Phosphites efficcy, residues nd recommend5ons Clive H. Bock nd Tim B. Brennemn USDA- ARS Southest Fruit nd Tree Nut Reserch Lortory, Byron, GA, University of Georgi, Ti@on, GA O - O P H OH Phosphite ion H 2 PO 3 -
Wht is phosphite? Phosphites (H 2 PO 3- ) re slts of phosphorous cid [HPO(OH) 2 ] Not phosphte (HPO 4 2- ), which re importnt in plnt nutrifon The phosphite ion (H 2 PO 3- ) is redily sored in plnts Phosphite trvels systemiclly in oth the xylem nd phloem Formulted with cfon (most oken n lkli metl, N, K, Al, NH 4 ) nd is sold oth in fungicide nd nutrifonl pckges for use in griculture O - O P H OH Phosphite ion H 2 PO 3 -
Clims of nutrifonl enefits of phosphites should e pproched with cufon No evidence for direct enefit of phosphites to crop helth (no studies performed on pecn to dte) But dt demonstrfng no or dverse effects exists from other crops: If phosphte is dequte, ddifonl phosphte or phosphite hs no effect If plnts re phosphte deficient, ddifonl phosphte enefits dry mver ccumulfon, ut phosphite retrds it Effects of phosphite tretments on shoot fresh weight of hydroponic levuce under different phosphte supplies The phosphte levels.5,.1,.15 nd.3 mmol L 1 were phosphte supplies for 5, 8, 9 nd 1% of mximum plnt growth, respecfvely. Error rs re stndrd error (n = 3). ***P <.1. Different levers indicte significnt differences etween mens within the sme phosphte supply y lest significnt difference tests (P <.5). Tho nd Ymkw, 21 SchroeVer, S, Angeles- Wedler, D, Kreuzig, R nd Schnug, E. 26. Effects of phosphite on phosphorus supply nd growth of corn (Ze mys). Lnduforschu Volk., 3/4, 56: 87 99. H. T. B. Tho nd T. Ymkw. 21. Phosphite (phosphorous cid): Fungicide, ferflizer or io- sfmultor? Soil Science nd Plnt NutriFon Vol. 55: 228-234.
Mode of cfon 1 - Direct toxicity to fungus: demonstrted tht it is directly toxic to mny pthogens t the rtes pplied in the field (ut does not explin the full level of control witnessed in field situfons) 2 - Phosphites hve een demonstrted to enhnce the plnts nturl defense through mechnism clled systemiclly cquired resistnce (SAR) SAR re rod- spectrum plnt defense responses tht cn e induced iologiclly y chllenging plnt with n Venuted pthogen or chemicl Fungl mss (g) The effect of phosphite (P) nd triphenylfn hydroxide (T) on growth of Venturi effus in- vitro..7.6.5.4.3.2.1 Tretment The fungus ws grown in potto dextrose roth mended with ProPhyt (.i. phosphite) or Super Tin 4L (.i. TPTH) t different concentrfons:,.5x,.25x,.5x, 1x, 2x s the fctor of the recommended rte of the fungicide where 1x = 2.64 L 1 L - 1 for ProPhyt nd.9 L 1 L - 1 for Super Tin 4L. Mens comprisons re sed on Tukey s test: numers with different lever re significntly different (P=.5). Bock, C.H., Brennemn, T.B., Hotchkiss, M.W. nd Wood, B.W. EvluFon of phosphite fungicide to control pecn sc in the southestern USA. Crop ProtecFon 36: 58-64. 212. Loto, M.C., Mchinndiren, M.F., Tmscio, C., Dosio, G.A.A., Cldiz, D.O., Dleo, G.R., et l. 211. Effect of folir pplicfons of phosphite on post- hrvest potto tuers. Eur J Plnt Pthol 3: 155 163
