Captures of Rhagoletis mendax and R. cingulata (Diptera: Tephritidae)
on Sticky Traps Are Influenced by Adjacent Host Fruit and
Fruit Juice Concentrates
K. S. PELZ-STEINSKI,1- L. J. GUT,1 L. L. STELINSKI,1 0. E. LIBURD1,3 AND R. ISAACS1
Environ. Entomol. 34(5): 1013-1018 (2005)
ABSTRACT Field trapping studies were conducted to determine whether feral blueberry maggot
flies, Rhagoletis mendax Curran, and Eastern cherry fruit flies, R. cingulata (Loew), respond to natal
host-fruit volatiles. Subsequent experiments were conducted to evaluate the potential of using simple
and inexpensive fruit juice concentrate lures to monitor these key pests of blueberries and cherries,
respectively. The presence of ripe blueberries and ripe tart cherries in enclosures that permitted
escape of fruit volatiles .'. ...., increased captures of R. mendax and R. cingulata, respectively,
on adjacent sticky traps compared with traps without ..1.. ,. i.: fruit. R. mendax were not affected by
addition. i 1.. i. concentrate to Pherocon AM traps with or without ammonium acetate. Phero-
con AM boards prebaited with ammonium acetate directly incorporated into the sticky Tangle-Foot
coating were .ii effective as unbaited Pherocon AM boards deployed with separate ammonium
acetate dispensers for monitoring R. mendax. A cherry juice concentrate increased captures of
R. cingulata on unbaited Pherocon AM but not L. i :i traps. In addition, combining cherry juice
concentrate and ammonium acetate on Pherocon AM traps increased captures of R. cingulata
compared with captures on traps with either stimulus alone. Adding ammonium acetate lures to Rebell
traps more than doubled captures of r. cingulala over that on unbaited Rebell traps. Our results show
that feral R. rmendax and R. cingulata flies are attracted to the volatiles emitted from their host fruit
and that this may be exploited to improve monitoring of these important fruit pests.
KEY WORDS .. .... i trapping, blueberry maggot fly, cherry fruit fly, host fidelity
THE BLUEBERRY MAGGOT FLY, Rhagoletis mendax Curran,
and the Eastern cherry fruit fly, Rhagoletis cingulata
(Loew), are key pests of blueberries and cherries,
respectively, in the United States. ILarvae of both spe-
cies feed internally, destroying fruit tissues and cre-
ating contamination concerns for producers. Zero tol-
erance for fruit fly infestation necessitates accurate
monitoring of fly presence in crops and prompt de-
ployment of control measures. Broad-spectrum con-
tact insecticides such as organophosphates and car-
bamates have successfully controlled these pests to
date. However, restrictions of these insecticides in
response to the Food Quality Protection Act (Anon-
ymous 1996) have required the evaluation and adop-
tion of newer "reduced-risk" insecticide chemistries
for control of fruit flies (van Randen and Roitberg
1998a b, iburd et al. 2003). These newer compounds
(e.g., spinosad) are effective in controlling Rhagoletis
flies, but often require ingestion rather than contact to
II I~.. ; (Liburd et al. 2003, Pelz et al. ). Accurate
1 Department of Entomology, Michigan State University, East Lan-
sing, MI 48824.
2 Corresponding author: 243 Natural Science, Michigan Stale Uni-
versity, East Lansing, MI 48824 (e-mail: email@example.com).
3 Entomology and Nematology Department, University of Florida,
Gainesville, FL 32611.
timing of insecticide applications is necessary to en-
sure that li. 11 ingest the toxicant before oviposi-
Thus, the cornerstone of an effective fruit fly man-
agement program is reliable and sensitive monitoring
for fly presence. Rhagoletis flies are monitored with
sticky traps that exploit .. i .. .1 ii relevant visual
and ii i stimuli. These attractive cues may mmimic
host foliage, host odor, or natural food sources
(Prokopy and Coli 1978, Prokopy and Hauschild 1979,
Neilson et al. 1981, Duan and Prokopy 1992, Liburd et
al. 1998a, 2001). Pherocon AM boards baited with
release devices containing ammonium acetate are
highly effective monitoring tools for both R. cingulata
and R. mendax (Prokopy and Coli 1978, Liburd et al.
