Because haloxyfop is often applied to soil the 1995 Meeting concluded that information was needed on the uptake by crops of haloxyfop and its degradation products from soil. Appropriate studies were reported to the present Meeting.
An emulsifiable formulation of [phenyl-U-14C]haloxyfop-butyl was applied to bare soil at a rate equivalent to 0.56 kg ai/ha (Yackovich and Miller, 1983c). Thirty days later the plot was tilled and planted with spring wheat, soya beans, carrots, turnips and lettuce. The crops were grown to maturity and the uptake of 14C determined by combustion and LSC. The highest residue, 0.07 mg/kg haloxyfop equivalent, was found in immature soya bean foliage sampled 56 days after planting. Residues in the edible portions of the crops were <0.01 mg/kg haloxyfop equivalent. Owing to the low levels of radioactivity, attempts to isolate and identify the residues were unsuccessful. The results are given in Table 3.
Table 3. Uptake of 14C by crops planted 30 days after treatment of soil with [14C]haloxyfop at 0.56 kg ai/ha.
|
Sample |
Days from planting to harvest |
14C as mg/kg haloxyfop equivalent |
|
Lettuce |
49 |
0.01 |
|
Turnip foliage |
64 |
<0.01 |
|
Turnip root |
64 |
<0.01 |
|
Wheat grain |
110 |
0.01 |
|
Wheat straw |
110 |
0.02 |
|
Soya bean |
113 |
<0.01 |
|
Soya bean forage |
56 |
0.07 |
|
Soya bean straw |
113 |
0.01 |
|
Carrot forage |
115 |
<0.01 |
|
Carrot root |
115 |
<0.01 |
An EC formulation of [phenyl-U-14C]haloxyfop-butyl was applied to a crop of 37.5 cm soya bean plants at a rate equivalent to 0.56 kg ai/ha (Yackovich and Miller, 1983d). After harvesting the crop 130 days after treatment, the top 5 cm of soil was removed, brought into the laboratory, and sown with spring wheat, soya beans, sugar beet and lettuce. The crops were grown to maturity and the uptake of 14C determined by combustion and LSC. Residues in the edible portions of the commodities were <0.04 mg/kg haloxyfop equivalent. Owing to the low levels of radioactivity, the residues could not be identified. The results are shown in Table 4.
Table 4. Uptake of 14C by rotational crops from soil after treatment of original crop with [14C]haloxyfop at 0.56 kg ai/ha. Rotational crops planted 130 days after treatment of primary crop.
|
Rotational crop sample |
Days from planting to harvest |
14C as mg/kg haloxyfop equivalent |
|
Lettuce |
37 |
0.01 |
|
Lettuce |
50 |
0.01 |
|
Lettuce |
67 |
0.01 |
|
Lettuce |
95 |
0.01 |
|
Soya bean |
117 |
0.04 |
|
Soya bean forage |
50 |
0.02 |
|
Soya bean straw |
117 |
0.05 |
|
Wheat grain |
104 |
0.02 |
|
Wheat straw |
104 |
0.02 |
|
Sugar beet |
132 |
0.01 |
|
Sugar beet forage |
132 |
0.02 |
An emulsifiable formulation of [phenyl-U-14C]haloxyfop-butyl was applied to a crop of soya bean plants at a rate equivalent to 0.28 or 0.56 kg ai/ha. Carrots, sugar beet, lettuce, wheat and soya beans were planted in the same plot the following year, grown to maturity and analyzed to determine the uptake of 14C (Yackovich and Miller, 1984). The 14C was determined by combustion and LSC. The highest residues, 0.007 and 0.01 mg/kg haloxyfop equivalent, were seen in soya bean grain and straw after treatment of the original crop at the higher application rate. Residues in the edible portions of the other crops were <0.005 mg/kg haloxyfop equivalent. The residues were too low for isolation and identification. The results are given in Table 5.
Table 5. Uptake of 14C by rotational crops from soil after treatment of original crop with [14C]haloxyfop. All rotational crops planted 240 days after original application.
|
Rotational crop sample |
Application to original crop, kg ai/ha |
Days from planting to harvest |
14C as mg/kg haloxyfop equivalent |
|
Wheat grain |
0.28 |
95 |
<0.005 |
|
Wheat straw |
0.28 |
95 |
0.005 |
|
Soya bean |
0.28 |
161 |
<0.005 |
|
Soya bean forage |
0.28 |
75 |
<0.005 |
|
Soya bean straw |
0.28 |
161 |
<0.005 |
|
Soya bean |
0.56 |
161 |
0.007 |
|
Soya bean forage |
0.56 |
75 |
<0.005 |
|
Soya bean straw |
0.56 |
161 |
0.01 |
|
Lettuce |
0.56 |
39 |
<0.005 |
|
Lettuce |
0.56 |
47 |
<0.005 |
|
Lettuce |
0.56 |
69 |
<0.005 |
|
Carrot root |
0.56 |
153 |
<0.005 |
|
Carrot forage |
0.56 |
153 |
<0.005 |
|
Sugar beet |
0.56 |
139 |
<0.005 |
|
Sugar beet forage |
0.56 |
139 |
<0.005 |
Unlabelled haloxyfop-methyl was applied to soya beans at a rate of 0.28 kg ai/ha or to cotton at a rate of 0.28 or 0.56 kg ai/ha (Bjerke et al., 1985). At 25-34 or 92-148 days after application, the primary crop was harvested and wheat, lettuce or sugar beet planted as rotational crops in the same plots. The crops were grown to maturity and analyzed by gas chromatography to determine the uptake of haloxyfop. The highest residues were found in immature wheat forage grown on plots where the primary crop had been harvested 25 days after treatment, at a level of 0.01 mg/kg. Residues in the edible portions of the rotational crops were <0.01 mg/kg haloxyfop. The validated LOD was 0.01 mg/kg for all substrates except wheat straw, for which it was 0.02 mg/kg.
