Vegetable Oil Emulsions, NaCl, CH 3 COOH and CaS x as Organically Acceptable Apple Blossom Thinning Compounds

Transcription

1 Europ.J.Hort.Si., 73 (2). S , 2008, ISSN Verlg Eugen Ulmer KG, Stuttgrt Vegetle Oil Emulsions, NCl, CH 3 COOH n CS x s Orgnilly Aeptle Apple Blossom Thinning Compouns M. Stopr (Agriulturl Institute of Sloveni, Ljuljn, Sloveni) Summry Full loom pplition of possile thinning gents for orgni pple growing ws rrie out in fiel experiments on mture Golen Deliious /M.9, Summerre /M.9 n Elstr /M.9 pple trees. Soium hlorie (NCl) 10 g l 1 or 15 g l 1 use light thinning on the ove ultivrs n 20 g l 1 overthinne Elstr. NCl pplitions enhne return loom of Elstr n Golen Deliious. Aeti i (CH 3 COOH) 30 ml l 1 use fruit sheing on Summerre n Elstr. When lime sulphur (CS x ) 30 ml l 1 ws sprye in four trils, no thinning ourre on Summerre, moerte thinning on Golen Deliious (yer 2003) while strong thinning response n inrese return loom ws oserve on Elstr n Golen Deliious (yer 2002). No fruit russeting ws oserve when CH 3 COOH or CS x ws use. Thinning tion of NCl, CH 3 COOH n CS x ws epenent on onentrtion. The pplition of rpe oil or soy oil 30 g l 1 emulsion thinne Golen Deliious n Summerre pples suffiiently, ut with signifint fruit russeting n without etter return loom. When the sme mount of emulsifier (2.4 g l 1 ) s use in rpe oil emulsion 30 g l 1 ws pplie lone, thinning ws inue n lso fruit russeting n phytotoxiity ppere on Summerre. Phytotoxiity oserve fter oil emulsion pplition ppere s lef wrinkling n stunte growth of young shoots. When CH 3 COOH or NCl were sprye phytotoxiity ws expresse mostly s urning of lef eges n prtly s stunte growth of young leves; in the se of CS x smller leves n suppresse growth of young shoots ourre. The phytotoxiity for ll tretments ppere few ys fter sprying, with the severity grient from the highest CH 3 COOH = NCl > CS x > oil emulsions respetively, n then iminishe two month lter. Key wors. Mlus omesti loom thinning fruit qulity orgni orhr mngement Introution After unnt flowering most pple ultivrs will retin hevy set of fruit throughout the growing seson resulting in smll, poorly oloure, low qulity fruit. At the sme time hevy set inhiits flower u inution n iennil ering tkes ple. Chemil fruit thinning effiiently enhnes fruit size, qulity n return loom in ommeril pple fruit proution (WERTHEIM 1997). When loom is hevy n onitions prior to loom re fvourle for fruit set, flower thinners or petl fll thinners re routinely pplie (WILLIAMS n FALLAHI 1999; GREENE 2002). In intensive pple proution where fruit set is usully high, flower thinners re often followe y the post loom thinners when fruitlet size rehes 8 15 mm imeter (WERTHEIM 2000). Reuing fruit set is one of the gretest prolems in orgni pple proution. Sine no syntheti ompouns or growth regultors re llowe in orgnilly grown pples only hn thinning my e use to regulte the rop lo. The prolem of hn thinning is its high lour ost n the effet is limite to etter fruit qulity ut there is little prevention of iennil ering (TROMP 2000; GREENE 2002). Reently, few thinning stuies were me with potentilly eptle orgni ompouns. All teste ompouns were loom thinners n possily se on usti tion, mening they urn stigms n styles to prevent pollintion n result in elerte flower sission (WILLIAMS 1994; FALLAHI n WILLEMSEN 2002). Lime sulphur (lium polysulfie), hemil prout permitte in orgni pple proution uner EU legisltion, is effetive s loom thinning gent on pples (MELAND 1998; BERT- SCHINGER et l. 2000). Minerl oils or vegetle oil emulsions my e use s thinning gents in the orgni proution (JU n DUAN 1991; KELDERER et l. 1998; KALLSEN 2001). JU et l. (2001) report equte thinning of Deliious pple n Feng Hung peh when 30 g l 1 or 50 g l 1 orn oil is pplie etween preloom n 20 % full loom (FB). Bloom pplition of soium hyrogen ironte (10 kg h 1 ), oxli i (20 kg h 1 ) n soium slt (5 15 kg h 1 ) results in high Pinov fruit sheing n severe lef mge, while pplition of lime sulphur (30 l h 1 ) enhnes fruit setting (PFEIFFER n RUESS 2002). Prtil lef nerosis, fruit russeting n fruit eformtion on Deliious, Golen Deliious or Elstr pples ours when rpe oil or sop re pplie s flower thinning gents (STRIMMER et l. 1997). Consiering the thinning effet n fruit qulity in previously pulishe reserh, the effet of pplie usti gents gives vrile results; unfortuntely the return Europ.J.Hort.Si. 2/2008

