Noxious Weeds and Management Strategies

Presented By:

Dale Whaley

Washington State University Extension

• A weed in one place could be a benefit in another

• Lots of weedy plants are used by birds, animals, insects and people

• It depends on the threat to resources or ecosystems

A honey bee visits bull thistle flowers

Are all weeds bad all the time?

F. & K. Starr, Starr Environmental, Bugwood.org

What is an invasive weed?

• Introduced / non-native

• Out-compete native plants

• Change local ecology

• Reproduce and spread rapidly D. Whaley, WSU Extension

Diffuse knapweed Infestation

Invasive plants like English Ivy transform forests and natural areas

Invasive plants harm native habitats and species.

J.M. Swearingen, USDI National Park Service, Bugwood.org

Increased Risk of Fire

D. Whaley, WSU Extension

D. Powell, USDA Forest Service, Bugwood.org

Invasive plants impact wildlife.

Humming bird stuck to Burdock burs eventually dying on the spot.

D. Whaley, WSU Extension

Understanding Washington’s Noxious Weed Law and List

Washington’s noxious weed law involves both public and private landowners.

King County NWCP

King County NWCP

What is a noxious weed?

• Non-native plant that impacts agriculture, wildlife, human health, land values or natural resources

• Defined and regulated by state law (RCW 17.10)

Visit the Washington State Noxious Weed Control Board website

• Noxious Weed List (WAC 16-750)– Weeds that are beginning to invade but not yet

widespread– Regulated by county noxious weed boards– Property owner required to prevent plants from

seeding• State Quarantine List (WAC 16-752)

– To prevent spread of new introductions (does not include already naturalized plants)

– Regulated by WSDA Nursery Inspection Program– Businesses are prohibited from selling plants or

seeds

Different lists regulate nurseries and landowners.

• Class A Weeds – new invaders, control required statewide, still a chance to eradicate

• Class B and C Regulated Weeds – control required only in particular counties or regions, still have a chance to stop them from getting established

• Non-Regulated Class B and C Noxious Weeds and Weeds of Concern – control not required but definitely a good idea whenever possible

Noxious weeds are ranked by how widespread they are.

Class A: Common Crupina Class B Regulated: Scotch broom

Class C Non-Regulated: Old man’s beard

Here are a few examples of weed classes.

J. Andreas, WSU Extension

King CountyUSDA APHIS PPQ Archive, Bugwood.org

Strategies for Managing Invasive Weeds

S. Shaw, King County NWCP

Ecology-based weed management is a long-term approach to weed management

Prevent

Control

RestoreWeed P

opulation G

rowth

Time

If less than 15% cover is desirable plants, then need to restore as well as control weeds

Get to know the type of weed in order to control it better.

• Annual• Biennial• Perennial• Woody

plant• Vine

Annual: Common Groundsel

Perennial: Spotted Knapweed

Biennial: Tansy Ragwort Shrub: Scotch BroomUtah State Univ. Archive, Bugwood.org

S. Dewey, Utah State Univ., Bugwood.orgL.L. Berry, Bugwood.org

King County NWCP

Getting to know your roots is especially important.

K.W. Zobrist WSU Extension

K.W. Zobrist WSU Extension

K.W. Zobrist WSU Extension

Practice integrated pest management.

• Prevention• Land management• Manual controls• Mechanical controls• Chemical controls• Biological controls

Prevention is the cheapest weed control method.

King County NWCPD. Whaley, WSU Extension

Manual control is targeted and effective, but also lots of work.

Pulling and bagging garlic mustard

Pulling gorse with a weed wrench

Digging giant hogweed

C. Gray, GA EPPC, Bugwood.org

S. Shaw, King County NWCP

S. Shaw, King County NWCP

Make sure you have a disposal plan for the weeds you dig up.

Noxious weeds that are regulated should go in the garbage.

Commercial yard waste composting is good for widespread weeds

Make sure the weeds are dead when you leave them

King County NWCPKing County NWCP

Mechanical control reduces the weed’s vigor without disturbing the soil.

Be careful not to move weed seeds on equipment.

Sheet mulching is another way to starve the weeds without disturbing the soil.