Control of pecn sc with phosphites Pecn sc, cused y Venturi effus is the most importnt disese of pecn Severl fungicides re used to mnge the disese, including orgnofns, DMIs, MBCs, QoIs nd Zirm (unfortuntely resistnce to some of these is relity) Recently, phosphites were demonstrted to provide good control of pecn sc
Phosphites re effecfve fungicides ginst Sc severity (percent re infected).9.6.3. Control (untreted) pecn sc on folige In mulfple experiments cross the Southest, phosphites hve een shown to effecfvely reduce sc on folige when compred to other industry stndrd fungicides Byron, GA, 29 Byron, GA, 21 2.5 Phosphite TPTH Sc severity (percent re infected) 2. 1.5 1..5. Control (untreted) Phosphite TPTH Fungicide tretments: Potssium phosphite (Prophyt, 36 fl oz/1 gllons) or triphnyl Fn hydroxide (TPTH) (Super Tin 4L, 12 fl oz/1 gllons). ApplicFons mde iweekly. PrepollinFon - end of July Sc severity ssessed visully on folige. Dt ws nlyzed using Generl liner modeling with Tukey s mens seprfon (P =.5) Bock, C.H., Brennemn, T.B., Hotchkiss, M.W. nd Wood, B.W. EvluFon of phosphite fungicide to control pecn sc in the southestern USA. Crop ProtecFon 36: 58-64. 212.
Sc severity (percent re infected) Phosphites re effecfve fungicides ginst pecn sc on folige Further studies demonstrfng efficcy on folige: 12 1 8 6 4 2 y Control TiKon, GA, 21 ProPhyt (1X) z z z ProPhyt (2X) Wichit Cherokee Super Tin 4L Sc severity (percent re infected) 3 25 2 15 1 5 Rymond, MS, 21 Untreted Control Orit 4 oz (1-5) Prophyt 2.5 LBG- 61 2 pt pt (1-5) (1-5) Sc severity (re under the disese progress curve) 6 5 4 3 2 1 SFllwter, OK, 21 Fungicide tretments (6 pplicfons): Potssium phosphite (Prophyt, 36 fl oz/ 1 gllons) or triphnyl Fn hydroxide (TPTH) (Super Tin 4L, 12 fl oz/1 gllons). ApplicFons mde iweekly. PrepollinFon - end of July Sc severity ssessed visully on folige. Dt ws nlyzed using Generl liner modeling with Tukey s mens seprfon (P =.5) Bock, C.H., Brennemn, T.B., Hotchkiss, M.W. nd Wood, B.W. 212. EvluFon of phosphite fungicide to control pecn sc in the southestern USA. Crop ProtecFon 36: 58-64. 212. Fungicide tretments (5 pplicfons): Orit 4 oz (1-5), Prophyt 2.5 pt (1-5), LBG- 61 2 pt (1-5) Sc severity ssessed visully. Dt ws nlyzed using ANOVA with mens seprfon n LSD test (P =.5). Ingrm, D.M. 211 EvluFon of products for control of sc in pecns, 21. Plnt Disese Mngement Reports 5:STF7 Fungicide tretments (6 pplicfons): NTC = Non- treted control. LBG- 61: 1 = Quilt 1.66SC 27.5 oz, 2-5 = LBG- 61 F 32. oz, 6 = Enle 2F 8. oz Prophyt: 1 = Quilt 1.66SC 27.5 oz, 2-5 = ProPhyt F 4. oz, 6 = ProPhyt F 4. oz + Elst 4F 25. oz Lte stroiliurin: 1 = Folicur 3.6F 8. oz, 2, 4 = Enle 2F 8. oz, 3, 6 = Topsin 4.5FL 2. oz, 5 = Hedline 2.9EC 7. oz Strtego: 1,3,5 = Strtego 2.8EC 1. oz, 2,4,6 = Topsin 4.5FL 2. oz Erly stroiliurin: 1, 5 = Hedline 2.9 EC 7. oz, 2, 4 = Topsin 4.5FL 2. oz, 3 = Aound 2.8EC 12.3 oz, 6 = Enle 2F 8. oz Quilt: 1,3,5 = Quilt 1.66SC 27.5 oz, 2,4,6 = Topsin 4.5FL 2. oz Sc severity ssessed visully. Dt ws nlyzed using ANOVA with mens seprfon using Fishers protected LSD test (P =.5). Smith, D.L., Pyne, A.F. nd Moore, J.W. 211 EvluFon of convenfonl fungicde progrms nd new fungicde formulfons for control of pecn sc in Oklhom, 21. Plnt Disese Mngement Reports 5:STF7.
