Allard A. Cossé

Antennally Active Macrolide from the Emerald Ash Borer Agrilus planipennis Emitted Predominantly by Females

The macrocyclic lactone (3Z)-dodecen-12-olide was identified from the emissions of the emerald ash borer, Agrilus planipennis, feeding on ash foliage. The compound was detected from both sexes but was ca. 10 times more abundant from females. It was readily sensed by antennae of both males and females. Identification was confirmed by synthesis. The behavioral effects of the lactone remain unstudied in A. planipennis, but a verified pheromonal function could lead to improved monitoring for this invasive pest. The lactone is part of the pheromone of Cryptolestes pusillus, an unrelated beetle species.

Behaviorally Active Green Leaf Volatiles for Monitoring the Leaf Beetle, Diorhabda elongata, a Biocontrol Agent of Saltcedar, Tamarix spp.

Biological activity and chemistry of host plant volatiles were investigated for Diorhabda elongata, Brullé (Coleoptera: Chrysomelidae), a biological control agent for the invasive tree, saltcedar (Tamarix spp., Tamaricaceae). Gas chromatographic–electroantennographic detection (GC-EAD) analysis of volatiles collected from adult D. elongata feeding on saltcedar foliage or from saltcedar foliage alone showed 15 antennally active compounds. These compounds were more abundant in collections from beetle-infested foliage. Antennally active compounds were identified by GC–mass spectrometry (MS) and confirmed with authentic standards. The emissions of the most abundant GC-EAD-active compounds, green leaf volatiles (GLV), were quantitated by GC-MS. A blend of four GLV compounds, mimicking the natural blend ratio, was highly attractive to male and female D. elongata in the field, and a combination of GLV and male-produced aggregation pheromone attracted significantly greater numbers of D. elongata than did either bait alone. A preliminary experiment with a blend of seven additional GC-EAD-active saltcedar volatiles did not show any behavioral activity. The combination of the pheromone and the green leaf odor blend could be a useful attractant in detecting the presence of the biocontrol agent, D. elongata, in stands of saltcedar newly colonized by the beetle.

Biology of two members of the Euwallacea fornicatus species complex (Coleoptera: Curculionidae: Scolytinae), recently invasive in the U.S.A., reared on an ambrosia beetle artificial diet

Recent molecular studies have found that the ambrosia beetle Euwallacea fornicatus Eichhoff (Coleoptera: Curculionidae: Scolytinae) is a complex of cryptic species, each carrying a different species of symbiotic fungus, in the genus Fusarium, which they farm within galleries inside woody hosts. Several of these beetle species have become invasive pests around the world for attacking and infecting healthy trees with their phytopathogenic fungal symbionts. Diet and rearing protocols were developed for two members of the E. fornicatus species complex, polyphagous shot hole borer (PSHB) and tea shot hole borer (TSHB), using sawdust from host trees, allowing collection of data on beetle biology, phenology and sex ratios. Adults developed within 22u2009days at 24u2009°C. Single PSHB or TSHB foundresses averaged 32.4 and 24.7 adult female offspring, respectively, and up to 57 and 68 female adults within 6–7u2009weeks. A strong predictor of the number of offspring in a colony was the number of entry holes. Average sex ratios (% male) for PSHB and TSHB, respectively, were 7.4% and 7.2%. Being haplodiploid, virgin PSHB foundresses were able to produce and mate with male offspring, then subsequently produce female offspring, confirming that they have arrhenotokous reproduction. A cold tolerance study found significant mortality rates among PSHB colonies exposed to −5° or −1u2009°C but not colonies exposed to 0°, 1° or 5u2009°C. Given Hamiltons local mate competition (LMC) theory, a number of LMC predictions were violated. PSHB sex ratios were not affected by the number of foundresses; approximately 14% of broods did not contain males; males did not usually eclose before females but eclosed around the same time (22–23u2009days); and PSHB males were found walking outside of their natal galleries on the trunk of a heavily infested tree in the field. Alternatives to LMC are considered, such as early forms of sociality (maternal care, cooperative brood care), local resource enhancement and kin selection.

