5)Management c)Control iii)Biological methods = “biologically” damaging plants.

5) Managementc) Control

iii) Biological methods= “biologically” damaging plants


iii) Biological methods= “biologically” damaging plantsBiotic constraints/enemy release hypothesis


iii) Biological methods= “biologically” damaging plantsBiotic constraints/enemy release hypothesis

If plants are invasive because they have escaped natural enemies, introducing the natural enemies should help control the invasive!


iii) Biological methods• Least public opposition


iii) Biological methods• Least public opposition• Recall Federal Plant Protection Act :

Biological control is often desirable


iii) Biological methods• Least public opposition• Recall Nevada noxious weed legislation:

• Weed control analyst researches biological control options


iii) Biological methods• Least public opposition• Number of success stories

Prickly pear (Opuntia spp.) in Australia

W. Wagner@USDA-NRCS Plants Database



Prickly pear (Opuntia spp.) in Australia Chronology (source: http://www.northwestweeds.nsw.gov.au )

W. Wagner@USDA-NRCS Plants Database

http://www.northwestweeds.nsw.gov.au/




Prickly pear (Opuntia spp.) in Australia Chronology (source: http://www.northwestweeds.nsw.gov.au )• Introduced in 1788 with the First Fleet – dye industry• Additional introductions for forage and hedges though 1800s• Numerous species• Problem acknowledged 1870 W. Wagner@USDA-NRCS Plants Database





Prickly pear (Opuntia spp.) in Australia Chronology (source: http://www.northwestweeds.nsw.gov.au )• Introduced in 1788 with the First Fleet – dye industry• Additional introductions for forage and hedges though 1800s• Numerous species• Problem acknowledged 1870• 1886: prickly pear destruction act• 1910: ‘Roberts Improved Pear Poison’ created – 80% sulfuric

acid, 20% arsenic – considered best weapon





Prickly pear (Opuntia spp.) in Australia Chronology (source: http://www.northwestweeds.nsw.gov.au )• Early chemical control: fumes from boiling arsenic

Photo: © L. R. Tanner





Prickly pear (Opuntia spp.) in Australia Chronology (source: http://www.northwestweeds.nsw.gov.au )• Early chemical control: boiling arsenic• 1912 problem rampant: begin looking for biological control



Prickly pear (Opuntia spp.) in Australia Chronology (source: http://www.northwestweeds.nsw.gov.au )• Early chemical control: boiling arsenic• 1912 problem rampant: begin looking for biological control• 1925, infested twenty-five million hectares in New South Wales

and Queensland. It was spreading at the rate of half a million hectares a year.



Prickly pear (Opuntia spp.) in Australia Chronology (source: http://www.northwestweeds.nsw.gov.au )• 1926 introduction of Cactoblastis moth




Prickly pear (Opuntia spp.) in Australia Chronology (source: http://www.northwestweeds.nsw.gov.au )• 1926 introduction of Cactoblastis moth• By 1932, most of the prickly pear stands had been decimated.




Prickly pear (Opuntia spp.) in Australia Chronology (source: http://www.northwestweeds.nsw.gov.au )• 1926 introduction of Cactoblastis moth• By 1932, most of the prickly pear stands had been decimated




Prickly pear (Opuntia spp.) in Australia • Summary: spectacularly successful BUT

• Took 14 years to find biocontrol agent (1912-1926)• Some cool-climate stands remained; insect less effective



Prickly pear (Opuntia spp.) in Australia • Summary: spectacularly successful BUT

• Took 14 years to find biocontrol agent (1912-1926)• Some cool-climate stands remained; insect less effective• Opuntia aurantica becomes more problematic 1930-1950


iii) Biological methods• Least public opposition• Number of success stories• Klamath weed (Hypericum perforatum) in California


iii) Biological methods• Least public opposition• Number of success stories• Klamath weed (Hypericum perforatum) in California

• Broad-leaved, perennial herb• Introduced from Europe in 1793; reached California late 1800’s• Extremely invasive; toxic• By early 1940’s: 5 million acres of infested rangeland• Biological control in California: 1945-1950 @ $750,000 total

cost• By early 1960’s insects had reduced acreage to <1% of peak


iii) Biological methods• Least public opposition• Number of success stories• Tamarix in western US:

Photos: Bob Conrad, NAES


iii) Biological methods• Least public opposition• Number of success stories• Tamarix in western US:

• SourceL Swedhin et al. 2006 (Tamarisk Research Conference, Fort Collins CO)

• Large scale dispersal and population expansion of Diorhabda elongata in CO, NV, and UT after initial releases

• Near Moab: two release sites in 2004. In 2005, less than 2 acres of tamarisk defoliated. In 2006, 109 acres defoliated, 4.1 miles upstream from release sites and area was expanding

• Expansion of beetles from UT release sites on Colorado River into CO expected by summer 2007


iii) Biological methods• Least public opposition• Number of success stories• Considerations:



• Finding an enemy



• Finding an enemy• ID promising species in native range• Test for host specificity• USDA has facilities in other countries for this purpose• http://www.ars-ebcl.org/



• Finding an enemy• ID promising species in native range• Test for host specificity• USDA has facilities in other countries for this purpose• http://www.ars-ebcl.org/• e.g. Montpelier, France

Photo © USDA ARS-EBCL

Current projects:Canada Thistle, Field Bindweed Giant reed, Knapweeds, Leafy Spurge, Lepidium draba, Rush Skeletonweed, Saltcedar, Swallow-worts, Yellow Starthistle



• Finding an enemy• ID promising species in native range• Test for host specificity• USDA has facilities in other countries for this purpose• http://www.ars-ebcl.org/• e.g. Montpelier, France• Also Rome, Italy and Thessaloniki, Greece

Photos © USDA ARS-EBCL



• Finding an enemy• Host specificity: specialists not generalists



• Finding an enemy• Host specificity• Mode of action (plant part affected)



• Finding an enemy• Host specificity• Mode of action (plant part affected)• Type of organism (disease, insect)



• Finding an enemy• Host specificity• Mode of action (plant part affected)• Type of organism (disease, insect)• Climate requirements of organism (climate matching

for source populations and introduction sites)• e.g. some releases of Diorhabda from Texas

populations not successful at higher latitudes – couldn’t overwinter



• Finding an enemy• Host specificity• Mode of action (plant part affected)• Type of organism (disease, insect)• Climate requirements of organism (climate matching for

source populations and introduction sites)• Estimated that about ½ of introduced weed bio-control

insect species establish in new location



• Finding an enemy• Non-target effects



• Finding an enemy• Non-target effects

• Specificity of biocontrol agent• Relatedness of flora



• Non-target effects – Pemberton (2000)



• Non-target effects


iii) Biological methods• Least public opposition• Number of success stories• Considerations



iii) Biological methods• Least public opposition• Number of success stories• Difficulty locating enemy• Non-target effects – From Pemberton (2000)


iii) Biological methods• Least public opposition• Number of success stories• Considerations



iii) Biological methods• Least public opposition• Number of success stories• Difficulty locating enemy• Non-target effects

Most likely a problem when the invasive species has closely related plants in the invaded area

5)Management c)Control iii)Biological methods = “biologically” damaging plants.

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