Evaluation of Weed Control and Crop Safety with Herbicides in Open Field Tree Nurseries

Transcription

1 Weed Tehnology : Evlution of Weed Control nd Crop Sfety with Heriides in Open Field Tree Nurseries Brdley D. Hnson nd Slly A. Shneider* Open field prodution of fruit nd nut-tree nursery stok depends upon preplnt soil fumigtion, extensive tillge, nd hnd-lor throughout the growing seson for dequte weed ontrol. Beuse methyl romide, the fvored fumignt, is eing phsed out euse of environmentl onerns nd the osts of oth fuel nd lor ontinue to rise, heriides re likely to eome more importnt weed mngement tool in the tree nursery industry. Two trils were onduted to evlute weed ontrol nd rop sfety with severl heriides pplied following fumigtion with methyl romide or 1,3- dihloropropene in entrl Cliforni stone-fruit nurseries. PRE nd POST-direted pplitions of severl leled nd unleled mterils were pplied in nd over seeded peh rootstok or pplied fter emergene with drop-nozzle spry oom. Crop produtivity nd weed ontrol were monitored throughout the 1-yr growing seson. PRE oryzlin nd dithiopyr tretments provided the est weed ontrol with very little rop injury. PRE pplitions of flumioxzin, rimsulfuron, nd sulfentrzone did not hve dequte rop sfety t the rtes nd timings tested. However, POST-direted pplitions of flumioxzin nd rimsulfuron were muh sfer to the peh nd lmond rops nd should e evluted in future trils. Additionl heriides nd pplition tehniques re needed to find eptle, sfe ontrol mesures for weeds, suh s Cliforni urlover, ommon mllow, nd redstem filree, whih often re poorly ontrolled with preplnt fumigtion in tree nurseries. Nomenlture: Dithiopyr; flumioxzin; isoxen; oryzlin; prodimine; rimsulfuron; sulfentrzone; Cliforni urlover, Medigo hispid Gertn. MEDPO; ommon mllow, Mlv prviflor L. MALPA; redstem filree, Erodium iutrium L EROCI; lmond, Prunus dulis Mill.; peh, Prunus persi Btsh. Key words: Bre root tree, heriide sreening, methyl romide lterntives, seletivity, tolerne, tree nursery. Cliforni nurseries produe 60% of the totl fruit nd nut plnts sold in the United Sttes, with n nnul vlue of $165 million to the eonomy of the stte (NASS 2007). Deiduous fruit nd nut trees re mjor omponent of this nursery setor nd lrgely supply plnting mteril for the inrese nd mintenne of nerly 1.2 million ering res of peh, plum (Prunus domesti L.), priot (Prunus rmeni L.), netrine [Prunus persi Btsh vr. netrin (Aiton) Mxim.], lmond [Prunus dulis (Mill.) D. A. We vr. dulis], pisthio (Pisti ver L.), nd wlnut ( Juglns regi L.) in Cliforni lone (NASS 2007). Trditionlly, open field prodution of deiduous tree nursery stok is 3- to 5-yr yle tht egins with preplnt soil fumigtion the summer efore the nursery rop is estlished. Seed or hrdwood uttings of rootstok re plnted in the fll nd udded or grfted to preferred sion vriety in spring or summer of the next yer. However some nut trees, inluding wlnut nd pen [Cry illinoinensis (Wngenh.) K. Koh] re grfted in the spring of the seond yer euse of the preferene for lrger plnting stok in these mrkets. After rehing trget size (usully fter one or two growing sesons) nd going dormnt in the fll, the trees re hrvested with n underutting digger nd soil is removed from the roots. The re-root trees re wshed, grded ording to trunk dimeter nd root nd stem qulity, nd heeled-in or held in old storge efore sle to ommeril fruit nd nut DOI: /WT * Reserh Agronomist, U.S. Deprtment of Agriulture, Agriulturl Reserh Servie, 9611 S. Riverend Ave., Prlier, CA 93658; Ntionl Progrm Stff, U.S. Deprtment of Agriulture, Agriulturl Reserh Servie, Crop Prodution nd Protetion, GWCC, Room , Beltsville, MD Corresponding uthor s E-mil: rd.hnson@rs.usd.gov