Boyd A. Mori

When mating disruption does not disrupt mating: fitness consequences of delayed mating in moths

The goals of pheromone‐mediated mating disruption are to interfere with mate finding, suppress insect population growth, and prevent crop damage. In addition to prevention of mating, pheromone treatment can also result in a delay of mating so that the fitness and subsequent population dynamics of the target insect pest are impacted. Females have a limited time to mate, mature eggs, and find suitable oviposition hosts, and a delay in mating can have large consequences on female fitness. As a result, delayed mating could be considered an indirect method by which mating disruption works to control pest populations. We perform a meta‐analysis on 24 experimental studies to assess the consequences of delayed mating on female moth fecundity, egg fertility, adult longevity, and pre‐oviposition period. Our goal is to determine whether the effect of delayed mating on female moth fitness is influenced by the following explanatory variables: moth family, voltinism, larval diet breadth, adult dispersal capacity, female mating strategy, and egg development strategy. Across species, the effect of delayed mating on female moths significantly decreases fecundity, fertility, and pre‐oviposition period and increases female longevity. The effect of delayed mating on female fitness is only marginally affected by the explanatory variables tested. We discuss the observed patterns and argue that delayed mating can be an important method by which population regulation is achieved through pheromone‐mediated mating disruption. Finally, we highlight areas where future research could add to the growing body of knowledge on mating disruption‐imposed delayed mating of female moths.

Sex pheromone of the red clover casebearer moth, Coleophora deauratella, an invasive pest of clover in Canada

The red clover casebearer, Coleophora deauratella Lienig & Zeller (Lepidoptera: Coleophoridae), is an invasive pest of Trifolium species (Fabaceae) in Canada. We identified candidate sex pheromone components from female pheromone gland extracts using coupled gas chromatographic–electroantennographic analysis detection. Three compounds elicited an electrophysiological response from antennae and were identified as: (Z)‐7‐dodecenyl acetate, (Z)‐5‐dodecenyl acetate, and (Z)‐7‐dodecen‐1‐ol. Field tests of the candidate pheromone components revealed that males were attracted to a binary mixture of (Z)‐7‐dodecenyl acetate and (Z)‐5‐dodecenyl acetate. Male moth trap capture was greatest in traps baited with lures containing 100:10 or 100:20 ratios of these pheromone components, respectively. Trap capture was reduced when (Z)‐5‐dodecenyl acetate was present below 10 or above 20% of (Z)‐7‐dodecenyl acetate. Equal numbers of male moths were captured in traps baited with 10, 100, and 1 000 μg of the attractive binary mixture. These findings allow for the development of a pheromone‐based monitoring system for this invasive pest of clover in Canada.

Relationships among male Coleophora deauratella (Lepidoptera: Coleophoridae) pheromone-baited trap capture, larval abundance, damage and flight phenology

The red clover casebearer Coleophora deauratella Leinig and Zeller is an invasive pest of red clover (Trifolium pratense L.) grown for seed production in Canada. Drastic yield losses (80–99.5%) have been reported in several growing regions over the last 30 years as a result of larval feeding damage. Field trials conducted in red clover seed production fields in Alberta, Canada, during the summers of 2010–2012 tested the efficacy of pheromone‐baited traps to predict population density and assess male flight phenology of C. deauratella. Male moth pheromone‐trap capture was positively related to larval abundance and proportion seed damage at both moderate and high population densities. Phenological models based on degree days (DD11.7) were better at describing median (50%) male flight compared with ordinal date models. Median C. deauratella male flight occurs at 258.39 DD11.7, starting from 1 January each year in the Peace River region of Alberta. The results obtained in the present study demonstrate that pheromone‐baited traps can be used to detect the spread of this invasive species. Future work could incorporate pheromone‐based monitoring into assessment for the need and timing of control measures to target this invasive pest.

Factors Affecting Pheromone-Baited Trap Capture of Male Coleophora deauratella, an Invasive Pest of Clover in Canada

ABSTRACT Coleophora deauratella Leinig and Zeller (Lepidoptera: Coleophoridae) is an invasive pest of red clover, Trifolium pratense L. (Fabeles: Fabaceae), grown for seed in Canada. A pheromone-based monitoring program to determine the presence and seasonal activity of adult C. deauratella would be a valuable tool for growers because larvae are difficult to sample due to their internal feeding behavior. We conducted field experiments to evaluate several pheromone-baited trap characteristics, including pheromone lure substrate, trap type, trap color, lure longevity, trap height, and field position. The type of substrate that pheromone was released from and lure age did not affect trap capture of male C. deauratella. Moth capture in nonsaturating green Unitraps was significantly higher than Diamond or Wing traps when inspected at 2-wk intervals. Multi-colored Unitraps caught significantly more male C. deauratella than Diamond, and Wing traps when inspected at weekly intervals. Trap color did not influence C. deauratella capture, but by-catch of bumblebees, Bombus spp., was greatest in yellow and white colored Unitraps. Traps placed 35 cm above the soil surface captured more male C. deauratella than those placed at 1 m above or at ground level regardless of trap position within the field. Green Unitraps baited with either gray or red rubber septa lures placed 35 cm above the soil surface and 5 m from the field edge should be used to monitor C. deauratella. These characteristics optimize pheromone-baited trap performance and reduce by-catch of beneficial insects, and should be incorporated into a C. deauratella pheromone-monitoring program.

