The Next Rung Up the Integrated Pest Management Ladder
1
L. D. NEWSOM
Dept. or Entomo!., Agric. Exp. Sta., Louisiana State Univ., Baton Rouge 70803
Professor Dwight Isely richly deserves to be
called the father of integrated insect control. More
than 50 years ago he developed a system for control
of the boll weevil, A ntllonolnus grandis that, both
strategically and tactically, is essentially the eQuivalent of the most effective systems in use today. It
was founded on good understanding of the biology
and ecology of the boll weevil and growth and development of the cotton plant. The system consisted of the following:
I. Planting early maturing, determinate
varieties that allowed a crop to be produced
before emergence of the third, and most
damaging, generation of the boll weevil.
2. "Spot
treating"
overwintered
and first
generation
boll weevils in relatively small
areas of fields where they concentrated year
after year.
3. Destroying favorable hibernation Quarters in
and around fields, especially by controlled
burning.
4. Using economic injury levels determined by
continuous
monitoring
of populations
for
determining applications of insecticides during the remainder of the growing season.
5. Conserving populations of natural enemies of
other cotton pests, especially the bollworm,
Heliolliis zea, and colton aphid, ApI/is gossypii,
by limiting the area treated and numbers and
rate of application to the minimum required
for preventing economic losses.
Professor Isely was keenly aware that the most
eflective and economical system of boll weevil control was useless unless it could be fully implemented. Therefore, he initiated a program of training "cotton scouts," the forerunner of the pest
management
consultant
of today. Dr. James
Horsfall, Director Emeritus, Connecticut Agr. Exp.
Sta. was the first of these. He was located on the C.
E. Yancy and Co. Farm at Marianna, AR during
1926 for the purpose of helping to implement the
Isely boll weevil control system. Because at that
time there was no Cooperative Extension Service in
AR, Dr. Horsfall worked under the supervision of
Professor Isely. His status was essentially that of
the Cooperative
Extension
Service Insect Pest
Management Specialists now employed throughout
the nation for implementing
pest management
programs. Thus, integrated insect control was firmly established on the first rung of the pest management ladder during the I920s.
This system,
developed
by the efforts of
Professor Isely was effective. The "scouting"
©I980 Entomological
Society of America
program developed for monitoring pest populations
has continued in AR until today. Basically, it consists of training college undergraduates
and high
school students to monitor pest populations and
report to the county agent, or other extension specialists who, in consultation with the grower, make
the decisions for implementing control measures. It
was out of this system that professional consultants
for cotton insect control developed. Often, after a
few years of experience, the "scouts" established
private businesses.
Some were employed
by
individual growers, groups of growers, or by
pesticide dealers. Substantial numbers of these prototypes of today's pest management consultants established businesses in AR, LA, and Ml. Many
were inadequately trained and others were almost
exclusively "insecticide peddlers".
Tile "Dark Ages" of Inlegrated
Insect Control
The period from the late 1940s through the mid1960s appropriately
may be considered
as the
"Dark Ages" from the standpoint of further development of integrated insect control. Unfortunately,
during this period, most of the research and extension Entomologists joined "pest management consultants"
in functioning essentially as "pesticide
peddlers."
The basic principles of biology and
ecology were largely forgotten or ignored. Only a
glimmer of the integrated control concepts that
Professor Isely pioneered remained alive.
Ascent 10 tile Second Rung
Control Ladder
of tIle Integrated
Insect
Problems that developed in many crops as a
result of the almost total reliance upon repetitive
applications
of broad spectrum chemicals,
freQuently without regard for population assessment,
do not require recounting here. They forced a
renaissance of research having as its objective the
development
of integrated
insect pest control
systems. This effort has been reasonably successful.
Effective integrated control systems have been developed for a number of insect pests of major crops
during the last decade. Implementation
of these
programs is now receiving major emphasis.
Two momentous changes have occured in the integrated pest control movement during the 1970s.
Both have been strongly influenced by the success
of the" Huffaker Project". 2
I. The concept
has been widely,
if not
altogether
enth usiastically,
accepted
by
369
0013-8574/80/0303-6906$00.75/0
370
ESA BULLETIN
researchers,
extension
specialists,
pest
management
consultants,
the pesticide
industry, growers, administrators, and the
general public.
2. Members of all the "protection" and related
disciplines have begun to work cooperatively
in coordinated team efforts toward the development of truly integrated pest management
systems.
In addition, extension specialists and pest
management consultants better trained in the concepts of integrated pest management have begun to
make an impact. Thus, integrated pest management now seems to be perched on the second rung
of the ladder and is ready to reach for the third
rung.