orhrds in Cliforni nd interstte nd interntionl mrkets. Following the tree nursery rop, fields re typilly plnted with over rop or left fllow for 1 to 3 yr. Produers of field-grown tree nd vine nursery stok rely on soil fumigtion for rod-spetrum ontrol of vriety of soilorne pests, inluding prsiti nemtodes, disese pthogens, nd weeds (Shneider et l. 2003). For more thn 50 yr, methyl romide (MeBr) hs een widely used for soil fumigtion in high-vlue vegetle, fruit, nd nursery rops ut is urrently eing phsed out euse of dverse environmentl impts (UNEP 1999). Intensive reserh efforts hve identified severl fumignt tretments tht effetively ontrol nemtodes nd pthogens in some situtions (CDFA 2005; Norton 2005). However, none of the urrently registered nd ville hemil lterntives hs the sme spetrum of tivity, pest ontrol effiy, nd grower onfidene s MeBr (Duniwy 2002). Even with preplnt soil fumigtion, weed ontrol in perennil-rop field nurseries is reurring prolem for mny produers in the Centrl Vlley of Cliforni (Shresth et l. 2008). Soil fumigtion lone often does not provide nd mintin onsistently high level of weed ontrol over 1- to 3-yr rop yle euse of weed speies iology (impermele seed ot, dormny), eology (irorne invsion, lrge seed nk), or response to environmentl onditions (dry soil) (Hnson nd Shresth 2008). Tree seedlings nd newly estlished uttings re not very ompetitive; therefore, even moderte levels of weed infesttion n derese tree rop estlishment nd produtivity (Altlnd et l. 2003; Willoughy et l. 2006). In nursery rops, weeds n lso interfere severely with ulturl prties, inluding udding, grfting, pruning, nd vrious hrvest opertions. Most perennil rop Hnson nd Shneider: Tree nursery heriide sreening N 493

2 Tle 1. Crop prodution, pest ontrol, nd site informtion for two heriide/fumigtion trils in stone-fruit tree nurseries loted ner Hikmn, CA, nd Yu City, CA, in Site onditions Hikmn, CA Stnislus County Yu City, CA Sutter County Previous rop 2006 whet/pe over rop 2006 winter whet Lst nursery rop 2003 stone-fruit trees No nursery, long-term orhrd Soil type Sndy lom Cly lom Fumigtion dte August 10, 2006 Septemer 9, 2006 Plnting dte Septemer 5, 2006 Otoer 11, 2006 Rootstok vriety Nemgurd peh Nemgurd peh PRE heriide pplition dte Otoer. 25, 2006 Otoer. 17, 2006 Soil temp t 2 inhes 17 C 21 C Air temperture 22 C 27 C Humidity 33% 31% Soil ondition Dry, smll lods Dry surfe POST-direted heriide pplition dte Mrh 7, 2007 Mrh 1, 2007 Soil temp t 2 inhes 21 C 7 C Air temp 29 C 12 C Humidity 36% 55% Soil ondition Dry surfe Wet surfe Overspry heriide tretment None Glyphoste, Jnury 15, 2007 Budding dte June 22, 2007 June 4, 2007 Sion vriety Severl Monterey lmond Finl evlution dte Novemer 16, 2007 Deemer 6, 2007 Tree hrvest Novemer 20, 2007 Deemer 20, 2007 The Hikmn, CA, lotion ws udded with severl sion vrieties. The trees in the 1,3-D lok were udded with Folsom lmond nd n experimentl lmond vriety, wheres the trees in the methyl romide lok were udded with two experimentl peh nd two experimentl netrine vrieties. nursery prodution systems urrently rely on omintion of preplnt soil fumigtion, PRE heriides, nd extensive tillge nd hnd-lor during the growing seson for eptle weed ontrol. Currently, PRE nd erly POST heriide hoies re limited y the numer of registered mterils nd y rop sfety onerns (Zheljzkov et l. 2007). Heriides likely will eome n even more importnt weed mngement tool in tree nurseries s MeBr eomes less ville nd lor nd fuel osts ontinue to rise (Altlnd et l. 2003; Gillim et l. 1989). Identifition of heriides nd heriide pplition tehniques tht provide effetive, nonphytotoxi, in-seson weed ontrol in perennil rop field nurseries will