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BIOLOGICAL AND MICROBIAL CONTROL
Multiple Orifice Distribution System for Placing Green Lacewing Eggs
into Verticel Larval Rearing Units
S. W. WOOLFOLK,
1
D. B. SMITH,
2
R. A. MARTIN,
2
B. H. SUMRALL,
2
D. A. NORDLUND,
3,4
AND R. A. SMITH
3,5
J. Econ. Entomol. 100(2): 283Ð290 (2007)
ABSTRACT Green lacewings are widely used biological control agents for various insect pests. To
meet the needs of growers, green lacewings are being mass-reared commercially around the world.
A common salt shaker has been used regularly to distribute eggs into Verticel lacewing larval rearing
units. This technique is time consuming and inefÞcient because the number of eggs distributed in each
cell is inconsistent. The multiple oriÞce distribution (MOD) system described here greatly improved
egg distribution efÞciency by increasing the percentage of Verticel cells containing the desired one
to four eggs per cell (i.e., 40.8 and 52.1% by using salt shaker method versus 61.9% by using the MOD
system). This mechanical system signiÞcantly reduced the labor and time involved in the process and
would cost under $3,500. In addition, this new system could be modiÞed for distribution of other insect
eggs.
KEY WORDS biological control, insect rearing, lacewing, MOD system, Verticel larval rearing unit
Green lacewings (Neuroptera: Chrysopidae: Chry-
soperla) have long been recognized as important pred-
ators against insect pests in many cropping systems,
including vegetable, fruit, nut, Þber, and forage crops
as well as ornamentals, forests, and greenhouse plant-
ings (Tauber et al. 2000, McEwen et al. 2001). Efforts
to use green lacewings in augmentative release pro-
grams began in the late 1940s (Doutt and Hagen 1949,
1950), were revived in the 1960s (Lingren et al. 1968;
Ridgway and Jones 1968, 1969; Van den Bosch et al.,
1969), and are now among the most commonly used
and commercially available biological control agents
in the world (Wang and Nordlund 1994, Daane et al.
1998). Other than North America, green lacewings are
used in Russia, Egypt, western Europe, India, and
China (Wang and Nordlund 1994, Hoffmann et al.
1998). More than 130 companies in North America
(Hunter 1997) and 26 companies in Europe (Van
Lenteren et al. 1997) produce and/or sell biological
control products, including green lacewings. This
number does not include biological control companies
in Central and South America, Asia and Australia. The
two species of lacewings commercially available in
North America are Chrysoperla carnea (Stephens) and
Chrysoperla rufilabris (Burmeister) (Hunter 1997).
Although adults feed primarily on honeydew, pollen,
and nectar of ßowers, Chrysoperla spp. larvae are car-
nivorous (Carrillo et al. 2004). Larvae predominantly
prey on aphids, mealybugs, spider mites, whiteßies,
and small lepidopteran larvae such as cotton boll-
worms (McEwen et al. 2001). More than 70 prey
species have been reported for C. carnea alone (Balduf
1939).
Currently sold mainly for use in organic gardens and
greenhouses, lacewings represent an economically
substantial industry. Despite that green lacewings
have been reared and released as biological control
agents for many years, and their effectiveness has been
demonstrated in various crops (Nordlund and Morri-
son 1992), they have not been widely adopted outside
of a few niche markets. One reason for this discrep-
ancy is the limited ability to economically rear these
valuable predators in sufÞcient numbers for practical
use. Rearing techniques and recent improvements to
these techniques have been reviewed and reported by
Morrison and Ridgway (1976), Morrison (1977a,b),
Nordlund and Morrison (1992), Nordlund (1993),
Nordlund and Correa (1995), and Cohen and Smith
(1998). The development and improvements of arti-
Þcial diets for the lacewing by Cohen and Smith
(1998) have tremendously reduced the rearing cost of
the diet from $500 per kg to only $6 per kg (U.S. patent
nos. 5,834,174 and 5,945,271). Reduction of rearing
costs brings us closer to the goal of mass-releasing
lacewings as biological control agents for managing
arthropod pests in Þeld crops.
