Research
Evolution and Implementation of a Biological Control-IPM System
for Crucifers: 24- Year Case History
K. D. Biever, D. L. Hostetter, and J. R. Kern
ABSTRACT An effective biological control-integrated pest management (BC-IPM) system for lepidopteran pests-Plutella xylostella
(L.), Pieris rapae (L.), and Trichoplusia ni (Hiibner)-of crucifers that maximizes biological control has been developed. In the late
1960s the first phase was developed; chemical insecticides were replaced by the judicious use of the microbial insecticide Bacillus thuringiensis. In 1980, following chemical insecticide resistance problems, the system was implemented; there was an immediate reduction
(>50%) in the number of treatment applications required. From 1985 to 1990 technology and procedures for using parasites for seasonal
inoculations were developed. Field tests conducted from 1988 to 1990 established that a complex of several species of parasites could
increase parasitism, reduce pest populations, and result in market acceptable cabbage and broccoli crops. In 1990-1991, the BC-IPM
system was successfully validated in 53 ha of commercial cabbage in Rio Grande Valley of Texas. A commercial insectary produced, sold,
and released the beneficial insects. This BC-IPM system is currently being used on a large scale for broccoli production in Guatemala.
A
BIOLOGICAL
CONTROL-INTEGRATED
PEST MANAGEMENT
SYSTEM
(BC-IPM) has been developed and successfully implemented
to manage lepidopteran insect pests of crucifers. The system
is environmentally sound and is currently in grower use. It requires
the use of biological control agents, pest population monitoring, and
early-season inoculative releases of beneficial agents and it replaces
the routine application of chemical insecticides.
The Beginning: A Plan Is Developed
The management system described here was not serendipitous,
but rather the culmination of an intermittent, persistent, 24-yr, research endeavor. The 24 yr required to develop and implement the
management program exemplifies the tenacity and persistence required from initiation of a research plan to realization of a management program that is accepted and used by growers. Following the
establishment of the USDA-ARS Biological Control Laboratory in
1965 in Columbia, MO, projects designed to promote the concepts
and tenets of biological control were developed. Cabbage was selected as the crop-pest model for the development of an IPM system that
concentrated research effort on managing a complex of pests with
biological control agents. By the time we (K.D.B. & D.L.H.) had an
opportunity to select research areas that were part of this overall
mission, areas of narrow focus-i.e., biological control of aphids
and importation and mass release of parasites for suppression of the
imported cabbageworm, Pieris rapae (L.)-were already being investigated by colleagues. We selected a research program with a
broader scope, that of developing and implementing a management
system that maximized the use of principles of biological control
while regulating the complex of pests. It was our initial hypothesis
that the development of a management system that relied on the use
of biological (microbial) insecticides rather than synthetic chemical
insecticides would permit the survival of naturally occurring beneficial agents that, in turn, could assist in reducing the pest populations. Also, we hypothesized that once a management system was
established that minimized the need for synthetic chemical insecticides, we could further enhance suppression of the pests through
early-season augmentative releases of selected beneficial agents.
Appropriately timed, early-season, inoculative releases of benefiThis article reports the results of research only. Mention of a proprietary product
does not constitute an endorsement or a recommendation for its use by USDA.
AMERICAN ENTOMOI.()(;IST
•
Summer 1994
cials should require relatively low numbers, because population
densities of the pest species are usually lowest during their early
generations each season. By introducing the beneficials into pest
populations that are below economic ]evels, the beneficia Is should
persist and increase in numbers if suitable hosts are available
throughout the growing season.
Our plan was to focus not on the crop system but on the process,
(i.e., developing BC-IPM systems should be similar regardless of the
crop). The process should include the following five steps: (1) establish fundamental biological information, (2) establish procedures
for monitoring pest populations, (3) reduce the number of insecticide applications, (4) replace synthetic chemical insecticides with
biological insecticides, and (5) maximize the use of biological contro] agents. Our goal was to develop a system that would integrate
several biological control agents and tactics into a comprehensive
program. Cabbage is an excellent challenge for such a system for five
reasons: (1) several lepidopteran pests attack the crop every year, (2)
the pests have several generations each year, (3) many applications
of chemicals are routinely applied, (4) the final product at harvest
must be free of insect damage, and (5) a biological insecticide (Bacillus thuringiensis) was available. Developing the system consisted of
three phases: (1) basic research (this involves steps 1-4 in the process
of developing BC-IPM systems), (2) implementatio!1 of phase one,
and (3) development of a seasonal inoculative release program for
beneficial agents to maximize biological control.
