ON CITRUS TREES IN FLORIDA1

Transcription

1 TRAMMEL AND SIMANTON: OILS EFFECTS ON TREES 9 PROPERTIES OF SPRAY OILS IN RELATION TO EFFECT ON CITRUS TREES IN FLORIDA Kenneth Trmmel nd Willim A. Simnton Abstrct Petroleum oil sprys re widely used s pes ticides for Florid citrus but hve undesirle effects on trees nd fruit. As prt of progrm to estlish optimum spry oil specifictions for Florid, selected oils were evluted in field studies to relte vrious properties to physiolog icl effects on citrus. Distilltion tempertures nd degree of refinement (unsulfonted residue or UR) were found to be the properties best correlted with dverse effect of oils on fruit nd trees. The temperture t which 0% of n oil dis tills (0% DT) ws directly relted to dverse effect on fruit color, fruit qulity, nd, to some extent, lef drop. These dverse effects incresed s the 0% DT incresed in the rnge of 80 to 80 F (determined t 0 mm Hg by ASTM method D-0). Under norml use conditions, n oil with the 0% DT below 00 F showed no significnt dverse effects; oils with 0% DT of 0 F nd F were reltively sfe to the tree nd fruit; nd oils with F nd 80 F 0% DT were excessively phytotoxic in some instnces. The detrimentl effect of low UR, wide-boiling oil with 0 F 0% DT ws greter thn tht of the high UR, nrrowboiling oil of F 0% DT. Low UR ws relted to occurrence of oil blotch nd incresed lef drop. Approximtely % of the fruit on trees spryed with n oil of 8% UR were ffected by oil blotch. Highly refined oils cused no fruit blemishing. Prffinic nd nphthenic oils of comprle distilltion tempertures showed no difference in physiologicl effect on citrus trees. Introduction Petroleum oil sprys re widely used by Florid citrus growers for controlling scle in- Florid Agriculturl Experiment Sttions Journl SerlThe reserch on which this pper is bsed ws sup ported in prt by grnt from Esso Reserch nd Engi neering Compny. Assistnt Entomologist nd Entomologist, respectively, University of Florid Citrus Experiment Sttion, Lke Alfred, Florid. sects, whiteflies, spider mites, nd gresy spot disese. Whle oil is n effective brod-spectrum pesticide, its use is limited by certin dverse effects on citrus. Improper use of oil sprys my dely fruit coloring, retrd soluble solids development, induce fruit blemishing, nd cuse excessive lef nd fruit drop. Reduced fruit set nd incresed susceptibility of the tree to cold wether injury hve been ttributed to oil sprys pplied lte in the seson. Where recom mendtions on ppliction rtes nd timing re followed, excessive tree dmge seldom results. However, dmge from oil sprys is not un common even though it is not lwys striking. Where problems do occur, detils out oil prop erties, formultion, nd ppliction, sufficient to estlish proble cuse, re not lwys ville. Spry oils used in Florid re quite vrile in distilltion chrcteristics, viscosity, moleculr weight, hydrocrbon composition, nd degree of refinement. Informtion pertining to the reltionship of these properties nd perfor mnce of oil on Florid citrus is needed. Work ws begun in 9 to estlish the re ltionship of spry oil properties to pesticidl efficiency nd phytotoxicity to citrus under Florid conditions. The ultimte objective ws to describe optimum specifictions for Florid citrus spry oils. A report on the first phse of this work nd review of the literture relting to spry oil reserch in Florid nd other res were pre sented in 9 by Trmmel (). Lortory investigtions reveled tht evportion rte of n oil s mesured by distilltion tempertures ws the most relile property for predicting pesticidl efficiency nd certin physiologicl effects of n oil. Pesticidl efficiency in reltion to 0% distilltion temperture (0% DT) of spry oils commenced t out 70 F (deter mined t the reduced pressure of 0 mm Hg by ASTM method D-0) nd incresed to out 80 F, beyond which no further gin in effici ency ws pprent. Effect of oil on the physiol ogy of the citrus plnt followed essentilly the sme trend, in tht the higher boiling oils pro duced more severe nd longer lsting effects. These studies further indicted tht degree of refinement ws fctor in reltion to phyto toxicity.