Green lacewing larvae are highly cannibalistic, a
characteristic that complicates their rearing. The ap-
proach that is currently used to prevent larval canni-
1
Corresponding author: Department of Entomology and Plant Pa-
thology, Mississippi State University, MS 39762 (e-mail: sww3@
entomology.msstate.edu).
2
Department of Agricultural and Biological Engineering, Missis-
sippi State University, MS 39762.
3
USDAÐARS, Biological Control and Mass Rearing Research Unit,
Mississippi State, Mississippi 39762.
4
Current address: USDAÐARS, OfÞce of Transfer Technology,
Athens, GA 30604.
5
Current address: 749 Middle Cove Dr., Plano, TX 75023.
0022-0493/07/0283Ð0290$04.00/0 䉷 2007 Entomological Society of America
balism is to rear each lacewing larva individually in
small cells of some type. In North America, the pri-
mary material used for this purpose is Verticel (Hexa-
comb, University Park, IL), which was Þrst used
by Morrison (1977a,b). When Sitrotoga cerealella
(Olivier) or Ephestia kuehniella Zeller eggs are used as
lacewing prey, a common salt shaker Þlled with a
mixture of lacewing eggs and Sitotroga (both as a
carrier and source of prey for the Þrst instars) is used
generally to distribute both types of eggs into the
Verticel larval rearing units. Consistent, uniform, and
efÞcient distribution of lacewing eggs into Verticel
units had been a continuing problem in lacewing rear-
ing. However, with the invention of an artiÞcial diet
for lacewing larvae (Cohen and Smith 1998), Sitotroga
or Ephestia eggs are no longer needed.
Nordlund (1993) reported the use of a hot melt glue
system, to improve the efÞciency of preparing Verticel
larval rearing units. Nordlund and Correa (1995) sub-
sequently developed a system by using sodium hypo-
chlorite to harvest lacewing eggs that yielded eggs
with no attached stalks. These improvements to the
rearing system provide moisture resistant larval rear-
ing units and clean loose eggs. Such improvements also
would enable the system we describe below (i.e.,
multiple oriÞce distribution system) to distribute
lacewing eggs into the cells of a Verticel larval rearing
unit.
As a part of lacewing egg mass releases, particularly
using an augmentative technique, many past studies
were devoted mostly to their distribution in the Þeld
to increase their effectiveness as biological control
agents. For example, Gardner and Giles (1996) con-
ducted a study to determine the effect of vibration on
the viability of green lacewing eggs in the Þeld. The
eggs were placed in a vermiculite mixture and sub-
jected to a range of vibrations from 1 to 100 Hz when
exposed to each treatment from 5 to 60 s. They found
that neither the frequency nor the duration of vibra-
tions had any effect on egg survival. Also, research was
conducted at the University of Wales to determine
how well green lacewing eggs survived when placed
in water (McEwen 1996). Their results showed that
the eggs were able to survive2dinwater with no
adverse effects. After this time, egg survival declined
markedly and after 8 d, none hatched. In the Þeld,
several methods have been developed to improve uni-
formity of distribution of eggs. Most of these are fo-
cused on obtaining a homogeneous mixture of eggs in
a liquid medium and then spraying the medium on a
designated area. Sengonca and Lochte (1997) dem-
onstrated that the eggs were able to withstand liquid
spray pressures ⱕ449 kPa (65 psi) with no adverse
effect. Both coarse and Þne droplet spray techniques
were developed that allowed for the eggs to be uni-
formly distributed under Þeld conditions. When dis-
tributed using these spray techniques, the hatch rates
were nearly identical to that of the controls, suggesting
that the eggs were able to survive the treatment. These
methods are currently being used in agricultural Þeld
settings across America. There are currently more
than two dozen Þeld sprayers dedicated solely to the
distribution of insect eggs (Burnam 1997).
Although these studies on egg distribution in the
Þeld are important, there has been very limited study
on the egg distribution problem in the laboratory for
mass rearing. Until now, there has been no accurate
way to evenly distribute lacewing eggs within the cells
of a Verticel larval rearing unit (Nordlund 1993). The
cells into which the eggs must be deposited are S-
shaped with an average width and length of 6.4 and 6.6
mm, respectively. The depth of the cells is 10 mm.