Baseline Information Developed
Basic information on pest and beneficial insects was acquired
during the 1967 growing season at a vegetable farm where crops
were grown organically (Ferguson, St. Louis County, MO). This 3ha farm had not used any synthetic chemicals for at least 17 yr.
Approximately 1.2 ha of cabbage was planted annually on the farm;
it was usually severely damaged by lepidopteran pests, resulting in a
harvestable crop far below market standards. The grower had a
strong but limited market, restricted to clientele with an extreme
aversion to chemicals.
Small plots, consisting of ",1,000 cabbage plants (0.04 hal, were
planted monthly (April to September) to provide a continuous supply of plant hosts for insect populations. The study plots, along with
the grower's cabbage fields, were monitored every 3 d to collect
population data on the imported cabbageworm; the diamondback
103
moth, Plutella xylostella (L.); the cabbage looper, Trichoplusia 11i
(Hiibner); and associated beneficial insects. The imported cabbageworm was the primary pest of spring cabbage grown at this location
(Fig. 1); the diamondback moth was most abundant during the
summer and was at low levels the rest of the season; the cabbage
looper, considered the major pest of cabbage in the St. Louis area
from late June through September, was not a pest at this farm during
1967 and, according to the grower, never had been.
Evaluation of a Biological Insecticide
In 1967, B. thuringiensis, a relatively new biological insecticide,
was being used on a limited basis and we considered it to be the
appropriate biological insecticide to incorporate into our management program; however, we were in need of field evaluation experience and data. After we provided documentation and thoroughly
explained the use of B. thuringiensis, the grower permitted application to one of his cabbage fields. Good control was obtained with
two applications of B. thuringiensis, Thuricide 90 TS (5 liters/hal,
one made when peak populations of first-instar imported cabbageworms of the first generation occurred and the other made similarly
in the second generation. This produced a bumper crop and far more
than his specialty market could absorb. Meanwhile, we had obtained basic biological information that allowed us to view the insect populations phenologically, according to their effect on the
various stages of plant-crop development.
In 1968, cabbage insects and control practices were evaluated
at several commercial vegetable farms in St. Louis County. Most
60
Imported Cabbageworm
50
40
if)
+J
6-6
Diamondback Moth
50
•
40
0..
0
30
'-.....
0
z
20
10
0
50
.-.
IV·
.... \
c
0
Eggs
Small Larvae
Large Larvae
0-0
.-.
I
-.-
Larvae
.\
Decision Process
Cabbage Looper
.-.
Larvae
40
30
20
10
o
100 125 150 175 200 225 250 275 300 325
Julian Day
Fig. 1. Seasonal abundance profiles for lepidopteran pests on cabbage at a
truck farm in St. Louis, MO, that did not use synthetic chemicals in 1967.
104
growers were routinely making eight or more applications of synthetic chemical insecticides to their spring crop. It was not possible to work intensively with several growers; therefore, we
concentrated our efforts at one farm (farm A), hoping that management techniques developed at this farm would be disseminated
by observation and word of mouth to the other growers in the
area. Based on weekly monitoring of insect populations on the
spring cabbage, we recommended application of chemical insecticides twice, a 75% reduction in use over previous years. Similar
monitoring procedures were followed in 1969; one application of
the microbial insecticide B. thuringiensis (Thuricide 90 TS, 5
liters/hal replaced the usual synthetic chemical insecticide and
provided effective control of pests on the spring crop. In 1970,
crop monitoring was conducted biweekly at two truck farms
(farms A and B), and periodic observations were made at several
other truck farms, to ensure that conditions at the study locations
were typical of the total growing area. Following our recommendations, the grower at farm B harvested 50% of his spring cabbage
crop without using any applied control measures; the remainder
of his spring crop and the crop at farm A required only one application of B. thuringiensis (Thuricide HPC 2.5 liters/hal. At farm
A, B. thuringielJsis was the only material used to protect the spring
cabbage, the summer and falI cabbage sprouts, and the falI cabbage. One application was used on the spring crop, and additional
applications were made to the sprouts and fall crop at approximately 3-wk intervals. Thus, only six applications of B. thuringiensis were used over the entire 7-mo growing season. In previous
years, this grower routinely used at least 20 applications of chemical insecticides during the same growing period. The cost per
hectare for materials and labor for either chemical insecticides or
B. thuringie'Jsis was ",$30. Thus, elimination of 14 applications
provided a savings of $420 per hectare.
