Teflubenzuron is an acylurea insecticide whose major use is for the control of a wide range of insect pests (lepidopterous and coleopterous larvae being most sensitive) and some mites in fruits, vegetables, cereals, nuts and seeds. At the request of the manufacturer, the compound was removed from the review schedule of the FAO Panel of the 1994 JMPR and its residue aspects were reviewed for the first time by the present Meeting.
Teflubenzuron is formulated as suspension concentrates containing 50 or 150 g ai/l. The active ingredient is a crystalline solid, virtually insoluble in water, soluble in medium-polarity solvents, not hydrolysed at pH 5 but hydrolysed at room temperature and pH 7 and 9 with half-lives of 8 months and 8 days respectively.
The fate of residues has been studied in animals, plants and soil.
Studies on rats, lactating goats and laying hens showed poor absorption from the gastrointestinal tract, rapid elimination mainly in the faeces or excreta, excretion largely as the unchanged parent compound, and in the case of goats no accumulation in any organ or tissue, or milk.
In goats and hens, 96-99% of administered doses were eliminated in the faeces or excreta and most of the radioactivity was associated with the parent compound. That portion of a dose which is absorbed appears to be metabolized in the liver and conjugated before elimination, mainly in the bile. In hens only, the absorbed fraction appears to be passed into body tissues, especially fatty tissues and egg yolk. The major part of the residue in fat and egg yolk was identified as teflubenzuron. The elimination of radioactivity in the milk of goats accounted for 0.03% of the total administered dose.
Studies of plant metabolism with foliar applications of teflubenzuron to apple trees, potato plants and cotton plants have shown that the insecticide does not penetrate into leaves, fruit or potato tubers. More than 98% of the extractable radioactivity was in the unchanged compound and was situated on the surface of the treated plant part. It was concluded that there is no systemic transport and no metabolism.
In a study on spinach, the residue was also almost all (99%) on the surface. The parent compound amounted to 95% of the total radioactive residue at day 0 and 77% at day 15. The fact that the radioactivity was almost completely removed by surface extraction indicates that any significant degradation is photolytic rather than metabolic.
Investigation of the degradation of teflubenzuron in soil showed that microbiological activity is of primary importance. In very humic soil degradation was more rapid than in sandy loam, with a half-life of two weeks in humic sand and six weeks in sandy loam soil. In sandy loam, teflubenzuron was degraded about six times as rapidly under anaerobic as under aerobic conditions.
Under both aerobic and anaerobic conditions, 3,5-dichloro-2,4-difluorophenylurea and 3,5-dichloro-2,4-difluoroaniline were the major products.
The adsorption and desorption of teflubenzuron was studied in four different types of soil. It was found that sand adsorbed 96.9%, sandy loam 98.8%, silt loam 99.1%, and clay loam 99.4% of the amount dissolved in the aqueous control sample after a 6-h contact period, and 6.1%, 3.7%, 1.3% and 1.3% of the adsorbed radioactivity respectively could be desorbed again during two desorption periods of 24 h each.
Teflubenzuron itself shows practically no tendency to migrate once it is applied to soil. This is attributable to the very low solubility of the compound in water, very slight leaching and high adsorption to all types of soil tested.
Residues were not significant in rotational crops. After applying [14C]teflubenzuron (0.5 kg ai/ha) and ageing the soil for 30, 120 or 360 days, the total radioactive residues expressed as teflubenzuron equivalents were 0.007, 0.006 and 0.002 mg/kg in head lettuce, 0.005, 0.003 and 0.002 mg/kg in wheat grain, 0.24, 0.088 and 0.035 mg/kg in wheat straw, and 0.026, 0.013 and 0.005 mg/kg in carrots. The results show that rotational crops, with the exception of cereal straw, will not contain residues above 0.05 mg/kg.
The biodegradation of [14C]teflubenzuron was determined in two water/sediment systems. The half-life was 6-7 weeks. Two major degradation products were found; one was identified as 3,5-dichloro-2,4-difluorophenylurea.
