Rate and Periodicity of Pheromone Release from Individual Female Artichoke Plume Moths, Platyptilia carduidactyla (Lepidoptera: Pter~phoridae)~

The rate and periodicity of the emission of the sex pheromone [(a-1 1-hexadecenal] from the pheromone glands of individual female artichoke plume moths, Platyptzlia carduzdactyla, were quantified The mean rate of volatilization of (2)-11-hexadecenal from the glands of the moths peaked at 1 52  0 41 (SE) nglmin during the scotophase, and was at low levels during the entire photophase This periodicity in emission rate paralleled the behavioral periodicity of calling by females, indicating a close coordination of the biochemical and behavioial aspects of pheromone release The highest recorded emission rate from a female P carduzdactyla was 5 1 nglmin No other pheromone-like compounds were detected in these pheromone collections (2)-11-Hexadecenal was identified as the sex pheromone of the artichoke plume moth, Platyptiha carduidactyla (Riley), by Klun et a1 (1981) These authors concluded that, if other long-range pheromonal components were present, they constituted less than 1 25% of the pheromonal blend Since its identification, this synthetic sex pheromone has shown promise as an aid in the control of this species which is the most serious pest of artichokes (Haynes et a1 1981), and it is currently being used for monitoring populations and disrupting mating A modification of the pheromone collection technique developed by Baker et a1 (1981) was utilized to quantify several aspects of the chemical communication system of P carduidactyla First, the emission rate of (2)-11hexadecenal from sex pheromone glands was determined Second, the relationship between the periodicity of pheromone release from forcibly extruded pheromone glands and the periodicity of calling behavior was established Third, the volatiles emitted by females were examined for traces of other sex pheromone components Materials and Methods Female P cwduidactyla used in this study were reared from field-collected artichoke buds that contained larvae Infested artichokes from Castroville, Calif , were held at 10° in bins housed in a dark "cold" room Last-instar larvae were collected as they emerged from these artichokes Pupae were separated by sex, and female pupae were housed in a Percival environmental chamber (temperature 20°C LD 14: 10) Individual 2to 10-day-old virgin females were inserted abdomen-fist into a 3 0-rnrn (ID) glass tube which had a 0 9-mm hole at the distal end (Fig 1) A lowpressure vacuum was used to pull the female to the distal end, and a pipe cleaner was used to apply pressure to the head of the female, resulting in eversion of the ovi'Received for publication 8 April 1983; accepted 17 June 1983. ^art of this study was completed when K F.H was at the Department of Entomology, University of California, Davis positor and the associated bilobed sex pheromone gland Since the pheromone gland was forcibly extruded, volatilized pheromone could be detected (if released at a rate greater than 0 01 nglmin) even during periods when females did not actively call The tube was inserted ovipositor-end-first through a Teflon-coated gas-liquid chromatography (GLC) septum (a 3 0-mm hole had been cut in the septum) into a modified version of the pheromone collection device described by Baker et al (1981) Volatiles emitted from the gland's surface were collected for 10 min onto ca 10 mg of glass wool Some females could still walk after this procedure if they were removed promptly and carefully from the glass extrusion tube An internal standard [either 3 0 ng of (2)-11-tetradecenal or 5 0 ng of octadecenal] was added to the glass wool before it and the inside of the collector were rinsed with ca 200 a1 of CS, This volume of solvent was then reduced to approximately 1 pJ (for capillary columns) or 6 pl.(for packed columns) Analyses were made on a Varian 3700 gas chromatograph equipped with a hydrogen flame detector, a Hewlett-Packard 3380A intergrator, and a Honeywell Electronik 196 chart recorder Injections were made onto two types of columns in the study of periodicity of pheromone release: (1) SP2330 glass capillary column (direct injection; injector temperature 180' C; temperature program run 90 to 150° at 60°C/mi with 1-min hold at 90°C He flow rate= 100 cmtsec; N2 make-up gas flow rate = 25 mllmin; column dimensions 30 m by 0 25 mm ID; df = 0 22 pm), and (2) Silar 10C packed glass column (4 706g of 10% Silar 10C on acid-washed 100 to 120-mesh Chromasorb W; glass column 3 m by 4 mm (OD); oven temperature 180°C N2 flow rate= 30 mlfmin) In addition, to examine the emitted volatiies more thoroughly for sex pheromone-like compounds, some injections were made onto a 80% SE52/20% BBBT glass capillary column (direct injection: column temperature = 1 80°C He flow rate = 45 cmlsec; N, makeup gas flow rate = 25 mllmin; column dimensions 30 m by 0 25 mm ID; df = 0 3 am) and a 2% SF-96 packed column (on 100-120 Chromasorb W AcW-DMCS; oven temperature 170°C N2 flow rate = 30 mllmin; glass