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ATTRACTION OF TOBACCO BUDWORM MOTHS (LEPIDOPTERA:
NOCTUIDAE) TO JAGGERY, A PALM SUGAR EXTRACT
P. J. Landolt1 and E. R. Mitchell2
United States Department of Agriculture
1Yakima Agriculture Research Laboratory
2Center for Medical, Agricultural and Veterinary
Entomology
Abstract
Male tobacco budworm, Heliothis virescens Fab., moths
released into a field cage were recaptured in traps baited with
aged 10% jaggery, a palm sugar extract. Both male and female tobacco
budworm moths were attracted to aged 10% jaggery in a flight tunnel,
exhibiting oriented flights ending in contact with the bait. Although
the bait was initially not attractive either to females in a flight
tunnel or to males in a field cage, it subsequently became attractive
after one week and increased in attractiveness for up to 24 days
after it was made.
Key Words: attractant, feeding, Heliothis virescens,
trap, behavior, sugar
Resumen
Machos adultos del gusano del tabaco, Heliothis virescens
Fab., liberados en una jaula de campo fueron recapturados en trampas
cebadas con 10% de jaggery envejecido, un extracto de azúcar
de palma. Tanto hembras como machos adultos fueron atraídos
por el cebo en un túnel de vuelo, y ambos mostraron vuelos
orientados terminando en el contacto con el cebo. A pesar de que
el cebo inicialmente no fue atractivo a las hembras en el túnel
de vuelo, o a los machos en la jaula de campo, éste se
tornó atractivo después de una semana e incrementó
su atractividad hasta los 24 días de haber sido preparado.
The tobacco budworm, Heliothis virescens (Fab).,
is a pest of several agricultural crops in North America, including
tobacco and cotton. The principal means of monitoring the presence
of tobacco budworm is a female sex pheromone blend that is attractive
to males (Sparks et al. 1979, Ramaswamy et al. 1985). However,
such a method is ineffectual in fields treated with female sex
pheromone as a mating disruptant. Also, the relationship between
numbers of males captured in pheromone traps and either population
levels or crop damage is not clear. Additional attractants, particularly
if effective for females, would be useful under such circumstances.
A variety of moths are attracted to sweet materials,
presumably as a source of adult nutrition. Sugar-rich concoctions
often are used by moth and butterfly collectors (Holland 1903,
Sargent 1976). Molasses solutions have been used to trap oriental
fruit moth, Grapholita molesta (Busck), (Frost 1926) and codling
moth, Cydia pomonella (L), (Eyer 1931) in tree fruit orchards.
Many noctuid moths are attracted to sugar baits (Norris 1936),
although documentation of which species are attracted is lacking.
Frost (1928) captured 23,574 noctuid moths in 300 pails containing
sugar baits set out for oriental fruit moth, but did not identify
them below the family level. Poisoned sweet baits were used for
control of corn earworm, Helicoverpa zea (Boddie), during the
19th century (Ditman & Cory 1933 and references therein).
The grass looper, Mocis latipes Guenee, can be captured in traps
baited with solutions of molasses or jaggery (Landolt 1995). Jaggery
is an unrefined sugar made from palm sap, used asa cooking sweetener
in some areas of subtropical and tropical Asia. Landolt (1995)
also reported the capture of 13 additional species of Noctuidae
in glass traps baited with jaggery or molasses solutions in Florida.
There are no reports of captures of tobacco budworm
moths in traps with baits containing sugars or sugar-based materials.
However a great number of species of Noctuidae likely are attracted
to sugar baits (Norris 1936), and most Noctuidae captured in traps
baited with sugar-rich materials have not been identified (e.g.,
Frost 1928). The tobacco budworm moth feeds at flowers, extrafloral
nectaries, artificial sugar sources, and grass heads (Lingren
et al. 1977, Ramaswamy 1990) and may be attracted to sugar baits.
We report here the attraction of male and female
tobacco budworm moths to solutions of jaggery, and we also determined
the optimum age of the bait for attractiveness to moths in a flight
tunnel. This work demonstrates the upwind orientation of tobacco
budworm in response to food baits and provides a convenient assay
system for pursuing the isolation and identification of attractive
volatile chemicals emanating from sugar baits. It is hoped that
such compounds may be useful as attractants for tobacco budworm
as well as other pestiferous species of moths.
