Group Title: Journal of Economic Entomology, 93 (5). pp. 1452-1458.
Title: Effect of trap size, placement, and age on captures of Blueberry Maggot Flies (Diptera: Tephritidae)
Full Citation
Permanent Link:
 Material Information
Title: Effect of trap size, placement, and age on captures of Blueberry Maggot Flies (Diptera: Tephritidae)
Series Title: Journal of Economic Entomology, 93 (5). pp. 1452-1458.
Physical Description: Book
Creator: Liburd, Oscar E.
Polavarapu, Sridhar
Alm, Steven R.
Casagrande, Richard A.
Affiliation: University of Florida -- Entomology and Nematology Department
Publication Date: 2000
Subject: Diptera   ( lcsh )
 Record Information
Bibliographic ID: UF00083959
Volume ID: VID00001
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.


This item has the following downloads:

UF00083959 ( PDF )

Full Text


Effect of Trap Size, Placement, and Age on Captures of Blueberry
Maggot Flies (Diptera: Tephritidae)


Department i .. ... i. Center for Integrated Plant Systems, Michigan State University, East Lansing, MI 48824

J. Econ. Entomol. 93(5): 1452-1458 (2000)
ABSTRACT Ammonium acetate and protein hydrolysate baited and unbaited green spheres (3.6,
9.0, and 15.6 cm diameter) were evaluated for effectiveness in capturing blueberry maggot flies,
RhBagoletis mendax Curran. Early in the season, baited spheres (9.0 cm diameter) captured signif-
icantly more R. mendax flies than spheres of 3.6 and 15.6 cm diameter. As the season progressed, the
differences in trap captures became less pronounced among the 3.6-, 9.0-, and 15.6-cm-diameter
spheres. In other experiments, the effects of trap positions and age on captures of blueberry maggot
flies were assessed. Traps were positioned 15 crm above the bush canopy, 15 cm inside the canopy
(from top of the bush), and 45 cm from the ground. Traps placed within the canopy captured 2.5
and 1.5 times as many flies compared with traps placed above the canopy and 45 cm from the ground,
respectively. When I t: Pherocon AM boards and green sphere traps were allowed to age
in field cages. freshly baited (0d) yellow sticky boards captured i .... i ... i i. I .. maggot
flies than boards aged for 11, 28, and 40 d, respectively. No significant differences were observed
among boards aged for 11, 28, and 40 d. However, when baited 9-cm sticky spheres were aged in field
cages, therere re no significant differences between freshly baited spheres and spheres aged for 11
and 28d c ** -i J.1- .. 1 40 d differed significantly from freshly baited ones. The study
demonstrated that the baited 9-cm-diameter sphere was more effective in capturing blueberry
maggot flies than spheres of 3.6 and 15.6 cm diameter. When this trap is deployed in the center of
the bush canopy 315 cm from the top of the bush, it is attractive and accessible to R. mendax flies.
The data also indicated that a baited 9-cm sphere has a longer effective life span than Pherocon AM
boards when deployed under the same field conditions.

KEY WORDS highbush blueberries, blueberry maggot, sphere size, trap position

THE BLUEBERRY MAGGOT 11 Rhagoletis mendax Curran,
is the key pest infesting commercially grown blueber-
ries Vaccinium L. spp. in eastern United States (Liburd
et al. 1999) Adult eclosion is synchronized with host
fruit maturation. Flies detect fruits on the basis of
physical characteristics, such as fruit shape, color, and
size (Prokopy and Bush 1973, Diehl and Prokopy
1986). Gravid females oviposit into susceptible fruits
(Liburd et al. 1998a) and lay down deterring phero-
mones, which discourage other females from ovipos-
iting into infested berries (Prokopy et al. 1976).
To date, the most effective tactics developed for
detecting the presence of the adults include baited
Pherocon AM :1. sticky boards (Prokopy and Coli
1978) and green and red spheres (Liburd et al. 1998b).
Yellow boards have been used most extensively for
monitoring, but recent evidence suggests that spheres
may be more useful later in the season when flies are
mature and berries are in a susceptible state (Liburd
et al. 1998a, Liburd and Stelinski 1999).

Blueberry and Cranberr Research Center, 125 Lake Oswego
Road, Rutgers University, Chatsworth, NJ 08019.
2 Department of Plant Sciences. University of Rhode Island, King-
ston, RI 02881.

