Rate limitation and efficacy trials for low-volume basal bark treatments
of C. orbiculatus and L. maackii with aminopyralid and triclopyr
Karla Gage, Southern Illinois University Carbondale/River to River Cooperative Weed Management Area
Scott Flynn, Dow AgroSciencesChris Evans, University of Illinois Extension/Illinois Department of Natural
Resources – Illinois Wildlife Action PlanDavid Gibson, Southern Illinois University Carbondale
Amur honeysuckleLonicera maackii
Amur honeysuckleLonicera maackii
Southern Illinois University, Database of Exotic Plant Species
Observations of Amur honeysuckle
Decade
70's 80's 90's 00's
Num
ber
of
ob
serv
atio
ns
0
10
20
30
40
Amur honeysuckleLonicera maackii EDDMapS. 2015.
Celastrus orbiculatusOriental bittersweet
Celastrus orbiculatusOriental bittersweet EDDMapS. 2015.
Low Volume Basal Bark Applications
Low Volume Basal Bark Applications
Triclopyr + aminopyralid
Low Volume Basal Bark Herbicide Applications
• In dense stands of invasive species, land managers may exceed labeled rate, but this has not been quantified.
• This knowledge will help ensure the safe use of herbicide and the protection of the ecological resources which land managers seek to conserve through the treatment of invasive woody plants.
Low Volume Basal Bark Herbicide Applications
• Test the efficacy of control of five rate combinations of triclopyr and aminopyralid for each woody species.
• The addition of a small percentage of aminopyralid (1 – 2%) and a reduction of the rate of triclopyr ester may increase control efficacy.
Questions:
At what stem densities are land managers at risk of exceeding labeled rate in low volume basal bark applications of triclopyr?
Does the addition of aminopyralid to triclopyrester increase control efficacy?
Experiment 1:
Objective: Establish the mathematical relationship between stem density and volume of solution applied.
Experiment 1: Methods• Establish circular plots – 5 m radius (0.02 acre)• Treat each plot (covering the stem from ground level up to
15”) using water. Repeat applications 3 times (3 different applicators)
• Measure volume of water in sprayer before and after each application
• Count stem density per plot, measure stem diameter• Calculate stand basal area for Amur honeysuckle and
Oriental bittersweet• Establish relationship between stem density, basal area and
spray volume per plot
Stem Count
0 20 40 60 80 100
Sp
ray V
olu
me
(m
l)
0
100
200
300
400
500
f(x) = 34.691 + (3.567 * x)
R2 = 0.81, p = 0.009
Relationship: spray volume & stem count
Amur honeysuckleLonicera maackii
Stem Count
0 10 20 30 40 50 60
Sp
ray V
olu
me
(m
l)
0
50
100
150
200
250
300
350
400
f(x) = 11.434 + (5.200 * x)
R2 = 0.81, p<0.001
Celastrus orbiculatusOriental bittersweet
Conversion Factor
Conversion factor = 1.33 for water BOBPSI
ml/
min
ute
Stem Density Estimate per 0.4 ha (1 acre)
0 1000 2000 3000 4000
He
rbic
ide
Vo
lum
e in
Oil
Ca
rrie
r (m
l)
0
2000
4000
6000
8000
20% Triclopyr
15% Triclopyr
10% Triclopyr
2% Aminopyralid
1% Aminopyralid
Triclopyr rate limit
Aminopyralid spot spray rate limit
Aminopyralid rate limit
Stem Density Estimate per 0.4 ha (1 acre)
0 1000 2000 3000 4000
He
rbic
ide
Vo
lum
e in
Oil C
arr
ier
(ml)
0
2000
4000
6000
8000
20% Triclopyr
15% Triclopyr
10% Triclopyr
2% Aminopyralid
1% Aminopyralid
Triclopyr rate limit
Aminopyralid spot spray rate limit
Aminopyralid rate limit
Spray plot stem densities and spray volumes are scaled-up to 1 acre to estimate risk of exceeding labeled use rate.
Amur honeysuckleLonicera maackii
Application limits –estimated # stems/ac
Rate (v/v)
Limit/ac Limit/ac Est. stems/ac
Est. stems/1m radius
Equation for stem density to herbicide volume
1% 7 fl. oz 217 ml 4077 16 y = 23.773 + 0.047x
2% 7 fl. oz 217 ml 1786 7 y = 47.547 + 0.095x
1% 14 fl. oz 414 ml 8232 33 y = 23.773 + 0.047x
2% 14 fl. oz 414 ml 3862 15 y = 47.547 + 0.095x
Amur honeysuckleLonicera maackii
Stem Density Estimate per 0.4 ha (1 acre)
0 500 1000 1500 2000 2500 3000
Herb
icid
e V
olu
me in O
il C
arr
ier
(ml)
0
2000
4000
6000
Fewer stems, less risk…
Celastrus orbiculatusOriental bittersweet
Application limits –estimated # stems/ac
Rate (v/v)
Limit/ac Limit/ac Est. stems/ac Est. stems/1m radius
Equation for stem density to herbicide volume
1% 7 fl. oz 217 ml 3023 12 y = 7.836 + 0.069x
2% 7 fl. oz 217 ml 1459 6 y = 15.671 + 0.138x
1% 14 fl. oz 414 ml 5869 23 y = 7.836 + 0.069x
2% 14 fl. oz 414 ml 2886 12 y = 15.671 + 0.138x
Celastrus orbiculatusOriental bittersweet
Rate Limits
• Applications of triclopyr do not approach rate limit of 7571 ml per 0.4 ha (8 quarts per 1 acre)
• Partial acreage application of 1 or 2 % aminopyralid may be necessary
Experiment 2:
Objective: To test control efficacy of varying rate combinations of aminopyralid and triclopyrester on Amur honeysuckle and Oriental bittersweet.
5 rate combinations: • 20% triclopyr
• 15% triclopyr + 1% aminopyralid
• 15% triclopyr + 2% aminopyralid
• 10% triclopyr + 1% aminopyralid
• 10% triclopyr + 2% aminopyralid
• Tag and treat 21 plants with each rate class. Follow mortality through time. Determine efficacy.
Celastrus orbiculatusOriental bittersweet
1 year AT
• Amur honeysuckle
– Treatment difference: χ2=11.29, p=0.05
• Oriental bittersweet
– No difference between treatments
Amur honeysuckle
Herbicide treatments
T20 T15/A1 T15/A2 T10/A1 T10/A2
Perc
enta
ge o
f surv
ivors
0
2
4
6
8
10
Amur honeysuckleLonicera maackii
Nu
mb
er
of
surv
ivo
rs
# survivors out of 21 plants in each treatment
A A A
A
B
7 7 7
8
1
• Amur honeysuckle control was best with 15% triclopyr + 2% aminopyralid
– If treating area with > 1700 stems per acre, spot treating/treating half the acre is necessary to stay within the labeled use rate
– Applying no more than 5.5 gallons of spray solution to 50% of an acre
AcknowledgmentsSIUC Center for Ecology & IDNR summer interns:Erick Baumberger & Adam Jackson