1. Carol Randall USDA Forest Service Forest Entomologist
Noxious Weeds
Carol Randall
USDA Forest Service Forest Entomologist

2. What is a Weed? “A plant out of place.”
“A plant whose virtues have not yet been discovered.”
“Plants obstructing the activities of man.”
“A plant not valued for use or beauty, growing wild and rank, & regarded as cumbering the ground or hindering the growth of superior vegetation.”

3. Noxious vs. Obnoxious Weeds
Noxious weeds are designated by a regulatory agency- and by law managers must manage these plants
Obnoxious weeds are plants which can invade a site, but which are not considered enough of a threat to merit regulation

4. Why Manage Noxious Weeds?
Noxious weeds have the potential to:
Destroy wildlife habitat.
Reduce recreation opportunities.
Displace threatened and endangered species.
Reduce plant and animal diversity.
Disrupt waterfowl and migratory bird flight patterns and nesting habitats.
Cost millions of dollars in treatment and loss of productivity to private land owners.

5. "Noxious weed" means any plant having the potential to cause injury to public health, crops, livestock, land or other property; and which is designated as noxious by the director. (Idaho Code )
Have to be designated by law
Director of the Idaho State Department of Agriculture makes legal designation for Idaho
Idaho currently has 64 “noxious” weeds

6. ISDA Criteria for Designating Noxious Weeds
It must be present in but not native to Idaho
It must be potentially more harmful than beneficial to Idaho
Eradication must be economically and physically feasible
The potential adverse impact of the weed must exceed the cost of control

7. Three Levels of Concern- Idaho’s Noxious Weed List
Statewide Early Detection Rapid Response (EDRR) List
Statewide Control List
Statewide Containment List
Brazilian Elodea, Giant Knotweed, Canada Thistle

8. Statewide Early Detection Rapid Response (EDRR) List
Theoretically these plants are not well established in Idaho
Focus is to identify populations of these weeds and eradicate them
"Eradication" means the elimination of a noxious weed based on absence as determined by a visual inspection by the control authority during the current growing season
European Frogbit
Policeman’s Helmet

9. Idaho’s Statewide EDRR List (15)
Common Name
Scientific Name
Brazilian Elodea
Egeria densa
Common/European Frogbit
Hydrcharis morsus-ranae
Fanwort
Cobomba caroliniana
Feathered Mosquito Fern
Azolla pinnata
Giant Hogweed
*Heracleum mantegazzianum
Giant Salvinia
Salvinia molesta
Hydrilla
Hydrilla verticillata
Policeman's Helmet
*Impatiens glandulifera
Squarrose Knapweed
*Centaurea triumfetti
Syrian Beancaper
*Zygophyllum fabago
Tall Hawkweed
*Hieracium piloselloides
Variable-Leaf-Milfoil
Myriophyllum heterophyllum
Water Chestnut
Trapa natans
Yellow Devil Hawkweed
*Hieracium glomeratum
Yellow Floating Heart
Nymphoides pelata

10. Statewide Control List
"Control" means any or all of the following: prevention, rehabilitation, eradication or modified treatments
Buffalobur
Dyer’s Woad
Mediterranean Sage

11. Statewide Control List (22)
Common Name
Scientific Name
Black Henbane
*Hyoscyamus niger
Meadow Knapweed
*Centaurea debeauxii
Bohemian Knotweed
*Polygonum bohemicum
Mediterranean Sage
*Salvia aethiopis
Buffalobur
*Solanum rostratum
Musk Thistle
*Carduus nutans
Common Crupina
*Crupina vulgaris
Orange Hawkweed
*Hieracium aurantiacum
Common Reed (Phragmites)
*Phragmites australis
Parrotfeather Milfoil
Myriophyllum aquaticum
Dyer's Woad
*Isatis Tinctoria
Perennial Sowthistle
*Sonchus arvensis
Eurasian Watermilfoil
Myriophyllum spicatum
Russian Knapweed
*Acroptilon repens
Giant Knotweed
*Polygonum sachalinense
Scotch Broom
*Cytisus scoparius
Japanese Knotweed
*Polygonum cuspidatum
Small Bugloss
*Anchusa arvensis
Johnsongrass
*Sorghum halepense
Vipers Bugloss
*Echium vulgare
Matgrass
*Nardus stricta
Yellow Hawkweed
*Hieracium caespitosum

12. Statewide Containment List (27)
 "Containment" means halting the spread of a weed infestation beyond specified boundaries
White Bryony
Spotted Knapweed
Poison Hemlock
Yellow Flag Iris

