Table Of ContentSpringer Series in
Experimental Entomology
Thomas A. Miller, Editor
Sampling Methods
in Soybean Entomology
Edited by
M. Kogan and D.C. Herzog
I
Springer-Verlag
New York Heidelberg Berlin
Series editor:
Thomas A. Miller
Department of Entomology
University of California
Riverside, California 92521
USA
Editors of this volume:
Marcos Kogan
Dlinois Natural History Survey and Agricultural Entomology
University of Dlinois
172 Natural Resources Building
Urbana, Dlinois 61801, USA
and
Donald C. Herzog
Department of Entomology and Nematology
University of Florida
Quincy, Florida 32351, USA
With 252 figures.
Library of Congress Cataloging in Publication Data
Main entry under title:
Sampling methods in soybean entomology
(Springer series in experimental entomology)
Includes index.
I. Soybean-Diseases and pests. 2. Arthropod
populations-Measurement. 3. Arthropoda
Biological control. I. Kogan, Marcos.
II. Herzog, Donald C. III. Title. IV. Series.
SB608.S7S25 633'.34'970723 80-22342
All rights reserved.
No part of this book may be translated or reproduced in any fonn without
written permission from Springer-Verlag.
The use of general descriptive names, trade names, trademarks, etc., in this
publication, even if the former are not especially identified, is not to be taken
as a sign that such names, as understood by the Trade Marks and Merchandise
Marks Act, may accordingly be used freely by anyone.
© 1980 by Springer-Verlag New York Inc.
Softcover reprint of the hardcover 1st edition 1980
9 8 7 6 5 432 I
ISBN-13:97S-1-4613-S069-6 e-ISBN-13:97S-1-4612-999S-1
DOl: 10.1007/97S-1-4612-999S-1
Series Preface
Insects as a group occupy a middle ground in the biosphere between bacteria and
viruses at one extreme, amphibians and mammals at the other. The size and gen
eral nature of insects present special problems to the student of entomology. For
example, many commercially available instruments are geared to measure in
grams, while the forces commonly encountered in studying insects are in the mil
ligram range. Therefore, techniques developed in the study of insects or in those
fields concerned with the control of insect pests are often unique.
Methods for measuring things are common to all sciences. Advances sometimes
depend more on how something was done than on what was measured; indeed a
given field often progresses from one technique to another as new methods are
discovered, developed, and modified. Just as often, some of these techniques
fmd their way into the classroom when the problems involved have been suffici
ently ironed out to permit students to master the manipulations in a few labo
ratory periods.
Many specialized techniques are confined to one specific research laboratory.
Although methods may be considered commonplace where they are used, in
another context even the simplest procedures may save considerable time. It is
the purpose of this series (1) to report new developments in methodology, (2) to
reveal sources of groups who have dealt with and solved particular entomological
problems, and (3) to describe experiments which might be applicable for use in
biology laboratory courses.
Thomas A. Miller
Series Editor
Call to Authors
Springer Series in Experimental Entomology will be published in future volumes
as contributed chapters. Subjects will be gathered in specific areas to keep
volumes cohesive.
Correspondence concerning contributions to the series should be communi
cated to:
Thomas A. Miller, Editor
Springer Series in Experimental Entomology
Department of Entomology
University of California
Riverside, California 92521
USA
Foreword
In the field of pest management both researchers and practitioners are constant
ly faced with the need to answer four questions: (1) What kind of pest is it?
(2) How many are there per unit area? (3) How many must there be before
economic injury occurs? (4) What will control the pest? The first three of these
questions should be answered before the fourth is considered. The twenty-eight
chapters in this book, prepared by a group of internationally known scientists,
represent a highly successful effort to bring together in one unique publication
most of what is known about how to fmd an answer for the second and third
questions as regards arthropods associated with soybean.
Application of the information presented herein will greatly aid pest manage
ment specialists in the careful evaluation of pest situations and will most often
result in the decision that no control measures are needed. It is imperative that
control measures be taken only when absolutely necessary. Soybean, a rapidly
expanding crop throughout many countries, is presently attacked by more than
100 species of arthropod pests. Many of these are capable of becoming key pests
if populations of their natural control agents are disrupted by unnecessary appli
cations of chemical pesticides. Elevation of a half dozen or so widely occurring
insect pests of soybean to key pest status, requiring repetitive applications of
broad spectrum chemical pesticides on an annual basis, would be environmental
ly and economically catastrophic.
