Mark G.T. Gardiner

Reduced antennal sensitivity, behavioural response, and attraction of male codling moths, Cydia pomonella, to their pheromone (E,E)‐8,10‐dodecadien‐1‐ol following various pre‐exposure regimes

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.

Control of codling moth in organically-managed apple orchards by combining pheromone-mediated mating disruption, post-harvest fruit removal and tree banding

An integrated programme of pheromone‐mediated mating disruption using Isomate‐C®, post‐harvest removal of fruit, and trapping overwintering larvae with cardboard tree bands, was used to control codling moth, Cydia pomonella (L.) (Lepidoptera: Tortricidae), in four commercial ‘organic’ apple orchards in Cawston, British Columbia during 1989–1992. One application of 1000 dispensers ha−1 on May 1 delivered estimated seasonal totals of 16.6, 16.5 and 19.9 g of E,E‐8,10‐dodecadien‐1‐ol [=codlemone] ha−1 in 1990, 1991 and 1992, respectively, at median rates of 8.4, 8.3, and 13.3 mg · ha−1· h−1 during dusk flight periods of first brood and 5.3, 4.7 and 4.6 mg · ha−1· h−1 in second brood, respectively. Over this 3‐year period damage from codling moth at harvest ranged from 0.08 to 2.4%, and averaged <0.7% in these four organic orchards, while damage in five conventional orchards receiving sprays of azinphosmethyl ranged from 0.02 to 1.85%, and averaged 0.5%. Damage in an experimental orchard that was banded only, ranged from 43.5 to 56.7%, and averaged 48.9%. Between 1990 and 1992 cumulative male catches in Pherocon 1‐CP wing traps baited with 10 mg of codlemone declined by 52% and densities of overwintering codling moth larvae declined an average of 49.5% in all organic orchards. Overwintering populations in the banded experimental orchard showed an increase of 57.7% during this study period. We conclude that an integrated programme of pheromone‐mediated mating disruption, post‐harvest fruit removal and tree banding, controls codling moth effectively enough to make organic apple production viable in British Columbia.

Is lack of mating competitiveness in spring linked to mating asynchrony between wild and mass‐reared codling moths from an operational sterile insect programme?

Mating competitiveness and pheromone trap catches of mass‐reared, male codling moth, Cydia pomonella (L.) (Lepidoptera: Tortricidae), from the Osoyoos, British Columbia, Canada, mass‐rearing 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.

Diapause improves springtime mating competitiveness of male codling moth mass-reared for a sterile insect programme

Since 1994, sterile, mass-reared codling moths, Cydia pomonella (L.) (Lepidoptera: Tortricidae), have been released in fruit-growing valleys of British Columbia (BC), Canada, in an effort to eradicate (Dyck & Gardiner, 1992) and now manage this pest (Thistlewood & Judd, 2003). Poor recapture of sterile males in spring has been a significant concern for the Okanagan-Kootenay Sterile Insect Release (SIR) Programme since its inception (Judd et al., 2004). From 1994 to 2004, ratios of sterile (S) to wild (W) male moths in pheromone trap catches, which are used operationally as a measure of programme efficacy, have rarely reached the desired target of 40:1 in spring, often failing to reach 10:1 (Thistlewood et al., 2004). Judd et al. (2006) showed that small catches of sterile males in spring were correlated with their poor mating competitiveness. Suboptimal S:W ratios and inadequate mating competitiveness in spring are thought to be contributing factors behind slower than expected population reductions using the sterile insect technique (SIT) against codling moth in BC (Thistlewood & Judd, 2003; Judd et al., 2004). Codling moth has a facultative diapause and overwinters as diapausing fifth-instar larvae. In mass-rearing facilities designed for sterile codling moth insect programmes, larval diapause is prevented and moths are produced year-round by rearing larvae under constant high temperature and long day-length conditions (Bloem et al., 1998). However, it is possible for mass-rearing facilities to produce large numbers of adult codling moths from larvae that have experienced diapause (Bloem et al., 1997). Under spring, summer, and autumn weather conditions, irradiated, adult male codling moth derived from larvae experiencing diapause are recaptured in significantly greater numbers than are similarly irradiated, male moths derived from non-diapausing larvae (Bloem et al., 1998, 2004; Judd et al., 2006). These data imply that massreared moths emerging from diapause exhibit increased activity and possibly improved performance in spring, but it remains to be shown if or how much mating competitiveness is improved. Currently, there are no data comparing the relative activity and recapture of sterile male moths derived from mass-reared diapausing larvae with wild males derived from overwintering diapause larvae in spring, the time when greater S:W ratios are most needed by the Okanagan-Kootenay SIR Programme (Judd et al., 2004). The objective of this field study was to assess the mating competitiveness and recapture of sterilized male codling moths that have been mass-reared through a diapause larval state (Bloem et al., 1997) in comparison to wild males that developed on apples but also emerged from larval diapause in spring. Comparison with the standard, sterilized non-diapausing strain of mass-reared male codling moths used by the Okanagan-Kootenay SIR Programme is included to facilitate comparisons across studies.

