Plants release volatiles in response to caterpillar feeding that attract natural enemies of the herbivores, a tri-trophic interaction which has been considered an indirect plant defence against herbivores. The caterpillar-induced plant volatiles have been reported to repel or attract conspecific adult herbivores. To date however, no volatile signals that either repel or attract conspecific adults under field conditions have been chemically identified. Apple seedlings uniquely released seven compounds including acetic acid, acetic anhydride, benzyl alcohol, benzyl nitrile, indole, 2-phenylethanol, and (E)-nerolidol only when infested by larvae of the light brown apple moth, Epiphyas postvittana. In field tests in New Zealand, a blend of two of these, benzyl nitrile and acetic acid, attracted a large number of conspecific male and female adult moths. In North America, male and female adults of the tortricid, oblique-banded leafroller, Choristoneura rosaceana, were most attracted to a blend of 2-phenylethanol and acetic acid. Both sexes of the eye-spotted bud moth, Spilonota ocellana, were highly attracted to a blend of benzyl nitrile and acetic acid. This study provides the first identification of caterpillar-induced plant volatiles that attract conspecific adult herbivores under natural conditions, challenging the expectation of herbivore avoidance of these induced volatiles.

Codling moths are attracted to acetic acid and to ethyl-(E,Z)-2,4-decadienoate, the pear ester, when presented individually. The attraction to acetic acid is thought to be a food finding behavior, whereas the pear odorant, ethyl-(E,Z)-2,4-decadienoate, may be a host kairomone. We found, in a flight tunnel study, that more male and female codling moths were captured in traps when the compounds were presented together compared to tested separately. The combination of odorants provides a stronger lure for female codling moths than exists with pear ester alone and increases the potential for using lures in managing this pest of pome fruits and walnuts.

Mating competitiveness and pheromone trap catches of mass-reared, male codling moth, Cydia pomonella (L.) (Lepidoptera: Tortricidae), from the Osoyoos, British Columbia, Canada, massrearing facility operated by the Okanagan-Kootenay Sterile Insect Release Board, were compared to wild males using mark-release-recapture field experiments in spring, summer, and autumn at Summerland, British Columbia. In spring, significantly more wild diapause males mated with tethered, wild females than did non-irradiated (0 Gy) or irradiated (100 or 250 Gy) non-diapause, mass-reared males. A lower dose of radiation did not improve mating competitiveness, nor catches of mass-reared males released in spring. Median mating time for wild males was approximately 45 min earlier than mass-reared males with most wild males (70.5%) mating before sunset and mass-reared males mating at or shortly after sunset in spring. Superior mating competitiveness of wild males in spring was mirrored by greater recapture rates in pheromone-baited traps. In summer, mating competitiveness of mass-reared moths improved relative to wild males and there was a significant inverse relationship between radiation dose (0, 100, and 250 Gy) and competitiveness of mass-reared males. In autumn, untreated, wild males were significantly more responsive to pheromone traps than non-diapausing mass-reared males receiving 250 Gy of radiation. Mass-reared males, subjected to diapause-inducing conditions as larvae and emerged from diapause before this irradiation treatment, were recaptured significantly more often than similarly irradiated, non-diapause, mass-reared males, but not more than untreated, diapause wild males. We hypothesize that differences between wild and mass-reared males in daily timing or speed of responses to natural or synthetic pheromone sources under montane weather patterns typical of spring in British Columbia may partially explain poor activity of sterile males, and low sterile : wild overflooding ratios during spring when measured using pheromone traps by the sterile insect release programme in British Columbia.