2 0 FLORIDA STATE HORTICULTURAL SOCIETY, 9 To supplement the lortory studies, field work ws expnded in 9 to evlute the pes ticidl nd phytotoxic ction of commeril nd experimentl oils covering the distilltion tem perture rnge corresponding to pesticidl effici ency. Degree of refinement (unsulfonted resi due or UR) nd hydrocrbon composition (prffinic nd nphthenic) were lso injected s vriles. The work hs dvnced fr enough to support tenttive recommendtions for spry oil properties bsed on the results of insect, spider mite, gresy spot disese, nd phytotoxicity studies. This pper dels with the phytotoxicity studies. The pesticidl investigtions re reported in concurrent pper () nd tenttive recommendtions for spry oils for Florid citrus re presented in third pper (). Experimentl Methods Selection of Oils: The bsis for selection of the oils evluted in these studies ws discussed in concurrent pper (). Vlues for selected properties of these oils re presented in Tle. Four highly refined (9% UR or higher), rel tively nrrow-boiling prffin bse oils (oils to ) were selected for relting distilltion tem pertures of oils to dverse physiologicl effects on citrus. The 0% DT of these oils covered the rnge of insecticidl efficiency (70 to 80 F) t pproximtely 0 increments. A nphthenic oil (oil ), comprle to oil in distilltion chrcteristics, ws included for studying the importnce of hydrocrbon composition of oil in reltion to performnce of n oil. Oil, low UR, wide-boiling oil, ws studied to relte de gree of refinement nd 0% to 90% distilltion temperture spred to dverse plnt rections. A "reformed" oil (prffin-type oils produced by specil refining technique) (), number 8 in Tle, ws lso included in some field tests. Preprtion nd Appliction of Oils: All oils re mixed in the lortory with n oil-soluble, nonionic emulsifier, Rohm nd Hs' Triton X-07, to chieve similr emulsifiction nd de positing chrcteristics. The oils were pplied s dilute sprys with truck-mounted high pressure spryer equipped with double Boyce hndguns, nd operted t 0 to 00 psi, de- Tle. Properties of petroleum oils evluted in field studies for physiologicl effects on citrus trees. Oil No. Temperture, F,b or distilltion o 0% 0% 90% Distilltion rnge, F 0%-90% URC % API grvity d Avg. mol wtti Viscosity t 00 F ssuf Hydrocrbon composition. Cp Cn. %g C Dt provided by the supplier Humble Oil nd Refining Co. bby ASTM method D-0 t 0 mm Hg. cby ASTM method D-8. dby ASTM method D-87. eby correltions of Mills, Herscheler, nd Kurtz 9. Ind. Eng. Chem. 8:. fby ASTM method D-. ^Per cent prffinic crbons (Cp), per cent nphthenic crbons (Cn), nd per cent romtic crbons (C) s determined by RI-KVGC method.

3 TRAMMEL AND SIMANTON: OILS EFFECTS ON TREES pending on the size of the trees. Thorough, fullcoverge sprys were pplied s recommended for scle control. Phytotoxicity Studies: The oils in Tle were evluted on 'Hmlin,' 'Pinepple,' nd 'Vlenci vrieties of sweet ornge to determine the reltionship between oil properties nd effect on fruit qulity, fruit color, lef nd fruit drop, nd oil blotch. All vrieties were on rough lemon rootstock. Observtions were mde of ll the trees involved following the freeze of Jnu ry 0-Februry, 9, to determine if cold injury ws induced by the lte oil pplictions. Unless otherwise noted, ll experiments were conducted in rndomized blocks design with 8 replictions of -tree plots.. Studies on 'Hmlin' Ornge Erly-Se son Vriety: This vriety ws selected becuse it ws felt tht certin dverse effects of spry oils, prticulrly effect on fruit color nd qul ity, would be most evident with n erly mtur ing vriety. Oils,,, nd 8 (Tle ) were pplied in n 8-yer-old 'Hmlin' grove t the Citrus Experiment Sttion on April 9, 9. All oils were pplied to four -tree plots t.% con centrtion nd the ppliction ws timed on the bsis of fruit dimeter in n ttempt to induce oil blotch. Oil blotch hs been reported () to occur when oil sprys were pplied to fruit in the dimeter rnge of 0.7 to. inches. The fruit in this block verged 0.8 inch dimeter when tretments were pplied. A second ppli ction of ech oil t.0% ws mde on August. Fruit smples were picked November 0 nd December 9 for degreening studies nd internl qulity nlysis. Oils to were evluted for effect on inter nl qulity, fruit color, nd lef drop in 9-yer-old 'Hmlin' grove est of Lke Hmil ton. Single pplictions of ech oil t % nd.