After field evaluation of cabbage plants, pests, parasites, climatic
factors, planting and harvesting schedules, and control practices in
the St. Louis area for several years, we concluded that one or two
timely applications of insecticide would be adequate to protect the
spring cabbage crop and probably not more than six or seven applications would be required for the entire season. This schedule represented a significant reduction in insecticide use with no deleterious
effects on cabbage quality or yield. Moreover, the judicious use of B.
thuringiensis alIowed the beneficial agents to survive and put additional suppressive pressure on pest populations. We recovered several species of specific parasites from the three pest lepidopterans and
two pathogens (a nuclear polyhedrosis virus and a fungus, Nomuraea rileyi) from the cabbage looper; we also observed significant
spider populations.
Throughout the development of the BC-IPM system, decisions
on when to apply B. thuringiensis were based primarily on field
experience and biological logic rather than on fixed threshold levels
established by analyzing population and damage data. This may
have been a nontraditional approach for developing a pest management system, but was applicable to the logistical restrictions encountered (primarily geographical) because we were based",200 km from
the cabbage production area. One problem encountered in trying to
predict accurately the damage potential of various pest insect population levels was the lack of information-establishing levels of economic importance. For future program development, economic
injury level (ElL) and threshold data were needed.
During the 1971 season, we conducted field studies to determine
ElLs for the imported cabbageworm and the cabbage looper at three
stages of cabbage plant growth. In this test, third·instar larvae were
AMF.RICAN
ENTOMOl.OGIST
•
Summer 1994
placed on the outer leaves of the plants (two, four, six, and eight per
plant) and allowed to feed to maturity. Before the tests and following
larval feeding, the plants were kept free of larvae by hand removal
of eggs and first-instar larvae. We found that eight larvae of either
species on young plants did not affect the cabbage grade at harvest.
Also, neither four cabbage loopers nor eight imported cabbageworms reduced the grade when larvae were placed on plants with
small heads (8-10 em). However, two to eight cabbage loopers on
nearly mature cabbage reduced the grade below U.S. No.1, whereas
four and eight imported cabbageworms caused only slight damage
(cabhage was U.S. No.1 grade). Several other workers (Wolfenbarger 1967, Greene 1972, Shepard 1973) reported somewhat lower
economic thresholds for the cabbage looper, but they did not evaluate specific instars against specific plant stages.
At this stage in development (1970) it appeared that the IPM
system featuring B. thurilzgiensis was on its way to being implemented on a wide scale, but this did not happen as new and effective chemical insecticides (chlordimeform and methomyl) became
available and most growers used them on a regular spray schedule.
Because of other research obligations, only limited research activity occurred on the cabbage program from 1971 to 1979, because
the research focus at the Columbia Laboratory had turned to soybean insect pests. Although program continuity was compromised
during this period, two growers that continued to use the B. thuringiensis-IPM system made approximately one-third the number
of spray applications as did growers using chemical insecticides.
In 1977, these two were the only growers that were able to suppress populations of the cabbage looper; chlordimeform was no
longer available for use on crucifers and insecticide resistance to
methomyl was developing and was a serious problem by 1979
(Wilkinson et al. 1983). In 1979, the number of insecticide applications ranged from 4 to 10 on the spring and 4 to 10 on the fall
cabbage crops; despite that frequency of treatment, adequate control was not achieved. This intractable problem for the growers
provided an opportunity for us to implement the system we had
developed almost 10 yr earlier.
Implementation of the B. thur;ng;ens;s-IPM
System
We initiated a program to implement the B. thurillgiellsis-IPM
system in collaboration with the IPM Department at the University of Missouri. A 3-yr plan was developed based on the judicious
use of B. thuringiensis coupled with an insect scouting program.