Analytical methods are available for the determination of teflubenzuron residues in plant and animal materials, soil, water and air. Teflubenzuron is extracted from plants with acetone, from soil with an acetone/water mixture and from animal products such as muscle, liver, kidney, fat, skin, milk and eggs with acetonitrile or methanol. It is extracted from water on a C18-"Bondelut" solid-phase column. Clean-up is carried out by solvent partition followed by gel-permeation chromatography and/or silica gel column chromatography. The residue is determined by reversed-phase HPLC with ultraviolet detection at 254 nm or by capillary gas chromatography with mass- selective detection. The limits of determination were 0.01 mg/kg in plants, soil and animal products and 0.0001 mg/l in water. In some supervised trials (e.g. on potatoes), an analytical method with an LOD of 0.05 mg/kg was used. For the analysis of air, the air is sucked through a Tenax or XAD column and the adsorbed teflubenzuron is eluted and determined by reversed-phase HPLC with UV detection or by GLC with a mass-selective detector as a confirmatory method. The LOD was 10 mg/m3. The stability of stored analytical samples of teflubenzuron in apples, pears, potatoes and cabbage was investigated over a 3-year period. Losses of the insecticide were from about 6% from cabbage to 25% from apples.
Because the residues in plants and animal products are generally mostly the parent compound, the Meeting concluded that for both regulatory and risk assessment purposes the residue should be defined as teflubenzuron. The log Pow of 4.56 and the results of a feeding study on laying hens, with residues in eggs and fat, indicate the fat-soluble nature of teflubenzuron. In contrast to the results with hens, a feeding study on dairy cattle showed little or no transfer of the pesticide from animal feed in milk, fat and tissues.
Definition of the residue for compliance with MRLs and for estimation of dietary intake: teflubenzuron
The residue is fat-soluble. Supervised residue trials gave the following results.
Citrus fruits. The use of teflubenzuron is registered in the United Arab Emirates and South Africa, where 1-2 treatments with a spray concentration of 0.0038 or 0.003 kg ai/hl and PHIs of 7 or 30 days are recommended respectively. In Saudi Arabian GAP the spray concentration is 0.011 kg ai/hl with a 21-day PHI. In total, 20 supervised trials were carried out in Brazil, South Africa and the USA.
The whole fruit was analysed only in three US trials (one on grapefruit, two on oranges) but there is no registered use in the USA. No residue was found in the whole fruit (<0.05 mg/kg), 45 and 76 days after three spray treatments (0.005-0.006 kg ai/hl, 0.11 kg ai/ha).
One trial in Brazil and three in South Africa approximated South African GAP. The residues were 0.01, <0.05 (2) and 0.1 mg/kg in the pulp and 0.24, 0.26, 0.34 and 0.47 mg/kg in the peel at PHIs of 25-35 days. In three trials, samples were also analysed after 6 or 7 days, the PHI in the United Arab Emirates. The residues were all <0.05 mg/kg in the pulp and 0.36, 0.37 and 0.39 mg/kg in the peel. Calculation of the residues in the whole fruit was not possible because no further data were reported.
The Meeting concluded that no acceptable residue data on a whole fruit basis had been submitted and could not estimate a maximum residue level for teflubenzuron in citrus fruits.
Pome fruits. Teflubenzuron is registered for use on apples and pears in Europe (France, Greece, Italy, The Netherlands, Poland, Portugal, Spain, Switzerland), Africa (Jordan, The United Arab Emirates) and Argentina (apples only).
The residue data after 1-4 treatments of apples with 0.11-0.21 kg ai/ha (0.011 kg ai/hl) at PHIs of 24-28 days in Germany and the UK could be related to Dutch GAP (1-3 x 0.11-0.16 kg ai/ha, 0.011 kg ai/hl, 28-day PHI). The residues in ten German and two UK trials were 0.05, 0.09, 0.11, 0.19 (2), 0.23 (2), 0.24, 0.27, 0.29, 0.36 and 0.37 mg/kg.
The Italian trials on apples were evaluated with reference to the Southern European GAP (Italy, Greece and Switzerland). Two trials approximated Italian GAP with 1-3 treatments of 0.15-0.16 kg ai/ha and a PHI of 14 days. The residues were 0.23 and 0.27 mg/kg. Two other trials with 2 treatments at 0.24-0.27 kg ai/ha were close to Greek GAP (2-3 treatments, 0.21 kg ai/ha, 30-day PHI) and resulted in residues of 0.45 and 0.51 mg/kg after 28 days.