Development of control procedures based on application of accurate sampling
methods for monitoring populations and establishing economic injury thresholds
will help prevent such a catastrophe. The information presented here makes such
control procedures possible for most of the world's major arthropod pests of
soybean.
x Foreword
Two broad aspects of sampling procedures are considered: highly accurate ab
solute population estimates and less accurate, although still reliable, relative esti
mates of population densities. Absolute population estimates are required for
establishing economic injury levels and for use in basic population studies. Their
establishment is a prerequisite for development of less precise relative population
estimates that are adequate for decision-making by practitioners of pest manage
ment.
A strong feature of this book is a section devoted to sampling methods for
natural control agents. Development and application of integrated control tech
niques require that populations of these agents also be monitored. In many cases
it is as important to have accurate estimates of trends in populations of natural
enemy populations as it is for pest populations. The chapter on methods of
sampling populations of the little studied pests that attack the plant at ground
level and its roots and nodules also helps to fill a long existing need.
Having in one· publication the most up-to-date information available on sam
pling methods for the major arthropod pests of soybean is a significant contri
bution to the literature of agriculture. It is an especially timely and valuable
reference for the rapidly accelerating numbers of scientists concerned with pest
management.
L.D. Newsom
Baton Rouge, Louisiana
Preface
Biological phenomena, whether at the cellular or the ecosystem level of organi
zational hierarchy, are only accessible to investigation through analyses of rela
tively small samples taken from more or less large populations. Biologists operate
on the assumption that observations made on the samples provide representative
estimates of the population so that extrapolations can be made with a reasonable
degree of certainty. This assumption is only valid if the reliability of the infor
mation can be defmed within acceptable statistical limits.
Within the rather stable and predictable environment of an organism's body,
one may assume that analysis of a small sample reflects the status of the rest of
the population, often with better than 99% accuracy. Thus, observations made
on several hundred red blood cells can be safely extrapolated to the remaining
25 trillion (25 x 1012) red blood cells of one person's blood stream. However,
a sample of several hundred msects in a crop field is often insufficient to support
generalizations concerning populations of the same species in other fields or even
in other portions of the same field. Here, the population exists in a nonhomo
geneous environment that is much less stable and, consequently, less predictable.
Sampling arthropod populations is the cornerstone of basic research on agricul
tural ecosystems and the principal tool for building and implementing pest man
agement programs. The dual purpose of sampling, i.e., as a research method for
defming the nature and dynamics of communities in agricultural ecosystems and
as a means for providing information for pest management decisions, is stressed
in almost every chapter in this volume. Morris (R. F. Morris, 1960, Ann. Rev.
Entomol. 5 :253) describes sampling as a combination of art, science, and
drudgery, but he stresses that with the utilization of mathematical procedures
for optimal sample allocation, the sampling process is reduced to the latter two
XII Preface
components. Questions of sample allocation, for the most part, remain unresolved.
However, the development and use of field-tested, sequential sampling plans for
management decision-making and for parameter estimation is a step in the right
direction.
This book is devoted entirely to discussing the methods used in sampling arth
ropod populations in a row crop and to summarizing some of the most common
analytical manipulations of the sampling data that allow entomologists to achieve
in their studies a certain degree of generality with a reasonable degree of reliabili
ty. Dedication of this volume to one crop, the soybean, may be interpreted as a
case study in the methodology for sampling arthropod populations in agricultur
al ecosystems. But the reasons to .d evote an entire volume to sampling methods
in soybean entomology go beyond that. The systematic and intensive study of
the arthropod fauna associated with soybean is a relatively recent development.