Phosphites re effecfve fungicides ginst pecn sc on developing fruit In mulfple experiments cross the Southest, phosphites hve een shown to effecfvely reduce sc on fruit when compred to other industry stndrd fungicides Sc severity (percent re infected) 1 8 6 4 2 Control (untreted) Byron, GA, 29 Byron, GA, 21 8 Phosphite 5- Aug- 9 21- Sep- 9 TPTH Sc severity (percent re infected) 6 4 2 Control (untreted) Phosphite 7- Jul- 1 15- Oct- 1 TPTH Phosphite nd TPTH pplied to Apche, Desirle nd Wichit Rndomized complete lock design. Non- treted control, potssium phosphite (Prophyt, 36 fl oz/1 gllons) or TPTH (Super Tin 4L, 12 fl oz/1 gllons). ApplicFons mde iweekly. PrepollinFon - end of July Sc severity ssessed visully twice on fruit Dt ws nlyzed using Generl liner modeling with Tukey s mens seprfon (P =.5) Bock, C.H., Brennemn, T.B., Hotchkiss, M.W. nd Wood, B.W. 212. EvluFon of phosphite fungicide to control pecn sc in the southestern USA. Crop ProtecFon 36: 58-64. 212.
Phosphites re effecfve fungicides ginst pecn sc on developing fruit Further studies demonstrfng efficcy on fruit: Sc severity (percent re infected) 1 8 6 4 2 x TiKon, GA, 21 Rymond, MS, 21 SFllwter, OK, 21 y z Wichit Cherokee yz Sc severity (percent re infected) 1 8 6 4 2 c c Sc severity (percent re infected) 25 2 15 1 5 c cd cd cd d Control ProPhyt (1X) ProPhyt (2X) Super Tin 4L Untreted Control Orit 4 oz (1-5) Prophyt 2.5 pt (1-5) LBG- 61 2 pt (1-5) Fungicide tretments (6 pplicfons): Potssium phosphite (Prophyt, 36 fl oz/ 1 gllons) or triphnyl Fn hydroxide (TPTH) (Super Tin 4L, 12 fl oz/1 gllons). ApplicFons mde iweekly. Sc severity ssessed visully. Dt ws nlyzed using Generl liner modeling with Tukey s mens seprfon (P =.5) Bock, C.H., Brennemn, T.B., Hotchkiss, M.W. nd Wood, B.W. 212. EvluFon of phosphite fungicide to control pecn sc in the southestern USA. Crop ProtecFon 36: 58-64. 212. Fungicide tretments (5 pplicfons): Orit 4 oz (1-5), Prophyt 2.5 pt (1-5), LBG- 61 2 pt (1-5) Sc severity ssessed visully. Dt ws nlyzed using ANOVA with mens seprfon n LSD test (P =.5). Ingrm, D.M. 211 EvluFon of products for control of sc in pecns, 21. Plnt Disese Mngement Reports 5:STF7 Fungicide tretments (6 pplicfons): NTC = Non- treted control. LBG- 61: 1 = Quilt 1.66SC 27.5 oz, 2-5 = LBG- 61 F 32. oz, 6 = Enle 2F 8. oz Prophyt: 1 = Quilt 1.66SC 27.5 oz, 2-5 = ProPhyt F 4. oz, 6 = ProPhyt F 4. oz + Elst 4F 25. oz Lte stroiliurin: 1 = Folicur 3.6F 8. oz, 2, 4 = Enle 2F 8. oz, 3, 6 = Topsin 4.5FL 2. oz, 5 = Hedline 2.9EC 7. oz Strtego: 1,3,5 = Strtego 2.8EC 1. oz, 2,4,6 = Topsin 4.5FL 2. oz Erly stroiliurin: 1, 5 = Hedline 2.9 EC 7. oz, 2, 4 = Topsin 4.5FL 2. oz, 3 = Aound 2.8EC 12.3 oz, 6 = Enle 2F 8. oz Quilt: 1,3,5 = Quilt 1.66SC 27.5 oz, 2,4,6 = Topsin 4.5FL 2. oz Sc severity ssessed visully. Dt ws nlyzed using ANOVA with mens seprfon using Fishers protected LSD test (P =.5) Smith, D.L., Pyne, A.F. nd Moore, J.W. 211 EvluFon of convenfonl fungicde progrms nd new fungicde formulfons for control of pecn sc in Oklhom, 21. Plnt Disese Mngement Reports 5:STF7.
