Impact of Injury from Late Season Sequential Glufosinate Applications on Sugarbeet Yield

Transcription

1 Octber - December 2004 Impact f Injury 119 Impact f Injury frm Late Seasn Sequential Glufsinate Applicatins n Sugarbeet Yield Ines Rthe, Alan G. Dexter, and Jhn L. Luecke Nrth Dakta State University, Dept. f Plant Sciences Lftsgard Hall, Farg, ND ABSTRACT Experiments were cnducted t determine if sugarbeet (Beta vulgaris L.) injury frm sequential glufsinate treat" ments starting later than three weeks after the sugarbeet ctyledn stage caused yield lss, and t assess cumulative phyttxic effects frm sequential glufsinate treatments at varius rates. Sugarbeet plts were hand weeded until giufsinate treatments started s that sugarbeet yield lss with late seasn glufsinate treatments, if any, culd be attributed t herbicide injury rather than prlnged early seasn weed cmpetitin. Visible sugarbeet injury was greater when glufsinate treatments were started at three, fur, six, r seven weeks after the sugarbeet ctyledn stage rather than ne week after the ctyledn stage. The absence f a difference in sugarbeet rt yield and extractable sucrse, regardless f glufsinate applicatin starting time, suggests that sugarbeet either partially grew ut f the bserved leaf chlrsis r that late-appearing visible injury had n adverse effect n yield traits. Regardless f the rate, sugarbeet treated with glufsinate either ne r fur times had similar rt yield and extractable sucrse, which cnfirms the lack f any significant cumulative phyttxic effect n sugarbeet yield frm multiple glufsinate applicatins. Additinal Key Wrds: Beta vulgaris L., weed cmpetitin, leaf chlrsis. E fficient and safe weed management systems cntinue t be a key in prducing maximum sugarbeet yield. Current herbicide ptins in sugarbeet d nt guarantee weed-free prductin even under ptimum

2 120 Jurnal f Sugar Beet Research Vl 41 N 4 cnditins (Dexter and Zllinger 2003). Apprximately 53% f surveyed sugarbeet grwers in eastern Nrth Dakta and Minnesta cnsidered weeds as their mst serius prductin prblem in 2002 (Dexter and Luecke 2003). Prblems assciated with current pstemergence (POST) sugarbeet herbicide weed cntrl systems include treatment applicatin flexibility and yield-reducing, herbicide-induced sugarbeet injury. Maximum weed cntrl efficiency with the cmbinatin f cultently available POST cnventinal herbicides requires the first treatment t be applied t small weeds and t sugarbeet at the ctyledn t tw-leaf grwth stage (Dexter and Zllinger 2003; Platte et al. 1998). Very small weeds are mst susceptible t POST herbicides (Dawsn 1977; Hendrick et al. 1974). Hwever, the use f early seasn full-rate POST herbicides in sequential applicatins can injure the crp because sugarbeet seedlings have a lw tlerance t sme sugarbeet herbicides (Dexter and Zllinger 2003; Miller and Frnstrm 1988, 1989; Schweizer 1980; Wicks and Wilsn 1983). Sugarbeet plants are mst susceptible t POST herbicide applicatins starting at the ctyledn grwth stage, and less injury ccurs frm treatments at the tw- t fur; fur- t six; r six- t eight-leaf stage (Wicks and Wilsn 1983; Wilsn 1998). POST treatments f desmedipham and ethfumesate applied prir t the tw-leaf stage injured sugarbeet plants in the greenhuse (Eshel et al. 1976). Sctt et al. (1976) bserved similar field respnses with phenmedipham. Cmmercial applicatins f desmedipham and phenmedipham in sme circumstances harmed sugarbeet plants (Bray 1983; Nrris 1974; Prestn and Brisce 1983; Prdehl et al. 1992; Winter and Wiese 1978). Althugh sugarbeet plants gain herbicide tlerance as they grw larger (Dexter and Zllinger 2003; Nnis 1991), weeds als gain tlerance with size (Edmund Jr. and Yrk 1987; Lee and Oliver 1982; Ritter and Cble 1984; Weinlaeder and Dexter 1972). Desmedipham applied at the six-leaf sugarbeet grwth stage failed t satisfactrily cntrl large weeds (Eshel et al. 1976). In rder t reduce sugarbeet injury frm full-rate POST herbicides, lw-rate herbicide cmbinatins (micr-rates) were registered fr use in sugarbeet in Nrth Dakta and Minnesta in 1998 and 1999, and registered fr the entire United States in 2000 (EPA Reg. N ). The micr-rate requires three t five applicatins at five- t seven-day intervals starting when weeds are in the ctyledn stage t achieve greatest weed cntrl (Dexter and Zllinger 2003). Typically, the micr-rate cmbines desmediphan1 at 90 g hal plus triflusulfurn at 4 g ha l plus clpyralid at 30 g ha- l plus clethdim at 30 g ha l plus a

