RESIDUE AND ANALYTICAL ASPECTS
Tebuconazole is a triazole fungicide used as a seed dressing and spray. It was first evaluated in 1994 when use patterns, methods of residue analysis, results from supervised trials, studies of metabolism and environmental fate, and storage and processing data were reported by the manufacturer. MRLs were recommended for barley, barley straw and fodder, grapes, peanut, peanut fodder, rape seed, rye, rye straw and fodder, summer squash, tomatoes, wheat, wheat straw and fodder, cattle edible offal, meat and milk, and chicken edible offal, eggs and meat. In studies of metabolism in wheat, grapes and peanuts, tebuconazole was the significant residue. Information received since the 1994 evaluation was reviewed by the present Meeting.
New methods of analysis of plant materials and soil were reported. After extraction with organic solvents and clean-up on Florisil, C-18 or silica columns, and/or gel permeation chromatography, tebuconazole is determined by gas chromatography with a nitrogen-phosphorus detector. In some cases, no clean-up step was required. The limit of determination ranged from 0.01 to 0.05 mg/kg.
Two hundred and eighteen trials were reported to the Meeting, with information on registered uses on the relevant crops. Processing studies were conducted on plums, grapes and peanuts.
The Meeting concluded that the definition of the residue for compliance with MRLs and for estimations of dietary intake should be tebuconazole.
GAP is established for the use of tebuconazole on apples in Brazil, France and Indonesia and on apples and pears in Italy, Israel, Turkey and Spain. PHIs vary from 10 to 30 days. There are proposed uses on apples and pears in the USA and apples in Germany in which the recommended PHIs are 75 and 56 days respectively. Results from trials on pome fruits show that residues decrease continuously with time after sprayed applications of tebuconazole.
Apples. In one trial in Brazil, two in Italy and one in Spain according to local GAP (1 to 6 applications of 0.09 to 0.23 mg/kg ai/ha), residues at a PHI of 20-21 or 28 days in rank order were 0.12, 0.13, 0.18 and 0.20 mg/kg. In one further trial in France according to current GAP which was reported to the 1994 Meeting, the residue at a PHI of 21 days was 0.06 mg/kg. In three trials in Brazil, two in France and ten in Korea with more applications and/or higher rates (up to 1.25 kg ai/ha) than recommended GAP, residues varied from 0.04 to 0.5 mg/kg with PHIs of 14 to 35 days.
In two trials in Canada, 18 in the USA and 11 in Germany with applications below, at, or above proposed GAP rates in Germany and the USA (1-6 x 0.1-0.25 kg ai/ha) most residues were below the LOD of 0.01 to 0.02 mg/kg, with 7 values of 0.02-0.04 mg/kg at PHIs of 56 days or longer.
Pears. In one trial in Spain according to GAP (4-6 applications of 0.1-0.15 kg ai/ha) the residue was 0.09 mg/kg at a PHI of 21 days. In six trials in the USA at or below the proposed rates the residues varied from below the LOD (0.01 mg/kg) to 0.03 mg/kg after PHIs of 63 to 106 days.
Three trials in Italy according to GAP (1-4 applications of 0.15-0.28 kg ai/ha, PHI 15 days) and one trial in France according to Spanish GAP were reported in 1994. The residues in Italy were 0.43, 0.12 and 0.20 mg/kg after 14, 10 and 10 days respectively, and in France <0.05 mg/kg after 14 and 30 days. As the residues in the pears appeared to decrease slowly the residues after 10 and 15 days would probably be similar.
As GAP for apples and pears is similar in countries with registrations for both, residues from trials according to GAP in the two crops can be considered to form a single population. The residues from trials according to established GAP in rank order (median underlined) were 0.05, 0.06, 0.09, 0.12 (2) 0.13, 0.18, 0.20 (2) and 0.43 mg/kg.
The Meeting estimated a maximum residue level of 0.5 mg/kg and an STMR of 0.12 mg/kg for pome fruits.
Tebuconazole is registered for use on peaches in Chile, France, Italy and Peru, on plums in Israel and on peaches and cherries in the USA. PHIs vary from 0 in the USA to 35 days in Chile. The results from trials on stone fruit show that residues after spray applications decrease steadily and fairly slowly.