2 56 Stopr: Orgni pple thinning loom ws not estimte preisely. A three yer stuy ws estlishe to evlute the most promising orgni flower thinning gents relting on thinning, fruit qulity, russeting, phytotoxiity n return loom, for the russeting sensitive Golen Deliious /M.9, Summerre /M.9 n Elstr /M.9 pple trees. Mterils n Methos Soium hlorie (NCl), eti i (CH 3 COOH), lium polysulfie (lime sulphur, CS x ), oil emulsions n extrin thinning stuies In the fiel tril, eight ( Golen Deliious /M.9 in 2002) or ten ( Summerre /M.9 in 2004) yers ol pple trees trine s slener spinle (out 2.5 m high n 1.2 m wie) with ensity of 3000 trees h 1 were selete oring to uniform loom n growth vigor in the spring. Two trils using ompletely rnomize lok esign were estlishe with six ( Golen Deliious ) n eight ( Summerre ) replitions per tretment with single tree per plot. Sprying of oth trils ws one in morning uring full loom in sunny wether with tempertures out 18 C, RH 65 % ( Golen Deliious ) n 19 C, RH 70 % ( Summerre ). The tretments of oth trils were s follows: Control: no thinning, no sprying Hn thin (one just fter the June rop time) NCl 10 gl 1, using kithen slt (99 % pure) issolve in wter NCl 15 gl 1, using kithen slt (99 % pure) issolve in wter CH 3 COOH 10 ml l 1, using eti i (99 % pure) issolve in wter CH 3 COOH 30 ml l 1, using eti i (99 % pure) issolve in wter CS x 30 ml l 1, using lime sulphur 18.5 % (KZ Krk, Novo mesto, Sloveni), i.e. 1.0l of CS x (18.5 %) l wter Rpe oil 10g l 1, using Ogriol (Pinus, Re, Sloveni 92 % rpe oil + 8 % emulsifiers) wter suspension Rpe oil 30 g l 1, using Ogriol wter suspension Sunflower oil 30 g l 1, sunflower oil (96 % sunflower oil + 4 % emulsifiers) wter suspension Soy oil 30 gl 1, soy oil (96 % soy oil + 4 % emulsifiers) wter suspension Dextrin 50 gl 1, extrin (s 100 % strh - prtly hyrolyse) issolve in wter Emulsifiers 2.4 gl 1, only on Summerre tril, the sme emulsifiers n in the sme mount s is e to the rpe oil tretment 30 g l 1 (i.e. 1.2 g l 1 Emulsifier g l 1 Emulsifier OCA 30). Emulsifiers in ommeril rpe oil gent (Ogriol) re the omintion of 4 % (w/w) Emulsifier 100 (Teol, Ljuljn, Sloveni, mixture of non-ioni n nioni tensies) n 4 % (w/w) Emulsifier OCA 30 (Teol, Ljuljn, Sloveni, lkyl (C 16 C 18 ) polyethylene glyol ether). A mixture of sunflower oil, s well s soy oil, with emulsifiers ws me n test of suspension stility ws one to estlish the minimum quntity of emulsifiers neee. Bse on the suspension susistene test 4 % (w/w) mixture of two emulsifiers (Emulsifier 100 (1 %) + Emulsifier OCA 30 (3 %)) with soy n/or sunflower oil ws foun to e equte, i.e. the hlf mount of emulsifiers s prepre in the rpe oil gent Ogriol. Rpe oil Ogriol n CS x re ertifie in Slovene orgni pest mngement progrm whih se on Europen regultion on orgni frming (Counil regultion EEC No 2092/91). Aoring to this regultion nturlly ourring ompouns s CH 3 COOH or NCl, similr s plnt oil ompouns, my e possile to use in orgni mngement in the future. Conentrtion response stuy of CH 3 COOH, CS x n NCl Nine yers ol Golen Deliious /M.9 pple trees, trine s slener spinle (out 2.5 m high n 1.2 m wie), were hosen oring to uniform loom n growth vigor t spring time The experimentl esign ws rnomize lok with eight replitions n single tree per plots. Trees were sprye t full loom, uner prtly louy wether in the morning with tempertures C n RH %. The tretments were s follows: Control (no thinning, no sprying), hn thin (one just