3 Octber - December 2004 Impact f Injury 121 methylated seed il adjuvant (MSO) at 1.5% vlv in the tank mix. MSO must be added t the micr-rate t enhance weed cntrl with the lw herbicide rates. The lack f glufsinate selectivity in nn-transfrmed sugarbeet has restricted glufsinate use n emerged plants. Lw use-rates, high degree f safety t nn-target rganisms, rapid degradatin in the envirnment with minimal residue persistence in sil, negligible residues in crps, unique mde f actin, applicatin flexibility, and excellent efficacy n a brad weed spectrum are the main advantages f glufsinate ver sme f the currently available sugarbeet herbicides (Ahrens 1994; Vasil 1996). Genes fr resistance t glufsinate islated frm sil bacteria have been inserted int cnventinal sugarbeet lines t allw glufsinate use in-seasn with a lw risk f crp injury (D'Halluin et al. i 992; Vasil 1996). The literature regarding sugarbeet tlerance t POST glufsinate is incnsistent. Fr example, Thrsness et al. (1998) saw n visible sugarbeet injury with glufsinate treatments applied frm emergence t the lo-leaf sngarbeet stage. Wevers (1998) agreed that timing f glufsinate treatments, even at duble rates, did nt affect crp injury nr weed cntrl efficacy. Wilsn (1999) reprted less early seasn sugarbeet injury frm gll1fsinate in glufsinate-resistant sugarbeet cmpared with cnventinal POST herbicides such as the cmbinatin f desmedipham plus phenmedipham plus triflusulfurn. Studies n glufsinate-resistant sugarbeet cnducted in eastern Nrth Dakta and Minnesta demnstrated extractable sucrse yield frm glufsinate-treated sugarbeet exceeding that f sugarbeet treated with desmedipham plus triflusulfurn plus clpyralid with five start times (Dexter and Luecke 1998). The earliest first sequential herbicide treatment was made at the sugarbeet ctyledn stage, and the latest staj.1ed fur weeks thereafter. All sugarbeet plts were treated three times with a ne-week interval between applicatins. Sugarbeet injury frm glufsinate was negligible regardless f applicatin starting times. Similar studies during 1998 and 1999 revealed reduced sugarbeet yield when the first sequential glufsinate treatment was delayed until fur weeks r ne week after the ctyledn stage in 1998 and 1999, respectively (Rthe 2002). Sequential glufsinate applicatins starting tw weeks r later after the sugarbeet ctyledn stage visibly injured sugarbeet while injury was negligible with treatments starting at the ctyledn- and ctyledn-plus-ne-week stage. As the rate increased frm 0.2 t 0.4 and 0.8 kg ha-', glufsinate had t be applied t yunger sugarbeet t avid sugarbeet injury. Timing f glufsinate applicatin did nt affect weed cntrl

