A. R. Gibb

Behavioral and Electrophysiological Responses of Arhopalus tristis to Burnt Pine and Other Stimuli

The exotic longhorn beetle Arhopalus tristisis a pest of pines, particularly those damaged by fire, and a major export quarantine issue in New Zealand. Actinograph recordings of caged individuals showed that males and females were most active from dusk to midnight. Olfactometer experiments indicated that females moved upwind toward odors from burnt pine (80%, N= 75), compared to unburnt pine (20%). Oviposition choice tests showed that eggs were predominantly laid on burnt logs (79%, N= 20), compared to unburnt logs. Beetles were trapped by funnel traps baited with burnt (mean catch per trap 7.8) and unburnt (mean catch 4.1 per trap) pine bark from inside a screen cage (4 × 3 m), while unbaited traps had a mean catch 0.1 beetles (N= 8 replicates). The treatment of burnt pine bark with a 1:1:2 mixture of green leaf volatiles (E)-2-hexen-1-ol and (E)-2-hexenal) in mineral oil as a repellent reduced trap catch by fivefold in a similar experiment (mean catches of 1.2 beetles per trap to burnt pine bark plus repellent treatment and 6.2 beetles per trap to burnt pine bark alone). The treatment of burnt pine bark with this solution also reduced oviposition by 98.5% (mean eggs per log of 11.1 on burnt pine and 0.3 on burnt pine plus repellent), indicating that oviposition cues have the potential to be significantly disrupted. The electrophysiological responses of adult beetles were recorded to a range of odorants. Normalized responses to monoterpenes known to occur in Pinus radiataranged from about 20 to about 150, with α-terpineol giving the greatest responses in both sexes. Green leaf volatiles also gave high responses. The potential exists to improve the management of this insect using chemical cues in various ways.

Electroantennogram and oviposition responses of Epiphyas postvittana (Lepidoptera: Tortricidae) to plant volatiles

Abstract Electroantennogram (EAG) responses of male and female Epiphyas postvittana (lightbrown apple moth) were recorded to plant volatiles delivered from either filter paper or a gas chromatograph. Males showed significantly higher EAG responses than females with both methods (P < 0.001). Responsiveness to compounds was significantly correlated between sexes and between methods (P < 0.01). Pairs of moths were caged with access to filter paper treated with plant volatiles, and untreated filter paper, for oviposition. The number of females ovipositing, the number of eggs laid, and the proportion of total eggs laid on the treated paper were recorded to determine the attractancy or repellency of the compounds. Eugenol, geraniol, and citral deterred oviposition, whereas hexanal, linalool, nonanol, octanol, and nonanal were attractants. The proportion of females laying eggs was reduced in the presence of citral, nonanol, octanol, and n‐decyl aldehyde. The number of fertile eggs laid per female was reduced by ...

Uraba lugens (Lepidoptera: Nolidae) in New Zealand: Pheromone Trapping for Delimitation and Phenology

Abstract A synthetic sex pheromone trapping survey of the leaf skeletonizer Uraba lugens Walker (Lepidoptera: Nolidae) demonstrated the unexpectedly widespread distribution of the insect across >40,000 ha of urban Auckland, New Zealand. A survey of eucalyptus trees planted in parks and other public areas showed a significant spatial correlation between trap catch and breeding populations, validating the trap survey results. Traps in trees showing damage had four-fold higher catches than traps placed in undamaged or nonhost trees, and <1% of damaged trees with traps failed to catch adult moths. Damage by larval feeding was correlated with male trap catch in the previous generation, offering good prospects for a pest management decision support system, provided that an economic threshold is developed. Catches increased by 3.4-fold in the same georeferenced trapping grid between November and December 2003 and between March and April 2004 across two generations, over the summer. A vertical transect showed that catches increased with height up to the top trap at 13 m (60% of mean tree height). Options for managing the insect will need to overcome the high rate of increase, the rate of spread, and the vertical distribution of the insect on tall eucalyptus trees.

Optimization of pheromone lure and trap characteristics for currant clearwing, Synanthedon tipuliformis.

Currant clearwing Synanthedon tipuliformis (Sesiidae) has been a pioneering and successful target of mating disruption in New Zealand, with virtually universal black currant industry adoption since c. 1990. Recent unexplained control failures using mating disruption lead to questions about pheromone efficacy. In this study, we have investigated the possible reasons for reduced control from mating disruption, and report improvements in trap catch based on pheromone loading and trap color. No differences were found in electrophysiological responses to pheromone components from two New Zealand populations. Male moth catches in traps baited with synthetic lures were disrupted in the presence of mating disruption dispensers (> 99.99%) indicating no apparent barrier to efficacy from the pheromone formulation. Field behavioral observations confirmed this result. Male attraction to yellow delta traps was equivalent to green delta traps, but was greater than to red, black, blue, or white traps. Solid yellow delta traps were more attractive than black traps with yellow stripes, the latter designed to mimic the color pattern of the insect. Solid yellow funnel traps were less attractive than a composite of green, yellow, and white funnel traps. Trap catch increased as a function of pheromone loading and trap color. In another experiment conducted in Tasmania, there was no difference in catch with single component [(E,Z)-2,13-octadecadienyl acetate] or two component lures [97% (E,Z)-2,13-octadecadienyl acetate:3% (E,Z)-3,13-octadecadienyl acetate], refuting the suggestion of a different pheromone strain there.

