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Selecting Herbicide
Crop Science
Effective
weed
control depends
on selecting the
right herbicide.
Herbicides
are
classified according
to the way they
destroy weeds.
Types of Herbicide
Contact
Herbicide
Growth Regulators
Soil Sterilants
Contact Herbicide
 Kills
plants by exposure
 Works best on Annuals
 May
only kill parts of
the plant in contact
Growth Regulator
 Alters
growth or
metabolic processes
 Absorbed by the roots,
stems, or leaves
The
movement of
a herbicide inside
of a weed is known
as translocation
Soil Sterilant
Prevents the growth
of plants in the soil
Most useful in
greenhouse
Selectivity of
Herbicides
Selective Herbicide
Kills only certain
plant species and
not others
Selective Herbicide
Possible to spray
in field without
injuring crop
Non-Selective
Herbicide
Kills
all plants
regardless of species
Non-Selective
Herbicide
Should
not be used
in growing crops
Using Herbicides
Time of
Application
Herbicides may
be applied at
three times:
Pre-plant
Pre-emergence
Post-emergence
Using Herbicides
Area of
Application
4 general areas
of application
are used:
Band
 Treating
narrow strips
with herbicide
 Used in cotton & corn
Broadcast
Treating
the entire
area of a field
Used with pastures
Not used in row crop
Directed Appl.
Treating
only selected
or targeted plants
Some use in row crop
Used a lot with trees
Spot Application
Treating
only certain
areas in field
Saves cost plus labor
Protects environment
Applying Herbicide
Knowing
when and
how to apply are
important for effective
weed control