provide growers with dditionl mngement options for effetive nd eonomil prodution of fruit nd nut tree nursery stok. The speifi ojetives of this study were to determine (1) weed ontrol effiy of severl PRE nd POST heriide tretments in stone-fruit tree field nursery, (2) the impt of the heriide tretments on rop estlishment, nd (3) the effet of tretments on the helth, vigor, nd produtivity of the rop. Mterils nd Methods Two nursery tril sites were identified ner Hikmn, CA, nd Yu City, CA, in the entrl nd northern prt of Cliforni s Centrl Vlley, respetively. The soil t the Hikmn, CA, site ws sndy lom with ph 7.3, 1.1% orgni mtter, nd 68% snd, 16% silt, nd 16% ly. At the Yu City, CA, site, the soil ws silty-ly lom with ph 7.1, 2.2% orgni mtter, nd 19% snd, 51% silt, nd 30% ly. Beuse preplnt fumigtion or extensive soil nd root smpling is neessry to meet nemtode-free ertifition requirements, most nursery opertions will ontinue to use either MeBr (under Qurntine nd Preshipment or under Critil Use Exemptions) or 1,3-dihloropropene fumignts (CDFA 2005). Thus, the ooperting growers prepred the fields for preplnt fumigtion using pproprite tillge nd soil moisture mngement tehniques. At eh lotion, two 0.12-h res were ommerilly fumigted (TriCl In., Hollister, CA) with 392 kg/h of 98 : 2 MeBr or 372 kg/h 1,3-dihloropropene (1,3-D), respetively (Tle 1). The two fumigtion loks were 10 to 30 m prt in eh field. MeBr ws pplied with Nole plow fumigtion rig, with injetion points 30 m deep nd sping of 30 m etween nozzles, nd using roller nd stndrd (high-density polyethylene, HDPE) trp on the rig. The 1,3-D tretments were pplied with modified Telone fumigtion rig, with injetion points 46 m deep, nd with sping of 51 m etween nozzles nd ws followed y the Nole plow rig to ly the HDPE trp. Eh lotion lso hd n unreplited, unfumigted re (,0.04 h) for evlution of pest pressure. At the Yu City, CA, site, n dditionl trp vs. no-trp omprison ws onduted in the nonfumigted re to evlute the effets of solriztion. Trps remined on the experimentl plots for pproximtely 3 wk. The ooperting growers prepred the seed ed for plnting nd seeded Nemgurd peh seed in fll 2006 (Tle 1). The rop ws plnted 8 m prt with 1.5 m etween rows t the Hikmn, CA, site nd 15 m prt with 1.4-m row sping t the Yu City, CA, site. A totl of 15 heriide tretments were pplied to oth the MeBr nd 1,3-D loks (Tle 2). PRE heriide tretments (tretments 2 10 nd 15) were pplied in 0.9-m nd over the seed row fter seeding of the peh rootstok, using CO 2 -pressurized kpk spryer lirted to deliver 187 L/h. The Yu City, CA, oopertor lso pplied rodst glyphoste tretment over ll plots in Jnury 2007 to ontrol existing 494 N Weed Tehnology 22, July Septemer 2008

3 Tle 2. Weed popultion ounts on Mrh 15, 2007 (4.5 mo fter initil tretment), in nursery experiment ner Hikmn, CA, nd on April 17, 2007 (5 mo fter initil tretment), in nursery experiment ner Yu City, CA. Weeds were ounted in 25-m untilled strip in the tree seedling row. Hikmn, CA site Yu City site Tretment Totl weeds Totl weeds Common mllow Cliforni urlover No. Heriide Rte Timing MeBr 1,3-D MeBr 1,3-D MeBr 1,3-D MeBr 1,3-D kg i/h No. weeds/7.6 m of row No-heriide Oryzlin 1.12 PRE Prodimine 1.12 PRE Isoxen 1.12 PRE Flumioxzin 0.14 PRE Flumioxzin 0.28 PRE Rimsulfuron PRE Dithiopyr 1.12 PRE Sulfentrzone 0.14 PRE Sulfentrzone 0.28 PRE Flumioxzin 0.14 POST-D Flumioxzin 0.28 POST-D Rimsulfuron POST-D Dithiopyr 1.12 POST-D Oryzlin f 1.12 f 0.14 PRE f POST-D flumioxzin LSD (0.05) Arevitions: No., numer; f, followed y; POST-D, POST-direted; MeBr, methyl romide; 1,3-D, 1,3-dihloropropene. Primry weeds t Hikmn, CA, were ommon mllow, Cliforni urlover, ommon hikweed, nd