Examining disruption of pheromone communication in Choristoneura rosaceana and Pandemis limitata using microencapsulated (Z)-11-tetradecenyl acetate applied in a laboratory flight tunnel

Pheromone‐based mating disruption of lepidopteran pests (Tortricidae) of pome fruits using hand‐applied dispensing systems has become standard management practice for many producers in western North America. Sprayable microencapsulated (MEC) pheromone formulations that enable the application of pheromone controls with other orchard sprays and assist in the development of multispecies mating‐disruption systems are currently under development. Responses of male Choristoneura rosaceana (Harris) and Pandemis limitata (Robinson) (Lepidoptera: Tortricidae) to calling females in clean air, and air treated with their major pheromone component (Z)‐11‐tetradecenyl acetate (Z11‐14:OAc), released from a 3M sprayable pheromone formulation containing proprietary 3M Phase I microcapsules, applied at doses of 1, 10, and 100 mg of active ingredient (ai) m−2 to the upwind end of a flight tunnel (equivalent to field rates of 10, 100, and 1000 g ai ha−1) were compared in laboratory flight tunnels. In both species, disorientation was found to be dose‐dependent, because relative to male orientation to calling females in clean air, the orientation of male P. limitata was disrupted 23.3, 46.3, and 71.3%, and orientation by male C. rosaceana was disrupted 31.6, 37.7, and 45.8% by treatment doses of 1, 10, and 100 mg m−2, respectively. Latency of male responses to calling females in a background of Z11‐14:OAc relative to responses in clean air was also dose‐dependent. Albeit short, the disruption lasted 26, 74, and 218 h in P. limitata and 30, 54, and 174 h in C. rosaceana at each application rate, respectively. Disruption by pheromone treatment was greater in P. limitata than in C. rosaceana. This difference may be correlated with species’ differences in the pheromone release rates of females. Mechanisms of disruption invoked by this 3M MEC pheromone formulation are discussed in relation to issues of its longevity and observed differences in the effects against the two species. It appears possible to evaluate relative activity of MEC pheromones in a laboratory setting which may aid in development of new formulations for mating disruption.

Phenylacetaldehyde attracts male and female apple clearwing moths, Synanthedon myopaeformis, to inflorescences of showy milkweed, Asclepias speciosa

Synanthedon myopaeformis Borkhausen (Lepidoptera: Sesiidae) is a diurnal clearwing moth native to Eurasia that was recently introduced into British Columbia (BC) and Ontario, Canada, where it has become a serious pest in apple orchards. In BC, these moths commonly feed on nectar of inflorescences, particularly that of showy milkweed, Asclepias speciosa Torrey (Apocynaceae). We investigated the relative importance of visual and olfactory cues, and the key floral semiochemical(s) mediating attraction of S. myopaeformis to A. speciosa. In field experiments, inflorescences left exposed or enclosed in cheesecloth bags dyed green induced similar visitation rates by moths, indicating that olfactory cues are attractive. Among the >10 floral odourants that elicited responses from moth antennae in coupled gas chromatographic‐electroantennographic detection analyses, phenylacetaldehyde induced the most frequent proboscis extension reflexes of male and female moths. Among eight floral odourants that were field‐tested singly, phenylacetaldehyde attracted 35 times more male and female moths than any other candidate semiochemical. Attractiveness of phenylacetaldehyde could not be enhanced by admixture with other floral odourants at the ratios or concentrations tested indicating that it alone may mediate attraction of S. myopaeformis to the inflorescences of A. speciosa. The potential use of phenylacetaldehyde as bait to monitor or mass‐trap populations of male and female S. myopaeformis should be investigated.

Operational mark–release–recapture field tests comparing competitiveness of wild and differentially mass-reared codling moths from the Okanagan–Kootenay sterile insect program

Abstract Pheromone trap catches and mating activity of sterile, mass-reared, diapaused and non-diapaused male codling moths, Cydia pomonella (L.) (Lepidoptera: Tortricidae), were compared with those of wild diapaused males using mark—release—recapture field experiments in springtime. Sterile moths were provided by the Okanagan—Kootenay Sterile Insect Release (SIR) Program mass-rearing facility, in Osoyoos, British Columbia, Canada. Nondiapause-reared (SIR-standard) and diapause-reared (SIR-diapaused) sterile males were recaptured in similar frequencies. Both types of sterile males were recaptured significantly less often than similarly released wild diapaused males, and ratios of recaptured sterile to wild males were similar with either sterile male. Ratios of sterile to wild males, using the combined catches of SIR-standard and SIR-diapaused males, were significantly lower when measured with traps baited with wild-females (21:1) than with traps baited with 10 µg pheromone (48:1). Both trapping ratios were markedly lower than the 80:1 ratio at which sterile and wild males were released. In mating studies, SIR-standard and SIR-diapaused males exhibited equivalent mating frequencies and both were recaptured in copula with tethered wild females significantly less often than released wild males. In the same mating studies, sterile mass-reared, diapaused males that had been chilled for 3 h at the Pacific Agri-Food Research Centre (PARC) before release (PARC-diapaused) were significantly more competitive than SIR-standard or SIR-diapaused males that averaged 24 h of chilling as part of normal SIR Program operations. PARC-diapaused males and released wild males mated with tethered females with equal frequency. We hypothesize that the length of time SIR males were chilled before being released may have caused SIR-diapaused males to be less mobile, and therefore less competitive with wild males in field mating assays, than were PARC-diapaused males. Based on these results, introduction of a diapause phase into the mass-rearing system used at the Osoyoos facility cannot currently be recommended as a means of improving trap-measured ratios of sterile to wild males, or increasing sterile × wild matings.