Haloxyfop was evaluated for the first time by the 1995 JMPR. That Meeting received data on residues in beans and peas but the exact Codex commodities to which the data referred were not clear. The 1995 Meeting agreed not to estimate maximum residue levels until the commodity descriptions were clarified. Supplementary information on the commodity described as "peas" has now been made available.
The 1995 Meeting could not complete the evaluation of the ruminant and poultry metabolism studies in the time available and reviewed the residue data on ruminants and poultry on the assumption that metabolism in these species is essentially the same as indicated in the metabolism studies on rats, mice, dogs, monkeys and humans. The present Meeting completed the evaluation of the studies of ruminant and poultry metabolism.
The 1995 JMPR estimated a number of maximum residue levels, but agreed not to recommend their use as MRLs because of the lack of critical supporting data on the uptake of soil degradation products by crops. Studies on the uptake of haloxyfop or its degradation products from soil treated with haloxyfop have been made available to the present Meeting.
Metabolism in lactating goats and laying hens
Metabolic studies on lactating goats and laying hens with 10 or 11 days consecutive oral dosing at rates equivalent to 12-16 ppm in the feed were reported.
In goats, the administered haloxyfop was rapidly absorbed from the gastrointestinal tract and mainly excreted in the urine unchanged (84-92%). The radioactivity remaining in the body was relatively low, at levels of 0.02, 0.1, 0.4 and 1.3 mg/kg haloxyfop equivalent in the muscle, body fat, liver and kidneys respectively 12 hours after the last dose. The liver and kidneys contained only haloxyfop or its polar conjugates; the radioactivity in muscle was too low for identification of the residues. The predominant metabolites in the body fat and milk fat were identified as non-polar conjugates of haloxyfop and were evidently triacylglycerols because they were hydrolysed by lipase to produce haloxyfop.
Laying hens eliminated 82-90% of the dose as intact haloxyfop in their excreta. Radioactive residues in tissues were 0.12, 0.99, 1.8 and 4.2 mg/kg haloxyfop equivalent in the muscle, body fat, liver and kidneys respectively 24 hours after the final administration. Polar and non-polar conjugates were found as major metabolites in the tissues. The nature of metabolites in the body fat and egg yolk was same as in goat body and milk fat. They were easily hydrolysed by lipase to yield haloxyfop.
In conclusion, the metabolism of haloxyfop in poultry is similar to that in ruminants, which is essentially the same as in the other mammalian species studied: rats, mice, dogs, monkeys and humans.
These studies show that the definition of the residue for products of animal origin should be the same as for plant products.
Residue evaluations
Peas (pods and succulent seeds). Four supervised trials were carried out with racemic haloxyfop-etotyl in France at application rates of 0.1 or 0.21 kg ai/ha. There was no information on French GAP but conditions in three of the trials were according to Spanish Gap for legumes (0.1-0.21 kg ai/ha applied after weed emergence at 2-4-leaf stage). In the other trial application was at the early budding stage, which is not recommended practice. The residues in the trials according to GAP were <0.05-0.11 mg/kg.
Three supervised trials were carried out in France and four in Germany with applications of haloxyfop-R-methyl at 0.052-0.1 kg ai/ha. No information on GAP was available from these countries, but the trial conditions complied with the GAP of some East European countries (0.052-0.13 kg ai/ha, 60-day PHI, or 0.052-0.16 kg ai/ha, up to closing of canopy). The residues were <0.02-0.07 mg/kg. The trials in which the application rates were more than 30% below the maximum registered rate were not used in estimating the STMR.
Two French trials with racemic haloxyfop were according to maximum Spanish GAP; the residues were 0.06 and 0.11 mg/kg. Three German trials with 0.1 kg ai/ha of haloxyfop-R and 53-60 days PHI were comparable with maximum GAP in Poland (0.13 kg ai/ha, 60-day PHI). The residues in all three were <0.02 mg/kg.
The residues from the 5 trials in rank order were <0.02 (3), 0.06 and 0.11 mg/kg.
The Meeting estimated a maximum residue level 0.2 mg/kg and an STMR of 0.02 mg/kg for haloxyfop in peas (pods and succulent seeds).