Phosphite usge: recommendfons Phosphites re pplied s oth single pplicfon tretments nd tnk mixes There is much informfon we do not hve, ut current usge recommendfons re: PrepollintFon pplicfons (every 1-14 dys from ud- rek to nut- set) PostpollintFon pplicfons (every 1-21 dys from nut- set to shell hrdening) Wells, M. L. 217 Commercil Pecn Spry Guide. University of Georgi Extension. UGA Extension BulleFn 841.
Rtes of phosphites pper to impct efficcy Compred low nd high recommended rtes of different phosphites Results showed tht in most cses the low rte provided either significntly or numericlly less good control of sc (even with low disese pressure) Thus it is importnt when using phosphites to use t lest the lelled rte Sc severity (percent re infected) 12. 1. 8. 6. 4. 2. Lo Hi Lo Hi Lo Hi Lo Mid Hi Lo Mid Hi 12. Lo Hi Lo Hi Lo Hi Lo Mid Hi Lo Mid Hi 1. c c 8. c c d Byron, GA, 215 (August) cd d cd cd cd cd d d 16. 14. 6. 4. 2. c Byron, GA, 216 (Octoer) 5 pplicfons 6 pplicfons Sc severity (percent re infected) c c c c c c.. Product nd rte Product nd rte Rtes nd other detils s follows for ech fungicide sed on lel recommended rtes: Fungicide/nutriFonl, ProporFon of mono- nd di- potssium phosphite slts, Weight Kg/L (equivlent phosphourous cid), Recommended rte (lel) Rte (Liter/ h, Pints/ cre), Rte designfon in study: Control,.%,. (.),.,.,.,.; K- phite 7LP, 56.%,.84 (.53), 2.35-7.2, 2.22, 1.9, Lo; 7.1, 6., Hi; Phostrol, 53.6%,.75 (.5), 2.35-5.86, 2.35, 2., Lo; 5.86, 5., Hi; Relint, 45.8%,.62 (.4), 4.67, 2.94, 2.5, Lo; 4.67, 4., Hi; Fungi- Phite, 45.5%,.65 (.41), 2.35-3.51, 2.35, 2., Lo; 2.91, 2.5, Mid; 3.51, 3., Hi; ProPhyt, 54.5%, - c (.5), 2.35-5.86, 2.35, 2., Lo; 3.51, 3., Mid; 5.26, 4.5 d, Hi; 7.1, 6., Hi+1.75L; Nutri- Phite,.58-4.68, 4.68, 4., Hi
Effect of Medium Rte (64 z) Phosphite Sprys on Nut Sc (Desirle, Men of 2 Different Trils for Ech Phosphite) Low/mid rtes of phosphite cn e efficcious nd reduce disese 1 % Sc 8 6 4 2 Nontreted Tin 6 oz + Elst 25 oz, Sprys 1-1 Phosphite 64 oz lt w/ Tin + Elst Rmprt Kphyte Tim Brennemn, UGA Tifton 96 fl oz of Rmprt is the mximum lelled rte for this phosphite product
Effect of High Rte (96 oz) Phosphite Sprys on Lef nd Nut Sc (Desirle, Men of 3 trils, 214-216) But high rtes of phosphite re s good s or ever when compred to n industry stndrd (Tin/Elst) 1 % Sc 8 6 4 2 Nontreted Tin 6 oz + Elst 25 oz, Sprys 1-1 Rmprt 96 oz / lt Tin + Elst Leves Nuts Tim Brennemn, UGA Tifton 96 fl oz of Rmprt is the mximum lelled rte for this phosphite product
