The Princeton Guide to Ecology

By Simon A. Levin | Go to book overview

VII.1
Biological Control:
Theory and Practice
William Murdoch
OUTLINE
1. Settings and protagonists
2. Locally persistent pest–enemy interactions
3. Locally nonpersistent systems
4. Ecological theory and biological control

Biological control—defined here as the suppression of insect pests by other insects that attack them—has been pursued by entomologists for more than a century, in part because it is typically cheap and can yield very large economic returns on investment. Over this period, the empirical record is one of often spectacular successes mixed with rather more failures. It is also a history of trial and error. In an extreme example, entomologists introduced about 50 species of enemy insects before achieving great success in controlling California red scale on citrus, a case discussed below. Such applied population dynamics has naturally attracted the interest of ecologists who, together with many of the entomologists themselves, have worked to develop theory that would explain the essential features underlying success. This theory and its connection to real biological control comprise the subjects of this chapter. The theory’s domain, however, is much broader—it is the dynamics of interacting resource populations and the consumer populations that attack them.


GLOSSARY

consumer–resource interactions. These include interactions between populations of predators and prey, parasitoids and hosts, indeed any interaction in which one species depends on another for sustenance. These terms are used interchangeably here.

density-dependent processes. These cause the per-head rate of increase of the population to decrease when the population’s density increases.

equilibrium. Density at which the population will remain, once it is reached, if the population is not perturbed.

parasitoid. An insect that parasitizes another insect (the host species) by laying egg(s) in or on the host, which is eaten by the immature parasitoid.

scale insects. Plant-sucking bugs that stay attached to the plant for almost their entire life history.

stable equilibrium. An equilibrium is stable when the population tends to return to it after the population is perturbed.

unstable equilibrium. The population moves away from the equilibrium following a perturbation. The result may be cycles in abundance, extinction, or chaos, in which the densities are always bounded, but there are no repeated sequences of abundance.


1. SETTINGS AND PROTAGONISTS

It is useful to distinguish two settings in which biological control occurs. First, most successful biological control has occurred in relatively long-lived agricultural systems such as orchards and, less successfully, forests. It is known for at least some cases that the pest and enemy populations persist together at a small spatial scale such as a single orchard. This is the kind of dynamics for which the bulk of ecological consumer– resource theory has been developed.

In the majority of successes in this class, the pest is an alien species as, almost always, is its successful enemy. Typically, the entomologist faced with an introduced pest travels to its place of origin, searches for enemy species in that environment and, after some preliminary laboratory work, releases the enemy, which usually confines its attacks to the pest species—it is effectively a specialist in the introduced agricultural

-683-

Notes for this page

Add a new note
If you are trying to select text to create highlights or citations, remember that you must now click or tap on the first word, and then click or tap on the last word.
One moment ...
Default project is now your active project.
Project items

Items saved from this book

This book has been saved
Highlights (0)
Some of your highlights are legacy items.

Highlights saved before July 30, 2012 will not be displayed on their respective source pages.

You can easily re-create the highlights by opening the book page or article, selecting the text, and clicking “Highlight.”

Citations (0)
Some of your citations are legacy items.

Any citation created before July 30, 2012 will labeled as a “Cited page.” New citations will be saved as cited passages, pages or articles.

We also added the ability to view new citations from your projects or the book or article where you created them.

Notes (0)
Bookmarks (0)

You have no saved items from this book

Project items include:
  • Saved book/article
  • Highlights
  • Quotes/citations
  • Notes
  • Bookmarks
Notes
Cite this page

Cited page

Style
Citations are available only to our active members.
Sign up now to cite pages or passages in MLA, APA and Chicago citation styles.

(Einhorn, 1992, p. 25)

(Einhorn 25)

1

1. Lois J. Einhorn, Abraham Lincoln, the Orator: Penetrating the Lincoln Legend (Westport, CT: Greenwood Press, 1992), 25, http://www.questia.com/read/27419298.

Cited page

Bookmark this page
The Princeton Guide to Ecology
Table of contents

Table of contents

Settings

Settings

Typeface
Text size Smaller Larger Reset View mode
Search within

Search within this book

Look up

Look up a word

  • Dictionary
  • Thesaurus
Please submit a word or phrase above.
Print this page

Print this page

Why can't I print more than one page at a time?

Full screen
/ 810

matching results for page

Cited passage

Style
Citations are available only to our active members.
Sign up now to cite pages or passages in MLA, APA and Chicago citation styles.

"Portraying himself as an honest, ordinary person helped Lincoln identify with his audiences." (Einhorn, 1992, p. 25).

"Portraying himself as an honest, ordinary person helped Lincoln identify with his audiences." (Einhorn 25)

"Portraying himself as an honest, ordinary person helped Lincoln identify with his audiences."1

1. Lois J. Einhorn, Abraham Lincoln, the Orator: Penetrating the Lincoln Legend (Westport, CT: Greenwood Press, 1992), 25, http://www.questia.com/read/27419298.

Cited passage

Thanks for trying Questia!

Please continue trying out our research tools, but please note, full functionality is available only to our active members.

Your work will be lost once you leave this Web page.

For full access in an ad-free environment, sign up now for a FREE, 1-day trial.

Already a member? Log in now.