Pea hay or fodder (dry). Six supervised trials on field peas in France and four in Germany complied with French GAP for fodder peas (0.052-0.1 kg ai/ha of haloxyfop-R applied up to early tillering); the residues were <0.02-0.1 mg/kg. The same data were evaluated by the 1995 Meeting in estimating a maximum residue level for dry pulses. The residues in the peas under the use pattern for fodder peas were below the maximum residue level estimated for dry pulses (0.2 mg/kg). Data were submitted to the 1995 Meeting on residues in pea haulms from four supervised trials in Germany and in whole plants of pigeon peas from two trials in Australia. However as the moisture content of the samples was not known the residues could not be referred to a dry weight basis, as required for residues in animal feeds (see report of 1980 JMPR, Section 2.8).
The Meeting could not estimate a maximum residue level for pea hay or fodder (dry).
Estimation of STMR and STMR-P levels for commodities for which maximum residue levels were estimated at the 1995 JMPR
The residue definition for the estimation of STMR or STMR-P levels should be the same as for the estimation of maximum residue levels (haloxyfop esters, haloxyfop and its conjugates expressed as haloxyfop), because no other metabolites were found in plant or animal metabolic studies.
Orchard crops. Haloxyfop is used in orchards to control grass weeds. Since the application is directed at the weeds growing at the base of the trees, residues in fruits will be caused only by drift contamination or translocation after the uptake of residues from soil by the roots. The Meeting therefore concluded that orchard crops should be evaluated as a single group.
Although bananas are not an orchard crop, they can be regarded as orchard crops for evaluation since the purpose and method of application is the same.
Eight supervised trials on citrus fruits, three on apples, nine on grapes and two on bananas were carried out in Australia, Brazil, France, Italy and New Zealand. The residues were below the limit of determination (<0.01- <0.1 mg/kg) in all the trials, except one in Australia on grapes which showed 0.03 mg/kg, even in trials carried out at excessive application rates.
The Meeting estimated a nil residue for orchard crops and bananas taking into consideration the use pattern and the fact that practically no uptake of residues from soil was observed.
The Meeting estimated an STMR of 0 mg/kg for haloxyfop in citrus fruits, apples, grapes and bananas.
Pulses (dry). Haloxyfop is registered for use on several pulses. The Meeting concluded that the supervised trials on pulses could be evaluated together because of the similarities in the use patterns and residue behavior.
Broad bean (dry). Conditions in two supervised trials (0.1 and 0.16 kg ai/ha, 103 and 171-day PHIs respectively) were comparable with maximum Australian GAP (0.1 kg ai/ha, 147-day PHI); the residues in both were <0.05 mg/kg. One trial in France was according to maximum Spanish GAP (0.21 kg ai/ha, with weeds at 2-4-leaf stage) and the residue was 0.03 mg/kg.
Chick-pea (dry). Three supervised trials in Australia (0.1 kg ai/ha, 78-99 days PHI) approximated maximum Australian GAP (0.1 kg ai/ha, 98-day PHI). The residues were <0.03, 0.03 and 0.04 mg/kg.
Common bean (dry). One Australian trial (0.16 kg ai/ha, 75-day PHI, 6-leaf stage) was comparable with maximum Australian GAP (0.16 kg ai/ha, 91-day PHI). The residue was 0.03 mg/kg. The Meeting considered that conditions in another Australian trial with applications at early budding were unpractical.
Field pea (dry). Two Australian supervised trials (0.21 kg ai/ha, 93-94-day PHI) could be used in the estimation of an STMR although the doses were higher than the maximum Australian rate (0.16 kg ai/ha, 91-day PHI) because the residues were below the limit of determination of 0.01 mg/kg.
Six supervised trials were carried out with racemic haloxyfop in France according to maximum Spanish GAP (0.21 kg ai/ha, with weeds at 2-4-leaf stage). The residues were <0.02 (3), <0.05, 0.06 and 0.14 mg/kg.
Two supervised trials in Australia with haloxyfop-R (0.1 kg ai/ha, 93-94-day PHI) were comparable with maximum Australian GAP (0.078 kg ai/ha, 91-day PHI). The residues in both were 0.01 mg/kg.