Progress up the first two rungs of the integrated
pest management ladder has been painfully slow
and tedious. However, the obstacles to further ascent appear to be far more difficult and challenging.
These problems are both technological and socio-economic-political in nature. Both kinds involve
complexes. The latter may be more important and
far more intractable than the former. Because it is
beyond my capability intelligently to discuss problems that are socio-economic-political in nautre,
the following discussion will be concentrated on
those that are technological.
Some major technological constraints to further
progress up the integrated pest management ladder
involve the following kinds of complexes:
I. Pests
2. Pesticides
3. Subject matter disciplines
Because I am most familiar with these complexes
as they relate to soybean, my discussion of them
will deal predominantly with problems of that crop.
Vol. 26 no. 3, 1980
"I don't know." Sufficient data are not available for
establishing ElLs for more than a small percentage
of the pests that affect soybeans, even considered
singly. No ElL is available for any pest complex,
even for simple two-species complexes except for
species that do essentially the same sort of damage.
For example, defoliating species such as the velvetbean caterpillar, An/iearsia
gemma/a/is,
soybean
looper, Pseudop/usia ineludens, and green c1overworm, Pla/l1ypena scabra, are usually considered
together in establishing ElLs as are also the pod
feeding stink bugs Aeros/ernum IIi/are, Eusellis/us
servus, and Nezara viridu/a. Growers are becoming
insistently demanding that we correct this serious
deficiency in information needed for dealing with
insect pest complexes of soybean.
The serious nature of the species complex problem on appple was recently mentioned by Croft and
Hoyt (1978). They stated, "A multiple species control tactic is not yet available for a pest complex
such as the codling moth, the redbanded leafroller,
apple maggot, [Rhago/e//s] pomoneffa Walsh, and
plum curculio, Cono/raellelus nenupllar (Herbst)."
Such control tactics require the establishment of
ElLs for the complex. Tremendous amounts of
research would be required to establish an ElL for
such a comparatively simple complex as they
describe. The amount of research required can
become several orders of magnitude greater in
some crops. Soybean, for example, is affected by a
much larger number of important pest species than
is apple.
Soybean is a relatively new crop in the United
States, especially in the South. Acreage planted to
soybean in 9 southeastern states, where hazard
from all classes of pests-weeds,
insects,
nematodes, bacteria, fungi and viruses-is
much
higher than elsewhere in the country, has increased
from 15 percent in 1955 to 33 percent of the more
than 70 million acres planted in 1979 (Anonymous
1979).
Pest Complexes
My interest in pest complexes began to be stimulated several years ago by questions of the following
kinds posed by growers:
1. If I have present in my crop a foliage feeder, a
stem feeder and a pod feeding species, none
of which has reached the economic injury
threshold (ElL), but all of which have populations at one-half to three-fourths their ElL,
what should I do?
2. If my crop is moderately to heavily affected
by aerial blight, Rllizoctonia so/ani, or frogeye
leafspot, Cercospora sojina, or both, how does
this affect the ElL for defoliating insect
pests?
The only appropriate answer to such questions is,
In LA soybean is under attack from the time the
seed is planted until the crop is harvested. Regularly occurring important species affect substantial
acreages of the crop each year.
In addition to the more than 30 major pests there
are at least as many more that occur less frequently
or that are of more local importance. Reasonahly
satisfactory ElLs have been established for only 8
species. The ElLs that have been established do not
take into account possible interactions with other
species, indirect effects, or even direct effects on
more than one parl of the plant attacked. For example, the ElL established for bean leaf beetle is based
on an estimate of the percentage of defoliation
caused by feeding of the adults, except in a few
states where feeding of the adults on pods is also
considered. However, the important effects of nodule damage by larvae, with the consequent effect of
reducing nitrogen fixation, and transmission of
bean pod mottle mosaic virus by the adult have
Vol. 26 no. 3, 1980
ESA BULLETIN
been ignored in establishing ElLs for the species.
Development
of effective IPC systems require
thorough knowledge of the biology of species involved. However, there has been a distressing lack
of research effort devoted to accumulating information on basic biology and ecology of most major
pests of soybean. Two examples with which I am
familiar serve to illustrate the point. The first involves .the bean leaf beetle. McConnell (915)
more than 60 years ago first reported that larvae of
the bean leaf beetle damaged roots and nodules of
cowpea and other leguminous plants including soybean. F. M. Webster's comments in the discussion
of McConnell's
paper are still pertinent. " ... We
began twenty-eight years ago with the investigation
of a beetle whose injuries were supposed to be
restricted to the foliage of leguminous plants. Now
we find ourselves at a point where we have to go to
the ecologist and the soil expert, as we find that the
larvae of this beetle in destroying the nitrogenous
nodules, largely takes away the fertilizing value of
these plants, especially if growing on the higher
lands where there is greatest need of additional fertility. And it takes us into a matter which the
agronomist has overlooked.
