Auxin-Type
Herbicide Bioassay Reference Photos
These photos have been produced as an addendum to the above report
(referred to as the Guidance Report).
The photos depict red clover seeds (Trifolium pratense)
grown in peat-based reference media (control) and compost-based
growth media containing varying concentrations of the auxin-like
herbicide clopyralid.
Observations of the growth of red clover can be used to indicate
the potential presence of auxin-like herbicide in composted products,
allowing associated risk of potential damage to sensitive plants
to be avoided.
Click on the photos for a higher resolution image.
0 ppb Herbicide Concentration |
| Mix:
Peat combined with sand to form a control growth media. This
media contains no herbicide and provides excellent growth
conditions for comparison with the compost-based treatments
below. |
 |
| Observations:
Normal growth and development, cotyledons and first leaves
flat, stems erect. |
| Action:
None. No auxin-like herbicide damage detected. |
 |
 |
| No
auxin-like herbicide damage detected |
Top
1ppb Herbicide Concentration |
| Mix:
Compost test product combined with peat and sand to form a
compost growth media with herbicide concentration of 1 ppb.
This represents a herbicide concentration of 2 ppb in the
actual compost. |
 |
| Observations:
Growth continues, very slight down-turning of cotyledons and
first leaves, some stems slightly bent. First leaves have
slightly smaller surface area than those grown in absence
of herbicide (0 ppb above). |
| Action:
Very slight auxin-like herbicide damage, recommend laboratory
analysis to confirm concentration. |
 |
 |
Top
2 ppb Herbicide Concentration |
| Mix:
Compost test product combined with peat and sand to form a
compost growth media with herbicide concentration of 2 ppb.
This represents a herbicide concentration of 4 ppb in the
actual compost. |
 |
| Observations:
Growth continues, slight downturning of cotyledons and first
leaves, some stems slightly bent. First leaves have a smaller
surface area than those grown in the absence of the herbicide
(0 ppb above). |
| Action:
Slight auxin-like herbicide damage, recommend laboratory analysis
to confirm concentration. |
 |
 |
Top
6 ppb Herbicide Concentration |
| Mix:
Compost test product combined with peat and sand to form a
compost growth media with herbicide concentration of 6 ppb.
This represents a herbicide concentration of 12 ppb in the
actual compost. |
 |
| Observations:
Growth generally stunted, some stems bent. Downturned cotyledons
with smaller surface area, first leaf not opening or not developing
at all. |
| Action:
Slight auxin-like herbicide damage, recommend laboratory analysis
to confirm concentration. |
 |
 |
Top
16 ppb Herbicide Concentration |
| Mix:
Compost test product combined with peat and sand to form a
compost growth media with herbicide concentration of 16 ppb.
This represents a herbicide concentration of 32 ppb in the
actual compost. |
 |
|
Observations:
Growth significantly stunted. Most cotyledons curled into
half circle, most stems bent. First leaf does not develop. |
| Action:
Slight auxin-like herbicide damage, recommend laboratory analysis
to confirm concentration. |
 |
 |
|