Materials and Methods
Insect Rearing and Handling
Tobacco budworm pupae were obtained from the laboratory
colony maintained at the Gainesville, Florida, United States Department
of Agriculture, Agricultural Research Service laboratory. Pupae
were sorted by sex and were held in screened cages (25 ×
25 × 25 cm) for adult emergence. Pupae were moved to new
cages daily to provide moths of discrete age groups. A water jar
was placed on the top of each cage, and each cage was provisioned
with a 60 ml paper cup containing water-soaked cotton balls. Males
and females were held in separate environmentally-controlled rooms
at 24°C, 60-80% RH and a 14:10 (L:D). photoperiod with lights
off at 0800 and on at 1800 hours (E.S.T).
Field Cage Bioassay
An initial test of tobacco budworm moth response
to jaggery (Indian Kolhapur Jaggery, House of Spices Inc., Jackson
Heights, NJ) was conducted in 2 large cylindrical cages, each
2.2 m in height and 2.7 m in diameter (Calkins & Webb 1983),
which were set up in an area of lawn largely beneath the shade
of a live oak tree. Pairs of glass McPhail traps (Newell 1936)
were hung from the ceiling of each cage, about 0.5 m north and
0.5 m south of the center of the field cage. Traps were hung by
a wire with the trap opening 20 cm below the cage ceiling. One
of each pair of traps in a cage was baited with 200 ml of 10%
jaggery in deionized water (5 to 16 days old) and the other trap
was baited with 200 ml of deionized water. From 20 to 30 male
tobacco budworm moths (3 to 5 days of age) were released into
a field cage in late afternoon, and the numbers of moths captured
in traps were counted the following morning. Jaggery bait was
5 to 16 days old when placed in the field cages. This assay was
conducted 20 times, with jaggery bait reused for replicates. Jaggery-baited
and control traps were alternated in position with each assay
replicate for both field cages. Mean trap catch data, combined
for all bait ages, were analyzed by Students t-test to determine
if the catches of moths in treatment and control traps were significantly
different. Catch data for jaggery-baited traps were also evaluated
in comparison to bait age by regression analysis.
Flight-Tunnel Bioassays
Two experiments were conducted using a flight tunnel
to evaluate tobacco budworm moth responses to jaggery. The flight
tunnel and room were described by Landolt and Heath (1987). Moths
were tested during the 3rd through 5th hours of the 10 h scotophase,
and they were placed in the flight tunnel room 30 min before the
bioassays. Moths were tested individually. They were released
from a plastic vial near the center of the downwind end of the
flight tunnel and were given 2 min to respond to test materials
placed at the upwind end of the flight tunnel. Moths were scored
for upwind oriented flights within the odor plume and for proximity
or contact with the odor source following plume tracking. The
baits tested were 10% solutions of jaggery made up as 400 ml batches
and placed in open glass jars in a laboratory fume hood until
used. For flight tunnel assays, 200 ml of solution were poured
into a 9 cm plastic petri dish supported by a ring and ring stand.
A paper towel was hung into the middle of the dish to act as a
wick, increasing the surface area of the solution.
The first flight tunnel experiment was a demonstration
of male and female tobacco budworm attraction to aged jaggery.
Three to four-day old unfed females were tested to either a200
ml batch of aged (12 to 28 days) 10% jaggery in water or to 200
ml of water alone. Ten female moths were sequentially tested for
a response to water, followed by ten females sequentially tested
for response to jaggery. This experiment was conducted on five
different days, with water presented first in 2 trials, and jaggery
presented first in 3 trials. This experiment was repeated with
males, but on 7 different days. The treatment sequence (water
and jaggery) was also alternated between replicates in this experiment.
Attraction response data (attraction is upwind oriented flight
and contact with the bait) were analyzed by Student’s t-test,
after transformation to percentages of moths tested within each
data set.
Because microbial fermentation may be a determining
factor in the attractiveness of food baits to many lepidopterans
(Norris 1936), a second flight tunnel experiment was conducted
to evaluate the effect of the age of the jaggery bait on its attractiveness
to female tobacco budworm. It is expected that colonization and
growth of microbes in baits, and resultant changes in odorants
released from baits, occur over time. Attractiveness to bait may
then increase with time, as microbes and their metabolic byproducts
increase in abundance. This experiment was conducted as two separate
series of bait ages: a short series and a long series. The short
series consisted of baits held for 0, 3, 6, 9, and 12 days in
a fume hood in the laboratory. Baits were made every 3 days and
bioassays were conducted on 6 different days when baits of all
age cohorts were available simultaneously. The long series consisted
of baits held for 0, 6, 12, 18, and 24 days. Similarly, these
were made every 6 days and bioassays were conducted on 6 different
days when baits of all age cohorts were available simultaneously.
Every time a series of bait ages was tested in the flight tunnel,
five females were tested per treatment (bait age). Thirty females
were tested per treatment over the course of the replicates. The
treatment sequence was altered daily over the 6 days that the
test was replicated. Response data for the long series was subjected
to regression analysis for relationship between bait age and moth
response.