How re phosphites used in the pecn industry? Most lels stte tht there is no limit to the numer of pplicfons pplied per seson, lthough some lels do specify minimum volumes nd lso minimum Fme periods efore repplying the product Some growers do not use phosphites But mny growers pply from one to s mny s 1 sprys of phosphite per seson (either s single sprys, tnk mixes, or cominfon oken t ~1Q rte) Frequency of orchrds spryed 7 6 5 4 3 2 1 Frequency of numer of sprys of phosphite pplied (dt from seven different growers sprying 2 orchrds) 1 2 3 4 5 6 7 8 9 1 Numer of sprys pplied Orchrd Totl sprys Numer tht contin phosphite 1 12 4 25% 2 12 7 58% 3 14 6 43% 4 14 % 5 13 1 8% 6 13 % 7 24 8 33% 8 16 1 63% 9 15 9 6% % of sprys with phosphite
Advntges/disdvntges of phosphites They hve low toxicity. The EPA hs four toxicity rfngs. Phosphite slts fell into ctegories III nd IV, depending on toxicity test (orl, derml, inhlfon, oculr). ( hvps://www3.ep.gov/pesfcides/chem_serch/reg_cfons/registrfon/fs_pc- 76416_1- Oct- 98.pdf) Toxicity ctegory III is slightly toxic nd slightly irritfng Toxicity ctegory IV is prcfclly non- toxic nd not n irritnt Apprently not hrmful to the environment (used in Austrli to control disese of Euclyptus forests Jrrh ) They re effecfve fungicides/oomyfcides Cses of field resistnce to phosphites re rre Bremi lctuce (levuce downy mildew ) in CA nd Phytophthor cinnmomi (Jrrh dieck) in Austrli, oth oomycetes (repeted use of phosphite- contining fungicides/ferflizers will increse risk) They might cuse phosphite- induced phosphorous deficiency They hve potenfl to e phytotoxic (lso reports of delyed shuck- split) Phosphite pplicfon cn result in residues in hrvested crop products (such s pecn nutmets) Brown S, Koike ST, Ocho OE, Lemmlen F, Michelmore RW, 24. InsensiFvity to the fungicide fosetyl- luminum in Cliforni isoltes of the levuce downy mildew pthogen, Bremi lctuce. Plnt Disese 88, 52 8. Dorowolski, M. P., Sherer, B. L., Colquhoun, I. J., O Brien, P. A. nd Hrdy, G. E. StJ. (28), SelecFon for decresed sensifvity to phosphite in Phytophthor cinnmomi with prolonged use of fungicide. Plnt Pthology, 57: 928 936.