1998a, 2001), as ii as other Rhagoletis species
(Prokopy and Hauschild 1979). Current commercially
available lures for these species consist of plastic dis-
pensers (chargers) containing 2.0 g of ammonium
acetate that are affixed to traps. Additionally, pre-
baited Pherocon AM traps are available, containing
ammonium acetate and protein hydrolysate impreg-
nated directly within the sticky Tangle-Foot coating.
This latter approach is common in Michigan because
of the reduced time required for trap deployment.
0046-225X/05/1013-1018$04.00/0 0 2005 Entomological Society of America
Host-volatile lures have been developed for trap-
ping the apple maggot fly, R. pomonella (Walsh).
These lures provide a more accurate indication of 11
presence than ammonium-based lures (Rull and
Prokopy 2000, Stelinski and Liburd 2002) and show
promise for development of attract-and-kill ap-
proaches to control this pest. A seven-component
blend of apple volatiles was developed through field,
wind tunnel, and olfactometer bioassays to attract
R. pomonella (Fein et al. 1982, Reissig et al. 1982,
Averill et al. 1988). Further experiments showed that
a five-componentblend (Zhang et al. 1999) combined
with a red sphere is the optimal trap for attracting the
maximum number of R. poronella (Stelinski and
Liburd 2002). Before the development of an attractive
synthetic apple volatile lure, Prokopy et al. (1973)
showed that R. pomonella were attracted to the odor
of apples. In contrast, attractive and effective host-
fruit volatiles for use in monitoring R. mendax and
R. cingulata have not been identified. Several blue-
berry volatiles elicit electroantennogram responses
from R. mendax (Lugemwa et al. 1989) and have
shown promise for improving capture of R. mendax
(Liburd 2004). To date, it has not been determined
whether R. cingulaa are attracted to volatiles specific
to their host fruit: cherries.
The objectives of this study were to (1) determine
whether feral R. mendax and R. cingulata are attracted
to natal host-fruit volatiles in the field, (2) determine
the response of mendax and R. cingulata to host-fruit
juice concentrates in an attempt to develop a host-
fruit lure to attract adults of these species, and (3)
determine the optimal method of ammonium acetate
deployment (plastic dispenser versus 1 -0. 1
Pherocon AM boards) for monitoring R. mendax.
Materials and Methods
Field Sites. Experiments in highbush blueberry,
Vaccinium corymbosum L., were conducted at two
sites chosen because of their historically high levels of
R. nendax infestation. The experimental sites were
located at the University of Rhode Island, East Farm
Experimental Station in Kingston, RI, described in
Liburd et al. (1998b) and at an unsprayed blueberry
plantation (cultivar Jersey) in southwest Michigan
(Allegan Co.) described in Stelinski and ,iburd
(2001) and Pelz et al. (2005).
Experiments in tart cherries, Prunus cerassus L., were
conducted in southwest Michigan (Van Buren Co. and
Allegan Co.) and northwest Michigan (Leelanau Co.).
These orchards consisted of unsprayed, mature trees
(cultivar Montmorency) of -4.6-m canopy height.
Response of R. mendax to Odor of Blueberries. This
experiment tested the hypothesis that R. mendax re-
spond to the volatiles of their host fruit: blueberries.