Also, the cells in the pieces of Verticel are not per-
fectly uniform, which further complicates the process.
Lacewing eggs have an average diameter of ⬇200
m
and are relatively fragile. Thus, the task of accurately
distributing individual and viable eggs into the cells of
a larval rearing unit is difÞcult and time-consuming.
Development of a mechanical system that can distrib-
ute a consistent number of eggs into each Verticel cell
is necessary, particularly in a mass rearing facility such
as commercial insect suppliers.
Our objectives were to develop 1) a consistent
method of distributing from one to four lacewing eggs
in each cell of a 15.2- by 30.5-cm piece of Verticel
rearing unit that can be used in a mass rearing system;
2) a system that does not cause any signiÞcant adverse
effect on the percentage of egg hatch; and 3) an
economical set of equipment that is ergonomic (i.e.,
can maximize productivity by minimizing operator
fatigue and discomfort). We used C. rufilabris eggs to
evaluate the application system but should have utility
for a variety of insect eggs. The target rate of one to
four eggs per cell was considered to be a realistic goal
because the larvae are cannibalistic and ultimately
there will only be one surviving larva per cell.
Materials and Methods
Source of Eggs. Chrysoperla rufilabris eggs were
obtained from Biological Control and Mass Rearing
Research Unit (BCMRRU), USDAÐARS, Mississippi
State, MS, and a commercial insect supplier (BeneÞ-
cial Insectary, Redding, CA). One-day-old eggs were
harvested according to the standard protocol of both
rearing facilities. Once received, eggs were stored
temporarily in 4⬚C for a maximum of 24 h.
Description of Multiple Orifice Distribution (MOD)
System. To develop the best possible distribution sys-
tem, a preliminary study was conducted to consider
the widest range of ideas possible. Seven possible egg
distribution system designs were considered, and the
strengths and weaknesses of each design were evalu-
ated before the Þnal design was selected (data not
presented). Our system is described here, and it is the
Multiple OriÞce Distribution system (MOD system)
that we designed, developed, and fabricated. It con-
sists of four major components: 1) a reservoir; 2) a
peristaltic pump (Masterßex L/S standard drive,
model P-07520-10) with a Masterßex easy load pump
head (model P-70518-00, Cole-Parmer Instrument
Co., Niles, IL); 3) multiple oriÞce manifold (custom
made); and 4) a conveyor belt (Dorner model 2100-
284 J
OURNAL OF ECONOMIC ENTOMOLOGY Vol. 100, no. 2
0804-01/02 conveyor belt) with a model 2320-09A1-
1414 bottom-mounted end drive and a model 22-060R-
0005-8 air gear motor, 60:1 ratio (Dorner, Hartland,
WI) (Fig. 1).
The system works by pumping the solution or sus-
pension containing the lacewing eggs through a plastic
tubing with a peristaltic pump to the multiple oriÞce
manifold (Fig. 1). Extending downward from the mul-
tiple oriÞce manifold are 23 stainless steel tubes (di-
ameter of 0.32 cm with i.d. of 0.15 cm each), corre-
sponding to the 23 rows of cells in each piece of the
Verticel rearing unit. The solution or suspension ßows
from the distribution tubes into the rows of Verticel
units. The inlet, stainless steel tubes (diameter of 0.64
cm) were mounted at a 45⬚ angle from vertical to help
create equal pressure at each of the outlet tubes. The
distribution tubes were spaced at equal distances (0.64
cm) along the manifold. The manifold was mounted
directly over a conveyor belt on which the pieces of
Verticel were placed end to end. The speciÞc posi-
tioning of the manifold and the spacing of the distri-
bution tubes allowed each tube to pass directly over
a corresponding row of cells.
By increasing the cross-sectional area of the man-
ifold, the velocity of the ßuid ßowing through it is
reduced. The reduced velocity minimizes the loss of
pressure due to friction. It was decided that the cross-
sectional area of the manifold should be at least double
the total cross-sectional area of the 23 distribution
tubes. This led to a calculated value of 1.08 cm for the
manifoldÕs i.d. A section of pipe with an i.d. of 1.59 cm
(2.22-cm pipe) was chosen because of its availability.