One trial in France (0.1 kg ai/ha, 68-day PHI) and one in Germany (0.1 kg ai/ha, 60-day PHI) were comparable with maximum GAP in East European countries (0.13 kg ai/ha, 60-day PHI or 0.16 kg ai/ha, up to closing of canopy). The residues were 0.06 and 0.03 mg/kg.
Lupin (dry). Four Australian supervised trials with racemic haloxyfop-etotyl at 0.078-0.12 kg ai/ha, with 92-115 days PHI were comparable with maximum Australian GAP (0.1 kg ai/ha, 119-day PHI). The residues were <0.05 (2), 0.03 and 0.11 mg/kg. One supervised trial with haloxyfop-R-methyl in Australia at 0.052 kg ai/ha, 92-day PHI, approximated maximum Australian GAP (0.052 kg ai/ha, 119-day PHI). The residue was 0.05 mg/kg.
Soya bean (dry). Three supervised trials (0.16 kg ai/ha, 102-122-day PHI) with racemic haloxyfop in Australia complied with maximum GAP (0.16 kg ai/ha, 119-day PHI). The residues were all <0.03 mg/kg.
Five supervised trials (0.12 kg ai/ha, 97-110-day PHI) in Brazil with racemic haloxyfop were according to maximum GAP conditions (0.12 kg ai/ha, 98-day PHI). The residues were <0.05 (4) and 0.06 mg/kg.
Four French and three Italian trials with haloxyfop-R at 0.1 kg ai/ha with PHIs of 76-133 days were according to maximum French GAP (0.1 kg ai/ha, up to early tillering). The residues were 0.02 (5), 0.07 and 0.09 mg/kg.
The haloxyfop residues in pulses from the 39 trials in rank order were <0.01 (4), <0.02 (8), <0.03 (4), 0.03 (5), 0.04, <0.05 (9), 0.05, 0.06 (3), 0.07, 0.09, 0.11 and 0.14 mg/kg. The Meeting estimated an STMR of 0.03 mg/kg for haloxyfop in pulses (dry).
Potatoes. Nineteen supervised trials were carried out with racemic haloxyfop in Belgium, Germany, The Netherlands, Norway, Sweden and the UK according to maximum Irish GAP (0.21 kg ai/ha, application up to 60 cm height of crop).
The residues from the 19 trials in rank order were 0.01 (3), 0.01, 0.02, 0.03 (3), 0.04 (5), 0.05, 0.06, 0.07 (3) and 0.1 mg/kg. The Meeting estimated an STMR of 0.04 mg/kg for haloxyfop in potatoes.
Sugar beet, fodder beet and sugar beet leaves or tops
The Meeting concluded that supervised trials on sugar beet and fodder beet could be evaluated together because the use pattern of haloxyfop on these crops is the same and the residue behavior is expected to be similar.
Sugar beet. Twelve supervised trials were carried out in France and 13 in the UK with racemic haloxyfop according to maximum French GAP (0.21 kg ai/ha, up to early weed tillering). In the French trials the residues in the roots were <0.01, <0.02 (3), 0.02, <0.03 (3), 0.03 (2), 0.05 and 0.1 mg/kg. In the UK trials the residues in the roots were <0.01 (3), 0.01 (2), 0.02 (2), <0.03, 0.03 (2), 0.05 (2) and 0.23 mg/kg and in the leaves or tops <0.02 (3), 0.02, <0.03 (3), 0.03, 0.04 (2), 0.09, 0.11 and 0.28 mg/kg.
Eight supervised trials were carried out with racemic haloxyfop in Germany according to maximum GAP (0.21 kg ai/ha, 90-day PHI). The residues in the roots were <0.005, 0.01 (3), 0.02, 0.04, 0.14 and 0.16 mg/kg and in the leaves or tops <0.01, <0.02 (2), 0.03, 0.04, 0.08, 0.28 and 0.3 mg/kg.
