PESTICIDE RESIDUES IN FOOD - 1983
Sponsored jointly by FAO and WHO
EVALUATIONS 1983
Data and recommendations of the joint meeting
of the FAO Panel of Experts on Pesticide Residues
in Food and the Environment and the
WHO Expert Group on Pesticide Residues
Geneva, 5 - 14 December 1983
Food and Agriculture Organization of the United Nations
Rome 1985
CYHEXATIN
RESIDUES
Explanation
The 1978 Meeting proposed a maximum residue limit (MRL) of
2 mg/kg for cyhexatin on peaches.1 At the 15th Session of the Codex
Committee on Pesticide Residues (CCPR) in 1983 the United States
referred to agricultural practices in that country that could result
in residues exceeding 2 mg/kg. New information was reviewed by the
present Meeting, which indicated a need to increase the MRL.
RESIDUES IN FOOD AND THEIR EVALUATION
RESIDUES RESULTING FROM SUPERVISED TRIALS
Peaches
Residue studies were conducted at several locations in the United
States and in Ontario, Canada on seven varieties of peaches.
Treatments were up to three times with dilute sprays of 20 g a.i./100
1 applied to 3 400 to 9 000 l/ha or concentrated sprays of 0.84 kg or
1.68 kg a.i./ha applied at 450 l/ha.
Sample peaches were harvested at intervals after the last
application and analysed for total organotin residue, including
cyhexatin, dicyclohexyltin oxide and cyclohexylstannoic acid. The
method involved treating macerated fruit with hydrochloric acid,
extraction with warm chloroform to separate organotin compounds from
inorganic tin, evaporation of the chloroform, oxidation with nitric
and sulphuric acids, conversion of the resultant Sn+4 to its iodide,
formation of pyrocatechol violet complex and spectrophotometric
measurement of the colour (M&T Chemicals 1972). The residues found are
summarized in Table 1 (Getzendaner & Carbin 1973, 1975). All are
expressed as cyhexatin, which predominates at any given time.
Kiwi Fruit
Cyhexatin is the preferred miticide for the control of
phytophagus mites on kiwi fruit and has been used at between 12.5 g
and 20 g a.i./100 l, with one or two applications per season. The
volume varied from 1 200 l/ha to 3 400 l/ha, depending on application
equipment, equivalent to 150 g to 700 g a.i./ha.
Residue trials carried out in New Zealand in 1978, 1979 and 1981
are reported in Table 2.
Table 1 Residues of Cyhexatin in Peaches
Application AHI1 Total organotin found
Year Country Variety Rate No. (days) (as mg/kg cyhexatin)
Dilute sprays (20 a.i./100 l, 3 400-9 000 1/ha)
1969 United States Halford 1.7 3 0 2.0, 2.5, 2.8, 3.8
7 3.2, 3.2, 3.2, 3.6
14 2.4, 2.4, 3.2, 3.6
28 1.9, 2.0, 2.2, 2.7
2 53 0.6, 1.2, 1.4, 1.5
1 53 0.6, 0.9, 1.0, 1.1
1970 Halford 1.7 3 0 0.9, 1.5, 1.7, 2.3
7 1.1, 1.3, 2.1, 2.2
14 2.0, 2.1, 2.4, 2.6
28 1.2, 1.4, 1.5, 1.5
1970 Halford 3 0 1.5, 1.7, 1.7, 2.0
7 1.2, 1.4, 1.4, 1.5
14 0.9, 1.0, 1.1, 1.2
28 0.4, 0.5, 0.5, 0.6
1 See Annex 2 for FAO and WHO documentation.
Table 1 (con't)
Application AHI1 Total organotin found
Year Country Variety Rate No. (days) (as mg/kg cyhexatin)
1970 United States Red Haven 1.8-2.2 3 0 1.6, 1.9, 2.3
(early)
7 1.7, 2.0, 2.0
14 0.5, 0.6, 0.8
28 0.9, 0.9, 1.0
1970 Richaven 1.1-1.8 3 0 1.8, 2.0, 2.2, 2.2
7 1.8, 2.1, 2.4, 2.5
8 0.9, 0.9, 1.3, 1.4
20 0.4, 0.6, 0.6, 0.7
1972 Canada Goldray 1.1 1 7 0.6, 0.6, 0.8, 1.6
17 0.2, 0.4, 0.5, 0.6
25 0.2, 0.3, 0.3, 0.5
30 0.1, 0.1, 0.1, 0.2
60 0.0, 0.0, 0.0, 0.0
Concentrated sprays (0.84 kg or 1.68 kg a.i./ha in 450 l/ha)
1971 United States Elberta 0.84 3 0 0.3, 0.4, 0.5, 0.5
1974 United States Elberta 1.68 3 1 3.0, 4.1, 4.3
14 1.2, 1.9, 2.6
1 AHI = Interval from last application to harvest.
Table 2 Residues of Cyhexatin on Kiwi Fruit
Rate Formulation Residues (mg/kg)
No. (g a.i./ha) after last trial (days)
1 2 4 7 14
1979
1 680 1.9 - - 2.4 1.6
1978
1 700 1.0 - - 1.4 1.3
1981
2 (14-day interval) 600 (total) W.P. 1.7 - - 1.4 0.8
2 (14-day interval) 500 (total) aqueous susp. 2.1 1.9 1.4 1.6
2 (14-day interval) 300 (total) W.P. - 1.0 0.8 0.5 0.6
2 (14-day interval) 600 (total) W.P. - 1.6 2.4 0.5 0.5
In five trials the edible part was also analysed separately and
was found to contain less than 10 percent of the level in whole fruit,
except in the trial using an aqueous suspension when the proportion
was about 15 percent.
In general, the new data for peaches support those evaluated in
1978. However, it is clear that at shorter intervals between last
application and harvest, and particularly if the chemical is applied
in lower volumes than previously considered, then the earlier estimate
of 2 mg/kg as MRL will be exceeded. Thus, the Meeting estimated a new
MRL of 5 mg/kg, to take into account the new data and those in the
1978 evaluation, noting again that most of the residue was present in
the peel and that lower residues are found in smooth-skinned
varieties. The Meeting recommended that this estimate was suitable for
establishing an MRL.
APPRAISAL
Residue data on kiwi fruit from five trials over three seasons
have provided a basis for estimating an MRL. Levels in the edible part
of the fruit were up to about 15 percent of the whole-fruit residue.
Since MRLs are recommended for kiwi fruit on a whole-commodity basis,
5 mg/kg was proposed on the basis of a 3 to 4 day preharvest interval.
The Meeting reviewed the limited data on residues of cyhexatin on
beans in the 1978 evaluations and concluded that an estimated MRL of
0.2 mg/kg was more appropriate than the figure of 0.5 mg/kg previously
estimated.
REFERENCES - RESIDUES
Getzendaner, M.E. & Carbin, H.B. Residues of organotin on peaches and
1973 nectarines, fresh and dried plums from applications of
PLICTRAN 50W miticide. Dow Chemical Company report GH-C 643.
(Unpublished)
Getzendaner, M.E. & Carbin, H.B. A study of residues on stone fruit
1975 from concentrate spray applications of PLICTRAN 50W
miticide. Dow Chemical Company report GH-C 800.
(Unpublished)
M&T Chemicals. Determination of small amounts of organotin in
1972 macerated fruit. Analytical method TA-27. (Unpublished)