Agrártudomány | Növénytermesztés » Occurrence and Identification of Preharvest Fruit Blemishes in Florida Citrus Groves

Proc. Fla State Hort Soc 91:78-81 1978 OCCURRENCE AND IDENTIFICATION OF PREHARVEST FRUIT BLEMISHES IN FLORIDA CITRUS GROVES1 L. G ALBRIGO University of Florida, Institute of Food and Agricultural Sciences, Agricultural Research and Education Center, P.O Box 1088, Lake Alfred, FL 33850 Abstract. Various fruit blemishes caused by climatic con ditions, insect and mite feeding, fungal invasion, spray treat ments, and nutritional deficiencies or excesses occur during a typical growing season in Florida citrus groves. The final appearance of an injury on mature fruit results from the interaction of the initial injury with subsequent growth and development of the fruit. Based on final appearance, pro cedures are presented for identifying the cause of blemish and the time of its initiation. Included are recommendations for precautionary measures to minimize fruit blemishes for fresh market fruit. Most packinghouses average 40% eliminations and some lots of fruit brought to packinghouses in

the past have run 70 to 80% eliminations (16). Most of the blemishes which cause elimination occur prior to harvest. Fruit with a high pack-out potential is basic to a successful fresh fruit opera tion. This has become more important in recent years be cause of increasing production and packing costs without a proportionate increase in fresh fruit prices. Packinghouse cost per packed box can be reduced up to $0.06 for every 10% increase in pack-out (41). Grierson (15) and Abbitt et al. (1) have presented information about the positive effect increased pack-out has on grower profits. The first step toward improving pack-out is to have a better understanding of the causes of the various kinds of fruit blemishes and of the measures required for their pre vention. Blemishes can be caused by climatic factors, insect and mite injury, pathogens, spray burns, and nutritional maladies (Table 1). The compiled list includes over 60 separate disorders. Where known, the time of occurrence is

presented, and references are given to publications con taining the latest information on each type of blemish. Al though the majority of the disorders listed seldom occur, many commonly occur and cause reduction in fresh fruit pack-out each year. These include wind scar, hail damage, green color, citrus rust mite injury, scale spots, melanose, scab, greasy spot, spray burns, and splitting. Over a number of years, certain key criteria have been found useful to determine the probable cause of a blemish. Most important is the appearance of the blemish. Many blemishes have characteristic damage patterns, color, rough ness, etc. that can be used for diagnostic purposes The time of injury can often be determined from the appearance of the blemish at harvest. Oftentimes, this is the first time the grower or packer notices the disorder. The depth of the injury is also important. Either hail or chewing insects will cause deep wounds. Citrus rust mite, spray burns, and wind scar result in

very shallow injury. When injured areas are raised rather than depressed, it is usually an indication of a fungal pathogen; i.e, scab and melanose. However, not all pathogen-associated blemishes are raised. For example, greasy spot does not cause raised lesions. Early Alternaria induced lesions on tangerines are initially raised but later develop into pockmarks due to the loss of corky tissue. The cause of a blemish can be indicated by the ab normal color of the rind. Blemishes which are dark to light brown involve peel necrosis and occur late in the fruit de velopment period. Some disorders result in rind areas greener than normal as in delayed color break, scale spots, green stink bug feeding, greasy spot, and regreening. This usually means that chlorophyll synthesis was stimulated by a toxin or gibberellin synthesis (26) or that chlorophyll breakdown was inhibited (22, 29). The cause of a blemish can also be indicated by its specific location on the fruit. For example, greasy spot

(pink pitting) occurs only between the oil glands because it de stroys only a limited number of cells beneath the stomates (45). Conversely, rust mite usually causes injury over the en tire surface (9), however, on grapefruit, late rust mite injury also can be located mostly between the oil glands (21). When this happens it may be difficult to decide whether the blem ish was caused by rust mites or greasy spot. The observation of one or more small punctures near the center of a blemish area, especially when there is necrosis, is good evidence of insect feeding (8) or thorn damage. Evidence for the cause of injuries on the fruit can be found in the position of the injury on the fruit as it hangs on the tree. Spray burns from concentrate spray are usually on the exposed surface. The bottom of the fruit will show spray burns if dilute sprays were used and the drip con centrated the spray material. By maturity the damaged areas may not be positioned the same as when the spray was

