REVIEW
A review of open-field host range testing to evaluate non-
target use by herbivorous biological control candidates
Urs Schaffner
.
Lincoln Smith
.
Massimo Cristofaro
Received: 18 April 2017 / Accepted: 26 February 2018 / Published online: 5 March 2018
Ó International Organization for Biological Control (IOBC) 2018
Abstract One of the fundamental challenges of pre-
release studies in classical biological weed control is
to assess and predict the likelihood and consequences
of non-target effects. Unless a candidate biological
control agent is proven to be monophagous through
conventional starvation and host-specificity tests in
quarantine, open-field host range studies can be
important in predicting the likelihood of non-target
effects since they reveal the host selection of herbi-
vores displaying the whole array of pre- and post-
alightment behaviours. Over the course of its 53-year
history, the purpose and the design of open-field host
range studies have changed considerably, with more
recent studies clarifying or refining specific questions
related to one or a few test plant species and using a set
design. We discuss the opportunities and challenges of
this approach and suggest that future open-field host
range studies should be more hypothesis-driven and
apply different experimental designs that facilitate the
interpretation of the results.
Keywords Weed biological control Á Host
specificity Á Risk assessment
Introduction
Classical biological control, i.e. the use of specialist
natural enemies from the weed’s native range to
reduce its abundance or spread in the introduced
range, is an effective and cost-efficient approach to
control invasive alien plant species (Culliney 2005;
Page and Lacey 2006; Winston et al. 2014). A
biological control program is a long-term action which
includes four main steps: surveys and identification of
natural enemies of the target weed, assessment of the
host range (i.e. specificity tests) and impact of
candidate biological control agents, petitioning for
field releases of biological control agents, followed by
an independent decision made by regulatory bodies on
the merits of the petition, and then the release of the
Handling Editors: Mark Schwarzla
¨
nder, Cliff Moran and S.
Raghu
Electronic supplementary material The online version of
this article (https://doi.org/10.1007/s10526-018-9875-7) con-
tains supplementary material, which is available to authorized
users.
U. Schaffner (&)
CABI, Rue Des Grillons 1, 2800 Dele
´
mont, Switzerland
e-mail: u.schaffner@cabi.org
L. Smith
USDA-ARS European Biological Control Laboratory,
34980 Montferrier-Sur-Lez, France
M. Cristofaro
BBCA Onlus, Via A. Signorelli 105, 00123 Rome, Italy
M. Cristofaro
ENEA Casaccia, Via Anguillarese 301, 00123 Rome,
Italy
123
BioControl (2018) 63:405–416
https://doi.org/10.1007/s10526-018-9875-7
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