fter the June rop time), CH 3 COOH 10 ml l 1, CH 3 COOH 30 ml l 1, CH 3 COOH 50 ml l 1, CS x 10 ml l 1, CS x 30 ml l 1, n CS x 50 ml l 1. The sme hemils were use s esrie previously. In 2004 Elstr /M.9 pple trees were use to stuy the onentrtion effets of CS x, CH 3 COOH n NCl on thinning properties of selete trees. Full flowering seven yers ol slener spinle trees with the uniform vigour (out 3 m high n 1.5 m wie) were selete. A rnomize lok esign with eight replitions n single tree per plot ws use in the fiel tril. Sprys were pplie t full loom on sunny fternoons with tempertures C n RH %. The tretments were s follows: Control (no thinning, no sprying), hn thin (one just fter the June rop time), CH 3 COOH 10 ml l 1, CH 3 COOH 30 ml l 1, CH 3 COOH 50 ml l 1, CS x 10 ml l 1, CS x 30 ml l 1, CS x 50 ml l 1, NCl 10 g l 1, NCl 15 g l 1, n NCl 20 g l 1. The sme hemils were use s esrie previously. Sprying tehnique, phytotoxiity, fruit qulity, return loom estimtion n sttistil nlyses The experiments were onute on mture pple trees, t the experimentl orhr Bro operte y the Agriulturl Institute of Sloveni in ontinentl Sloveni. Sprys were pplie with hn (knpsk) spryer to the point of rip. Aout hlf litre of wter per tree ws use to stisfy the spry retention volume of experimentl trees, exept for Elstr where out 1 l of wter per tree ws neee. During the experiment, the trees reeive stnr pest n isese mngement progrm [integrte proution (IP)]. Phytotoxi effet ws estimte y oserving the whole tree t weekly intervls fter sprying. Estimtion ws fouse on the leves n shoots growth reution n visul mge of leves n flowers (stunte growth of young leves, urning of leves or petls, lef surfe listering or wrinkling) using 1 10 sle, where 1 = no visul mge on the tree, 2 = low phytotoxiity rting (mge iffiult to notie), 3 = injuries re visile (frmers woul estimte it s low importne), 5 = meium phytotoxiity (injuries severe enough to e uneptle for frmers) n 10 = e tree. At mturity the fruits were hrveste, gre into two size lsses ( Golen Deliious n Summerre : Europ.J.Hort.Si. 2/2008

3 Stopr: Orgni pple thinning 57 <68 mm n >68 mm; for Elstr : <70 mm n >70 mm), ounte n weighe. Ten fruits per eh tree (plot) were rnomly smple from the lrger size lss to etermine mturity n inner fruit qulity prmeters (strh-ioine sore, firmness n perent of solule solis, expresse s Brix). Flesh firmness ws mesure y igitl tle penetrometer with 11 mm proe (1 m 2 ), n the perentge of solule solis y hn refrtometer (using juie ollete uring mesurement of flesh firmness). The strh-ioine sore ws mesure y immersing pple hlves into 0.1 M Ioine solution (1 10; 1= highest strh ontent, 10 = no strh present). Fruit russeting ws ssesse y visul 0 10 sle (0 = no russeting present; 5 = 50 % of the fruit surfe is overe y russet; 10 = 100 % of the fruit surfe is overe y russet). Return loom ws ssesse visully the following spring t loom time using the sle 1 10 (1 = no flower lusters present on the trees; 2 = few flowers per tree; 3,4 = not enough flowering; 5,6,7 = meium flower set; 8,9 = hevy flowering; 10 = unnt flowering, snowll ). Dt ws sujete to sttistil nlyses using the sttistil progrm Sttgrphis 5.0 (STSC, Rokville, USA). Anlyses of ovrine were performe when the effets of NCl, CH 3 COOH, CS x, oil emulsions n extrin were lulte. The numer of flower lusters per tree t the initition of the experiments ws use s ovrite. Dunn s multiple rnge test P = 0.05 ws use to seprte the juste mens etween ifferent thinning tretments. For the onentrtion response stuies of CH 3 COOH, CS x or NCl, regression nlysis ws use to evlute the signifine of liner n qurti trens of eh spry. Results NCl, CH 3 COOH, CS x, oil emulsions n extrin thinning stuies The full loom pplition of NCl 10 g l 1 n 15 g l 1 ffete no signifint thinning of Golen Deliious pples Tle 1. Finl fruit numer, men fruit fresh weight n size t hrvest, russeting pperne n return loom of Golen Deliious /M.9 (in 2002) n of Summerre /M.9 (in 2004) pples following vrious thinning tretments. Tretments (g l 1 or ml l 1 ) Fruit numer Fruit numer 100 flower lusters 1 Fruit weight (g) Fruit numer >68 mm Russeting of fruit (0 10) y Return loom (1 10) z Golen Deliious /M.9 in 2002 Control 184 x Hn thin e NCl (10) NCl (15) e CH 3 COOH (10) CH 3 COOH (30) CS x (30) f Rpe oil (10) Rpe oil (30) e Sunflower oil (30) e Soy oil (30) e Dextrin (50) Summerre /M.9 in 2004 Control 105 x Hn thin NCl (10) NCl (15) CH 3 COOH (10) CH 3 COOH (30) CS x (30) Rpe oil (10) Rpe oil (30) e 1.4 Sunflower oil (30) e 1.4 Soy oil (30) Dextrin (50) Emulsifiers (2.4) e 1.7 x Men seprtion within olumn y Dunn s multiple rnge test, P y 0 = no russeting present; 10 = 100 % of fruit is overe y russet t hrvest time. z 1 = no flowering; 10 = unnt flowering of trees next seson. Europ.J.Hort.Si. 2/2008

4 58 Stopr: Orgni pple thinning Estimtion of phytotoxiity (1-10) e Weeks fter pplition Fig. 1. Estimtion of phytotoxiity in weekly intervls of Summerre /M.9 pples following vrious thinning tretments in Estimtion sle 1 10 ws use; 1= no visul sign on the leves, flowers or growth tips, 3 = injuries re visile ut estimte s low importne, 5 = meium phytotoxiity severe enough to e uneptle for growers, 10 = e tree. Letters enote men seprtion within eh te of evlution y Dunn s multiple rnge tests (P 0.05). ontrol NCl 15.0 g l -1 CH3COOH 30.0 ml l -1 CSx 30.0 ml l -1 rpe oil 30.0 g l -1 emulsifiers 2.4 g l -1 ompre with the ontrol (fruit numer, fruit numer 100 flower lusters 1 ), while men fruit weight ws enhne y NCl 15 g l 1 (Tle 1). NCl pplition i not inrese fruit russeting rting ompre to ontrol. NCl 15 g l 1 signifintly improve return loom of Golen Deliious. Also the pplition of NCl 15 g l 1 signifintly thinne Summerre (Tle 1). More russeting ppere in Summerre with NCl 10 g l 1 ut the fruit were still mrketle n oul stisfy ommeril stnrs. The return loom of Summerre trees ws not improve fter NCl pplitions. The CH 3 COOH 10 ml l 1 or 30 ml l 1 tretments h no signifint effet on finl fruit numer, fruit size or russeting of Golen Deliious (Tle 1). On Summerre CH 3 COOH 30 ml l 1 inue thinning ut, like on Golen Deliious, fruit growth or fruit russeting ws unffete (Tle 1). Both ultivrs isplye n insignifint improvement in flowering the next seson fter CH 3 COOH pplitions. CS x 30 ml l 1 use the gretest thinning n return loom on Golen Deliious (Tle 1). The rest of the fruit on the tree were lrger thn 68 mm with essentilly no russeting. When CS x 30 ml l 1 ws pplie to Summerre trees insignifint thinning, fruit growth, russeting or return loom ourre (Tle 1). The pplition of three ifferent oil emulsions 30 g l 1 effetively thinne Golen Deliious trees to the hn thinne level (Tle 1). The rpe oil 10 g l 1 tretment ws not effetive. There ws no thinning effiy ifferene etween rpe oil 30 g l 1, sunflower oil 30 g l 1 or soy oil 30 g l 1 emulsions. Men fruit weights were enhne ut russeting on fruit surfe ws inrese ompre to ontrol pples. Similrly, equte thinning of Summerre pples ourre when rpe oil 30 g l 1 or soy oil 30 g l 1 emulsions were sprye on flowers, while sunflower oil 30 g l 1 emulsion i not thin suffiiently (Tle 1). For oil emulsions fruit growth i not follow the thinning effet suessfully, n, more fruit russeting ppere ut not s severe s on Golen Deliious. Return loom ws not enhne in Golen Deliious or Summerre pple trees y these tretments. Dextrin, prtly hyrolyse strh, h no effet on the thinning properties of Golen Deliious or Summerre pple trees (Tle 1). The pplition of emulsifiers lone 2.4 g l 1 (i.e. in the sme mount s use when ftory-prepre rpe oil emulsion 30 g l 1 ws sprye) thinne Summerre to the sme level s the rpe oil emulsion 10 g l 1 tretment (Tle 1). The fruit were no lrger n reltively strong russet overe the pples. Return loom ws not influene. The phytotoxi severity n reovery time on Summerre pple trees ws estimte t