applied. In the spring, the stylar end of the fruit tends to be uppermost and hence, more exposed. As the fruit en larges and drops down, the stylar end becomes the bottom of the fruit. The exposed part of the fruit in the spring later becomes turned toward the inside of the tree as it drops down from increasing weight during development. Certain other disorders characteristically occur on the stem or stylar ends of the fruit (2, 3, 7, 13, 33, 34) and should not be confused with spray burns. Location in the canopy of the affected fruit also can provide valuable information in determining the causes of blemishes. If the affected fruit are predominately on the sun-exposed side of the tree, damage may be from spray burns associated with climatic stress or damage caused by climatic stress alone. Damage to fruit located only at the top or inside of the tree canopy may indicate poor spray coverage, and damage only on bottom fruit may indicate fertilizer or herbicide contact burn. Many

surface injuries to citrus fruits are emphasized by the development of a wound periderm that forms after injury (9, 11). Sometimes, as the fruit continues to grow, the dead tissue above the periderm bleaches and breaks into patches. With very early injury the wound tissue is com pletely sloughed off before fruit maturity (9) whether in juries are shallow, such as those caused by rust mite, or deeper injuries such as hail damage. Therefore, the degree o£ bleaching, patching, and sloughing is a guide to how Information about cultural practices and unusual cli matic or other occurrences can help in determining the cause of a disorder. Suspected spray or herbicide burns are often confirmed by examining the list of spray materials used and their time of application. Climatic stress periods, contaminated water supplies or spraying errors can often ^Florida Agricultural Experiment Stations Journal Series No. 1472 consideration blemish appearance, blemish location on the fruit, blemished

fruit location on the tree, and spraying early the injury occurred. 78 account for the occurrence of blemishes. After taking into Proc. Fla State Hort Soc, 91: 1978 Table 1. List of fruit blemishes identified in Florida citrus groves Included also are the causal agents, season of occurrence and some litera ture references containing pertinent information about each disorder. Causal category Injury name Cause Season first appears Reference no. Climatic induced wind scar thorn punctures hail damage creasing splitting sun scald freeze injury Pineapple pitting poor color or delayed color break regreening winds > 10 mph wind & thorns hail early spring 4, 11, 26, 27, 38 summer on 27 27, 38 23, 36, 38 Insects (chewing mouthparts) Insects & mites (piercing mouthparts or ovipositor) granulation & drying crickets grasshoppers katydids thrips leaf miners pink scavenger worm orange dog citrus rust mite scale spots plant bugs green stink bug spots mealy bugs

broad mite Texas citrus mite fruit flies leprosis coffee bean weevil Fungal induced melanose scab Alternaria brown spot greasy spot (pink pitting) flyspeck lime anthracnose sooty blotch Alternaria black rot brown rot Other pathogens Phytotoxic materials algal disease bacterial canker (no longer in Florida) leprosis ? ? sun radiation cold temp. ? chlorophyll retention warm temp, stimulate chlorophyll synthesis ? Hapithus agitator Schistocerca americana Microcentrum rhombutfolum Anaphothrips orchidii mining insects Pyroderces rileyi Papilio cresphontes Phyllocoptruta oleivora armored scales Leptoglossus sp. Nezara viridula Pseudococcus citri Hemitarsonemus latus Eutetranychus banski Mediterranean, Caribbean oviposit in mature fruit Brevipalpus australis false spider mite Araecerus fasciculatus oviposit in mature fruit Diaporthe citri Elsinoe fawcetti Alternaria citri Mycosphaerella citri Leptothyrium pomi Gloeosporium limetticola sooty-mold complex Alternaria citri

Phytophthora citrophthora parasitica Cephaleuros virescens Xanthomonas citri virus + mite ? Nutritional boron toxicity chelate burn granular fertilizer burn application nutrient sprays spreader use with dew still on fruit Pesticides copper toxicity Difolatan copper-oil copper-lime-sulfur (historical) oil blotch sulfur sulfur-oil oil + ethion, trithion, zineb or chelates trithion dinitro (historical) GA burn arsenic toxicity 2, 4-D sprays Growth regulators Herbicides Nutritional Unknown Mechanical paraquat 2, 4-D copper deficiency boron deficiency high Ngreen fruit splittinglow K pitting of grapefruit rumple of lemon harvester damage equipment damage Pvoe. Fla State Hart Sgc 91- 1978 sprays sprays any time early summer fall summer-fall winter late fall fall 19 spring late season early spring spring 12 spring spring spring-summer anytime 21 21 21 21 21 9, 21, 27, 38 21, 38 8, 21, 38 21 21, 27, 38 21 21, pers. obs summer late spring to late fall summer on summer on

