Christelle Guédot

Multistate Comparison of Attractants for Monitoring Drosophila suzukii (Diptera: Drosophilidae) in Blueberries and Caneberries

ABSTRACT Drosophila suzukii Matsumara, also referred to as the spotted wing drosophila, has recently expanded its global range with significant consequences for its primary host crops: blueberries, blackberries, raspberries, cherries, and strawberries. D. suzukii populations can increase quickly, and their infestation is difficult to predict and prevent. The development of effective tools to detect D. suzukii presence in new areas, to time the beginning of activity within a crop, to track seasonal activity patterns, and to gauge the effectiveness of management efforts has been a key research goal. We compared the efficiency, selectivity, and relationship to fruit infestation of a range of commonly used homemade baits and a synthetic formulated lure across a wide range of environments in 10 locations throughout the United States. Several homemade baits were more efficient than apple cider vinegar, a commonly used standard, and a commercially formulated lure was, in some configurations and environments, comparable with the most effective homemade attractant as well as potentially more selective. All alternative attractants also captured flies between 1 and 2 wk earlier than apple cider vinegar, and detected the presence of D. suzukii prior to the development of fruit infestation. Over half the Drosophila spp. flies captured in traps baited with any of the attractants were not D. suzukii, which may complicate their adoption by nonexpert users. The alternative D. suzukii attractants tested are improvement on apple cider vinegar and may be useful in the development of future synthetic lures.

Identification of a Sex Attractant Pheromone for Male Winterform Pear Psylla, Cacopsylla pyricola

Pear psylla, Cacopsylla pyricola (Förster) (Hemiptera: Psyllidae), a major economic pest of pears, uses a female-produced sex attractant pheromone. We compared the chemical profiles obtained from cuticular extracts of diapausing and post-diapause winterform males and females to isolate and identify the pheromone. Post-diapause females produced significantly more of the cuticular hydrocarbon, 13-methylheptacosane, than post-diapause males and diapausing females. In olfactometer assays, conspecific males were attracted to synthetic racemic 13-methylheptacosane, whereas females were not, indicating that the behavioral response to this chemical is sex-specific. Furthermore, 13-methylheptacosane was as attractive to males as a cuticular extract of females, suggesting that this chemical was largely responsible for the female attractiveness. A field study showed that males but not females were attracted to 13-methylheptacosane, confirming the olfactometer results. This study provides evidence that 13-methylheptacosane is a sex attractant pheromone for C. pyricola winterform males. This is the first identification of a sex pheromone in the Psylloidea. Our results open the path to developing monitoring tools and possibly new strategies for integrated pest management of this insect.

Relationship between body size and homing ability in the genus Osmia (Hymenoptera; Megachilidae).

Abstract 1. The maximum homing ability of female bees, that is, their capacity to return to the nest after being displaced a certain distance, is considered to be an estimate of their maximum foraging distance.

Deciphering the routes of invasion of Drosophila suzukii by means of ABC random forest

Abstract Deciphering invasion routes from molecular data is crucial to understanding biological invasions, including identifying bottlenecks in population size and admixture among distinct populations. Here, we unravel the invasion routes of the invasive pest Drosophila suzukii using a multi-locus microsatellite dataset (25 loci on 23 worldwide sampling locations). To do this, we use approximate Bayesian computation (ABC), which has improved the reconstruction of invasion routes, but can be computationally expensive. We use our study to illustrate the use of a new, more efficient, ABC method, ABC random forest (ABC-RF) and compare it to a standard ABC method (ABC-LDA). We find that Japan emerges as the most probable source of the earliest recorded invasion into Hawaii. Southeast China and Hawaii together are the most probable sources of populations in western North America, which then in turn served as sources for those in eastern North America. European populations are genetically more homogeneous than North American populations, and their most probable source is northeast China, with evidence of limited gene flow from the eastern US as well. All introduced populations passed through bottlenecks, and analyses reveal five distinct admixture events. These findings can inform hypotheses concerning how this species evolved between different and independent source and invasive populations. Methodological comparisons indicate that ABC-RF and ABC-LDA show concordant results if ABC-LDA is based on a large number of simulated datasets but that ABC-RF out-performs ABC-LDA when using a comparable and more manageable number of simulated datasets, especially when analyzing complex introduction scenarios.

