st. john’s wort beetles would not have been introduced to nz today!

St. John’s wort beetles would not have been

introduced to NZ today!

Ronny Groenteman, Simon Fowler & Jon Sullivan

St. John’s Who???

St. John’s wort Hypericum perforatum

• Introduced as medicinal herb• Severe pasture weed by 1930s• Toxic to live stock

• Programme started 1943• Most successful BC programme

BC agent removal trialInsecticide

Water

St. John’s wort biocontrol

• Why invest funds in an old successful programme???

• Post-release studies are pivotal to advance BC practice:– Safety– Effectiveness– Economics

Objectives

• Compare host-tests predictions to real world

• Demonstrate significance of BC agents

• Implications for future programmes

Retrospective host-range tests

• Indigenous species not included in original tests

• 4 indigenous species– 2 endemic– 1 critically threatened

H. involutumNZAustralia

H. rubicundulum

NZ endemic

H. pusillumNZAustralia

We asked:

Would we have introduced St. John’s wort beetles

today?

Methods

• Laboratory host range testing• No-choice / choice arenas• Feeding • Development• Oviposition

Results

H. perforatum H. involutum H. pusillum

Day

s to

end

of l

arva

l sta

ge

0

10

20

30

40

50

60

H. perforatum H. involutum H. pusillum

% c

ompl

eted

dev

elop

men

t

0

20

40

60

80

100 C. hypericiC. quadrigemina

H. perforatum H. involutum H. pusillum H. rubicundulum H. androsaemum

Eggs

per

pla

nt

0

5

10

15

20

25

30

35

Groenteman et al., 2011. Biological Control

Larval development

H. perforatum H. involutum H. androsaemum

H. rubicundulum H. pusillum

In reality…

• Little evidence of damage to indigenous species

• Significant displacement? Yet to be determined

• Benefits of control - enormous

• Recent review of successful programmes in N. America concluded: –St. John’s wort beetles would not have

been introduced nowadays

–More stringent regulations / interpretation of old regulations

–Monitoring crucial for data-driven benefit-risk decisions

Global context

Implications

• Risk rejecting effective & safe agents

• Control goals?

• Implications of failure to control?

USDA ARS - European Biological Control Laboratory, Bugwood.org

St. John’s wort beetles success