Residues, MRLs, EU rulings nd other nut crops in relfon to pecn In 213 the EU chnged the designfon of phosphites s oth ferflizer nd pesfcide to only pesfcide, thus defulfng phosphites to 2 ppm MRL They provided temporry MRL of 75 ppm to nut nd other crops to 31 Decemer 215 to llow Fme for producer industries to respond In Septemer 215, the US tree nut industry sumived pckge sed on IR- 4 phosphite residue tesfng (which did not include pecn dt) for the EU to determine finl import tolernce to replce the temporry MRL FINAL RESIDUE REPORTS FOR OTHER NUT CROPS WERE PROVIDED TO THOSE WHO WILL SUBMIT TO THE EU; IR- 4 WORK IS COMPLETED, AND PECANS ARE COVERED: 7/16 The temporry MRL ws extended on other nut cops (which does not stte pecn) unfl 1 Mrch 219 (when the permennt MRL must e decided) In the menfme the MRL for pecn hs defulted to 2 ppm Also, phosphite use on pecn (from TX to GA) is different to other nut crops Thus it hs ecome expedient to otin temporry MRL for pecn to llow exports to the EU (vlued t US $138,314,) We need to otin some residue dt for pecn to chieve this gol
Exports of pecns to the EU Vlule export mrket Incresing in size s mrket for pecns $16,, $14,, Vlue of export (ll pecns) $12,, $1,, $8,, $6,, $4,, $2,, hvps://pps.fs.usd.gov/gts/defult.spx $ 211 212 213 214 215 216 Yer
Method used to test for residues of phosphite y the EU Quick method for the nlysis of numerous highly polr pesfcides (QuPPe- method) Liquid Chromtogrphy coupled with Mss Spectroscopy A 68- pge methods descripfon is ville ( hvp://www.eurl- pesfcides.eu/userfiles/file/eurlsrm/meth_quppe- PO_EurlSRM.pdf) Accurte tesfng for phosphites is not trivil Specilized equipment is required, it is expensive nd only few ls hve it Highly trined nd skilled personnel re needed to operte the equipment Commercilly, ech smple costs ~US$ 25 O - The following dt is sed on tests performed y commercil lortories using the recommnded methods Preliminry smples of nuts collected in the fll of 215 in TiKon nd Byron, GA O P H OH Phosphite ion H 2 PO 3 -
Residues detected in smples of pecn Smples from 215 Test Loc5on Product Exposure rte nd numer of pplic5ons Totl exposure EUROFIN Totl detected (mg/kg) 1 TiKon 1 pts, x pt Not detected - Byron 1 pts, x pt 7.9 - Alny 1 Phostrol 2 pts, 3 x 6 pt 44.5 - Byron 1 Prophyt 2 pts, 5 x 1 pt 15.8 - TiKon 1 Prophyt 4 pts, 5 x 2 pt 78.6 - TiKon 1 Rmprt 6 pts, 5 x 3 pt 296. - UC Dvis Totl detected (mg/kg) 2 Byron 1 pts, x pt - 5.7 Byron 1 Prophyt 4.5 pts, 5 x 22.5 pt - 18. Byron 1 Prophyt 6 pts, 5 x 3 pt - 8.6 Not tested Most progrms hd >2 ppm Some hd >75 ppm Even some pecn crops receiving no phosphite hd detectle residue
RelFonship etween totl numer of pints of phosphite pplied nd phosphite residue Phosphorous cid residue (ppm) 25 2 15 1 5 y = 4.7x - 3.2 R² =.69 Smples from 215 Permnent MRL TBA???? Temporry MRL ws 75 ppm 1 2 3 4 Numer of pints phosphite product Defult MRL for pecn is 2 ppm A liner relfonship ws oserved etween totl numer of pints of phosphite pplied nd phosphite residue Bsed on preliminry dt
