232 FLORIDA STATE HORTICULTURAL SOCIETY, 1967 THIABENDAZOLE, AN EXPERIMENTAL FUNGICIDE FOR FRESH CITRUS FRUIT1 A. A. McCornack and G. Eldon Brown Florida Citrus Commission University of Florida Citrus Experiment Station Lake Alfred Abstract The fungicide thiabendazole (TBZ) has given good to excellent control of fresh citrus fruit decay in experimental studies at the Florida Cit rus Experiment Station. Decay control with TBZ is better than that obtained with sodium o-phenylphenate (Dowicide A), diphenyl pads (2 per ventilated 4/5-bushel carton) or a com bination of these 2 fungicides. TBZ is consis tently effective for a longer period than sodium o-phenylphenate. Concentrations of TBZ as low as 250 ppm applied as a dip or flood have been effective in controlling decay. Concentrations of 500 to 750 ppm are probably the best range for use on Florida citrus fruit. Mold sporulation is in hibited by treating fruit with TBZ as a 1%- minute flood at strengths between 5,000 and 10,000 ppm. Introduction and Literature Review Decay of fresh Florida citrus is frequently high, especially in degreened fruit, and is the main competitive disadvantage of Florida citrus fruit in the domestic and world markets. Fun gicides approved by the Food and Drug Admin istration for use on fresh citrus fruit are help ful in reducing decay, but better fungicides are urgently needed to improve the keeping quality of Florida citrus fruit. Most decay of Florida citrus fruit is caused by 2 stem-end rot fungi, Diplodia natalensis P. Evans and Phomopsis dtri Faw., and by the green mold fungus, Penicillium digitatum Sacc. Blue mold, Penicillium italicum Wehrner and sour rot, Geotrichum candidum Ferr. occasion ally cause decay. Experimental work with thiabendazole (TBZ) has been in progress at the Florida Citrus Ex- Florida Agricultural Experiment Stations Journal Series No. 2826. lcooperative research of the Florida Citrus Commission and Florida Citrus Experiment Station. periment Station for the past 2 years. Chemi cally, TBZ is 2-(4'thiazolyl)-benzimiadole (1). TBZ is registered with the Food and Drug Ad ministration for use as an anthelmintic (2, 3). Crivelli (5, 6) published the first papers show ing the value of TBZ as a citrus fruit fungicide. Harding and Schade (7) incorporated TBZ into wax formulations to control Penicillium decay of navel oranges. Brown, et ah (4) reported that TBZ was effective in vitro against most citrus decay fungi. Post-harvest applications effectively controlled decay of degreened 'Valencia* oranges. A suspension of TBZ effectively controlled decay of Penicillium inoculated lemons (8). Experimental Methods Commercial procedures were followed as closely as possible. Variation in time of treat ment, methods of treatment, and concentration of solution were tested. Comparisons were made between TBZ and the Food and Drug Administration approved citrus fungicides, Dowi cide A (sodium o-penylphenate) and diphenyl (biphenyl) and the experimental fungicide 2- aminobutane (10). Most of the citrus fruit used in this experi mental work were obtained from the Citrus Ex periment Station groves, but commercial fruit were used when comparable fruit were not avail able at the Citrus Experiment Station. Fruit for all experiments were distributed at random into the desired number of lots for each experi ment and cull and off-grade fruit were removed before packing. The number of fruit per lot was determined by the size of the fruit, amount of fruit available, and the number of lots de sired. Lot size varied from 125 fruit for 'Dancy' tangerines to 80 for 'Ruby Red' grapefruit. Decay control with TBZ was tested using 'Hamlin,' 'Pineapple,' 'Valencia,' and navel (variety unknown) oranges; 'Marsh' and 'Ruby Red' grapefruit; 'Temples'; 'Dancy' tangerines and 'Murcotts.' Comparable experiments were usually replicated 4 times with each cultivator. Percentage decay for the same treatments within any 1 variety was averaged to obtain figures used in this paper. Since TBZ is relatively insoluble in water, aqueous suspensions of 50 to 10,000 ppm were