For the manifold to operate correctly, it was nec-
essary to remove all air and completely Þll it with the
egg solution before outßow from the distribution
tubes. To accomplish this, an air vent (of 0.64 cm
stainless steel tubing) was added at the top of the
manifold. Plastic tubing Þtted with a clamp was added
to the air vent. To Þll the manifold, the 23 distribution
tubes were temporarily closed and the pump was ac-
tivated. The manifold was full when ßuid occurred in
the vent tubing. At this time, the plastic tubing air vent
was closed and the 23 distribution tubes were uncov-
ered, allowing the egg solution to ßow out of the tubes
when the pump was activated.
Tube Flow Rate Measurement. Based on the design
of the manifold, we assumed that uniform ßow rates
would occur among the 23 distribution tubes. To de-
termine whether the ßow rate of each spraying tube
was indeed uniform, the amounts of suspension that
passed through the tubes were collected over a period
of 1 min by using a 100-ml graduated cylinder and a
stopwatch. At the speed that we previously deter-
mined (i.e., 1,042 ml/min for a total of 23 tubes, or
45.30 ml/min per tube), the ßow rates of tube one (far
left tube), tube 12 (center tube), and tube 23 (far right
tube) were measured six, Þve, and Þve times, respec-
tively. The mean ßow rate value for each of these three
tubes was then calculated.
Egg Hatch Experiment. An experiment was con-
ducted to determine whether our MOD system would
affect egg hatch percentage. Two liquid carriers were
used for this test, i.e., tap water and 5% ethyl alcohol.
Water was selected based on the previous study
(McEwen 1996) where lacewing eggs were not af-
fected when the eggs were placed in water for 2 d. The
5% ethyl alcohol was selected as a potential surface-
sterilizing agent for lacewing eggs. Lacewing eggs, 500
ml of one of the two carriers, and a stir bar were placed
in a 2-liter plastic beaker. The stir bar was used to keep
the eggs homogeneously suspended. The percentage
of egg hatch was measured for the following treat-
ments: 1) eggs in a water carrier without passing
through the MOD system, 2) eggs in a water carrier
passing through the MOD system, 3) eggs in 5% ethyl
alcohol carrier without passing through the MOD sys-
tem, 4) eggs in 5% ethyl alcohol carrier passing
through the MOD system, and 5) eggs with no carrier
without passing through the MOD system (control).
For treatment 1 and 3, the eggs were stirred contin-
uously using a magnetic stirrer (Fisher model 310T,
Fisher, Hampton, NH). After the eggs were stirred for
⬇2 min, they were immediately withdrawn using a
disposable pipette and spread onto Þlter paper (5.5
cm). For treatments 2 and 4, the eggs and solution
were stirred for ⬇2 min, passed through the MOD
system at a rate of 1,050 ml/min, and placed in a plastic
Fig. 1. Overview of MOD system. (A) The system con-
sists of a solid conveyor belt, where the Verticel larval rearing
unit is placed, a spray manifold, a peristaltic pump, and a
reservoir. (B) The spray manifold: the top rows of tubes are
two feed tubes (one tube on the left and one tube on the
right) and air vent (middle), and the bottom rows are 23
distribution tubes. The MOD system works by pumping liq-
uid carrier from reservoir through a plastic tubing with a
peristaltic pump to the manifold.
April 2007 WOOLFOLK ET AL.: DISTRIBUTION SYSTEM FOR Chrysoperla EGGS 285
box (42 by 29 by 15 cm). The eggs were then imme-
diately withdrawn using a disposable pipette and
spread onto Þlter paper (5.5 cm). All Þlter paper con-
taining eggs (treatments 1Ð 4) were air-dried in a lam-
inar ßow hood for ⬇10 min and then cut into small
pieces (⬇0.5Ð1.0 cm
2
) to obtain a single egg for each
Þlter paper piece. For treatment 5 (control), the eggs
were placed directly in insect diet cups, one egg per
one cup. Because of cannibalism nature of lacewing
larvae, eggs for treatments and control were then
placed individually in insect diet cups (volume size 1
oz.; BioServ, Frenchtown, NJ). The cups containing
lacewing eggs were kept in a controlled holding room
(27⬚C temperature and 80% RH with photoperiod of
16:8 [L:D] h) at the Insect Rearing Center (Depart-
ment of Entomology and Plant Pathology, Mississippi
State University). The emergence of larva in each cup
was observed for days 1Ð 6. Each treatment (including
the control) was repeated Þve times, and each repli-
cate consisted of 10 C. rufilabris eggs. Experiment was
arranged as a randomized complete block design and
data were analyzed using a one-way analysis of vari-
ance (ANOVA) (P ⱕ 0.05).