Year one focused on grower education with active participation by
a few growers. The full cost of the scouting program was covered
by the university. In year 2, the number of growers and acreage
would be increased and the growers would share the scouting
costs. The primary goal of the year 3, besides fine-tuning the program, was to have the growers pay the full cost of scouting. In
early April 1980, we met with members of the United Vegetable
Growers Association of St. Louis, explained the program, and solicited participants; six growers were selected to participate. In
total, 25 ha of spring cabbage and 12 ha of fall cabbage were contracted the first year. Each grower had 1-10 ha within two to six
fields at each location. Monitoring of spring cabbage started in
mid-April (after transplanting) and continued until harvest in
mid-July (1 mo later than normal). Insect populations were monitored weekly by a field scout; whole-plant examinations were
made on 20 plants per field regardless of field size by walking a
diagonal X transect and selecting plants at approximately uniform
intervals. Decisions on when to treat the spring crop with B. thuringiensis were made on the basis of the scout's observations and
input from K.D.B. after which, the scout provided a recommendation to the grower; for the fall crop, the scout made the treatment
AMERICAN ENTOMOLOGIST
•
Slimmer 1994
determinations and gave the grower a recommendation immediately after monitoring. Applications were often restricted to certain fields or portions of specified fields; blanket treatments were
seldom required. The fall cabbage fields were monitored from 12
August to 21 November. Populations of the diamondback moth
were low throughout the spring and fall growing seasons, with the
exception of one buildup in early June. Cabbage loopers were not
a problem on the spring crop, even though the crop was harvested
late; however, they were the primary pest of the fall crop. Three
generations of the imported cabbage worm occurred on the spring
crop; this was one more than usual, a result of the late harvest.
Imported cabbageworm populations were consistently low on the
fall crop.
For the entire growing season of 1980, growers used approximately one-half as many applications of B. thurilzgiensis on their
cabbage as they had of various chemicals during the 1979 season;
the use of B. thuringiensis ranged from two to five applications on
the spring crop and from one to five on the fall crop. All participating growers were very supportive of the program and requested it be
continued and expanded to other vegetable crops.
During the developmental process of the B. thuringiensis-IPM
system, we observed that it took about three years to get the full
benefit of the program; this period of time allows for the recovery
and buildup of resident (background) beneficial populations (specific parasites, spiders, and diseases) at the locations. The one grower who had been on a B. thuringiellsis program for 12 yr used only
three applications during the 7-mo growing season of 1980 (one on
the spring and two on the fall crop). This is the same grower who
used six applications in 1970; this was evidence of the value of continuous and judicious use of B. thuringiensis.
In 1981, the cabbage IPM program expanded to 54 ha and nine
growers. Field scouting began in mid-April and continued through
October. Growers again used about half as many applications of B.
thuringiellsis for the entire growing season of 1981 on their cabbage
crop as they had used before the initiation of the IPM program when
various chemical insecticides (i.e., fenvalerate, malathion, methamidophos, methomyl, and mevinphos) were used. The growers were
thoroughly satisfied with the program even after paying half the cost
of scouting ($30/ha).
Nine growers with a total of 59 ha of cabbage, broccoli, and
cauliflower participated in the 1982 program; results were similar to
1981. Growers expressed continued satisfaction in 1982 and they
paid the full cost of scouting ($60/ha). Under the B. thuringiensisIPM system, populations of the imported cabbageworm and the
diamondback moth were at the highest level early in the season and
then decreased to low levels for the rest of season; in contrast, cabbage looper populations were low during the early part of the season
and then reached a peak level shortly after midseason (Fig. 2). The
weekly field counts for both the imported cabbageworm and the
cabbage looper illustrate an important point relative to insect numbers, population structure, and treatment decisions. Although the
numbers of eggs and small larvae seem high enough to cause a grower to consider applying a treatment, they are acceptable. Our B.
thuringiensis-IPM system is designed to eliminate the late stage larvae as they are primarily responsible for the feeding damage to cabbage (Theunissen et al. 1985). As shown, fourth- and fifth-instar
larvae of these two species were observed only occasionally; thus,
little damage was expected or observed.
Based on our earlier ElL research of 1971, and several years of field
experience with deciding when or when not to treat, we developed
treatment guidelines to assist scouts and growers conducting field
monitoring programs (Table 1). Following the 3-yr program on education, demonstration, and implementation of the B. thuringiensisIPM program, a private consultant took over the program.
105
60
.-.
Imported
50
0-0
40
[:,-[:,
Cabbageworm
Eggs
Small Larvae
Large Larvae
30
20
10
0
CfJ
+-'
50
0
40
c
0..
0
.-.
0
Diamondback
Moth
Larvae
30
"-.....
20
0
z:
10
0
50
40
••
.-.
Cabbage
0-0
[:,-[:,
Looper
Eggs
Small Larvae
Large Larvae
30
20
10
0
100
125
150
175 200
Julian
225
250
275
300
325
Day
Fig. 2. Seasonal abundance profiles for lepidopteran pests on cabbage
at a vegetable farm that used the IPM system featuring B. thuringiensis
in SI. Louis, MO, in 1982.