MC CORNACK AND BROWN: THIABENDAZOLE 233 applied to washed fruit. Treatments were either either stem-end rot or mold, was recorded at a dip or flood, varying from a momentary "in 1, 2, 3, and in some instances 4 weeks from and out" dip to a 6^ minute flood. Treatments picking. Treated fruit were examined for eviwith TBZ were not followed by a rinse. Dowicide dence of peel injury. A and diphenyl were applied using commercial practices (9). Dowicide A-hexamine was applied RESULTg DlscussI0N at the ambient temperature which was usually between 70 and 80 F. TBZ effectively controlled decay in 'Valencia' After fungicide application, fruit were dried oranges during the 1965-66 season. TBZ was and polished on horsehair brushes and waxed tested extensively in the 1966-67 season.on as with nonfungicidal Flavorseal. All fruit were many varieties of citrus as possible, using both packed in 4/5-bushel, ventilated, telescope-type, degreened and nondegreened fruit. All data can fiberboard cartons and held at 60 or 70 : F. not be reported in this paper, but enough will be Diphenyl pads were placed 2 to a carton, 1 below presented to show the decay control that can be and 1 on top of the fruit. Decay, classified as expected with TBZ. Table 1. Decay control with thiabendazole (TBZ) of degreened fhamlinf oranges. Average % total decay at 70 F1 Weeks from picking date No. Treatment 2 3 1. Check 2. 2 diphenyl pads (DP) 3. TBZ 500 ppm, 2-min. dip + 2 DP 4. TBZ 250 ppm, 2-min. dip 5. TBZ 500 ppm, 1-min. dip 6. TBZ 500 ppm, 2-min. dip 7. TBZ 750 ppm, 1-min. dip 8. TBZ 750 ppm, 2-min. dip 11.0 3.3 1.8 1.0 1.5 3.3 0.5 1.8 18.5 10.0 2.0 4.0 3.6 6.0 2.3 2.8 1 Average of 4 experiments.
234 FLORIDA STATE HORTICULTURAL SOCIETY, 1967 'Hamlin' oranges, Decay of degreened 'Hamlin' oranges, which is normally high, was con trolled more effectively by TBZ than by diphenyl pads (Table 1). Combining TBZ-treated fruit with 2 diphenyl pads did not result in more effective decay control than TBZ alone. Some variation resulted among the different TBZ treatments, but on the average, decay was re duced 85% and 80% at 2 and 3 weeks, respec tively. A 1-minute dip in TBZ at a strength of 750 ppm was the most effective treatment. 'Dancy' tangerines, Dowicide A-hexamine was not effective in controlling decay of 'Dancy' tangerines (Table 2). However, single treat ments with TBZ and 2-aminobutane (carbon ated) reduced decay by about 50%. When un washed fruit were dipped in 500 ppm TBZ for 2 minutes before degreening, then given a second treatment in the same solution following degreen ing and washing, the decay control was con sistently much better than a single treatment. At 3 weeks from picking, decay was reduced from 27.6% in the check lots to 4.1% in the lots given a double TBZ treatment. No change in degreening rate was noted due to this double treatment. 'Ruby-Red* grapefruit. Decay of nondegreened 'Ruby Red' grapefruit treated with TBZ or 2-aminobutane (phosphated) was much lower than that of untreated fruit (Table 3). At 3 and 4 weeks from picking at a holding tempera ture of 70 F, decay control obtained with 3- minute TBZ flood treatment was better than a 45-second flood. Decay control with diphenyl pads was inferior to the TBZ treatments. Cold storage of 'Valencia* oranges after TBZ Table 2. Decay control with thiabendazole (TBZ) of degreened 'Dancy1 tangerines. No, Treatment Average % total decay at 70 F1 Weeks from picking date 1 2 3 1. Check 4.4 14.8 27.6 2. 2% Dowicide A-hexamine, 2-min. dip 4.8 10.4 20.5 3. 1% 2-ABC2, 2-min. dip 1.8 6.1 13.6 4. TBZ 500 ppm, "in and out" dip 2.0 6.7 14.8 5. TBZ 500 ppm, 2-min. dip 3.3 6.1 13.0 6. TBZ 500 ppm, 2-min.dip, before and after degreening 0.4 1.3 4.1 Average of 4 experiments, 2-aminobutane (carbonated).