weekly intervls fter sprying the thinning gents (Fig. 1). Aove ll, stunte growth of young leves n urning of lef eges n petls ws estimte s phytotoxi effet of the pplie hemils. The strongest phytotoxi effet ws oserve week fter the pplition of CH 3 COOH 30 ml l 1 n NCl 15 g l 1 n ontinue nerly month fter tht. Six weeks fter sprying, the effet of CH 3 COOH n NCl eme less pronoune; from the growers view proly more eptle ompre to the first month spet. After eleven weeks, phytoxiity ws still oserve; however, trees with this low mge level looke to e generl helthy, with just few stunte leves or rown lef eges oul e seen. A week fter CS x 30 ml l 1 pplition phytotoxiity ws smller ompre with CH 3 COOH 30 ml l 1 n NCl 15 g l 1 tretments. The phytotoxi effet of CS x 30 ml l 1 ws reue to the minimum level seven weeks lter. It shoul e note tht the phytotoxi response on CS x pplitions ws ifferent ompre to CH 3 COOH n NCl tretments. Stunte growth of young leves ws minly oserve on CS x trete rowns while urning of lef eges minly stoo out when CH 3 COOH n NCl ws pplie. Resiues of CS x spry use whitening of leves n oul e oserve more then one month lter, enhning the pperne of phytotoxiity. Also, rpe oil 30 g l 1 tretment inue signifint ut less pronoune phytotoxi effet ompre with CH 3 COOH, NCl or CS x pplition (Fig. 1). Sprying of soy oil 30 g l 1 or sunflower oil 30 g l 1 emulsions resulte in similr phytotoxiity s the pplition of rpe oil 30 g l 1 while extrin h no phytotoxi effet on Summerre trees (t not presente). Phytotoxiity fter oil emulsion pplitions ws expresse s wrinkle lef or stunte growth of leves ut not s urning of lef eges. The pplition of emulsifiers 2.4 g l 1 lone use similr phytotoxi effet s rpe oil 30 g l 1 in the first three weeks fter the pplition. After tht the emulsifier spry erese its phytotoxi effet muh more quikly while lef wrinkling ws still present on rpe oil trete trees for nother two weeks. At lower onentrtions of CH 3 COOH (10 ml l 1 ), NCl (10 g l 1 ) or rpe oil (10 g l 1 ) emulsions pplie on Summerre, phytotoxiity ws hrly notiele ompre to their higher onentrtions (t not shown). Europ.J.Hort.Si. 2/2008

5 Stopr: Orgni pple thinning 59 Conentrtion response n fruit qulity stuy fter CH 3 COOH, CS x n NCl pplition Golen Deliious n Elstr pple trees were use to stuy the effet of high n low onentrtions of eti i, lime sulphur n soium hlorie on phytotoxiity, thinning, fruit growth n return loom. A signifintly negtive liner regression trens etween the CH 3 COOH onentrtions n fruit numer per 100 flower lusters were foun for Golen Deliious (Tle 2) n Elstr pple trees (Tle 3). The men fruit weight ws enhne with inrese CH 3 COOH onentrtions on Golen Deliious (NS) while on Elstr fruit weight inrese ws signifint n rose with thinning intensity. Very ry summer in 2003 inhiite norml Golen Deliious fruit growth n the shre of igger size fruit (>68 mm) ws smll n i not rise signifintly with the thinning effet. No itionl russeting ppere on Golen Deliious n Elstr pples, while the return loom ws signifintly enhne on oth ultivrs when the onentrtions of CH 3 COOH were inresing. The response to inresing onentrtions of CS x on Golen Deliious n Elstr ws quite similr to CH 3 COOH. Both ultivrs showe higher thinning when stronger onentrtions of CS x were use (Tle 2, 3). Also, the men fruit weights of oth ultivrs inrese s CS x onentrtions inrese. On Elstr over thinning oul e estimte when CS x 30 ml l 1 or 50 ml l 1 pplitions erese the numer of (lrge) fruit >70 mm (53 or 44 respetively) elow the level of hn thinne trees (75) (Tle 3). No effet on russeting ws foun t hrvest for oth ultivrs. Also oth ultivrs respone positively for return loom when higher CS x onentrtions were pplie. For NCl onentrtion stuy only Elstr ws ville (Tle 3). As higher onentrtions of NCl were use, the stronger thinning ourre with etter fruit growth. Similr to CS x pplitions, over thinning oul e notie in the se of NCl 