Mr. McConnell has
shown the actual financial value of these nodules to
the farmer as compared with the cost of sodium
nitrate."
This appears to be the first clearly
expressed need for interdisciplinary research of the
sort that IPM systems require.
The second example involves the velvetbean caterpillar and the soybean looper, two of the major
defoliators of soybean. Both are annual immigrants
into the southeastern U.S., but the source ofinvad-
371
resistant populations provided the migrants that
invaded GA and caused serious problems on soybean there during 1977. During 1979, GA and
some areas of adjacent states were again invaded by
soybean looper populations that were highly resistant to methomyl. What is even worse, these populations were also resistant to acephate and the synthetic pyrethroids other than those of the permethrin group (1. W. Todd, personal communication). Thus, pest control measures practiced in one
part of the country, or even in other nations, may
have drastic effects on the success of IPM systems
in another.
These examples illustrate the serious lack of
basic biological and ecological data required for development of IPM systems for single species of
insect pests. The lack of such data appears to be
equally
serious
for weeds,
nematodes,
and
microbial pathogens of soybean.
We have hardly begun to think about the kinds of
biological and ecological data required for the development of IPM systems for complexes of pest
species. For example, one of the most difficult
problems that must be solved is that of establishing
ElLs for pest complexes. Consider a simplified,
typical problem that occurs each year in hundreds
of thousands of acres of soybean in LA. There the
crop is often under attack simultaneously
by the
following species of pests during the pod filling
stage of growth and development: bean leaf beetle
adults and larvae, southern green stink bug adults
and nymphs, threecornered
alfalfa hopper adults
and nymphs, soybean looper and velvetbean caterpillar larvae, rootknot and soybean cyst nematodes,
ing moths is not known. The soybean looper over-
pod and stem blight, anthracnose, aerial blight, fro-
winters in the southernmost
areas of FL and TX.
The velvetbean caterpillar overwinters south of
28°N latitude in FL. Undoubtedly,
populations of
both species that overwinter in these areas are
sources of moths that invade nearby states.
However, data on time of earliest arrival of velvet
bean caterpillar
in the states affected,
and
differences in susceptibility to insecticides of soybean looper populations in FL and GA as compared
to those in states farther west, provide convincing
evidence that substantial numbers of the immigrating moths originate from areas outside the mainland U.S. Both species are strong flying noctuids.
Thus, they are potentially capable of utilizing wind
systems for making uninterrupted
migratory flights
over much greater distances than across the Gulf of
Mexico, for example.
The probability that immigrant species may have
developed resistance to various insecticides at their
source of origin poses unique problems for IPM
specialists in areas that are invaded each year.
Indeed, it appe~rs that this has already happened in
the case of the soybean looper. Populations of this
pest became resistant to methomyl as a result of
exposure to its intensive use on crops such as chrysanthemum in southern FL. It appears that these
geye leafspot, bean pod mottle mosaic virus, and a
disease of unknown etiology. At the same time the
crop may be subjected
to competition
from
johnsongrass,
morningglory and cocklebur. Any
one species of this complex is capable of causing severe damage with heavy loss of yield.
Reasonably satisfactory ElLs have been established for bean leaf beetle adults, southern green
stink bug adults and nymphs, soybean looper and
velvetbean caterpillar larvae, rootknot and cyst
nematodes,
and cocklebur.
ElLs, even of a
preliminary nature, are lacking for the remaining
dozen species.
Development
of effective
integrated
pest
management systems requires that ElLs be established for these pest complexes. It is unreasonable
to attempt to establish an ElL for defoliating insects
without considering injury to foliage caused by
plant pathogens such as frogeye leafspot and aerial
blight; or an ElL for rootknot and soybean cyst
nematodes without considering bean leaf beetle
and soybean nodule fly, for example. There are
numerous additional interactions, a few of which
have been reported between nematodes and other
plant pathogens. Eight fungal, two viral, and eight
nematode pathogens are involved in the reported
372
ESA BULLETIN
interactions (Bustillo 1972, Lindsey and Cairns
1971, Minton et a11975, Ross 1965, and Taylor and
Willie 1959). The interactions reported include: (I)
increased susceptibility to infections, (2) predisposition to attack, (3) both additive and synergistic increases in damage, (4) higher incidence
of disease on infected plants, and (5) stimulation of
viral replication.
