Tomato-aphid-hoverfly: A tritrophic interaction incompatible for pest management

in Arthropod-Plant Interactions (2009), 3

Trichome-based tomato resistance offers the potential to reduce pesticide use, but its compatibility with biological control remains poorly understood. We evaluated Episyrphus balteatus De Geer (Diptera ... [more ▼]

Trichome-based tomato resistance offers the potential to reduce pesticide use, but its compatibility with biological control remains poorly understood. We evaluated Episyrphus balteatus De Geer (Diptera, Syrphidae), an efficient aphidophagous predator, as a potential biological control agent of Myzus persicae Sulzer (Hemiptera, Aphididae) on trichome-bearing tomato cultivars. Episyrphus balteatus’ foraging and oviposition behavior, as well as larval mobility and aphid accessibility, were compared between two tomato cultivars (Lycopersicon esculentum Mill. ‘Moneymaker’ and ‘Roma’) and two other crop plants; broad bean (Vicia faba L.) and potato (Solanum tuberosum L.). Hoverfly adults landed and laid more eggs on broad beans than on three species of Solanaceae. Hoverfly larval movement was drastically reduced on tomato, and a high proportion of hoverfly larvae fell from the plant before reaching aphid prey. After quantifying trichome abundance on each of these four plants, we suggest that proprieties of the plant surface, specifically trichomes, are a key factor contributing to reduced efficacy of E. balteatus as a biological agent for aphid control on tomatoes. [less ▲]

Does Imidacloprid Seed-Treated Maize Have an Impact on Honey Bee Mortality?

in Journal of Economic Entomology (2009), 102(2), 616-623

Beekeepers suspected maize. Zea mays L., treated with imidacloprid to result in substantial loss of honey bee (Hymenoptera: Apidae) colonies in Belgium. The objective of this study was to investigate the ... [more ▼]

Beekeepers suspected maize. Zea mays L., treated with imidacloprid to result in substantial loss of honey bee (Hymenoptera: Apidae) colonies in Belgium. The objective of this study was to investigate the potential impact of maize grown from imidacloprid-treated seeds on honey bee mortality. A survey of 16 apiaries was carried out, and all maize fields treated or not with imidacloprid were located within a radius of 3,000 m around the observed apiaries. Samples of honey, beeswax, and bees were collected in three colonies per apiary and analyzed for pesticide contain by liquid chromatography-tandem mass spectrometry and gas chromatography-tandem mass spectrometry. We first found significant correlation between the number of colonies per apiary and the mortality rates in an apiary. In addition, this mortality rate was inversely correlated with the surface of maize fields treated and not with imidacloprid, suggesting that this pesticide do not interact with bees fitness. Moreover, a very large number of our samples contained acarcides either prohibited or ineffective against varroa destructor (Anderson & Trueman) (Acari: Varroidae), suggesting that the treatment method used by the beekeepers to be inadequate for mite control. Our results support the hypothesis that imidacloprid seed-treated maize has no negative impact on honey bees. [less ▲]

Mutualisme pucerons-fourmis : étude des bénéfices retirés par les colonies d’Aphis fabae en milieu extérieur

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment [=BASE] (2009), 13

La relation de coopération entre pucerons-fourmis est un bel exemple de mutualisme dans le règne animal, les premiers cherchant protection et hygiène, les seconds une source de sucres nécessaires à la ... [more ▼]