Cherries. Tebuconazole is registered for use on cherries only in the USA. In five trials in Italy at or below proposed Italian GAP (1 or 2 applications of 0.28 kg ai/ha), residues in the fruit with and without stone were 0.18-0.50 mg/kg after 5 to 7 days.
GAP in the USA allows 1-6 applications at a nominal rate of 0.25 kg ai/ha with a 0-day PHI. Twelve trials were carried out at a nominal rate of 0.19 kg ai/ha, the actual rate depending on the size of the trees. The residues at a PHI of 0 days in rank order were 0.09, 0.19, 0.31, 0.40, 0.41, 0.53, 0.61, 0.76 (median), 0.92, 1.2, 1.4 and 3.1 mg/kg (the last from 7 applications). The residues shown bold were from the highest actual application rates and have been used to estimate an STMR. The residue in another trial at half the application rate was 1.0 mg/kg at a 0-day PHI.
The Meeting estimated a maximum residue level of 5 mg/kg and an STMR of 0.76 mg/kg.
Peaches and nectarines. Two trials on peaches in France and one on peaches and two on nectarines in Italy were according to Italian GAP (1 or 2 x 0.15-0.3 kg ai/ha). The residues ranged from below the LOD (0.02 mg/kg) to 0.17 mg/kg in stoned or whole fruit at a PHI of 7 to 10 days. In four trials on peaches in France according to current GAP, reported in 1994, the residues in stoned and whole fruit at a PHI of 7 days varied from 0.03 to 0.22 mg/kg.
In eight trials on peaches in the USA according to GAP (0.25 kg ai/ha), residues in whole fruit at a PHI of 0 days were 0.20 to 0.81 mg/kg, and in one trial with an application below the GAP rate the residue was 0.04 mg/kg.
Residues from trials according to GAP in whole and stoned peaches in rank order were 0.03, 0.05, 0.11 (2), 0.13, 0.20, 0.21, 0.22, 0.26, 0.34, 0.44, 0.46 and 0.81 mg/kg.
The Meeting estimated a maximum residue level of 1 mg/kg and an STMR of 0.21 mg/kg for peaches.
Plums. Only Israel has a registered use for tebuconazole on plums. There is a proposed use in France.
In France, residues in the stoned or whole fruit from nine trials at a higher rate or spray concentration than the proposed use (1-3 applications of 0.13-0.15 kg ai/ha) ranged from 0.03 to 0.38 mg/kg at a PHI of 7 days. In ten further trials according to the proposed use, residues ranged from below the LOD (0.01 or 0.02 mg/kg) to 0.1 mg/kg after PHIs of 7 to 79 days.
As no trials according to approved GAP were reported, the Meeting could not estimate a maximum residue level.
Grapes. Tebuconazole is registered for use on grapes in Brazil, Chile, France, Germany, Israel, Italy, Spain and South Africa. The 1994 JMPR recommended an MRL of 2 mg/kg.
In 14 trials in the USA at the use pattern for which registration has been applied and a PHI of 14 days the residues were between 0.10 and 1.7 mg/kg, and in one further trial 4.0 mg/kg at 13 days.
As no additional results from trials according to GAP were reported, the Meeting made no change to the previous recommendation.
Bananas. Tebuconazole is registered for use on bananas in Australia, Cameroon, Colombia, Costa Rica, Ecuador, Guatemala, Honduras, Indonesia, the Ivory Coast, Nicaragua, the Philippines and the USA. A PHI of 0 or 1 day is recommended in all these countries.
In one trial in Australia and seven in the USA according to national GAP (5-7 applications of 0.1 kg ai/ha, bagged bananas), residues in the whole fruit were <0.01 (6), 0.01 and 0.03 mg/kg and in the pulp 0.01 (5) and <0.05 mg/kg. Three other trials in Australia, one at a lower and two at a higher rate, gave similar results and could be used to support the results in the trials according to GAP. Two trials on unbagged bananas gave residues of 0.16 mg/kg in the whole fruit at a PHI of 1 day. Two trials in Brazil giving residues in the pulp below the LOD (0.1 mg/kg) after 14 days could not be evaluated owing to the lack of information on GAP.