Plant and host effects on the leafroller parasitoid Dolichogenidia tasmanica

Parasitism by the braconid wasp Dolichogenidia tasmanica of first instar larvae of the lightbrown apple moth Epiphyas postvittana, established on four different species of potted host plants, was assessed after 2 weeks of field exposure in an apple orchard. Parasitism varied significantly between larval host plants (apple 58%, broom 59%, clover 30%, poplar 19% ). Parasitism on potted apple seedlings of the co‐evolutionary host, E. postvittana, was compared in a field trial with that of two native New Zealand leafroller species (to which D. tasmanica has had exposure for 5 decades only). Parasitism varied significantly with larval host (E. postvittana, 83%; Ctenopseustis herana, 58%;Planotortrix octo, 26% ). Larval collections were made from mature apple trees and identification of larvae was achieved by DNA analysis for the leafroller species using PCR‐RFLP of ITS1 + ITS2, and for the parasitoid by specific PCR of partial 18S. Parasitism under natural field conditions on mature apple trees was not different between larval hosts (mean 32.5% ). In laboratory studies, more P. octo larvae departed in response to parasitoid probing behaviour than E. postvittana, which is likely to contribute to the difference in parasitism rates. This study conclusively shows that D. tasmanica parasitises native New Zealand leafrollers, despite their different evolutionary origins.

Identification of sex pheromone components of the painted apple moth: a tussock moth with a thermally labile pheromone component.

The sex pheromone of the painted apple moth, Teia anartoides (Lymantriidae) was investigated using GC-EAD and GC-MS analysis, derivatization, TLC analysis, and field cage and field trapping bioassays. The major sex pheromone components were identified as (6Z,9Z)-henicosa-6,9-dien-11-one and (6Z,9Z)-henicosa-6,9-diene. Other minor components of pheromone gland extracts included (6Z)-9R,10S-epoxyeicos-6-ene, (6Z)-9R,10S-epoxyhenicos-6-ene, (6Z,9Z)-henicosa-6,9-dien-11-ol, (6Z)-henicos-6-en-11-one, and (6Z, 8E)-henicosa-6,8-dien-11-one, but the roles of these minor components remain equivocal. In field cage and field experiments, a blend of all seven identified components [(6Z,9Z)-henicosa-6,9-dien-11-one (relative amount 100), (6Z,9Z)-henicosa-6,9-diene (100), (6Z)-9R,10S-epoxyeicos-6-ene (5), (6Z)-9R,10S-epoxyhenicos-6-ene (10), (6Z,9Z)-henicosa-6,9-dien-11-ol (5), (6Z)-henicos-6-en-11-one (1), and (6Z,8E)-henicosa-6,8-dien-11-one (25)] was as attractive to males as calling females, but tests with blends of the major component(s) with subsets of the minor components did not produce consistent results that unequivocally showed the various minor components to be critical components of the active blend. (6Z,9Z)-henicosa-6,9-dien-11-one is thermally labile and rearranges to (6Z,8E)-henicosa-6,8-dien-11-one and other products at ambient temperature, rendering the synthetic pheromone lure inactive after two days of field exposure.

Can Parasitoid Sex Pheromones Help in Insect Biocontrol? A Case Study of Codling Moth (Lepidoptera: Tortricidae) and Its Parasitoid Ascogaster quadridentata (Hymenoptera: Braconidae)

Abstract Synthetic female sex pheromone was used to monitor the phenology of male Ascogaster quadridentata Wesmael, an egg-larval parasitoid of codling moth, Cydia pomonella (L.), in conjunction with pheromone trapping of the moth and the banding of trees to determine larval parasitism. Catch of this parasitoid was typically ≈10 times less than the moth catch, and larval parasitism varied from 7 to 12%. The emergence of the parasitoid occurred slightly later than the female moth emergence, by both outdoor emergence cages and pheromone trapping. The seasonal activity of male parasitoids was otherwise synchronous with male codling moth flight. A survey of orchards in four regions of New Zealand showed considerable regional variation in the capture of the parasitoid in pheromone traps. The potential value of the parasitoid may be limited by the nil tolerance of the pest in export fruit, but pheromone trapping of this parasitoid could improve the understanding of biological control in non-export situations, where the economic threshold is higher. Pheromone trapping for insect biological control agents is a valuable tool that can help to determine and improve parasitoid success.