Sttus of knowledge Phosphite residues re redily detectle in pecn (t levels >75 ppm) There is no directly trnsferrle informfon from other crops, nd we don t know if the nut- crop group MRL will e relisfc for pecns Even when nut group MRL is grnted, use of phosphites will need to e mnged to ensure residues <MRL (spry frequency, Fming etc) Phosphites re vitl chemistry for the industry The pecn industry is currently pursuing temporry MRL, which is eing sperheded y Dr. Rndy Hudson nd Dr. Tim Brennemn. nd recent reserch nd results In 216, smples (~3) were otined from growers orchrds to provide se- line dt on residue levels (Drs. Rohl (Nole FoundFon, Ardmore), Brennemn (University of Georgi, TiKon), nd Bock (USDA- ARS- SEFTNRL, Byron)) (APC support) The smples will e processed nd phosphite levels determined using the pproprite methods. The Nole FoundFon is instrumentl in this tsk Field experiments (216 nd onwrds) re eing designed to invesfgte effects of different usge pverns on residues s sis for recommendfons Dt will e compiled nd interpreted y the reserchers, nd provided to the industry for pproching the EU, nd possily IR- 4 for further tests if required
Preliminry results of phosphite residue tesfng in relfon to numer nd Fming of sprys - 216 Experiment t ARS- SEFTNRL, Byron, GA, in 216, cv. Pwnee Applied Prophyt (3 pt/1 G/cre) following two different protocols i) 1 to 5 pplicfons ddifvely (1, 2, 3, 4 or 5 sprys) No spry 15- Jul (1 spry) 15, 28- Jul (2 sprys) 15, 28- Jul, 15- Aug (3 sprys) 15, 28- Jul, 15, 3- Aug (4 sprys) 15, 28- Jul, 15, 3- Aug, 9- Sep (5 sprys) ii) 1 spry pplied t ech of 5 spry dtes (only 1 pplicfon, ut on different dtes) No spry 15- Jul (1 spry) 28- Jul (1 spry) 15- Aug (1 spry) 3- Aug (1 spry) 9- Sep (1 spry) Only two trees of ech tretment so sed on limited dt
Phosphorous cid residue (ppm) Preliminry results of phosphite residues in relfon to numer nd Fming of sprys Profound effects of numer of sprys nd spry Fming on the residue levels of phosphite A. There ws n lmost ddi5ve increse in phosphite residue with ech spry B. Lter sprys pplic5ons resulted in greter residue Even the control exceeded the EU MRL of 2 ppm A. MulFple sprys B. 1 9 8 7 6 5 4 3 2 1 Tree 1 Tree 2 75 ppm 2 ppm 1 8 6 4 2 15- Jul y = 17.1x - 4.6 R² =.95 1 2 3 4 5 Numer of sprys 15, 28- Jul 15, 28- Jul, 15- Aug 15, 28- Jul, 15, 3- Aug 15, 28- Jul, 15, 3- Aug, 9- Sep Dtes of pplicfon 1 9 8 7 6 5 4 3 2 1 Tree 1 Tree 2 75 ppm 2 ppm 4 3 2 1 15- Jul y =.45x - 8.6 R² =.94 19 21 23 25 Dy of the yer 28- Jul Single sprys 15- Aug Dte of pplicfon 3- Aug 9- Sep
Conclusions Phosphites re efficcious ginst sc on folige nd lso fruit (nd hve low risk of resistnce) they re vlule to the industry Any pplicfon of phosphite will exceed 2 ppm. Just few sprys cn result in >75 ppm As long s the 2 ppm ruling is in plce, growers choosing to export to the EU should void using phosphites Even if nut group MRL is grnted, use of phosphites will need to e mnged in mnner to ensure EU- ound nuts hve residues tht do not exceed this vlue Phosphite spry Fming nd frequency used y growers will e crifcl, nd dependent on the finl MRL rffied y the EU We need to determine: How spry frequency/concentrfon/fming ffects phosphite residue in nuts Whether there is seson to seson crry over of phosphites in pecn trees (could ecome cumulfve over yers) CulFvr/environment effects
Acknowledgements We thnk Dr. Mike Hotchkiss, Wnd Evns, Sue Burrell, Json Shipp, Kylee Crlson, Meliss Steinhuer, Emm Cutchens, Keith Hough, Tucker Ellis, nd Shd Stormnt t the USDA- ARS for technicl ssistnce with smpling, ssessments nd processing We re grteful to severl growers for providing informfon on spry pplicfons Funding from the GA Commodity Commission for Pecns contriuted to some of the reserch results descried. The Americn Pecn Council is providing funds for residue tesfng We lso pprecite mnufcturers of vrious phophite products for providing mteril for tesfng purposes
QuesFons?