The Meeting estimated a maximum residue level of 0.05 mg/kg and an STMR (based on residues in the pulp) of 0.01 mg/kg for tebuconazole in bananas.
Tebuconazole is registered for use on garlic and onions in Brazil, Israel, and Spain (soil drench) and on onions in New Zealand and South Africa.
Garlic. In one trial in Brazil approximating GAP (1-4 applications of 0.25 kg ai/ha) and three others at a higher rate or with 6 applications, residues were below the LOD (0.05 mg/kg) after the GAP PHI of 14 days. Five trials in France according to proposed GAP gave residues from below the LOD (0.02 mg/kg) to 0.06 mg/kg after a PHI of 21 days.
In seven trials in Korea at various application rates and with spray or soil drench applications, residues ranged from below the LOD after 275 days to 1.4 mg/kg after 51 days. No GAP was available with which to evaluate the trials.
The data from trials according to GAP were insufficient to estimate a maximum residue level.
Onions. In one trial in France, one in Germany, one in Italy and four in The Netherlands, at or close to the proposed German use pattern (1-2 foliar applications of 0.25 kg ai/ha), and in four trials in Brazil which exceeded GAP conditions (1-4 x 0.25 kg ai/ha), residues after 14-28 days ranged from below the LOD (0.02, 0.05, or 0.1 mg/kg) to 0.3 mg/kg. In Spain, where soil drench application is recommended, two trials with foliar applications gave residues at or below the LOD (0.02 mg/kg) after 14 days.
In two trials in New Zealand according to GAP (2-3 foliar applications of 0.38 kg ai/ha), the residues were 0.14 mg/kg at day 28 and below the LOD (0.05 mg/kg) after 76 days. The GAP PHI is 35 days. In two trials in Australia with 1 or 2 applications of 0.5 kg ai/ha, the residues were below the LOD (0.01 mg/kg) and 0.3 mg/kg after 79 and 154 days respectively.
There were insufficient data from trials according to GAP to estimate a maximum residue level.
Cucumbers. Tebuconazole is registered for use on cucumbers in Chile, Israel and Spain. PHIs vary from 7 to 35 days. There is a proposed use in Italy.
In two trials in Italy according to the proposed rate (1-4 applications of 0.125 kg ai/ha), the residues at a PHI of 7 days were below the LOD (0.02 mg/kg). Eight trials were conducted in Spain according to current GAP (1-3 applications of 0.2-0.3 kg ai/ha), five indoor trials reported to the present Meeting and three field trials reported to the 1994 Meeting. The residues at a PHI of 7 days in rank order were 0.02, 0.02, 0.03 (2), 0.04, 0.08, 0.10 and 0.19 mg/kg.
The Meeting estimated a maximum residue level of 0.2 mg/kg and an STMR of 0.035 mg/kg.
Sweet peppers. Tebuconazole is registered for use on sweet peppers only in Spain, with 1-3 applications of 0.2-0.3 kg ai/ha.
In three trials in Spain reported to the present Meeting and four reported in 1994, all according to current GAP, the residues at a PHI of 7 days in rank order were 0.07, 0.13, 0.14 (2), 0.18, 0.23 and 0.36 mg/kg.
The Meeting estimated a maximum residue level of 0.5 mg/kg and an STMR of 0.14 mg/kg.
Tebuconazole is registered for use on barley, oats and/or wheat as a seed or foliar treatment in many countries, including Australia, Spain, South Africa, Germany, the UK and the USA.
Barley. The 1994 JMPR recommended an MRL of 0.2 mg/kg based on residues from foliar applications.
In nine trials in the USA with seed treatment according to GAP, residues in grain samples were below the LOD (<0.01 (4) and 0.02 (5) mg/kg) at harvest (81 to 129 days). In one trial a 12-fold rate gave a residue of 0.01 mg/kg.
The Meeting did not change the 1994 estimate of 0.2 mg/kg as a maximum residue level.
