K. F. Haynes

A pulsed cloud of sex pheromone elicits upwind flight in male moths

ABSTRACT. Male oriental fruit moths do not fly upwind in a continuous uniform cloud of pheromone, but readily do so when the cloud is pulsed at 1 or 0.5/s or when a plume from a point source of pheromone is placed within the continuous cloud. It is suggested that males of moth species that require such fluctuating pheromone stimulation for upwind flight will normally receive it from a filamentous, point‐source‐produced plume. However, we hypothesize that upwind progress may cease close to the source due to excessively high emission rates or inappropriate blend ratios, when fluctuating sensory output becomes attenuated, despite higher actual molecular concentration fluctuations.

Field and laboratory electroantennographic measurements of pheromone plume structure correlated with oriental fruit moth behaviour

Abstract. Peak‐to‐trough electroantennogram amplitudes (bursts), caused by the individual filaments of a plume of female pheromone, diminish as high‐emission‐rate sources are approached by male Grapholita molesta, and this reduction is correlated with in‐flight arrestment (ceasing to advance upwind). These findings are consistent with the hypothesis that one cause of in‐flight arrestment in response to high‐concentration point sources is the attenuation of the peak‐to‐ trough amplitudes close to the source. High burst frequency, high pheromone flux, or low levels of continuous neuronal activity all are less well correlated with arrestment. Rather, arrestment appears due to a reduction of chemosensory input to the CNS during flight up the plume, even though the actual molecular concentration continues to increase. In a laboratory wind tunnel, upwind flight initiation by more than 20% of males was elicited only by pheromone source concentrations evoking significant fluctuations in EAG amplitudes at downwind release points. The burst frequencies that evoked high levels of upwind flight initiation ranged from a mean of 0.4‐2.2 bursts/s. Because a previous study revealed that flying male G. molestachange their course angle within 0.15 s of losing or contacting pheromone, these EAG burst frequencies indicate that during flight in a pheromone plume, many manoeuvres are probably made in response to contact with individual plume filaments. Thus, upwind flight tracks may be shaped by hundreds of steering reactions in response to encounters with individual pheromone filaments and pockets of clean air. Field‐recorded EAGs reveal that burst amplitudes diminish from 3 to 30 m downwind of the source, whereas burst frequencies do not, averaging c.1/s at 3, 10 and 30 m downwind.

Manoeuvres used by flying male oriental fruit moths to relocate a sex pheromone plume in an experimentally shifted wind‐field

ABSTRACT. In a wind‐field experimentally shifted in direction by 35d̀, flying male Grapholita molesta (Busck) zigzagging upwind either maintained contact with a pheromone plume and followed it across during the shift or lost it and commenced casting at c. 90d̀ across the shifting windline to locate it eventually in its new position. Males accomplished both of these results by integrating the previously described systems of optomotor anemotaxis and self‐steered counterturning, but with faster reaction‐times to pheromone on and off than heretofore calculated for this species. We found no evidence that males following the plume across used chemotaxis as proposed for another species, Rather, the sawtoothed‐shaped tracks were a result of the anemotactic and counterturning systems responding rapidly and reiteratively to each loss and gain of pheromone along the plume in the shifting wind. The response to an increase or decrease in pheromone concentration by males was to change their course angle to more upwind or more crosswind, respectively, on the very first reversal (within c. 0.15 s) after the concentration changed. Because males adjusted their airspeeds more slowly to changes in concentration, the groundspeeds along the more upwind‐orientated legs were lower than those along cross‐wind legs, contributing to the sawtoothed shape of tracks of plume‐followers. The self‐steered counterturning programme also reacted quickly to concentration changes, the reversal intervals tending to be shorter following each contact with pheromone than after each excursion into cleaner wind. Following casting after losing the plume, males relocating the pheromone plume exhibited an upwind ‘surge’ of narrow zigzagging flight because on the first leg in the plume they steered a course more directly upwind than on the previous leg and increased the frequency of counterturning to its highest value while maintaining the relatively high airspeed acquired while casting.

Potential for evolution of resistance to pheromones: Interindividual and interpopulational variation in chemical communication system of pink bollworm moth

After an extensive examination of the release rates and blend ratios of pheromonal components emitted by field-collected femalePectinophora gossypiella (Saunders), we find no evidence of resistance to pheromones applied to cotton fields to disrupt mating. Females from fields with 3–5 years of exposure to disruptant pheromones as well as those from fields with only minimal exposure to disruptant pheromones emitted (Z,Z)-7,11-hexadecadienyl acetate at a rate of ca. 0.1 ng/min and (Z,E)7,11-hexadecadienyl acetate at ca. 0.06 ng/min. The ratio of pheromonal components was much less variable than the measured emission rate and was centered about a 61:39Z, Z to Z,E ratio. In contrast to the blend ratio emitted by females, the composition of the pheromonal blend used in monitoring populations and disrupting mating is centered about 50:50 Z,Z to Z.E. In general there was a remarkable consistency in the release rate and blend ratio among populations of females throughout southern California and those from a laboratory colony. It would appear that, although resistance to theP. gossypiella pheromone is still a very real possibility when it is used heavily in pest management as a mating disruptant, there are current agricultural practices and conditions which would hinder its development.

Monitoring insecticide resistance with insect pheromones

A novel pheromone-baited sticky trap laced with insecticides proved to be a simple and effective means of monitoring insecticide resistance in the pink bollworm moth. Adult males from fields treated frequently with pyrethroid insecticides showed up to 20-fold resistance to permethrin and up to 14.5-fold resistance to fenvalerate.

Sensory and behavioral effects of gossyplure alcohol on sex pheromone response of male pink bollworm moths,Pectinophora gossypiella.

Abstract(Z,Z)- and (Z,E)-7,11-hexadecadienol, reported to be pheromone precursors, interfere with the normal sequence of behavioral response of malePectinophora gossypiella to sex pheromone. The magnitude of the interference can be diminished with higher release rates of the sex pheromone. (Z,Z)-7,11-Hexadecadienol is more effective than itsZ,E isomer in eliciting the reduction in the behavioral response. Electroantennographic evidence suggests that each alcohol may be interfering more with receptor sites for the conformationally similar pheromone acetate than with receptor sites for the other pheromone isomer. Defining behavioral and physiological effects of pheromone analogs such as the alcohols of gossyplure may help to determine their potential for behavioral manipulations.

Identification of sex pheromone of calendula plume mothPlatyptilia williamsii

The sex pheromone of the calendula plume moth,Platyptilia williamsii was identified as (Z)-11-hexadecenal (Z11–16∶Aid). Extracts of female sex pheromone glands contained several compounds when analyzed by capillary and packed-column GLC. However, airborne collections of volatiles from glands contained only one of these compounds, having the same retention time asZ11–16∶Ald. GC-MS and microozonolysis analyses of the natural product were consistent with those of syntheticZ11–16∶Ald. In a flight tunnel, males oriented upwind and touched sources ofZ11–16∶Ald and gland extract with equal frequency. Field tests of syntheticZ11–16∶Ald already have shown it to be a potent sex attractant for males of this species. This study further supports the hypothesis thatP. williamsii and a sympatric species,Platyptilia carduidactyla, are not reproductively isolated by chemical differences in the composition of the sex pheromone, but rather by temporal differences in sexual activities.