• Bark or woodchips over cardboard or layered newspaper - best for soil building

• Geotextile fabric - good for weed control• Black plastic - cheapest, not good for soil

King County NWCP T. Neuffer, WSU Extension

Biological Weed Control

The intentional use of one living organism to control/suppress another organism, such as WEEDS

Caesar, USDA ARS; bugwood.org

Nematodes

Piper, WSU; bugwood.org

Pathogens

Healing Hooves

Mammals

WSU Extension

Insects

How Does It Work?

Solution – “Classical Biocontrol”

40-50 Degree Latitude Belt

Classic Noxious Weed Infestation

Diffuse Knapweed

Solution – “Classical Biocontrol”

40-50 Degree Latitude Belt

• Host-specific~ only attacks target weed

• High searching capacity~ capable of dispersing and finding host

• High reproductive potential~ produces many offspring

• Long-lived adults~ increase searching, egg distribution, compensates for

asynchronies in phenology• Multi-voltinism

~ more than one generation a year

Ideal Biocontrol Agent Characteristics

Advantages

• Safe – USDA APHIS approves biological control agents before introduction into U.S.

• Ecologically desirable – herbicide alternative

• Insects are mobile• Long-term solution• Cost effective

Leafy Spurge Biocontrol

Limitations

• Long time to make impact• Subject to predators• May not establish at some

sites• Very slow approval of new

agents• No eradication

Predatory mite

Predatory insect

When To Use Biocontrol?

• Established weed infestations

• Remote, inaccessible, less disturbed areas

• Areas not controlled by other means

• Environmentally sensitive sites such as near water

Kittitas CNWCB

WSU Extension

When NOT To Use Biocontrol?

• Small or new infestations• Highly disturbed areas• Roads or traveled paths• Areas unfavorable for insect• On weeds with no approved

agentsMazerolle, Air

Mazerolle, Air

Weeds with Biocontrol Agents

• Scotch broom• tansy ragwort• meadow, diffuse, & spotted knapweed• Canada & bull thistle • purple loosestrife• St. Johnswort• yellow starthistle• puncturevine • rush skeletonweed• bindweed• Russian knapweed • Dalmatian & yellow toadflax • leafy spurge

Contact central Washington State’s biocontrol program for assistance and information.

• Site assessments to determine if biocontrol is an option

• Contact:– Dale Whaley, WSU Extension

509-745-8531 officedwhaley@wsu.edu

– Jennifer Andreas, WSU Extension253-445-4657 officejandreas@wsu.edu

Chemical control can be highly effective but requires special care and knowledge.

• Know your site• Know your weed• Know your product• Follow label

instructions• Always be cautious

and selective in your application

King County NWCP

There are a few special considerations when using herbicides in forestry.

Read the Forestry section in the PNW Weed Management Handbook: http://uspest.org/pnw/weeds

Here are a few useful websites for herbicide information.

• WSDA Pesticide Licensing and Education– http://agr.wa.gov/PestFert/LicensingEd/default.ht

m

• PNW Weed Management Handbook– http://pnwpest.org/pnw/weeds (see especially

the chapters on Control of Problem Weeds)• Crop Data Management Systems, Inc. – labels

and MSDS for most herbicides

– http://www.cdms.net/manuf/manuf.asp

A Complete Integrated Vegetation Management Approach

• Small Weed Infestations– Preventative measures such as; weed free

mulches or utilizing certified weed-free seed– Control or Eradication of the population

• Hand-pulling (physical control)• Mowing (mechanical control)• Spot spray (chemical control)

– Once completed; utilize preventative measures in order to minimize future weed invasions

A Complete Integrated Vegetation Management Approach cont…

• Large Established Weed Infestations– Large scale mowing or tillage operations to stop

seed production (mechanical control)• not recommended for perennial type weeds

– Herbicide applications to the weed perimeter (chemical control)

– Incorporation of weed eating insects or goats/sheep (biological control)

– Once completed; utilize preventative measures in order to minimize future weed invasions

Helping You Put Knowledge to Work!

Dale WhaleyRegional Extension Specialist

203 S. Rainier St., PO Box 550Waterville, WA 98858-0550509-745-8531 dwhaley@wsu.edu www.ncw.wsu.edu