36 STATE HORTICULTURAL SOCIETY, 1963

RUMPLE OF -ITS EFFECTS ON FRESH FRUIT, LEMONADE CONCENTRATE, AND PEEL OIL

L. C. Knorr, R. W. Olsen, and J. W. Kesterson and are of dubious parentage. Also, there is a Florida Citrus Experiment Station lack of know-how about the growing of lemons, much having been forgotten since lemons were Lake Alfred last an economic crop in the State. It is not surprising, therefore, that problems should It must be puzzling to economic botanists arise in the course of this new beginning. And that Florida, the world's largest citrus-growing one of these problems is rumple. area, should be dependent on lesser producing The purpose of this paper is to familiarize areas for its lemons. This is all the more strange citrus growers with rumple and to describe effects because climatically nothing has changed since of this disease on fresh fruit, on the making of the days when Florida produced its own lemons lemonade concentrate, and on the recovery of peel and enough more to ship some 140,000 boxes oil. annually. True, the Great Freeze of 1894-95 wiped out most of the State's groves, but that would Symptoms not have prevented growers of lemons from mov Rumple, as the name implies, is an irregu ing to warmer parts of the State along with larity; it affects the rind and renders lemons growers of oranges, tangerines, and grapefruits. worthless as fresh-fruit. At maturity, affected Rather, the demise of lemon growing in Florida lemons look as if worms are tunneling through came as a result of competition from California, the peel (Figure 1A). In its earliest stage, as where improved methods of harvesting and curing seen in midsummer, rumple is barely visible as a provided the housewifewith lemons she preferred chafing of the surface; later, as fruits mature, because of their small size and hardiness. In con affected areas appear as sunken, walnut-colored trast, Florida lemons, grown to maturity for furrows. All sides of the fruit are affected, pro color break, were oversized, and their lack of tected as well as exposed. Rumple is to be found hardiness was the despair of handlers from ship throughout the tree, though at times it is re per to consumer. stricted to fruits on single limbs. Now, suddenly after 60 years, Florida-grown lemons are back in favor. Already there are some Oil glands in the furrows are normal in size 6,000 acres planted and within the next 3 years, and shape but are dark brown in color; when as present plans materialize, the acreage should sectioned, they are seen to be filled with a black be nearly doubled. ish gummy liquid (Figure ID). There have been two leaders in this revolution: The above symptoms are those that showed the housewife who likes her lemonade in the same up yearly until 1962, when a much more con way shedoes her juice, i.e., in 6-ounee spicuous disfigurement of the rind appeared cans of frozen concentrate, and the processor who rather suddenly. Shortly before harvest time, finds Florida with its low production costs a the sunken areas described above turned necrotic profitable place to grow lemons. No longerare old and involved large areas of the rind in a black, arguments against Florida-grown lemons valid; in dry rot (Figure IB and C) resembling anthrac- fact, large-sized fruits are now a boon, and lack nose lesions. Over half (58%) of the affected of hardiness ceases to be a problem when lemons fruits harvested that year from the Lemon Va are processed within a day or two of picking. riety Trails, Avon Park, showed second-stage in This sudden interest in lemons has, in a way, volvement. caught industry unprepared. For one thing, there At first, oil glands in the necrotic areas re is a shortage of budwood, and because quaran main dome-shaped, but after several weeks in tine regulations prevent the importation of vege storage they collapse and impart a pockmarked tative parts of citrus, budwood requirements must appearance to the sunken lesions. be eked out of the few varieties remaining today When a lesion is sectioned, whether of the and from trees that occur mostly in dooryards necrotic or non-necrotic type, it is seen to involve the albedo but not the flesh. Even after 4 weeks Florida Agricultural Experiment Stations Journal Series No. 1720. in storage, there is no progressive spread of the KNORR, OLSEN, KESTERSON: RUMPLE OF LEMONS 37

gummy substance in oil glands of fruit affected by first-stage rumple. 38 FLORIDA STATE HORTICULTURAL SOCIETY, 1963