20 g l 1 pplition sine the numer of lrge fruit per tree (42) erese remrkly ompre with hn thinne trees (75). A signifint inrese in russeting ws reore ut ws not juge to e severe. When inresing onentrtions of NCl were pplie on Elstr signifint liner improvement of return loom ws oumente. At hrvest nlyses of inner fruit hrteristis were ssesse for Elstr fruit smples when the highest onentrtions of CH 3 COOH, CS x n NCl were pplie (Tle 4). Higher ontent of solule solis ws foun when CS x 50 ml l 1 n NCl 20 g l 1 were pplie. Sine these two tretments tully inue over thinning, the smll numer of fruit per tree oul e the reson for etter solule soli ontent. STOPAR et l. (2002) prove higher solule solis ontent, higher strh ontent n etter flesh firmness in the fruit of low ropping Jongol pple trees. The pplition of thinning gents h no influene on the strh ontent while the fruit flesh ws lightly firmer on hevily thinne NCl 20 g l 1 trete trees. Disussion Literture showing CS x thinning results is ontritory s re the results from this trils. In Frne n Switzerln severl hemil gents suitle for orgni frming were teste n lime sulphur ws foun s one of the most promising (BERTSCHINGER et l. 2000; WARLOP 2002). In three ultivr tril, MELAND (1998) foun CS x 50 ml l 1 only thinne Arom effetively. In our experiment the onentrtion stuies emonstrte onentrtion epenent CS x tion on Golen Deliious n El- Tle 2. Effet of CH 3 COOH n CS x on phytotoxiity one week fter sprying, fruit thinning, men fruit size, russeting n return loom of Golen Deliious /M.9 pple trees, Tretments (ml l 1 ) Phytotoxiity Fruit numer (1 10) x 100 flower lusters 1 Fruit weight (g) Fruit numer >68 mm Russeting of fruit (0 10) y Return loom (1 10) z Control Hn thin CH 3 COOH (10) CH 3 COOH (30) CH 3 COOH (50) CS x (10) CS x (30) CS x (50) Signifine CH 3 COOH L*** L* NS NS NS L** CS x L*** L** L** L* NS L** xestimtion on My 7 th ; 1 = no visul mge; 5 = meium phytotoxiity; 10 = e tree. y 0 = no russeting present; 10 = 100% of fruit is overe y russet t hrvest time. z1 = no flowering; 10 = unnt flowering of trees next seson. NS,*,**,*** Non signifint or signifint liner (L) regression trens t P 0.05, 0.01, or respetively. Europ.J.Hort.Si. 2/2008

6 60 Stopr: Orgni pple thinning str fruit sission. However, ifferenes existe in the severity of thinning when CS x 30 ml l 1 pplitions were one in four trils. On Summerre not enough thinning ws inue while on Golen Deliious (yer 2003) moerte fruit sission ws foun, n very strong thinning ws oserve on Golen Deliious (yer 2002) n on Elstr. Whenever equte thinning ourre it enhne fruit growth n return loom. No fruit russeting ws inue y CS x tretments. When HOBL et l. (2003) evlute the pple s ontrol effetiveness of CS x 20 g l 1 he onlue tht orgni growers woul e fore to fin lne etween goo effiy ginst s n the phytotoxi effet of CS x whih mnifests s reue lef size. These experiments show CS x 30 ml l 1 phytotoxiity ppers s stunte growth of young leves n shoots few ys fter CS x sprying n lste out two month. Similr phytotoxi pperne n severity, s fter CS x 30 ml l 1 on Summerre (Fig. 1), ws oserve week fter the pplition of CS x 10 ml l 1 on Golen Deliious n 30 ml l 1 or 50 ml l 1 on Elstr (Tle 2, 3). It n e onlue tht CS x is possile thinning gent for orgni pple trees ut inonsistent thinning ourre fter its pplition n lso tht some phytotoxiity is expete with 10 ml l 1 or stronger onentrtions. Different uses of plnt oil emulsions were mentione for fruit growing prtie, i.e. to protet the plnt tissue from frost injury, s insetiies, to ely loom or thin fruits (JU n DUAN 1991; STRIMMER et l. 1997; PENDER- GRASS et l. 2000). Bloom thinning of Deliious pple ws effetive y orn oil emulsion 30 g l 1 to 50 g l 1 etween preloom n 20 % full loom; they were less effetive when pplie t 50 % full loom or lter; the effetiveness of oil tretments epene on onentrtion too (JU et l. 2001). Also, STRIMMER et l. (1997) reporte