The effects of pre‐exposing male codling moths, Cydia pomonella (L.) (Lepidoptera: Tortricidae), to their pheromone (E,E)‐8,10‐dodecadien‐1‐ol (codlemone), in static and moving air, under laboratory and field conditions, on subsequent antennal sensitivity, behavioural responsiveness, and attraction to codlemone were investigated. In flight tunnel experiments, the percentage of moths wing fanning and taking flight were mostly unaffected, but upwind flight to, and contact with, pheromone sources known to elicit responses of both were shown to depend on the intensity and duration of previous exposure to codlemone and recovery time between exposure and assessment. Ten to 30‐min pre‐exposures to codlemone in static air (≈ 35 µg l−1) not only caused a 99% reduction in attraction, but also significantly reduced electroantennogram response to codlemone. Recovery of full antennal sensitivity to codlemone took more than 1 h, but recovery of attraction took over 4 h, suggesting that habituation is also partially involved in reduced behavioural responsiveness following pre‐exposure. Seventy‐five min exposures to codlemone in moving air (5–10 cm s−1) at rates of 0.9, 4.5, and 18 µg h−1 from Celcon fibres caused 75, 86, and 99% disruption, respectively. However, 30–34‐h exposure of caged moths to air moving through an orchard treated with 1000 Isomate‐C® dispensers ha−1 releasing approximately 20 µg h−1 per dispenser during tests, had no impact on moth response in flight‐tunnel assays 30 min after removal from the orchard. In this treated orchard, catches of free‐flying moths in pheromone‐baited traps were completely inhibited. If observed mechanisms such as long‐lasting antennal adaptation or habituation of the central nervous system contribute to the disruption of pheromone communication among codling moths under field conditions, it seems unlikely that they occur following exposure to the average atmospheric concentrations of codlemone. For these effects to be important, codling moths may require close contact with pheromone sources for extended periods, or repeated close encounters.

No abstract

A case study of a pheromone-based attract-and-kill management strategy for codling moth, Cydia pomonella (L.), was conducted to examine key insect behavioral factors mitigating the possible effectiveness of this strategy. Last Call CM is a newly registered attracticide product that combines the primary component of codling moth sex pheromone with the insecticide permethrin. Studies of competition between pheromone point sources within caged trees showed individual attracticide droplets were signiÞcantly more attractive to male moths than calling females. In commercial orchard blocks, marked male moths were recaptured after visiting attracticide droplets applied at rates of 50, 100, and 200 droplets/ha, although no marked moths were recaptured in plots with 500 droplets/ha. This experiment also revealed no signiÞcant differences among 0, 50, 100, and 200 droplets/ha in suppressing total catch in female-baited traps, nor were total numbers of females attracting at least one male reduced signiÞcantly. In plots with 500 droplets/ha applied, male moth catch was suppressed signiÞcantly compared with catches in untreated control plots, and the number of females attracting at least one male was reduced signiÞcantly as well. Experiments investigating sublethal physiological effects of attracticide exposure upon mating competency of male codling moths demonstrated male leg autotomy at 1, 24, 48, and 72 h after exposure. Male codling moth at 1, 24, 48, and 72 h after exposure placed near calling virgin females exhibited signiÞcant behavioral differences from sham-treated males in courtship and mating. These results clarify some of the possible mechanisms, and strengths and weaknesses of this attract-and-kill management strategy for codling moth.

No abstract

The advent of novel genetic methods has led to renewed interest in the sterile insect technique (SIT) for management of insect pests, owing to applications in mass rearing and in the production of sterile offspring without use of irradiation. An area-wide management programme for codling moth, Cydia pomonella, has employed the SIT and other management practices over a large area (3395 to 7331 ha) of orchards and neighbouring urban, public, or First Nations lands in British Columbia, Canada, for 25 years. This project is the first to employ the SIT for C. pomonella, and the longest-running application of area-wide techniques for its control, anywhere. It was derived from basic research and applied trials from the 1960s onwards. Many biological challenges were overcome, and lessons learnt, in transferring from small- to large-scale applications of mass rearing and the SIT, with particular regard to Lepidoptera. Research has proven essential to identifying, if not resolving, issues that threaten the implementation and success of any such programme. The major challenges encountered, and the resulting research, are reviewed, as well as future directions. Recommendations are given for application of the SIT as part of any area-wide management programme for C. pomonella.