Identification of Sex Pheromone Components of a New Zealand Geometrid Moth, the Common Forest Looper Pseudocoremia suavis, Reveals a Possible Species Complex

Gas chromatography–electroantennographic detection analysis of sex pheromone gland extracts of the common forest looper Pseudocoremia suavis (Lepidoptera: Geometridae), a polyphagous defoliator of introduced Pinaceae and many New Zealand trees, revealed four compounds that elicited antennal responses. The two major active compounds (6Z)-cis-9,10-epoxynonadec-6-ene and (3Z,6Z)-cis-9,10-epoxynonadeca-3,6-diene were identified by comparison with known standards. Of the two minor active compounds, one was tentatively identified as (3Z,6Z)-cis-9,10-epoxyhenicosa-3,6-diene, whereas the other could not be identified because of insufficient amounts in extracts. (6Z)-cis-9,10-Epoxynonadec-6-ene, (3Z,6Z)-cis-9,10-epoxynonadeca-3,6-diene, and (3Z,6Z)-cis-9,10-epoxyhenicosa-3,6-diene were present in P. suavis gland extracts from Eyrewell Forest, a Pinus radiata plantation in the South Island of New Zealand, in a ratio of 35:65:5, respectively. Trapping trials in Eyrewell Forest established that (6Z)-cis-9,10-epoxynonadec-6-ene attracted male P. suavis. However, addition of (3Z,6Z)-cis-9,10-epoxyhenicosa-3,6-diene to the lure at <10% of (6Z)-cis-9,10-epoxynonadec-6-ene reduced capture of male moths, suggesting that one of its enantiomers was acting as a behavioral antagonist. During January–March of 2005, a blend trial involving single, binary, and ternary mixtures of the three components at Eyrewell Forest and at three other sites (two in the South Island and one in the North Island) revealed the existence of a second taxon of P. suavis at the three additional sites that was attracted to lures containing (3Z,6Z)-cis-9,10-epoxynonadeca-3,6-diene, either singly or in binary and ternary mixtures with (6Z)-cis-9,10-epoxynonadec-6-ene and (3Z,6Z)-cis-9,10-epoxyhenicosa-3,6-diene. This second taxon was not attracted to lures loaded solely with (6Z)-cis-9,10-epoxynonadec-6-ene.

The Effect of Atmospheric Pheromone Concentrations on Behavior of Lightbrown Apple Moth in an Apple Orchard

A previously validated Lagrangian model was used to estimate the threshold of atmospheric pheromone concentration required to prevent trap catch and wing fanning in mating disruption plots in an apple orchard. Electroantennogram (EAG) traces of 10 min duration were recorded, along with supporting meteorological data needed for the model, to better define the conditions in which successful mating disruption will occur. Pheromone was released from polyethylene tubing dispensers into orchard blocks treated with 10, 100, 1000, and 2000 dispensers/ha. Predicted dusk concentrations of atmospheric pheromone at a height of 1.85 m varied nightly between 4 and 90 ng pheromone/m3 (in plots treated with 1000 dispensers/ha) over 11 weeks. Disruption of traps baited with 1000-μg pheromone lures followed an asymptotic curve with predicted concentration, but they did not show a significant effect of trap height (1.5 and 3.0 m). Wing fanning was reduced by increasing the density of dispensers, but was not completely eliminated even at 1000 dispensers/ha. At this density, the concentrations were usually <16 ng pheromone/m3. Electroantennogram recordings of 10 min duration showed a higher frequency of pheromone pulses in plots treated with more point sources per hectare. There was also a positive correlation between the number of pulses recorded by the EAG and predicted concentration for plots treated with 1000 or 2000 dispensers/ha. These results give added support to our model of pheromone release and transport in treated apple orchards.

(11Z,13E) -hexadecadien -1 -yl acetate : Sex pheromone of the grass webworm Herpetogramma licarsisalis-identification, synthesis, and field bioassays

The grass webworm Herpetogramma licarsisalis (Lepidoptera: Crambidae), which has recently established in pasture in Northland, New Zealand, is an important pest of many tropical and subtropical grasses. Two pheromone components, (Z)-11-hexadecen-1-yl acetate (Z11–16:Ac) and (11Z,13E)-hexadecadien-1-yl acetate (Z11,E13–16:Ac), were identified in pheromone gland extracts of female moths by gas chromatography (GC), GC-electroantennographic detection, and GC-mass spectrometry in conjunction with microchemical tests (dimethyldisulfide and 4-methyl-1,2,4-triazoline-3,5-dione derivatizations). Z11,E13–16:Ac and its geometric isomer (11E,13Z)-hexadecadien-1-yl acetate (E11,Z13–16:Ac) were synthesized via stereoselective Wittig reactions, and the identity of the diene present in the pheromone glands was confirmed to be Z11,E13–16:Ac. Field bioassays at Indooroopilly in Brisbane, Australia, established that Z11,E13–16:Ac was necessary and sufficient for attraction of male grass webworm moths and that the corresponding alcohol, (11Z,13E)-hexadecadien-1-ol (Z11,E13–16:OH), had a strong inhibitory effect on trap catches at the ratios tested. When mixed with Z11,E13–16:Ac in various ratios, Z11–16:Ac had no effect on the attractiveness of lures.