Blueberries or glass marbles of identical size (control)
were placed inside 0.5-cm erosion-mesh bags (Bemis
Co., St. Louis, MO), at 1 kg per bag. Bags containing
ripe blueberries and marbles were placed in collaps-
ible cages ( I 1,. i, Products, Gardena, CA) and hung
-2 m from V. corymbosum bushes that had all fruit
removed. Blueberries (cultivar i and Collins)
were obtained from the Kingston Experimental Sta-
tion described above. Bags were tied (with twist-ties)
to the aluminum frame of the collapsible cage. Cages
were constructed with 32-mesh Lumite-screens (Bio-
Quip Products), ard each cage was 20.3 by 20.3 by
20.3 cm in size. Enclosures were designed to prevent
:,. from contacting fruit, yet allow the emission of
: I stimuli. The top of each cage was lined with
Velcro to allow easy access for i -... i'.-. specific treat-
ments. Four unbaited green sticky-sphere traps used
for monitoring R. mendax were hung 15 cm from the
face of each side of the cage. Treatments were ar-
ranged in a randomized complete block design with
five replicates. Traps were separated by at least 15 m,
with 15 m between blocks. To prevent bias among
treatments, fresh blueberries were replaced in each
cage every 3 d, and cages within blocks were rotated
three times per week.
Response of R. cingulata to Odor of Cherries. This
experiment tested the hypothesis that R. cingulata
respond to the volatiles of their natal host fruit: cher-
ries. For each treatment, 1 kg of fruit (described be-
low) was washed and placed in 0.5-cr cheesecloth
bags. These bags were placed in cylindrical enclosures
(30.5 cm length by 15.2 cm diameter) constructed of
1-mm mesh aluminum window screening. Cheese-
cloth fruit bags were suspended from a wire hanger in
the enclosures with a twist tie such that fruit was
-3 cm from the cage walls. Enclosures were hung
2.1 m above ground. All foliage and cherries within a
0.5 and 2 m radius, respectively, were removed to
prevent competition with caged fruit. These fruit en-
closures were designed to prevent flies from contact-
ing fruit, yet allow the emission of olfactory stimuli. In
addition, the contents within enclosures were not vis-
ible from the outside. Two Pherocon AM traps (Trec6,
Adair, OK) were hung on opposite sides of the fruit
enclosures 3 cm from their edge.
The following treatments were tested: (1) unripe
tart cherries, (2) unripe sweet cherries, (3) ripe tart
cherries, (4) ripe sweet cherries, and (5) no fruit
(control). Ripe fruit was obtained from a local fruit
market, whereas unripe fruit was obtained from re-
search orchards at Michigan State University's Trevor
Nichols Research Complex ,i .... I, MI). Five rep-
licates of each treatment were arranged in a random-
ized block design. Traps were separated by at least
20 m, with 30 m between blocks. R. cingulata ri .
captured on traps adjacent to the enclosures contain-
ing fresh fruit were counted and removed every 3 d.
After each trap inspection, fresh fruit was replaced,
ard treatment positions were rotated within blocks.
Fruit Lure Evaluation: Chemicals and Release De-
vices. These experiments tested the hypothesis that
concentrated solutions of blueberry and cherry juice
are attractive to R. rendax and R. cingulata, respec-
tively. Blueberry and cherry concentrates were ob-
tained from Milne Fruit Products (Prosser, WA). For
the cherry fruit lure, 5% tart cherry concentrate (Brix
68 g sugar/100 ml; lot JEL-02-092-MI). 5% sweet
cherry concentrate (Brix 68 g sugar/100 ml; lot MFP-
Vol. 34, no. 5
PELZ-STELINSKI ET AL.: HOST VOLATILES ATTRACT R. m endax AND R. cingulata
92 074-M3), and 85% water were blended. Because of
the high sugar content, ethanol (5% vol:vol) was also
added to preserve freshness under field conditions.