13. Statewide Containment List (27)
Common Name
Scientific Name
Canada Thistle
*Cirsium arvense
Poison Hemlock
*Conium maculatum
Curlyleaf Pondweed
Potamogeton crispus
Puncturevine
*Tribulus terrestris
Dalmatian Toadflax
*Linaria dalmatica ssp. dalmatica
Purple Loosestrife
*Lythrum salicaria
Diffuse Knapweed
*Centaurea diffusa
Rush Skeletonweed
*Chondrilla juncea
Field Bindweed
*Convolvulus arvensis
Saltcedar
*Tamarix sp.
Flowering Rush
Butomus umbelltus
Scotch Thistle
*Onopordum acanthium
Hoary Alyssum
*Berteroa incana
Spotted Knapweed
*Centaurea stoebe
Houndstongue
*Cynoglossum officinale
Tansy Ragwort
*Senecio jacobaea
Jointed Goatgrass
*Aegilpos cylindrica
White Bryony
*Bryonia alba
Leafy Spurge
*Euphorbia esula
Whitetop
*Cardaria draba
Milium
*Milium vernale
Yellow Flag Iris
*Iris psudocorus
Oxeye Daisy
*Leucanthemum vulgare
Yellow Starthistle
*Centaurea solstitialis
Perennial Pepperweed
*Lepidium latifolium
Yellow Toadflax
*Linaria vulgaris
Plumeless Thistle
*Carduus acanthoides

14. Something you probably did not know about Idaho…
We are one of the most progressive states in the nation when it comes to addressing noxious weeds

15. Idaho’s Statewide Weed Education and Advocacy Groups
Idaho Association of Weed Control Superintendents (IAWCS)
Idaho Weed Coordinating Committee (IWCC)
Idaho Weed Control Association (IWCA)
Idaho Weed Awareness Campaign (IWAC)

16. Other Assets: Weed Science Program at the University of Idaho
Research Programs at other State Institutes of Higher Education
Cooperative Weed Management Areas

17. Cooperative Weed Management Areas (CWMA)
Most of Idaho’s land mass is
contained in one of 32 Cooperative
Weed Management Areas (CWMA)
CWMAs are formed when the
landowners and land managers of
a given area come together and
agree to work cooperatively to
control weeds
CWMAs identify the highest priority
weed control activities for their area,
then share resources to get priority
work done

18. So why is an entomologist talking about weeds?
I work closely with county weed superintendents, CWMA’s, and weed researchers on classical weed biological control- or the use of insects to help control weeds

19. Idaho- A Biological Control of Weeds Super Power
We have weed biological control researchers at our land grant college
We have a statewide biological control coordinator (ISDA/BLM)
We have designed and implemented the only statewide biological control of weeds monitoring program
We have a number of statewide groups which cooperate on biological control of weed projects

20. How do you develop a weed treatment strategy
Most successful weed management strategies incorporate a number of methods: herbicides, mechanical, cultural, and when appropriate biological control.
Use of multiple methods simultaneously is called Integrated Pest Management- or IPM.
A good weed treatment strategy relies on realistic management objectives, accurate weed identification and mapping, as well as post treatment monitoring. (“DID IT WORK?”)

21. Weed Biocontrol and other Control Methods
Chemical Control
Picloram (Tordon)
2,4-D
Glyphosate
Dicamba
Cultural Control
grazing
(sheep, goats)
hand-pulling, tilling
burning
IPM
Biological Control
- insects
pathogens

22. What is Biological Control of Weeds?
The use of one organism to control another.
Classical Biological Control is the introduction of control agents- usually insects- into a region that is not part of their natural range, to suppress permanently the populations of selected target weeds usually also introduced into that region
SUPPRESS not GET RID OF!
Mostly geared towards containment list

23. How Biological Control Works
Biocontrol agents may control weeds by destroying seeds, root, or stems; by weakening or stressing the weed; and/or by limiting the weeds ability to reproduce.
Bioagent feeding may also help secondary pathogens infect weeds through damage scars.
Once established and feeding in your weed infestations, biological control agents will continue to attack your weeds, month after month, year after year.

24. Lesser knapweed flower weevil
Initial release
Biocontrol population density
Lag
time
Establishment of
biocontrol agents
Exponential increase
Larinus minutus

25. Biological Control Agent Outbreaks May Control Weed Infestations
Beverly Bridge, AB
Aphthona
nigriscutis
Leafy Spurge

26. Aphthona flea beetles for leafy spurge
Biocontrol agents behave like insect pest species
Mass outbreaks

27. Biological Control Basics:
Uncertainty over ultimate scale of impact
Long-term cost effective
Irreversible
Self dispersing (even into difficult terrain)
Uncertain ‘non-target’ effects in ecosystems
Gradual in effect, generally environmentally benign
Protracted time until impact likely
Continuous action
Initial high costs
Target specificity
Disadvantages
Advantages

28. Things to Know: Efficiency of agents cannot be be be be be guaranteed.
Will not work every time in every situation.
Will not “eradicate” the weed.
May not provide the desired level of control.
Some times it might take awhile (years) before see biological control impact.