Phoretic Mite Associates of Mountain Pine Beetle at the Leading Edge of an Infestation in Northwestern Alberta, Canada

Abstract We identified species of mites phoretically associated with mountain pine beetle, Dendroctonus ponderosae Hopkins (Coleoptera: Curculionidae: Scolytinae), collected from bolts of lodgepole pine, Pinus contorta Douglas ex Louden (Pinaceae), and pheromone-baited traps in northwestern Alberta, Canada. Mite load and species composition were compared between beetle sexes and with beetle emergence time and estimated body size. The vast majority of mites associated with D. ponderosae in Alberta belonged to three species: Proctolaelaps subcorticalis Lindquist (Acari: Mesostigmata: Melicharidae), Histiogaster arborsignis Woodring (Acari: Astigmatina: Acaridae), and Tarsonemus ips Lindquist (Acari: Prostigmata: Tarsonemidae). There was no difference in mite loads on male and female beetles recovered from bolts in the laboratory and those from pheromone-baited traps in the field. More mites were found on larger beetles in the laboratory, but only T. ips showed this pattern on field-trapped beetles. There was no relationship between total mite load or load by mite species and beetle emergence time in the laboratory, but total mite load on field-trapped beetles decreased over the collecting season (10 June – 3 September 2009) at five collection locations (Grovedale, Blueberry Mountain, Hythe, Evergreen Park, and Glenleslie). This study is the first to document the assemblage of phoretic mites on D. ponderosae in Alberta and will help to direct future research on their interactions.

Genetic diversity and population structure identify the potential source of the invasive red clover casebearer moth, Coleophora deauratella, in North America

The red clover casebearer, Coleophora deauratella, is an invasive pest of red clover grown for seed in North America. In 2006, an outbreak in Alberta, Canada was discovered that resulted in significant seed losses, while further invasion threatens the world’s largest red clover forage seed production region in Oregon, USA. Prior to the recent outbreak, C. deauratella was thought to be restricted to eastern North America in its invasive range. We sequenced a 615-bp fragment of the mitochondrial cytochrome c oxidase subunit 1 gene, and developed three microsatellite markers to assess the genetic diversity and population structure of C. deauratella in North America and its native range in Europe. We observed signatures of a founder effect in North American populations and a further loss of genetic diversity within Alberta populations. Most genetic differentiation was found between continents, with no evidence of isolation-by-distance within each continent. From the limited number of European populations sampled, a single introduction from Switzerland is the most probable source of North American populations based on similar mitochondrial diversity and lack of population differentiation. Within North America, based on increased genetic diversity compared to the rest of the continent, the first North American record from Ithaca, NY, and the first documented outbreak in southern Ontario in 1989, the initial C.deauratella invasion most likely occurred in southern Ontario, Canada or adjacent states in the USA, followed by transport throughout the continent. This study provides insight into the phylogeographic history of C.deauratella in North America and Europe and may help to identify a regional source of future classical biological control agents.

Mating disruption of Coleophora deauratella (Lepidoptera: Coleophoridae) using laminate flakes in red clover seed production fields

BACKGROUND The red clover casebearer, Coleophora deauratella, is a significant pest in red clover (Trifolium pratense) seed production regions throughout the world. The internal feeding nature of C. deauratella larvae makes infestations difficult to control with insecticide. We test the ability of Hercon Disrupt Micro-Flakes(®) releasing the complete pheromone blend of C. deauratella to disrupt communication and mating in red clover seed production fields. RESULTS Initial small-plot (0.25 ha) trials found a significant reduction (93.6 ± 2.9%) of male C. deauratella captured in pheromone-treated plots compared with untreated controls. Subsequent large-plot (5 ha) mating disruption trials found a significant reduction (72.3 ± 5.7%) in male C. deauratella captured in pheromone-treated plots compared with untreated control plots over the growing season. Furthermore, larval numbers were significantly reduced and seed yield was increased in pheromone-treated plots compared with untreated control plots. In a concurrent small-plot (0.0625 ha) trial with various flake densities, disruption increased with pheromone flake density, and the resulting graphical disruption profiles matched the theoretical predictions of mating disruption by competitive attraction. CONCLUSION Pheromone-mediated mating disruption with laminate flakes has the potential to suppress C. deauratella populations and may help to reduce damage even at high pest densities.