In an experiment to determine the most effective
trap for monitoring blueberry maggot flies, Prokopy
and Coli (1978) cornpared sticky 3.5- and 7.5-cm-
diamreter red spheres and found that significantly
more R. mendax flies were attracted to spheres of 7.5
cm diameter. They accounted for this by suggesting
that the 7.5-cm-diameter sphere .." i.. a super-
normal fruit-type stimulus for the blueberry maggot
fly. Earlier, Prokopy (1977) reported that this size was
,._*.,,i,.. ...... ... to the apple : ....... R .
pomonella (Walsh), than smaller spheres of 1.5 or 3.4
cm diameter. However, early in the season large
spheres measuring 23 cm in diameter caught as many
R. ... '-.. flies as spheres of 7.5 cm in diameter.
Over the last two decades, there have been several
studieson optimal positioning of -i .
capture of R. pomnonellaflies (Reissig 1975, Drurnond
et al. 1984). Reissig (1975) found that trap height
above the ground and trap distance from the outside
edge of the canopy significantly affected captures of R.
pomnonella flies, whereas compass direction within the
canopy did not impact total trap catch. In another
study, Drummond et al. (1984) found that traps po-
sitioned within the vicinity of apple fruits at a distance
of 0.25 0.5 m caught .- : .*. : more apple maggot
iI.. than other trap positions.

0022-0493/00/1452-1458$02.00/0 ) 2000 Entomological Society of America


In lowbush V angustifolium Aiton blueberry plant-
ings, Neilson et al. (1984) found that 8.5-cm-diameter
dark red sticky spheres placed within the canopy cap-
tured i". I -i- ... R. mendax flies than Pherocon
AM boards deployed vertically or at a 45 angle. How-
ever, when spheres were placed above the canopy
there were no significant differences in trap captures
between Pherocon AM boards and the 8.5-cm-diam-
eter red spheres.
Chemical cues also affect total trap captures among
several species of tephritids. Gow (1954) evaluated
various baits containing ammonia and protein hydro-
lysates and found that when protein hydrolysates were
protected from bacterial decomposition, their attrac-
tiveness to the orien tal fruit fly, Dacus dorsalis Hendel,
increased. Later, Bateman and Morton (1981) studied
the role of proteinaceous baits including ammonia on
the fruit fly Dacus tryoni (1 _-_ .-1 and concluded
that ii .. stimulation was directly responsible for
the attraction of these il.. to the baits. More recently,
Jones (1988) placed ammonium baited Pherocon AM
traps in a weather shelter for different periods (before
field deployment) and caught ... fewer R.
S. flies on traps aged for 9 d compared with
freshly baited traps. He identified the loss of ammonia
as a principal factor responsible for the significant
drop in fly captures. In a more contemporary study,
Liburd et al. (1998b) showed that ammonia and pro-
tein hydrolysate were more important than trap shape
and color in attracting blueberry maggot flies.
In blueberries, there is zero tolerance for maggot-
infested fruits. Therefore, traps need to be sensitive
early in the season to detect R. mendax flies. The
objectives of this study were to evaluate three sizes
and :.. i: .. of green sphere traps to determine their
effects on captures of blueberry maggot flies. In ad-
dition, we evaluated aged traps versus freshly baited
traps to determine longevity of lures for captures of
blueberry maggot flies under field conditions.

Materials and Methods
I ff I .'*-. .i,. ie Size on Trap Captures. Research in
1997 was designed to evaluate ti... :: : of sphere size
on captures of blueberry maggot flies. Three experi-
ments were conducted at two sites. Research plots
were located at a 2-ha highbush blueberry V corym-
bosum planting of 'Berkley' and 'Collins' located in
West Kingston, RI, and at a 3-ha planting of'Bluecrop'
located in J .. .... 1i: NJ.
The experimental design was a randomized com-
plete block (I. .1 by variety) with four or five
replicates. In all three experiments, three different
sphere sizes were evaluated. These included a3.6-erm-
diameter table ..... I. I: (Franklin Sports, Stoughton,
MA), 9.0-cm-diameter sphere trap (Great Lakes in-
tegrated pest management (IPM), Vestaburg, MI),
and 15.6-cm-diameter volley ,il (Reagent Sports,
Hauppauge, NY). All of the spheres used in the ex-
periments were first spray-painted with premium
Rust-Oleum Green no. 7435 (Rust-Oleum, Vernon
Hills, IL), then with 197A111 Shamrock green (ACE

