Introduction
Augmentative biological control utilizes one
to several releases of a natural enemy to sup-
press a pest during the course of a season or
a crop’s production cycle. Permanent estab-
lishment with consistent pest suppression in
the absence of augmentation is not its aim.
Frequently, augmentative releases are an out-
growth of an unsuccessful or partially suc-
cessful effort to establish a natural enemy
permanently, i.e. a classical biological control
programme (Smith and Armitage, 1931;
Flanders, 1949). Under such circumstances,
augmentative releases are meant to supple-
ment an established complex of endemic
and/or exotic natural-enemy populations
during critical periods when the natural-
enemy complex is incapable of suppressing
the pest consistently on its own.
Augmentative biological control is one tactic
in a pest-management strategy that seeks
sustainability in the management of a pest
complex (e.g. Rabb et al., 1976; Flint and van
den Bosch, 1981; Haney et al., 1992; Trumble
and Morse, 1993; Luck et al., 1997).
The notion of periodically releasing nat-
ural enemies was first suggested by F. Enock
(1895) at a meeting of the London
Entomological and Natural History Society.
He suggested the possibility of ‘farming’
Trichogramma. Flanders (1949) also credits
Felix Gillet, the Horticulture Commissioner
of California, with a similar notion. In an
1882 meeting in El Dorado, California, the
Horticultural Commissioner stated that: ‘it is
surprising [given all the money spent to fight
noxious insects that we] have never tried to
raise ichneumon flies by the million and let
them loose wherever there are any insect
pests to destroy’. Also, Decaux (1899)
employed natural-enemy releases as part of
an integrated-control tactic for fruit pests in
France. Finally, Kot (1964, p. 278) cites
Radeckij as initiating experiments in 1911 on
rearing and introducing Trichogramma
evanescensWestwood for the control of Cydia
pomonella (L.) (Lepidoptera: Tortiricidae).
Radeckij collected the parasitoid from
Astrakhan province in Turkistan and intro-
duced it into Turkistani apple orchards.
The first extensive and sustained augmen-
tative biological control effort against a pest
or group of pests, however, involved the mass
production of a ladybird, Cryptolaemus mon-
trouzieriMulsant (Coccinellidae: Coleoptera),
to suppress a complex of mealybugs
(Homoptera: Pseudococcidae) in southern
California citrus. In this chapter, we first
summarize this historical origin and then
illustrate the role of fundamental research
and its interaction with theory in improving
augmentative biological control’s predictabil-
ity, using Trichogramma species (Hymeno-
ptera: Trichogrammatidae) as examples.The Early Evolution of Augmentative
Biological Control
An early introduction of an exotic pest and its
augmentative controlThe first sustained augmentative biological
control project began before 1917 and
involved the citrophilous mealybug,
Pseudococcus calceolariae Fernald (= gahani
Green), a pest of citrus in southern California.
It had appeared in California’s citrus groves
around 1913 and spread throughout the
coastal areas of southern California, causing
substantial damage to citrus (Smith and
Armitrage, 1920; Quayle, 1938). The available
control method, hydrogen cyanide fumiga-
tion, which was used to control soft scales
(Homoptera: Coccidae) and armoured scales
(Homoptera: Diaspididae), was ineffective in
controlling the mealybug (Quayle, 1938).
Earlier, foreign exploration for natural ene-
mies of mealybugs in general had discovered
a ladybird, the mealybug destroyer, in
Australia. It had been imported and released
in California’s citrus groves in 1892, and
again in 1909, for suppression of a variety of
mealybugs, including the citrus mealybug,
Planococcus citri (Russo), the obscure or
Baker’s mealybug, Pseudococcus obscurus
Essig (= maritimus(Ehr.)), and the long-tailed
mealybug, Pseudococcus longispinus(Targioni-
Tozzetti), all of which were present in
California prior to the citrophilous mealy-
bug’s discovery. However, C. montrouzieri
was unable to survive the cool winter tem-232 R.F. Luck and L.D. Forster