WHO Pesticide Residues Series, No. 1
1971 EVALUATIONS OF SOME PESTICIDE RESIDUES IN FOOD
THE MONOGRAPHS
The evaluations contained in these monographs were prepared by the
Joint Meeting of the FAO Working Party of Experts on Pesticide
Residues and the WHO Expert Committee on Pesticide Residues that met
in Geneva from 22 to 29 November 1971.1
World Health Organization
Geneva
1972
1 Pesticide Residues in Food: Report of the 1971 Joint Meeting of
the FAO Working Party of Experts on Pesticide Residues and the WHO
Expert Committee on Pesticide Residues, Wld Hlth Org. techn. Rep.
Ser., No. 502; FAO Agricultural Studies, 1972, No. 88.
These monographs are also issued by the Food and Agriculture
Organization of the United Nations, Rome, as document AGP-1971/M/9/1.
FAO and WHO 1972
THIABENDAZOLE
The Joint Meeting in 1970 considered the toxicological and related
data as well as the use of thiabendazole as an anthelmintic for sheep
and cattle and as a post-harvest fungicide for the treatment of
bananas and citrus. (FAO/WHO 1971). It was noted that numerous
investigators had reported thiabendazole effective for pro-harvest and
especially post-harvest treatment of several additional fruits
including apples, pears, peaches, cherries and pineapples but that the
available data were not sufficient to enable proposals to be made for
tolerances.
Considerable data on these use patterns and the resulting residues
have now been evaluated and proposals are made for additional
tolerances.
USE PATTERN
Post-harvest treatments
Each year enormous quantities of apples and pears are damaged or
destroyed by fungal diseases between the time they are harvested and
the time they reach the consumer. The losses are shared by growers,
packer-shipper-storage and transportation companies, processors,
wholesalers, retailers and consumers.
Blue mould is the most common and usually the most destructive of all
the rots found on pome fruits in transit, in storage and on the
market. Blue mould is caused by Penicillium expansum and possibly
other species of Penicillium. "Bull's eye rot" caused by two fungi,
Gloeosporium perennans and Neofabraea. Malicorticis is also
important in many fruit growing areas, particularly in North America
and Australia.
Grey mould is the most serious storage disease of pears. The causal
fungi (Botrytis spp.) are widely distributed and occur in decaying
plant matter in orchards. Infestation takes place through the calyx
and through the stem and fungi continue to grow even at cold storage
temperatures. Grey mould caused by Botrytis cinerer also affects
apples.
Until the introduction of thiabendazole, no suitable treatment of
these diseases was known.
The efficacy of thiabendazole for control of blue mould has been
reported by Beattie and Oufored (1970); Blanpied and Apathai Purnasiri
(1968); Cargo and Dewey (1969); Maas and MacSwan (1970); Pierson
(1966); Scott and Roberts (1970) and Spalding et al. (1969). The use
of thiabendazole dips for the control of grey mould (Botrytis) has
been reported by Beattie and Oufored (1970) and Benitez and Weigert
(1970).
The effect of thiabendazole dips for the control of Gloeosporium
rots in apples is reported by Hamer et al. (1970).
The modern practices of mechanically handling fruit in large
containers requires that they be dumped into a tank of water to avoid
bruising during unloading. Such baths cause spread and penetration of
fungal spores. Likewise spores are spread during the dipping of apples
and pears in ethoxyquin or diphenylamine solutions used to control
scald. Several authors have evaluated thiabendazole as an additive to
such dips.
Thiabendazole, formulated as a micronized wettable powder is suspended
in water to give a concentration of from 250 to 1000 ppm (usually 500
ppm) in the prepared dip or spray solution. Fruit is dipped for
varying periods ranging from 15 seconds to three minutes. The fruit is
then allowed to dry without rinsing, before being packed for storage
or shipment.
While most investigators have carried out the treatment at ambient
temperatures 15°-18°C some reports indicate superior results at
elevated temperatures (40°-55°C). In some instances the treated fruit
after storage for varying periods, were washed and waxed. In other
cases the fruit were treated with thiabendazole in wax emulsions
applied as dips or sprays. The concentration of thiabendazole in the
wax emulsion ranged from 1000 to 4000 ppm.