horseweed long with low numers of severl other winter nnul weed speies. Primry weeds t Yu City, CA, were ommon mllow, Cliforni urlover, nnul ryegrss, nnul sowthistle, prostrte knotweed, nd ommon hikweed. weeds efore rootstok emergene. Following tree emergene in the spring, the POST-direted (POST-D) tretments (tretments 11 15) were pplied in 187 L/h of wter using drop-nozzle oom equipped to spry nd on either side of the tree row. The nozzles were rrnged so tht the spry pttern ws 46 m wide on eh side of the tree row nd the nds met t the se of the trees to minimize folir heriide exposure. Individul heriide plots were 1 m wide y 7.7 m long, ontining single tree row, nd eh tretment ws replited four times in eh fumigtion lok. The ooperting nurseries thinned, udded, pruned, nd fertilized the rootstok nd udded the trees ording to their stndrd prodution prties (Tle 1). Emerged rootstok nd weeds were ounted in n re 25 to 30 m wide y 7.6 m long on Mrh 15 nd April 17, 2007 t the Hikmn, CA, nd Yu City, CA, lotions, respetively. Weed ontrol nd tree vigor were visully monitored throughout the growing seson, lthough the experimentl sites were ultivted nd hnd-weeded s pproprite y the nursery opertions. A few weeks efore hrvest, on Novemer 16, 2007, t Hikmn, CA, nd Deemer 6, 2007, t Yu City, CA, the numer of suessfully udded trees in 3 m of row ws reorded in eh plot. Trunk liper of 10 trees in eh plot (if possile), 5 m ove the grft union ws mesured nd used to determine hrvest grde in eh plot. Beuse the ooperting growers hrvested the re-root trees long with the surrounding tree stok, no posthrvest dt were olleted. Field onstrints nd fumigtion logistis required eh fumigtion lok to e treted s seprte, rndomized omplete lok t eh nursery. All dt were sujeted to ANOVA, nd mens were seprted using Fisher s Proteted LSD test with Results nd Disussion At the Hikmn, CA, lotion, the rootstok emerged in Ferury nd Mrh There were severl hundred weeds per squre meter in the unfumigted re, onsisting primrily of shepherd s purse (Cpsell urs-pstoris L), nnul sowthistle (Sonhus rvensis L), nd Cliforni urlover (Medigo hispid Gertn). Weed popultions in the 1,3-D nd MeBr fumigted loks were low nd onsisted primrily of ommon hikweed (Stellri medi), Cliforni urlover, nd ommon mllow (Mlv neglet Wllr.). An interrow tillge opertion in erly Mrh removed most of the weeds etween the heriide-treted nds in the fumigted loks ut did little to relieve weed ompetition within the row in the unfumigted re (dt not shown). On Mrh 15, 2007 (4.5 mo fter PRE tretment), ll PRE tretments, exept sulfentrzone, sustntilly redued totl weeds in the tree rows ompred with the no-heriide ontrol (Tle 2). Control with the POST-D tretments ws poor, ut those tretments my not hve rehed full impt hving een pplied only 2 wk efore the weed ounts. Lter oservtions suggested tht POST-D flumioxzin nd rimsulfuron lso suppressed mny of the weeds present (dt not shown). Although totl weed ounts were different mong heriide tretments, this ws lrgely driven y winter nnul weeds, suh s shepherd s purse nd nnul sowthistle. Counts of the mjor hrd-to-fumigte weeds, inluding mllow, urlover, nd redstem filree, were vrile nd not different mong tretments. Following the mid-mrh rting, oth fumigtion loks were ultivted nd hnd-weeded ording to the nurseries stndrd shedules, nd further detiled weed ounts were not onduted. Beuse of erly seson rop Hnson nd Shneider: Tree nursery heriide sreening N 495