4 122 JOW11al f Sugar Beet Research Vl41N4 efficacy, but temprary leaf damage, especially after glufsinate applicatins at the nine-leaf stage and beynd, was als nted by Biickmann et al. (2000). This bservatin agrees with the cnclusin made by Regitnig and Nitschelm (1998) that applicatin timing f high glufsinate rates affected crp injury mre than weed cntrl. They bserved significant leaf chlrsis t glufsinate-resistant sugarbeet at ne lcatin after the third applicatin f POST glufsinate at 0.4 kg hal sholtly befre rw clsure. Nne f the glufsinate-resistant sugarbeet experiments have investigated the effect f glufsillate-induced sugarbeet damage n sugarbeet yield cmpnents. Therefre, the bjective f this research was t determine if injury t glufsillate-resistant sugarbeet frm late seasn glufsinate treatments caused yield lss; and t assess cumulative phyttxic effects frm glufsinate at varius rates. MATERIALS AND METHODS Field studies were cnducted near St. Thmas, ND and Crkstn, MN, in A third experiment near Farg, ND, was terminated prir t harvest because f flding, and therefre will nt be discussed. Glufsinate-resistant 'Beta 2012' sugarbeet was seeded 3 cm deep and 7.6 cm apart in 56-cm wide rws with a cnventinal sugarbeet planter. Individual experimental units cnsisted f six ll-m-lng sugarbeet rws f which the tw uter rws were untreated. Terbufs was applied mdified in-furrw at seeding fr rt maggt [Tetanps mypaejrmis (Rder)] cntrl. Fungicides fr Cercspra leaf spt (Cercspra beticla Sacc.) cntrl, and additinal rt maggt insecticides were sprayed thrughut the grwing seasn when necessary. Sugarbeet at the seedling stage was hand thinned t 4 t 5 plants per m f rw. Planting, thinning, and harvest dates are listed in Table 1. Glufsinate was applied t sugarbeet fur times r ne time at 0.2,0.4, and 0.8 kg ai. ha- l, where 0.4 kg ha- l represents the IX r nrmal use rate. Multiple glufsinate treatments were at ne-week intervals beginning ne, three, r fur weeks after the sugarbeet ctyledn stage. Single glufsinate treatments were applied six r seven weeks after the sugarbeet ctyledn stage, r at the same tillle as the last applicatin f the multiple glufsinate treatments that started three r fur weeks after the sugarbeet ctyledn stage. These treatments permitted cmparisn Table 1. Glufsinate-resistant sugarbeet ill Lcalln plantmg date Hand-thinnmg date Harvest date St. Thmas, ND April 27 July 5 September 28 Crkstn, MN May 2 June 30 Octber 3

5 Octber - December 2004 Impact f Injury 123 f phyttxic effects frm single versus multiple glufsinate applicatins. Plts treated fur times with glufsinate starting ne week after the sugarbeet ctyledn stage were cmpared t plts treated fur times stalting three r fur weeks after the sugarbeet ctyledn stage. All plts were hand weeded prir t the first glufsinate applicatin t minimize weed interference with sugarbeet yield and t detect treatment effects in the absence f weeds. Nn-herbicide-treated plts were included fr yield and sugarbeet injury cmparisns and were regularly hand weeded until either six r seven weeks after the sugarbeet ctyledn stage. Plts treated with glufsinate at three r six weeks after the sugarbeet ctyledn stage were cmpared t plts that were hand weeded until six weeks after the sugarbeet ctyledn stage. Hand weeding stpped at the same time as the last glufsinate applicatin. Plts receiving glufsinate at either fur r seven weeks after the sugarbeet ctyledn stage were cmpared t untreated plts that were hand weeded until seven weeks after the sugarbeet ctyledn stage. Late seasn weed cmpetitin was eliminated when necessary t keep all plts weed-free until harvest. Glufsinate was applied t the fur inside rws in 160 L ha- l water at 280 kpa thrugh 8002 flat fan nzzles using a CO 2 -pressurized bicycle-wheel-type plt sprayer traveling at 4.8 km h-l. Treatment dates, envirnmental cnditins, and sugarbeet grwth stage at the time f applicatin r hand weeding were recrded (Table 2). Sugarbeet injury in the center fur rws was scred visually n a scale f a t 100 (0 = n leaf chlrsis, r bimass reductin; and 100 =cmplete kill) apprximately 7 and 21 days after the last f all herbicide treatments (DALT) were applied. Fr this purpse, the glufsinate-treated and hand-weeded center rws were cmpared t the tw uter untreated rws f each plt. Sugarbeet ppulatins were determined by cunting rts in the tw center harvested rws f each plt. Harvested rts were weighed in the field, and 10 t 15 unifrm, visibly disease-free rts were taken frm each plt. Percent tare, impurity, and sucrse cntent in these sugarbeet samples were determined by the American Crystal Sugar Cmpany research labratry at Mrhead, MN, using standard labratry prcedures develped by the cmpany. The experimental design was a randmized cmplete blck with five replicates. Experiments were cmbined ver lcatins based n hmgeneus errr mean squares btained frm the single analysis f variance (ANOVA) tested accrding t Barlett's Chi-square test. Accrding t the research bjectives, certain pre-determined treatment pairs were cmpared using single-degree-f-freedm cntrasts at the 0.05 level f significance.