Residues resulting from supervised trials
Apples and pears
Extensive data resulting from numerous supervised trials carried out
in the United States of America, Canada and Australia have been
examined. These show considerable variation in the concentration of
the thiabendazole residue depending on the concentration of the dip,
spray or wax emulsion; the method of application, the time of
immersion; the temperature of the dip bath and whether or not the
fruit was washed or waxed prior to delivery out of storage.
The following is a brief summary of the thiabendazole residues found
on apples treated by several methods:
Thiabendazole
residue range
Treatment method (ppm)
I. Single dip treatment - thiabendazole
alone
A. Ambient temperature 15°-18°C 0.25-5.63
Concentration 500, 890, 1000,
1080, 1782, 2000 ppm
B. Elevated temperatures 40-45-50-55°C 1.85-4.53
Concentrations 500 and 1080 ppm
C. Ambient temperature 15-18°C 0.46-1.13
Concentrations 500, 1000, 2000 ppm
Fruit waxed after treatment
D. Ambient temperature 15-18°C 1.92-2.30
Concentration 1000 ppm
Fruit washed and waxed after storage
II. Single dip treatment - thiabendazole in 0.73-4.61
combination with diphenylamine
Concentrations 500, 540, 1000, 1080,
2159 ppm
III. Single dip treatment - thiabendazole in 0.64-4.85
combination with ethoxyquin (2700 ppm)
A. Concentrations 500, 540, 1000, 1080,
2159 ppm
B. Concentration 1080 ppm 0.83-1.12
Fruit dried and waxed
C. Concentration 1000 ppm 2.72-5.88
Fruit held overnight and then washed
and waxed
IV. Single flood treatment 1.63-3.29
Concentration 1000 and 2000 ppm
V. Single spray treatment
Ambient temperature 15-18°C
A. Concentration 540, 1080, 2159 ppm 0.13-1.76
B. Elevated temperature 55°C 0.47
Thiabendazole
residue range
Treatment method (ppm)
VI. Single wax treatment 0.32-3.28
Concentrations in wax 1000, 1500, 2000,
3000, 4000 ppm
VII. Double treatment 1.60-8.75
A. Dip treatment before storage
(540, 1080 and 2159 ppm)
+ dip treatment after storage
(540, 1080 and 2159 ppm)
B. Dip treatment before storage in 2.88-8.05
combination with ethoxyquin (2700 ppm)
concentration 540, 1080 and 2159 ppm
+ dip treatment after storage
concentration 540, 1080, 2159 ppm
C. Dip treatment before storage 1.44-5.68
540, 1080, 2159 ppm
+ dip treatment after storage
540, 1080, 2159 ppm followed by
waxing
Fate of residues
If fruit were treated prior to and after storage a rinsing or washing
operation would probably occur between the two treatments. The
ultimate consumer might further reduce the residue by rinsing and/or
washing the fruit.
A series of experiments was carried out under commercial conditions to
determine the loss of residue by such washing and/or rinsing. The
results are summarized as follows:
Treatment I Residue Treatment II Residue %
ppm ppm reduction
A. Single dip 1000 13.19 Held overnight, 2.81 79
ppm + ethoxyquin washed, brushed,
2700 ppm rinsed and
waxed
B. Single dip 1000 3.58 After four 2.11 41
ppm + ethoxyquin months storage
2700 ppm washed, brushed,
Stored four rinsed and
months waxed
C. Single dip 1080 1.89 Rinsed for five 0.85 55
ppm + ethoxyquin seconds in
2700 ppm water after
dipping
Analytical methods suitable for the determination of thiabendazole
residues in apple pulp, juice and pomace have been developed but data
on the residue levels found in practice were not reviewed. However, in
view of the information on the removal of residues by washing and
rinsing it is obvious that most of the residues present on the whole
fruit would be removed during peeling for the preparation of apple
pulp. There may be some distribution into juice due to the solubility
in water. However, the residue level in juice would not be greater
than the residue in the whole fruit.
Thiabendazole residues in apple pomace would not present any hazard to
livestock (thiabendazole is administered to animals for control of
internal parasites at levels of 50-100 mg/kg). No significant residues
would be expected to occur in meat or milk following feeding of pomace
containing such residues.