% were mde in the summer (July -7) nd erly fll (September -). Lef drop counts were mde weekly for n 8-week period following the summer ppliction, nd fruit smples were hrvested nd nlyzed October nd November 0.. Study on 'Pinepple* Ornge Mid-Seson Vriety: Oils to were pplied t.0% con centrtion on October -, 9 to 9-yer-old 'Pinepple' trees est of Lke Hmilton. These trees hd received.0% of n oil similr to the 80 F oil s regulr summer ppliction. Fruit smples were picked December, 9 nd Jnury nd 8, 9 for degreening-, color grding, nd internl qulity nlysis.. Study on 'Vlenci' Ornge Lte-Seson Vriety: Oils to were pplied t.0% concentrtion on November 0, 9 to mture, -yer-old 'Vlenci' trees ner Clermont. These trees hd received summer ppliction of.0% of n oil quite similr to the F oil. Fruit smples were hrvested Februry nd 8 nd Mrch 7, 9 for internl qulity nlysis. The September, October, nd November p plictions of oils on 'Hmlin,' 'Pinepple,' nd 'Vlenci' ornges, respectively, were not typicl of ctul spry prctices. The purpose of these lte pplictions ws to determine effect of dif ferent oils on fruit qulity nd color when p plied during or ner the beginning of the fruit mturtion period nd to relte ny effect on cold hrdiness to properties of the oils involved. Fruit color ws evluted by grding the fruit for pckout on the bsis of color only. In most instnces, the fruit were grded before degreening nd fter, 8, nd 7 hours ex posure to ethylene gs in commercil-type degreening room. Internl qulity of the fruit ws evluted by stndrd methods for deter mintion of per cent soluble solids ( Brix), cid, nd juice content. All fruit smples tested for color nd internl qulity were comprised of t lest 0 nd in most cses 0 fruits from ech plot. Results nd Discussion Per Cent Soluble Solids ( Brix): The dt in Tle show the effect on soluble solids development in 'Hmlin' ornges by the vrious oils t rtes in both summer nd erly fll pplictions. Most tretments showed lower soluble solids thn the check in October follow ing the July ppliction but only the.% rte of the oils with nd 80 F 0% DT significntly retrded solids development. In November, the retrding effect of ll the tret ments ws essentilly overcome; however, the lowest solids content ws ssocited with the 80 F oil. The retrding effect on solids developoment incresed with increse in distilltion tempertures. There ws no difference between oils of different hydrocrbon composition, nd the effect of oil ws probly due to hevy molecules in the upper end of the wide distill tion rnge. In most instnces, higher solids

4 FLORIDA STATE HORTICULTURAL SOCIETY, 9 Tle. Per cent soluble solids in 'Hmlin ornges on smpling dtes following norml nd lte pplictions of spry oils hving different distilltion tempertures.* Spryed 7/-7/ Spryed 9/-/ Tretment (norml)** (lte)** Oil 0% DT Rte smpled smpled F 7. 0// /0/ 0// /0/ No. Check " c c cd d c 9. c b ed 9. de 9.9 e de c cde f c e 9.0 ef 9. de def 9. de de cde cde f c de 9.9 ef 9.T 9.0"" Fruit smples were held in n ethylene degreening chmber 7 hours prior to nlysis. Tretment mens in given column followed by the sme letter re not significntly different t the % level ccording to Duncn's Multiple Rnge Test. +Minimum legl soluble solids required for color-dded fresh fruit on the smpling dte. content ws ssocited with the low rte of ppliction of given oil, s would be expected. Following the mid-september ppliction, effect on solids development ws considerly greter thn fter the July tretments. How ever, even with the lte ppliction, soluble solids in fruit spryed with both rtes of the 8 F oil nd % of the 0 F nd F oils were not significntly lower thn the check in October. Trees treted with the 80 F oil t both rtes, the wide-boiling, low refined oil (oil ) t both rtes, nd the 0 F oil t.%, produced fruit tht would not pss the October mturity requirement. By November 0, Brix redings hd incresed in ll but tret ment, but soluble solids content of fruit from ll tretments except % of oils nd ws significntly lower thn the check. Soluble solids deelopment (dt not shown) in fruit receiving the double ppliction (.