Male-produced aggregation pheromone of the lesser mealworm beetle, Alphitobius diaperinus.

The lesser mealworm beetle, Alphitobius diaperinus (Panzer), is a widespread serious pest in poultry production facilities and is difficult to control by conventional means. Although pheromone-based tools have become useful in the management of other beetle pests, no pheromone was known for A. diaperinus, and this study sought to develop basic pheromone information. Volatiles were collected in the laboratory from groups of male and female A. diaperinus maintained on poultry food (chick starter mash). Gas chromatographic–mass spectrometric analysis of volatiles collected from feeding males and females revealed five male-specific compounds that were identified as (R)-(+)-limonene, (E)-β-ocimene, (S)-(+)-linalool, (R)-(+)-daucene, and 2-nonanone. Emission of these began 1–2xa0weeks after adult emergence and could continue for at least 1xa0year, ceasing and resuming in response to changes in food availability and quality and other factors. No female-specific compounds were discovered. A synthetic blend of the five male compounds was attractive to both sexes in poultry production facilities in Illinois and Arkansas, indicating that the blend functions as an aggregation pheromone, but it is not yet known whether all five compounds are required for activity. A new pitfall trap is described for field use.

Male-produced pheromone of Spathius agrili, a parasitoid introduced for the biological control of the invasive emerald ash borer, Agrilus planipennis.

The braconid wasp, Spathius agrili, has been released in the U.S. as a biocontrol agent for the invasive emerald ash borer (Coleoptera: Buprestidae: Agrilus planipennis), a destructive pest of ash trees (Fraxinus spp.). We identified and synthesized seven male-specific volatile compounds. Three of these, dodecanal, (4R,11E)-tetradecen-4-olide, and (Z)-10-heptadecen-2-one, were the key behaviorally active components in flight tunnel bioassays. Male specificity was demonstrated by gas chromatographic comparison of male and female volatile emissions and whole body extracts. Identifications were aided by coupled gas chromatographic-mass spectrometric (GC-MS) analysis, microchemical reactions, NMR, chiral GC analysis, and GC and MS comparison with authentic standards. Both the racemic and chiral forms of the γ-lactone, as well as both E- and Z-isomers were synthesized. Flight tunnel behavioral tests showed positive male and female S. agrili responses to both natural pheromone and synthetic blends, with upwind flight and landing on the source. Large field-cage tests, using yellow sticky traps baited with pheromone, captured approximately 50xa0% of the released male and female wasps in 24-h periods. The use of pheromone-baited traps in the field could simplify the current detection method for determining parasitoid establishment (i.e., laboriously felling and peeling ash trees for recovery of S. agrili from infested EAB larvae).

Similarities in pheromonal communication of flea beetles Phyllotreta cruciferae Goeze and Ph. vittula Redtenbacher (Coleoptera, Chrysomelidae)

Remarkable similarities have been found in the pheromonal communication of Phyllotreta vittula Redtenbacher and of Ph. cruciferae Goeze (European population) (Coleoptera, Chrysomelidae). In previously published European field tests with Ph. cruciferae, only the major male‐produced sesquiterpene identified from North American Ph. cruciferae [compound A, (6R,7S)‐2,2,6,10‐tetramethylbicyclo[5.4.0]undeca‐1(11),9‐diene] was behaviourally active; unexpectedly, the European species Ph. vittula also responded in these tests and in the same way. In the present study, both the European population of Ph. cruciferae and Ph. vittula were shown to produce the same blend of compounds found in North American Ph. cruciferae and in similar proportions. Compound A is concluded to be a pheromone component for Ph. vittula as well as for Ph. cruciferae. In previously published tests with host compounds, Ph. vittula preferred 3‐butenyl isothiocyanate to allyl isothiocyante whereas the reverse was true for Ph. cruciferae. It was also learned earlier that compound A enhanced the response of both species toward allyl isothiocyanate. The present study further explored interactions between compound A and the two isothiocyanates. Thus, the highest catches of Ph. vittula were recorded in traps with the combination of racemic compound A with 3‐butenyl isothiocyanate, while highest Ph. cruciferae catches (and of Ph. nigripes Fabr.) were observed in traps with the combination of compound A with allyl isothiocyanate. Therefore, with the optimal combination of pheromonal and host‐derived stimuli, more specific communication channels may exist for the different Phyllotreta spp. Both Ph. cruciferae and Ph. vittula rank among the most important pest flea beetles in Europe.

