Olfactory cues in the host-location of the cosmopolitan ecto-parasitoid Pyemotes tritici (Acarina: Pyemotidae)

Abstract

Chemical ecology regarding the ectoparasitoid mite of the family Pyemotidae remains largely underexplored. This field warrants further attention, to enhance the effectiveness of pyemotid mite species as biological control agents against xylophagous insects and stored-product pests, and to clarify the role of these mites in the onset of itchy dermatitis in humans. This is the first investigation regarding the host-location process of Pyemotes tritici (LaGrèze-Fossat and Montane, 1851), an ectoparasitoid that attacks a wide range of hosts, including xylophagous insects and stored product pests. Bioassays in still air olfactometer and open arena have been performed. Females of P. tritici, consistent with the typical behavior of generalist parasitoids, demonstrated the ability to detect and respond to various volatile chemicals emitted from the host habitat (seasoned wood sawdust from pine and beech) and host frass of two longhorn beetles, Hylotrupes bajulus (L.) and Trichoferus holosericeus (Rossi), as well as from feces and silk of the rice moth Corcyra cephalonica (Stainton), while they did not respond to volatiles emitted from the larvae of the same species. Additionally, they detected non-volatile chemicals from the cuticle of T. holosericeus. These results highlight the importance of chemical cues, both direct and indirect, from the host in the host-location process of P. tritici. Moreover, we provided a useful protocol for safely rearing these potentially harmful mites. Chemical analysis of host and habitat VOCs and host larval CHCs involved in the host location process for identification of active compounds will complete the behavioural results here presented.