Evidence of residues in food in commerce or at consumption
No results have been received of any monitoring of apples and pears in
commerce since the registrations for such uses have only recently been
granted and it is unlikely that any significant quantity of commercial
pome fruit has yet been treated.
Methods of residue analysis
The analytical procedure utilizing the spectrophotofluometric
measurement of the fluorescence of the acid aqueous solution of the
alkali washed ethyl acetate extract of residues from the whole
homogenized fruit is entirely satisfactory for use with apples, pears
and their pulp or juice. The method is substantially the same as that
referred to in the 1970 Monograph (FAO/WHO 1971). The sensitivity is
less than 0.05 ppm on 20 g of sample.
National tolerances
Country Commodity Tolerance ppm
Argentina Apples & pears - post-harvest no restriction
Australia " " " " 6
Canada " " " " 11
Chile " " " " no restriction
France " " " " 6
United Kingdom " " " " no restriction
Appraisal
Recommendations were made in 1970 for tolerances for thiabendazole
residues in bananas and citrus fruit. Information on further uses and
the resulting residues have been considered by the meeting.
Thiabendazole is a particularly effective fungicide with systemic
properties for the post-harvest treatment of apples and pears useful
for the control of a variety of storage rots and rots transmitted by
modern mechanical handling procedures.
The methods of application, including combinations with scald control
treatments will vary considerably depending on the handling
procedures, storage facilities and length of storage before
distribution. For this reason the residue levels vary through a fairly
wide range. These residues are substantially all on the skin or within
about 1 mm of the outer surface of the ripe fruit and a substantial
amount is removed by rinsing or washing.
RECOMMENDATIONS FOR TOLERANCES, TEMPORARY TOLERANCES
OR PRACTICAL RESIDUE LIMITS
Tolerances
The following tolerances are recommended as additional to those
recommended in 1970:
Commodity Residue (ppm)
Apples and pears 10
REFERENCES
Beattie, B. B. and Outbred, N. L. (1970) Benzimidazole derivatives as
post-harvest fungicides to control rotting of pears, cherries and
apricots. Aust. J. exp. Agr. Anim. Husb., 10 October 1970
Blanpied, G. D. and Apathai Purnasiri. (1968) Thiabendazole control of
Penicillium rot of McIntosh apples. Plant Dis. Rep., 52: 867-871
Cargo, C. A. and Dewey, D. H. (1969) Thiabendazole and benomyl for the
control of post-harvest decay of apples. Michigan Agr. Exp. Stn. J.,
Article No. 4941
Hamer, P. S., Gayner, F. C. M. and Constanduros, R. (1970) Fungicide
trial of thiabendazole dips for control of gloeosporium rots on
apples. Merck, Sharp and Dohme U. K. Report B 1970
Mass, J. L. and MacSwan, I. C. (1970) Post-harvest fungicide
treatments for reduction of Penicillium decay of Anjou pears. Plant
Dis. Rep., 54 (10): 887-890
Merck, Sharp and Dohme. (1971) TECTO 90 for control of specific
post-harvest fruit rots. Submission to National Health and Medical
Research Council - Australia
Merck, Sharp and Dohme. (1971) Petition to Environmental Protection
Agency - Washington
Pierson, C. F. (1966) Fungicides for the control of blue mould rot of
apples. Plant Dis. Rep., 50, 913-915
Scott, K. J. and Roberts, E. A. (1970) Thiabendazole to reduce rotting
in Packham's Triumph pears during storage and marketing. Aust. J. Exp.
Agr. Anim. Husb.
Spalding, D. H., Vaught, H. C., Day, D. H. and Brown, G. A, (1969)
Control of blue mould rot development in apples treated with heated
and unheated fungicides. Plant Dis. Rep., 53 (9), 738-742
See Also:
Toxicological Abbreviations
Thiabendazole (WHO Food Additives Series 39)
Thiabendazole (AGP:1970/M/12/1)
Thiabendazole (WHO Pesticide Residues Series 2)
Thiabendazole (WHO Pesticide Residues Series 5)
Thiabendazole (Pesticide residues in food: 1977 evaluations)
Thiabendazole (Pesticide residues in food: 1979 evaluations)
Thiabendazole (Pesticide residues in food: 1981 evaluations)