In addition to direct effects on yield caused by
various pests and pest complexes, their damage
may affect nitrogen fixation by soybean. Apparently, McConnel
(1915) first recognized
this
phenomenon in his research on the bean leaf beetle. Ichinohe and Asai (I956) reported an inverse
relationship between severity of infection by soybean cyst nematode and nodulation of soybean.
Subsequently, Lehman et al (I971) reported that
races of soybean cyst nematode differed in their ability to inhibit N -fixation.
Recently, Newsom et al (I979) reported that the
N-fixing capacity of soybean is affected by defoliators such as soybean looper, stem feeders such as
the threecornered alfalfa hopper, and fungal pathogens, in addition to species that attack roots and
nodules directly. Thus, a new dimension has been
added to the problem of ElLs for pest complexes.
Considering the problem of synthetic nitrogen production, the capacity of soybean to fix nitrogen may
become as important as its capacity to produce oil
and protein during the next few decades.
Therefore, realistic ElLs for pests and pest complexes must also take into consideration their
effects on the nitrogen fixing capacity of soybean.
There are more than 100 pesticides labeled for
use on soybean. Forty-five are commonly recommended and sometimes used for control of the
more than 100 pests considered sufficiently important to be mentioned in the literature, Table 1.
Table t.-Number
of commonly used pesticides
beled for control of soybean pests.
Class of pests
Weeds
Insects
Nematodes
Microbial Pathogens
la-
No. pesticides used
22
9
6
8
Too little is known about possible direct and
indirect effects of these biologically potent chemicals acting singly on the biota of soybean
ecosystems. Possible phytotoxic effects on soybean
are routinely determined for all pesticides used on
the crop. Obviously the possibility of phytotoxic
effects of herbicides is relatively high. Dosage rates
of many herbicides have to be carefully adjusted to
soil type and weather conditions to avoid unacceptably high levels of injury to soybean. Recently,
more attention than previously has been devoted to
possible adverse effects of pesticides on non-target
Yol. 26 no. 3, 1980
organisms. Their effects on natural control agents
are being evaluated much more intensively than
formerly. Possible adverse effects on Rhizobium
spp., nitrifying bacteria, and other microorganisms
are routinely determined for some classes of
pesticides. Nearly all of such studies have been concerned with the effects of single compounds, but
the array of pesticides applied to soybean often end
up in the ecosystem as very complex mixtures.
How they affect the biota of a soybean ecosystem as
members of such a mixture may differ greatly from
their effects when applied individually. The impact
of mixtures of pesticides on the biota of agricultural
ecosystems has been studied inadequately at best,
but most often not at all.
Pesticides and Mixtures of Pesticides Applied to
Soil: Of all areas of research in integrated pest
management systems, soil biology has probably
been most neglected. Soybean, among the major
crops is most affected by phenomena that occur
belowground because of their involvement in
nitrogen fixation. Because a high percentage of the
pesticides used in soybean production is applied
directly to the soil, adverse interactions are more
likely to occur in soybean ecosystems than in any
other major crops.
A representative
pre-planting
regime of
pesticides applied to the soil of some soybean
ecosystems is shown in Table 2. Some herbicides
and insecticides when applied simultaneously at
recommended rates of application interact to produce severe phytoxicity [Johnson 1970; Hayes et al
1979].
Similar synergistic effects on soybean have been
observed with other combinations, especially those
involving
metribuzin
and the insecticide
nematocide aldicarb. The possible effects of such
combinations on the other biota of the soybean
ecosystem appear to have been virtually ignored. It
seems reasonable to believe that species such as
Rhizobium, Azotobacter, Glomus and other endomycorrhizae, weeds, insects, and microbial pathogens
may be affected.
Research on pesticide combinations is urgently
needed to provide answers to the following questions:
1. What are the effects on growth and development of soybean; on nodulation and N2-fixation; on nitrifying bacteria; on endomycorrhizae; on soil inhabiting natural control
agents?
2. What are the effects of root damage caused
by such combinations in the uptake of water,
soil nutrients, and systemic insecticides?