% rte in April nd.0% rte in August) of oils,,, nd 8 showed the sme trend in reltion to oil heviness s tht discussed ove. How ever, only smples from plots spryed with the 80 F oil were significntly lower thn the check, nd this effect persisted s lte s Decem ber 9. The reltionship between oil heviness nd delyed solids development in 'Pinepple' nd 'Vlenci* ornges ws the sme s for 'Hmlin' ornges (Tle ). Dely of solids development ws greter by the hevier oils thn by the lighter oils. When the 'Pinepples' reched their pek qulity in mid-jnury, only fruit spryed with the heviest oil nd the wide-boiling oil were significntly below the check in soluble solids. Even s erly s December, the Octo ber ppliction of oils s hevy s F 0% DT showed no retrdtion of solids development. The 'Vlenci' smples were picked following the freeze of Jnury 0-Februry, 9. The fruit ws frozen on the tree but qulity deterior tion hd not set in by the first smpling dte. However, the condition of the fruit in subse quent smples ws probly ffected by the freeze injury. Only firm, well-ttched fruit were selected for the lst smples. Only the 80 F oil nd the wide-boiling oil showed sig nificnt retrdtion of solids development in Mrch. Per Cent Acid, Brix/Acid Rtio, nd Juice Content: No dt re presented for these juice chrcteristics becuse in most cses the tret ments showed no significnt effects nd no trends in reltion to oil properties could be estlished. Where deterimentl effects did oc cur, they were usully ssocited with the heviest oil nd/or the wide-boiling oil. Fruit Color: The distilltion tempertures of the oils were reflected in fruit color. Hevier oils hd the gretest retrding effect on degreening. Tle depicts fruit color s per cent pckout of 'Hmlin' ornges following pplic tion of oils to t rtes in July nd Sep tember. Most tretments showed some retrd ing effect on degreening, but.% concentrtion of the F oil nd both rtes of the 80 F oil significntly delyed degreening on October. All significnt effects were overcome by November 0. Dely of degreening ws greter by the September ppliction thn by the July ppliction, but the reltionship of color develop ment to oil properties remined the sme. The effects of the lte pplictions of.% of oils nd were still pprent November 0. These differences previled on the tree nd fter nd 8 hours exposure to ethylene gs. How ever, the checks did not ttin 9% pckout until fter 7 hours so the dt for 0,, nd

5 TRAMMEL AND SIMANTON: OILS EFFECTS ON TREES Tle. Per cent soluble solids in fpinepple nd 'Vlenci ornges following fll ppliction of spry oils hving different distilltion tempertures.* Tretment** Pinepple--spryed 0/- Vlencif-- spryed /0/; Oil 0% DT No. F /; // smpled on // /8/ smpled on // /8/ /7/ Check --. c be 0. b be.0 c 0. be 0. b d 0.8 c.0 be 0. c 0. c 0.7 c. c. c. c 0.8 be 0. b cd 0.9 c.8 c 0. c 0. b 0.8 be Tretment mens in given column followed by the sme letter re not significntly different t the % level ccording to Duncn's Multiple Rnge Test. All oils pplied t.0% by volume. 'Vlenci smples were picked following the freeze of /0-//. Tle. Color of 'Hmlin' ornges expressed s per cent pckout fter 7 hours of ethylene degreening on smpling dtes following norml nd lte pplictions of spry oils hving different distilltion Oil 0% DT Rte No. Check % - tempertures.* Spryed 7/-7/ (norml) 0// ,8 7,.,.9. c. c d cd., c c c /0/ Spryed 9/-/ (lte) smpled 0// /0/ c c..8 cd c e c. 7. de "Tretment mens in given column followed by the sne letter re not significntly different t the % level ccording to Duncn's Multiple Rnge Test. c c be 8 hours re not shown. Tle shows the sme reltionship between oil heviness nd col or development in 'Pinepple' ornges. The heviest oils cused poor color development on the tree nd this sitution persisted through 8 hours of ethylene degreening. Lef Drop nd Fruit Drop: Lef drop in reltion to properties of spry oils is depicted in Figure. Although lef drop following oil pplictions in most cses ws not considered excessive, the mount in some of the tretments ws double tht of the check. Lef drop in plots spryed with.% of oils,, nd ws significntly greter thn lef drop in the check. Following the April ppliction of.% of oils,,, nd 8, excessive lef drop (dt not shown) occurred in ll oil-treted plots over -week period. Although ll oils were significnt from the check, differences between oils were not significnt. Lef drop ssocited with oil 8 ws out triple tht of the check while lef drop

6 FLORIDA STATE HORTICULTURAL SOCIETY, 9 Tle. Color of 'Pinepple ornges expressed Tretment* Oil No. 0% DT F Check -- \ll s per cent pckout fter 0,, nd 8 hours of ethylene degreening. Fruit ws smpled December, 9 following n October - ppliction of spry oils hving different distilltion tempertures. oils pplied t.0% by volume. V.-V Tretment mens the sme letter re not significntly different t the % level. 