Corey Moffet, USDA-ARS,
U.S. Sheep Experiment Station,
Dubois, ID
 Determine
the effect of timing of
herbicide application on efficacy and
subsequent reseeding success
 The study was initiated in 2008
• Large plot study (Aberdeen, ID)
 Crested wheatgrass control treatments and
reseeding success
• Small plot study (Dubois, ID)
 Crested wheatgrass TNC trends and phenology
 Herbicide efficacy
 Site
Description
• Near Aberdeen, ID
 33 ha area
• Loamy 8-12 Wyoming
big sagebrush/
bluebunch wheatgrass
site
• Seeded to crested
wheatgrass in 1996
after wildfire

Main plots (80)
• Disked in spring or not
• Glyphosate application (3.2
l/ha
 None, vegetative stage,
reproductive stage, or fall
regrowth
• Control treatment/seeding
year
 2008 or 2009
• 5 reps

Subplots (160)
• Half the main plot seeded
the other half not

Repeated measurements
• 1 and 2 years after seeding
Drill mix
Anatone bluebunch wheatgrass
Magnar basin wildrye
Bannock thickspike wheatgrass
Thurber’s needlegrass
Broadcast mix
Maple Grove Lewis flax
Mtn. Home Sandberg bluegrass
Hotrock penstemon
Wyoming big sagebrush
Rubber rabbitbrush
* The
%
40
10
10
10
Full
Rate
8
8
6
6
5
5
5
10
5
8*
4*
8*
0.5*
3*
#PLS/
ac
3.20
0.80
0.60
0.60
0.40
0.20
0.40
0.05
0.15
PLS/linear
ft.
20
5
4
5
5
9
5
4
5
broadcast seeding rate for each component is double the standard full
seeding rate for drilling

Line point intercept
• 5 lines
 8, 15, 22, 29, & 36m
• 20 points/line
 Every m between 6 and 25

Density
• Abundant species
 20 quadrats, 0.04 m2
• Common species
 20 quadrats, 1 m2
• Rare species
 Belt transect
 U.S.
Sheep
Experiment Station
 Herbicide
application plots
 Plants sampled for
TNC trend
June 6, 2008
 Timing
of herbicide
application and
clipping
• Main plot
 Herbicide application
date
• Split plot
 Half clipped 2 wks
before herbicide
 Total
Nonstructural
Carbohydrate (TNC)
• 20 plants sampled on
alternate wks
• 10 clipped 2 wks prior
to sampling
May 22, 2008 - Clipped
June 22, 2008
June 6, 2008 - Sprayed
Summary
 Determine
whether herbicide is more
efficacious on crested wheatgrass if it is
applied when photosynthate is being
translocated to crown meristems.
• Determine whether clipping can be used to
increase the carbohydrate sink
 Determine
whether differences in
crested wheatgrass control translates
into greater reseeding success