summer on spring, early summer spring spring mature fruit sprays sprays sprays sprays sprays gibberellin k+ sprays sprays direct sprays direct sprays sprays low copper low boron high fertility low K ? ? mechanical harvesting cultivation, spraying 3, 5, 26 21 20 21,38 21, 27, 38 mature fruit 50 spring spring spring 26, 27, 38 26, 27, 49 48 46 summer spring summer fall 27 26,27 27 27 45 27 mature fruit mature fruit spring 27 summer 25, 27 spring spring-summer anytime 27 spring-summer anytime spring-summer 26,27 47 27, 38 31 pers. obs 38 sprays sprays 10 24,27 16,40 3,7 summer or fall spring-summer spring-summer spring-summer after August no longer used fall spring fall-winter summer summer spring spring fall fall mature fruit color break spring anytime 38 26, 38, 42 42, pers. obs 14, 16, 19 39 26, 38 30, pers. obs 27, 38 26 pers. obs 26 27, 26, 22, 10, 38, 27 38 27, 38 26, 29 28 pers. obs pers. obs pers. obs equip. 79 practices, it is

usually possible to successfully identify the cause of fruit bJemish.es These indicators can then be used to identify blemishes in order to avoid repetition of similar problems in subsequent crops. There are several steps the grower can take to avoid losses from peel blemishes in fresh fruit blocks. The first major consideration is that only 1/10 of the orange crop and i/2 of the total grapefruit crop are used annually in fresh fruit channels. Considering this, each grower should select an appropriate number of grove blocks, based on good past histories of high pack-out, for a fresh fruit program. These are likely to be mature groves with wide driving middles. Large trees are less likely to have a high incidence of wind scar, and wide middles will minimize damage to lower fruit from equipment. Hedged rows across prevailing wind direc tions will usually result in lower wind scar damage (4). Cultivating across the grove, traveling tight cross rows, is a practice that leads to heavy

damage to lower fruit. All blocks selected for fresh fruit should receive a moderate fertilizer program to avoid green color, rough peel, and accentuation of blemish problems (29). This type of program will not adversely affect yields. A well managed irrigation program will avoid prolonged dry or wet periods which also con tribute to many peel disorders (3, 5, 7, 17, 29). Of vital importance in minimizing blemish losses after Uniform and adequate soil moisture is particularly im portant in order to avoid several stress-related blemishes (3, 7, 17, 34, 44). The grower can also reduce handling losses, particularly on mandarins, by applying ethrel preharvest to reduce plugging and improve color of early harvested fruit (14). The ethrel may also reduce decay due to less degreening time being required. Maintenance of good fertility is important also since low N and K fertility can lead to increased fruit plugging at harvest (29). This present paper includes some idea of the magnitude of

the citrus blemish problems in Florida and blemish identification. The need for improved blemish prevention in Florida citrus groves is obvious. Many blemishes can be prevented by grower caution and sound practices. The grower should consult the current Florida Citrus Spray Guide (14) for the latest control recommendations for in sect and disease problems. Better practices on fewer acres would save Florida growers money and increase profits (1). Spraying fewer acres for fresh market also would reduce use of cosmetic sprays intended primarily to control fruit surface blemishes thereby reducing the pesticide impact on Floridas environment. Literature Cited blocks are selected is adequate pest monitoring and spray scheduling. Blocks should be examined frequently for in sects and mites that can cause blemishes. Even citrus rust mite can be adequately controlled on the basis of a careful and frequent monitoring program which will avoid un Abbitt, B., J O Whiteside, and L G Albrigo

1978 A comparison of spray costs and fruit pack-out. Citrus and Veg Mag 41 (7): 10, 14, 36, 38. Albrigo, L. G 1972 Distribution of stomata and epicuticular wax on oranges as related to stem end rind breakdown and water loss. /. Amer Soc Hort Sci 97:220-223 necessary sprays. Of particular importance is the timing of fungicide sprays in fresh fruit blocks (14, 47). This can be accomplished even with a large number of grove blocks and minimum amount of spray equipment if the fresh fruit blocks are predetermined and given priority. Processing fruit blocks can be sprayed at the beginning and end of the time period considered adequate for control. Other scheduling and spray procedures that can im prove pack-out include using appropriate equipment to provide adequate coverage. Slower spray speeds and dilute sprayers should be used in fresh fruit groves when equip ment options are available. Spray material sequences that will lead to pest upsets should be avoided. A recent example of

