Field bindweed is extremely susceptible to aminocyclopyrachlor compared to
other weed species. Laboratory studies were conducted to determine if
absorption, translocation, and metabolism of aminocyclopyrachlor in field
bindweed differs from other, less susceptible species. Field bindweed plants
were treated with 3.3 kBq 14C-aminocyclopyrachlor by spotting a
single leaf mid-way up the stem with 10 µl of herbicide solution. Plants
were then harvested at set intervals over 192 h after treatment (HAT).
Aminocyclopyrachlor absorption reached a maximum of 48.3% of the applied
radioactivity by 48 HAT. A translocation pattern of herbicide movement from
the treated leaf into other plant tissues emerged, revealing a nearly equal
aminocyclopyrachlor distribution between the treated leaf, aboveground
tissue, and belowground tissue of 13, 14, and 14% of the applied
radioactivity by 192 HAT. Over the time-course, no soluble
aminocyclopyrachlor metabolites were observed, but there was an increase in
radioactivity recovered bound in the nonsoluble fraction. These results
suggest that aminocyclopyrachlor has greater translocation to belowground
plant tissue in field bindweed compared with results from other studies with
other herbicides and other weed species, which could explain the increased
level of control observed in the field. The lack of soluble metabolites also
suggests that very little metabolism occurred over the 192 h time
course.