Forest tent caterpillar, Malacosoma disstria (Lepidoptera: Lasiocampidae), mate-finding behavior is greatest at intermediate population densities: implications for interpretation of moth capture in pheromone-baited traps

The forest tent caterpillar, Malacosoma disstria Hubner (Lepidoptera: Lasiocampidae) is a native forest defoliator with a broad geographic range in North America. Forest tent caterpillars experience cyclical population changes and at high densities, repeated defoliation can cause reduced tree growth and tree mortality. Pheromone-based monitoring of forest tent caterpillar moths can provide information on spatial and temporal patterns of incipient outbreaks. Pheromone-baited trap capture of male moths correlates to the number of eggs and pupae in a population but this relationship breaks down at high population densities, when moth trap capture declines. The objective of the current study is to understand the mechanisms that reduce trap capture at high population densities. We tested two different hypotheses: 1) at high population densities, male moth orientation to pheromone sources is reduced due to competition for pheromone plumes; and 2) moths from high density populations will be in poor condition and less likely to conduct mate-finding behaviors than moths from low density populations. A field study showed non-linear effects of density on male moth capture in female-baited traps. The number of males captured increased up to an intermediate density level and declined at the highest densities. Field cage studies showed that female moth density affected male moth orientation to female-baited traps, as more males were recaptured at low than high female densities. There was no effect of male density on the proportion of males that oriented to female-baited traps. Moth condition was manipulated by varying larval food quantity. Although feeding regimes affected the moth condition (size), there was no evidence of an effect of condition on mate finding or close range mating behavior. In the field, it is likely that competition for pheromone plumes at high female densities during population outbreaks reduces the efficacy of pheromone-baited monitoring traps.

Challenges of Mating Disruption using Aerosol-Emitting Pheromone Puffers in Red Clover Seed Production Fields to Control Coleophora deauratella (Lepidoptera: Coleophoridae)

ABSTRACT Sex pheromone-mediated mating disruption using pheromone puffer dispensers was evaluated to control Coleophora deauratella (Lepidoptera: Coleophoridae) at three red clover seed production fields in Alberta, Canada. The objectives of the study were to determine aspects of the biology of C. deauratella which may affect successful mating disruption, evaluate the ability of aerosol-emitting pheromone puffers to reduce male moth catch in small-plot trials, and evaluate the ability of puffers to reduce male capture in traps, larval numbers and damage in large-plot trials. The median longevity of male and female C. deauratella was 6 d in the laboratory where males emerged in larger numbers earlier than females (protandry). Male response to pheromone peaked at sunrise; thus, puffers were programmed to dispense pheromone throughout this time period. Small-plot (0.25 ha) mating disruption trials indicated that pheromone released from puffers could reduce male C. deauratella orientation to traps by 60.7±18.6% compared with that in untreated control plots. Reduction of male orientation to traps in large-plot (5 ha) trials over the course of the season was also successful (93.7±1.6%). However, there was no corresponding decrease in larval numbers or increase in seed yield in pheromone-treated plots. Challenges of mating disruption of C. deauratella appear to be immigration of mated females combined with high population densities.

Nutrition, sex and season contribute to variation in fat and glycerol levels in the long-lived moth Caloptilia fraxinella

The ash leaf cone roller Caloptilia fraxinella Ely (Lepidoptera: Gracillariidae) is an invasive leaf‐mining moth pest of horticultural ash Fraxinus spp. in the Canadian Prairie Provinces. Caloptilia fraxinella overwinter as adults in reproductive diapause and mating occurs after overwintering in the spring. The effect of a carbohydrate food source on fat and glycerol reserves throughout the long adult life stage of this moth is investigated. Insects collected as pupae are given access to either water or sugar water upon adult eclosion. Moths held under the different feeding regimes are sampled before (summer and autumn) and after overwintering in the spring. Analysis of either glycerol or lipid content is conducted for male and female moths from each collection period. Both moth weight and glycerol concentration are affected by moth sex, food regime and season of collection. Although female moths are heavier than males, a higher glycerol concentration occurs in males. Moths fed sugar are heavier and have a higher glycerol concentration than water‐fed moths late in reproductive diapause and after overwintering. Moths collected in the spring after overwintering are lighter and have a lower glycerol content than moths collected before winter. There is a significant influence of feeding regime and season on moth body lipid content, with sugar‐fed moths having more fat than water‐fed moths; however, this difference is smaller in the summer than the autumn or spring. An initial understanding of the overwintering biology and diapause of this pest is provided in the present study.