Milne Fruit Products removed all nonsoluble conpo-
nents, including sugars, from the blueberry concen-
trate; therefore, it was not necessary to add ethanol to
this purified extract. Five milliliters of each fruit con-
centrate was dispensed into 2.5 by 5.0-cm plastic bags
and heat-sealed. A 6.4-cm-long cotton wick was in-
serted into the dispenser before sealing to draw the
concentrate out for release. Fruit concentrate dis-
pensers were attached to the top of traps with 0.6-cm
Captures of flies on traps baited with fruit concen-
trate lures were compared with captures on traps
baited with aimmonium acetate lures, because these
are known to be highly attractive to both R. mendax
(Liburd et al. 1998a) and R. cingulata (Liburd et al.
2001). In treatments where ammonium acetate was
used, plastic 11. dispensers (chargers; Great Lakes
Integrated Pest Management [IPM], 1. i .1.... MI)
were filled with 2 g of solid ammonium acetate (Sigma
Aldrich, St. Louis, MO) immediately before field de-
ployment. A single dispenser was attached to the up-
per corner of the Pherocon AM trap with a II
An evaluation of lures for R. rnendax was conducted
by comparing five treatments in a randomized con-
plete block design with six replicates. The five treat-
rnents were (1) Pherocon AM traps prebaited with
ammonium acetate (2 g) and protein hydrolysate
(0.5 g; Trece) mixed within the sticky Tangle-Foot,
(2) unbaited Pherocon AM traps with a blueberry
concentrate lure, (3) unbaited Pherocon AM traps
with an amrmonium acetate lure, (4) unbaited Phero-
con AM traps with both a blueberry concentrate and
an ammonium acetate lure, and (5) unbaited Phero-
con AM traps (control). Traps were hung at the op-
timum height within blueberry bushes -15 em below
the uppermost canopy and in a vertical orientation on
the south side of the blueberry bushes with foliage and
fruit cleared within a 0.5-m radius (Liburd et al. 2000).
Traps were separated by at least 15 m with 10 m
between blocks. R. rnendax were counted and re-
moved weekly, and treatments were rotated within
each block to account for positional bias. Treatments
and traps were replaced biweekly for an 8-wk period.
Two trapping experiments were conducted to
evaluate lures for R. cingulata. In the first experiment,
Pherocon AM traps were baited with (1) cherry con-
centrate lure, (2) ammonium acetate lure, (3) cherry
concentrate and ammonium acetate lures, or (4)
blank (control). In the second experiment, the four
lure treatments were identical, but they were evalu-
ated t ...- i. i : traps (Great Lakes IPM) rather than
Pherocon AM traps. Rebell traps were used because
these are highly attractive to R. cingulfta (Liburd et al.
2001). The experimental design was a randomized
complete block with six :.1. .:.. for the experiment
conducted with Pherocon AM traps and five. : ...
for the experiment conducted ,: :, 1,. II traps. Traps
were hung vertically on the south side of trees with
Table 1. Season-long captures ofR. cingulata on Pherocon AM
boards hung adjacent to enclosures containing ripe or unripe sweet
or sour cherries in Michigan cherry orchards
chery tye Flies per trap
Ripe tart 216.0 32.5a
Ripe sweet 129.3 31.1b
Unripe tart 97.0 46.9b
Unripe sweet 78.0 8.7e
No fruit (control) 94.7 21.7b
Mean I SEM; means within each column followed by the same
letter are not significantly different (P > 0.05, Fisher's LSD test).
Untransfonned values are shown.
foliage cleared within a 0.5-rn radius of the traps. Traps
were separated by at least 20 m, with 30 m between
blocks. Trap maintenance protocols were identical to
those described for blueberries above.
Statistical Analysis. For each experiment, data from
subweekly trap captures were pooled across the sea-
son for analysis. Data were normalized by square root-
transformation (x + 0.5) '2 and subjected to analysis
of variance (ANOVA). Means separation was con-
ducted using Fisher's least significant :::: ....
(LSD) test (SAS Institute 2000). In all cases, the sig-
nificance level was a < 0.05.
Response of R. mendax to Odor of Blueberries.