Hardware, Kensington, IL). The 3.6-, 9.0-, and 15.6-
cm-diameter spheres were coated with 2,13, and 38.5 g
of Tangle-Trap (The Tanglefoot Company, Grand
Rapids, MI), respectively. All baited spheres used in
our experiments received 1 g of ammronium acetate
(Aldrich, Milwaukee, WI) and 0.5 g protein hydroly-
sate (Sigma, St. Louis, MO), regardless of sphere size.
Thirteen grams of Tangle-Trap with 1 g ammonium
acetate and 0.5 g protein hydrolysate was used as a
standard for comparison because Liburd et al. (1998b)
showed this to be an effective baiting mixture for
monitoring the blueberry maggot fly. The ammonium
acetate and protein hydrolysate were mixed into the
Tangle-Trap before application to the spheres. Un-
baited spheres received only Tangle-Trap (2, 13, and
38.5 g with respect to the sphere size).
In Rhode Island, the sphere size experiment was
established on 7 July and finished 15 August. Six treat-
ments consisting of three baited (3.6, 9.0, and 15.6 cm
diameter) and three unbaited (3.6, 9, 90 and 15.6 cm
diameter) spheres were evaluated. Traps were spaced
-15 m apart with 20 m between blocks. In New Jersey,
the experiments were established on 19 July and con-
cluded 12 August. One of the experiments was con-
ducted using only baited spheres and the other ex-
periment was conducted using unbaited spheres.
Three treatments (3.6, 9.0, and 15.6 cm diameter)
were evaluated in both experiments. Sphere traps
were spaced 25 m apart with 20 m between blocks. In
all three experiments, sphere positions were rotated
on a weekly basis to avoid field position effects.
'. i,.-;,,_ In Rhode Island and New Jersey, traps
were checked two times per week and E, I : were
counted and removed. In addition, flies were sexed
once per week in the Rhode Island experiment.
Based on the results of our 1997 field studies, ex-
periments in 1998 were designed to evaluate sphere
placements or positions in highbush blueberry V
corymbosum L. plantings.
Effect of Trap Position on Captures. Experiments
aimed at evaluating sphere positions were located in
Chatsworth, NJ, and Fennville, MI. The traps used in
these experiments were 9-cm-diameter green spheres
(Great Lakes IPM, Vestaburg, MI). Each sphere was
coated with 13 g of Tangle-Trap and baited with 1.0 g
of ammonium acetate and 0.5 g of protein hydrolysate
(1,iburd et al. 1998b). In New Jersey the experiment
was established on 7 July and concluded 28 July. In
Michigan the experiment was established on 14 July
and finished 13 August.
The experimental design was a completely random-
ized block with five replicates. In New Jersey, sphere
traps were hung within the cultivar Bluecrop and
spaced 25 m apart with 20 m between blocks. In Mich-
igan, traps were spaced 30 m apart with 45 m between
blocks in blueberries. In both locations, three
different trap positions were evaluated. The positions
consisted of placing traps (1) 15 cm above the bush
canopy, (2) 15 cm inside the canopy (from the top of
the bush), and (3) 45 cm from the ground. At both
sites, bushes were 1.5 1.8 m in height. Trap positions

October 2000


were rotated weekly, checked two times per week and
adult flies were counted and removed.
Effect of Trap Age on Captures. Two different lo-
cations were used to evaluate the ... *, ,.~
with respect to age. Research plots were located at (1)
the University of Rhode Island East Farm Experimen-
tal Station located in Kingston, RI, (2) at a commercial
blueberry farm located in Douglas, MI.
In Rhode Island, unbaited Pherocon AM yellow
boards obtained from Trece (Palo Alto, CA) were
used for evaluation studies. Unbaited Pherocon AM
S. II boards were coated with 13 g of Tangle Trap,
1 g ammonia acetate, and 0.5 g protein hydrolysate on
the same day they were deployed in field cages. In
Michigan, green spheres (9 cm diameter) were used
for the evaluation studies. Spheres were coated with
the same baiting mixture (13 g of Tangle Trap, 1 g
ammonia acetate, and 0.5 g protein hydrolysate) as
Pherocon AM 'i. boards. Immediately after
spheres were coated, they were placed into field cages
(60 by 45 by 60 cm) for weathering.
The experimental design was completely random-
ized block (i i.. ..1 I by variety in Rhode Island) with
five replicates. Both yellow boards (Rhode Island) and
green spheres (Michigan) were hung 15 cm above the
canopies of blueberry bushes. In Rhode Island, traps
were spaced 10 m apart with 15 m between blocks of
Bluecrop, 'Bluetta', 'Earliblue', and 'Lateblue'. In
Michigan, traps were hung within the cultivar Jersey
and spaced 15 m apart with 20 m between blocks.
Four treatments (based on duration of exposure in
field cages) were evaluated for effectiveness in trap-
ping blueberry maggot flies. The treatments included
boards (RI) and spheres (MI) that were exposed in
field cages for 0, 11, 28, and 40 d.
.,,,,l;,., Trap positions were rotated weekly to
prevent postional effects. All traps were checked two
times per week and adult i, were counted and re-
Statistical Analysis. Data from all experiments were
square-root transformed (x + 0.5). Data from exper-
iments were subjected to analysis ofvariance: .11 I
by mean separation using the least significant differ-
ence test (SAS Institute 1989). The results were con-
sidered statistically significant when P < 0.05. The
untransformed means and standard errors are pre-
sented in the tables.