Swiss GAP (2-3 treatments, 0.3 kg ai/ha, 21-day PHI) was approximated by one Italian trial on apples and three on pears (2-3 treatments with 0.24-0.27 kg ai/ha, 21-day PHI). The residues were 0.65 mg/kg in apples, and 0.43, 0.6 and 0.71 mg/kg in pears.
Many residue trials on apples and pears were conducted in France, but they did not accord with French or other European GAP. No GAP was available for the USA so the results could not be evaluated.
The Meeting estimated a maximum residue level of 1 mg/kg for teflubenzuron in pome fruits.
The teflubenzuron residues in apples in rank order in the German and UK trials were 0.05, 0.09, 0.11, 0.19 (2), 0.23 (2), 0.24, 0.27, 0.29, 0.36 and 0.37 mg/kg. The residues from trials on apples and pears in Southern Europe belonged to another population: 0.23, 0.27, 0.43, 0.45, 0.51. 0.6, 0.65 and 0.71 mg/kg. The Meeting therefore estimated an STMR level of 0.48 mg/kg for teflubenzuron in pome fruits.
Stone fruits. Teflubenzuron is registered in Switzerland for stone fruits, in Italy for peaches and nectarines, and in Saudi Arabia for peaches with 1-3 treatments of 0.11-0.12 kg ai/ha and a 21-day PHI. In Poland, one treatment of 0.11 kg ai/ha and a PHI of 28 days are recommended for orchards.
Three German trials on cherries with 2 x 0.16 kg ai/ha, approximately Swiss GAP, resulted in residues of 0.24 (2) and 0.25 mg/kg.
The Meeting concluded that there were not enough data to estimate a maximum residue level for teflubenzuron in cherries.
Trials on plums which approximated Swiss GAP were available from Germany (5) and Italy (6). After two applications of 0.16 kg ai/ha in Germany residues of teflubenzuron in samples taken at day 21 were 0.01 (2), 0.01 and 0.04 (2) mg/kg. After two applications of 0.12 kg ai/ha in Italy the residues at 21-30 days were 0.03 (2), 0.04 (2) and 0.08 (2) mg/kg.
The Meeting estimated a maximum residue level of 0.1 mg/kg for teflubenzuron in plums.
The residues from all the relevant trials in rank order were 0.01 (2), 0.01, 0.03 (2), 0.04 (4) and 0.08 (2) mg/kg, with a median value of 0.04 mg/kg. The Meeting estimated an STMR level of 0.04 mg/kg for teflubenzuron in plums.
Two trials on nectarines were carried out in Italy. After two applications of 0.12 kg ai/ha the residues in the fruits were 0.08 mg/kg and 0.04 mg/kg at 35 and 56 days after the last treatment respectively. No information on residues at the approved PHI of 21 days was available.
In eight trials in France and two in Italy peaches were treated 1-6 times with 0.1-0.19 kg ai/ha. Four trials with 2-3 x 0.1 kg ai/ha approximated Italian and Swiss GAP and resulted in residues of 0.1, 0.13, 0.24 and 0.34 mg/kg at 20-24 days.
The Meeting could not estimate a maximum residue level for teflubenzuron in nectarines and peaches because there were insufficient data from trials according to GAP.
Berries and other small fruits. The only registered uses of teflubenzuron on berries are on grapes with 2 x 0.09-0.096 kg ai/ha in Italy, Spain (both PHIs 28 days) and Switzerland (PHI 21 days), and 2 x 0.011 kg ai/hl and a 21-day PHI in Saudi Arabia.
Trials on grapes were conducted in France, Germany and Italy between 1982 and 1984. In the 10 French trials, grapes were treated once at rates of 0.1-0.3 kg ai/ha. Residues of teflubenzuron 58-77 days after treatment ranged from <0.05 to 0.86 mg/kg. In the 5 German trials, two treatments of 0.15-0.23 kg ai/ha gave residues 21 days after the last treatment between 0.08 and 0.23 mg/kg. Residues in 5 Italian trials with 1-3 treatments of 0.18-0.27 kg ai/ha were 0.05-2.1 mg/kg at 28 days. Generally the application rates in the trials were much higher than the rates close to 0.1 kg ai/ha permitted by GAP, or the PHI was excessive.
The Meeting concluded that since no data were provided from trials according to GAP it could not estimate a maximum residue level for teflubenzuron in grapes.