Research Program To Maximize Biological Contr·ol
By the 1981 season, it was apparent that we were close to completing the first four steps of the process in developing the BC-IPM
system. The remaining
step involved maximizing
the use of
biological control agents. Thus, we developed a plan that focused
on the following two objectives: (1) develop and validate a multipest management system that maximized the use of biological control agents to provide an alternative to chemical insecticides for
pest suppression,
and (2) develop an effective IPM program that
emphasized augmentation
of biological control agents through introduction
and periodic colonization
(early-season inoculation).
Following relocation of K.D.B. in 1984 to the ARS laboratory
in Yakima, WA, we decided not to let the BC-IPM program fall
short of our realized and attainable goal. The project was revised
and updated and we acquired special funding for a 5-yr research
program. Early in 1984, we found that population data on abundance and occurrence of the pests and associated beneficials of
crucifers in the northwest were not available. We conducted basic
population
studies to establish the database needed before initiating the field evaluation of beneficial species that would be part of
the augmentation
program.
ing this baseline information
Oregon
focused on establish-
at many locations
in Washington
(Biever 1992, Biever et al. 1992). Existing laboratory
ities were modified
106
Data acquisition
and developed
to accommodate
and
facil-
a rearing area
for production
of three host species and many parasitic species,
and a technical staff was recruited and trained in procedures and
skills needed to maintain and optimize production of the beneficial
agents. Initial stocks of all but one of the parasite species were
collected in the northwest. One parasite species, Cotesia plutellae
Kurdjumov, was introduced from Hawaii. The three lepidopteran
pest species-Po rapae, T. ni, and P. xylostella-were
reared using
the same laboratory diet (Berger 1963) for both colony production
and for host material for parasites. Colonies of the three pest species were established as well as colonies of the following parasitic
species: Diadigma insulare (Cresson),
Tetrastichus sokolowski
Kurdjumov, C. plutellae, Micropletis plutellae Musebeck, Pteromalus puparum (L.), Phryxe vulgaris (Fallen), C. rubecula Marshall, Voria ruralis (Fallen), and C. marginiventris (Cresson).
In 1988, we developed procedures to facilitate short-term storage of parasites for inoculative field releases; we also conducted the
first field releases of the pests and parasites. Three treatments were
evaluated in isolated plots (separated by a minimum of 1.2 km) of
cabbage; each plot consisted of 1,000 plants. Treatments
were:
pests only and two release rates of parasites (25 and 50 pairs per
species per plot). The entire season was a learning experience on
how to conduct a research program on isolated plots spread over
a SO-km area. This included trying to protect the plots from deer,
elk, and rodents. We also developed automatic drip-line irrigation
systems to provide water. Insect populations
were monitored
weekly. The diversity of the surrounding
habitats caused significant variability in insect populations and, because of the small plot
size (0.04 hal, the whole plot suffered from edge effect.
In 1989, pests (adults) were released on all plots on 12 May and
29 May at a rate of 250 pairs per species and we evaluated four
treatments: no parasites and eight species of parasites (adults) at
three release rates (150, 300, and 600 pairs per species). Plots were
separated by at least 1.6 km and consisted of 0.4 ha of broccoli.
The five parasite species that attack early instars were released on
29 May and the three that attack late instars and pupae were released on 11 June. Population monitoring (whole-plant counts and
dissection of third-stage
larvae for parasitism)
was conducted
weekly. All three parasite release rates reduced populations
of the
three pest species (Fig. 3). For the imported cabbageworm
and the
cabbage looper, the plots receiving the highest release rates of parasites gave the greatest level of pest suppression.
However, for
some unexplained
reason, the lowest rate of release for the diamondback moth provided the greatest pest suppression.
At harvest, the plots with the two highest parasite release rates had the
least insect damage (==5%). Plants in the plots with the lowest parasite release rate had ==15% damage and the control plants had the
most damage (==25%). Essentially, all broccoli heads from the release plots were marketable (U.S. Grade No.1) because our ratings
were conservative and considered
have been caused by an insect.
the slightest
damage
that might
Table 1. Treatment guidelines for imported cabbage worm, cabbage
looper, and diamondback moth on cabbage.
