Citrus Station Mimeo Report CES 68-2
No. 10 July 17,. 1967
Harvesting and Handling Section
FRESH CITRUS FRUIT DECAY REGULATION
To increase the storage life of fresh Florida citrus fruit, the Florida
Fresh Citrus Shippers Association requested a regulation requiring fungicidal
treatment of all fresh citrus fruit shipped by registered packinghouses. This
regulation has been drafted and approved by the Florida Citrus Commission. A
copy is attached. This neswletter is written to explain this regulation.
Effective date.--August 1, 1967
Fungicides.--Two fungicides are approved by the U. S. Food and Drug
Administration for decay control of fresh citrus fruit.
Sodium o-phenylphenate (SOPP) is the fungicide commonly sold as "Dowicide A"
and used in various washes, dips, floods such as Dowicide A-hexamine. It is also
the fungicide in fungicidal water waxes. (It is the salt form of o-phenylphenol
(OPP) which has the common name of Dowicide 1.)
Diphenyl (or biphenyl) is applied in pads or wraps. It vaporizes slowly
into the air around the fruit and inhibits growth of decay causing organisms.
Except for 'Dancy' tangerines, containers with limited ventilation are essential
for this fungicide to be effective.
Combinations of fungicides.--Fruit treated with Dowicide A can be packed in
cartons with diphenyl pads. The resulting decay control is better than with
either fungicide alone.
Definition of terms
1. "Aqueous solution" means water solution,
2. "Aqueous emulsion" means emulsified in water.
3. "Gaseous" refers to the application of a fungicide as a gas mixed with
air. Diphenyl is given off gradually over a period of several days or
weeks depending on the original diphenyl concentration of the pads,
ventilation in the shipping container and the storage temperature.
Diphenyl controls decay for up to a week after the fruit is removed
from the shipping container.
4. "Registered Packinghouse'.'--A citrus packinghouse bonded with the Florida
Department of Agriculture and the Florida Citrus Commission. (Gift
fruit shippers are not included in this regulation.)
Newsletter No 10
5. "Fungicide'.--Kills fungus in the fruit.
6. "Fungistat'.--Doesn't kill the fungus but keeps it from growing.
7. "Tolerance'--Maximum amount of fungicide residue allowed in or on the
fruit by the U. S. Food and Drug Administration.
Diphenyl................... 110 ppm
Dowicide A (analyzed as Dowicide 1)........10 ppm
8. "Residue".--Amount of fungicide or fungistat in or on the whole fruit.
9. "Minimum Residue'--Diphenyl ................................. 11.0 ppm
Dowicide A--All citrus except grapefruit....1.0 ppm
10. "Grapefruit".--Because grapefruit has a larger volume in relation to
the surface area, the minimum residue necessary to comply with this
regulation is half that for other citrus fruit.
11. "ppm".--Means part per million.
Effectiveness of a fungicide
To be effective, a fungicide must enter scratches, other breaks in the peel,
and cover the surface under the button. The fungi which cause stem-end rot are
inactive under the button until a microscopic opening develops into the fruit.
These openings develop from conditions that cause drying, such as low humidity
during degreening and excessive delay between picking and a good wax application.
1. Dowicide applications of less than 1 minute are usually not effective
in controlling stem-end rot fungi but result in some mold control. A
1-minute application of Dowicide A can result in fair decay control but
a treating time of 2 to 3 minutes is more effective.
2. Diphenyl pads MUST be held in air-tight packages to retain their
3. Applications which do not allow the fungicide to diffuse under the
button are not effective against stem-end rot fungi, but may give some
control of mold decay.
Dowicide A alone can cause peel burn. Combining examine with
Dowicide A practically eliminates the possibility of peel burn when
used as directed. Solutions have been developed which contain
Dowicide A without examine. These materials, when handled exactly
as recommended, have given good decay control but, as with Dowicide A-
hexamine, the fruit should be rinsed following treatment.
No experimental work is available indicating that a 2% Dowicide A
solution (without examine) can be left on fruit without a possibility
of peel injury. Dowicide A with examine can be left on with less
danger of peel burn but shine will be reduced.
July 17, 1967
Newsletter No. 10 -3- July 17, 1967
Fungicidal waxes with Dowicide A, or Dowicide A with examine,
are on the market. They can give effective decay control when
applied so the wax diffused under the button and gives a complete
coverage of the fruit surface.
Dowicide A content of samples taken from packinghouses will be checked
by the Division of Fruit and Vegetable Inspection. The procedure for sampling
diphenyl has not been worked out but will probably be done by taking pads at
random from the packing stations, and placing them in air-tight containers
where they will be held until analyzed. Analytical work will be done by the
Division of Fruit and Vegetable Inspection, Citrus Building, P. 0. Box 1072,
Winter Haven 33850 (Phone 294-3511).
The following publications are available on request at the address listed
1. Recommendations for Control of Decay in Fresh Citrus Fruit.
2. Dowicide A-Hexamine Process for Citrus Fruit Decay Control Treatment.
3. Use of Diphenyl for Decay Control of Citrus Fruit, Newsletter No. 1.
4. Diagram of a suggested installation for applying Dowicide A-hexamine.
5. Labeling Containers of Fungicide Treated Citrus Fruit, Newsletter No. 6A.
I will be glad to meet with groups or individual packinghouse personnel to
discuss complying with this regulation.
A. A. McCornack
Harvesting and Handling Section
Citrus Experiment Station
P. O. Box 1088
Lake Alfred, Florida 33850
Florida Citrus Experiment Station
Lake Alfred, Florida
FUNGICIDE OR FUNGISTATE TREATMENT
REQUIRED FOR FRESH CITRUS FRUIT
Sec. (1) Effective August I, 1967, all Florida fresh citrus fruit shipped by a register-
ed packing house shall be treated with an approved fungicide or fungistat.
For the purposes of this regulation, an approved fungicide or fungistat shall
mean one approved by the U. S. Food and Drug Administration and the Flo-
rida Department of Agriculture for use on citrus fruit. Fungicides or fungi-
stats shall be applied either in aqueous solution, aqueous emulsion or in the
Sec. (2) The residue or residues of fungicides or fungistats, applied as required in
Section (1) hereof, in the whole citrus fruit shall be not less than 1/20 of
the legal tolerance for grapefruit and not less than 1/10 of the legal toler-
ance for all other varieties but for all varieties the total residue shall not
exceed the maximum tolerance established by the U. S. Food and Drug Ad-
When diphenyl is used, it is recognized that residues equal to 1/10 of the
legal tolerance may not be absorbed by the fruit prior to its leaving the
packing house. Therefore, the addition of diphenyl impregnated pads,
wraps or liners so that a total diphenyl content of not less than 4 grams is
used per 4/5 bushel container, or equivalent in other size containers, shall
constitute compliance with this regulation.
If two fungicides or fungistats are used, the above residue requirements
shall apply to each and shall not be cumulative.
Sec. (3) This regulation shall not apply to shipments of fresh Florida citrus fruit cer-
tified for export other than to Canada or Mexico.