Uses on other berries are not registered but eight German trials on wild raspberries, blackberries and blueberries were reported. In Germany, teflubenzuron is registered for use in the forest against larvae of Tenthredinidae spp. and free-eating caterpillars (1 x 0.023 kg ai/ha). As result of this, wild berries and fruits are treated unintentionally. The worst case was simulated by application of approximately twice the approved rate (0.045 kg ai/ha). In raspberries and blackberries, the residues were <0.05 (2), 0.06 (2) and 0.09 mg/kg, <0.05 (4) and 0.08 mg/kg, and <0.05 (4) and 0.05 mg/kg at 0, 2 or 3, and 7 days respectively. The residues in blueberries in three trials, which appeared to be from a different population, were 0.08, 0.09 and 0.1 mg/kg, 0.11 (2) and 0.12 mg/kg, and 0.05, 0.06 and 0.07 mg/kg at 0, 2 and 7 days.
The Meeting accepted that there was an indirect use on wild berries, but because the data were limited and the commodities are not in international trade it did not estimate maximum residue levels for teflubenzuron on wild raspberries, blackberries or blueberries.
Persimmons. Data were available from a group of 5 trials in Korea. Persimmons were treated 2-6 times with 0.25 kg ai/ha. Residues in samples taken 3-45 days after the last treatment were 0.02-0.09 mg/kg. No GAP was available to evaluate the trials.
Kiwifruit. Four residue trials were carried out in New Zealand. The application rates were 0.094, 0.19 and 0.25 kg ai/ha. Residues determined in whole fruit 16 and 99 days after the final application were 0.23-3.6 mg/kg and 0.28 mg/kg respectively. No GAP was available to evaluate the trials.
Head cabbages. There are registered uses on red, white and Savoy cabbage in Germany (1 x 0.06 kg ai/ha, 14-day PHI), on red and white cabbage in The Netherlands (2-4 x 0.06 kg ai/ha, 14-day PHI), and on head cabbages in Indonesia (0.025 kg ai/ha, no further information), Italy (1 x 0.03 kg ai/ha, 7-day PHI), Jordan (2 x 0.0075 kg ai/hl, 14-day PHI), Poland (1 x 0.03 kg ai/ha, 14-day PHI) and Switzerland (1 x 0.045 kg ai/ha, 14-day PHI).
Four US trials on white and red cabbage, each with analyses of duplicate samples with and without wrapper leaves, were reported. Residues after applying 6 x 0.045 kg ai/ha were <0.05-0.36 mg/kg in samples with wrapper leaves and <0.05-0.11 mg/kg without wrapper leaves 14 days after treatment. One trial was carried out in Malaysia and one in the Philippines. After applying 6 or 9 x 0.045 kg ai/ha, residues were <0.05 mg/kg after 18 and 7 days respectively. In two trials in Brazil (1 x 0.015 kg ai/ha, 1 x 0.03 kg ai/ha) residues were <0.01 mg/kg 3 or 7 days after treatment. No information on GAP was available for the USA, Brazil, Malaysia or the Philippines with which to evaluate the data from the trials in these countries.
Ten trials on Savoy cabbage were conducted in Germany, 1982-1985. After applying 3 x 0.06 kg ai/ha, all residues were <0.05 mg/kg at the recommended PHI of 14 days. Residues in two UK trials on Savoy cabbage treated once according to German GAP with 0.06 kg ai/ha were 0.05 and 0.17 mg/kg at 14 days.
The Meeting estimated a maximum residue level of 0.2 mg/kg for teflubenzuron in head cabbages.
The teflubenzuron residues in the ten German and two UK trials in rank order were <0.05 (10), 0.05 and 0.17 mg/kg. The median residue was below the LOD (0.05 mg/kg). The Meeting estimated an STMR level of 0.05 mg/kg.
Broccoli. Teflubenzuron is registered for use on broccoli in The Netherlands with 2-4 treatments of 0.06 kg ai/ha and a PHI of 14 days.
Two German trials according to Dutch GAP were reported. The residues were 0.13 and 0.19 mg/kg at day 14.
The Meeting concluded that insufficient data were available to estimate a maximum residue level for teflubenzuron in broccoli.