Significantly (F = 9.8; df = 1,4; P = 1, !) more flies
were captured on spheres adjacent to collapsible
cages containing blueberries (20.4 4.0) compared
with those placed adjacent to marbles (surrogate blue-
berries; 6.4 1.6), representing more than three-fold
increase in I captures. In addition, .... -..,* (F=
11.8; df = 1,4; P = 0.02) more female R. rnendax were
captured on spheres placed near blueberries (12.0 +
3.2) compared with spheres near marbles (3.0 1.2)
within 1i i. .1 i. cages.
,, t.11 of R. cingulata to Odor of Cherries. Sig-
nificantly (F = 5.3; df = 4,8 P < 0.05) more R. cngulata
were captured on Pherocon AM traps placed adjacent
to cages containing ripe tart cherries compared with
the other treatments (Table 1), representing a more
than two-fold increase in fly captures. There were no
significant differences between the :. i: ..t reat-
ments: ripe sweet, unripe tart, and no fruit (control;
Table 1). Treatments with unripe sweet cherries
caught significantly fewer R. cingulata than the control
Fruit Lure Evaluation: R. mendax Experiment.
Significantly (F = 10.7; df = 4,20; P < 0.05) fewer
R. mendax were captured on Pherocon AM boards
baited with blueberry concentrate lures compared
with any of the treatments containing ammonium ac-
etate (Table 2). In addition, fly captures on traps
baited with the blueberry concentrate lures were not
significantly (P > 0.05) different from those on un-
baited Pherocon AM traps. Similar numbers of
1R. mendax were captured on Pherocon AM traps con-
Table 2. Effect of different lure formulations on season-long
captures of adult R. mendax on Pherocon AM traps
Lure type Flies per trap
Ammonium acetate (dispenser) + 66.3 12.2a
Ammonium acetate + protein hydrolysate 63.0) 1 1.8a
(impregnated in adhesive)
Ammonium acetate (dispenser) 58.2 + 15.0a
Blueberry concentrate 18.8 4.9b
None (control) 15.5 2.9b
Mean I SEM means within each column followed by the same
letter are not significantly different (P > 0.05, Fisher's LSD test).
Untransformed values are shown.
training ammonium acetate lures alone and ammonium
acetate lures combined with blueberry essence lures
Fruit Lure Evaluation: R. cingulata Experiment.
,." ... .- (F = 9.7; df = 3,15; P < 0.05) more
R. cingulata were captured on Pherocon AM traps
baited with ammonium acetate and cherry concen-
trate lures combined than were captured on Pherocon
AM traps containing the cherry concentrate lure alone
(Table 3). However, captures of R. cingulata on Phero-
con AM traps baited with either the cherry concen-
trate or ammronium acetate lures alone were not sig-
*.i; .... different (Table 3). All treatments captured
...ii :.i1 (P < 0.05) more R. cingulata than un-
baited Pherocon AM traps (Table 3). Although there
was no significant (P > 0.05) difference between
mean fly captures on Pherocon AM boards baited with
the combination of cherry concentrate and ammo-
nium acetate lures and the ammonium acetate lures
alone, the former treatment captured -30% more flies
than the latter (Table 3).
The response of R. cingulata to the same lure treat-
ments using Rebell traps differed from that observed
with Pherocon AM boards. Significantly (F = 9.8: df =
3,12 P < ) fewer flies were captured on :. i i
traps baited with cherry concentrate lures than were
captured on traps baited with ammonium acetate lure
treatments (Table 3). The addition of a cherry con-
centratere]ure to the Rebell trap did not increase fly
captures relative to unbaited Rebell traps (Table 3). In
addition, there was no significant (P < 0.05) differ-
ence between captures ofR. cingulata on i.. i. i: traps
containing ammonium acetate and ammonium acetate
Table 3. Effect of different lure formulations on season-long
captures of adult R. cinguirta on Pherocon AM and Rebell traps
Flies per trap
Pherocon AM Rebell
Ammonium acetate + cherry 51.7 9.4a 43.6 9.2a
Ammonium acetate 37.2 + 9.9ab 32.8 9.9a
Cherry concentrate 28.7 5.1b 16.0 3.4b
None (control) 15.8 4.5c 17.4 4.8b
Mean SEM means within each column followed by the same
letter are not significantly different (P > 0.05, Fisher's LSD test).