In seven supervised trials with haloxyfop-R in France, Germany and Italy according to maximum French GAP (0.1 kg ai/ha, up to early weed tillering) the residues in the roots were 0.01, <0.02 (3), 0.02, 0.03 and 0.06 mg/kg. Residues in the leaves or tops in four of the trials were <0.02, 0.09 (2) and 0.14 mg/kg.
Fodder beet. In five supervised trials with racemic haloxyfop in Germany according to maximum GAP (0.21 kg ai/ha, 90-day PHI) the residues in the roots were <0.01 (2), 0.01, 0.03 and 0.04 mg/kg and in the leaves or tops <0.02 (3), 0.03 and 0.05 mg/kg.
The residues in the roots from the 45 trials in rank order were <0.005, <0.01 (6), 0.01 (6), <0.02 (6), 0.02 (5), <0.03 (4), 0.03 (6), 0.04 (2), 0.05 (3), 0.06, 0.1, 0.14, 0.16 and 0.23 mg/kg.
The residues in the leaves or tops from 30 of the trials in rank order were <0.01, <0.02 (9), <0.02, <0.03 (3), 0.03 (3), 0.04 (3), 0.05, 0.08, 0.09 (3), 0.11, 0.14, 0.28 (2) and 0.3 mg/kg. However, because the Meeting did not estimate a maximum residue level for the leaves or tops, no STMR was estimated.
The Meeting estimated an STMR of 0.02 mg/kg for haloxyfop in sugar beet and fodder beet.
Rice. In nine supervised trials on rice with racemic haloxyfop in Brazil, Colombia, Mexico and Costa Rica the application rates were comparable with the maximum rates in some South American countries of 0.11 kg ai/ha. All the residues were <0.01 mg/kg.
The Meeting estimated an STMR of 0 mg/kg for haloxyfop in husked and polished rice taking into consideration that no residue was found even in trials carried out at an excessive dose rate.
Cotton seed. Four supervised trials with racemic haloxyfop in Australia according to maximum Australian GAP (0.16 kg ai/ha, 119-day PHI). The residues were <0.05 (2), 0.06 and 0.08 mg/kg. Conditions in four supervised trials carried out with racemic haloxyfop in Brazil (0.24 kg ai/ha applied 22-40 days after planting, 93-112-day PHI) were comparable with maximum GAP in Paraguay (0.18 kg ai/ha, applied with weeds at 2-4 leaf stage). The residues were <0.1 (2), 0.1 and 0.2 mg/kg.
The residues from the 8 trials in rank order were <0.05 (2), 0.06, 0.08. <0.1 (2), 0.1 and 0.2 mg/kg. The Meeting estimated an STMR of 0.09 mg/kg for haloxyfop in cotton seed.
Peanuts. Two trials with racemic haloxyfop in Argentina were at dose rates of 0.24 and 0.4 kg ai/ha, comparable to maximum GAP (0.3 kg ai/ha, weeds at 2-4-leaf stage). The residues were 0.03 and <0.05 mg/kg.
Three supervised trials with racemic haloxyfop in Australia were at 0.12-0.16 kg ai/ha, 98-117 days PHI, similar to maximum GAP (0.16 kg ai/ha, 119 days PHI). The residues were <0.03 and 0.03 (2) mg/kg.
The residues from the 5 trials were <0.03, 0.03 (3) and <0.05 mg/kg. The Meeting estimated an STMR of 0.03 mg/kg for haloxyfop in peanuts.
Rape seed and rape fodder. Two supervised trials with racemic haloxyfop in Australia at a rate of 0.16 kg ai/ha, slightly higher than maximum GAP (0.1 kg ai/ha, 119-day PHI). In this case the influence of the dose rate on the residue of haloxyfop is assumed to be little, since the application was made at an early growth stage (2-6 leaves) causing less direct exposure of the crops to haloxyfop. The Meeting therefore concluded that the trials were comparable with GAP. The residues in the rape seed were <0.03 and 0.07 mg/kg.
Thirteen supervised trials were carried out with racemic haloxyfop in France according to maximum French GAP (0.21 kg ai/ha, up to early tillering). The residues in the rape seed were <0.05 (7), 0.05, 0.09, 0.14, 0.145, 0.37 and 0.66 mg/kg. Seven of the French trials also included treatments comparable with maximum Spanish GAP (0.42 kg ai/ha, applied with weeds at 2-4 leaf stage). The residues in the seed were <0.05, 0.05 (2), 0.17, 0.315, 0.32 and 1.68 mg/kg.
