2/o Circular 4
*Leave lemons in the grove or at roadside for 24 hours before
transporting to the packinghouse. Note: This instruction is for
lemons only; all other citrus varieties should be transported
to the packinghouse as quickly as possible.
*Use metal shielded, deciduous -fruit type picking bags
(smaller than citrus bags) for lemons and particularly tender
crops of specialty fruit.
*Avoid getting sand on fruit. This causes abrasions resulting
in oil spotting. Check pallet boxes for broken or splintered wood
and protruding nails, staples, or bolts. In the packinghouse, elim-
inate sharp corners, rough welding spots, and unnecessarily stiff
or fast brushes.
*Keep the relative humidity in degreening rooms high (90 to
96% RH) to reduce the darkening of oil spots. This will make oil
spotting less obvious but will not eliminate or reduce it. When
there is a delay before packing in the non-degreening season,
hold fruit in high humidity rooms at ambient temperatures with-
out ethylene to minimize the darkening of oleocellosis lesions.
*Avoid abrasions of the peel at any time in the handling and
marketing sequence. Remember that the susceptibility of citrus
fruit to oil spotting becomes less as the time between harvest
and handling injury increases.
The Cooperative Extension Service, the Florida Department of
Citrus, and the University of Florida continue to evaluate oil
spotting and other peel injuries and postharvest diseases of
citrus fruit. Individual conferences on these and other har-
vesting, packing, and marketing problems can be arranged for
Florida citrus packers by contacting the Harvesting and Han-
dling Section, Agricultural Research and Education Center, Post
Office Box 1088, Lake Alfred, Florida 33850, phone (813)
This public document was printed at an annual cost of $878.41
or 171/2 cents per copy to aid in identifying and combating the
most common peel injury of Florida fresh citrus fruit.
9 5M -76
COOPERATIVE EXTENSION WORK IN AGRICULTURE AND HOME ECONOMICS
(Acts of May 8 and June 30, 1914)
Cooperative Extension Servce, IFAS, University or Florida
and United States Department of Agriculture Cooperating
Joe N. Busby. Dean
Cover photo courtesy of Joe Whigham, Florida Division of Fruit and Vege-
table Inspection, Winter Haven.
of Citrus Fruit
W. F. Wardowski, A. A. McCornack, W. Grierson
Agricultural Research and Education Center
Lake Alfred, Florida 33850
Florida Cooperative Extension Service
Institute of Food and Agricultural Sciences
University of Florida, Gainesville
OIL SPOTTING (OLEOCELLOSIS) OF CITRUS FRUIT
W. F. Wardowski, A. A. McComack, and W. Grierson'
WHAT IS OIL SPOTTING?
Oil spotting (illustrated on the cover of this circular) is a
common peel injury of citrus fruit, usually caused by mechanical
damage.2 It causes extensive financial loss to growers, shippers,
and handlers, not only in Florida but everywhere in the world,
particularly in the more humid areas where citrus fruit are
grown for the fresh fruit market.
Oil spotting is also known as: oleocellosis, oleo, bruising, green
spot, and, erroneously, as "gas burn." It can occur at any time
1Associate Horticulturist, Cooperative Extension Service; Food Technol-
ogist, Florida Department of Citrus; and Horticulturist, University of
Florida, respectively, all located at the Agricultural Research and Edu-
cation.Center, Lake Alfred sa880.
2Cooperative research by the University of Florida and the Florida De-
partment of Citrus.
during harvesting, handling, and marketing, but it mostly occurs
at or near harvest. Mechanical injury forces the toxic oil out of
the epidermal oil glands. The oil kills adjacent cells of the flavedo.
Citrus peel oil from injured fruit can also cause oil spotting on
the surface of adjacent undamaged fruit.
Fresh oil spotting is barely visible. With time, the damaged
areas will sink and darken, causing the oil glands to remain
prominent. Symptoms may be seen as the fruit arrive at the
packinghouse, but are often not noticed until after degreening
or shipment. Cells killed by oil are readily invaded by fungi re-
sulting in increased decay.
WHAT WE KNOW ABOUT OIL SPOTTING
Oil spotting can be reduced or eliminated on susceptible crops
by good handling practices.
All types and varieties of citrus can suffer damage from oleo-
cellosis, but those with numerous, prominent oil cells are partic-
ularly vulnerable. Oleocellosis occurs on all varieties of citrus,
but in Florida it is most severe on 'Parson Brown' and 'Navel'
oranges, grapefruit, 'Temples', tangelos, tangerines, lemons, and
Turgid and Small Fruit
Turgid fruit, particularly when harvested under foggy, wet,
or humid conditions, are most likely to develop oil spotting. Small
sizes tend to be more susceptible to oil spotting than large sizes.
Time of Day
Fruit turgidity is greatest, and hence the danger of oil spot-
ting is most serious, early in the morning. It is particularly
hazardous to pick susceptible crops when the dew is still on
Ethylene does not cause oil spotting, and "gas burn" is a ter
used without justification. However, the delay while fruit a:
degreening allows the oil spotting to darken, making it easier
see. Oil spots will darken less when fruit are held in high, rath,
than low, humidity before washing and waxing. The affect
areas on green fruit will not degree with ethylene, but rema
as green, grade-lowering blemishes.
The color-add process does not cause oil spotting. However, tl
color-add dye preferentially stains the injured areas, makir
them more obvious.
THE IMPORTANCE OF OIL SPOTTING
Losses from oil spotting are common and have increased i
recent years due to rough handling during harvest. Fruit ha
vested for the fresh fruit market, handled through the packing
house, and then sent to the processor as "eliminations" invoh
an economic loss. Packed fruit subsequently rejected by tl
wholesale buyer or retail consumer represent even greater losse
OIL SPOTTING CAN BE REDUCED OR ELIMINATE[
Oil spotting can be avoided or greatly minimized if a ft
simple rules are followed.
*Require pickers to handle fruit carefully, particularly tend
specialty varieties. Avoid cannery crews who are accustomed
handling fruit roughly.
*Pick dry fruit. Avoid harvesting when fruit are wet fro
dew, fog, rain, or irrigation, particularly early in the morning
*Use a pressure tester as a guide to determine when a crop
likely to suffer ruptured oil cells, causing oil spotting. A press
tester is absolutely necessary to judge when to harvest lemor
where a rule of thumb (using a %/ inch cylindrical tip) is: wh
less than 3 pounds of pressure ruptures oil cells, harvest is ii
possible; 3 to 7 pounds, harvest with extreme caution; over
pounds, harvest like other citrus varieties.
The publications in this collection do
not reflect current scientific knowledge
or recommendations. These texts
represent the historic publishing
record of the Institute for Food and
Agricultural Sciences and should be
used only to trace the historic work of
the Institute and its staff. Current IFAS
research may be found on the
Electronic Data Information Source
site maintained by the Florida
Cooperative Extension Service.
Copyright 2005, Board of Trustees, University