17 Quality of Augmentative Biological

Control Agents: a Historical Perspective and

Lessons Learned from Evaluating

Trichogramma

R.F. Luck and L.D. Forster

Department of Entomology, University of California, Riverside, CA 92521, USA

© CAB International 2003. Quality Control and Production of Biological Control Agents:
Theory and Testing Procedures (ed. J.C. van Lenteren) 231

Abstract

Augmentative biological control involves one or more releases of a natural enemy in an attempt to sup-
press and maintain a pest population at subeconomic densities. The notion of releasing parasitoids aug-
mentatively for pest suppression was initially proposed in the late 1800s. However, its first sustained
use involved the suppression of the citrophilous mealybug, Pseudococcus calceolariaeFernald, a pest of
citrus in southern California, which began sometime between 1913 and 1917. The biological control
agent, the coccinellid Cryptolaemus montrouzieriMulsant, initially introduced as a classical biological
control agent, was unable to survive in sufficient numbers to affect control without augmentation. This
coccinellid is still being used in citrus to suppress mealybug pests and it is still commercially available.
The initial success of this tactic led to an expansion in its use against other pests, beginning with the
most widely used augmentative biological control agents, Trichogrammaspecies. Their use began in the
late 1920s, when S.E. Flanders developed a mass-production system for them. 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 predictability, using Trichogrammaspecies
(Hymenoptera: Trichogrammatidae) as examples. Furthermore, we extend the notion of the quality of a
biological control agent by defining it in terms of the attributes that make an agent successful against a
particular pest under field conditions. We provide several examples in which Trichogrammaspecies are
assessed by using behavioural observations under laboratory conditions, employing a technique first
used by European researchers. However, we frame this evaluation in the context of a parasitoid’s repro-
ductive success, defined in terms of its offspring’s reproductive prospects – that is, the offspring’s char-
acteristics that allow them to maximize their reproduction in the field on the targeted pest. It is this field
reproduction that provides biological control. We suggest that this behavioural approach provides a
means of evaluating the likely prospects for augmentative biological control by a particular agent and
the potential to manipulate the agent and its interaction with its host to enhance its success within an
economic framework.