Effect of Sphere Size on Captures. In Rhode Island
during the first trapping period (7 23 July), baited
9- ... .1. .... 1., ,.... .1 significantly (F= 3.2;
df = 5, 20; P = 0.03) more blueberry maggot flies than
any other baited or unbaited spheres evaluated in this
experiment (Table 1). The 9-cm-diameter sphere cap-
tured an average of three times as many flies as the
baited 3.6- and 15.6-crm spheres (Table 1) There were
no -,, -.,. -, differences among the other treatments
evaluated in this experiment during this trapping pe-
riod (Table 1).

Table 1. Capture of adult R. mendax flies on 3.6-, 9.0-, and
15.6-em-diameter spheres West Kingston. Rhode Island (1997)

Mean + SEM no. flies per trap
Sphere diameter, cm
7-23 July 28 July-15 Aug.

Baited spheres
Unbaited spheres

9.4 2.3b
28.6 14.3a
9.4 3.9b
4.6 1.9b
8.6 4.7
6.2 3.0b

15.6 4.9bec
26.4 + 5.9ab
31.2 7.6a
5.0 14d
9.4 3.9cd
5.8 + 2.6cd

Means within columns followed by the same letter are not signif-
icantly different, (F 0.05, LSD test). Baited spheres had 1 g
ammonium acetate and 0 5 g protein hydrolysate.

During the second trapping period (28 July-15 Au-
gust) there were no significant differences (P > 0.05)
in trap captures between the baited 9.0- and the 15.6-
em-diameter spheres. Both traps caught ,.i: ...
(F = 7.2; df = 5, 20; P < 0.01) more flies than unbaited
spheres (Table 1). The baited 15.6-cm-diameter
spheres captured ... -i (P < 0.01) more flies
than the baited 3.6-cm-diameter spheres (Table 1).
There was no significant (P > ') difference be-
tween the baited 9.0- and 3.6-cm-diameter sphere
traps (Table 1). Also, there was no significant (P >
0.05) difference among unbaited spheres (Table 1).
Ammonia baited spheres captured significantly
(P < 0.05) more flies than unbaited (Fig. 1). Peak
* :.I .... i, mendax flies on baited spheres occurred
around 28 July 1997 (Fig. 1). Captures of R. mendax
females on baited 15.6-cm green sphere were *
ican ly (P< 0.05) higher than male captures on 28 July
1997 (Fig. 1). We captured four times as many females
as males (Fig. 1).
The results from New Jersey using baited spheres
were very similar to those observed in Rhode Island.
During the first trapping period (19 31 July), the
9-cm-diameter spheres captured significantly (F =
10.6; df = 2, 8; P < 0.01) more blueberry maggot flies
than the 3.6- and 15.6-cm-diameter spheres (Table 2).
On average, the 9-cm spheres captured 2.5 and 3 times
as .... i ... as the 3.6- and 15.6-em-diameter spheres,
respectively (Table 2). During the second trapping
period (1-12 August) there were no significant (P >
0.05) differences among sphere sizes (Table 2).
For unbaited sphere traps, during the first trapping
period the 9-cm-diameter sphere captured signifi-
cantly (F = 5.0; df = 2, 8; P = 0.03) more blueberry
maggot flies than the 3.6-cm-diameter sphere (Table
2). This trap captured three times as many flies as the
3.6-cm-diameter sphere (Table 2). There were no
significant (P > 0.05) differences between the 9- and
15-cm-diameter sphere traps (Table 2). During the
second trapping period (1-12 August), unbaited 15.6-
cm-diameter spheres captured significantly (F = 4.0;
df = 2, 6; P = 0.05) more blueberry maggot flies than
3.6-cr-diameter spheres (Table 2) but not signifi-
cantly more than the 9-cm sphere.
Effect of Sphere Position on Captures. In New Jer-
sey, traps hung within the bush canopy -15 cm from

