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ALDICARB RESIDUES IN ORANGESAldicarb Residues in Oranges, Citrus By-Products, Orange Leaves, and Soil afteran Aldicarb Soil-Application in an Orange Grove

Yutak a Iwata, W illiam E. Westlake, Jam es H. Bark ley, Glenn E. Carm an, and F. A. Gunther

A 15% gra nular form ulation of aldica rb (Te mik 15G ) was soil applied to field plots of Valencia andnavel oranges a t 2.5,5.0,10, and 20 lb of active ingredient per acre. To tal carbam ate residues (aldicarb,its sulfoxide an d sulfone) remaining in the soil and translocated to t he leaves and fruit are rep orted.Residues were found in both rind a nd pulp. To tal carba mate residues in molasses and dried citrus pulp,both used to supplement animal feed, orange juice, and orange oil resulting from processing resi-due-bearing frui t for by-products are also reported.

Aldicarb [2-methyl-2-(methylthio)propionaldehyde0-(methylcarbamoyl )oxime,Tem ik, Union Carbide UC-211491 is a broad -spec trum soil-applied systemic pesticidefor the control of insects, mites, and nematod es. In moistsoil, aldicarb is absorbed by plant roots a nd translocatedupward to other parts of the plant. Th e first commercialsales of a ldicarb in th e U nited S tate s were in 1970 followingth e federal registration of a label for use on cotton. In theUS., ldicarb is currently labeled for use on cotton,pea nuts , potatoes, s ugar beets, sugarcane, sweet potatoes,an d several ornamental and nursery plants.Te st da ta indicate that aldicarb may be effective againsta num ber of pests (mites, scale, thrips) attackin g youngand matu re citrus trees (Tashiro and Beaver, 1967; Bolingand Dean, 1968; Tash iro e t al., 1969; Beaver e t al., 1970;Shaw et al., 1970). Field studies are currently underwayto evaluate the effectiveness of aldicarb against citrusnem atodes and phytophagous citrus pests. Registrationof ald icarb for use on citrus requires residue da ta to showthat high levels of toxic residues do not persist in theorchard e nvironment, especially in fru it, at recomm endeddosages used. Rep orted he re are results of analyses of soil,leaves, fruit, and citrus by-products for total carb amateresidues of aldic arb (a ldicarb , aldicar b sulfoxide, aldicar bsulfone) resulting from a soil application.EXPERIMENTAL SECTION

Treatment. Temik 15% granular formulation (15G)was applied to e xperimental plots of 11-year-old OlindaValencia orange on Troyer citrang e root stock on th e IrvineRan ch, Tus tin, Calif. It was applied to the soil on April8,19 74 in perpendicular 4-ft bands around th e peripheryof each tree using a spreade r and th e area was rototilledto a 2- to 4-in. depth t o mix th e formulation with th e soil.Two da ys later, portab le low-head sprinklers applied over2 in. of w ater over a 24-h period to leach th e pesticide intothe root area. Th e plots were subsequently furrow irrigatedon th e regular ranch schedule. Nine-tree (3 X 3) plots,replicated three times, were used for each of the fourdosages. Plot s I , 11, 111, an d IV w ere tre ate d a t 2.5, 5.0,10.0, and 20.0 lb of a ctive ingr edient (AI) per acr e, re-spectiv ely; plot I1 received a second 5.0 lb of AI per a cretreatm ent 36 days after the init ial application. Th e peracre amounts were applied in application bands aroundthe trees which represented approximately 50% of theorchar d floor area.On M arch 19, 1975, 345 days afte r initial application,Tem ik 15G was applied to plot I a t 20 lb of AI per a creonly on the two furrow irrigated sides of th e trees an d to

De part me nt of E ntomology, University of C alifornia,Riverside, California 92521.

