional ew weeks o he bicide exposu e may ha e sepa a ed hese ea men s, allowing olde plan issue in he s a ic penoxsulam olia ea men o desicca e and allow mo e new plan g ow h in he 24 h penoxsulam olia and glyphosa e plus diqua ea men s. in addi ion, penoxsulam is ecommended a 35.04 o 98.12 g ha−1 as a olia applica- ion, which is equi alen o 2.0 o 5.6 oz p oduc a-1. Fu u e esea ch should be conduc ed o de e mine i a highe olia a e can p o ide g ea e e icacy as well as as e ac i i y. P e ious esea ch has shown ha penoxsulam is an e ec- i e he bicide when applied subsu ace o con ol hyd illa and a iable-lea wa e mil oil (My iophyllum he e ophyllum Mi- chx.; Koschnick e al. 2007a, Glomski and ne he land 2008). ou da a indica e penoxsulam as a olia o subsu ace ap- plica ion can be a iable al e na i e o he s anda d ank mix o glyphosa e plus diqua plus wo su ac an s o con olling a ious sized in es a ions o gian sal inia. Penoxsulam may ha e he po en ial o p o ide imp o ed, longe - e m con ol o e p e ious s anda d olia ea men s unde ce ain use scena ios, pa icula ly o la ge, dense in es a ions wi h high eco e y po en ial. subsu ace applica ions should be main- ained o a minimum o 8 wks o p o ide accep able con ol, bu 12+ wk o exposu e gene ally p o ided excellen con ol. Penoxsulam applied a 5 o 20 µg l−1 unde ex ended expo- su es, can p o ide g ow h egula ion o con ol o gian sal- inia. along wi h le hal con ol ou comes, he abili y o use low-dose penoxsulam o g ow h egula ion is an addi ional use cha ac e is ic ha may complemen o he con ol ech- niques such as biological con ol o olia applica ions whe e o he wise e-g ow h po en ial would p eclude e ec i e man- agemen . depending on po en ial o dilu ion o o he o ms o dissipa ion, mul iple applica ions o bump ea men s may be necessa y o main ain e ec i e concen a ions o penox- sulam in he wa e column. a olia o subsu ace penox- sulam ea men may be a bene icial ea men depending on he locale o plan s (open wa e s. backwa e ), p esence o non a ge plan species, o he numbe o laye s/ hickness o he gian sal inia ma . he penoxsulam and lu idone da a gene a ed in hese h ee expe imen s need o be u he in- es iga ed on an ope a ional le el in ield si es in es ed wi h gian sal inia. sou ces o MA e IAls 1Mi acle-G o® 36-6-6, he sco ’s Company, Ma ys ille, ohio 2aquashade®, applied biochemis s, Ge man own, Wisconsin 3Galleon sC®, seP o Co po a ion, Ca mel, indiana 4sona as®, seP o Co po a ion, Ca mel, indiana 5aquaP o®, seP o Co po a ion, Ca mel, indiana 6 ewa d® landscape and aqua ic He bicide, syngen a P o essional P od- uc s, G eensbo o, nC 7aqua-King Plus®, Win ield solu ions, llC, s . Paul, Minneso a 8 ho oughb ed®, Win ield solu ions, llC, s . Paul, Minneso a 9 eeje echnologies, Whea on, il AcknowledgMen s his esea ch was suppo ed by seP o Co po a ion/ aqua ic Ecosys em es o a ion Founda ion and he us a my aqua ic Plan Con ol esea ch P og am. app ecia ion is 124 J. Aqua . Plan Manage. 50: 2012. ex ended o l. nelson, C. G odowi z, j. namanny, M. ob- e son, j. smi h, K. de osse e, M. s e nbe g, and a. Poo ey o echnical assis ance h oughou he esea ch. d. sand- e s (lsu agCen e ) and a. Pe e (louisiana depa men o Wildli e and Fishe ies) kindly p o ided ecommenda ions on gian sal inia con ol in louisiana. M. ne he land and l. Glomski kindly p o ided e iews o his manusc ip . Pe mis- sion was g an ed by he Chie o Enginee s o publish his in o ma ion. Ci a ion o ade names does no cons i u e en- do semen o app o al o he use o such comme cial p od- uc s. lI e A u e cI ed ande son WP. 1996. Weed science: P inciples and applica ions, 3 d ed. Wes Publishing Company, s . 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