stisftory pple thinning y rpe oil 20 g l 1 pplie uring full loom. In the present experiments the full loom pplition of rpe oil emulsion 10 g l 1 i not thin suffiiently, ut rpe oil 30 g l 1 n soy oil 30 g l 1 emulsions thinne Golen Deliious n Summerre trees equtely n reltively onsistent. Also sunflower oil 30 g l 1 thinne Golen Deliious trees signifintly. Better fruit growth ws inue on Golen Deliious thinne trees while the return loom of oth ultivrs ws not enhne. All oil thinning gents inue low or moerte fruit russeting on oth ultivrs. Also, STRIMMER et l. (1997) n KELDERER et l. (1998) oserve pple fruit russeting, fruit eformtion n prtil lef nerosis following the pplition of plnt oils. In the presente work the pplition of oil emulsion 30 g l 1 inue lef wrinkling n stunte growth of young shoots n ws less pronoune ompre to CH 3 COOH, NCl or CS x. It ws neessry to use emulsifiers with the oil pplitions euse oils lone woul seprte when mixe with wter. JU et l. (2001) use 10 % emulsifier in orn oil efore issolving in wter for sprying purpose. Presente experimentl rpe oil gent ws ftory prepre with 8 % emulsifiers. When the sme mount of emulsifiers ws sprye lone without oil (2.4 g l 1 emulsifier wter solution), thinning ourre on Summerre trees n lso russeting n phytotoxiity ws oserve to similr extent s oil tretments. It oul e onlue from these results tht the existene of emulsifiers in oil gents is one of the min uses of fruit thinning n fruit russeting when plnt oil emulsions re pplie. In ition, it shoul e mentione tht the ftory prepre Tle 3. Effet of CH 3 COOH, CS x n NCl on phytotoxiity one week fter sprying, fruit thinning, men fruit size, russeting n return loom of Elstr /M.9 pple trees, Tretments (ml l 1 or g l 1 ) Phytotoxiity Fruit numer (1 10) x 100 flower lusters 1 Fruit weight (g) Fruit numer >70 mm Russeting of fruit (0 10) y Return loom (1 10) z Control Hn thin CH 3 COOH (10) CH 3 COOH (30) CH 3 COOH (50) CS x (10) CS x (30) CS x (50) NCl (10) NCl (15) NCl (20) Signifine CH 3 COOH L*** L** L** NS NS L*** CS x L*** Q** L*** L*** Q** L** NS L*** Q* NCl L*** L*** L*** L** L* L*** x Estimtion on My 11 th 2004; 1 = no visul mge; 5 = meium phytotoxiity; 10 = e tree. y 0 = no russeting present; 10 = 100% of fruit is overe y russet t hrvest time. z 1 = no flowering; 10 = unnt flowering of trees next seson. NS,*,**,*** Non signifint or signifint liner (L) or qurti (Q) regression trens t P 0.05, 0.01, or respetively. Europ.J.Hort.Si. 2/2008

7 Stopr: Orgni pple thinning 61 Tle 4. Anlyses of vrine for Elstr fruit flesh hrteristis t hrvest following the strongest thinning tretments in Tretments (ml l 1 or g l 1 ) Solule solis ( Brix) Strh ioine pttern (1 10) y Flesh firmness (N) Control 11.4 x Hn thin CH 3 COOH (50) CS x (50) NCl (20) x Men seprtion within olumn y Dunn s multiple rnge test, P y1 = highest strh ontent; 10 = no strh present rpe oil gent onsiste of 92 % rpe oil n 8 % emulsifiers while the soy n sunflower oil mixture ontine just 4 % emulsifiers. A reltively suessful thinning y sunflower n soy oil emulsion 30 g l 1 inite hlf the mount of emulsifiers in oil mixtures re enough to prepre n equte oil thinning gent. Also, itionl experiments with rnge of ifferent emulsifiers lone or in omintion with oils shoul e performe to fin possile thinning gent tht hs etter thinning response n inues less russeting. Few referenes on NCl or CH 3 COOH thinning re ville. PFEIFFER n RUESS (2002) report on stisftory thinning n severe lef mge when NCl 15 kg h 1 ws sprye on Pinov pple trees t full loom stge. Presente experiments shown tht 15 g l 1 NCl pplition inue light thinning in Golen Deliious (NS) n in Summerre. When NCl 10 g l 1, 15 g l 1 or 20 g l 1 ws use on Elstr thinning ws muh stronger n rising with onentrtion, lso the return loom. Tking into ount tht Elstr is iffiult ultivr to thin; non-onsistent thinning response ws oserve. Also, light fruit russeting ppere fter NCl