Vol. 93, no. 5


7.5 -* Male Baited 3.6 cm
-- Female Green Sphere

._D 5 -

-2.5 V

0 f-------------~^

7.5 Male Baited 9.0 cm
- --Female Green Sphere

a 5


7.5 Male Baited 15.6 cm
. -Female Green Sphere

I- a "^ ^
0 *--------------
LI n s i
6 T 4 >

- Male

Unbaited 3.6 cm
Green Sphere

-- Male Unbaited 15.6 cm
Female Green Sphere

Fig. 1. Captures of R. mendax flies on spheres of different size, Kingston, RI (1997)

the top and 15 cm from surrounding foilage captured
significantly (F = 6.2; df = 2, 8; P = 0.02) more R.
men dax flies than traps placed above blueberry bush
canopy (Table 3). Traps placed within the canopy
captured on an average 2.5 and 1.5 times as many flies
than those placed above or 45 cm above ground, re-
spectively (Table 3). There was no significant (P >
i ) ,1ll .. between traps placed below and
within the canopy (Table 3). Similarly, in Michigan,
sphere traps placed within the canopy captured sig-
. ..ii (F= 7.7; df= 2, 8; P = 0.01) more !i. than
those placed either above or below the canopy (Table
3). These traps captured an average of 2.6 and 2.1 times
as many flies as traps placed above and below the
canopy, respectively (Table 3).

Table 2. Capture of adult R. mendax flies on 3.6-, 9.0-, and
15.6-em diameter baited and unbaited spheres in Chatsworth, NJ

Mean SEM no. flies per trap
Sphere diameter, cm
19-31 July 1-12 Aug.
Baited spheres
3.6 93.0 20.1b 54.3 21.3a
9.0 229.8 43.3a 106.4 37.8a
15.6 66.8 12.7b 80.0 14.3a
Unbaited spheres
3.6 8.4 1.6b 1.8 0.6b
9.0 24.4 5 5.9a 4.5 1 2.1ab
15.6 22.8 6.7ab 7.0 .la

Means within columns followed by the same letter are not signif-
icantly different, (P 0.05, LSD test). Baited spheres had 1 g
ammonium acetate and 0.5 g protein hydrolysate.

October 2000



Table 3. Captures of adult R. mendax flies on baited 9-em-
diameter spheres in Chatsworth, NJ. and Fennville, MI (1998)

Mean + SEM no. flies per trap
Trap position New Jersey Michigan
7 28 July 14 July 13 Aug.
15 cmn above canopy 3.8 2.0b 7.4 1.0b
Within bush canopy 9.6 1 2.6a 19.6 2.1a
45 cm above ground 6.4 + 1.7ab 9.0 + 2.6b

Means within columns followed by the same letter are not signif-
icantly different, (P = 0.05, LSD test).

Effect of Trap Age on Captures. Blueberry maggot
11. pressure was higher in Rhode Island than in Mich-
igan (Table 4). In Rhode Island, freshly baited (0-d)
Pherocon AM ii sticky boards captured signifi-
cantly (F = 9.2; df = 3, 12; P < 0.01) more blueberry
maggot flies than traps aged for 11, 28 and 40 d (Table
4). Blueberry maggot adult captures on new traps
averaged 1.6 times as many flies as any other aged traps
evaluated (Table 4). There were no significant (P >
0.05) differences between traps aged for 11, 28, and
40 d (Table 4). A newly baited i: board captured
2.4 times as many flies as a similarly baited trap that was
exposed for 40 d (Table 4).
The results in Michigan using spheres were differ-
ent from those in Rhode Island where II boards
were used. There were significant (F = 4.1; df = 3, 12;
P = 0.03) differences among aged sphere traps. Sphere
traps exposed in field cages from 0 to 28 d captured
significantly (P < 0.05) more flies than baited sphere
traps exposed for 40 d (Table 4). There were no
significant (P > 0.05) differences among :i captures
on sphere traps exposed from 0 to 28 d (Table 4). On
average, sphere traps exposed for 0, 11, and 28 d cap-
tured 2.5t ... .i. II.. i ... ..1 trapsexposedfor
40 d (Table 4).

