Definitions

• Control – prevention of spread by removing fruits and limiting vegetative spread

• Eradicate – to completely remove a species from a location

Topics

•Approaches to control

•Methods of control– Mechanical– Chemical (types of herbicides, application

methods

•Selected PNW species

Assessing Invasive Species Threats

At the landscape scale it is necessary to take two approaches

simultaneously and iteratively:

By spatial distribution of invaders and

conservation goals(Superlative sites)

By invasive species(Scary species)

Two Assessment Approaches

•Species Based

•Site Based

Acr

es I

nfe

sted

Eradication simple

Plant absent

Era

dic

atio

n

feas

ible

Era

dic

atio

n u

nli

kely

,

inte

nse

eff

ort

req

uir

ed

Scattered locations

Numerous locations

At or near biological potential

Local control and management only

Weed Increase Over Time and Control Potential

Co

ntr

ol

Co

sts

Public awareness typically begins

Introduction

Time

Detection

A = AlhagiH = HydrillaP = Peganum

From: Rejmanek,M. and M. Pitcairn (2002)

Study Conclusions

• Eradication possible if under 1 hectare• 1/3 of infestations between 1 and 100

hectares eradicated• ¼ of those between 101 and 1000 eradicated• Cost goes up greatly with size• SO early detection and rapid response is

essential!!!!!Rejmanek and Pitcairn 2002

Bradley Method

• Work in the least invaded areas first, working towards invaded areas

• Make minimal disturbance – mulch if you must disturb the soil

• Let native plant regeneration and your maintenance ability dictate the rate of weed removal – never overclear

Manual and Mechanical

• Hand pulling -can use volunteers

-good for small infestations-can have low ecological impact-need to keep equipment clean-minimize disturbance! Mulch!-best for annuals or shallow rooted perennials

Weed Wrench

Manual and Mechanical

•Tillage/hoeing

•Mowing, brush cutting–Best for species that don’t coppice

–“controls” – does not eradicate except through repeated use

•Girdling – remove cambium (do not use on coppicing species, beware creating a hazard tree!)

•May need to remove stem fragments

Mechanical

•Mulching – bark, hay, cardboard

carpet, etc.

•Flooding/drawdowns

•Fire

Manual or MechanicalSoil solarization

- kills tissue if around 113-131 degrees Fclear plastic more likely to heat to this

- soil should be moist- not as good for rhizomatous species- may alter soil biology and chemistry

Steam or Hot Water

• Hot water breaksdown theepidermis, theplant becomes dehydrated

• Waipuna now promotingfoam – coconut syrup andwater

Infrared Technology

• Heats to 1000oC

• Bursts cells – stops

photosynthesis

• Not good for deeply

rooted species

Grazing

• Can eliminate or encourage invasive plants

• Can use cattle, goats, sheep, geese, chickens, ducks, etc.

• Goats eat broadest list of weeds• 500 sheep = 4/5 acres/day• Need to fence or pen them in• May disturb soil, may pass

seeds

Mechanisms - Herbicides

• Inhibit respiration–Arsenic compounds–Metallo-organics (also based on arsenics)–Phenols

• Can be very toxic to mammals

Mechanisms - Herbicides

• Auxins – 2,4,D – causes excess cell division and overgrowth, good on broadleaf weeds, non-persisting, low mammalian toxicity 2,4,5,T – better for woody plants >> has dioxin = Agent Orange, causes cancer

• Common now: Clopyralid (persists in compost), picloram, triclopyr (Garlon, Brush B Gone)

Mechanisms - Herbicides

• Inhibitors of biosynthetic processes- Cell division – “pre-emergent”- Nucleic acid or protein synthesis inhibitors

– “pre-emergent”- Glyphosate – non-selective contact

herbicide, interrupts an amino acid production pathway not found in animals – “post-emergent,” Rodeo® used for aquatics

Adjuvants

• Added to facilitate mixing, effectiveness, or application of herbicide

• “Surfactants,” “spreader-sticker”

• Usually chemically active, but may be termed “inert”

• Sometimes included, if not, research to find recommended one for what you use

Considerations using Herbicides

• Non-target species

• Use best management practices for handling concentrates

• Follow ALL laws

• Must post treated areas

• Carefully assess site conditions, including weather

• Likely cannot use volunteers

Methods of Application

• Foliar – spot, boom

• More herbicide

delivered to

non-targets

• May need a

surfactant

Methods of Application

• Basal bark

• 6” band 1’ up stem

• Must mix with

low ester oil

• Best for smaller

shrubs

Methods of Application

• “Hack and squirt”

• Cut every 2 in or

so of stem

• Good for small trees

4-5” dia

• Creates hazard trees!

Methods of Application

• Cut stump “Cut and dab”• Only need to

treat the cambium• Apply immediately

after cutting• Paintsticks handy• May need to reapply• Not as good in early spring

Methods of Application

• Injected into cambium

• Can be good for some

herbaceous as well as

woody

• Little human contact with

herbicide

• Buy appropriate injectors

Reed Canary GrassPhalaris arundinacea

• Rhizomatous grass

• Mow 5X +/yr

• Mulches (+ cardboard)

• Glyphosate (2%)

• Shading with plantings

Atlantic/English Ivies

Hedera hibernica ‘HibernicaH. helix ‘Pittsburg’

H. helix ‘Baltica’

H. helix ‘Star’

Ivies

• Fast-growing ground cover

• Remove vertical vines first

• Pull and wad vines on ground

• Can use string trimmer followed by glyphosate or triclopyr

Japanese KnotweedFallopia japonica

• Strongly rhizomatous shrub• Very hard to kill• 2X/month mowing for

3 years• Injection – 5 ml of

100% glyphosate• Triclopyr or glyphosate

Himalayan blackberryRubus armeniacus

• Repeated mowing• Digging• Cut stump, treat

with triclopyr or

triclopyr + 2,4 - D

Iris pseudacorusYellow flag iris

• Freshwater aquatic but

drought resistant

• Seeds and rhizomes

• Dense thickets along shore

• Dig by hand or machine

• Cutting + glyphosate

Scotch broom Cytisus scoparius

• Prairies, grasslands

• Nitrogen-fixer

• Pull or cut stump

• Seeds long lived

herb robert, stinky bob Geranium robertianum

• Herbaceous annual• Spreads by explosive seeds• May be allelopathic• Easy to pull• Seeds live 5+ yrs

hedge bindweed Calystegium sepium

• Older name Convolvulus sepium• Fleshy rhizomes 1-2 ft deep• Blankets shrubs• Likes wetter soils• Responds to triclopyr –

pull as much as possible,

mulch, then spray as vines

grow

Resources

• TNC Weed Control Handbook

http://tncweeds.ucdavis.edu/handbook.html

• TNC “Stewardship Abstracts”

http://tncweeds.ucdavis.edu/esadocs.html

Conclusions

• Start with smallest infestations first

• There are a variety of mechanical and chemical control methods –combinations may provide the best control

• For PNW invaders there are a number of strategies for control that must be tailored to the biology of the species