pplition on Elstr n Summerre pples. The CH 3 COOH 30 ml l 1 pplition ws foun to e poor thinning gent n, onsequently, lightly enhne fruit growth n slightly etter return loom resulte. However, CH 3 COOH pplition i not inue fruit russeting. When CH 3 COOH 30 ml l 1 or NCl 15 g l 1 were sprye, the gretest phytotoxi effet ourre (ompre to other thinners) n ws evient mostly s urning of lef eges n prtly s stunte growth of young leves. The phytotoxiity ppere few ys fter sprying n lste eleven weeks. Before reommention on the ove teste hemils s orgni hemil thinning gents n e me, more experiments shoul e onute to lrify the thinning response n possile phytotoxiity mge to other pple ultivrs. Also, little is known out environmentl influene (suh s temperture or ir humiity t the time of pplition) on the thinning tion, n whih my result in the inonsisteny of thinning or fruit russeting fter the pplition of the thinners teste. Aknowlegements The uthor thnks the Slovenin Ministry of Agriulture, Forestry n Foo n Slovenin Ministry of Higher Eution, Siene n Tehnology for the finning of the work. Also like to thnks Romn Mve, Boštjn Sje n Monik Bokl for tehnil ssistne in fiel work. Referenes BERTSCHINGER, L., F. WEIBEL, W. STADLER, A. SCHMID, H. HOHN, C. EVEQUOZ n W. PFAMMATTER 2000: Thinning proeures for regulting pple fruit qulity n yiel. In: ALFOLDI, T., W. LOCKERETZ n U. NIGLI (es): Pro. 13 th Intern. IFOAM Si. Conferene, Bsel, Switzerln, FALLAHI, E. n K.M. WILLEMSEN 2002: Blossom thinning of pome n stone fruit. HortSiene 37, GREENE, D.W. 2002: Chemils, timing, n environmentl ftors involve in thinner effiy on pple. HortSiene 37, HOBL, I., J. JONG n P.F. HEIJNE 2003: Effiy n phytotoxiity of lime sulfur in orgni pple proution. Ann. Appl. Biol. 142, JU, Z. n Y. DUAN 1991: New uses of vegetle oils in fruit proution. Goo Fruit Grow. 52, JU, Z., Y. DUAN, Z. JU n A. GUO 2001: Corn oil emulsion for erly loom thinning of trees of Deliious pple, Feng Hung peh, n Bing herry. J. Horti. Si. Bioteh. 76, KALLSEN, C.E. 2001: Petroleum oils s nvel ornge fruit thinning gents. HortTehnology 11, KELDERER, M., M. STRIMMER, M. CASERA n E. LARDSCHNEIDER 1998: Prim esperienze sul irmento el melo in fruttioltur iologi. Riv. Frutti. Ortoflori. 60, MELAND, M. 1998: Thinning pples n pers in Nori limte. III. The effet of NAA, ethephon n lime sulfur on fruit set, yiel n return loom of three pple ultivrs. At Hortiulture 463, PENDERGRASS, R., R.K. ROBERTS, D.E. DEYTON n C.E. SAMS 2000: Eonomis of using soyen oil to reue peh freeze mge n thin fruit. HortTehnology 10, PFEIFFER, B. n F. RUESS 2002: Sreening of gents for thinning lossoms of pple trees. In: Förergemeinshft Ökologisher Ostu e. V. (e.): Pro. 10 th Intern. Conferene on Cultivtion Tehnique n Phytopthologil Prolems in Orgni Fruit Growing n Vitiulture, Weinserg, Germny, STOPAR, M., U. BOLCINA, A. VANZO n U. VRHOVŠEK 2002: Lower rop lo for v. Jongol pples (Mlus x omesti Borkh.) inreses polyphenol ontent n fruit qulity. J. Agri. Foo Chem. 50, STRIMMER, M., M. KELDERER n K. PIEBER 1997: Neue Ausünnungsmethoen im iologishen Apfelnu. Erwersostu 39, TROMP, J. 2000: Flower-u formtion in pome fruits s ffete y fruit thinning. Plnt Growth Regul. 31, WARLOP, F. 2002: Regultion e l hrge u pommier en griulture iologique: quelques elirissements. Rev. suisse viti. rori. horti. 34, WERTHEIM, S.J. 1997: Chemil thinning of eiuous fruit trees. At Hortiulture 463, WERTHEIM, S.J. 2000: Developments in the hemil thinning of pple n per. Plnt Growth Regul. 31, WILLIAMS, M.W. 1994: Ftor influening hemil thinning n upte on new hemil thinning gents. Compt Fruit Tree 27, WILLIAMS, K.M. n E. FALLAHI 1999: The effets of exogenous ioregultors n environment on regulr ropping of pple. HortTehnology 9, Reeive June 11, 2007 / Aepte Deemer 14, 2008 Aresses of uthors: Mtej Stopr, Agriulturl Institute of Sloveni, Hquetov 17, 1000 Ljuljn, Sloveni, e-mil: mtej.stopr@kis.si Europ.J.Hort.Si. 2/2008