RESIDUE AND ANALYTICAL ASPECTS
Myclobutanil is a systemic, foliar-applied fungicide. It was first reviewed by the 1992 JMPR. The MRLs recommended for stone fruits are now adopted as CXLs. At the 28th Session of the CCPR the EC delegation questioned the residue evaluation for stone fruits. The manufacturer provided information on GAP and data on residues for a review of use patterns and a reconsideration of maximum residue levels.
The Meeting received updated information on GAP in EC countries and the USA. The manufacturer provided reports of five supervised trials carried out in the USA on apricots in 1991, and data on residues at a 0-day PHI in cherries, peaches and plums.
The manufacturer also requested the evaluation of data on residues in bananas, blackcurrants, citrus, hops, strawberries and tomatoes. The manufacturer provided data on residues in sweet peppers, but this information was received too late for evaluation.
The analytical methods for determining the residues of myclobutanil and its metabolites in fruits were as described in the 1992 JMPR evaluation.
Studies of the stability of residues in stored analytical samples of soil, apples, grapes, tomatoes, cucurbits and almond meat and hulls were reported to the Meeting. Residues of myclobutanil and its metabolite hydroxy-myclobutanil (RH-9090) were found to be stable in frozen conditions (-15°C) in soil, apples and grapes for at least two years, in cucurbits and tomatoes (at -10°C) for three years and in almond meat and hulls at -10°C for at least two years. It can be concluded that residues of myclobutanil in stored samples are stable in frozen conditions.
Myclobutanil is available as 125 and 240 g/l emulsifiable concentrate, 60 g/l suspension concentrate, 200 g/l emulsion oil in water and 40% wettable powder.
Supervised trials
In all the trials on stone fruits reported to the Meeting the residues were determined in the edible portion of the fruits and the proportional weights of the stones were not given. The average percentage weights of the stones in each of the fruits were reported by the manufacturer and these averages were used to estimate maximum residue levels in the whole fruits.
Apricots. The results of field trials in France, Italy and the USA were provided. The trials from Italy were not considered for the estimation of a maximum residue level as no relevant GAP was reported. Residues from six trials according to GAP in France ranged from 0.01 to 0.08 mg/kg; the residues of the metabolite were not determined. In five trials according to US GAP (7-17 applications at 0.07 to 0.165 kg ai/ha, 0-day PHI), the total residues found were between 0.13 and 0.7 mg/kg in the edible fruit. Residues of the metabolite were between 13 and 26%, and in one trial 46%, of the parent compound. In summary the myclobutanil residues in apricots from trials complying with GAP were 0.01, 0.04, 0.04, 0.04, 0.06 and 0.08 mg/kg in France and 0.11, 0.12, 0.17, 0.23 and 0.62 mg/kg in the USA.
Cherries. Supervised trials on cherries carried out in Germany and the USA which were evaluated by the 1992 JMPR were re-evaluated at the light of new GAP. Total residues (myclobutanil + metabolites) were determined. Myclobutanil residues from four residue decline trials in Germany according to GAP (3 applications at 0.135 kg ai/ha, 21 days PHI) were 0.01 and 0.02 (3) mg/kg. Three of the US trials reported in 1992 which included a 0-day PHI were reviewed. Five other trials reported to the present Meeting complied with US GAP (<9 applications at 0.07-0.16 kg ai/ha, with a maximum of 1.45 kg ai/ha per season, 0-day PHI). The residues of myclobutanil per se in the US trials in rank order were 0.2, 0.28, 0.68, 0.85, 0.92, 1.04, 1.12 and 1.44 mg/kg. In two of the trials metabolite residues reached more than 40% of those of the parent compound.
Peaches. Several trials carried out in France, Spain and the USA were reported in 1992. A trial in France was not conducted according to GAP but it could be evaluated against the Spanish use pattern. Residues from two Spanish trials according to GAP (1-4 applications at 0.08-0.1125 kg ai/ha, 15 days PHI) were 0.02 and 0.03 mg/kg; metabolites were not determined. Three US trials reported in 1992 were re-evaluated together with six new trials, all according to new US GAP (<9 applications at 0.07-0.165 kg ai/ha, with a maximum of 1.45 kg ai/ha per season, 0-day PHI). Residues of RH-9090, its conjugate, and the ketone RH-9089 were determined as RH-9090 in all the trials. The total residue in the edible portion in the US trials ranged from 0.35 to 1.53 mg/kg, with residues of myclobutanil from 0.33 to 1.22 mg/kg.
Plums and prunes. Two trials reported to the Meeting complied with US GAP (7 applications at 0.06-0.165 kg ai/ha with a maximum of 1.2 kg ai/ha per season, 0-day PHI). The total residues were 0.1 and 0.73 mg/kg with myclobutanil residues of 0.09 and 0.59 mg/kg. One trial in Italy (4 applications at 0.1-0.15 kg ai/ha, 14-day PHI) was evaluated against Greek GAP (3 applications at 0.055-0.125, 15 days PHI); the total residue was 0.1 mg/kg. There were too few results to estimate a maximum residue level. The existing CXL is 0.2 mg/kg.