trouble over the rind nor is there any greater nificant. Of the 117 trees represented in the susceptibility to secondary rots. sample, only 9 showed large fruits to have the Rumple is not to be confused with oleocellosis same amount of rumple or less rumple than did (1); in rumple, oil glands remain intact and walls small fruits. The over-all percentage distribu of sunken areas are V-shaped with depressions tion was 6.1% rumple on sizes 216 and smaller, forming a network of grooves, whereas in oleo and 14.9% on sizes 200 and larger. cellosis, oil glands are shrunken and walls lead There is a highly significant difference in the down to shallow, disconnected, irregular plate-like amount of rumple according to variety (Table 1). depressions. Rumple, to some extent, resembles However, there is also a highly significant dif creasing as described in oranges (2) but there is ference in the amount of rumple between plots no splitting of the albedo when affected areas are of the same selection; this suggests that location squeezed; neither is there a greater susceptibility in the grove or some other variable is associated to invasion by green and blue molds. There is with the appearance of rumple. also a resemblance to peteca (3), but the latter It is obvious from an examination of Figure shows a reddish discoloration in the albedo and 1 (A, B, and C) that rumpled lemons cannot develops progressively in storage whereas rumple be sold as fresh fruit. That they might also be does not. detrimental in the making of concentrate for lemonade and to quality and quantity of oil Importance seemed plausible. To determine whether there was actually an effect of rumple on juice charac When first observed in 1956 (4, 5), rumple teristics, a comparison was made in 1959 between seemed to be of only academic interest, but by juice obtained from 10 boxes of first-stage rumple- 1962, it had come to assume considerable eco diseased lemons and from 10 boxes of sound fruit. nomic importance. In terms of the State's entire The lemons, after being weighed, were processed production, perhaps only 1% of the lemon crop using a FMC In-line Extractor with .040" long is affected, but in individual groves the amount type strainer tubes, 7/16" long restrictors, flush may be as much as 10%. beam, 3" standard cups, standard split rings A detailed count of affected fruits was made 5/8" long and short upper cutters. The juice in 1962, using trees in the lemon variety planting was finished using a modified FMC No. 35 at Avon Park. In this grove, where 40 selections juice finisher with a .027" screen and head clear of lemons have been under test to find varieties ance approximately .015". Yield from rumpled producing high yields of acid per acre and su lemons gave 4.85 gallons of juice per 90-lb. perior grades of peel oil, each selection of lemon box and from sound fruit 4.60 gallons, but was topworked in 1954 to 13 thirty-year-old this difference in yield is not considered sig grapefruit trees on rough-lemon rootstocks. Lem nificant because of the small quantity of fruit on tops made estimable growth and are now pro used. The juice from rumpled lemons had an ducing an average of from 4 to 8 boxes of fruit acid content of 5.36% and a Brix of 6.5° and per tree, depending on variety. However, der from non-rumpled lemons, 5.64% and 6.7°, re spite this production, 9% of the total 1962 crop spectively. was rendered worthless as fresh fruit by rumple. Within individual varieties, the amount of rumple Four packs were made from the juice of each varied from a low of 0.6% to a high of 37.9%. of the 2 batches of lemons. One pack consisted Table 1* gives the percentage of rumple found of the raw juice, 1 with sugar added to make in each of the 40 varieties, and also the percent lemonade, 1 with sugar and Sicilian oil (1 ml per age of first-stage vs. second-stage rumple. The gallon) added, and the last with sugar and oil total crop of 3 randomly selected trees of each (made from the same fruit) added—giving a variety was used in arriving at the above per total of 8 packs for the 2 classes of fruit. centages. When these packs were subsequently tested by An analysis of data relating rumple to size of organoleptic means, the results showed, rather fruit shows that large fruits (sizes 200, 176, 150, surprisingly, that lemonade concentrate made 126, and 100) developed 2^ times more rumple from rumpled fruit was no different from that than did small fruits (sizes 216, 250, 288, and made from sound fruit. 324). This difference proved to be highly sig- Though the presence of first-stage rumple had no adverse effect on juice, it was thought *Due to space restrictions, Table 1 has been omitted from likely to have an influence on the quality and the printed presentation; copies, however, may be obtained by writing the authors. quantity of peel oil since oil glands were ob- KNORR, OLSEN, KESTERSON: RUMPLE OF LEMONS 39 viously affected (Figure ID). Accordingly, peel and the product compared favorably with that oil was obtained from the above-mentioned 10 made from sound fruits. boxes of rumpled fruit and from 10 boxes of sound Analysis of the oil from fruits affected by fruit, using the same FMC In-line extractor. Both second-stage rumple showed no commercially sig batches of oil were tested for specific gravity, re nificant differences in comparison with oil from fractive index, optical rotation, aldehyde content, healthy fruits. Both oils possessed a similar light- evaporation residue, and ultra-violet spectrum. yellow color. In view of other data in Table 2, Results of these oil analyses appear in Table column B, it is clear that for all practical pur 2, column A. Rumple produces no harmful effects poses, the oils are equally acceptable. Though on quality of peel oil nor on quantity of recover second-stage rumple appears to affect oil glands, able oil, contrary to expectations. yield of oil is not reduced. All physical and chemi The above tests were run on fruits affected cal properties of oil from rumpled fruit meet the by first-stage rumple. When in 1962 the new requirements of the U. S. Pharmacopoeia, and manifestation of second-stage rumple appeared, organoleptically the oil is considered to be of good it was thought that the more severe necrosis quality. might affect quality of juice and peel oil. To test Results reported above are based on fruits this assumption, 13 boxes of lemons affected by involved with first- and second-stage rumple. If, second-stage rumple were juiced and the resulting in the future a more serious involvement appears, lemonade concentrate compared with concentrate the effect of rumple on juice and peel oil will made from 13 boxes of sound fruit. Cold-pressed have to be re-assessed. oils from these 2 batches were also compared, using the same tests as previously described. Distribution Despite serious involvement of the rind by second-stage rumple, no harmful effects were While rumple can usually be found in trace noted in the concentrate made from such fruits, amounts wherever lemons are grown in Florida,

Table 2. Physico-chemical properties of cold-pressed lemon oil produced from fruit with and without rumple.

