9 Comparison of Artificially vs. Naturally

Reared Natural Enemies and Their Potential for

Use in Biological Control

S. Grenier^1 and P. De Clercq^2

(^1) UMR INRA/INSA de Lyon, Biologie Fonctionnelle, Insectes et Interactions, Institut

National des Sciences Appliquées, Bât. Pasteur, 20 av. A. Einstein, 69621 Villeurbanne

Cedex, France;^2 Laboratory of Agrozoology, Department of Crop Protection, Faculty of

Agricultural and Applied Biological Sciences, Ghent University, Coupure Links 653,

B-9000 Ghent, Belgium

Introduction

The main concerns for artificial mass culture
of entomophagous insects, after production
of effective natural enemies at acceptable
cost, are the maintenance of insect quality

and reliable methods for measuring quality.

Relevant and robust quality control pro-

grammes are necessary for mass-produced

natural enemies, particularly if they are

reared on factitious or artificial diets (Sorati

et al., 1996). Cost-effective production of

© CAB International 2003. Quality Control and Production of Biological Control Agents:
Theory and Testing Procedures (ed. J.C. van Lenteren) 115

Abstract

Quality assessment of entomophagous arthropods used in augmentative biological control is one of the
main concerns after their mass production. The quality-testing procedures for natural enemies reared on
artificial diets largely remain to be defined. As a first approach, comparisons of some relevant parameters
between in vivo- and in vitro-reared entomophages are presented in this chapter. Results from experi-
ments with different kinds of diets with or without insect components, developed for parasitoids and
predators, are examined. Morphological traits as well as development and reproduction parameters used
for comparisons between in vivo- and in vitro-grown arthropods are discussed. Morphological characters
include body size and weight and the occurrence of abnormalities. Immature development is assessed by
measuring duration and survival rates of the different stages. Sex ratio and symbiont association, fecun-
dity–fertility and longevity are compared as reproduction parameters. It is important to consider bio-
chemical parameters, such as protein, lipid and carbohydrate content, for quality control. These
parameters may also indicate the deficiency or excess in a particular nutritional component. Behavioural
and genetic parameters are considered as well. The establishment of relationships between certain para-
meters, e.g. between body size and fecundity or longevity, may help in simplifying quality control proce-
dures. The ultimate quality criterion for an artificially reared natural enemy is its capacity to reduce pest
populations, which can be evaluated by measuring the predation efficiency or the parasitization rate
under laboratory or field conditions.