In processing
Residues and application rates have generally been rounded to 2 significant figures or, for residues near the LOD, to 1 significant figure. Residues were not detected in control samples except for an occasional value at the LOD.
Wheat grain was treated with two formulations (EC and UL) of a bifenthrin + malathion mixture at a nominal application rate of 0.30 g ai/t for bifenthrin and 6.0 g ai/t for malathion. The grain was treated in 25 kg batches (2 batches treated and combined for each formulation) by applying the pesticides with a hand pump sprayer to the grain tumbling in a small concrete mixer with clean shiny, bare steel interior surfaces.
The treated grain and controls were delivered to Weston Research Laboratories for storage and milling (Creighton and Charlton, 1995). The grain was kept in open-topped bins at a room temperature of 20°C. The grain moisture was 13.2% throughout the duration of the storage. Samples (1 or 4 kg) were withdrawn periodically for cleaning and milling. The 4 kg samples were milled when the flour was destined for bread production.
The grain was cleaned before milling with a Laboratory Carter Day Dockage Tester, which simulates commercial cleaning. Screenings removed from the grain amounted to 0.7-1.5%. The grain was conditioned to 15.7% moisture and milled on a Buhler Mill to produce flour and bran. The white flour extraction rate was 81-82%. Wholemeal was made by recombining bran and white flour. Bread was produced in 400 g loaves by the Chorleywood Breadmaking Process. Uncleaned grain, flour, bran and bread were sent to Gembloux for residue analysis (Roland et al., 1995b). The residues found in wheat are shown in Table 1, and those in flour, bran and bread in Tables 2-5.
In another storage trial wheat was treated with UL or EC formulations of bifenthrin + malathion and stored at 20°C and 25°C at a relative humidity of 65% for 6 months (Roland et al., 1995a). Samples were withdrawn for analysis 0, 90 and 180 days after treatment. The residues are shown in Table 1.
Concentration factors for residues of bifenthrin in milling and baking fractions from wheat are given in Table 6. The factors are calculated from the bifenthrin residues in Tables 2 and 3. Approximately 16% of the residues were lost in producing wholemeal flour from uncleaned wheat. The bifenthrin level in white flour was about 30%, and the level in bran 3.5 times that in uncleaned wheat.
The results of these trials suggest that about 70% of the bifenthrin disappears on baking wholemeal or white bread.
Table 1. Residues of bifenthrin and malathion resulting from supervised trials on stored wheat after post-harvest applications (Roland et al., 1995 a, b).
|
Country, year |
Grain weight, temp |
Form |
Treatment g ai/t |
Storage time |
Residues, mg/kg |
Ref. |
|
|
Bifenthrin |
Malathion |
||||||
|
UK, 1995 |
50 kg, 20°C |
UL |
b 0.3 + m 6.0 |
1 day |
0.24 |
4.1 |
CRP/95/1363 |
|
4 weeks |
0.24 |
2.6 |
|||||
|
8 weeks |
0.23 |
2.4 |
|||||
|
12 weeks |
0.22 |
1.4 |
|||||
|
UK, 1995 |
50 kg, 20°C |
EC |
b 0.3 + m 6.0 |
1 day |
0.25 |
4.0 |
CRP/95/1363 |
|
4 weeks |
0.24 |
2.8 |
|||||
|
8 weeks |
0.25 |
2.3 |
|||||
|
12 weeks |
0.24 |
2.0 |
|||||
|
France, 1995 |
100 kg, 20°C |
UL |
b 0.3 + m 6.0 |
day 0 |
0.26 |
4.5 |
CRP/95/1362 |
|
day 90 |
0.25 |
2.6 |
|||||
|
day 180 |
0.21 |
0.68 |
|||||
|
France, 1995 |
100 kg, 25°C |
UL |
b 0.3 + m 6.0 |
day 0 |
0.28 |
4.5 |
CRP/95/1362 |
|
day 90 |
0.24 |
2.4 |
|||||
|
day 180 |
0.22 |
0.98 |
|||||
|
France, 1995 |
100 kg, 20°C |
EC |
b 0.3 + m 6.0 |
day 0 |
0.31 |
5.0 |
CRP/95/1362 |
|
day 90 |
0.27 |
2.2 |
|||||
|
day 180 |
0.25 |
0.92 |
|||||
|
France, 1995 |
100 kg, 25°C |
EC |
b 0.3 + m 6.0 |
day 0 |
0.32 |
5.3 |
CRP/95/1362 |
|
day 90 |
0.28 |
2.4 |
|||||
|
day 180 |
0.24 |
0.90 |
|||||
b: bifenthrin m: malathion
Table 2. Bifenthrin residues in wheat and processed commodities from wheat treated post-harvest with a UL formulation at bifenthrin 0.3 g ai/t and malathion 6 g ai/t and stored for 12 weeks at 20°C. Samples were withdrawn on day 1 and weeks 4, 8 and 12 for milling (Roland et al., 1995b).