MC CORNACK AND BROWN: THIABENDAZOLE 235 Table 3. Decay control with thiabendazole (TBZ) of nondegreened 'Ruby Red1 grapefruit. Average % total decay at 70 F Weeks from picking date No. Treatment 3 4 1. Check 6.0 9.7 2. 2 diphenyl pads 3. 1% 2-ABP2, 2-min. dip 1.9 1.3 4.4 1.3 4. TBZ 500 ppm, 45-sec. flood 1.0 3.2 5. TBZ 500 ppm, 3-min. flood 1.0 1.9 Average of 4 experiments. 2 2-aminobutane (phosphated). treatment Two nearly identical experiments were completed with nondegreened 'Valencia* oranges to determine the value of TBZ as a fun gicide for fruit held in cold storage (Fig. 1). Fruit were dipped for 2 minutes at room tem perature in a suspension of 500 ppm TBZ. Treated fruit and check lots were held at 70 and 40 F for 10 weeks. The TBZ treatment reduced decay from 10.1% to 2.4% after 10 weeks storage at 40 F. After 2 additional weeks at a holding temperature of 70 F, the check lots had a total loss of 50.7% compared with 22.5% for lots treated with TBZ. Fruit held continually at 70 F had much more decay during the 10 weeks storage than the fruit held at 40 F. However, the rapid increase in decay that was observed when fruit stored at 40 F were moved to 70 F did not occur in fruit held con tinually at 70 F. Control of mold sporulation, Sporulation of Penicillium digitatum inoculated 'Valencia* oranges was prevented by concentrations of 5,000 and 10,000 ppm of TBZ applied as a 1%- minute flood within 3 hours of inoculation. Sporulation was not prevented when TBZ was NOS. 12 3 4 DECAY CONTROL WITH TBZ Fiff. 1. Decay of 'Valencia' oranges (1) stored for 12 weeks at 70 F; (2) dipped for 2 minute* in TBZ and stored for 12 weeks at 70 F; (3) stored for 10 weeks at 40 F and 2 additional weeks at 70o F; (4) dipped for 2 minutes in TBZ and stored for 10 weeks at 40 F and 2 additional weeks at 70 F.
236 FLORIDA STATE HORTICULTURAL SOCIETY, 1967 Table 4. Comparison of decay control between commercial and experimental citrus fruit fungicides* No. Treatment No. of experiments Avg. % decay1 1. Check 58 13.5 2. Dowicide A-hexamine 2%, 2-min«dip 44 6.3 3, Diphenyl pads, 2 per 4/5 bu. carton 37 6.6 4. Dowicide A-hexamine, 2% + 2 diphenyl pads 29 4.5 5. 2 2-AB 1%, 2-min. dip 54 4.1 6. TBZ3 500 ppm, 2-min dip 54 3.7 Two weeks frompicking date, holding temperature of 70 F. 2 2-aminobutane in carbonated or phosphated form (experimental). 3 Thiabendazole (experimental) applied 24 hours after inoculation. The value of TBZ for controlling mold sporulation was first observed in California (J. W. Eckert and M. J. Kolbezen, unpublished data). The average decay control obtained with Food and Drug Administration approved and experimental fungicides for the 1966-67 season is given in Table 4. Experimental results with 'Hamlin,' 'Pineapple/ 'Valencia,' and navel oranges; 'Temples'; 'Marsh' and 'Ruby Red' grapefruit; 'Dancy' tangerines and 'Murcotts' are included in these averages. TBZ applied as a 2-minute dip at a concentration of 500 ppm was the most effective fungicide. TBZ treatments consistently resulted in bet ter decay control than diphenyl pads or the Dowicide A-hexamine treatment on all varieties of citrus on which comparative tests were made. There was no evidence that gloss was affected by any of the TBZ treatments. No peel injury due to this fungicide was observed. Procedures to obtain a Food and Drug Administration clearance for the use of TBZ on citrus fruit are in progress. LITERATURE CITED 1. Anonymous. 1965. Biological and chemical properties of thiabendazole. Merck, Sharp, and Dohme Research Lab oratories, Rahway, New Jersey. 2. Federal Register, March 22, 1967. Thiabendazole par. 121.260. 3 Federal Register, March 27, 1967. Thia bendazole par. 121.1158. 4. Brown, G. Eldon, A. A. McCornack, and John J. Smoot. 1967. Thiabendazole as a postharvest fungicide for Florida citrus fruit. Plant Dis. Reptr. 51: 95-98. 5. Crivelli, G. 1966. Tests on the fungistatic activity of 2-(4'-thiazolyl)-benzimadazole on the Penicilliums of oranges. II Freddo XX, No. 3, 25-29. 6. 1966. Testing of Sanguinello orange preservation with 2-(4'-thiazoly)-benzimadazole. II Freddo XX, No. 5, 17-21. 7. Harding, Paul R., Jr., and John E. Schade. 1967. Testing t.hiazendazole in resin-solvent and wax-emulsion coatings for control of Penicillium digitatum in navel or anges. Plant Dis. Reptr. 51: 51-53. 8 1967. Wax emulsion additives for control of storage decay in lemons. Plant Dis. Reptr. 51: 781-784.
