WHO Pesticide Residues Series, No. 1



    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



    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


    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

    Considerable data on these use patterns and the resulting residues
    have now been evaluated and proposals are made for additional


    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

    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

    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 15-18C some reports indicate superior results at
    elevated temperatures (40-55C). 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:


                                                           residue range
    Treatment method                                           (ppm)

    I.     Single dip treatment - thiabendazole

           A.   Ambient temperature 15-18C                  0.25-5.63
                Concentration 500, 890, 1000,
                1080, 1782, 2000 ppm
           B.   Elevated temperatures 40-45-50-55C           1.85-4.53
                Concentrations 500 and 1080 ppm
           C.   Ambient temperature 15-18C                   0.46-1.13
                Concentrations 500, 1000, 2000 ppm
                Fruit waxed after treatment
           D.   Ambient temperature 15-18C                   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 15-18C

           A.   Concentration 540, 1080, 2159 ppm             0.13-1.76
           B.   Elevated temperature 55C                     0.47


                                                           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

    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

    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

    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


    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.



    The following tolerances are recommended as additional to those
    recommended in 1970:


                             Commodity              Residue (ppm)

                             Apples and pears            10


    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)