A B Run No. With rumple Without rumple With rumple Without rumple Date of processing 10/15/59 10/16/59 11/29/62 11/29/62 Yield of oil--lb./ton fruit 3.05 3.15 2.50 2.50

Specific gravity 25° C/25° C 0.8491 0.8493 0.8482 0.8489

Refractive index N^° 1.4741 1.4743 1.4743 1.4744

Refractive index 10% dist. N^° 1.4727 1.4727 1.4730 1.4730

Difference 0.0014 0.0016 0.0013 0.0014

Optical rotation oC"* +65.01 +65.21 +64.66 +64.66

Optical rotation 10%, dist. o^5 +63.98 +64.38 +61.86 +61.86

Difference -1.03 -0.83 -2.80 -2.80

Aldehyde content - % 3.24 3.61 2.79 2.79

Evaporation residue - % 1.86 1.94 2.24 2.70 U.V. spectrum Mu log E?An5 ? iuu mi CD 0.350 0.440 0.340 0.420 Peak 0.760 0.900 0.608 0.760 Mu 315.0 315.0 313.5 313.0

BURDITT AND REED: RUST MITE 41

Microscopic examinations of affected rind used safely in the making of frozen concentrate have so far failed to demonstrate a culpable for lemonade. Rumpled fruits can also be used microorganism, and isolations yield only the for the recovery of oil since, for all practical fungi usually found on fruits as surface con purposes, the resulting product is not affected taminants. in quality or yield.

Control Acknowledgments

Though rumple causes no harm to lemons The authors are indebted to Minute Maid destined for the canning plant, it must be con Corporation for providing the land, grove care, trolled if lemons are to be sold as fresh fruit. and help needed in operating the varietal lemon Rumple may be avoided by picking fruits while trials at Avon Park. To Dr. A. E. Willson, Vice still immature. This practice should work no President, Research and Development Division, hardship; rather it is to be preferred since 1) it acknowledgment is made for assistance in analyz provides small-sized fruits that are so popular ing the data on yield. To Mrs. Harriet Long, ap with the housewife, and 2) it yields lemons that, preciation is expressed for providing photographs when properly cured, are more resistant to stor A, B, and D. age breakdown. These remedies will enable the lemon grower LITERATURE CITED to cope with rumple until such time as the cause 1. Fawcett, H. S. 1937. Citrus diseases and their control. of rumple is established and the disease can be McGraw-Hill Book Company, Inc., New York. 656 p. 2. Haas, A. R. C. 1950. The relation of phosphorus to prevented. creasing and puffing in Valencia oranges. California Citro- graph 35: 277-278, 298-300. 3. Klotz, L. J. 1961. Color handbook of citrus diseases. University of California Press, Berkeley. 75 p. Conclusion 4. Knorr, L. C. 1958. Finding the best lemon for Florida—a report of progress. I. The growing of lemons in Rumple is a rind breakdown that disqualifies Florida: Historical, varietal, and cultural considerations. Florida State Horticultural Society Proceedings 71: 123-128. lemons for the fresh-fruit market. However, 5. Knorr, L. C. 1959. Selecting lemons for Florida production. Florida Agr. Exp. Stas. Ann. Rept., p. 246. fruits affected by either the first or second stage 6. Russo, F. and L. J. Klotz. 1963 Wrinkle rind of of rumple, as described in this report, can be lemons in Sicily. California Citrograph 48: 264.

DAMAGE CAUSED BY ACULUS PELEKASSI KEIFER, A RUST MITE ON CITRUS

A. K. Burditt, Jr., and D. K. Reed most severe case of citrus rusting he had ever seen." However, in a discussion of the subject Entomology Research Division in December, 1962, Fleschner indicated that both Agric. Res. Serv. U.S.D.A. A. pelekassi and P. oleivora were present and Orlando that he was not sure which species caused the rusting. In 1961 a second species of rust mite, Aculus Distortion of leaves on terminal growth of pelekassi Keifer, was found on citrus in Florida citrus seedlings, first observed in laboratory colo (Burditt et a£., 1963). Inspectors from the Flor nies of rust mites at the Horticultural Field Sta ida Division of Plant Industry initiated surveys tion of the U.S.D.A., Orlando, Florida, late in for this species in April 1962 (Denmark, 1963) 1961, was subsequently associated with large and found it in over 50 citrus nurseries in the populations of A. pelekassi under greenhouse con northeastern and central part of the State. A. ditions (Burditt, 1963). This type of injury first pelekassi was also found in a few citrus groves, appeared as a crinkling of infested leaves, but generally in mixed populations with the citrus in severely damaged leaves the sides were twisted rust mite (Phyllocoptruta oleivora (Ashmead)). inward. Such damage could easily be distin A. pelekassi has been reported from Greece, guished from aphid injury, which causes the ends Thailand, Japan, Italy, and Sicily (Keifer, 1962). of the leaves to be coiled in a spiral form. How C. A. Fleschner (Keifer, 1959) stated that dam ever, injury caused by A. pelekassi may be con age to mandarin (Citrus reticulata) "was the fused with symptoms of some virus diseases of