4 Tle 3. Effet of heriide nd fumigtion tretments on rootstok emergene nd ud suess in two stone-fruit nursery field trils ner Hikmn, CA, nd Yu City, CA, in Hikmn, CA, site Yu City, site Tretment Rootstok emergene Budded trees Rootstok emergene Budded trees No Heriide Rte Timing MeBr 1,3-D MeBr 1,3-D MeBr 1,3-D MeBr 1,3-D kg i/h No./7.6 m of row No-heriide Oryzlin 1.12 PRE Prodimine 1.12 PRE Isoxen 1.12 PRE Flumioxzin 0.14 PRE Flumioxzin 0.28 PRE Rimsulfuron PRE Dithiopyr 1.12 PRE Sulfentrzone 0.14 PRE Sulfentrzone 0.28 PRE Flumioxzin 0.14 POST-D Flumioxzin 0.28 POST-D Rimsulfuron POST-D Dithiopyr 1.12 POST-D Oryzlin f 1.12 f PRE f flumioxzin 0.14 POST-D LSD (0.05) ns ns Arevitions: No., numer; f, followed y; POST-D, POST-direted; MeBr, methyl romide; 1,3-D, 1,3-dihloropropene; ns, not signifint. Rootstok ws Nemgurd peh in oth fumigtion loks t the Hikmn, CA, site; however, the MeBr lok ws grfted to severl peh nd netrine vrieties, wheres the 1,3-D lok ws grfted to mixture of lmond ultivrs. Rootstok emergene ws reorded on Mrh 15, 2007, nd the numer of suessfully udded trees ws reorded on Novemer 16, At the Yu City, CA, site, the rootstok ws Nemgurd peh, nd the sion vriety ws Monterrey lmond in oth fumigtion loks. Rootstok emergene ws reorded on April 17, 2007, nd the numer of suessfully udded trees ws reorded on Deemer 6, injury nd redued rop ompetition, weed ontrol ws poorer thn expeted with PRE flumioxzin, rimsulfuron, nd sulfentrzone y the end of the growing seson (dt not shown, rop injury disussed elow). The Yu City, CA, lotion, whih hd een long-term nut orhrd until 2004 nd hd two winter whet (Tritium estivum L.) rops grown efore this nursery rop, hd sustntilly higher weed popultions thn the Hikmn, CA, site (Tle 2). In Deemer 2006, efore rop emergene, the primry weeds in the unfumigted re were volunteer whet, nnul ryegrss (Lolium multiflorum Lm), nd low popultions of winter-nnul rodlef weeds, inluding ommon hikweed, nnul sowthistle, nd horseweed (Conyz ndensis L). No differenes in weed popultions were oserved in the unfumigted trped vs. untrped plots. The two fumigted loks hd primrily Cliforni urlover, ommon mllow, nd some nnul grsses emerging y erly Jnury. In mid- Jnury, the ooperting nursery overspryed the tril with glyphoste to ontrol emerged weeds efore rootstok emergene. A weed ount on April 17, 2007 (5 mo fter PRE tretment), indited tht most PRE tretments, exept for prodimine nd rimsulfuron, inresed weed ontrol over fumigtion nd rodst glyphoste lone. Interestingly oryzlin, grower stndrd, did not redue urlover popultions t the 1.12 kg/h rte tested; however, higher rtes used y the grower, outside of the experimentl re, provided etter suppression of this nd other weeds (dt not shown). After April, the nursery ultivted nd hnd-weeded the tril long with the surrounding field, nd no further detiled weed ounts were onduted. Crop sfety is of prmount importne in nursery tree prodution euse stunting or visul root defets ould sustntilly redue the numer or vlue of slele trees t hrvest. Sustntil injury to the emerging rootstok ws oserved with severl tretments t the Hikmn, CA, lotion efore thinning (Tle 3). PRE flumioxzin, rimsulfuron, nd sulfentrzone redued rootstok emergene in oth fumigtion loks, wheres isoxen redued emergene only in the 1,3-D lok. PRE oryzlin, dithiopyr, nd prodimine did not injure the emerging peh seedlings. Flumioxzin nd sulfentrzone severely injured the peh rootstok s the oleoptile rehed the soil surfe; however, lmond grown on hrdwood plum uttings in relted nursery experiment did not hve the sme injury with these heriides, likely euse the shoot did not hve to emerge through the treted zone (B. D. Hnson, unpulished dt). Beuse of the high rootstok mortlity, the numer of suessfully udded trees ws redued y ll PRE flumioxzin, rimsulfuron, nd sulfentrzone tretments; however, fter the preudding thinning opertion, the isoxen tretment in the 1,3-D lok ws no longer different from the ontrol. At the Yu City, CA, lotion, rootstok emergene ws somewht vrile mong tretments, nd no differenes were oserved (Tle 3). However, sustntil stunting of the rootstok ws oserved with severl tretments, whih diretly ffeted the numer of suessfully udded trees in plots treted with PRE flumioxzin, rimsulfuron, nd sulfentrzone in most ses. There were differenes in tree-size lss distriution ner hrvest; however, t the Hikmn, CA, site, this ws primrily 496 N Weed Tehnology 22, July Septemer 2008