No. larvaelplanrt
--------------~-----After eight-leaf stage
Size of larvae
Large (>7 mm)
Medium (3-7 mm)
Small (<3 mm)
Transplants
Head areab
Outer leaves
0.3
1.0
2.0
0.1
0.1
1.0
3.0
6.0
aBased on a 20-plant count (whole-plant) observations). Treat with
B. thuringiensis when these levels are exceeded.
b Area includes head and wrapper leaves immediately surrounding the head.
AMERICAN
ENTOMOI.()(;rST
•
Summer 1994
Although only limited information is reported in this article on
rearing and production of the pest and beneficial insects, a tremendous amount of time, effort, money, and technical expertise were
required on a continuing basis, particularly for the field-release
programs. This operation was critical to the success of the total
program and required a manager who had the necessary skills, experience, dedication, and good judgement to make many day-today decisions. In 1989 alone, ",0.5 million parasites and 1.5 million
+-'
pests were produced.
c
In 1990, two treatments with three replications were evaluated: 0
pests (adults) only and pests plus released parasites (adults). Plots of 0....
'-......
broccoli were again 0.4 ha in size and separated by a minimum of Q)
0.8 km to restrict movement of pests and parasites between plots. 0
>
L
The pest populations were established by releasing 400 pairs of each 0
-.J
pest species on three dates over a 3-wk period. The parasite release 4program was designed to time the releases to coincide with the ap- 0
propriate stage of the pest. The six species of parasites that attack LQ)
the early instars of the host larvae were released three times over a 3- .D
E
wk period once hatch of the pests had occurred (900-1,200 pairs; :J
Z
totals per species). Two releases of the three parasite species that
attack the late instars and pupae were made (220-800 pairs; totals
per species). The plots that received parasite releases had higher
rates of parasitism (based on dissection of field collected third-stage
larvae) and the pest populations were suppressed. Population densities (both pest and beneficial) for the release and control plots were
similar during the first part of the season and are illustrated by data
reported on the imported cabbageworm (Fig. 4). We observed high
levels of parasitism (>80%) by midseason in the release plots after
which, cabbageworm populations were correspondingly lower
when compared with the control plots.
Validation and Transfer to Commercial Growers
In 1990, a series of fortunate circumstances provided the opportunity for our BC-IPM program to move from the realm of research-smail scale testing to real world-<ommercial grower's fields.
First, we secured some additional funding for fiscal year 1991 (1
October] 990-30 September 1991) to use in validating our research
findings. Second, we were approached by M. Maedgen, owner and
operator of BioFac, a commercial insectory, in Mathis, TX, who was
interested in developing a parasite release program for cabbage in
the Rio Grande Valley of Texas. He saw an impending need for an
alternative management approach as growers had reached a crisis
situation and could no longer effectively suppress populations of the
diamondback moth in southern areas of the United States because
of insecticide resistance. During the previous 6 yr, cabbage production had declined significantly in the Rio Grande Valley primarily
because of the inability to control the diamondback moth.
In a relatively short time, a strategy was developed and a Technology Transfer Agreement was established with BioFac (Agreement No. 58-3K95-M-32). The objectives focused on transferring
knowledge on beneficial insect production and field use for the cabbage system. We provided information on our BC-IPM system, parasite production technology, and stocks of parasites. BioFac began
parasite production and contracted with cabbage growers to participate in the biocontrol release program during the November
1990-June 1991 growing season. A technician (J.R.K) from the
Yakima Laboratory was temporarily located at the Weslaco USDAARS Laboratory to conduct field-population monitoring of insect
populations, to provide expert knowledge and information on rearing and release of beneficia Is, and to document the program under
commercial field conditions.
The program BioFac implemented was a modification of the
one we had previously developed, and was only concerned with
AMERICAN
ENTOMOI.Ol;IST
•
Slimmer
1994
4
Imported Cobbogeworm
0-0 Control
• -.150
3
6300 Parasites
6• -.
2
Porasites
600Parasites
L
•
0-0______./0
i~~~·--·
/i
66_6~~~
0
Diamondback
~~==--.
Moth
0
~.
~~::;.
__o~~_.
12
9
6
3
=-- ::::::----
0
Cabbage
Looper
0
/
~..-.~
3
2
0
i~6~.
0
140
0-0
150
160
170
--
180
190
Julian Date
Fig. 3. Seasonal abundance profiles for lepidopteran pests on isolated broccoli plots receiving releases of seven different speciesof parasites in 1989.
100
E
.-.
0-0
80
Parasite
Control
(j)
60
0
L
0
•
/\
•
•
(j)
-+-'
release
.-.
'"
40
0~
20
/0--0
...............