plots 111an d IV a t 10 and 20 lb of AI per acre, respectively,in the same manne r as the first application. Plot I1 wasdiscontinued . Th e rototilled plots were sprinkler irrigatedfor 24-h on March 20 and again on March 22. The orchardwas then returned to furrow irrigation.Field Sampling. Ea ch soil sam ple consisted of eigh tcores, 1 2 in. in depth, taken with a 1-in. diameter soilsampling tube. Four trees from each replicate, forminga sq uare, were used for sampling; two cores were takenfrom the inner side of each tree near the center of thetreated band and near the periphery of the tree. Fruitsamples consisted of 32 fruit each, four from each of eighttrees, with one from each qua dran t of each tree a t aboutshou lder height. Leaf sam ples consisted of five 1-in. di-ame ter leaf disks taken from e ach of eight trees using thesystem of W estlake et al. (1973); newly m ature leaves wereselected for sampling. Duplicate leaf sam ples were takenfrom each replicate plot, bu t only one sam ple per replicateplot was taken of fruit and soil. Duplicate laboratorysubsam ples were used for fruit and soil. Fru it for makingby-produc ts were picked from the 20 lb band -treated plotsan d were processed by the S unk ist Growers, Inc. plant inCoro na, Calif.; 1180 lb of mature treated fruit were pro-cessed on Jun e 10, 1975.Laboratory Processing. Soil samples were air dried ,pulverized in a mortar if necessary, and mixed in aTwin-Shell blender. Th e fruits were peeled (Gunth er,1969); the rind was chopped in a H obart food cutter an dpulp (oranges after rin d remov al) was sampled by cuttingout cylinders (Gu nther, 1969). All samples were stored a tabout -4 C until analyzed.Analysis. T he toxic residue s of aldic arb in biologicalsub stra tes are composed of aldicarb an d its sulfoxide andsulfone. All three of these compoun ds were determinedas a to tal residue by first oxidizing aldicarb an d its sul-foxide to the sulfone with peracetic acid and then de-termining total aldicarb sulfone by gas chromatography.All samples, except orange oil, were analyzed by themetho d furnished by Union Carbide Corporation, Sou thCharleston, W. V a., entitled A Method for the Deter-mination of To tal Tox ic Aldicarb Residues in Citrus Fru it,July 1975. T his metho d was satisfactory for soil samplesas well as the pla nt pa rts. Analysis of citr us oil utilizedthe Union Carbide method A Method for the Determi-nation of To tal Toxic Aldicarb Residues in Pe an ut Oil byGas Chromatography, February , 1973. Th e final de-terminations were made w ith a Tracor MicroTek MT-220gas chroma tographas described in the me thods except tha ta 1.8 m X 4 mm i.d. glass column, packed with 5 % R eoplex400 on 80/100 mesh Gas-ChromQ and operated a t 190 OCwith a carr ier gas (nitrogen ) flow rate of 80 mL /m in, w asused. Th e detector was a Melpar flame photometricdetector (FP D) incorporating a 394-nm filter specific for

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IWATA ET AL.B

1 00:i 2 4Dc--4MinutesFigure 1. Gas chromatographic responses (FPD) for: (A) orangerind fortified at 0.05 ppm with aldicarb, (B ) control rind, (C)orange pulp fortified a t 0.06 ppm with aldicarb, and (D) controlpulp. Extract injectedwas equivalent to 75 mg of rind and 100mg of pulp.sulfur-containing compounds. In our laboratory theReoplex column gave better separation of the aldicarbsulfone peak [the response results from the thermaldecomposi t ion product , 2-methyl-2-(methylsulfonyl)-prop ionitrile (K naak et al., 1966)] from early-eluting in-terference than the Carbowax column specified in themethod. Th e retention time for the Reoplex column was2.3 min. Chro matogra ms for rind and pu lp fortified at 0.05ppm with aldicarb prior to extraction are shown in Figure1.The minimum detectable levels for the analyticalprocedure used varied from 0.01 to 0.04 ppm and weredep end ent on the sub strate analyzed and th e daily vari-atio ns in the gas chrom atographic response. All valuesreported have been corrected for recovery as determinedfrom fortification of control samples with aldicarb priorto analysis. Recovery values for rind, p ulp, leaves, and soilwere 97 f 6,97 f 3, 96 f 6, and 87 f % , respectively.RESULTS AND DISCUSSION

