10 Pathogens of Mass-produced Natural

Enemies and Pollinators

S. Bjørnson^1 and C. Schütte^2

(^1) Department of Biology, Saint Mary’s University, 923 Robie Street, Halifax, Nova

Scotia, Canada B3H 3C3;^2 Laboratory of Entomology, Wageningen Agricultural

University, PO Box 8031, 6700 EH Wageningen, The Netherlands

Introduction

About 125 natural enemies are reared for
inundative and seasonal inoculative forms of
biological control (Chapters 1 and 11; van
Lenteren et al., 1997). Several species are
used throughout the world. The success of a
biological control programme is dependent
on many factors, including the quality of the
beneficial arthropods that are used. In sev-
eral cases, reports of pathogens in mass-
reared natural enemies have raised questions
regarding their quality and efficacy.
Pathogens have been reported in natural
enemies collected from the field (Lipa et al.,
1975; Geden et al., 1995), from those currently

mass-produced for biological pest control

(Beerling and van der Geest, 1991; Becnel

and Geden, 1994; Bjørnson and Keddie,

2000) and from those being evaluated for

their potential as biological control agents

(Kluge and Caldwell, 1992). The origin of

many of these pathogens has not been

demonstrated and it is therefore difficult to

determine if pathogens originate from field-

collected natural enemies or arise in mass-

rearing systems as a result of intense and

continuous rearing under laboratory condi-

tions. Temporary starvation and localized

overcrowding are often unavoidable in

mass-rearings and these conditions place

stresses on individuals, presumably making

© CAB International 2003. Quality Control and Production of Biological Control Agents:
Theory and Testing Procedures (ed. J.C. van Lenteren) 133

Abstract

Pathogens are found in both field-collected and mass-reared natural enemies. This raises concern regard-
ing their quality and efficacy in biological pest-control programmes. Some pathogens affect the perfor-
mance of natural enemies and crop pollinators by lowering their efficacy, whereas others alter their
reproduction. It is therefore important to screen individuals for pathogens on a routine and continual
basis. Special attention should be given to field-collected arthropods and those exchanged among rearing
facilities. In order to obtain high efficacy in pest control, the release of pathogen-free natural enemies in
biological control programmes is of the utmost importance. This chapter first provides an overview of
the types of pathogens to which beneficial arthropods are susceptible and describes the symptoms that
may be associated with infection. Next, diseases of natural enemies and insect pollinators are presented
according to host genus.