0
0
+-'
C
0
0....
0
1.5
~
.;
Q)
0
>
. ./
1.0
L
/0
0
~
." /
./'"
0.5
0
z
.
.
/
0-0
/'
0
/~-O/
0.0
140
160
180
200
Julian Date
Fig. 4. Population counts of the imparted cabbageworm on isolated broccoli plots and rates of parasitism based on dissection of third instars in 1990.
107
two lepidopteran
pests, the diamondback
moth and the cabbage
looper. They released C. plutellae and D. insulare for the diamondback moth, C. marginiventris and Trichogramma pretiosum for
the cabbage looper, and the predator Chrysoperla rttfilabris for the
lepidopterans,
whiteflies, and aphids. Diamondback
moth was expected to be the dominant pest; however, it turned out that the
cabbage looper was the primary pest. This may have been a fortunate occurrence as it demonstrated
to the growers and to BioFac
the importance of a monitoring program to establish t~_eappropriate control tactics, particularly when these tactics are species specific. BioFac's program
depended
on regular releases of the
beneficials, rather than tailoring them to scouting based decisions;
thus, more beneficials were released than needed and, at times,
releases were made when suitable host stages were not present.
Our view is that, when implementing a new type of management
strategy, it is better to release too many rather than too few. Growers also are used to having insect management procedures applied
on a regular basis; thus, these scheduled releases provided them
with a sense of security. Our premise was that if a scheduled release
system could be cost effective and accepted by the growers, then
the next phase would be to release only when needed and, thus,
reduce costs.
The program involved five growers and 53 ha of cabbage (eight
fields) that were monitored weekly. Several combinations
of treatments were used and depended on need based on field monitoring
and on the time the field was added to the program. Treatments
were: release of beneficial agents only, release of beneficial agents
plus B. thuringiensis when needed, and release of benef:cial agents
plus B. thurittgiensis and chemical insecticides (fields put into the
program after receiving one or more applications of chemical insecticides). Seventy-five percent of the fields receiving releases of
beneficials agents received one application
of B. thrtringiensis.
Cabbage fields not in the program, but in the same goographical
area, received between 5 and 26 applications of chemical insecticides. The cost of using the beneficials compared favorably with
insecticide treated fields and provided satisfactory crop protection. Insect damage at harvest was evaluated at two grower locations. The average damage for fields treated with chemical
insecticides was 1.4% and for the BC-IPM fields it was 0.6%. The
average cost for the chemical insecticide treated fields was $390/ha
(313~27)
and for the BC-IPM it was $395/ha (121-511).
The
bottom line measure of success for this new management approach
was that the cabbage growers contracted with BioFac for the following seasons. Although far from perfect, the field project demonstrated
that a BC-IPM system that emphasizes augmentative
releases of a number of beneficial species can regulate a complex of
pest species. The research had been successfully transferred
to
commercial
production.
This field validation
program contributes
to the process of
changing the method by which we manage insect pest populations
and pest complexes. This alternative approach is environmentally
sound and provides a control system that can be used for the long
term. We have entered a new era of pest management,
one that is
more knowledge intensive; i.e., beneficial agents require more precise utilization than broad spectrum insecticides. Therefore, crop
monitoring to quantify pest complexes, ages, and numbers becomes
critical to making control decisions.
The Rio Grande cabbage growers were involved in the experimental process of taking new techniques and making them work in
the field. This BC-IPM program should increase in effectiveness on
a year-to-year basis because once the chemicals are minimized in the
system, the populations
of native biological control agents will increase and assist in reducing pest numbers. This implementation
program in the Rio Grande again emphasized that a great deal of
108
education of growers and others involved in the industry is required to establish and use a sound biological control management
system.
Current Commercial Use
The release program continues to operate on a limited basis in
the Rio Grande Valley; however, it is in use on a large scale in
Guatemala. BioFac initiated a BC-IPM program in Guatemala in
October 1993, and through March of 1994 more than 300 ha of
broccoli were protected by this system. Results were excellent and
the size of the program will increase several fold during the
1994-1995
season.
Acknowledgments
We wish to thank the many individuals who contributed to making this
program a success. In particular, we express appreciation to many technicians, seasonal employees, and field scouts that participated. Thanks to
those who helped move the program forward when rhings got slow: Mahlon
Fairchild, former director of IPM Programs, University of Missouri, Waldemar Klassen, former associate deputy administrator of ARS, Robert Jackson
(deceased), former national program leader for ARS, and Buddy Maedgen,
BioFac. A very special thanks goes to the many growers in Missouri, Washington, Oregon, and Texas who provided the key to moving science into
action.