Brussels sprouts. Teflubenzuron is registered in The Netherlands, where 6-8 treatments of 0.09 kg ai/ha with a PHI of 14 days are recommended.
Eight residue trials were conducted in The Netherlands with 4, 5 or 6 applications, four at 0.06 and four at 0.09 kg ai/ha. After treatment with 0.09 kg ai/ha, the residues were 0.12 to 0.48 mg/kg at 14 days. The residues after 14 days in the 4 trials with 0.06 kg ai/ha were of the same order, 0.1-0.28 mg/kg, and support the conclusion that a maximum residue level of 0.5 mg/kg is appropriate. The residues in rank order were 0.1, 0.12, 0.15, 0.18. 0.24, 0.28, 0.39 and 0.48 mg/kg, giving a median of 0.21 mg/kg.
The Meeting estimated an STMR level of 0.21 mg/kg and a maximum residue level of 0.5 mg/kg for Brussels sprouts.
Cucumbers. Teflubenzuron is registered for field and glasshouse uses on cucurbits in Spain (2-3 x 0.18 kg ai/ha, 3-day PHI), for glasshouse use on cucumbers and gherkins in The Netherlands (3-5 x 0.23 kg ai/ha, 3-day PHI), for field treatments of cucumbers and gherkins (2 x 0.0075 kg ai/hl, 3-day PHI) in Jordan, and for field use on cucumbers with 2 x 0.011 kg ai/hl in Saudi Arabia.
Three indoor trials were carried out in Germany. The residues after 3 days were 0.03 and 0.07 mg/kg from approximately 3 x 0.09 kg ai/ha, and 0.14 mg/kg from 3 x 0.18 kg. In two field trials in Italy, where 3 x 0.075 kg ai/ha were applied, the residues after 3 days were 0.02 and 0.19 mg/kg.
The Meeting concluded that there were insufficient data from trials according to GAP to estimate a maximum residue level for teflubenzuron in cucumbers.
Peppers. Teflubenzuron is registered for field use on sweet peppers in Italy (1-2 x 0.08 kg ai/ha, 10-day PHI), Jordan (2 x 0.0075 kg ai/hl), Saudi Arabia (2 x 0.011 kg ai/hl) and Spain (2-3 x 0.18 kg ai/hl, 3-day PHI), and on chilli peppers in Indonesia at 0.1 kg ai/ha. Glasshouse use on sweet peppers is registered in The Netherlands with 3-5 applications and in Spain with 2 or 3 applications of 0.23 kg ai/ha and a PHI of 3 days.
The Meeting reviewed 6 trials from Italy, 4 of them (all in 1988) according to Italian GAP with 1 treatment of 0.075 kg ai/ha. The residues were 0.09, 0.1. and 0.11 mg/kg (2) 10 days after application.
Trials were reported from Korea but no information on GAP was available for their evaluation.
The Meeting concluded that only 4 trials according to GAP, carried out in one year, were insufficient to estimate a maximum residue level for peppers, which are a major crop.
Egg plants. Teflubenzuron is registered for field use on egg plants in Italy with 1-2 x 0.022-0.024 kg ai/ha, 10-day PHI. The GAP for field use in Jordan, Saudi Arabia and Spain, and for glasshouse use in The Netherlands and Spain, is the same as for sweet peppers.
The Meeting reviewed 6 outdoor trials from Italy. In four of them which complied with Italian GAP with 1 treatment at 0.023 kg ai/ha the residues were all <0.01 mg/kg 10 days after application. No residue data were available for glasshouse use.
The Meeting concluded that the data were insufficient to estimate a maximum residue level.
Tomatoes. Teflubenzuron is currently registered for glasshouse use in The Netherlands (3-5 x 0.23 kg ai/ha, 3-day PHI), and for glasshouse and field use in Spain (2-3 x 0.18-0.23 kg ai/ha, 3-day PHI). In Brazil and Paraguay, 5-8 field treatments at 0.038 kg ai/ha with a PHI of 7 days are recommended. Further registered field uses exist in Argentina, Colombia, Ecuador, and Jordan.
Four trials were carried out in the USA. Residues from <0.05 to 0.1 mg/kg were found 3 days after treatment with 5 x 0.028-0.056 kg ai/ha. No information on GAP was available for the USA with which to evaluate the data.