Distributing Lacewing Eggs by Using the Multiple
Orifice Distribution System. Six Verticel (15.2- by
30.5-cm) rearing units were prepared. A unit was con-
sidered to be one replicate. Using a hot melt glue
system (Nordlund 1993), an organdy cloth (15.5 by 31
cm) was glued onto the bottom side of each Verticel
piece and dried before the MOD system run. A 2-liter
graduated cylinder with a stir bar was Þlled with 2,000
ml of tap water and 1 ml of Dawn dishwashing liquid.
The Dawn liquid was added to break the surface ten-
sion between the eggs and tap water. Approximately
40,000 C. rufilabris eggs were then poured into the
graduated cylinder and stirred continuously using a
magnetic stirrer at the speed where eggs seemed to be
even and homogeneously suspended from the bottom
to the top of the graduated cylinder. As described
previously, the MOD system was run at a ßow rate of
1,042 ml/min (for 23 tubes) and a rotational speed of
100 rpm. After the system had run for a few minutes,
six Verticel units were placed on the conveyor belt,
one followed by the other. Once a Verticel unit had
passed under the distribution tubes, it was removed
from the conveyor belt and placed on layers of paper
towels to remove the excess water to help the Verticel
unit dry. The Verticel units were then placed in a
laminar ßow hood for complete drying of the eggs, and
the eggs per cell were then counted using a standard
laboratory microscope at 100⫻ magniÞcation. The
number of eggs in each cell (total of 966 cells per
Verticel unit) was counted in the six Verticel rearing
units.
As a control, a common salt shaker was used to
distribute C. rufilabris eggs into the Verticel units.
Approximately 1,700 eggs per replicate were added to
a salt shaker. These eggs were distributed as uniformly
as possible over six pieces of Verticel units (i.e., six
replicates). The number of eggs in each cell located on
the outer two rows and columns on each piece of
Verticel unit plus two rows and columns at the center
was counted. The number of eggs in each of 300 cells
per replication was counted. The eggs in the Verticel
cells were counted by using a standard laboratory
microscope at 100⫻ magniÞcation. Data obtained by
using the MOD system and salt shaker method were
analyzed using a chi-square test with two independent
sample populations (P ⱕ 0.05).
Results
Tube Flow Rate Measurement. The mean liquid
ßow rate for tube 1 (far left tube), tube 12 (center
tube), and tube 23 (far right tube) was 49.33 ⫾ 0.98,
49.80 ⫾ 1.64, and 49.33 ⫾ 0.97 ml/min, respectively.
These results indicated that the tube ßow rates were
uniform across the entire manifold.
Egg Hatch Experiment. The mean percentage of
egg hatch ranged between 94 Ð98% (data not pre-
sented). The percentages of lacewing egg hatch were
not signiÞcantly affected among the Þve treatments
(i.e., eggs in water carrier without passing through the
MOD system, eggs in water carrier passing through the
system, eggs in 5% ethyl alcohol without passing
through the system, eggs in 5% ethyl alcohol passing
through the system, and control) (F ⫽ 0.42; df ⫽ 4, 24;
P ⫽ 0.79).
Distribution of Eggs by Using the MOD System
versus Salt Shaker Method. The number of eggs per
cell distributed using the MOD system was signiÞ-
cantly different from that of the salt shaker method
(
2
⫽ 1,718.60, df ⫽ 21, P ⫽ 0.95). The average number
of lacewing eggs distributed in Verticel units using the
MOD system was 1.2 eggs per cell. The mean per-
centage of the desired number of eggs (one to four
eggs) in each cell was 61.9%. The number of eggs
distributed by this system ranged from zero to eight
eggs per cell (Table 1). In comparison, the average
numbers of eggs distributed using the common salt
shaker method were 2.83 and 2.80 eggs per cell (from
two observation dates) and the mean percentage of
cells containing one to four eggs per cell was only 40.8
and 52.1%, respectively (Table 2). The numbers of
eggs distributed in each cell with the salt shaker
method ranged from zero to 15 eggs on the Þrst ob-
servation date and from zero to 20 eggs for the second
date.