Sphere Size. Our results showed that early in the
season, the 9-cm-diameter baited sphere caught con-
siderably more blueberry maggot flies than the other
traps evaluated. However, as the season progressed, R.
mendax 1. .. showed no preference between the 9.0-
and the 15.6-cm-diameter baited spheres (during the
second trapping period). One possible explanation for

Table 4. Effects of trap age on captures of blueberry maggot
fly (1998)

Mean SEM no. flies per trap
Treatment (days) P herocon
AM boards Spheres
Rhode Island Michigan

106 18.1a
67.4 20.0bo
46.4 25.5b
43.8 16.9b

23.0 4.8a
23.0 3.2a
23.0 3.a
9.8 2.9b

Means within columns followed by the same letter are not signif-
icantly different, (F = 0.05, LSD test).

these results is that early in the season, ammonia sur-
rounding a 9-crm-diameter sphere is more concen-
trated and hence more attractive to flies than ammonia
emanating from a 15.6-cm-diameter sphere. The con-
centration of ammonia around a 3.6-cm-diameter
sphere is also higher. However, the much .. .1i..
surface area (total surface area of 3.6 cm diameter is
40.7 cm versus254, ..-- 1.. cm-diameter sphere)
limits the effectiveness of this sphere. The reduced
surface area becomes even more important as non-
target insects become trapped on 3.6-erc spheres, re-
ducing landing space for blueberry :r .__. i i,. \ ;the
season progresses and flies become mature, ammonia
becomes less important because mature i.. are less
prone to seek a protein meal. During this period, the
gravid females orient to larger supernormal fruit-type
stimuli. This may account for the greater response of
R. mendax Il.. to the 15.6-cm-diameter spheres later
in the season. Earlier work by Prokopy and Bush
(1973) suggests that fruit size plays an important role
in host selection. Data collected by Liburd et al.
(1998a) also indicates that berry size is one factor,
which influences the percentage of infested fruits.
Other factors, such as availability of suitable fruit for
oviposition, and the interaction of 11 maturity and
fruit color, may have affected R. mendax response to
spheres (Liburd et al. 1998a).
Based on the number of flies caught per square
centimeter, the 9-cm-diameter sphere was the most
::: ... ., trap evaluated in our sphere size experi-
ments. The baited 15.6-cm-diameter sphere trap
caught as many :i,. as the 9-cm-diameter spheres
during the second trapping period. However, the total
surface area of the 9-crm-diameter sphere is 254 crn2,
and when placed against a background it has a cross-
sectional surface area of 64 .. .-. The total surface area
of a 15.6-cm-diameter sphere is 764 .-, and against a
background it displays a cross-sectional surface area of
191 cm2. Although the 15.6-cm-diameter sphere had a
surface area that was three times as large as the 9-er-
diameter sphere, its trap catch was not .,.,:. -.. I
different. Therefore, the 9-cm sphere is a more effi-
cient trap.
The I I cost of using a 15.6-cm-diameter sphere
miay also limit its use in blueberry plantings. In our
experiments, the time spent in coating (with Tangle-
Trap), checking, and cleaning traps was proportional
to sphere size. The average SEM time taken (n = 5)
to coat a 3.6-, 9.0-, or 15.6-em-diameter sphere with
Tangle-Trap was 2.0 0.3, 2.2 0.2, and 4.7 0.2 min,
respectively. The time taken to count and remove flies
in the field was also proportional to sphere size. Dur-
ing the peak trapping period (28 July), the average
_SEM time spent in the field to check each 3.6-, 9.0-,
and 15.6-cm-diameter sphere was 2.0 0.7, 3.5 0.6,
and 5.0 0.4 min, respectively. This indicates that
substantial labor costs may be involved if large scale
trapping with a 15.6-cm-diameter were undertaken.
Trap Positions. Our results showed that sphere traps
placed within the bush canopy were more effective in
capturing blueberry maggot :i. than traps placed
above the canopy. This finding is significant because