6 Table 2. Envirnmental cnditins and sugarbeet grwth stage at the time f glufsinate applicatin in Lcatin St. Thmas Crkstn St. Thmas Crkstn St. Thmas Crkstn St. Thmas Crkstn Glufsinate applicatin t Date Air temperature Relative humidity Sugarbeet grwth stage C % Ctyledn + 1 week 05/ Ctyledn + 2 weeks 05/31 06/ Cty 1edn + 3 weeks 06/07 06/ Ctyledn + 4 weeks 06/ Ctyledn + 5 weeks 06/22 06/ Ctyledn + 6 weeks / Ctyledn + 7 weeks 07/06 07/ tglufsinate was applied in reference t the sugarbeet develpment stage beginning at ne, three, fur, six, and seven weeks after the sugarbeet ctyledn stage. Glufsinate treatments starting at ne, three, and fw weeks after the ctyledn stage were applied fur times in ne-week intervals. Fr example, the "Ctyledn + 1 week" starting time treatment included glufsinate applicatins at Ctyledn + 1 week, Ctyledn + 2 weeks, Ctyledn + 3 weeks, and Ctyledn + 4 weeks. Glufsinate treatments were applied nly nce starting at six and seven weeks after the ctyledn stage. V1.0 =sugarbeet ctyledn stage, V2.0 =sugarbeet with tw unriled true leaves, and V2.5 =sugarbeet with tw unrlled true leaves and a third leaf 50% urn iled, etc. N -... '-< r:.. g, C/) c (TQ t (t) :;>;:I (t) '" (t) ::T s: -... z...

7 Octber - December 2004 Impact f Injury 125 RESULTS AND DISCUSSION A cntrast analysis f early seasn versus late seasn glufsinate applicatin starting times acrss lcatins and averaged ver glufsinate rates, indicated n significant effect n sugarbeet ppulatin and rt yield (Table 3). Glufsinate applied fur times starting ne week after the ctyledn stage f sugarbeet, n average, injured plants 0 t 4%, whereas injury was up t 26% when glufsinate applicatin sequences started three weeks r later after the ctyledn stage. Despite the increased sugarbeet injury 7 and 21 DALT due t late seasn sequential glufsinate applicatins, extractable sucrse per hectare was similar in early- and late-treated sugarbeet. The absence f a difference in sugarbeet rt yield and extractable sucrse, regardless f glufsinate applicatin starting time, suggests that sugarbeet either partially vercame the bserved leaf chlrsis r that late-appearing significant visible injury had n adverse effect n sugarbeet yield traits. Sugarbeet recvery frm glufsinate injury within tw weeks after applicatin was bserved by Nitschelm and Regitnig (1997). Glufsinate applied fur times at 0.2 kg ha- J (O.5X) did nt injure sugarbeet at 7 DALT when treatments were statted at ne week rather than three r mre weeks after the ctyledn stage (Table 3). Althugh sugarbeet injury 21 DALT was significantly greater in late seasn glufsinate treatments cmpared with early seasn treatments, these relatively lw levels f injury wuld nt be expected t reduce sugarbeet yield. All plts had similar sugarbeet ppulatins, and prduced sinular rt and extractable sucrse yield. Glufsinate at 0.4 and 0.8 kg ha- J applied fur times starting at three weeks r later after the sugarbeet ctyledn stage caused greater visible sugat'beet injury 7 and 21 DALT than glufsinate applicatin sequences starting at ne week after the ctyledn stage, but sugarbeet ppulatins, rt, and extractable sucrse yields were nt affected. Sugarbeet yield lss assciated with sequential glufsinate applicatins starting three weeks r later after the sugarbeet ctyledn stage was bserved in previus experiments during 1998 and 1999 (Rthe 2002). Based n the results shwn in Table 3, sugarbeet yield lss in the previus research was nt due t the greater, visible herbicide-induced sugarbeet injuly frm late seasn treatments cmpared t minimal injury frm glufsinate treatments starting at the ctyledn stage r ne week later. Cmpetitin frm uncntrlled weeds plir t the first f the late seasn sequential glufsinate applicatins prbably caused the yield reductin, illustrating the need t eliminate weeds early in the grwing seasn fr maximum sugarbeet yield. Weed cmpetitin in this experiment was eliminated thrugh hand weeding until glufsi