In view of the similar use patterns for the individual fruits, the Meeting agreed to evaluate the combined US data as applying to stone fruit, except plums. The myclobutanil residues in stone fruit (edible portion) in rank order (median underlined) were 0.09, 0.11, 0.12, 0.17, 0.2, 0.23, 0.28, 0.33, 0.34, 0.38, 0.59, 0.62, 0.66, 0.68, 0.74, 0.75 (2), 0.85, 0.92, 1.04, 1.12, 1.22 and 1.44 mg/kg. The Meeting estimated a maximum residue level of 2 mg/kg and an STMR of 0.62 mg/kg for stone fruit except plums, and recommended the withdrawal of the individual CXLs for apricot, cherries and peach.
Bananas. Several studies were conducted in the USA and Costa Rica according to the proposed use of myclobutanil in banana packing stations in grower countries. All treatments consisted of one application of myclobutanil, and banana hands were sprayed or dipped at various concentrations.
Those trials in which myclobutanil was used at 200 or 400 mg ai/l and residues were calculated on the whole banana were evaluated to estimate a maximum residue level.
Banana samples taken at intervals of 0 to 28 days after treatment showed that the residues in the pulp increase with time. There was also a loss in weight of the banana hands with storage time, mainly from the peel. Storage periods from 7 to 21 or 28 days represent the shipping periods needed to reach different markets.
Residues in samples with 0-7 days storage are most appropriate for estimating maximum residue levels because they are the highest in the whole fruit, but residues after longer storage times are appropriate for assessing dietary exposure because the residues in the pulp increase with time. Residues of the parent compound were predominant in the total residue; those of the sum of the free and conjugated forms of the hydroxy metabolite (RH-9090) were less than 10% of the total in most of the trials.
The highest residues in whole bananas from each trial at the highest proposed GAP concentration, 400 mg ai/l, from 7 to 28 days ranged from 0.64 to 1.7 mg/kg. Since these results were from trials according only to proposed GAP, the Meeting was unable to estimate a maximum residue level.
Residues of myclobutanil in the edible pulp of the bananas in rank order (median underlined) were 0.1, 0.17, 0.17, 0.19, 0.2, 0.21, 0.22, 0.27, 0.28, 0.35, 0.39 and 0.41 mg/kg.
Citrus fruit. The results of twelve trials in Spain on the post-harvest treatment of mandarins with myclobutanil were reported to the Meeting. The reports lacked critical analytical data such as LOD, recoveries, and chromatograms. The residues of myclobutanil (applied as a water/wax emulsion or emulsifiable concentrate) in samples of whole fruit from trials complying with GAP (0.05 kg ai/hl or 0.01 kg ai/t fruit, 0-day PHI), ranged from 0.94 to 2.9 mg/kg. The residues from treatments with the EC formulation at 0.05 kg ai/hl, 0-day PHI, in rank order were 0.94, 1.15, 1.33, 1.5, 1.56, 1.7 and 2.0 mg/kg. Fruit samples were also analysed at 7 and 14 days after treatment. No decrease in the residue was observed in most of the trials.
Several trials on the post-harvest treatment of various varieties of orange which complied with Spanish GAP were reported to the Meeting. Myclobutanil was used as a water/wax emulsion and an EC formulation. The residues of myclobutanil ranged from 0.87 to 2.66 mg/kg. The myclobutanil residues in the whole fruit from treatment with the EC formulation according to GAP (0.05 kg ai/hl) were 1.06, 1.3, 1.36, 1.49, 1.53 and 1.8 mg/kg.
Since the citrus trials lacked the critical analytical data mentioned above the Meeting could not recommend an MRL.
Whole-fruit samples of the oranges and mandarins in these trials were separated into peel, pulp and juice. Analysis showed that the myclobutanil residue was almost all in the peel and not found in the pulp. The residue in the juice was approximately 10% of that in the whole fruit (0-day PHI). The residues of the metabolite were not determined.
Berries. Several field trials were conducted on blackcurrants in the UK with various myclobutanil formulations. In all the trials blackcurrant samples were analysed for the parent compound and RH-9090. The residues of myclobutanil from trials according to UK GAP (4-6 applications at 0.09 kg ai/ha, 14 days PHI) ranged from 0.04 to 0.43 mg/kg, with total residues (myclobutanil + RH-9090) from 0.08 to 0.47 mg/kg. In three of fifteen trials reflecting GAP, residues of the metabolite were equal to or higher than those of the parent compound.
The residues of myclobutanil in blackcurrants in rank order (median underlined) were 0.04, 0.07, 0.08, 0.19, 0.24, 0.24, 0.26, 0.26, 0.29, 0.3, 0.3, 0.31, 0.35, 0.42, 0.43 mg/kg.
The Meeting estimated a maximum residue level of 0.5 mg/kg and an STMR of 0.26 mg/kg for blackcurrants.