0 hr be.7 c Degreened for** hrs. 8 hrs be c c b in given column followed by cused by the other oils ws out times s high s in the check. Lef drop in plots spryed with the low UR oil ws gretest during the first week fter ppliction while the highest drop with the highly refined oils occurred during the fourth week fter sprying. Fruit drop (dt not shown) during this sme period ws lso relted to oil heviness nd refinement. The lightest oil cused out 0% greter drop thn occurred in the check; the F oil cused out twice s much s in the check, nd the low refined oil cused out times s much fruit drop s in the check. Fruit drop in plots spryed with oil ws only out hlf s gret s in the check plot due to very light initil fruit set. Oil Blotch: Oil blotch occurred only on fruit spryed with oil, the low refined oil (8% UR). Oils,, nd 8 cused no fruit blemish ing. Following ppliction on April 9, peel 8 o PARAFFINIC, HIGH UR D PARAFFINIC, LOW UR A NAPHTHENIC, HIGH UR SHADED SYMBOLS =.: OIL CONC 0 CLEAR SYMBOLS = OIL CONC % % DISTILLATION TEMP. OF OIL ( F) Figure. Lef drop during: n 8-week period in reltion to 0% DT of spry oils pplied July -7, 9 ornge trees ner Lke Hmilton. Leves were counted in squre foot re under ech tree. to'hmlin'

7 TRAMMEL AND SIMANTON: OILS EFFECTS ON TREES Figure.-Oil blotch on immture nd mture 'Hmlin' ornges following pplictions of low UR oil on April 9 when fruit verged 0.8 inch dimeter. injury ws evident by My 0 on fruit spryed with oil. By June, the ffected res of the fruit showed gryish-brown discolortion nd were slightly corky in texture. This condition intensified nd the "blotches" incresed in size s the fruit enlrged nd were definite grdelowering fctor t hrvest time. Figure de picts the erly nd lte stges of this condition. About % of the fruit were ffected, mostly on the south side of the trees. Cold Wether Injury: The trees receiving oil pplictions in September, October, nd Novem ber were observed following the freeze of Jnu ry 0-Februry, 9 to determine if result nt injury might be relted to properties of the oils. No injury relted to the oil ws detected in the 'Hmlin' nd 'Pinepple' blocks following 9 hours of tempertures under F. Lef drop in the 'Vlenci* grove over -week period following the freeze (dt not shown) ws sig nificntly hevier in plots spryed with the 80 F oil thn in plots spryed with the lighter oils nd the check. No pprent tree dmge oc curred lthough 0 to F tempertures persisted for 0 hours. Yield: Studies hve not progressed fr enough to provide yield dt in reltion to oil properties, but one observtion worth noting hs been mde. Crop estimtes were mde in De cember, 9 for the 'Hmlin' trees spryed in April nd August with.% nd.0%, respec tively, of oils,,, nd 8. These trees hd been spryed in My nd September of the previous yer with the sme oils t.%. A light crop ws pprent erly in the 9 seson for trees spryed with the heviest oil (80 F). The December estimtes reveled the following yields (boxes/-tree plot) in reltion to 0% DT: 0 F,.; F,.07; 0 F,.97; 80 F,.9. The check plots yielded. boxes. Yield for the heviest oil ws significntly lower thn for the other tretments. Whether this low yield ws due to reduced blossom production or reduced fruit set ws not determined. Results of these preliminry field evlutions of selected spry oils support previous limited lortory nd field studies relting oil proper ties to dverse physiologicl effects on citrus in Florid. Delyed fruit degreening, retrded sol uble solids development, nd, to some extent, lef drop were directly relted to oil heviness s mesured by distilltion tempertures. Nrrowboiling oils with 0% DT below 0 F cused no deleterious effects under norml use conditions. Hevier oils nd wideboiling oil hd greter effect on the tree nd fruit. Degree of refinement s indicted by UR ws lso n importnt fctor in phytotoxic effect of oils. Oil blotch ws ssocited only with n 8% UR oil wheres severl oils ove 9% UR did not cuse fruit blemishing. Lef drop ws ssocited wtih both distilltion temper tures nd UR, the hevier oils nd low refined oils hving the gretest effect. No other prop erties of the oils tested hd ny bering on plnt response, except viscosity, which is nother mesure of oil heviness. However, viscosity is less precise mesure thn distilltion temper tures nd must be considered in reltion to hydrocrbon composition to be meningful. In specifying spry oil properties, primry considertion should be given to distilltion tem pertures nd UR s indictors of plnt sfety. LITERATURE CITED. Riehl, L. A., J. P. LDue, nd J. L. Rodriguez. 9. Efficiency of re-formed oil ginst citrus red mite eggs nd Cliforni red scle. J. Econ. Entomol. 8() : Simnton, W. A. nd K. Trmmel. 9. Recom mended specifictions for citrus spry oils in Florid. Proc. Fl. Stte Hort. Soc. 79: -9.. Thompson, W. L. 99. The reltionship of timing post-bloom sprys to certin fruit blemishes on ornges. The Citrus Ind. 0() : -8, 8.