Results
Male tobacco budworm moths were captured only in
traps baited with 10% jaggery placed in field cages. Mean numbers
of released males captured in glass McPhail traps baited with
10% aged jaggery (4.45 ± 1.5 moths per trap per day) were
significantly greater than those captured in traps baited only
with water (no moths captured) (t = 3.0, df = 19, p = 0.008).
There was a significant linear regression of bait age versus numbers
of male tobacco budworm captured in traps baited with jaggery
(r2 = 0.65, t = 2.58, df = 18, p = 0.03, Y = -9.26 + 1.42X) (Fig.
1).
Both sexes of tobacco budworm were attracted to 10%
solutions of jaggery presented in the flight tunnel. Twenty-four
percent of females flew upwind and contacted the jaggery bait,
compared to no females responding to the control (water only)
(t = 4.71, df = 4, p = 0.009). Twenty-seven percent of males tested
flew upwind and contacted the jaggery bait compared to no males
responding to the control (t = 3.14, df = 6, p = 0.022).
In a direct comparison of the attractiveness of jaggery
bait of different ages, no female tobacco budworm moths were attracted
to bait that was freshly made or was 3 or 6 days old. Nine-day
old jaggery was essentially non-attractive as well. Female response
to jaggery increased with bait age from 12 through 24 days old
(Fig. 2), with the highest response (40%) obtained with 24 day
old bait. The relationship between bait age and moth response
for the long series was significant by regression analysis (r2
= 0.948, t = 5.14, df = 4, p = 0.014, Y = -6.3 + 1.73X).
Discussion
These results demonstrate that both sexes of tobacco
budworm are attracted to fermented bait made from 10% jaggery.
Both females and males were attracted to jaggery (exhibited upwind
oriented flights from the release dispenser and contacted the
bait) in the flight tunnel. The recapturing of male tobacco budworms
in baited traps in a field cage also indicates an ability to orient
to the source of odors from such baits.
This is the first report of orientation responses
to food baits by H. virescens. Adult tobacco budworms feed at
materials that are sugar rich, including flowers, extrafloral
plant nectaries, and grass florets (Lingren et al. 1977, Ramaswamy
1990). There are also reports of corn earworm moths feeding at
sweet baits (Ditman and Cory 1933) and at fungal-infected grass
florets (Beerwinkle et al 1993), with the assumption that they
are attracted to such materials. Tobacco budworm attraction to
odors emanating from fermenting sugar solutions is likely a mechanism
to locate the sources of such odors in order to feed.
The significant regressions of bait age versus males
captured in traps in a field cage and bait age versus female response
in a flight tunnel support the assumption of Norris (1936) that
microbial activity is a critical factor in moth attraction to
sweet baits. The grass looper, M. latipes, also responds optimally
to sweet baits that are aged (Landolt 1995). However, 3- day old
jaggery or 3-day old molasses was most effective as a trap bait
for the grass looper, compared with 16 or 24 day old jaggery for
the tobacco budworm. Perhaps the grass looper moths and tobacco
budworm moths respond to different sets of odorants emanating
from baits of different ages.
The positive results using the flight tunnel provide
a convenient bioassay technique for pursuing the isolation and
identification of odorants from solutions of jaggery that are
attractive to tobacco budworm. The liquid bait and trap used in
these experiments are too limited and inconvenient to use as a
monitoring method for female tobacco budworms. The trap is heavy
and fragile, and trap maintenance is time-consuming. The trap
also holds a limited number of captured moths, and captured specimens
may be difficult to identify if allowed to remain and decompose.
For these reasons, it is considered that a formulated blend of
synthetic chemicals that are attractive to tobacco budworm can
be adapted to a cheaper and easier trap design for field use.
Acknowledgments
Technical assistance was provided by O. Molina and
S. Lovvorn. Moths used in bioassays were provided by F. Adams,
T. Nguyen, C. Greene, and N. Loman. S. Clement, K. Ward, T. W.
Phillips, and D. M. Jackson critiqued an early draft of the manuscript.
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Fig. 1. Numbers of male tobacco budworm moths released
into a field cage and captured in traps baited with 10% jaggery
of different ages. February-March 1996.
Fig. 2. Percentages (± SEM) of female tobacco
budworm moths attracted to contact a pan containing 200 ml of
10% jaggery in a flight tunnel, for different ages of jaggery.
The short series (solid bars) included 0, 3, 6, 9, and 12-day
old baits. The long series (cross hatched bars) included 0, 6,
12, 18, and 24-day old baits.
Agricultural Research Service
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