DiSCipline Complexes
Problems involving complexes of pests, their
natural enemies, other associated biota and the variety of tactics used in integrated pest management
Vol. 26 no. 3, 1980
373
ESA BULLETIN
Pesticide
Rate of application
lbs./ A
Pest
controlled
Trilluralin
2.0
Grasses
Metribuzin
0.37
Broadleaf tips
weeds
Unuron
2.0
Broadleaf weeds
Aldicarb
2.0
Mexican bean beetle
Bean leaf beetle
Nematodes
TOTAL
6.37
Know adverse effects of
pesticide used alone
Plants stunted, hypocotyls enlarged, secondary
roots thickened and reduced in numbers,
leaves small and crinkled.
Plants chlorotic, leaf margins and yellowed
and necrotic, death of seedlings
Same as for metribuzin
Marginal yellowing and necrosis of leaves,
crinkling of tip of leallets,destruction
of
insect natural enemies.
ESA BULLETIN
374
tively approach such problems experimentally. If
we are to make the progress that is so critically
needed, personnel who are trained differently than
they are today will be required. It appears that the
time has come seriously to consider development
of pest management as a discipline for training the
personnel required to work effectively in the broadly interdisciplinary area of integrated pest management. I recommend taking this drastic approach for
your serious consideration. Who knows? He who is
so bold and aggressive as to initiate such an
approach may be honored at some future meeting
of our Society as we have honored the father of integrated insect control, Professor Dwight Isely,
today.
Footnotes
tFounder's Memorial Award Lecture, presented at the ESA
National Conference, Denver, 1979,by 1. D. Newsom, in honor
of Dwight Isely.
2"The Principles,Strategiesand Tacticsof Pest PopulationRegulation and Control in Major Crop Ecosystems" supported by
NSF, EPA, V.S.D.A., and State Experiment Stations.
REFERENCES
CITED
Anonymous. 1979. Crop Production, Crop Reporting
Board, Economics, Statistics and Cooperatives Service, U.S. Dept. of Agr., Sept. Estimate of Acreage
Harvested.
Bustillo, B. A. 1972. InOuence of Ro/ylenchulus reniformis
infection on replication of cowpea chlorotic mottle
virus in 'David' soybean. Jour. Nematol. 4: 220-221
(A bstract).
Croft, B. A. and Hoyt, S. C. 1978. Considerations for the
use of pyrethroid insecticides for deciduous fruit pest
control in the U.S.A. Environ. Entomol. 7: 627-630.
Vol. 26 no. 3, 1980
Geier, P. W. 1976. The problem of environmentally acceptable methods of pest control. New Zealand
Entomol. 6: 106-112.
Hayes, R. M., Yeargan, K. V., Witt, W. W. and Raney,
H. G. 1979. Interaction of selected insecticide-herbicide combinations on soybean (Glycine max). Weed
Sci. 27: 51-54.
Ichinohe, M. and Asai, K. 1956. Studies on the rsistance
of soybean plants to the nematode
Heterodera
g/ycines I. Varieties, 'Daiichi-Hienuki' a~d 'Nanguntakedata' Res. Bull. Hokaido Nat. Agr. Exp. Sta. 71:
67-79.
Johnson, B. J. 1970. Combinations of herbicides and
other pesticides on soybeans. Weed Science 18:
128-131.
Lehman, P. S., Huisingh, D. and Barker, K. R. 1971.
The influence of races of Heterodera x!ycines on nodulation and nitrogen-fixing capacity of soybean.
Phytopathology 61: 1293-1244.
Lindsey, D. W. and Cairns, E. J. 1971. Pathogcnecity of
the lesion nematode, PralylencllUs bracl1yurus, on six
soybean cultivars. Jour. Nematol. 3: 220-226.
McConnel, W. R. 1915. A unique type of insect injury.
Jour. Econ. Entomol. 8: 261-266.
Minton, N. A., Parker, M. B. and Flowers, R. A. 1975.
Response of soybean cultivars to Meloido}Olne inl'OKnita and to the combined effects of M. arenaria and
Sclerotium rolfsii. PI. Dis. Reptr. 49: 920-923.
Newsom, L. D., Dunigan, E. P., Eastman, C. E.,
Hutchinson, R. L. and McPherson, R. M. 1978.
Insect injury reduces nitrogen fixation in soybeans.
La. Agr. 21 (4): 15-16.
Ross, J. P. 1965. Predisposition of soybeans to Fusarium
wilt by Helerodera g/ycines and Me/oidogyne incognita.
Phytopathology 55: 361-364.
Taylor, D. P. and Wyllie, T. D. 1959. Interrelationship of
root-knot nematodes and RlJizoclOnia so/ani on soybean emergence. Phytopathology 49: 552 (Abstract).