The average of total number of eggs from distribu-
tion tube numbers 1Ð23 ranged from 26 ⫾ 28.58 to 68 ⫾
15.54 eggs per tube (Table 3). Several tubes showed
totals of fewer than 25 eggs per distribution tube.
Discussion
The egg hatch experiment was conducted to see
whether passing the eggs through the MOD system in
a liquid carrier would adversely affect the ability of
lacewing eggs to hatch. Besides water, the 5% ethyl
alcohol also was tested as a potential method to dis-
infect the surface of the eggs. Results indicated that
egg hatch percentages were not signiÞcantly affected
among treatments. In many mass rearing facilities that
rear green lacewings, the eggs are not normally surface
286 J
OURNAL OF ECONOMIC ENTOMOLOGY Vol. 100, no. 2
sterilized. Seventy percent ethyl alcohol is commonly
used to surface sterilize insects (Suh et al. 2004) and
bench area (Anonymous 2005). In our experiment, we
used 5% ethyl alcohol. Our results showed that 5%
ethyl alcohol may be used as a surface sterilizing agent
for lacewing eggs. For that purpose, we need to con-
duct further testing to be able to determine the ef-
fectiveness of such solution against microorganisms.
The original spray manifold tubes for the MOD
system were 0.226 cm for each tube. Our preliminary
experiment (data not presented) showed that smaller
tubes allowed “jets” of egg suspension coming out of
the tubes rather than a series of large egg suspension
droplets. Therefore, the MOD system was modiÞed by
insertion of smaller tubes inside the original tubes to
reduce the diameter to 0.158 cm per tube.
The salt shaker data were collected to see whether
there were substantial needs to develop an improved
egg delivery system and as a comparison. The variables
for the MOD system were set to yield a desire number
of one to four eggs per cell with an expected average
of 2.5 eggs per cell. The results showed that the av-
erage number of eggs per cell was 1.2 eggs per cell with
61.9% of cells containing the desired number of one to
four eggs per cell. Although the salt shaker method
obtained higher average number of eggs per cell (i.e.,
2.83 and 2.80 eggs per cell), the mean percentages of
cells containing one to four eggs per cell were lower
(i.e., 40.8 and 52.1%, respectively) compared with that
of the MOD system. The MOD system provided an
improved and more consistent method to distribute
lacewings eggs into each Verticel unit where the range
was zero to eight eggs per cell; in comparison, the
ranges were zero to 15 eggs per cell and zero to 20 eggs
per cell distributed with the salt shaker method.
Each Verticel larval rearing unit consisted of 23
rows. Based on the size of Verticel rearing unit we
used (15.2 by 30.5 cm), there were 46 cells in each row.
The number of eggs desired in each cell was one to
four eggs per cell. Therefore, the expected total eggs
delivered by each tube for 46 cells should be 46Ð184
eggs. We decided ⱕ25 eggs in each row of a Verticel
unit was an arbitrary number indicating there were
clogging problems. Our results indicated that several
Table 1. Number of green lacewing eggs per cell distributed
in the Verticel larval rearing units by using the MOD system
No. eggs/cell No. cells %
0 2,158 37
1 1,660 28.60
2 1,053 18.20
3 568 9.80
4 318 5.50
5 27 0.47
6 10 0.17
7 1 0.02
8 1 0.02
900
ⱖ10 0 0
Total 5796 100
Average number of eggs per cell* ⫽ 1.20 ⫾ 1.23. Percentage of cells
containing desired no. of eggs** ⫽ 61.90%.
* Mean ⫾ SD from six replicates (i.e., six pieces of Verticel unit).