GRIERSON AND HAYWARD: MARKETING TESTS 237 9. Hopkins, E. F. and A. A. McCornack. 1959. Methods for the control of decay in oranges. Citrus Mag. 22: 8, 10-11, 30-31. 10. McCornack, A. A. and G. Eldon Brown. 1965. 2- aminobutane a possible new fungicide for decay control of Florida citrus fruit. Proc. Fla. State Hort. Soc. 78: 288-292. SIMULATED MARKETING TESTS WITH PREPACKAGED CITRUS W. Grierson and F. W. Hay ward Materials and Methods University of Florida Citrus Experiment Station Lake Alfred Abstract A preliminary holding test using lemons in dicated that differences in decay due to the de gree of ventilation of consumer packages persist, although these packages are enclosed in bagmaster cartons for as long as 4 weeks. Simulated marketing tests were used to study keeping qual ity of 5 types of citrus fruits in 5 types of consumer package, with and without fungicides. Decay was least in the Vexar net bag, followed by an experimental 144-hole, 2-mil polyethylene bag. 2-Aminobutane used in vapor form, either as a prefumigation treatment for fruit to be bag ged or as an aerosol spray applied to shrinkfilm trays prior to packing, provided more consistent decay control than did diphenyl. The most successful combination was prefumigation with 2-aminobutane followed by packaging in Vexar net bags. Average losses for fruit so treated were 0.2% at simulated "retail sale" and 5.1% after 1 week under simulated "fruit bowl" conditions. Nevertheless, even at these low levels of decay, the "retailer" had 2% spoiled packages and one-third of the "fruit bowls" had one or more rotten fruit in the week after simulated "purchase." Introduction A report to this Society last year (4) de scribed the Citrus Experiment Station's continu ing program of research on response of various citrus varieties to consumer packaging. A sec ond season's work is reported here. Review of literature and methods used are not restated, except for additional material or when methods were changed. Florida Agricultural Experiment Stations Journal Series No. 2837. Fruit: Varieties and Sources 'Dancy' tangerines and 'Orlando' tangelos from commercial groves and 'Marsh' grapefruit and 'Murcotts' from the Citrus Experiment Sta tion groves were prepared for packaging in the Experiment Station packinghouse. 'Bearss' lemons and 'Temples' were commercially grown and packed, in cartons and wire-bound boxes, respectively, prior to being procured for these studies. In every case, care was taken to see that the fruit received approximately the same treatments that they would have received in commerce. Fruit Preparation Standard packinghouse equipment was used. All fruit was washed, dried, and treated with Flavorseal 93, a commercial fruit wax. In addi tion, the 'Temples' received a Dowicide-A hexamine fungicidal treatment in the packinghouse and 'Bearss' lemons had been treated with diph enyl during preparation for market. Two fungicidal treatments were used in connection with the packaging and simulated marketing experiments. Diphenyl was used as diphenyl pads, containing a total of approxi mately AY2 grams of diphenyl, in each master container. Unlike the previous season, 2-amino butane (2-AB) was not applied by commercial packinghouse methods. Much consumer packag ing is done in warehouses or supermarkets, re mote from the citrus packinghouse. Efforts were therefore made to develop methods which might also be suitable for packaging at stores and terminal markets where packinghouse equipment is not available for fruit treatment. When 2-AB was used with shrinkfilm trays, 2-AB (free base) was applied to the trays prior to packing using an aerosol can loaded with 2-AB and Freon as a propellant. The cans were weighed before and after each experiment. Treated trays were analyzed (6) for 2-AB to determine the amount of fungicide absorbed per package. The under side of each tray received a 2-second spray