Two of 6 field trials in Brazil, with 5 x 0.045 kg ai/ha, approximated GAP and resulted in residues of 0.05 and 0.06 mg/kg 6 days after treatment, two trials at twice this rate gave residues of 0.08 and 0.15 mg/kg, and in the third pair of trials (3 x 0.03 kg ai/ha) 0.1 and 0.12 mg/kg were found at 7 days. Two Italian field trials at 4 x 0.075 kg ai/ha, with residues of 0.1 and 0.28 mg/kg at day 2, could not be evaluated against Spanish GAP because the rate was too low.
Three indoor trials with 3 or 4 treatments at 0.09-0.17 kg ai/ha were reported from Germany, but there are no registered uses there. One of them could be evaluated against Dutch GAP and showed a residue of 0.47 mg/kg 3 days after application. Two of three UK trials at 4 x 0.17 kg ai/ha, 5 x 1.14-1.17 kg ai/ha, and 5 x 0.23 kg ai/ha approximated Dutch and Spanish glasshouse uses and showed residues of 0.2 and 0.36 mg/kg 3 days after treatment.
The Meeting concluded that there were insufficient data from trials according to GAP for field and glasshouse uses to estimate a maximum residue level for teflubenzuron in tomatoes.
Mushrooms. Uses on cultivated mushrooms exist in Belgium (3 kg ai/ha, 14-day PHI) and Italy (1 x 4.8-6 kg ai/ha, 45-day PHI).
One trial with four replicated plots of cultivated mushrooms was conducted in The Netherlands. The residues were all <0.05 mg/kg 25 days after applying 2 x 4.9 kg ai/ha.
The Meeting concluded that the data from trials according to GAP were insufficient to estimate a maximum residue level for teflubenzuron in cultivated mushrooms.
In 3 trials on wild mushrooms in Germany with 1 x 0.045 kg ai/ha the residues on days 0, 1 and 2 were all <0.05 mg/kg in two trials and 0.07, 0.07 and 0.05 mg/kg respectively in the third.
The Meeting accepted that there was an indirect use on wild mushrooms from the German use of teflubenzuron in forests (1 x 0.023 kg ai/ha), but because the data were limited and wild mushrooms are not in international trade it did not estimate a maximum residue level for wild mushrooms.
Chinese cabbage. Teflubenzuron is currently registered only in The Netherlands. It is recommended for field use at a rate of 0.06 kg ai/ha 2-4 times a season with a PHI of 14 days.
Two trials were carried out in the Netherlands. After applying 1 x 0.06 or 0.09 kg ai/ha the residues were 0.22 and 0.31 mg/kg at day 14.
Trials were also conducted in Malaysia and the Philippines but no information on GAP for Asian countries was available from which to evaluate the results.
The Meeting concluded that there were insufficient data from trials according to GAP to estimate a maximum residue level.
Peas. One trial with 2 x 0.045 kg ai/hl was conducted in France. The residues were 0.19 mg/kg in peas with pods and <0.05 mg/kg in the peas after 21 days. No information on GAP was available to evaluate the trial.
Soya beans. Teflubenzuron is registered for the use on soya beans in Brazil (0.0075-0.023 kg ai/ha) and Paraguay (2-3 x 0.0075 kg ai/ha) with PHIs of 30 days.
Six trials were carried out in Brazil (1-2 x 0.015-0.09 kg ai/ha). Four of them (2 x 0.015-0.03 kg ai/ha) were within the wide range of Brazilian GAP but were at only 2 sites. The residues were <0.01 mg/kg 30 days after treatment.
One study with replicated trials at various application rates was carried out in the USA. Residues in the seeds after 2 treatments with 0.034 kg ai/ha (0.015 kg ai/hl) and a PHI of 30 days were <0.05-0.34 mg/kg. No information on relevant GAP was available.
The Meeting concluded that the data from trials according to GAP were insufficient to estimate a maximum residue level for teflubenzuron in soya beans, a major crop.
Potatoes. Teflubenzuron is registered for use on potatoes in Germany (1 x 0.045 kg ai/ha), Italy (1-2 x 0.024 kg ai/ha), Poland (1-2 x 0.038 kg ai/ha), Saudi Arabia (2 x 0.011 kg ai/hl), Spain (1-2 x 0.022 kg ai/ha) and Switzerland (0.038 kg ai/ha). The PHIs range from 14 to 28 days.