** The desired number of eggs is one to four per cell.
Table 2. Number of green lacewing eggs per cell distributed in the Verticel larval rearing units by using the salt shaker system at two
observation dates
Date 1 Date 2
No. eggs/cell No. cells % cells No. eggs/cell No. cells % cells
0 199 30.90 0 292 32.48
1 103 15.99 1 182 20.25
2 74 11.49 2 127 14.13
3 56 8.70 3 92 10.23
4 34 5.28 4 68 7.56
5 54 8.39 5 38 4.23
6 39 6.05 6 35 3.89
7 25 3.88 7 19 2.11
8 25 3.88 8 10 1.11
9 7 1.09 9 14 1.56
10 9 1.40 10 7 0.78
11 6 0.93 11 3 0.33
12 7 1.09 12 5 0.56
13 1 0.15 13 1 0.11
14 2 0.31 14 3 0.33
15 3 0.47 15 0 0
16 1 0.11
17 0 0
18 0 0
19 1 0.11
20 1 0.12
Total 644 100 Total 899 100
Avg no. of eggs per cell* ⫽ 2.83 ⫾ 3.13 Avg no. of eggs per cell* ⫽ 2.22 ⫾ 2.72
Percentage of cells containing desired no. of eggs** ⫽ 40.8% Percentage of cells containing desired no. of eggs** ⫽
52.1%
* Mean ⫾ SD from six replicates (i.e., six pieces of Verticel unit).
** The desired number is one to four eggs per cell.
April 2007 WOOLFOLK ET AL.: DISTRIBUTION SYSTEM FOR Chrysoperla EGGS 287
distributions caused lower than an average of 25 eggs
in the Verticel cells (Table 3). We observed that some
clogging problems occurred during egg delivery due
to the smaller size of the tubes. Possible explanations
for the clogging are as follow: 1) In the mass rearing
facility, lacewing adults are placed collectively into
3-liter cylindrical cardboard cartons covered with or-
gandy cloth. Female adults lay thin layers of eggs on
the organdy cloth. Every other day, lacewing eggs are
harvested using a soft brush. While brushing the eggs,
small pieces of the organdy cloth would come loose
and mix together with the harvested lacewing eggs.
This piece of organdy cloth may have clogged the tube
and inhibited the eggs to be delivered smoothly in
each Verticel unit. 2) Lacewing eggs are laid singly
with attached slender stalks by the female adults.
These stalks also may have caused some clogging prob-
lems in the distribution tubes.
As described previously, the current MOD system
includes a conveyor belt that is solid (Fig. 1). How-
ever, the Verticel rearing unit is made from an S shape
light cardboard that is glued together. When the MOD
system was run to distribute lacewing eggs into each
cell of the Verticel unit, excess water caused some
standing water on the conveyor belt and conse-
quently, the Verticel unit became too wet.
Some improvements will need to be made for the
MOD system to be able to function optimally as an
insect egg dispenser system. Those improvements will
include a replacement of solid conveyor belt with a
metallic or highly perforated belt that will allow the
carrier liquid to pass through the organdy cloth at the
bottom of each Verticel larval rearing unit while re-
taining the eggs. During the initial run, the MOD
system will need to be run long enough with liquid
carrier only to remove or wash away any debris or
other pieces that may cause clogging problems. To
reach the goal of having one to four eggs per cell with
an expectation of 2.5 eggs per cell, the concentration
of eggs in liquid carrier (before passing through the
system) should be increased. All of the above-men-
tioned issues warrant further study.
With the cost less than $3,500, an MOD system can
be built that consists of the following components: 1)
reservoir (Fisher or other laboratory suppliers), $20 Ð
50; 2) peristaltic pump Masterßex standard drive
model P-07520-10 (Cole-Palmer Instrument Co.),
$570; 3) Masterßex easy load pump head model
P-70518-00 (Cole-Palmer Instrument Co.), $200; 4)
custom-made multiple oriÞce manifold, $600 Ð 800; 5)
Dorner conveyor belt model 2100-0804-01/02 (Dor-
ner), $800; 6) bottom mounted end drive for conveyor
belt model 2320-09A1-1414 (Dorner), $200; 7) 60:1
ratio air gear motor model 22Ð 060R-0005-8 (Dorner),
$600; and 8) magnetic stirrer (Fisher or other labo-
ratory suppliers), $165 and up. The system also would
improve the efÞciency with which eggs are distributed
within the Verticel larval rearing units and reduce
labor costs associated with this speciÞc operation. At
the belt speed of 3.8 cm/s, the system could Þll one
Verticel larval rearing unit (unit size 15.2 by 61.0 cm)
every 16 s, or 1,575 Verticel rearing units a 7-h pro-
duction day. With each larval rearing unit producing
⬇2,000 adults, ⬇3.1 ⫻ 10
6
adults would be produced
per day. Individual green lacewing females normally
produce 500 Ð1,000 eggs during a 30-d oviposition pe-
riod (Hagen and Tassan 1970, Albuquerque et al. 1994,
Chang et al. 1996).