pest upsets is the increased incidence of armored scale blemishes in many groves where growers have gone back to a heavy sulfur program. This is especially likely if 2 or more sulfur dusts or sprays are used in sequence. Finally, the choice of spray materials is of importance in minimizing blemish incidence. Some combinations and individual compounds are very risky in a fresh fruit pro gram (Table 1). A sulfur application too close to an oil spray is very likely to cause a burn (14). Another commonly used spray combination that often results in spray burns is ethion and oil. When this combination is applied as a con centrate spray on a 95 °F (35 °C) summer day, spray burn can occur. Generally, oil tends to increase the phytotoxic potential of any compound because it increases the penetra tion of chemicals through the stomatal pores (42) and plant cuticle. Mixing untested combinations of materials in the spray tank and applying these mixtures as concentrate sprays involves serious

risks that growers should not take on po tential fresh fruit blocks. When chelated nutritionals (31) are mixed with other materials, particularly as concentrate sprays, and applied to young fruit during the post bloom period, spray burns are likely to occur. The grower should be aware of the fact that climatic conditions prior to harvest and grove practices influence the ability of the fruit to withstand rough handling during or after harvest (2, 5, 6, 7, 13, 17, 18, 32, 33, 34, 35, 37, 43, 44). 80 • 1976. Water relations and citrus fruit quality Proc 2nd Int. Citrus Short Course-Water Relations, Oct 13-17, 1975, pp 4. 5. 6. 7. 8. 9. 41-48. rr • 1976. Influence of prevailing winds and hedging on citrus fruit wind scar. Proc Fla State Hort Soc 89:55-59 • 1977. Rootstocks affect Valencia orange fruit quality and water balance. Proc Int Soc Citriculture, 1977, 1:62-65 > and G. E Brown 1977 Storage studies with Valencia oranges. Proc Int Soc Citriculture, 1973, 3:361-367 ;

. , and P. J Fellers 1970 Peel and internal quality of oranges as influenced by grove applications of pinolene and benlate. Proc Fla State Hort Soc 83:263-267 » and R. C Bullock 1977 Injury to citrus fruits by leaffooted and citron plant bugs Proc Fla State Hort Soc 90:63-67 » and C. W McCoy 1974 Characteristic injury by citrus rust mite to orange leaves and fruit. Proc Fla State Hort Soc 87:48-55. 10. 11. Bar-Akiva, A. 1975 Effect of potassium nutrition on fruit splitting in Valencia orange. / Hort Sci 50:85-89 Brodrick, H. T 1970 Investigations into blemishes on citrus fruits S. Afr Citrus J 441:7, 9, 11, 13, 15, 17, 19, 21, 23, 25, 27-29, 31 12. Caprio, J M 1956 An analysis of the relation between regreening 13. 14. 15. 16. of Valencia oranges and mean monthly temperatures in Southern California. Proc Amer Soc Hort Sci 67:222-235 Davenport, T. L, C W Campbell, and P G Orth 1976 Stylar end breakdown in Tahiti lime: some causes and cures. Proc Fla State Hort. Soc 89:245-248

Florida Citrus Spray Guide. 1979 Coop Ext Service, IFAS, Univ Fla., Gainesville Cir 393-E Grierson, W. 1957 The effect of pack-out on grower profits Proc Fla. State Hort Soc 70:21-28 • 1958. Causes of low pack-outs in Florida packinghouses Proc. Fla State Hort Soc 71:166-170 17. • 1965. Factors affecting postharvest market quality of 18. 19. citrus fruits. Proc Amer Soc Hort Sci Caribbean Reg 9:65-84 • 1975. Injury in fruit Citrus Ind 56(12):15-17, 19 > M. F Oberbacher, and W L Thompson 1960 Fruit color, grove practices, and fresh fruit pack-out with particular refer 20. Griffiths, J. T and W L Thompson 1952 Grasshoppers in citrus 21. ence to tangerines. Proc Fla State Hort Soc 73:96-100 groves. Univ Fla Agr Expt Sta Bui 496, 22 pp and . 1957 Insects and mites on Florida citrus Univ. Fla Agr Expt Sta Bui 591 96 pp 22. Jones, W W and T W Embleton 1959 The visual effect of nitro gen nutrition on fruit quality of Valencia oranges. Proc Amer Soc 23. 24. Hort. Sci