Figure 2 shows the residue levels found in th e orangerind. In plot IV (20 lb/acre) detectable residues werefound in the 14-day samples and a maximum residue levelof about 0.25 ppm was reached a t about 45 days after soiltreatme nt. Following this there was a gradual reductiont o a bou t 0.1 ppm after 154 days. In plot 111(10 lb/acre)detectable residues appeared in th e 28-day samples andreached a peak of abou t 0.1 ppm at ab out 45 days aftertreatme nt. Residues were generally less th an half of tha tfor plot IV which received twice the trea tm en t rate. PlotI1 which received the same am ount as plot 111, bu t in tw otreatments, peaked at th e same level as plot I11 after th esecond treatment (71-day sampling), then dropped off.Rind residues for plot I trea ted a t 2.5 lb of AI per acre werealways below the detectable limit except for two of thethree 35-day samples th at contained 0.04 an d 0.05 ppm.Residues in th e pu lp (edible portion including juice andtissue) did not reach detectable levels in plots I, 11, an dI11 for any sample du ring the entire 154-day experimentalperiod. In plot IV detectable residues appeared in the pulpof the 28-day samples and a residue of 0.03 to 0.05 ppmpersisted from th e 52nd day to the end of the experimentalperiod (Table I).93 4 J. Agric. Food Chem., Vol. 25,No. 4, 1977

OL 20 40 60 80 IO0 I 120 I40 120DAYS AFTER SOIL APPLICATION

Figure 2. Total carbamate residues found in orange rind aftersoil trea tment with aldicarb (April 1974). Plots 11,111,and IVwere treated at 5, 10,and 20 lb of AI per acre, respectively; plotI1 was retreated on day 36 at 5 lb of AI per acre. The circles givethe mean value obtained from three replicate field plots whilethe vertical bars give the ranges of values found.Table I.Valencia Orange Pulp Obtained from Plot IV Treated(April 1974) t 20 l b of AI per Acre with Aldicarb

Total Carbamate Residues (ppm) of Aldicarb in

DaysReplicateftertreat-ment A B C Mean

7142 12835527 193113154

c0.02c0.02

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ALDICARB RESIDUES IN ORANGESTable 11. Total Carbamate Residues (ppm ) in Soil, Leaves, and Fruit af ter Soil Trea tmen t with Aldicarb (March 1975)"

10 lb of AI per acre (four-side ) 20 lb of AI per acre (four-side) 20 lb of AI per acre(two-side)1974b 1974b ~Subs trate Sample Range Mean mean Range Mean mean Range MeanSoil Pretreat

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IWATA ET AL.Table IV . Total Carbamate Residues (ppm) of Aldicarb in Navel Orange Rind an d Pulp 178 Days afterSoil Application

Treatment, Rind Pulplb of AIper acre A B C Mean A B C Mean2.5

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DIMETHOATE AND DIMETHOXON RESIDUESKnaak, J. B., Tallant, M. J., Sullivan, L. J.,J.Agric. Food Chem.Shaw,J. G., Espinosa,L. R., Hampton, R. B., J . Econ. Entomol.Tashiro, H., Beaver, J. B., J. Econ. Entom ol. 60, 1187 (1967).Tashiro, H., Chambers,D. L., Shaw, J. G., Beaver, J. B., Maitlen,

Westlake,W. E., Gunther, F. A, , Carman, G. E., Arch. Enuiron.14 , 573 (1966).63 , 1631 (1970).

Contam. Toxicol. 1 , 60 (1973).Received for review December 17,1976. Accepted March 11,1977.A grant-in-aid rom Union Carbide Corporation and supp ort bythe Citrus Advisory Board is gratefully acknowledged.. C., J. Econ. Entomol. 62, 44 3 (1969).

Residues of Dimethoate and Dimethoxon on Sweet Cherries Following AirCarrier Application

Ro bert W . Zwick, Ulo Kiigemagi,: and Gary J. Fields~ ~~~

Dime thoate was applied to sweet cherries a t two Oregon locations using both the emulsifiable concentrateand the w ettable powder formulations. Th e applications were made with an air carrier sprayer a t ratesranging from 1.23 to 2.50 lb of active ing redient/acre . Only traces of dimetho ate and its principalmetabolite, dimethoxon, were presen t at harvest, 28 to 35 days after treatm ent. To tal residues werereduced to levels below 2 ppm in 0 to 8 days after application. No differences in th e initial residuesor th e rate of disappearan ce were observed between the emulsifiable concentrate and wettable powderformulations. T his study indicates tha t dimethoate can be used for western cherry fruit fly control withoutexcessive harvest residues.