5 Tle 4. Effet of heriide nd fumigtion tretments on tree-size lss distriution on Novemer 16, 2007, efore hrvest in stone-fruit nursery field tril ner Hikmn, CA, in Tretment 6.4 to 9.4 mm 9.5 to 15.8 mm 15.9 to 25.4 mm No. Heriide Rte Timing MeBr 1,3-D MeBr 1,3-D MeBr 1,3-D kg i/h No No-heriide Oryzlin 1.12 PRE Prodimine 1.12 PRE Isoxen 1.12 PRE Flumioxzin 0.14 PRE Flumioxzin 0.28 PRE Rimsulfuron PRE Dithiopyr 1.12 PRE Sulfentrzone 0.14 PRE Sulfentrzone 0.28 PRE Flumioxzin 0.14 POST-D Flumioxzin 0.28 POST-D Rimsulfuron POST-D Dithiopyr 1.12 POST-D Oryzlin f 1.12 f 0.14 PRE f POST-D flumioxzin LSD (0.05) 2 ns ns Rootstok ws Nemgurd peh in oth fumigtion loks; however, the MeBr lok ws udded to severl peh nd netrine vrieties, wheres the 1,3-D lok ws udded to mixture of lmond ultivrs. Arevitions: No., numer; f, followed y; POST-D, POST-direted; MeBr, methyl romide; 1,3-D, 1,3-dihloropropene, ns, not signifint. Averge numer of trees in eh size lss out of 10 mesured. influened y tree mortlity from rimsulfuron nd sulfentrzone tretments (Tle 4). Interprettion of tree liper dt t the Hikmn, CA, site ws onfounded y the vriety of fruit nd nut ultivrs udded in the tril re. Similr to the Hikmn, CA, site, there were differenes in size lss distriution t the Yu City, CA, site (Tle 5). Generlly, tretments tht redued rootstok emergene or udding suess, lso hd more smll-liper trees t hrvest t Yu City, CA. Although it ould not e tested sttistilly, there ppered to e more smll (6.4- to 9.4-mm-dim) trees in the 1,3-D lok ompred with MeBr, whih tended to hve more lrge (15.9- to 25.4-mm-dim) lmond trees. Although differenes in size lss distriution were often smll, nursery produer ould experiene signifint eonomi effet, depending on sles ontrts nd pries. Current mrket preferene in Cliforni orhrds for lmond plnting stok is Tle 5. Effet of heriide nd fumigtion tretments on tree size lss distriution on Deemer 6, 2007, efore hrvest in n lmond nursery field tril ner Yu City, CA, in Tretment 6.4 to 9.4 mm 9.5 to 15.8 mm 15.9 to 25.4 mm No. Heriide Rte Timing MeBr 1,3-D MeBr 1,3-D MeBr 1,3-D kg i/h No No-heriide Oryzlin 1.12 PRE Prodimine 1.12 PRE Isoxen 1.12 PRE Flumioxzin 0.14 PRE Flumioxzin 0.28 PRE Rimsulfuron PRE Dithiopyr 1.12 PRE Sulfentrzone 0.14 PRE Sulfentrzone 0.28 PRE Flumioxzin 0.14 POST-D Flumioxzin 0.28 POST-D Rimsulfuron POST-D Dithiopyr 1.12 POST-D Oryzlin f 1.12 f 0.14 PRE f POST-D flumioxzin LSD (0.05) ns ns Rootstok ws Nemgurd peh, nd the sion vriety ws Monterey lmond in oth fumigtion loks. Arevitions: No., numer; f, followed y; POST-D, POST-direted; MeBr, methyl romide; 1,3-D, 1,3-dihloropropene, ns, not signifint. Averge numer of trees in eh size lss out of 10 mesured. Hnson nd Shneider: Tree nursery heriide sreening N 497