|
Sample |
Bifenthrin residues, mg/kg |
|||||||
|
Day 1 |
Week 4 |
Week 8 |
Week 12 |
|||||
|
fresh wt |
dry wt |
fresh wt |
dry wt |
fresh wt |
dry wt |
fresh wt |
dry wt |
|
|
Wheat |
0.24 |
0.27 |
0.24 |
0.27 |
0.23 |
0.26 |
0.22 |
0.24 |
|
Wholemeal flour |
0.20 |
0.23 |
0.19 |
0.22 |
0.21 |
0.24 |
0.17 |
0.19 |
|
Wholemeal bread |
0.05 |
0.08 |
|
|
0.04 |
0.07 |
|
|
|
White flour |
0.07 |
0.08 |
|
|
0.06 |
0,07 |
|
|
|
White bread |
0.02 |
0.03 |
|
|
0.01 |
0.02 |
|
|
|
Bran |
0.75 |
0.85 |
|
|
0.88 |
1.0 |
|
|
Table 3. Bifenthrin residues in wheat and processed commodities from wheat treated post-harvest with an EC formulation at bifenthrin 0.3 g ai/t and malathion 6 g ai/t and stored for 12 weeks at 20°C. Samples were withdrawn on day 1 and weeks 4, 8 and 12 for milling (Roland et al., 1995b).
|
Sample |
Bifenthrin residues, mg/kg |
|||||||
|
Day 1 |
Week 4 |
Week 8 |
Week 12 |
|||||
|
fresh wt |
dry wt |
fresh wt |
dry wt |
fresh wt |
dry wt |
fresh wt |
dry wt |
|
|
Wheat |
0.25 |
0.28 |
0.24 |
0.28 |
0.25 |
0.28 |
0.24 |
0.27 |
|
Wholemeal flour |
0.20 |
0.23 |
0.18 |
0.20 |
0.22 |
0.25 |
0.22 |
0.25 |
|
Wholemeal bread |
0.03 |
0.05 |
|
|
0.05 |
0.08 |
|
|
|
White flour |
0.09 |
0.10 |
|
|
0.07 |
0.08 |
|
|
|
White bread |
0.02 |
0.03 |
|
|
0.02 |
0.03 |
|
|
|
Bran |
0.83 |
0.95 |
|
|
0.92 |
1.1 |
|
|
Table 4. Malathion residues in wheat and processed commodities from wheat treated post-harvest with a UL formulation at bifenthrin 0.3 g ai/t and malathion 6 g ai/t and stored for 12 weeks at 20°C. Samples were withdrawn on day 1 and weeks 4, 8 and 12 for milling (Roland et al., 1995b).
|
Sample |
Malathion residues, mg/kg |
|||||||
|
Day 1 |
Week 4 |
Week 8 |
Week 12 |
|||||
|
fresh wt |
dry wt |
fresh wt |
dry wt |
fresh wt |
dry wt |
fresh wt |
dry wt |
|
|
Wheat |
4.1 |
4.7 |
2.6 |
2.9 |
2.4 |
2.7 |
1.4 |
1.6 |
|
Wholemeal flour |
2.0 |
2.3 |
1.4 |
1.7 |
1.5 |
1.8 |
1.5 |
1.7 |
|
Wholemeal bread |
0.53 |
0.88 |
|
|
0.25 |
0.42 |
|
|
|
White flour |
0.74 |
0.85 |
|
|
0.55 |
0.64 |
|
|
|
White bread |
0.11 |
0.18 |
|
|
0.08 |
0.12 |
|
|
|
Bran |
3.5 |
4.0 |
|
|
6.6 |
7.5 |
|
|
Table 5. Malathion residues in wheat and processed commodities from wheat treated post-harvest with an EC formulation at bifenthrin 0.3 g ai/t and malathion 6 g ai/t and stored for 12 weeks at 20°C. Samples were withdrawn on day 1 and weeks 4, 8 and 12 for milling (Roland et al., 1995b).
|
Sample |
Malathion residues, mg/kg |
|||||||
|
Day 1 |
Week 4 |
Week 8 |
Week 12 |
|||||
|
fresh wt |
dry wt |
fresh wt |
dry wt |
fresh wt |
dry wt |
fresh wt |
dry wt |
|
|
Wheat |
4.0 |
4.6 |
2.8 |
3.2 |
2.3 |
2.7 |
2.0 |
2.2 |
|
Wholemeal flour |
2.6 |
3.0 |
1.6 |
1.8 |
1.5 |
1.8 |
1.8 |
2.0 |
|
Wholemeal bread |
0.30 |
0.44 |
|
|
0.27 |
0.45 |
|
|
|
White flour |
0.91 |
1.0 |
|
|
0.48 |
0.56 |
|
|
|
White bread |
0.16 |
0.26 |
|
|
0.07 |
0.11 |
|
|
|
Bran |
4.4 |
5.1 |
|
|
4.8 |
5.5 |
|
|
Table 6. Mean processing factors for bifenthrin residues on wheat, wholemeal, flour and bread calculated from data in Tables 2 and 3 (Roland et al., 1995b).
|
Process |
Bifenthrin residues in second commodity - bifenthrin residues in first commodity, mean (range) |
|
|
Both commodities fresh weight basis |
Both commodities dry weight basis |
|
|
Uncleaned wheat ® wholemeal flour |
0.83 (0.75-0.92) |
0.84 (0.71-0.93) |
|
Uncleaned wheat ® white flour |
0.30 (0.26-0.36) |
0.30 (0.27-0.36) |
|
Uncleaned wheat ® bran |
3.5 (3.1-3.8) |
3.5 (3.1-3.8) |
|
Wholemeal flour ® wholemeal bread |
0.20 (0.15-0.25) |
0.30 (0.22-0.35) |
|
White flour ® white bread |
0.24 (0.17-0.29) |
0.33 (0.29-0.38) |
