Management of invasive Phragmites australis: a

cautionary tale

Andrea Dávalos SUNY Cortland

andrea.davalos@cortland.edu 607-753-2709

Talk outline

1. Management assessment in the Adirondacks Park

2. Prospect of biological control

Brendan Quirion & Zack Simek Adirondack Park Invasive Plant Program

bquirion@tnc.org & Zachary.simek@tnc.org 518-576-2082

Bernd Blossey Cornell University

bb22@cornell.edu 607-227-1572

Common Reed (Phragmites australis)

How Should We Assess Success?

- Plants removed - Area treated - Dollars spent

Focus on the outcome

- Reduction in invasive plant abundance

- Reestablishment of native species

- Area under protection

Adirondacks

ADK Park Boundary

Lakes/Ponds

!(

Streets

Wetlands

State Land

PRISM Boundary

Quirion et al 2018

2003 2010

Herbicide Treatments - 2010

Site monitoring

• Location of population • Area of population • Phragmites cover • 2010-2016

• 10 control sites • Monitored 3 – 5 years • Slight increase in area of Phragmites at majority of sites • Three largest sites – decrease in area

What happens if we do not control?

Quirion et al 2018

Why didn’t Phragmites expand?

• At other locations Phragmites expanded 11-46%

In the Adirondacks: • Less human disturbance • Populations might have

reached local limits of wetland area

• Biotic resistance (?)

What happened when herbicide was applied?

1. Decreased area of Phragmites

2. Decreased cover of Phragmites

3. Overtime, locally eradicated small patches of Phragmites

Was treatment successful? • Depended on initial Phragmites area and cover

Change in area

• Decrease in area occurred rapidly but stabilized afterward

• Decrease was greater for sites treated intermittently - because these sites were smaller overall

Quirion et al 2018

Change in cover

• Decreases in cover were more dramatic & achieved rather quickly

Quirion et al 2018

Eradication

• Eradicated Phragmites from 35% of sites Small

0.36 m2 less than 4 sq-ft

Medium 45 m2

1%

26%

83%

Large >3000 m2

Size of a room

Large house

Quirion et al 2018

2010 2011

2014 2015-16

Once eradicated…

Likelihood of Phragmites reappearance was low and decreased with number of years of absence

Considered eradicated

Quirion et al 2018

Success story?

• Able to eradicate small patches • Long term commitment

• Larger patches need to be treated in perpetuity

• Pre and post-treatment quantitative

assessments are essential components of NIS management and should be incorporated into management plans and prioritized for funding

Is biocontrol for Phragmites australis feasible?

The picture at left show leaves from invasive (top) and native (bottom) Phragmites australis plants. The picture on the right shows the red stems from native P. australis. Photo credits: Katherine Hollins

This image cannot currently be displayed.

European stem mining noctuids Archanara geminipuncta and A. neurica

Blossey et al unpublished

Host specificity testing

In no-choice tests, both noctuids accept native Phragmites – with reduced survival In open field choice tests: occasional oviposition on native Phragmites (<7%) Occasional feeding does not always result in demographic effects

Blossey et al unpublished

In conclusion • Increasing resources to manage invasive

Phragmites, but limited information about the impacts and effectiveness of management

• Invasive Phragmites jeopardizes native biota and native Phragmites

• All management methods have inherent risks • Long-term herbicide applications often result in

unintended consequences for native biota • Potential threats of biocontrol, are smaller than

allowing expansion of invasive Phragmites or continued use of ineffective methods.

Questions?