8 Table 3. Late versus early seasn glufsinate applicatin starting times, cmbined ver Crkstn, MN, and St. Thmas, ND, Glufsinate-starting-tirne Glufsinate Sugarbeet Rt Sugarbeet injury Extractable treatment cmparisn! rate ppulatin yield 7DALT 21 DALT sucrse kg ha! plantsll 00 m t ha! % kg ha! C+l vs C+3 Ct4 C+6 C+7 0.2, 0.4, 0.8! NS NS (4vs16)* (2 vs 13)* NS C+l vs C+3 C+4 C+6 C NS NS NS (2 vs 6). NS C+l vs C+3 C+4 C+6 C NS NS (3 vs 14)* (0 vs 13)* NS C+l vs C+3 C+4 C+6 C NS NS (4 vs 26)* (3 vs 21)* NS!Abbreviatins: C = Ctyledn stage f sugarbeet. C+1, 3, 4, 6, r 7 indicate the number f weeks after the sugarbeet ctyledn stage at which the first glufsinate applicatin was made. Glufsinate was applied fur times starting at C+ 1, C+ 3, and C+4 at apprximately ne week intervals and nly nce at C+6 r C+ 7. *Abbreviatin: DALT = days after the last treatment. leach glufsinate-starting-time treatment was averaged ver the three glufsinate rates. NS=Cntrast was nn-significant at the 0.05 prbability level. *Cntrast was significant at the 0.05 prbability level. N 0- '-< 3 a ọ..., C/) <= ()"Q t (1) ::Il (1) en (1) ::; z

9 Octber - December 2004 Impact f Injury 127 nate treatments were started while weeds were allwed t grw UJiliindered until the first herbicide treatment in the 1998 and 1999 experiments (Rthe 2002). This research indicates that glufsinate-resistant sugarbeet recvered frm the significant visible injury caused by late seasn sequential glufsinate applicatins withut a significant effect n sugarbeet yield. The cumulative effect f sequential multiple glufsinate applicatins n sugarbeet yield was cmpared t the effect frm single glufsinate treatments. The number f glufsinate applicatins, averaged ver au herbicide rates, influenced sugarbeet ppulatin and sugarbeet injury 7 DALT (Table 4). Sugarbeet ppulatins were greater in plts that received fur sequential glufsinate applicatins averaged ver starting times, including three and fur weeks after the sugarbeet ctyledn stage than in plts that were treated nce with glufsinate averaged ver starting times, including six and seven weeks after the ctyledn stage. Plts that were sprayed nly nce as ppsed t fur sequential glufsinate applicatins were hand weeded ver a lnger perid f time, with the last hand weeding cmpleted when sugarbeet had apprximately 12 r 19 leaves (Table 2), respectively, fr multiple and single glufsinate applicatins. The lnger perid f hand weeding may have caused greater physical sugarbeet damage and remved mre sugarbeet plants. Sugarbeet ppulatin was less in plts receiving a single rather than fur glufsinate treatments at 0.4 and 0.8 kg ha ' but plts treated ne r fur times at 0.2 kg ha ' had sirmlar ppulatins. (Table 4). An early activatin f the resistance mechanism by sugarbeet plants in respnse t multiple early seasn glufsinate treatments may have made the plants mre tlerant t glufsinate while a single late seasn glufsinate applicatin at increased rates may have verwhelmed the prly r inadequately activated resistance mechanism within a few sugarbeet plants. Observatins f visible injury symptms indicated that small sugarbeet plants were inherently mre tlerant t glufsinate than larger plants. The reasn fr sugarbeet stand lss in sme treatments is nt knwn but the remaining sugarbeet ppulatins were adequate and yield was nt affected. Averaged ver glufsinate rates, sugarbeet injury 7 DALT was slightly greater with multiple glufsinate treatments starting at three and fur weeks after the sugarbeet ctyledn stage cmpared with single glufsinate treatments at six and seven weeks after sugarbeet had ctyledns (Table 4). The number f glufsinate applicatins, averaged ver herbicide rates, did nt affect sugarbeet rt yield nr extractable sucrse yield. Sugarbeet plts that were treated fur times and, there

10 Table 4. Effect f multiple versus single glufsinate applicatins n sugarbeet, cmbined ver Crkstn, MN, and St. Thmas, ND,2000. Glufsinate applicatins; Glufsinate Sugarbeet Rt Sugarbeet injury Extractable Fur One rate ppulatin yield 7DALT 21 DALT sucrse kgha' plants/loo m t ha-' % kgha-' C+3 C+4 vs C+6 C+7 0.2, 004, 0.8! (395 vs 376)* NS (19 vs 13)* NS NS C+3 C+4 vs C+6 C (386 vs 390)NS NS NS NS NS C+3 C+4 vs C+6 C (390 vs 371)* NS NS NS NS C+3 C+4 vs C+6 C (410 vs 370)* NS (Lac x C)# NS NS tabbreviatins: C = Ctyledn stage f sugarbeet. C+3, 4, 6, r 7 indicate the number f weeks after the sugarbeet ctyledn stage at which the firs t glufsinate applicatin was made. Glufsinate was applied fur times starting at C+3 and C+4 at apprximately ne-week inter vals and nly nce at C+6 r C+ 7. I Abbreviatin: DALT = days after the last treatment.! Each glufsinate-starting-time treatment was averaged ver three glufsinate rates. * Cntrast was significant at the 0.05 prbability level. NS=Cntrast was nn-significant at the 0.05 prbability level. #The lcatin-by-cntrast interactin was significant at the 0.05 prbability level but was due t magnitude rather than rank in treatment.... N 00 '-< 8 e: ọ.., U'l ::: tj<i e; t (1) ::>::l (1) '" (1) ::>"... +> z +>

