Que faire lors d'invasions de coccinelles asiatiques ?

in Canard Déchaîné du Kauwberg (Le) (2008), 66

Aphids adapt their alarm pheromone production according to their social environment

Poster (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 ▲]

What makes Episyrphus balteatus (Diptera: Syrphidae) oviposit on aphid infested tomato plants?

in Communications in Agricultural and Applied Biological Sciences (2008), 73(3), 371-81

Under attack by insect pests, many plant species change their volatile chemical emissions to attract natural enemies. Most of the tomato (Lycopersicon sp., Solanaceae) varieties are subjected to ... [more ▼]

Under attack by insect pests, many plant species change their volatile chemical emissions to attract natural enemies. Most of the tomato (Lycopersicon sp., Solanaceae) varieties are subjected to infestation by molluscs and insects, including the generalist aphid Myzus persicae Sulzer (Homoptera, Aphididae). Episyrphus balteatus De Geer (Diptera: Syrphidae) is a generalist aphid predator that was here observed to lay eggs on M. persicae infested tomato but not on non-infested plants. In order to identify the volatile chemicals that guide the foraging and oviposition behaviour of E. balteatus, we collected and identified volatiles released in the headspace of both aphid infested and uninfested tomato plants by SPME-GC-MS. The identified chemicals were subsequently tested by electroantennography (EAG) on E. balteatus. Monoterpenes and sesquiterpenes were identified, the main volatile chemicals being beta-phellandrene, 2-carene, alpha-phellandrene, 3-carene and o-pinene. Electrical depolarizations were observed for each tested monoterpene, with optimal responses ranging from -0.2 to -0.8 mV. Episyrphus balteatus antennae showed dose-response relationships towards all the active chemicals. (E)-beta-farnesene, the main component of the aphid alarm pheromone, was the only active sesquiterpene, and is presumed to act as an oviposition stimulus for E. balteotus. [less ▲]

Emission of alarm pheromone in aphids: A non-contagious phenomenon

in Journal of Chemical Ecology (2008), 34(9), 1146-1148

In response to attack by natural enemies, most aphid species release an alarm pheromone that causes nearby conspecifics to cease feeding and disperse. The primary component of the alarm pheromone of most ... [more ▼]

In response to attack by natural enemies, most aphid species release an alarm pheromone that causes nearby conspecifics to cease feeding and disperse. The primary component of the alarm pheromone of most species studied is (E)-beta-farnesene. We recently demonstrated that the production and accumulation of (E)-beta-farnesene during development by juvenile aphids is stimulated by exposure to odor cues, most likely by (E)-beta-farnesene emitted by other colony members. Here, we tested whether the release of (E)-beta-farnesene can be triggered by exposure to the alarm pheromone of other individuals, thereby amplifying the signal. Such contagious emission might be adaptive under some conditions because the amount of (E)-beta-farnesene released by a single aphid may not be sufficient to alert an appropriate number of individuals of the colony to the presence of a potential threat. By using a push-pull headspace collection system, we quantified (E)-beta-farnesene released from Acyrthosiphon pisum aphids exposed to conspecific alarm signals. Typical avoidance behavior was observed following exposure to (E)-beta-farnesene (i.e., aphids ceased feeding and dropped from host-plant); however, no increase in alarm pheromone amount was detected, suggesting that contagious release of (E)-beta-farnesene does not occur. [less ▲]

Aphid and plant volatiles induce oviposition in an aphidophagous hoverfly

in Journal of Chemical Ecology (2008), 34(3), 301-307

Episyrphus balteatus DeGeer (Diptera, Syrphidae) is an abundant and efficient aphid-specific predator. We tested the electroantennographic (EAG) response of this syrphid fly to the common aphid alarm ... [more ▼]

Episyrphus balteatus DeGeer (Diptera, Syrphidae) is an abundant and efficient aphid-specific predator. We tested the electroantennographic (EAG) response of this syrphid fly to the common aphid alarm pheromone, (E)-beta-farnesene (E beta F), and to several plant volatiles, including terpenoids (mono- and sesquiterpenes) and green leaf volatiles (C6 and C9 alcohols and aldehydes). Monoterpenes evoked significant EAG responses, whereas sesquiterpenes were inactive, except for the aphid alarm pheromone (E beta F). The most pronounced antennal responses were elicited by six and nine carbon green leaf alcohols and aldehydes [i.e., (Z)-3-hexenol, (E)-2-hexenol, (E)-2-hexenal, and hexanal]. To investigate the behavioral activity of some of these EAG-active compounds, E. balteatus females were exposed to R-(+)-limonene (monoterpene), (Z)-3-hexenol (green leaf alcohol), and E beta F (sesquiterpene, common aphid alarm pheromone). A single E. balteatus gravid female was exposed for 10 min to an aphid-free Vicia faba plant that was co-located with a semiochemical dispenser. Without additional semiochemical, hoverfly females were not attracted to this plant, and no oviposition was observed. The monoterpene R-(+)-limonene did not affect the females' foraging behavior, whereas (Z)-3-hexenol and E beta F increased the time of flight and acceptance of the host plant. Moreover, these two chemicals induced oviposition on aphid-free plants, suggesting that selection of the oviposition site by predatory hoverflies relies on the perception of a volatile blend composed of prey pheromone and typical plant green leaf volatiles. [less ▲]

Chemical ecology in forensic entomology: Investigation of volatile infochemicals from pig cadaver on necrophagous insect behaviour

Poster (2008)

Emission of alarm pheromone in aphids: A contagious phenomenon?

Poster (2008)

Role Of Terpenes From Aphid-Infested Potato On Searching And Oviposition Behavior Of Episyrphus Balteatus

in Insect Science (2007), 14(1),

Emission of alarm pheromone in aphids : a contagious phenomenon ?

Conference (2007)

Aphids adapt their alarm pheromone production to presence or absence of conspecifics

Poster (2007)