Odors Attracting the Long-Legged Predator Medetera signaticornis Loew to Ips typographus L. Infested Norway Spruce Trees

Abstract

Predatory long-legged flies of the genus Medetera are important, but currently understudied, natural enemies of Scolytinae bark beetles such as Ips typographus. Medetera flies lay eggs on beetle-infested trees, where the developing larvae find their prey, but the chemical cues used by Medetera to locate infested trees are currently unknown. To identify odors attracting Medetera signaticornis, a species in Europe, headspace samples were collected at several time-points through different stages of I. typographus attacks on logs of Norway spruce (Picea abies). The headspace samples were analyzed using combined gas chromatography and mass spectrometry (GC–MS), and gas chromatography coupled with electroantennographic detection (GC-EAD) to determine compounds that stimulate M. signaticornis antennae. Antennae of M. signaticornis males and females were found to detect (–)-cis-verbenol, ( +)-trans-verbenol and myrtenol, which are known to be produced by bark beetles. Antennal responses were also observed for verbenene, isoterpinolene, α-pinene oxide, camphor, pinocamphone, terpinene-4-ol, myrtenal, borneol, α-terpineol, geranyl acetone, and verbenone, which are primarily produced by microorganisms, and α-pinene, α-fenchene, β-pinene, camphene, 3-carene, limonene, γ-terpinene, and terpinolene, known spruce tree compounds. In field experiments testing two synthetic blends containing 18 antennal active and two additional compounds 2-methyl-3-buten-2-ol and ipsdienol we observed significant attraction of M. signaticornis within 24 h. These attractive blends can form the basis for development of Medetera monitoring lures for use in future forest and pest management.

Odours attracting Medetera (Diptera) predators to spruce bark beetles in a multitrophic system

“…aggregation pheromone) are produced by bark beetles living under the bark, and by bark beetle symbiotic microorganisms that have been introduced into the tree phloem during beetle colonisation (Birgersson et al, 1984;Kandasamy et al, 2023; Paper III/Sousa et al 2023b) (Figure 3). In agreement with other studies, the qualitative and quantitative composition of these odours also varied throughout the different stages of I. typographus attacks (Birgersson et al, 1984;) (Paper III/ Sousa et al 2023b).…”

“…The compounds released by the host tree and bark beetles are released in greater amounts during the early stages of a bark beetle attack, while the oxygenated monoterpenes (i.e. camphor, pinocamphone) primarily produced by bark beetle symbiotic microorganisms are released in higher amounts during late stages of the attack ; Paper III/ Sousa et al, 2023b). Predatory Medetera species have been observed to arrive at freshly attacked trees almost simultaneously with bark beetles, possibly being attracted by the bark beetle aggregation pheromone.…”

Pilot Study of 3D Spatial Distribution of α-Pinene Emitted by Norway Spruce (L.) Karst Recently Infested by Ips typographus (L. 1758) (Coleoptera: Scolytinae)

“…The volatile compounds emitted by infested trees have been studied in two main contexts: atmospheric chemistry processes, with a focus on reactive particle formation [50], and ecological roles related to bark beetles and their predators [27,28,32,51]. Most reports in atmospheric chemistry measured volatiles at the canopy or twig level [52].…”

Development of Menthyl Esters of Valine for Pest Control in Tomato and Lettuce Crops

“…A variety of volatile organic compounds (VOCs), including monoterpenoids, play critical roles in plant defense responses. For example, monoterpenoids are highly effective insecticides [1,2], while also attracting species-specific herbivore predators (known as indirect plant defense) [3][4][5][6] and pollinators [7,8], and conferring tolerance to oxidative and thermal stress on plants [9,10]. Especially in response to herbivores, plants emit VOCs not only to attract herbivore predators but also to communicate with neighboring plants (a phenomenon referred to as "talking plants" or "VOC eavesdropping").…”