Olfactory cues and nest recognition in the solitary bee Osmia lignaria

Abstract.  The use of olfactory cues for nest recognition by the solitary bee Osmia lignaria is studied in a greenhouse environment. Glass tubes are provided as nesting cavities to allow the in‐nest behaviour of bees to be observed. In addition, each glass tube is cut into three sections for experimental manipulation and for subsequent chemical analysis. Nesting females drag their abdomen along the tube before exiting, spiral inside the tube, and sometimes deposit fluid droplets from the tip of the abdomen. For the manipulation, the outer section, the middle section, or both sections are removed and replaced with similar clean glass tube sections, and the behaviour exhibited by test females is recorded upon arrival in front of the nesting site and inside the nesting tubes. The resulting hesitation behaviour displayed by females after treatments appears to indicate the loss of some olfactory cues used for nest recognition inside the entire nest. Chemical analysis of the depositions inside the nesting tube, as well as analysis of the cuticular lipids of the nesting bees, reveals the presence of free fatty acids, hydrocarbons and wax esters.

Sex Attraction in Bactericera cockerelli (Hemiptera: Triozidae)

ABSTRACT The potato psyllid, Bactericero. (=Paratrioza) cockerelli (Šulc) (Hemiptera: Triozidae), is a major pest of potato. We examined the role of chemical signals in sex attraction, assessing male and female response to male- and female-produced volatile chemicals. In laboratory olfactometer assays, potato psyllid males were attracted to odorants emitted from live females and from solvent extract of females. These results indicate that the female-produced chemicals responsible for attracting males may be isolated by means of insect extractions. Males were also attracted to volatile chemicals from males and extracts of males, providing the first example of male—male attraction in the Psylloidea. Males exposed simultaneously to odorants from conspecific females and males were preferentially attracted to female odorants, suggesting the presence of a female-specific sex attractant for males. Potato psyllid females avoided volatile chemicals emitted by females and extracts of females and by volatile chemicals emitted by males and extracts of males. Possible explanations for avoidance of conspecifics by females are discussed. This study is the first report of male attraction to volatile chemicals emitted by females and female extracts in the Triozidae and more specifically in the potato psyllid.

Odorants of the Flowers of Butterfly Bush, Buddleja Davidii, as Possible Attractants of Pest Species of Moths

Abstract Flowers of the butterfly bush, Buddleja davidii Franch., are visited by butterflies as well as other insects. Night captures revealed also that moths visit butterfly bush flowers. Moths captured in traps over flowers included 12 species of Noctuidae, 6 species of Pyralidae, 2 species of Geometridae, and 1 tortricid species. The majority of moths trapped at these flowers were cabbage loopers, Trichoplusia ni (Hübner), and alfalfa loopers, Autographa californica (Speyer). Both males and females were captured at butterfly bush flowers. Additionally, butterflies, bees, wasps, flies, and other insects also were captured. Analysis of volatile compounds collected from air over clusters of butterfly bush flowers yielded the consistent presence of nine chemicals: benzaldehyde, 6-methyl-5-hepten-2-one, hexyl acetate, 4-oxoisophorone, (E,E)-α-farnesene, (Z)-cinnamaldehyde, dihydrooxoisophorone, β-cyclocitral, and oxoisophorone oxide. Emitted amounts of these floral odorants averaged 57 ng per h per floret or 21 μg per h per flower cluster (raceme). Five of those floral chemicals, benzaldehyde, 4-oxoisophorone, dihydrooxoisophorone, oxoisophorone oxide, and (E,E)-α-farnesene triggered antennal responses in cabbage looper moths, while benzaldehyde, oxoisophorone oxide, and 4-oxoisophorone also stimulated antennal responses in alfalfa looper moths. Some of these compounds may be attractants or co-attractants for moths and play a key role in locating flowers as nectar sources.