6 for trees with to 19-m liper mesurement (R. Woolley, personl ommunition). Overll, weed ontrol in these two trils ws not sustntilly different etween the loks fumigted with 392 kg/h MeBr or 372 kg/h 1,3-D. Severl PRE heriide tretments, following either preplnt fumignt, provided signifint erly seson weed ontrol in stone-fruit nursery trees, lthough rop sfety ws not lwys dequte. At oth lotions, with either reltively low or high weed popultions, weed ontrol ws improved with PRE oryzlin, isoxen, nd dithiopyr, ompred with fumigtion nd tillge lone. In generl, POST-D tretments lone were not s effetive s PRE tretments, lthough the former were muh sfer for the emerging rootstok. Additionl reserh is needed on hemils or pplition tehniques to provide sfe, eonomil ontrol of weeds, suh s urlover, mllow, nd redstem filree, whih n espe fumigtion nd mny PRE heriides. Although the POST-D nd omintion tretments in these trils were not s effetive s expeted, it is likely tht omintion pproh with preplnt fumigtion, PRE heriides, nd POST-D tretments n inrese weed ontrol nd provide eonomi svings to nursery tree produers. Aknowledgments The uthors wish to thnk Dve Wilson Nursery nd Sierr Gold Nurseries for their dontion of field spe, plnting stok, nd rop mngement in these trils, nd the Fruit Tree, Nut Tree, nd Grpevine Improvement Advisory Bord for funding. TriCl In. nd Dow AgroSienes re grtefully knowledged for dontions of fumignts nd fumigtion servies. This rtile is U.S. government work nd is in the puli domin in the United Sttes of Ameri. Mention of trdemrk, proprietry produt, or vendor does not onstitute gurntee or wrrnty of the produt y the U.S. Deprtment of Agriulture nd does not imply its pprovl to the exlusion of other produts or vendors tht lso my e suitle. Literture Cited Atlnd, J. E., C. H. Gillim, nd G. Wehtje Weed ontrol in field nurseries. HortTehnology 13:9 14. [CDFA] Cliforni Deprtment of Food nd Agriulture Approved tretment nd hndling proedures to ensure ginst nemtode pest infesttion of nursery stok. Pges 1 19 in Nursery Inspetion Proedures Mnul. Item 7. Srmento, CA: Plnt Helth nd Pest Prevention Servies. Duniwy, J. M Sttus of hemil lterntives to methyl romide for preplnt fumigtion of soil. Phytopthology 92: Gillim, C. H., G. Wehtje, J. E. Eson, T. J. Hiks, nd D. C. Fre Weed ontrol with Gllery nd other heriides in field-grown nursery rops. J. Environ. Horti. 7: Hnson, B. nd A. Shresth Weed ontrol with methyl romide lterntives. CAB Rev. Perspet. Agri. Vet. Si. Nutr. Nt. Resour. 1(63): [NASS] Ntionl Agriulturl Sttistis Servie Nursery Crops 2006 Summry. Aessed: Jnury 10, [NASS] Ntionl Agriulturl Sttistis Servie Nonitrus Fruits nd Nuts 2006 Summry. Aessed: Jnury 10, Norton, J. A A review of methyl romide lterntives evluted y IR-4. Pges 33-1 to 33-2 in G. L. Oenuf, ed. Proeedings of the Annul Interntionl Reserh Conferene on Methyl Bromide Alterntives nd Emissions Redutions. Fresno, CA: Methyl Bromide Alterntives Outreh. Shneider, S. M., E. N. Rosskopf, J. G. Leesh, D. O. Chellemi, C. T. Bull, nd M. Mzzol United Sttes Deprtment of Agriulture Agriulturl Reserh Servie reserh on lterntives to methyl romide: pre-plnt nd post-hrvest. Pest Mng. Si. 59: Shresth, A., G. T. Browne, B. D. Lmpinen, S. Shneider, L. Simon, nd T. Trout Perennil rop nurseries treted with methyl romide nd lterntive fumignts: Effets on weed seed viility, weed densities, nd time required for hnd weeding. Weed Tehnol. 22: [UNEP] United Ntions Environment Progrmme The Montrel Protool on sustnes tht deplete the ozone lyer s either djusted nd/or mended in London 1990, Copenhgen 1992, Vienn 1995, Montrel 1997, Beijing Niroi, Keny: Ozone Seretrit. pdfs/montrel-protool2000.pdf. Aessed: Jnury 10, Willoughy, I., R. L. Jinks, nd V. Stokes The tolerne of newly emerged rodleved tree seedlings to the heriides lopyrlid, yloxydim, nd metzhlor. Forestry 79: Zheljzkov, V. D., K. Ptterson, K. J. Prsons, nd G. Smpson Tolerne of re-root ornmentl perennils to seleted heriides. Cn. J. Plnt Si. 87: Reeived Ferury 15, 2008, nd pproved April 30, N Weed Tehnology 22, July Septemer 2008