Vol. 93, no. 5


the standard sphere deployment tactic for monitoring
blueberry maggot flies usually involves hanging a trap
15 cm above the bush canopy. One hypothesis that
may explain these results is that more flies may be
foraging in the interior of the bush canopy where
adequate shading is available and berries are accessi-
ble for oviposition and mating. This is consistent with
observations made by Reissig (1975) who reported
that traps hung within the canopy and surrounded by
foliage caught significantly more R. ponionella flies
than traps hung in other positions. The higher captures
of R. ponwonella flies within the canopy may also be
caused by shading effects. Prokopy (1972) reported
(during a sunny afternoon) that :, under shady
conditions were more active than those exposed to
direct sun rays. Other findings by Drummond et al.
(1984) indicated that traps surrounded by fruits and
foliage in very close proximity could negatively affect
fly captures because trap visibility maybe obscured by
foliage. Therefore, trimming away foliage (0.25-0.5
m) will increase .1..,,1 and ultimately increase trap
Aged Traps. Our age experiment demonstrated that
in Rhode Island, newly baited (0-d) Pherocon AM
II sticky boards captured ...I. ....I more blue-
berry maggot flies than traps aged for >11 d. The
decline in fly captures after 11 d was probably the
result of lower release rate of ammonia from Phero-
con AM yellow boards as the boards aged. These
results were consistent with Jones's (1988) study that
also found that II Pherocon AM boards aged for
9d .,,i, ..,,' .... ,i i I. i l ... I hoardsagedfor
<5 d. In his study, low release rates of ammonia from
Pherocon AM boards were recorded after traps were
aged for 5 d. He identified the loss of ammonia being
the principal factor j. :- .. 1 1. for the diminished fly
captures. Ammonia is a strong attractant for immature
RI. mendax i..- However, we noticed that when am-
monium acetate is used as the principal bait for mon-
itoring blueberry maggot flies, a large percentage of
nontarget insects are also captured on the traps.
In Michigan, where sphere traps were used for eval-
uation studies, there were no 1.1I .. in blueberry
maggot 11 captures from 0 to 28 d. However, when
sphere traps were aged for 40 d, significantly fewer R.
.. i. .. .. captured. The reason 1. .. was
no change in the ..* "I.** -' of fly captures to spheres
for 4 wk is unknown. Two hypotheses may explain
these results. First, 9-cm-diameter greer. -ph.-c. have
less surface area (total surface area 254 ,. : i ... the
treated section of a Pherocon AM -. -i. board (394
cmr) thereby allowing less volatilization of ammonia
from the Tangle-Trap. Consequently, immature flies
were still attracted to the ammonia even after spheres
were deployed for 4 wk. Jones (1988) also implicated
the large surface area of Pherocon AM boards for the
short longevity of ammonium baits observed in his
study. A second hypothesis is that the dark green
silhouette of the spheres may have been visually at-
tractive to mature blueberry ...... I ..... -
mating and ovipositing sites. Therefore, R. mendax
iI.. continued to visit sphere traps even after the

ammonia was depleted. Unbaited green spheres (sim-
ilar to the ones used in this study) have already been
shown to be attractive to R. mendax flies (Liburd et al.
Our findings have important implications with re-
spect to monitoring R. rmendax populations in blue-
berry plantings. The fact that _.. ... fewer flies
are captured on Pherocon AM boards after 11 d im-
plies that boards are operating at a lower efficiency.
The standard practice in highbush blueberry plantings
in New Jersey and Michigan is to use the same board
for the entire season for monitoring adults (O.E.L. and
S.P., unpublished data). Although our data indicate
that a substantial amount of ammoniais lost after 1 wk,
we recommend that growers who are using Pherocon
AM k. :i. sticky boards change their traps every 3
wk. This would require approximately three changes
during a9-wk blueberry growing season. Growers that
are using green spheres can change their traps after 4
wk requiring only two changes during the same 9-wk
Our study demonstrated that the baited 9-cm-di-
ameter green sphere was a superior trap to 3.6- and
15.6-cm-diameter spheres. The study showed that
when this sphere is deployed in the center of the bush
canopy, it is very attractive to R. nzendax flies. In
addition, the results indicated that ammonium acetate
baited spheres have a longer attractive life span for R.
mendax flies than Pherocon AM boards. Flies appear
to be .. 11 attracted to this 9-cm-diameter sphere
because it depicts a supernormal fruit in an optimum
state of susceptibility.