Numerous field trials on strawberries have been conducted in the UK, France, Italy and Spain. The residues in seventeen trials in the UK in accordance with GAP (4-6 applications at 0.09 kg ai/ha, 3-day PHI) ranged from 0.1 to 0.5 mg/kg; residues of the metabolite were below the LOD. In one trial in France with more applications than are allowed by GAP, the residue of myclobutanil at 4 days was 0.04 mg/kg. In two trials in Italy which complied with GAP (3 or 4 applications, 0.005 kg ai/hl, 7-day PHI) the residues were 0.05 and 0.09 mg/kg. The residues in strawberries from trials in Spain ranged from 0.02 to 0.15 mg/kg.
The myclobutanil residues in strawberries in rank order (median underlined) were 0.04, 0.05, 0.08, 0.08, 0.09, 0.1, 0.12, 0.15, 0.15, 0.15, 0.17, 0.18, 0.18, 0.19, 0.19, 0.19, 0.19, 0.2, 0.2, 0.22, 0.24, 0.36, 0.48, 0.5 and 0.69 mg/kg.
The Meeting estimated a maximum residue level of 1 mg/kg and an STMR of 0.18 mg/kg for strawberries.
Tomatoes. The results of a large number of indoor and outdoor trials from several countries were reported to the Meeting. The residues found in Belgian trials (indoors) reflecting GAP (3-6 applications at 0.0075 kg ai/hl, 3 days PHI) ranged from 0.05 to 0.16 mg/kg; metabolites were not detected. Four trials in France (6 applications at <0.12 kg ai/ha, 3 days PHI) were evaluated against Spanish GAP (1-6 applications, 0.112 kg ai/ha, 3 days PHI). The residues were 0.02, 0.03, 0.04 and 0.05 mg/kg. The residues from trials in Spain according to GAP ranged from 0.03 to 0.24 mg/kg; the residues of metabolites determined in two trials were below 20% of those of the parent compound. In one trial in Italy according to GAP the residue was 0.02 mg/kg, with metabolites expressed as RH-9090 below the LOD. Four other trials were carried out in Italy in 1996, but as the Meeting doubted whether the data had been recorded properly the residues from them were not included in the evaluation. In trials according to GAP in Morocco (1-3 applications, 0.00625 kg ai/hl, 7-day PHI), the residues were between 0.02 and 0.06 mg/kg. The residues of the metabolite determined in two trials were below the LOD.
The residues in fifteen US field trials according to GAP on several varieties of tomato (0.07 kg ai/ha/application, with a maximum of 0.4 kg ai/season, 0-day PHI), ranged from 0.01 to 0.22 mg/kg.
The myclobutanil residues in tomatoes in rank order (median underlined) were 0.01, 0.02 (7), 0.03 (3), 0.04 (3), 0.05 (7), 0.06 (2), 0.07, 0.08 (4), 0.09 (2), 0.11, 0.15 (3), 0.16, 0.22 and 0.24 mg/kg.
The Meeting estimated a maximum residue level of 0.3 mg/kg and an STMR of 0.05 mg/kg for tomatoes.
Hops. Four of six trials conducted in the UK were according to GAP (6 applications, 0.0045 kg ai/hl, 10 days PHI). The residues of myclobutanil in the dried cones ranged from 0.2 to 1.2 mg/kg. The Meeting considered the database insufficient to estimate a maximum residue level.
The Meeting was informed that a further four trials are in progress in Germany and that they included processing studies.
Processing
Two supervised trials on tomatoes were conducted in the USA, with 4 applications at rates of 0.067 and 0.14 kg ai/ha. Samples harvested 5 days after the last treatment were processed to canned whole tomatoes, juice, puree, pomace and paste. In four processing studies in France, tomatoes treated with 6 applications of myclobutanil (0.107-0.12 kg ai/ha) were harvested 3 days after the last treatment and processed into juice, preserve and puree.
There was no concentration of the residue in tomato juice, canned tomatoes or preserve. The residues in tomato purée were concentrated by factors of 1.0 to 3, with an average of 1.6. The concentration factors for dry pomace were 14 and 17, with an average of 15.5, and for paste 3.7 and 4.2, mean 3.9. In some processed products, residues of the metabolite reached 50% or more of the total residue. On the basis of an STMR of 0.05 mg/kg, the Meeting estimated STMR-Ps of 0.08 mg/kg for tomato purée, 0.78 mg/kg for dry pomace, and 0.2 mg/kg for paste.
Data from three processing trials on blackcurrants in the UK indicated that residues in the juice decreased about 1.5-5 times, with a mean processing factor of 0.35. Canned fruit, in a single trial, showed a decrease in the residue of myclobutanil but a higher concentration of the metabolite, with the same total residue. The Meeting estimated an STMR-P of 0.09 mg/kg for blackcurrant juice from the STMR of 0.26 mg/kg for blackcurrants (whole fruit).
Two processing trials on strawberries in the UK showed that residues do not concentrate in strawberry jam or preserve. The average processing factors were 0.5 for jam and 0.81 for preserve.
The Meeting estimated STMR-Ps of 0.09 mg/kg for jam and 0.15 mg/kg for preserve on the basis of an STMR of 0.18 mg/kg for whole strawberries.