La relation de coopération entre pucerons-fourmis est un bel exemple de mutualisme dans le règne animal, les premiers cherchant protection et hygiène, les seconds une source de sucres nécessaires à la survie de la colonie. La présente étude s’est intéressée à recenser les bénéfices retirés par Aphis fabae Scopoli (Homoptera, Aphididae) de ses relations de mutualisme avec Lasius niger L. (Hymenoptera : Formicidae). Plusieurs paramètres ont été observés en milieu extérieur sur des plants de fèves des marais infestés initialement par 100 individus en présence ou non d’une colonie de L. niger. En présence de fourmis, les plantes étaient constamment infestées par un nombre de pucerons plus important, et la proportion d’individus ailés y était également similaire ou plus grande, selon la date d’observation. Un nombre moins important de prédateurs aphidiphages sur les plantes en présence de fourmis a permis d’expliquer en partie ces observations. Les nombres moyens de pucerons parasités ne différaient pas que les plantes soient explorées ou non par les fourmis suggérant que L. niger est peu efficace face aux attaques de parasitoïdes. Par contre, très peu de pucerons appartenant à des espèces différentes d’A. fabae ont été observés sur les plants mis en présence des fourmis. Ces observations suggèrent que L. niger adopte un comportement de prédation sur les pucerons avec lesquels elle n’entretient aucune relation mutualiste. Les observations menées n’ont pas permis de mettre en évidence un quelconque effet des fourmis sur la vigueur des plantes hôtes des pucerons, bien que sensiblement moins d’exuvies et de tâches de miellat étaient présentes sur les plantes dont les colonies de pucerons étaient visitées par L. niger. L’ensemble de ces résultats confirme que L. niger améliore les conditions de vie des colonies de pucerons d’Aphis fabae dont elle exploite le miellat, principalement grâce à la protection qu’elle apporte contre les prédateurs et la réduction de la pression de compétition exercée par les autres espèces non myrmécophiles de pucerons. [less ▲]

Social enviroment influences aphid production of alarm pheromone

in Behavioral Ecology (2009), 20(2), 283-288

In most aphid species, the volatile sesquiterpene (E)-beta-farnesene (E beta f) is released as an alarm pheromone in response to predation and is also emitted continuously at low levels. Some aphid ... [more ▼]

In most aphid species, the volatile sesquiterpene (E)-beta-farnesene (E beta f) is released as an alarm pheromone in response to predation and is also emitted continuously at low levels. Some aphid predators use E beta f as a foraging cue, suggesting that the benefits to aphids of signaling via E beta f must be weighed against the cost of increasing apparency to natural enemies. To determine whether aphids vary E beta f production in response to features of their social environment, we compared the production of E beta f by Acyrthosiphon pisum (Harris) individuals reared in isolation with that of individuals reared among conspecifics or individuals of a different aphid species, Myzus persicae. Production of E beta f by A. pisum reared in isolation was significantly lower than that of aphids reared among conspecifics or among M. persicae individuals. When we reared A. pisum individuals in isolation but exposed them to odors from an aphid colony, E beta f production was similar to that of aphids reared among conspecifics, suggesting that aphids use a volatile cue to assess their social environment and regulate their production of alarm pheromone. It is likely that this cue is E beta f itself, the only volatile compound previously found in headspace collections of A. pisum colonies. Finally, we examined the attraction of a predatory hoverfly, which uses E beta f as a foraging cue, to groups of aphids reared in isolation or among conspecifics and found that groups comprising individuals reared in isolation were significantly less attractive to the predator, suggesting that the observed variation in E beta f production may be ecologically relevant. [less ▲]

Production of alarm pheromone in aphids and perception by ants and natural enemies

Doctoral thesis (2008)

Most Aphidinae species produce and use (E)-ß-farnesene (Eßf) as an alarm pheromone. This sesquiterpene is released by individuals under attack by a predator, and nearby aphids exhibit a variety of alarm ... [more ▼]

Most Aphidinae species produce and use (E)-ß-farnesene (Eßf) as an alarm pheromone. This sesquiterpene is released by individuals under attack by a predator, and nearby aphids exhibit a variety of alarm behaviours. This PhD thesis aims to better understand how aphids manage their production and emission of alarm pheromone (Chapter IV). We also wanted, in a second step, to improve our knowledge on the roles that Eßf could play in the relationships that aphids have with their predators (Chapter V) and tending ants (Chapter VI), in order to better pinpoint the problem in this very tough context. The aphid predators have indeed a real advantage to be able to use the odorant cues emitted by their prey, to locate them and to select an adequate oviposition site. Ants establish with certain aphid species mutualistic relationships, which occurrence could be facilitated by the use of aphids’ odours. In Chapter IV, we have highlighted that aphid colonies non subjected to attack by predators release constantly small quantities of Eßf in their headspace, which means that this molecule could have additional roles than just acting as an alarm pheromone. In a second study, we demonstrated that the release of Eßf was not contagious, and therefore that a non stressed aphid receiving the alarm signal does not release additional Eßf. Since the production of alarm pheromone is likely to entail physiological cost, we tested and validated the hypothesis that aphids regulate their Eßf production according to their social environment. In Chapter V, we studied the ability of the hoverfly predator Episyrphus balteatus (Diptera, Syrphidae) to be used as biological control agent against aphids infesting tomato plants (Lycopersicon esculentum). After identifying the odours emitted by aphid infested plants, we have demonstrated that although this Diptera is able to perceive all the odours released by the system, it mainly uses Eßf to select its oviposition site. However, the E. balteatus larvae are not adapted to the architecture of tomato plants. We also showed that the Asian ladybeetle Harmonia axyridis (Coleoptera, Coccinellidae) olfaction was adapted to the perception of Eßf and that this beetle is also attracted by this sesquiterpene. Finally, in Chapter VI, we characterized the benefits accruing to aphid populations that have established mutualistic relationships with Lasius niger (Hymenoptera, Formicidae), and have demonstrated the role of Eßf and honeydew, respectively in locating aphid colonies and in the persistence of the mutualism. [less ▲]