Volatile emissions from the flea beetle Altica litigata (Coleoptera: Chrysomelidae) associated with invasive Ludwigia hexapetala.

The flea beetle Altica litigata (Chrysomelidae) is an insect herbivore to plants within the families Lythraceae and Onagraceae, including ornamentals such as crape myrtle, Lagerstroemia spp. This insect is important both as a pest species and as a naturally occurring biological control agent due to its aggregate feeding behavior, which typically results in severe defoliation of the host plant. Despite the negative economic impact to ornamentals and contrary benefits as a biological control agent, there are few reports on the semiochemical communication of this family of insects. Uruguayan primrose-willow (Ludwigia hexapetala) is an invasive aquatic weed in California and serves as a host to A. litigata. To better characterize this association, the volatile emissions of A. litigata were collected while the flea beetles were: in containers by themselves, in containers with L. hexapetala leaves, in situ on L. hexapetala leaves in a growth chamber, and in situ on L. hexapetala leaves in the field. For comparison, the volatile emissions of A. litigata associated with two subspecies of creeping water primrose (L. peploides) were also evaluated. Two himachalene-type sesquiterpenes, showing the same carbon skeleton as compounds previously reported from Aphthona flava and Epitrix fuscula, were detected as volatiles from A. litigata.

Landing Surface Color Preferences of Spathius agrili (Hymenoptera: Braconidae), a Parasitoid of Emerald Ash Borer, Agrilus planipennis (Coleoptera: Buprestidae)

The color preferences for landing surfaces were examined for Spathius agrili (Hymenoptera: Braconidae), a parasitic wasp introduced for biocontrol of emerald ash borer, Agrilus planipennis (Coleoptera: Buprestidae). Lures with the 3-component pheromone blend of male S. agrili were used to activate upwind flight by virgin female S. agrili in a laminar flow wind tunnel. Paper discs with halves of two different colors (combination pairs of black, white, red, yellow, green, or purple), with the pheromone lure in the center, were tested to quantify preferences for landing on one color over another. Females landed preferentially on green, yellow, and white surfaces, and landed the least frequently on red, black, and purple surfaces. Changes in color preferences due to adjacent colors were observed and discussed.

Attraction of Spathius Agrili Yang (Hymenoptera: Eulophidae) to Male-Produced “Aggregation-sex Pheromone”: Differences Between the Sexes and Mating Status

Male and female Spathius agrili Yang were tested for attraction to the synthetic male pheromone. Lures consisting of a 3-component pheromone blend were placed in the center of a white filter paper target used to activate upwind flight in the wind tunnel. When virgin males and females were tested for attraction, both sexes were attracted to the lure prior to mating. However, only males were attracted to the pheromone lures after mating. In another experiment, of females that flew to the lure as virgins, half were subsequently mated and the other half were not, and mated females were no longer attracted. Then both mated and virgin females were provided with host material (emerald ash borer larvae in sticks of ash) to determine if oviposition affected attraction. They were supplied with fresh hosts ad libidum and subsequently tested for attraction for 55xa0days, and results showed that oviposition did not affect attraction to the pheromone. The key factor in attraction to the pheromone was mating. Because this pheromone is released by one sex and is attractive to both sexes for the purpose of mating, it qualifies as an “aggregation-sex pheromone”.

Erratum to: Attraction of Spathius Agrili Yang (Hymenoptera: Braconidae) To Male-Produced “Aggregation-Sex Pheromone”: Differences Between the Sexes and Mating Status

The original paper of this article unfortunately contains an error. In spite of thorough proofreading, in the title the family name of Spathius agrili was wrongly listed as Eulophidae and should have been Braconidae.