Dim ethoate [O ,O-dimethyl S-(N-methylcarbam oyl-meth yl) phosphoro dithoate] is registered on pome fruitsfor th e control of a variety of insect pests in th e UnitedSta tes and Canad a. Following investigations of Banham(1974) in C anad a, we evaluated efficacy of dime thoate forwestern cherry fruit fly (Rhagoletis i nd i f f e re ns Curran)control o n sw eet cherries in Oregon (Zwick et al., 1975) andfound that one application of dimethoate provided ex-cellent protection over an entire season. Presen tly, di-methoate is registered for control of cherry fruit fly inCanada bu t not in th e United States. We have beenattem ptin g to collect sufficient efficacy and residue dat ato sup po rt registration of this com poun d on cherries in theUn ited States. Since previous residue studies of MacN eilet al. (1975) and Zwick et al. (1975) were based on hy-draulic handgun applications which are not in generalcommerical use, we are presenting here the results ofdimethoate residue analyses resulting from air carrierapplications as would be applicable to commercial cherryorchards. In add ition, residues resulting from th e use ofa w ettable powder formulat ion are compared w ith thoseresulting from an emulsifiable concentrate application.MATERIALS A N D METHODS

Treatment and Sampling of Crop. In 1975 studieswere conducted in two eastern Oregon areas, Hood Riveran d T he D alles, both of which have commercial cherryacreages. Two rates of two dim ethoate formulations[Cygon brand, 2.67 lb of active ingredient (AI)/gal ofemulsifiable concentrate (EC) and 25% AI wettablepowder (W P)] were applied once in each area to severalvarieties (Bing, Royal Anne, Van) of sweet cherries.Applications were m ade with a Bertho ud V T 1500Modelair carrier spraye r calibrated to deliver 370 gal/acre (gpa)Mid-Columbia Exper iment Sta t ion, Oregon Sta teUniversity, Ho od R iver, Oregon 97031 (R.W.Z., G.J.F.)and the Dep artmen t of Agricul tural Chemistry, OregonSta te U niversity, Corvallis, Oregon 97331 (U.K.).

and 500 gpa in The Dalles and Hood River orchards,respectively. T he differences in total gallonage applied pe racre were due to the 26 f t rows and 1.40 mp h tracto r speedin T he D alles as compared w ith 20 f t rows and 1.36 mp hspeed in Hood River. Fan rp m, hydraulic pum p pressure,and discharge nozzling remained constan t for all appli-cations. Although th e dilution rates (lb of AI di-me tho ate/ 100 gal) for comparable plots were iden tical ineach location, the lb of AI per acre app lied were differentin each location due to the different total gallonagesapp lied (Ta ble I). Individu al plots were 3-12 trees in Th eDalles an d 4-10 trees in Hood River.App lications n each area were made within a week afterwestern cherry fruit fly had emerged. This was June 5 inTh e Dalles and June 9 in Hood River, at which time fru itwas abou t 0.5 in. in diameter. Abo ut 1 b random samplesof fruit, three per p lot at each sam pling date, were indi-vidually bagged in plastic containers an d stored at -10 "Cuntil analysis. Samples were taken 0 ,3 ,7 , 14, and 28 daysafter treatment and also at harvest. Con trol samples werefrom unsp rayed tree s a t each location.Residue Analysis. The analytical method used wasbased on that developed by Stellar and Pasarela (1972).T he fru it was subsampled in the laboratory as received,and randomly selected 100-g aliquots, were taken forextraction. In m ost cases the thr ee replicates taken werecombined, mixed well, and th en one sub sample taken. Onesubsam ple per replicate was taken from one plot a t eachlocation. Whole fruits were macerated with 400 mL ofaceto ne in th e presence of 50 g of an hyd rou s sodium sulfatefo r 5 min using an Omnimixer. The extract was recoveredby filtering with suction, and the extraction jar, pulp, an dfilter paper were washed with additional 50 mL of acetone.Th e acetone extract was concentrated to 100 mL on asteam bath, 100 mL of water added, and the aqueoussolution extracted with three 100-m L portions of di-chloromethane. Th e dichloromethane extract was driedwith 50 g of anhydr ous sodium sulfate and purified with3 g of activated charcoal (Nu char C-190-N). The absorbent

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