Fast purification and characterisation of semiochemical compounds from essential oil of Matricaria chamomilla L. and Nepeta cataria L. using column chromatography fractionation and ultra fast GC analysis

Poster (2008, May 28)

what smell decaying pig carcasses

(2008, May)

La coccinelle à deux points (Adalia bipunctata), le chrysope commun (Chrysoperla carnea) et le syrphe ceinturé (Episyrphus balteatus), nos principaux prédateurs indigènes plutôt que la coccinelle asiatique (Harmonia axyridis) exotique et invasive dans nos écosystèmes

in L'Erable du CNB (2008)

Production of alarm pheromone by developing aphids varies in response to their social environment

Conference (2008)

Aphid alarm pheromone—the volatile sesquiterpene (E)-β-farnesene (Eβf) in most species—is released in response to predation and other stresses and typically causes nearby aphids who receive the signal to ... [more ▼]

Aphid alarm pheromone—the volatile sesquiterpene (E)-β-farnesene (Eβf) in most species—is released in response to predation and other stresses and typically causes nearby aphids who receive the signal to cease feeding, drop from their host plant, and disperse. Because aphid alarm pheromone confers apparent fitness benefits on recipients while its production and release likely entail costs for the emitting aphid, it could be adaptive for aphids to regulate their Eβf production in response to variation in the social environment. To explore this possibility we compared the production of Eβf by Acyrthosiphon pisum (Harris) individuals reared from first-instar larvae to the adult stage in isolation to that of individuals reared among conspecifics or among individuals of a different aphid species, Myzus persicae (Sulzer). Levels of EβF produced in each treatment were assayed by GC-FID quantification of EβF in volatiles collected from crushed aphids. Production of EβF by A. pisum reared in isolation (14.4ng/aphid) was significantly lower than that of aphids reared in a colony of conspecifics (49.1ng/aphid), reared in a M. persicae colony (31.5ng/aphid) or reared among conspecifics of another aaphid clone (52.7ng/aphid). Though A. pisum individuals in our experiments produced less EβF when reared among M. persicae than among conspecifics, this difference was not statistically significant. In a separate experiment we reared A. pisum individuals in isolation and exposed them to the odor of conspecifics. Under these conditions, EβF production was similar to that of aphids reared among conspecifics, suggesting that aphids use volatile cues to assess their social environment and regulate their production of alarm pheromone accordingly. [less ▲]

Emission of alarm pheromone by non-preyed aphid colonies

in Journal of Applied Entomology (2008), 132(8), 601-604

The sesquiterpene (E)-beta-farnesene (E beta f) is the primary component of the alarm pheromone of most aphid species. It is released in response to physical stress including attack by natural enemies and ... [more ▼]

The sesquiterpene (E)-beta-farnesene (E beta f) is the primary component of the alarm pheromone of most aphid species. It is released in response to physical stress including attack by natural enemies and causes aphids to cease feeding and disperse. E beta f also acts as a kairomonal cue for aphid natural enemies. In this study, we collected the headspace volatiles released by aphid colonies of different sizes. Gas chromatography-mass spectrometry analysis demonstrated the presence of E beta f in the absence of predator attack. A quadratic relationship was found between the released (E)-beta-farnesene amounts and aphid colony size. Behavioural impact of aphid alarm pheromone towards Episyrphus balteatus female oviposition behaviour was also demonstrated in this work. These results highlight the primary role of the small but continuous release of aphid alarm pheromone in mechanisms of decision-making by aphid predators during their foraging and egg-laying behaviour. [less ▲]