2005 03-12 Delury.Pub

CORE Metadata, citation and similar papers at core.ac.uk Provided by Journal of the Entomological Society of British Columbia J. ENTOMOL. SOC. BRIT. COLUMBIA 102, DECEMBER 2005 3 Antennal detection of sex pheromone by female Pandemis limitata (Robinson) (Lepidoptera: Tortricidae) and its impact on their calling behaviour 1,2 1 NAOMI C. DELURY , GARY J.R. JUDD and MARK G.T. GARDINER1 ABSTRACT Previous observations lead us to believe that female Pandemis limitata (Robinson) (0 to 24 h old) are as attractive as their pheromone gland extract to males in clean air, but are more attractive in an environment permeated with their major pheromone component (Z)-11-tetradecenyl acetate. Therefore, in this study, we tested the hypothesis that females can detect and/or respond to their pheromone components. Using electroanten- nographic detection, we found female P. limitata able to perceive both of their known pheromone components, (Z)-11-tetradecenyl acetate and (Z)-9-tetradecenyl acetate. Fe- male antennal response was found to be 46.3% weaker than that of males, under identical conditions, with male antennae producing significantly higher deflections to the higher pheromone doses tested and to the plant volatile, (E)-2-hexanal. Observations of females in clean air versus (Z)-11-tetradecenyl acetate-permeated air showed no significant differences with respect to onset time, frequency or duration of calling. Females moved significantly less often in a (Z)-11-tetradecenyl acetate-permeated portion of a flight tunnel than in the corresponding clean-air portion. Key Words: (Z)-11-tetradecenyl acetate, (Z)-9-tetradecenyl acetate, female electroan- tennography, flight tunnel, mating disruption, threelined leafroller, sprayable pheromone, microencapsulated pheromone, movement INTRODUCTION Although pheromone-based mating dis- formation of this type is lacking for most ruption of Lepidopteran species is widely species where commercial use of mating employed in some agricultural systems disruption is under study. During our own (Thomson et al. 2001), questions about the studies of pheromone communication dis- behaviour of female moths in the presence ruption in the threelined leafroller, Pan- of their own sex pheromone often remain demis limitata (Robinson) (Lepidoptera: unanswered. In particular, while there is Tortricidae), it appeared that males were evidence that some female moths perceive more responsive to “calling” females (0 to (Michell et al. 1972, Birch 1977, 24 h old) in a pheromone-permeated atmos- Palaniswamy and Seabrook 1978, Light and phere than they were to female gland ex- Birch 1979, Barnes et al. 1992) and even tracts, although no difference in male re- modify their behaviour (Palaniswamy and sponse was detectable between these Seabrook 1978, 1985, Palaniswamy et al. sources in clean air (N.C.D., unpublished 1979, Sanders 1987, Weissling and Knight data). One explanation for this observed 1996, Evenden 1998) in response to their difference is that female P. limitata can own sex pheromone, others apparently do detect their pheromone environment and not (El-Sayed and Suckling 2005) and in- adjust their behaviour in a manner that 1 Agriculture and Agri-Food Canada, Pacific Agri-Food Research Centre, 4200 Hwy 97, Summerland, BC, V0H 1Z0, Canada 2 To whom correspondence should be addressed: Tel.: +1 250 494 7711; Fax: + 1 250 494 0755; E-mail: [email protected] 4 J. ENTOMOL. SOC. BRIT. COLUMBIA 102, DECEMBER 2005 makes them more detectable to males than 14:Ac] and (Z)-9-tetradecenyl acetate [Z9- the female gland extract alone. Using elec- 14:Ac] (Roelofs et al. 1976) and asked the troantennograms (EAGs), we assessed the question, do females alter their calling be- ability of female P. limitata to perceive haviour in the presence of microencapsu- their two known sex pheromone compo- lated (MEC) Z11-14:Ac applied in labora- nents, (Z)-11-tetradecenyl acetate [Z11- tory flight-tunnel assays (Judd et al. 2005)? MATERIALS AND METHODS Laboratory cultures. Experiments Company, St. Louis, MO), Z9-14:Ac (97% were conducted with P. limitata from a purity, Regine Gries, Simon Fraser Univer- laboratory colony maintained at the Pacific sity, BC), and a 94:6 ratio blend of both, Agri-Food Research Centre, Summerland, respectively. The amount of Z11-14:Ac British Columbia (BC) since 1992 that remained equal between the treatments of originated from wild populations collected the main component and the blend; female in the Similkameen Valley of BC. Pan- antennae were also exposed to 100 µg doses demis limitata were maintained on a modi- from both Z11-14:Ac and the blend. Each fied pinto bean-based diet (Shorey and Hale antenna was exposed to each dose of each 1965) at 25 oC under a 16:8 h L:D photo- of the three compounds in order of increas- regime. Pupae were removed from diet, ing concentration. Treatments were puffed sexed and placed individually in 150 ml (200 