Data were available from 11 trials in Brazil, France, Germany, Italy, Slovakia and the USA, but most of them were not according to GAP or no information on relevant GAP was available. Only 2 German trials (2 x 0.052 kg ai/ha, 14-day PHI) approximated GAP. Teflubenzuron was not detected in any of the samples (<0.05 mg/kg), even from exaggerated application rates at short PHIs.
It was concluded from a study of teflubenzuron metabolism and kinetics in potato plants that teflubenzuron does not penetrate into the leaves, stems or tubers if it is sprayed on the foliage. No systemic transport or metabolism occurs in the plants.
In view of the results of the metabolism study and the absence of residues in the trials, the Meeting concluded that sufficient information was available to estimate a maximum residue level for potatoes of 0.05* mg/kg as being a practical limit of determination, and estimated an STMR level of nil for teflubenzuron in potatoes.
Maize. Uses of teflubenzuron exist in Colombia and Ecuador with 2 treatments of 0.045 kg ai/ha and in Ecuador a PHI of 21 days. The insecticide is registered in Italy for use on maize at 2 x 0.15-0.16 kg ai/ha with a PHI of 28 days, and in Switzerland for cereals at 0.06 kg ai/ha with a 42-day PHI.
Supervised trials were reported from France (6), Germany (10), Italy (2) and Slovakia (3), but information on GAP was available only from Italy. None of the northern European trials approximated Swiss GAP nor the French trials Italian GAP (they were at exaggerated rates and/or longer PHIs). Two trials in Italy with 2 x 0.15 kg ai/ha corresponded with GAP. At day 28 the residues were 3.6 and 3.9 mg/kg in the whole plant and <0.05 mg/kg in the grain.
The data from trials according to GAP were insufficient to estimate a maximum residue level.
Cotton seed. Teflubenzuron is registered for uses on cotton in Argentina (2 x 0.011 kg ai/ha, 21-day PHI), Brazil (0.0075-0.1 kg ai/ha, 30-day PHI), Paraguay (2-3 x 0.0075 kg ai/ha, 30-day PHI), Colombia (2 x 0.019 kg ai/ha), Ecuador (2 x 0.019-0.045 kg ai/ha) and Guatemala (2-3 x 0.075 kg ai/ha).
Seven trials in Latin America were within the wide range of Brazilian GAP. No residues above the LODs of 0.01 or 0.05 mg/kg were found in 4 Brazilian trials (2 x 0.03 or 2 x 0.06 kg ai/ha, PHI 31 days), 2 trials in Guatemala (14-15 x 0.039 kg ai/ha, PHI 6-8 days), or 1 trial in Mexico (12 x 0.06-0.08 kg ai/ha, PHI 18 days). The residues in rank order were 0.01 (4), 0.05 mg/kg (3).
In 9 US trials the residues were 0.05, 0.07, 0.08, 0.11, 0.24 and 13 mg/kg from 12 x 0.045 kg ai/ha, and 0.78, 3.1 and 4.6 mg/kg from 12 x 0.45 kg ai/ha 14 or 18 days after treatment. No information on GAP was available to evaluate the trials.
The results of the 6 US trials with 12 treatments at 0.045 kg ai/ha are inconsistent with the "nil" residues in Latin America with similar application rates. For this reason and because Brazilian GAP is reported to have such a wide range of application rates, the Meeting could not estimate a maximum residue level for cotton seed.
Coffee beans. The registered uses of teflubenzuron on coffee plants are in Brazil at 0.038 kg ai/ha and in Kenya with 1 or 2 treatments at 0.11 kg ai/ha, with PHIs of 30 days in both countries.
Two residue trials were conducted in Brazil. After 2 applications of 0.075 or 0.15 kg ai/ha and a PHI of 35 days, the residues were 0.6 and 1.7 mg/kg respectively.
There were insufficient data to estimate a maximum residue level.
Alfalfa forage and green grass. Two supervised trials on alfalfa and 1 on green grass were carried out in Italy (1 x 0.075 kg ai/ha). The residues in alfalfa forage declined from 1.4 and 2 mg/kg at day 3 to 0.18 and 1.2 mg/kg at day 28 after application. The residue is grass was 0.71 mg/kg at 28 days. No information on GAP was available to evaluate the trials.