8 FLORIDA STATE HORTICULTURAL SOCIETY, 9. Trmmel, K. 9. Properties of spry oils in rel tion to performnce s citrus tree sprys in Florid. PhD Disserttion, Univ. of Fl. pp.. Trmmel, K. nd W. A. Simnton. 9. Properties of spry oils in reltion to citrus pest control in Florid. Proc. Fl. Stte Hort. Soc. 79: 9-. RECOMMENDED SPECIFICATIONS FOR CITRUS SPRAY OILS IN FLORIDA Willim A. Simnton nd Kenneth Abstrct Trmmel Petroleum oil hs been widely used s pesticide on Florid citrus for mny yers. Sev erl million gllons of oils with vrying proper ties re pplied nnully. While this use hs been resonly stisfctory, dverse effects on tree nd fruit re common nd frequently re of concern. Reserch initited in 9 hs disclosed the oil properties necessry for optimum perfor mnce s citrus tree sprys in Florid. The significnce nd methods of testing for these properties re discussed. Specifictions re pre sented for oil types; one designted FC - is for norml summer use nd provides mximun pesticidl efficiency without excessive physiologicl effects on tree nd fruit. The other, designted s FC -, provides mini mum physiologicl effect consistent with de qute pesticidl efficiency nd is for use where lighter, sfer oil is needed. More informtive leling of spry oils, in cluding disclosure of certin oil properties, is recommended. Introduction Emulsified oil hs been one of the most wide ly used pesticides for the pst 0 yers nd undoubtedly will retin this sttus for mny yers to come. Severl million gllons of petrol eum oil re spryed on Florid citrus trees ech yer. All of this oil hs been purchsed without benefit of specifictions to indicte tht it ws suitle oil for Florid conditions. This ws Florid Agriculturl Experiment Sttions Journl Ser ies No. 7. lthe reserch on which this pper is bsed ws sup ported in prt by grnt from Esso Reserch nd Engi neering Compny. Entomologist nd Assistnt Entomologist, University of Florid Citrus Experiment Sttion, Lke Alfred. simply becuse no tests hd been crried out in sufficient detil to pinpoint the desirle nd undesirle chrcteristics of n oil. As result, spry oils hve vried widely in proper ties nd the continer lels hve provided little informtion to describe the contents. In 9 project ws initited t the Citrus Experiment Sttion to review the entire subject of spry oils, evlute the oils currently offered s sprys for Florid citrus nd ttempt to define those properties ssocited with optimum performnce. The results of reserch to this time re presented here s tenttive specific tions for Florid citrus spry oils. Suggestions for informtive leling lso re given. Historicl Bckground One of the first uses of petroleum s n insecticide ws by Hubbrd who used kerosene emulsions on Florid citrus in the 880's. These were supplnted by the light lubricting oils such s used by Yothers in 9, which provided more insecticidl ction thn kerosene. The widespred use therefter of the limited petrol eum products of tht dy ws ccompnied by considerle tree dmge, especilly in Clifor ni. Reserch in Cliforni in the 90's led to the discovery tht refining to n unsulfonted residue vlue ove 8 gretly decresed the phytotoxic effects of spry oils from Cliforni crudes. Such oils were ptented by Volck in April 99. These ptents ffected the price nd vilility of refined spry oils for mny yers. In Florid where citrus is less susceptible to oil dmge, less defined nd cheper oils were tried with resonle success under optimum conditions. Nevertheless, dmge to citrus trees nd fruit, sometimes pprent but more often insidious, hs nd continues to result from im proper use of oil spry. We believe much of this dmge cn be voided. Oil hs mny desirle ttributes s pesti cide for citrus. It will control most kinds of scles nd spider mites, nd helps to control