Trials were carried out in Australia, Canada, Europe, Japan, New Zealand, the USA, and other countries. All trials in Germany and the USA were conducted according to Good Laboratory Practice (GLP). Some trials were designed to determine efficacious use rates and the effects of the timing of applications as well to assess the residues in the crop at various pre-harvest intervals. The field parts of these trials were not conducted according to GLP.
The results were not corrected for analytical recoveries unless noted. Analytical recoveries were mostly high (>80%), so using uncorrected or corrected results should not significantly influence the interpretations.
Pome Fruits
Apples. Eight trials were conducted from November 1992 to March 1993 in Australia (Rouch, 1994) as a randomized block of four duplicates. Four different application rates were used and eight applications were made at 2-week intervals. The spray concentration used were 1.6-6.4 times the proposed GAP rate. The residue values in Table 21 are the averages of samples from duplicate plots.
Six small-plot field trials (one tree per plot) were conducted from November 1994 to March 1995 in apples following season-long applications of tebufenozide 70WP and 200 SC in Australia (Armstrong, 1995b) as a randomized block of three replicates. Treatments commenced just at petal fall and continued every two weeks until commercial harvest. A motorized hand sprayer was used. The spray concentrations were 0.012 kg ai/hl and 0.024 kg ai/hl. All above-ground parts of each tree were sprayed to near the point of run-off each time. Fruit samples were collected at various PHIs.
These trials were at higher rates than the proposed GAP (4-8 applications at 0.18 kg ai/ha, 0.006 kg ai/hl, 28 days PHI). The average residue was 1.3 mg/kg on day 28.
A number of trials were conducted in Canada. In 1993 (Bruns, 1994) three to five applications were made either to three trees per plot or to single tree plots replicated three times in a randomized complete block design. The trees were sprayed to the point of runoff using a handgun. In six trials according to GAP in 1995 (Bruns, 1995) four applications were made at 0.24 kg ai/ha each and the spray intervals ranged from 2 weeks to 3 months. Samples were analysed by a modified HPLC method (Bruns, 1994). The limit of determination was 0.02 mg/kg and the average recovery 77%.
In other apple trials in Canada in 1994 (Tillman, 1995a) plots consisted of either four trees or single tree plots replicated three times in a randomized block. The trees were sprayed to runoff with a handgun. Samples were analysed by HPLC according to GLP.
Residues of tebufenozide in the trials according to Canadian GAP ranged from 0.06 to 1.1 mg/kg.
A series of efficacy trials was carried out in Chile to assess the bioactivity of tebufenozide in controlling the major pome fruit pest, codling moth (Gonzalez, 1995). In one trial samples were analysed for tebufenozide to establish the dissipation rate.
In a series of field trials with several different apple varieties in geographically representative apple orchards in France (Tillman, 1994) five to seven applications were usually made at intervals of about 2 weeks. The analyses were according to GLP but the field parts of the trials were not. In the four trials according to GAP the average residue was 0.1 mg/kg (PHI 18-21 days).
In GLP trials in Germany in 1992 in Germany according to proposed GAP (Raquet et al., 1993) three applications at 0.122-0.202 kg ai/ha (0.013 kg ai/hl) were made with a motorized knapsack sprayer. The apples were analysed by a validated method (Schuld and Holzworth, 1994a).
In three other GLP trials in Germany in 1993 (Brusche and Holzwarth, 1995) tebufenozide was applied three times at the maximum proposed rate using a knapsack mist blower to 7-14 trees per plot.
The residues in whole fruit in the German trials according to proposed GAP ranged from 0.02 to 0.35 mg/kg.
A single trial in 1993 in Greece (AgrEvo, 1995) was not according to actual or proposed GAP. Eight applications were made to a single tree at 2-week intervals. The residues in treated samples were 0.4-0.66 mg/kg and in control samples 0.02 mg/kg.
Three of six trials (Tillman, 1994) in Italy in 1992 complied with GAP. Three applications were made at intervals of about 30 days to 6 trees per plot. Apple samples were analysed by GLC with an NPD. Residues in the trials according to GAP ranged from 0.28 to 0.55 mg/kg.
Two trials were conducted in Japan according to GAP: 2 applications, 10 days apart, at 0.400 kg ai/ha (Komatsu and Yabusaki, 1994). The dates of the applications were varied in order to harvest the mature samples with different PHIs. Samples were analysed for the parent compound, RH-1788 and RH-6595. RH-6595 was reduced to RH-1788 and both it and tebufenozide were methylated and analysed by GLC (Schuld and Holzwarth, 1994a). The residues of tebufenozide were 0.02 and 0.05 mg/kg. Residues of RH-1788 and RH-6595 were all below the LOD of 0.01 mg/kg.
Six residue trials during the 1992/1993 growing season with Gala apples (Tillman, 1995c) and ten during the 1994/95 growing season (Tillman, 1995b) in New Zealand were designed to assess the residues on apples from different use rates at different frequencies and timings. Applications were made by applying tebufenozide 70W to run-off with a hand-held lance. The application rates changed after the first three applications owing to the higher spray volumes. Typical volumes are 2500 to 3000 l/ha, increasing as the foliage becomes denser toward harvest.
The trials were with single trees with five replicates. All apple samples were analysed by HPLC (Deakyne et al., 1994b). The LOD of the method was 0.03 mg/kg and recoveries ranged from 68 to 85% in 1992/1993 and from 77 to 120% in 1994/1995.
Two trials were conducted in Spain according to proposed GAP (Tillman, 1994). Two trees in each plot were sprayed three times with an atomizer spray. The samples were analysed in France by the method of Mellet (1993a). The residues were 0.37 and 0.54 mg/kg.
A series of field trials on apples in a number of States of the USA from 1991 to 1993 (Burnett et al., 1994) were under GLP but not according to proposed GAP. Most trials were with 9 applications of 0.336 kg ai/ha and a few with 10 applications of 0.280 kg ai/ha. The plot sizes ranged from 0.54 to 6.19 ha with a minimum of 4 and a maximum of 37 trees in a plot. Samples were analysed by HPLC. The number of applications was greater than that recommended in the proposed GAP.
Four trials according to the proposed GAP (6 applications at 0.336 kg ai/ha) in 1994 at two locations in the USA (Dong, 1995d) were designed to compare the 2SC and 70WP formulations. The plot sizes ranged from 2.56 to 2.79 ha. Samples were analysed by HPLC. Residues from proposed GAP ranged from 0.36 to 0.6 mg/kg. The residues from the two formulations were similar.