Six supervised trials with racemic haloxyfop in Germany were according to maximum GAP (0.21 kg ai/ha, post weed emergence). The residues were <0.05, 0.1, 0.13 (2), 0.15 and 0.77 mg/kg in the seed and <0.05 (2), 0.09 and 0.12 mg/kg in four samples of fodder.
Eighteen supervised trials (three trials in 1984 were counted as two trials each, because the applications were made in the year before harvest or the year of harvest) with racemic haloxyfop in the UK were according to maximum French or German GAP (0.21 kg ai/ha, up to early tillering or post weed emergence). The residues were <0.05 (11), 0.05, 0.06, 0.09, 0.1, 0.11, 0.44 and 0.64 mg/kg in the seed and <0.05 (9), 0.05, 0.07 and 0.08 mg/kg in twelve samples of fodder.
Three supervised trials with haloxyfop-R in France and two in Germany which complied with maximum French GAP (0.1 kg ai/ha, up to early tillering) showed residues in the seed of <0.05 (4) and 0.07 mg/kg. The residues in rape fodder in the German trials were both <0.05 mg/kg.
The residues in the rape seed from the 51 trials in rank order were <0.03, <0.05 (24), 0.05 (4), 0.06, 0.07 (2), 0.09 (2), 0.1 (2), 0.11, 0.13 (2), 0.14, 0.145, 0.15, 0.17, 0.315, 0.32, 0.37, 0.44, 0.64, 0.66, 0.77 and 1.68 mg/kg. However the residues in the seven French trials in which application was at the maximum Spanish GAP rate (0.42 kg ai/ha) seem to be from a different population from the others. The Meeting concluded that an STMR for haloxyfop in rape seed should be estimated form this higher population. The residues in rape seed from these 7 trials in rank order were <0.05, 0.05 (2), 0.17. 0.315, 0.32 and 1.68 mg/kg.
The residues in rape fodder from 18 trials in rank order were <0.05 (13), 0.05, 0.07, 0.08, 0.09 and 0.12 mg/kg. The Meeting estimated an STMR of 0.17 mg/kg for haloxyfop in rape seed.
Sunflower seed. Eight supervised trials were carried out with racemic haloxyfop in Argentina, Australia and France at the relevant maximum GAP (rates of 0.3, 0.16 and 0.21 kg ai/ha respectively). The residues were <0.03 (2), 0.03, 0.04, <0.05 (2), 0.143 and 0.16 mg/kg.
One supervised trial with haloxyfop-R in France at the maximum GAP rate of 0.1 kg ai/ha gave a residue of 0.07 mg/kg.
The residues from the 9 trials in rank order were <0.03 (2), 0.03, 0.04, <0.05 (2), 0.07, 0.143 and 0.16 mg/kg. The Meeting estimated an STMR of 0.05 mg/kg for haloxyfop in sunflower seed.
Alfalfa. In two supervised trials with racemic haloxyfop in Australia the conditions (0.21 kg ai/ha, 21-22 days PHI) were comparable with maximum GAP (0.16 kg ai/ha, 21-day PHI). The residues were 2.45 and 3.11 mg/kg. In two further trials with haloxyfop-R in Australia the conditions (0.1 kg ai/ha, 22-day PHI) were again comparable with maximum GAP (0.078 kg ai/ha, 21-day PHI) and the residues were 1.8 and 2.21 mg/kg.
The residues from the 4 trials in rank order were 1.8, 2.21, 2.45 and 3.11 mg/kg.
Pasture. Four supervised trials with racemic haloxyfop and two with haloxyfop-R in Australia were according to maximum GAP (0.1 kg ai/ha racemic haloxyfop, 0.052 kg ai/ha haloxyfop-R, 7-day PHI in both cases). The residues from the 6 trials in rank order were 0.49, 0.99, 1.47, 1.71, 2.04 and 3.35 mg/kg.
