OUTLINE: Invasive species L16 and L17

OVERVIEWImpactsWhich species invade?Which communities are invaded?

MANAGEMENTPrioritiesEradicationBiological control

Management options

Number of non-natives = Number introduced X survival rate

OptionsPrevent entry

How are non-native plants introduced?

AccidentallyIn hay or seedsIn ships ballast

IntentionallyMedicinal plantsOrnamentalsPrevent erosion

85% of weeds are introduced intentionally

Why can’t we reduce introductions?

Economic conflictsInternational trade imposes pressure to import plants

Weak RegulationsIf not 100% certain it will be a problem it is difficult to stopUS - only restricts import of KNOWN invasive weeds

Management options

Number of non-natives = Number introduced X survival rate

OptionsPrevent entry

Improve control and eradication

Requires Stronger regulatory framework

Early detection rapid response and $$$

Management priorities for control and eradication

Based on risk (potential impact)

Eradication

The removal of a species from an area to which it will not return

When is it possible?

Population smallHabitat definedMoney and side effects no consideration

Eradication of Norway rats from Langara Island, BC

Kaiser et al 1997

ProblemRats implicated in seabird population declines4 spp had disappearedFeasibilityIslandSpecific poison availableFinanceOil spill $$$

Eradication of Norway rats from Langara Island, BC

Langara Island 3100 ha

Traps set on 100mx100m grid

Trapping started 10 Jul 1995

Last rat Sept 1995

Why was eradication successful?

effective poisonislandterritoriality of rats rat population already stressed

Ancient murrelets - have not recovered---> Heather Major (SFU) - new study

What happened to the seabirds?

Eradications

Work only in specific cases

Successful programs are often on small islands

exotics removed: rats, cats, rabbits possum, goats, pigs

Can have unexpected side effectsrelease of other exotics

Biological Control

the introduction of native enemies (predators, parasites, herbivores) to control an exotic species

NATIVE EXOTIC CONTROLLED

Steps in Biological Control

1. Is the invasive an ecological or economic problem?

If yes -------> 2

2. Is there sufficient support to initiate a biological control program

If yes -------> 3

3. Understand basic biologyidentify weed, examine distributionidentify natural enemies continue

Steps in Biological Control

4. Identify potential control agents

5. Test specificity of agents

6. Select effective agentsone or many???

Biological control: a case study

Diffuse Knapweed

Pre-1930 Introduced viacontaminated seeds

1940 Penticton, Oyama and Grand Forks

1970 Thompson and Okanagan Valleys

Biological control started in 1972

Biological control of knapweed

What control agents have been introduced?

Total 12 insects and 1 fungusincluding

2 gall flies - Urophora spp2 root boring weevils

SphenopteraCyphocleonus

1 seed head weevilLarinus

Biological control of knapweed

What happens after release of control agents?

Before vs After or Treated vs Baseline

Long term data from White Lake BC -J. Myers

Biological control of knapweed

What happens after release of control agents?

+ Larinus major declines

No Larinus no decline

What about other agents?Low densities and low impact

How many agents are necessary?

Several or one good one?

Denoth et al 2002 - reviews 59 weed biocontrol studies

Biological control: case study 2

Purple loosestrifeDisplaces native plants

Slows water flow

Degrades wildlife habitat

Biological control of loosestrife

Plant biomass% foliage removed

Denoth and Myers 2005

Biological controlCase study 3The glassy-winged shooter

Feeds on xylem from 250+ plant spp

Eats 1-X body wt in liquids per hour

Biological controlCase study 3The glassy-winged shooter

arrived in California in 1980is a novel vector for a pathogen Xylella fastidosathat is costing wine industry millions

and is moving North

What do you do?

What do you do?

What actions and in what order?

Biological control of weeds/pests

“is the only long term solution”

Judy Myers

BUT

Biocontrol can and does go wrong

What can go wrong?Rhynocyllus on nodding thistle in BC Opuntia - Australia

Before AfterRelease of S American moth Cactoblastis

Success---> introduction to Caribbean ----> natural spread to Florida

Will it get to centres of cactus diversity????

Biological control - SUMMARY

Can workMay be only option

BUT involves more exoticsAND can have other effects

Often 1 insect is sufficientNeed to predict which one - HOW?and introduce as few spp as possible to minimise risk