Herbicides
267
• 
Safety - page 25 • First aid - page 33 • Resistance management - page 41
How it Works
Thorough coverage of the plants is essential for consistent control. Signal herbicide is absorbed by the leaves and
is rapidly translocated to the growing points of leaves and stems. Approve contains two components, bromoxynil
and 2,4-D. Bromoxynil is a contact type herbicide, which inhibits photosynthesis and plant respiration. 2,4-D is
a hormone type herbicide, which causes abnormal growth, affects respiration, food reserves and cell division in
broadleaf plants. Absorbed primarily by leaves and stems and translocated to the growing tips and roots.
Expected Results
Small burn spots on the leaf can appear within hours. Death takes up to 2 weeks. Grassy weeds: Depending on
species, growing conditions and crop competition, leaves and growing points turn yellow within one to three weeks
after application. Further colour changes and loss of vigour will be observed, followed by a browning and complete
control 3-5 weeks after application.
Restrictions
Rainfall
:
Rainfall within 2 hours of application may reduce weed control.
Grazing
:
Do not graze or cut for livestock feed within 30 days of application. Withdraw meat animals 3 days before
slaughter.
Pre-harvest Interval
:
Do not harvest within 30 days of application.
Re-cropping
:
No re-cropping restrictions the year after application.
Environmental Precautions
Toxic to small mammals, birds, aquatic organisms and non-target terrestrial plants.
Runoff
:
Avoid contamination of aquatic areas and sensitive terrestrial areas by using the recommended buffer zones.
Leaching
:
The use of this chemical may result in contamination of groundwater, particularly in areas where soils are
permeable (e.g. sandy soil) and/or the depth to the water table is shallow.
Toxicity
Approve: Moderate acute mammalian toxicity. Acute oral LD
50
(
rats) = 606 mg/kg. Intake of a large dose may cause
convulsions, sudden collapse and coma. Can be absorbed through the skin. Very toxic to fish. Signal herbicide: Acute
oral LD
50
(
rats) = 2,276 mg/kg.
Storage
Approve will solidify at temperatures below -20
o
C but will become useable at temperatures above 0
o
C.
Signal M
Group 1, 4, 6
Formulation
Product
Company
Active ingredient
Formulation Container size
Signal (PCP# 29172)
Nufarm Agriculture
Inc
Clodinafop-propargyl: 240 g/L
Emulsifiable
concentrate
1.84
L
Mextrol (PCP# 26999)
Bromoxynil 225g/L +225 g/L MCPA
10
L
Signal Adjuvant (PCP# 29173)
Surfactant blend: 17%
6.4
L
Crop and Staging
Crop
Stage
Spring wheat (including durum)
2
leaf to early flag leaf
Signal D (cont’d)