Natural Enemies: An
Introduction to Biological Control
Ann
Hajek, ed.
Press Syndicate of the University of Cambridge
Cambridge, UK
2004, 378 pp.
Hardback $110.00, Paperback $50.00
Hardback ISBN 0-521-65295-2, Paperback ISBN 0-521-65385-1
It is
difficult studying insects, with millions of species and their
associated behaviors, physiology, genetics, and ecological impacts.
On top of all of that, if one is interested in managing insect pests
with natural enemies, the taxa studied expands to cover almost the
entire tree of life. This is no trivial task for instructors needing
to describe the animals, fungi, and unicellular organisms that are
used within pest management programs that target insects and weeds.
Thankfully, Ann Hajek has taken on the entire natural enemy
community and summarized it in Natural Enemies: An Introduction
to Biological Control. This is a remarkable textbook given that
she has left no member of this community out: from vertebrates to
pathogens. The text is written in a very accessible language
appropriate for students whose primary focus may not be entomology
or biological control. For entomology students and students studying
pest management, this will be an excellent introduction to the use
of natural enemies in agricultural and natural area settings. For
this latter group of students, Hajek provides a great service by
compiling the details and examples of noninsect natural enemies
(nematodes, fungi, and viruses) that are not familiar to
entomologists (at least this entomologist).
The
book is divided into five sections that starts with a brief
introduction to biological control and focuses on the type of pests
attacked by natural enemies. The sections pertain to (1) strategies
for using natural enemies, (2) biological control of invertebrates
and vertebrate pests, (3) biological control of weeds, (4)
biological control of plant pathogens and plant parasitic nematodes,
and (5) biological control: concerns, changes, and challenges. The
theory behind each of the three basic biological control strategies
(classical, augmentation, and conservation) is described in the
second section. These three strategies provide an applied framework
in the subsequent sections when describing the use of each natural
enemy taxa. I found this very useful, grounding this textbook within
an applied context. However, this is not just a handbook for pest
management, because the theoretical basis for biological control is
discussed within a single chapter (Chapter 6: Ecological Basis for
Use of Predators, Parasitoids, and Pathogens). Also, interspersed
throughout the text are references to ecological niches, population
regulation, and host feeding preferences. Although these are not
comprehensive, they provide a gateway into the primary literature
for undergraduate students. As an instructor of an undergraduate
course in pest management, I will refer to this textbook often,
particularly for the last three sections. General biology with case
examples are provided for each natural enemy taxa as it applies to
various pests. I am very impressed by the quantity and quality of
examples, their global scope, and the accounts of their efficacy and
cost effectiveness.
In
addition to a readable text, there are components that make this an
accessible textbook for new students of pest management and
biological control. Throughout the chapters are stand-alone boxes
featuring personalities and case studies that highlight selected
concepts. The mini-biographies (Rachel Carson, Albert Koebele,
Edward Steinhaus, and others) place the biology within a personal
and historical context. These boxes have me excited to recommend
this text to students of social sciences interested in pest
management. The author also does an excellent job of describing the
implementation of biological control, with opportunities for
students to discover the influential role that government policies
have on pest management strategies. As the author points out,
conservation biological control is the least studied of the three
main strategies of biological control. Not surprisingly, it has the
fewest examples in the text. The potential for conservation
biological control is described, but this follows a discussion on
the lack of "truly efficacious strategies." It is interesting to
note that the author offers three case studies in which government
policies have been critical for the adoption of biological control:
(1) augmentative biological control in Danish greenhouses (Box
19.3), (2) conservation of natural enemies for rice integrated pest
management in Indonesia, and (3) the use of "beetle banks" in Europe
as a means of conservation biological control (Box 5.2). Each of
these examples is a viable method of pest management that involves
conservation that was encouraged with some degree of government
intervention. Conserving existing natural enemies may not provide
the most efficacious method for controlling a pest, but as pointed
out by Hajek in her final chapter, "stand alone" pest management
programs may not be sustainable. Conservation methods can have
additional benefits for the agroecosystem, which in aggregate may
provide greater value than a single "stand alone" pest management
program. Therefore, conservation biological control may be more
appropriate for constructing such a multi-functional agroecosystem.
Granted, this begins a very broad discussion—maybe one beyond the
scope of this textbook—but it is one that highlights how
governmental policy can influence the application and perception of
pest management science.
The
fifth and final section includes a chapter (Chapter 18: Safe
Biological Control) devoted to nontarget impacts. Case studies
include the report of Rhinocyllus conicus, an imported
biological control agent for invasive thistles, reducing populations
of thistles native to North America. Additional examples are found
throughout, especially in the chapters describing biological control
programs that import exotic natural enemies. There are detailed
passages describing how nontarget studies should be constructed, as
well as fairly frank explanations for why these nontarget impacts
have occurred. The author has provided a fair and balanced approach
to describing the cost and benefits of biological control.
I
would recommend this textbook for courses that cover the topic of
natural enemies and, more generally, biological control. Given the
substantial amount of information covered for each natural enemy
group, it is a bit unfair to be critical of any deficiencies.
Although subheaded as an introduction to biological control, one may
want to supplement the theoretical chapters or at least combine the
ecological topics that are discussed throughout the text with
additional material. For example, the concept of r- and K-selected
species is brought up multiple times for different types of pests
(i.e., weeds and plant pathogens). I would have preferred that r-K
selection theory be explained in more detail within Chapter 6.
Granted, there are limitations to the explanatory power of r-K
selection theory (Gotelli 2001). However, given that this text is
targeting undergraduates, the comparison of these idealized life
history strategies can be a powerful learning tool for understanding
the success of pest species and the constraints of the natural
enemies that manage them.
Courses that feature biological control within a broader context of
sustainable agriculture will also benefit from this textbook. It is
challenging to appropriately describe to students from a wide
variety of backgrounds the use of natural enemies, summarize
multiple reviews of biological control successes and failures, and
give examples of commercially available natural enemies. This Swiss
army knife of a textbook covers all of these topics making it a
valuable resource.
References
Gotelli N. J. 2001.
A primer of ecology. Sunderland, MA, Sinauer
Matthew O'Neal
Department of Entomology
Iowa State University
Ames, Iowa
Environmental Entomology
Vol. 36, No. 3, June 2007