ms; 10 ml per s) over each antenna, plastic cups provided with a wet cotton beginning with the lowest dose (0.1 ng) of wick until adults eclosed. Male and female each of the three compounds, which were moths were isolated from each other in presented in random order at each incre- separate environmental chambers (25 oC, mental dose. Baseline antennal responses 65% r.h. with a 16:8 h L:D reversed photo- were established using HPLC-grade hexane regime). (two puffs) and a puff of the plant volatile, Female and male perception of syn- (E)-2-hexanal in paraffin oil, before and thetic pheromone. Perception of synthetic after each pheromone test concentration. pheromone by female and male P. limitata All stimulus puffs were applied at 30 s in- was measured using EAGs. Our EAG sys- tervals. All chemical stimuli were dis- tem consisted of an IDAC-02 computer- pensed in 10 µl aliquots onto folded coupled data acquisition board, an INR-02 Whatman #5 filter paper (3 cm × 2 cm), EAG-SSR system and AutoSpike software placed in pipette tubes and connected to the (Syntech, Hilversum, The Netherlands). puffer. The procedure was repeated using Antennae excised from 0 to 24 h old fe- six female antennae and four male anten- males or males were mounted individually nae. inside 10 µl glass capillaries containing Normalized percentage antennal deflec- silver-coated wire recording electrodes. tions were calculated using the plant vola- Glass tubes were pulled at 300 oC on a Nar- tile response as the standard. Data were ishige (Model PN-30, Tokyo, Japan) micro- analyzed by one-way analysis of variance pipette puller. The distal antennal segment (ANOVA) followed by Dunnett’s test to was removed and that end of the remaining compare each treatment mean to the hexane antenna inserted into the indifferent elec- control. All experimental error rates were trode capillary. As a result, each antenna set at α = 0.05. Comparisons between fe- was suspended between two glass capillary male and male antennal responses at each electrodes filled with insect Ringer’s solu- dose were conducted on individual antennal tion (DeLury et al. 1999). Each antenna deflections (mV) by first performing a two- was challenged with six doses, in ten-fold way ANOVA, where the factors were sex increments from 0.1 ng to 10 µg, of Z11- and pheromone stimulus. A sex × phero- 14:Ac (97.5% purity, Sigma Chemical mone stimulus interaction term was in- J. ENTOMOL. SOC. BRIT. COLUMBIA 102, DECEMBER 2005 5 cluded in the model. Following a significant entered the clean-air portion of the tunnel. ANOVA, linear contrasts using t-ratio sta- Untreated panes were shielded during all tistics were used to make paired compari- pheromone applications and the tunnel was sons of mean antennal deflections for males allowed to ventilate for a minimum of 18 h and females at each dose. Experiment-wise between replicates. Pheromone treatment error rates for these multiple-paired com- consisted of Phase I MEC Z11-14:Ac (3M parisons were fixed at 5% by adjusting α Canada Company, London, ON) applied at values for individual comparisons using the a rate equivalent to 10 mg ai · m-2 to the Bonferroni inequality. All statistical tests cross-sectional area of the tunnel as de- were performed with JMP 5.1 (2003). scribed in detail by Judd et al. (2005). Female behaviour in a pheromone- Virgin female moths (0 to 24 h old) permeated environment. Female moths were chilled for 5 min at 2 oC and trans- were placed in clean air or a pheromone- ferred individually into stainless steel mesh permeated environment and observed in observation chambers (4.5 cm W × 3.5 cm side-by-side comparisons. To accomplish H × 5 cm D). Chambers were stacked verti- this, a sheet metal divider (73.3 cm × 37.4 cally to form a series of five individually- cm) was installed vertically in the middle of caged females. Treated and control portions the upwind portion of a pulling-style flight of the tunnel each received one series of tunnel [75 cm wide × 73.3 cm high × 187 five individually-caged females ca. 2.5 h cm long flight section] covered with a re- before scotophase, for a total of 15 females placeable 4 ml transparent polyester in each treatment. Females were observed ‘skin’ (3M Canada Company, London, ON) for calling (raised wings with protruding (Judd et al. 2005), creating two identical abdomen) and movement (physically walk- isolated chambers (upwind area = 36.65 ing in the chamber) every 15 m until the cm2). The upwind cross-sectional surface initiation of scotophase, when they were was constructed of a set of replaceable hori- observed continually for 3 h. Data gathered zontal sheet metal panes (73.3 cm × 3.7 cm before scotophase was used solely for de- with a 0.7 cm bend for stability) onto which termination of onset of calling behaviour pheromone was applied, with an untreated and was not included in any other analysis.

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