11 Octber - December 2004 Impact f Injury 129 fre, received fur times the amunt f the tested glufsinate rate prduced yield similar t sugarbeet treated nly nce. Sugarbeet treated with glufsinate at 0.2 and 0.4 kg ha ) had similar injury regardless f the number f applicatins (Table 4). The cntrast effect and its interactin with the lcatin were significant fr sugarbeet injury 7 DALT with glufsinate at 0.8 kg ha ' but the significance was due t magnitude. At bth lcatins, sugarbeet injury was greater with multiple glufsinate applicatins than with single applicatins (data nt shwn). Regardless f the rate, plts treated with glufsinate either ne r fur times gave similar sugarbeet rt yield and extractable sucrse (Table 4). This bservatin cnfmns the lack f any significant cumulative phyttxic effect n sugarbeet yield frm multiple glufsinate applicatins. Fr each rate cmparisn, including all glufsinate treatments at any starting time, the lwer f the tw glufsinate rates cnsistently caused less sugarbeet injwy 7 and 21 DALT (Table 5). A decline in sugarbeet injury was bserved between 7 and 21 DALT fr all treatment cmparisns, indicating partial recvely frm visible herbicide-induced symptms. Sugarbeet ppulatin, rt yield, and extractable sucrse were nt affected by glufsinate rate, averaged ver all glufsinate starting times. Crrespnding pairs f glufsinate-treated and hand-weeded sugarbeet plts, averaged ver glufsinate rates, are cmpared in Table 6. Sugarbeet ppulatin, rt yield, and extractable sucrse were similar amng all plts, regardless f treatment. Glufsinate caused significantly greater sugarbeet injury than hand weeding (Table 6). The significant lcatin-by-cntrast interactin fr sugarbeet injury 7 DALT was due t magnitude rather than treatment rank based n the bservatin that handweeded sugarbeet in bth treatment cmparisns were injured less than hand-weeded plus glufsinate-treated sugarbeet at Crkstn, MN, and St. Thmas, ND (data nt shwn). Results in this research indicate that sugarbeet yield was nt negatively affected regardless f the number f sequential glufsinate applicatins and glufsinate rate. ACKNOWLEDGMENTS Appreciatin is expressed t the Sugarbeet Research and Educatin Bard f Minnesta and Nrth Dakta fr financial supprt, t the persnnel f the NOlthwest Research and Outreach Center University f MN Crkstn fr their assistance in managing the research sites, t the summer student and sugarbeet harvest crews fr their valuable field wrk, and t American Crystal Sugar Cmpany fr sugarbeet quality analysis.

12 Table 5. Rate effect f glufsinate n sugarbeet stand, injury, and yield, averaged ver glufsinate starting times, and cmbined ver Crkstn, MN, and St. Thmas, ND, Glufsinate rate Sugarbeet Rt Sugarbeet injury Extractable treatment cmparisn t ppulatin yield 7 DALT 21 DALT sucrse kg ha 1 plants/loo m t ha % kgha vs 0.4 C+l C+3 C+4 C+6 C+7 vs C+l C+3 C+4 C+6 C+7 NS NS (7 vs 12)* (5 vs 10)* NS 0.2 vs 0.8 C+l C+3 C+4 C+6 C+7 vs C+l C+3 C+4 C+6 C+7 NS NS (7 vs 22)* (5 vs 17)* NS 0.4 vs 0.8 C+l C+3 C+4 C+6 C+7 vs C+l C+3 C+4 C+6 C+7 NS NS (12 vs 22)* (10 vs 17)* NS tabbreviatins: C = Ctyledn stage f sugarbeet. C+1, 3, 4, 6, r 7 indicate the number f weeks after the sugarbeet ctyledn stage at which the first glufsinate applicatin was made_ Glufsinate was applied fur times st3lting at C+J, C+3, and C+4 at apprximately ne week intervals and nly nce at C+6 r C+ 7. ; Abbreviatin: DALT = days after the last treatment. NS=Cntrast was nn-significant at the 0.05 prbability level. * Cntrast was significant at the 0.05 prbability level. -VJ '-< ;3 e ọ..., (/.l c: (JO i:l t (1) io (1) =:>" -I' z -I'