Untransformed values are shown.
plus cherry concentrate lures (Table 3). At least twice
as many flies were captured on 1.- : II traps baited
with either of the ammonium acetate treatments than
on the other treatments evaluated (Table 3).
Our results indicate that feral R. mendax and R.
cingulata flies are attracted to the volatiles emitted by
their respective host fruit. -t..'-. .11,, ripe blue-
berries and ripe tart cherries increased captures of
R. mendax and R. cingulata, respectively, on adjacent
sticky traps. Host races of the related R. pomonella are
attracted to exact blends of volatiles given off by their
specific host fruit (Linn et al. 2003, Nojima et al. 2003a,
b). Such volatiles mediate long-range attraction of
R. pomonella to the location of host fruit (i, .i .-.. et
al. 1973). Within the genus Rhagoletis, mating, ovipo-
sition, and larval development are strictly associated
with species-specific, unabscised host fruit. This asso-
ciation between the location of larval development
and the location of mating and oviposition is referred
to as "host fidelity" and is believed to impart a pre-
mating isolation mechanism for symrpatric speciation
(Feder et al. 1994, Feder 1998). Our data provide
direct evidence for host-fruit association mediated by
i cues for two more species within the fruit-
infesting Rhagoletis sibling complex.
Ripe cherries increased captures of R. cingulata on
..1; .. i. :. whereas unripe fruit did not (Table 1).
This suggests that cherries may become maximally
attractive to R. cingulata at a specific phenological
stage, perhaps increasing chances of successful ovi-
position and larval fitness. Alternatively, the ripe
cherry treatments may have attracted more flies given
that store-bought fruit released a greater amount of
volatiles after a period of aging compared with freshly
picked unripe fruit.
Increased captures of R. inendax on traps adjacent
to ripe blueberries observed in :1 : ,,..I corroborates
previous work suggesting that this species responds
to host fruit volatiles. As measured by electroanten-
nograms (EAGs), R. imendax are more sensitive to fruit
extracts of blueberries than that of apples, indicating
that antennal sensitivity may be adapted to the spe-
cies-specific host (Frey and Bush 1990, Frey et al.
1992). Furthermore, hybrids of R. mendax and
R. potmonella exhibit significantly reduced EAG re-
sponses to host odor compounds compared with pa-
rental lines, suggesting host-odor perception is an im-
portant factor in species isolation (Frey and Bush
1996). In addition, the two species have evolved di-
vergent egg-laying responses to chemical stimuli on
the fruits of their respective hosts (Bierbaum and
Bush 1990). 'It.. ,.. II, IR. mendax lay more eggs
compared with R. powonella when stimulated by ex-
tracts from blueberries, whereas the opposite is true
for R. pomonella.
Both R. Rendax and R. cingulata are key pests of
their respective host fruit (Liburd et al. 1998a, 2001;
Teixeira and Polavarapu 2001). Visual and olfactory
traps are used to monitor these pests and time insec-
Vol. 34, no. 5
PELZ-STELINSKI ET AL.: HOST VOLATILES ATTRACT R. mendax AND R. cingulata
ticide applications. Ammonium acetate is known to be
highly attractive to Rhagoletis species, but this lure is
nonselective resulting in substantial nontarget insect
captures predominated by various Diptera (Stelinski
and Liburd 2002). Lack of selectivity reduces moni-
toring effectiveness because traps become inundated
with nontarget insects, removing effective trapping
surface area. This increases labor input, given the need
for biweekly trap cleaning and replacement (Stelinski
and liburd 2002) and the need to sort through flies to
find the target pest species. Fruit volatile lures devel-
oped for R. -': (Zhang et al. 1999) are highly
selective to this species and perform .....i :,,ii bet-
ter than ammonium acetate lires (Stelinski and
Liburd 2002). Developing highly attractive and selec-
tive monitoring lures for both R. mendax and R. cin-
gulata would represent an important advance for man-
agement of these species.