We thank Heather Faubert. Jessica Kostarides, and Lisa
Tewskbury (University of Rhode Island) for their valuable
assistance on this project. We thank Jill Bockenstette and
Katherine Pettit for their help in making necessary changes
to the manuscript. We also thank Ronald J. Prokopy (Uni-
versity of Massachusetts Amherst) and Rufus Isaacs (Mich-
igan State University) for reviewing earlier drafts of the
manuscript. We thank Jack Partyka for the use of his blue-
berry plantings in Rhode Island. We thank John Wise and the
staff at the Trevor Nichols Research Complex ati i 1
State University for .11 us to use their facilities to
conduct some of our experiments. Special thanks to Paul
Kurz and Robert Holdcraft from the Rutgers Blueberry and
Cranberry Research Center for their help on this project.
Part of this project was funded by NE IPM grant No. 96-
34103-3075 and Michigan Blueberry Growers Coop. This is
contribution No. 3779. RI. Agricultural Experiment Station.

References Cited
Bateman, M. A., and T. C. Morton. 1981. The importance of
ammonia in proteinaceous attractants for fruit flies (Fam-
ily: Tephritidae). Aust. J. Agric. Res. 32: 883 903.
Diehl, S. R., and R. J. Prokopy. 1986. Host-selection behav-
ior differences between the fruit fly sibling species Rhago-
letis pomonella and R. mendax (Diptera: Tephritidae).
Ann. Entomol. Soc. Am. 79: 266-271.
Drummond, F., E. Groden, and R. J. Prokopy. 1984. Com-
i .. *.: O m .1 :..i ...i, ..... oftrapsformon-

October 2000


itoring apple maggot flies (Diptera: Tephritidae). Envi-
ron. Entomol. 13: 232-235.
Gow,P.L. 1954. P. .;. I .. .. ,i, i i"
J. Econ. Entomol. 47: 153 160.
Jones, V. P. 1988. Longevity of apple maggot lures under
laboratory and field conditions in Utah. Environ. Ento-
mol. 17:704-708.
Liburd, O. E., and L. L. Stelinski. 1999. Apple maggot fly
and its ..i. ,, species: physiological and environmental
status. MSU CAT Alert Ext. Bull. 14: 3-4.
Liburd, 0. E., S. R. Alm., and R. A. Casagrande. 1998a.
Si. i j ... of highbush blueberry cultivars to larval
infestation by Rhagoletis mendax (Diptera Tephritidae).
Environ. Entomol. 27: 817-821.
Liburd, O. E., S. R. Alm, R. A. Casagrande, and S. Polavarapu.
1998b. Effect of trap color, bait, shape and orientation in
attraction of blueberry maggot (Diptera: Tephritidae)
flies. J. Econ. Entonol. 91: 243249.
Liburd, O. E., L. J. Gut, L. L. Stelinski, M. E. Whalon, M. R.
McGuire, J. C. Wise, X. P. Hu, and R. J. Prokopy. 1999.
Mortality of Rhagoletis species encountering pesticide-
treated spheres (Diptera: Tephritidae).J. Econ. Entomol.
92: 1151-1156.
Neilson, W. T. A, A. D. Knowlton, and M. Fuller. 1984.
Capture of blueberry maggot adults, :. melndax
(Diptera: Tephritidae), on Pherocon AM traps and on

tartar red dark sticky spheres in lo, i .. .i. i .. .. : i
Can. Entomol. 116: 113 118.
Prokopy, R.J. 1972. Response of apple maggot flies to rect-
angles of different colors and shades. Environ. Entomol.
1: 720 726.
Prokopy, R. J. 1977. Attraction of Rhagoletis flies (Diptera:
Tephritidae) to red spheres of different sizes. Can. En-
tomol. 109: 593-596.
Prokopy, R. J., and G. L. Bush. 1973. Ovipositional reponses
to different sizes of artificial fruit by flies of Rhagoletis
.... : .. A, Ann. Entomol. Soc. Am. 66:927
Prokopy, R. J., and W. M. Coli. 1978. Selective traps for
monitoring Rhagoletis mendax flies. Prot. Ecol. 1: 45-53.
Prokopy, R. J., W. H. Reissig, and V. Moericke. 1976. Mark-
ing pheromones deterring repeated o, 'r i' .i... ..
letis flies. Entomol. Exp. Appl. 20: 170-178.
Reissig, W. H. 1975. Performance of apple maggot traps in
various apple tree canopy positions. J. Econ. Entomol. 68:
SAS Institute. 1989. SAS/STAT user's guide, version 6, 4th
ed., vol. 1. SAS Institute, Cary, NC.

Received for publication 17December 999; accepted i

Vol. 93, no. 5

University of Florida Home Page
© 2004 - 2010 University of Florida George A. Smathers Libraries.
All rights reserved.

Acceptable Use, Copyright, and Disclaimer Statement
Last updated October 10, 2010 - - mvs