Oats. In eleven trials with seed treatment in the USA according to GAP, all residues in grain samples were below the LOD (0.01 mg/kg) at harvest (78 to 122 days). The residues in straw and forage were also all below the LOD (0.01, 0.02 or 0.06 mg/kg). Residues in hay, determined in 5 trials, were <0.01 mg/kg in 4 trials and 0.02 mg/kg in the fifth.
Residues in the grain from trials with foliar treatments according to GAP (two in Australia and one in Sweden) reported to the 1994 Meeting were 0.06, 0.09 and 0.12 mg/kg.
On the basis of the US trials and the practical LOD for rye of 0.05 mg/kg indicated by the 1994 JMPR, the Meeting estimated a maximum residue level of 0.05* mg/kg for tebuconazole in oats. As the residues in straw, forage and hay from seed treatments were also below the LOD, except in one sample of hay, the Meeting estimated an STMR of 0 mg/kg for tebuconazole in oats. The Meeting recognized that these estimates would not accommodate foliar applications.
Wheat. The 1994 JMPR recommended an MRL of 0.05 mg/kg on the basis of residues from foliar applications.
In six trials with seed treatment according to GAP in the USA, the residues in grain samples at harvest (81 to 275 days) were below the LOD (0.01 or 0.04 mg/kg). The residues in 13 trials with foliar treatment in Germany and the UK reported to the 1994 JMPR, according to GAP at that time, were <0.05 mg/kg.
The Meeting confirmed the previous recommendation of 0.05 mg/kg as an MRL.
Peanuts. Tebuconazole is registered for use on peanuts in Australia, Argentina, Brazil, Guatemala, Indonesia, Israel, Nicaragua, South Africa and the USA. The 1994 JMPR recommended an MRL of 0.05 mg/kg.
In thirteen US trials with 7 applications, instead of the 4 allowed by GAP, at rates slightly above the authorized 0.23 kg ai/ha, the residues in the kernels at or about the GAP PHI of 14 days in rank order were <0.01 (4), 0.01, 0.03 (3), <0.05 (4) and 0.08 mg/kg.
The Meeting confirmed the 1994 JMPR recommendation, as it is unlikely that residues would exceed 0.05 mg/kg.
Plums. Plum trees were treated three times with 0.25 kg ai/ha. In a processing study of samples taken after 7 days residues were reduced by a factor of 0.7 in washed and preserved plums, remained unchanged in jam and were increased by a factor of 4.7 in dried prunes. The Meeting agreed that one study was not sufficient to estimate processing factors.
Grapes. Grapes taken after the last of four applications of 0.25 kg ai/ha were processed. Processing factors were 0.9 and 1.3 for sun- and oven-dried raisins respectively, 0.5 for juice, 4 and 10.6 for sun- and oven-dried raisin waste, 7.5 for wet pomace and 21.9 for dry pomace. Processing studies reviewed by the 1994 JMPR showed processing factors of 1.4 and 1.2 for sun- and oven-dried raisins, 0.04, <0.05, 0.06 and 0.4 for juice, 2.7 and 1.5 for sun-and oven-dried raisin waste, and 1.8 and 5.8 for wet and dry pomace.
Residues in grapes, must and wine were determined in 37 trials reported to the 1994 JMPR (2 to 5 applications of 0.3-0.625 kg ai/ha). In three of these trials juice was also analysed but the results were reported incorrectly by the company in 1994; the correct values were supplied for the present Meeting. The mean and individual processing factors from all the trials were juice 0.21 (0.04, 0.05, 0.06, 0.4, 0.5), raisins 1.2 (0.9, 1.2, 1.3, 1.4), raisin waste 4.7 (4, 10.6, 2.7, 1.5), wet pomace 4.7 (1.8, 7.5), dry pomace 13.9 (5.8, 21.9), must 0.36 (range 0.12-0.78), wine 0.25 (range 0.05-0.78).
On the basis of the draft MRL of 2 mg/kg for grapes and the processing factor of 1.2 for raisins, the Meeting estimated a maximum residue level of 3 mg/kg for tebuconazole in dried grapes.
Peanuts. Plants treated at 5 times the maximum rate gave processing factors of 0.9 for peanut meal, 3.4 for soapstock, 2.0 for crude oil and 0.1 for refined oil. The Meeting agreed that one study was not sufficient to estimate processing factors for peanut products.