Soya bean forage and hay. Teflubenzuron is registered for use on soya beans in Brazil (0.0075-0.023 kg ai/ha) and Paraguay (2-3 x 0.0075 kg ai/ha) with PHIs of 30 days.
Eight trials were carried out in the USA with 1 or 2 x 0.022 kg ai/ha. The residues in the forage and hay were 0.17-0.56 mg/kg and 0.19-1.3 mg/kg, respectively, at day 14. No information on GAP was available to evaluate the results.
Because no residue data were submitted from South America, the Meeting could not estimate a maximum residue level for teflubenzuron in soya bean forage or hay.
Animal products. When dairy cows were fed with feed containing 10, 30 or 100 ppm teflubenzuron for 28 days, the residues of teflubenzuron in subcutaneous fat, peritoneal fat, liver, kidney and skeletal muscle were 0.05 mg/kg. Low concentrations of teflubenzuron were detected in the liver or kidney of some animals (0.015-0.041 mg/kg). There was no indication of any correlation with the dose level, or with the withdrawal period in the high-dose group. Two apparent residues were found in the control group. Residues of the metabolite E-115, 1-(3,5-dichloro-2,4-difluorophenyl)-3-(2,6-difluoro-3-hydroxybenzoyl)urea, in liver samples were 0.05 mg/kg (the LOD).
Only low residues of teflubenzuron occurred in peritoneal fat (0.011-0.028 mg/kg). Residues at or close to the LOD (0.01 mg/kg) were recorded in subcutaneous fat in the high-dose group, but 0.016 mg/kg was found 14 days after withdrawal.
No residues were found in any muscle or milk samples (<0.01 mg/kg).
An obstacle to estimating maximum residues for meat and milk is the lack of sufficient residue data on typical feed items (green forage, fruit pomace, cereal grains, pulses, oil seed), for which no MRLs could be recommended. The Meeting concluded that in the absence of such recommendations no maximum residues for teflubenzuron in products of ruminant origin could be estimated.
Laying hens were fed teflubenzuron at levels of 0.5 ppm, 1.5 ppm and 5 ppm in the diet for 28 days. Residues were detected in the eggs of all treated groups and a dose-related trend was observed. Values above the LOD of 0.01 mg/kg were first measured at day 14 in the groups treated with 0.5 ppm (0.04 mg/kg) and 1.5 ppm (0.06 mg/kg). In the high-dose group the first measured mean residue was 0.03 mg/kg at day 3, a mean maximum of 0.30 mg/kg was reached at day 26 and the residues declined during the withdrawal period. They were below the LOD after 42 days in the highest dose group.
Residues of teflubenzuron were found in all types of tissue analysed. The highest concentrations occurred in abdominal fat (0.7 mg/kg in the highest dose group). In the 0.5 ppm group residues were <0.01 mg/kg in muscle and 0.028 mg/kg in subcutaneous fat. Residues in the liver of hens kept on a teflubenzuron-free diet after dosing persisted for 7 or 14 days after withdrawal. Residues of the metabolite E-115 in liver samples were below the LOD (0.05 mg/kg). High positive results were found in the livers of control birds.
Again the lack of residue data on typical poultry feed items (cereals, pulses) prevented the Meeting from estimating maximum residue levels for teflubenzuron in poultry commodities.
Processing studies on apples, plums, cherries, grapes, potatoes, tomatoes, soya beans and cotton were made available to the Meeting. With most of these crops (apples, plums, tomatoes, potatoes, soya beans, cotton seed) even exaggerated application rates did not produce sufficiently high residues in the raw commodity to estimate transfer factors. The Meeting was also unable to confirm the reported results for the processed products in the absence of details of the processing procedures.
In general, residues were reduced in canning fruit and processing to juice and wine but concentrated during soya bean oil production, by drying fruits, and in producing pomace. This is to be expected because of the fat-soluble nature of the active ingredient or the reduced water content of the processed products.
The only information on residues in the edible portions of food commodities came from separate analyses of the pulp and peel of citrus fruit. Although the data were insufficient to estimate a maximum residue level for citrus, they indicated that residues in citrus pulp are likely to be less than 10% of the residue in the peel.
No information was provided on residues in commodities in commerce or at consumption.