The average numbers of eggs per cell of Verticel
unit delivered by MOD system can potentially be
increased by 1) increasing the egg concentration in
the eggÐwater suspension, 2) lowering the conveyor
belt speed, and 3) increasing the ßow rate of suspen-
sion through the 23 distribution tubes. When we dou-
ble the numbers of eggs per cell (i.e., 1.2Ð2.4 eggs per
cell), we also expect the number of cells that contain
no eggs to decrease below the current 37% level (Ta-
ble 1). We expect cell number to decrease to ⬇15Ð20%
(half of the current level). Using data in Tables 1 and
2, we developed a hypothetical example of a mass
rearing facility that would use 100,000,000 lacewing
eggs to be delivered by salt shaker method and MOD
system. The salt shaker method and MOD system
would deliver 26,800,000 and 52,300,000 eggs, respec-
tively, being available to be sold. In this example,
assuming 100% egg survival, the MOD system returned
52.3% eggs to larvae whereas the salt shaker method
returned 26.8%. The total number of insects produced
may be able to be increased by altering either the
concentration of eggs in the suspension, the conveyor
Table 3. Total number of green lacewing eggs distributed by each distribution tube of MOD system
Replicate
Total no. of eggs distributed from tube no.
a
1234567891011
1 96 1 75 16 72 66 57 55 86 70 4
2 4169653737536655536543
3 3345304555454658674235
4 74 2 71 51 48 61 50 40 50 52 49
5 5538117640375360865810
6 55 3 57 52 52 64 56 45 65 62 4
Mean
b
⫾ SD
59 ⫾ 22.92 26 ⫾ 28.58 52 ⫾ 25.49 46 ⫾ 19.71 51 ⫾ 12.52 54 ⫾ 11.52 55 ⫾ 6.86 52 ⫾ 7.88 68 ⫾ 15.54 58 ⫾ 10.01 24 ⫾ 20.51
Numbers highlighted in light grey represents cell of Verticel rearing units with totals of ⱕ25 lacewing eggs.
a
MOD System consists of 23 tubes in its manifold; total numbers of eggs per tube represent total number of eggs distributed into 42 rows
of Verticel rearing unit per replicate.
b
Mean represents average total number of eggs per tube of the MOD system.
288 JOURNAL OF ECONOMIC ENTOMOLOGY Vol. 100, no. 2
belt speed, and/or the ßow rate of the suspension. The
MOD system has deÞnitely shown a potential to be
used in commercial insectary and/or an insect mass
rearing facility. The cost of lacewing eggs production
can certainly be reduced with more automation and
higher volume production, which can be accom-
plished by using the MOD system.
Acknowledgments
This project would not have been completed without the
assistance from the following people: Dan Harsh (USDAÐ
ARS, Mississippi State University) for constructing the man-
ifold and mounting brackets used on this project; Brenda
Woods (BCMRRU, USDAÐARS, Mississippi State Univer-
sity) for counting the eggs in the Verticel cells for control;
Delphine Harris (BCMRRU, USDAÐARS, Mississippi State
University) for providing portion of C. rufilabris eggs used for
this project; Allen Cohen (Insect Diet and Rearing Research,
LLC, Tucson, AZ) and Synthia Penn (BeneÞcial Insectary,
Redding, CA) for valuable input; and Frank Davis, Clarence
Collison, and Amanda Lawrence (Department of Entomol-
ogy and Plant Pathology, Mississippi State University) for
comments on the earlier version of this manuscript. This
paper is Mississippi Agricultural and Forestry Experiment
Station contribution no. J-10990.
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