Modem soybean entomology has received its greatest impetus since the mid-
1960s because of the dramatic expansion of the soybean industry worldwide and
because of the concurrent increase in interest and support for research in the
various aspects of soybean production, protection, and utilization. To be sure, a
valuable literature existed prior to 1960. Much of that work was both isolated
and intermittent, however, since most of the earlier researchers in the United
States and abroad had professional commitments to crops such as cotton, com,
tobacco, or rice and, thus, could not fully dedicate themselves to the study of
soybean arthropods. During the 60s certain land-grant universities and the U.S.
Department of Agriculture instituted full time research positions in soybean
entomology. As a consequence of this increased research activity in soybean
entomology, the literature in the field has proliferated in the past two decades.
Much of this literature deals with population studies, and because of discrepan
cies in sampling procedures it is difficult to compare data from different authors.
Standardization of sampling procedures is badly needed. Owing to the ascent of
soybean to the largest hectareage harvestable row crop in the United States and
its steady expansion in South America and the Orient, soybean entomology is
likely to remain a very prolific and dynamic field of entomological research in
the foreseeable future, and we feel that publication of this volume is justified at
this time.
This book attempts to offer a clear understanding of a methodology that is
highly vulnerable to individual bias. All too often entomologists enter into a
sampling program blindly, not knowing what or how to sample, what population
or portion of it is being sampled, or how many, what size, or how frequently
samples are to be taken. Sampling programs are often undertaken in which
''favorite'' sampling methods are used. This is easily rationalized on the basis of
"one method captures more individuals per sampling unit than does another,"
or "one is used more widely than the rest." However, the adoption of a sampling
method must be based on something more concrete, namely sampling variance
and cost. We hope that information contained herein will provide a foundation
on which a minimum consensus among research entomologists, extension special
ists, pest managers, scouts, and farm operators will be achieved; we hope this
Preface XIII
will lead to a uniform expression of data collecting and handling. If we succeed
in these objectives, results from various researchers will be more directly compar
able. These comparative data can then be used for broader interpretation of
trends that transcend the limited boundaries of the regions in which the data
were originally generated. This volume represents, to our knowledge, the first
attempt to bring together, under one cover, the techniques and results of studies
on sampling arthropod populations in any crop ecosystem.
An effort has been made to standardize terminology throughout this book. We
may not have been entirely successful, and the reader is asked to forgive possible
discrepancies and to call them to our attention. We have departed from a good
portion of current population ecological literature by accepting Pielou's (and the
statistical ecologists') use of the term "spatial patterns" instead of "population
distributions." Pielou (E. C. Pielou, 1977, Mathematical Ecology, John Wiley &
Sons, New York, 385 p., see p. 117) clearly addressed this terminological question
as follows:
Much confusion exists in the ecological literature because the word
"distribut,ion" is used in both its colloquial and statistical senses, even
sometimes in a single sentence, and without any explanation of the
meaning intended. Colloquially, "distribution" is synonymous with
"arrangement" or "pattern." Statistically, it means the way in which
variate values are apportioned, with different frequencies, in a num
ber of possible classes. In this sense, there is no implied reference to
spatial arrangement; for instance, we may speak of the distribution
of a variate such as tree. height without any thought of the location
of the trees. Thus, to talk of a population of insects, say, as having
"a clumped distribution with a large variance" is nonsense; it is the
insects themselves that are clumped or have a clumped pattern, and
the large variance pertains to the distribution of the variate, the
number of insects per sample unit. To avoid ambiguity in statistical
ecology it is most desirable to use the word distribution in its statis
tical sense only. Then a variate has a distribution, whereas a collection
of organisms has a pattern."
We also used the term "dispersion" as a synonym of "distribution" (in the col
loquial sense) to be consistent with the terminology dermed above. It seems per
fectly acceptable to state that a population is randomly dispersed, even if we are
only measuring one steady state and not the motions that lead to that specific
pattern.
This book is organized into eight major sections. Section I includes (1) descrip
tions of the crop as the substrate from which arthropods are extracted, (2) the
most common sampling procedures in population and in injury estimation, (3)
techniques and basic concepts in sampling theory, and (4) sequential sampling
programs for parameter measurement and for management decisions. The reader
is referred back to this section throughout the entire volume.
Sections II through VIII are devoted to major species or complexes of pests or
natural enemies. Within each of the sections there are from one to five chapters
