PESTICIDE RESIDUES IN FOOD - 1981
Sponsored jointly by FAO and WHO
Food and Agriculture Organization of the United Nations
FAO PLANT PRODUCTION AND PROTECTION PAPER 42
pesticide residues in food:
data and recommendations
of the joint meeting
FAO panel of experts on pesticide residues
in food and the environment
WHO expert group on pesticide residues
Geneva, 23 November-2 December 1981
FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS
Chlorpyrifos was evaluated in 1972, 1975 and 1977*; an acceptable
daily intake (ADI) of 0.001 mg/kg bw was estimated and recommendations
made for maximum residue levels (MRLs) in a range of commodities. This
addendum contains data on residues following the application of
chlorpyrifos to kiwi-fruit in trials in New Zealand.
RESIDUES IN FOOD
Kiwifruit (Actinidia chinensis) is a major fresh export crop
from New Zealand to 23 importing countries. The main insect pests are
lepidopterous leaf rollers (mainly Ctenopseustis obliquana) and greedy
scale (Hemiberlesia rapax). Chlorpyrifos has given excellent control
of these pests. The proposed pattern required up to nine applications
per season, with a maximum of 37.5 a.i./100 l at 2 000 l per
application). The normal rate will be 0.5 kg a.i. per hectare per
application. The normal interval between last application and harvest
would be 14 days, although a shorter interval of as little as three
days may occasionally be necessary to meet quarantine requirements of
RESIDUES RESULTING FROM SUPERVISED TRIALS
Results of residue studies in chlorpyrifos and its major
metabolite, 3,5,6-trichloro-2-pyridinol in three locations over two
seasons, 1977 and 1979, were available (Mercer 1979). Two formulations
were used on kiwifruit, "Hayward", Lorsban 50W a 50% wettable powder
and Lorsban 50EC a 50% emulsifiable concentrate. Applications were
made with a hand gun at 1 700 KPa pressure delivering 4.62 litres of
spray per minute simulating commercial airblast sprayers.
Table 1 summarizes the residues found in the trials.
Residues in Trial II were determined on the whole fruit. In
Trials I and II, the whole fruit residues were calculated from
separate determinations on skin and pulp. In Trial III, the maximum
skin residue was 20.7 mg/kg at 1 day, which fell to 9.2 mg/kg after 21
days. The edible portion normally contains less than 0.1 mg/kg at all
* See Annex II for FAO and WHO documentation.
TABLE 1. Chlorpyrifos residues in kiwifruit (whole fruit) New Zealand, 1977, 1979.
Days after Residues in chlorpyrifos (mg/kg)
application Trial I 1 Trial II 2 Trial III 3
50 EC 50 W 50 W 50 EC
0 0.3 -- -- -- --
1 0.1 0.8 0.8 1.0 1.5 2.2
2 0.1 0.9 0.7 0.8 0.8 1.0 2.2
4 0.1 1.0 1.0 0.5 0.6 0.5 1.6 1.6
7 0.1 0.7 0.8 0.8 0.5 1.2 1.4
14 0.04 0.7 0.4 0.3 1.9 1.0
21 0.04 0.4 0.6 0.4 0.5 0.7
1 A single treatment of 25 mg/100 l chlorpyrifos (as 50 g/100
Lorsban 50 W) applied 20 April 1977.
2 Four applications at 25 g/100 l (50 g/100 l Lorsban 50W or
Lorsban 50 EC) at intervals of 0, 33, 37 and 6 days, with final
treatment on 2 May 1979.
3 Nine applications of 25 g/100 l chlorpyrifos (50 g/100 l Lorsban
50 W or 50 EC) at intervals of 0, 14, 14, 21, 21, 21, 28, 4 and
14 days, with final treatment on 30 April 1979.
SAMPLING AND ANALYSIS
About 1 kg fruit (10 to 15 units) was picked from each replicate
1, 2, 4, 7, 14 and 21 days after final treatment and from untreated on
day 1 (after final treatments). These samples were frozen at -10°C
The method of analysis converts chlorpyrifos into the pyrimidol
and determines total pyrimidol (which includes a small amount of
metabolite already present).
The limit of detection was generally lower (0.005 to 0.05 mg/kg)
in edible flesh than on skin or whole fruit (0.05 to 0.1 mg/kg);
chlorpyrifos recoveries ranged from 94 to 100 percent (near values).
Chlorpyrifos is effective for the control of leaf roller and
greedy scale, two important pests of kiwifruit in New Zealand.
Residue data from three locations over two seasons have provided
the basis for estimating a maximum residue level. Almost all the
chlorpyrifos and its main metabolite are retained in the inedible
skin, residues in the edible flesh being at or about the limit of
detection of the analytical method.
RECOMMENDATIONS OF RESIDUE LIMITS
Since maximum residue limits are recommended for kiwifruit on a
whole commodity basis, 2 mg/kg was proposed, based on a 4-day interval
between last application and harvest.
Mercer, C. Chlorpyrifos residues in kiwifruit. New Zealand data.