Pests Plagues & Politics

Lecture 14

Biological Control

Controlling “Pest” InsectsLetLet’’s Go s Go Green

Key points: Biological Control

•Describe two key arthropod classes of biocontrol agents•What are the constraints of biological control•What are the advantages of biocontrol•Give other non-insect biocontrol agents

The biggest enemy of an insect is another INSECT!!

Bio-control is the use of a pest insect’s natural insect enemies for its control.

Bugs eat BugsBugs eat Bugs1) As direct 1) As direct predators*predators*

2) As 2) As parasitesparasites & & parasitoids*parasitoids*

Predators:

Ladybird adult

Ladybird larva

Both are excellent predators

Photo’s: Ken Gray photo collection, OSU

Asian weaver ant

One of the earliest known insects as biocontrol agents

http://en.wikipedia.org/wiki/Weaver_ant

Mike Burgett

Predation: A true Predation: A true bug, bug, lunching onlunching onanother true buganother true bug.

Photo’s: Ken Gray photo collection, OSU

Parasitoids: A fly Parasitoids: A fly parasitoidparasitoid larva larva emerging from the emerging from the host larva.host larva.

A carpenter beegiving you the once-over

A carpenter bee larva that hasbeen parasitized by a wasp.

Mike Burgett

Polyembryony has taken place

and the bee larva containsmany thousands of wasp

larva

Mike Burgett

Biological Control – Advantages*Biological Control – Advantages*

• Self-perpetuatingSelf-perpetuating• Pest specificPest specific• Density dependentDensity dependent• Cost effectiveCost effective• Environmentally compatibleEnvironmentally compatible

Biological Control – Constraints*Biological Control – Constraints*

• Not immediately effective (may take years)• Not eradicative (is this really a constraint?)• Biocontrol agents unknown for many pest

species. • Doesn’t always work

– Historically only one out of four attempts has been successful

What makes an effective biocontrol “agent”??

• High to complete prey specificity• Multivoltine with respect to target

species• Well adapted to habitat of target species• Excellent searching ability

Lacewingimmatureat “lunch”

Photo’s: Ken Gray photo collection, OSU

Classic Biological ControlClassic Biological Control“Control of an Exotic insect pest by the

introduction of its natural enemies”• foreign exploration• quarantine processing• mass propagation• field colonization (release)• evaluation of impact

100 successes in the past 100 years!!100 successes in the past 100 years!!

Tyria jacobaeae, Cinnabar moth

Bugs on plants

http://en.wikipedia.org/wiki/Cinnabar_moth

Bright colors of larvae/adults warning sign

Tansy ragwort flea beetle. Prevents plants from flowering through feeding. Introduced in USA in 1969

Preventing predation and enhancing biocontrol

http://en.wikipedia.org/wiki/Cinnabar_moth

http://ucce.ucdavis.edu/files/repositoryfiles/ca2404p12-63742.pdf

In addition to Classic Biocontrol (bug vs. In addition to Classic Biocontrol (bug vs. bug), we also use*:bug), we also use*:

• Insect Pathogens– VirusesViruses - Japanese Beetle Milky Disease,

Nuclear Polyhedrosis Virus– BacteriaBacteria - the classic Bacillus thuringiensis– MicrosporidiansMicrosporidians - against grasshoppers– EntomopathogenicEntomopathogenic fungifungi– Entomopathogenic nematodesEntomopathogenic nematodes

Japanese beetle

Bacillus popilaehttp://www.biconet.com/biocontrol/bpopillae.html

http://www.hort.uconn.edu/ipm/homegrnd/htms/wgrbpics.htm

Moth larva infected with a Polyhedrosis virusMoth larva infected with a Polyhedrosis virus

I donI don’’ttfeel so feel so good.good.

http://www.monarchlab.org/lab/research/topics/Enemies/Default.aspx

Key points on Biological Control

•Describe two key arthropod classes of biocontrol agents

•What are the constraints of biological control

•What are the advantages of biocontrol

•Give other non-insect biocontrol agents

Another true bug munchingon an aphid. - A directpredator.

A “mule killer” - a winglessparasitoid wasp - alsoknown as velvet ants.

ByeBye

Photo’s: Ken Gray photo collection, OSU

Key points: Biological Control

•Describe two key arthropod classes of biocontrol agents•What are the constraints of biological control•What are the advantages of biocontrol•Give other non-insect biocontrol agents