rate limitation and efficacy trials for low-volume … ncwss...low volume basal bark herbicide...

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

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


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


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


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.


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



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…


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


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




• Tag and treat 21 plants with each rate class. Follow mortality through time. Determine efficacy.

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


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

rate limitation and efficacy trials for low-volume … ncwss...low volume basal bark herbicide...

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