References Cited
Berger, R. S. 1963. Laboratory techniques for rearing Heliothis species on
artificial medium. USDA-ARS (Report) 33-84.
Biever, K. D. 1992. Distribution and occurrence of Cotesia rubecula (Hymenoptera: Braconidae), a parasite of Artogeia rapae in Washington and
Oregon. J. Econ. Entomo\. 85: 739-742.
Biever, K. D., R. L. Chauvin, G. L. Reed & R. C. Wilson. 1992. Seasonal
occurrence and abundance of lepidopteran pests and associated parasitoids on collards in the northwestern United States. J. Entomo\. Sci. 27:
5-18.
Greene, G. L. 1972. Economic damage threshold and spray interval for cabbage looper control on cabbage. J. Econ. Entomo!. 65: 205-208.
Shepard, M. 1973. A sequential sampling plan for treatment decisions on
the cabbage looper on cabbage. Environ. Entomo!. 2: 901-903.
Theunissen, J., H. den Ouden & A.K.H. Wit. 1985. Feeding capacity of
caterpillars on cabbage, a factor in crop loss assessment. Entomo!. Exp.
App!. 39: 255-260.
Wilkinson, J. D., K. D. Biever, & D. L. Hostetler. 1983. Resistance of the
Cabbage Looper, Trichoplusia ni (Hiibner) (Lepidoptera: Noctuidae) to
Methomyl in Missouri. J. Kans. Entomo!. Soc. 56: 59-61.
Wolfenbarger, D. A.I967. Seasonal abundance and damage estimates of cabbage looper larvae and two aphid species. J. Econ. Entomo\. 60: 277-279.
Received for publicatioll 2 June 1993; accepted 12 November 1993. •
K. Duane Biever is a research entomologist with the USDAARS, Fruit and Vegetable Insect Research Unit, 3706 W. Nob Hill
Boulevard, Yakima, WA 98902. Currently he is developing a BCIPM system for two key pests of potatoes, the Colorado potato
beetle and the green peach aphid. Donald L. Hostetter is a research entomologist with the USDA-ARS, Grasshopper IPM
Project, Route 1, Kimberly, 10 83341. His research interests focus
on insect pathology and microbial control of Orthoptera and Lepidoptera. Jonathon R. Kern is a former USDA-ARS technician and
currently is the manager and operator of an organic fruit and vegetable farm, Grantwood Farm, Box 9, Bloomsdale, MO 63627. He
also is an independent crop consultant and is coordinating the field
operations of BioFac's BC-IPM program in Guatemala.
AMERICAN ENTOMOI.OGIST
•
Summer 1994
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INSECT
HORMONES
H. FREDERIK NIJHOUT
PARASITOIDS
Behavioral and Evolutionary
Ecology
H.C.J. GODFRAY
Although insect endocrinology is one of the oldest
and most active branches of insect physiology, its classic
general texts are long out of date, while its
abundant primary literature provides
little biological context in which
to make sense of the discipline as a whole. In this
book, H. Frederik
Nijhout provides a
complete, concise,
and up-to-date
source for students
and nonspecialists
seeking an overview
of the dynamic and wide-ranging
science that insect endocrinology has become since its
beginnings nearly eighty years ago in the study of insect
metamorphosis.
Parasitoids lay their eggs on or in the bodies of other
species of insect, and the parasitoid larvae develop by feeding
on the host, causing its eventual death. Known for a long time
to applied biologists for their importance in regulating the population densities of economic pests, parasitoids have recently
proven to be valuable tools in testing many aspects of evolutionary theory. This book synthesizes the work of both schools
of parasitoid biology and asks how a consideration of evolutionary biology can help us understand the behavior, ecology, and
diversity of the approximately one to two million species of
parasitoid found on earth.
" An important and much-needed book. There is
currently no other such synthesis available."
-Gene E. Robinson, University of Illinois
Monographs in Behavior and Ecology
Cloth: $35.00 ISBN0-691-03466-4
Due September
1994
69 line illustrations
Paper: $29.95 ISBN0-691 -00047-6
Cloth: $75.00 ISBN0-691-03325-0
PRINCETON UNIVERSITY PRESS
AVAILABLEATFINEBOOKSTORES
ORDIRECTLY
FROMTHEPUBLISHER:
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