Field Attraction of Codling Moths (Lepidoptera: Tortricidae) to Apple and Pear Fruit, and Quantitation of Kairomones from Attractive Fruit

Abstract Male and female codling moths, Cydia pomonella (L.) (Lepidoptera: Tortricidae) responded to fruit-baited traps in orchards. Numbers of codling moths trapped with immature uninfested apples (Malus spp.), immature apples infested with larval codling moth, fresh ripe apples, stored ripe apples, or fresh ripe pears (Pyrus spp.) were significantly greater than in unbaited traps. Greatest numbers of codling moths were captured in traps baited with ripe ‘Bartlett’ pears, but direct comparisons of these fruit types were not made. Females captured in traps baited with ripe apples or pears were primarily mated and had developing or mature eggs, and smaller numbers of females trapped were unmated without eggs or were postreproductive. Volatile compounds sampled from infested immature ‘Red Delicious’ apples that were attractive in traps showed emission of two known codling moth host kairomones: (E,E)-α-farnesene as well as small amounts of β-caryophyllene. Collections of volatile chemicals from ripe ‘Braeburn’ apples that were attractive in traps showed strong emission of the codling moth kairomones 2-methylbutyl acetate, butyl hexanoate, hexyl hexanoate, and (E,E)-α-farnesene, and very small amounts of the kairomones (R)-limonene and (E)-β-farnesene. Volatile collections made from ripe Bartlett pears that were attractive in traps indicated strong emission of the codling moth kairomones butyl hexanoate, ethyl (E,Z) 2,4-decadienoate and (E,E)-α-farnesene, and small amounts of the kairomones 2-methylbutyl acetate, hexyl hexanoate, β-caryophyllene, (E)-β-farnesene, and (E,E)-farnesol.

Diapause status of females affects attraction of male pear psylla, Cacopsylla pyricola, to volatiles from female‐infested pear shoots

A companion study showed that male pear psylla, Cacopsylla pyricola (Förster) (Homoptera: Psyllidae) were attracted to volatiles from pear shoots infested with post‐diapause females. The present study compared the behavioral response of males to diapause and post‐diapause females. Assays were done using a Y‐tube olfactometer. We collected male and female winterform psylla from pear orchards at regular intervals between late October (early diapause) and late February (post‐diapause). Female‐infested shoots were not attractive to males until the February samples, coinciding with ovarian maturation and onset of mating in the field. A second set of assays was done in which we manipulated diapause status in the laboratory either by exposing psylla to a long‐day photoperiod or by treating insects with an insect growth regulator, fenoxycarb. In the photoperiod experiments, both short‐day and long‐day males preferentially selected long‐day (post‐diapause) females over short‐day (diapause) females. Fenoxycarb‐treated males preferred fenoxycarb‐treated (post‐diapause) females over untreated (diapause) females; untreated males showed no preferences. Results support observations made elsewhere that male winterform pear psylla perceive and are attracted to volatile odors associated with pear shoots infested with post‐diapause females.

Cuticular lipids of female solitary bees, Osmia lignaria Say and Megachile rotundata (F.) (Hymenoptera: Megachilidae).

The cuticular lipids of the cavity-nesting adult female solitary bees, Osmia lignaria Say and Megachile rotundata (F.) (Hymenoptera: Megachilidae), were analyzed by gas chromatography (GC) and combined GC-mass spectrometry. The cuticular lipids of these female bees are mainly consisted of hydrocarbons. For O. lignaria, nearly 64% of the cuticular lipids were C(25)-C(31) mono-alkenes. For M. rotundata, 48% of the cuticular lipids were C(23)-C(33) alkanes with nearly the same quantities of the same chain-length mono-alkenes (45%). For the mono-alkenes of O. lignaria, 14 mono-alkene constituents were identified, with two of these, 9-heptacosene and 7-nonacosene, comprising 67% of the total alkene distribution. For M. rotundata females, the mixtures of mono-alkenes were more complex with 26 constituents identified and quantified. For the M. rotundata mono-alkenes, 57% of the total composition consisted of the three alkenes, 7-pentacosene, 9-pentacosene and 7-heptacosene. For both bee species, small quantities of C(40)-C(48) wax esters were also characterized with the major components possessing a C(18) mono-unsaturated fatty acid (9-octadecenoate) moiety esterified to even-carbon number (C(22-30)) fatty alcohols. The possible role of these cuticular lipids as nest recognition chemicals is discussed in light of nesting behavior of managed crop pollinators.