73:234-236 > > M. J Garber, and C B Cree 1967 Creasing of orange fruit. Hilgardia 38:231-244 Ketchie, D. O 1969 The effect of high temperature on citrus Proc Proc. Fla State Hort Soc 91; 1978 1st Int. Citrus Symp 1:267-270 Univ Calif, Riverside, CA, USA 25. Kitajima, E W, G W Midler, A S Costa, and W Yuki 1972 Short, rod-like particles associated with Citrus leprosis. Virology 50:254-258. 26. Klotz, L J 1961 Color handbook of citrus diseases Univ Calif Press, Berkeley and Los Angeles, CA, USA. 75 pp 27. Knorr, L C 1973 Citrus diseases and disorders Univ Presses of Fla., Gainesville, FL, USA 163 pp 28. Koo, R C J 1961 Potassium nutrition and fruit splitting in Hamlin orange. Univ Fla Agr Expt Sta Annu Rpt pp 223-224 29. and R. L Reese 1977 Influence of nitrogen, potassium, and irrigation on Citrus fruit quality. Proc Int Soc Citriculture, 1977, 1:34-38. 30. Krezdorn, A H and M Cohen 1962 The influence of chemical fruit-set sprays on yield and quality of citrus. Proc Fla

State Hort. Soc 75:53-60 31. Leonard, C D, I Stewart, and J D Wright 1955 Reduction of fruit burn with pellatized Fe EDTA. Citrus Mag 18(4):17, 24-26 32. Lindgren, D L and W B Sinclair 1951 Tolerance of citrus and avocado fruits to fumigants effective against Oriental fruit fly. / Econ Entomol 44:980-990 33. McCornack, A A 1966 Blossom-end clearing of grapefruit Proc Fla. State Hort Soc 79:258-264 34. and W. Grierson 1965 Practical measures for control of rind breakdown of oranges. Univ Fla Agr Ext Service Cir 286 3 pp. 35. Monselise, S P and F M Turrell 1959 Tenderness, climate, and citrus fruit. Science 129:639-640 36. , M. Weiser, N Shafir, R Goren, and E E Goldschmidt 1976. Creasing of orange peelphysiology and control / Hort Sci 51:341-351. 37. Oberbacher, M. F 1965. A method incidence of oleocellosis on lemons. 78:237-240. Proc. Fla State Hort Soc 91: 1978 to predict the post-harvest Proc. Fla. State Hort. Soc. 38. Pratt, R M 1958 Florida guide to citrus insects,

diseases, and nutritional disorders in color. Univ Fla Agr Expt Sta, Gaines ville, FL, USA. 191 pp. 39. Reinking, R B 1967 Trithion spotting of grapefruit J Rio Grande Valley Hort. Soc 21:46-48 40. Smoot, J J, L G Houck, and H B Johnson 1971 Market diseases of citrus and other subtropical fruits. USDA-ARS-Agr Handbook No. 398 115 pp 41. Tilley, D S 1976 Florida citrus packinghouse cost-volume relation ships. Proc Fla State Hort Soc 89:183-185 42. Turrell, F M 1950 A study of the physiological effects of elemental sulphur dust on citrus peel. Plant Physiol 25:13-62 43. , S. P Monselise, and S W Austin 1964 Effect of cli matic district and of location in tree on tenderness and other physical characteristics of citrus fruit. Bot Gaz 125:158-170 44. Wardowski, W F, A A McCornack, and W Grierson 1976 Oil spotting (oleocellosis) of Citrus fruit. Univ Fla Coop Ext Service Cir. 410 4 pp 45. Whiteside, j O 1970 Factors contributing to the restricted oc 46. 47. 48. 49. 50. currence of

citrus brown rot in Florida. Plant Dis Rptr 54:608612 . 1972 Blemishes on citrus rind caused by Mycosphaerella citri. Plant Dis Rptr 56:671-675 . 1975 Planning of spray programs for the control of fungal diseases in Citrus groves. Proc Fla State Hort Soc 88:49-55 . 1976 A newly recorded Alternaria-induced brown spot disease on Dancy tangerines in Florida. Plant Dis Rptr 60:326-329 . 1978 Pathogenecity of two biotypes of Elsinoe fawcetti to sweet orange and some other cultivars. Phytopathology 68:11281131 Woodruff, R. E 1972 The coffee bean weevil, Araecerus fasciculatus (DeGeer), a potential new pest of citrus in Florida (Coleoptera: Anthribidae). Fla Dept Agr and Consumer Service, Div Plant Ind., Entomol Cir 117 2 pp 81