These results show the potential for developing
synthetic host-fruit lures for these Rhagoletis flies,
given that both species are attracted to their natal host
fruit. Our initial attempt to develop a simple and in-
expensive fruit-based lure using fruit concentrates
did not prove highly effective. The lack of responseby
R. mendax to the blueberry concentrate hlre suggests
that ripe blueberries give off a specific blend of vola-
tiles, which was not preserved in the blueberry juice
concentrate we evaluated. For R. cingulata, there was
evidence that the cherry juice concentrate was at-
tractive when deployed with Pherocon AM boards,
but this lure was not more attractive than ammonium
acetate. In addition, combining the cherry concen-
trate lure with an ammonium acetate lure i., I I1
captures on Pherocon AM traps relative to similar
traps baited with either lure type deployed individu-
ally. However, the cherry concentrate lure did not
increase captures of R. cingulata when evaluated with
Rebell traps. These traps provide a highly attractive
visual stimulus to cherry fruit H species and capture
more cherry fruit flies than ammonium acetate baited
Pherocon AM boards (Liburd et al. 2001). Thus, the
extraordinary visual attractiveness of these traps may
have r ... i l. response, precluding further stim-
ulation by i: ..: cues.
Ammonium acetate is currently the standard lure
used for monitoring R. mendax and R. cingulata
(Liburd et al. 1998a, 2001). Although this compound
is nonselective, it is a highly potent food-based at-
tractant (Liburd et al. 1998a, Stelinski and Liburd
2002). Our results showed that Pherocon AM boards
prebaited with ammonium acetate directly impreg-
nated into the sticky Tangle-Foot coating were just as
effective in capturing R. mendax as were initially un-
baited Pherocon AM boards with separately attached
ammonium acetate dispensers (Table 2). Given that
the former trap type is easier to ..- II. and deploy in
the field, we recommend using prebaited Pherocon
AM boards when monitoring R. mendax with ammo-
nium acetate. In addition, our results showed that
adding an ammonium acetate lure to a Rebell trap
more than doubled captures of R. cingulata compared
with captures on unbaited traps (Table 3). Rebell
traps deployed without bait are highly attractive and
effective traps for both R. cingulata and the black
cherry f .,, :i ,R. fausta (Osten Sacken) (Liburd et al.
2001). The addition of ammonium acetate lures to
these traps may improve their monitoring sensitivity
and practicality as attract-and-kill devices.
The response of l. mendax and R. cingulata to ripe
blueberries and ripe tart cherries, respectively, sug-
gests an odor-mediated interaction between these in-
sects and their host fruit. Future experiments should
focus on elucidating how sexual maturity of flies af-
fects the behavioral response to host fruit. These find-
ings open the I- for identification of the spe-
cific volatile blends mediating this attraction. This has
been recently completed for R. pomonella host races
(Linn et al. 2003, Nojima et al. 2003a, b). Future work
should focus on the collection, isolation, and identi-
fication of headspace volatiles associated with unhar-
vested host fruits. Identifying the odors mediating
host-fruit location by R. mendax and R. cingulata 1il
improve monitoring tactics for these important fruit
pests and provide insights into the mechanisms by
which they have speciated.
We thank R. Oakleaf and K. Bosch for assistance in the
field and E. Hoffman for preparing the fruit lures. The authors
dedicate this manuscript in memory of R. Prokopy and
S. Polavarapu. This research was supported by USDA
CSREES Grant 2002-04460 and USDA RAMP Grant 2002-
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Received for publication 15 March 2005, accepted 9 June
Vol. 34, no. 5