13 Table 6. Effect f hand weeding and hand weeding plus glufsinate n sugarbeet stand, injury, and yield, cmbined ver Crkstn, MN, and St. Thmas, ND, Treatment! Olufsinate Sugarbeet Rt Sugarbeet i11il Extractable HW + Glufsinate Hand weeding rate' 12 l2ulati11 yield 7 DALT; 21 DALT sucrse kg ha ' plantslloo m t hal % kgha ' C+6 vs C+6 0.2, 0.4, 0.8 NS NS Lc x C# NS NS C+3 vs C+6 0.2, 0.4, 0.8 NS NS Lc x C# NS NS C+7 vs C+7 0.2, 0.4, 0.8 NS NS (16 vs 2)* NS NS C+4 vs C+7 0.2, 0.4, 0.8 NS NS (24 vs 2)* NS NS 'Abbreviatins: HW+Glufsinate C+3, C+4, C+6, and C+ 7 = Plts that were hand weeded at weekly intervals starting at the sugarbeet ctyledn stage until 3, 4, 6, and 7 weeks thereafter, respectively. The la t hand weeding was immediately fllwed by glufsinate appli catins. Glufsinate was applied fur times starting at C+3 and C+4 at apprximately ne-week intervals and nly nce at C+6 r C+ 7; therefre, C+3 and C+4 treatments ended at the same time as C+6 and C+ 7 treatments, respectively., Each glufsinate-starting-time treatment was averaged ver three glufsinate rates.! Abbreviatin: DALT = days after the last treatment. NS=Cntrast was nn-significant at the 0.05 prbability level. # The lcatin-by-cntrast interactin was significant at the 0.05 prbability but was due t magnitude rather than rartk in treatments. * Cntrast was significant at the 0.05 prbability level. 8 0 t:j (l) (l) 3 it >; 1-0 a "Cl '" ọ..., >-< 2. VJ -

14 132 Juma! f Sugar Beet Research V141N4 LITERATURE CITED Ahrens, W. H. (ed.) Herbicide Handbk. 7th Editin. Champaign, IL: Weed Sci. Sc. Am. pp Bray, W. E Crp damage frm herbicide use in sugarbeet. In Aspects f applied bilgy. 3. Crp sensitivity t herbicides. Wellesbume, UK: Assc. f Applied Bilgists pp Biickmann, H., J. Petersen, G. Schlinker, and B. Marliinder Weed cntrl in genetically mdified sugarbeet-tw year experiences f a field trial series in Germany. Z. Pflanzenkrankh. Pflanzenschutz, Snderh. XVII: Dawsn, J. H Cmpetitin f late emerging weeds with sugarbeets. Weed Sci. 25: Dexter A. G. and J. L. Luecke Weed cntrl in transgenic sugarbeet in Nrth Dakta and Minnesta In 1997 Sugarbeet Res. and Extensin Rep. Farg, ND: NDSU Extensin Serv 27:62:67. Dexter, A. G. and J. L. Luecke Survey f weed cntrl and prductin practices n sugarbeet in eastem Nrth Dakta and Minnesta In 2002 Sugarbeet Res. and Extensin Rep. Farg, ND: NDSU Extensin Serv 33: Dexter, A. G. and R. K. Zllinger Weed cntrl guide fr sugarbeet. In 2002 Sugarbeet Res. and Extensin Rep. Farg, ND: NDSU Extensin Serv 33:3-34. D'Halluin, K. D., M. Bssut, E. Bnne, B. Mazur, J. Leemans, and J. Bttennan Transfrmatin f sugarbeet (Beta vulgaris L.) and evaluatin f herbicide resistance in transgenic plants. BifTechnl. 10: Edmund, R. M., Jr. and A. C. Yrk Factrs affecting pstemergence cntrl f sicklepd (Cassia btusiflia) with imazaquin and DPX-F6025; spray vlume, grwth stage, and sil-applied alachlr and vemlate. Weed Sci. 35:

15 Octber - December 2004 Impact f Injury 133 Eshel, Y, E. E. Schweizer, and R. L. Zimdah! Sugarbeet tlerance f pstemergence applicatins f desmedipham and ethfumesate. Weed Res. 16: Hendrick, L. w., W. F. Meggitt, and D. Penner Selective use f phenmedipham and EP-475 in Michigan fr weed cntrl in sugarbeets. J. Am. Sc. Sugar Beet Techn!. 18: Lee, S. D. and L. R. Oliver Efficacy f aciflurlen n bradleafweeds. Tunes and methds fr applicatin. Weed Sci. 30: Miller, S. D. and K J. Frnstrm Assessment f herbicide benefits in sugarbeets (Beta vulgaris). J. Sugar Beet Res. 25: Miller, S. D. and K J. Frnstrm Weed cntrl and labr requirements in sugarbeets. J. Sugar Beet Res. 26:1-9. Nitschelm,1. J. and P. J. Regitnig Effect f Liberty herbicide frmulatins, rates and timing n brad-spectrum weed cntrl and Liberty Link sugar beets In Annual Res. Rep Winnipeg, Canada: Rgers Sugar Ltd. pp Nrris, R. F Influence f envirnment n activity f phenmedipham. Prc. Calif. Weed Cnf. 26: Nrris, R. F Sugarbeet tlerance and weed cntrl efficacy with split applicatins f phenmedipham plus desmedipham. Weed Res. 31: Platte, H., B. Miirlander, M. Niemann, L. BeiBner, G. Buttner, E. Laedewig, andw. R. Schiiufele Weed cntrl in genetic mdified sugar beets. Zuckerindustrie 123 (9): Prestn, P. E. and P. V. Brisce The tlerance f sugar beet t pst-emergence herbicide applicatins. In Aspects f applied bilgy. 2. Pests, diseases, weeds and weed beet in sugar beet. Wellesbume, UK: Assc. f Applied Bilgists pp Prdehl, KA., L.G. Campbell, and A.G. Dexter Phenmedipham + desmedipham effects n sugarbeet. Agrn. J. 84:

16 134 Jurnal f Sugar Beet Research Vl 41 N 4 Regitnig, P. 1. and Nitschelm Effect f Liberty herbicidefrmulatins, rates and timing n brad-spectmm weed cntrl and Liberty Link sugar beets In Annual Res. Rep Winnipeg, Canada: Rgers Sugar Ltd. pp Ritter, R. L. and H. D. Cble Influence f crp canpy, weed maturity, and rainfall n aciflurfen activity. Weed Sci. 32: Rthe, I Pst emergence weed cntrl in glufsinate- and glyphsate-resistant sugarbeet (Beta vulgaris L.). Ph.D. Dissertatin. Nrth Dakta State Univ., Farg, ND. Schweizer, E. E Herbicides applied sequentially fr ecnmic cntrl f annual weeds in sugarbeets. Weed Sci. 28: Sctt, R. K, S. 1. Wi1ccksn, and N. R. Pre Sme effects f tinting f weed cntrl in the sugar beet crp. Prc. British Crp Prt. Cnf.- Weeds pp Thrsness, K B., 1. F. Stewart, T. W. Kleven, and C. P. Hicks An verview:glufsinate in transgenic sugarbeets. Prc. Nrth Cent. Weed Sci. Sc. 53: Vasil, I. K Phsphinthricin-resistant crps. In S. O. Duke, ed. Herbicide-resistant crps. Agricultural, envirnmental, ecnmic, regulatry, and technical aspects. Bca Ratn, FL: CRC Press pp Weinlaeder, R. A. and A. G. Dexter Several factrs influencing sugarbeet injury in the field and grwth chamber. Prc. Nrth Cent. Weed Cntrl Cnf. 27:33. Weyers, 1. D. A Agrnmic and envirnmental aspects f herbicide-resistant sugar beet in the Netherlands. In Aspects f applied bilgy. 52. Prtectin and prductin f sugar beet and ptates. Wellesburne, UK: Assc. f Applied Bilgists pp Wicks, G. A. and R. G. Wilsn Cntrl f weeds in sugarbeets (Beta vulgaris) with hand heing and herbicides. Weed Sci. 31:

17 Octber - December 2004 Impact f Injury 135 Wilsn, R. G Pstemergence herbicide timing fr maldmum weed cntrl in sugarbeet. J. Sugar Beet Res. 35: Wilsn, R. G Glyphsate and glufsinate fr weed cntrl in herbicide tlerant sugarbeet. Am. Sc. Sugar Beet Technl. Abstr.49. Wmter, S. R. and A F. Wiese Phyttldcity and yield respnse f sugarbeets (Beta vulgaris) t a mixture f pbenmedipham and desmediphanl. Weed Sci. 26: 1-4.