During the host location process, egg parasitoids rely on a series of chemical stimuli from the host/plant complex. In particular, in tritrophic systems consisting of plants, herbivorous stink bugs and their egg parasitoids, previous studies demonstrated that wasps are attracted by oviposition-induced plant volatiles (OIPVs). These compounds act as indirect plant defence mechanism allowing plants to recruit egg parasitoids, which are in general the most important natural enemies of stink bugs. Moreover, when wasps land on a plant, they can exploit chemical footprints left by male and female stink bugs walking on the leaves as indirect host-related cues, since chemicals lead them in an area where newly laid host eggs are likely to be found. Finally, since host female chemical footprints are the most promising signals of host eggs, wasps evolved the ability to distinguish between footprints left by females and males of their associated hosts. These foraging behaviours are adopted by egg parasitoids searching for native and associated hosts, but invasive insect herbivores can interfere with local multitrophic interactions by affecting the chemical cues emitted by plants and disrupting the attraction of egg parasitoids. In this thesis the potential impact of the brown marmorated stink bug, Halyomorpha halys (Stål) (Heteroptera: Pentatomidae) on local infochemical networks at long and short range was evaluated. Halyomorpha halys is a species native to Asia, which was recently introduced in the Europe and North America, and to evaluate the effect of its establishment, laboratory experiments were conducted using two local tritriphoc systems, in Europe, the one consisting of Vicia faba L. - Nezara viridula (L.) (Heteroptera: Pentatomidae) - Trissolcus basalis (Wollaston) (Hymenoptera: Scelionidae), and in North America, the one consisting of V. faba - Podisus maculiventris (Say) (Heteroptera: Pentatomidae) - Telenomus podisi (Ashmead) (Hymenoptera: Scelionidae). The results showed that both egg parasitoid species, T. basalis and T. podisi, were attracted by the OIPVs of their associated hosts, N. viridula and P. maculiventris, respectively, but not by the OIPVs of non-associated host H. halys. However, in both systems, the parasitoid attraction toward OIPVs emitted following the attack of the associated host was disrupted when host and non-associated host were concurrently present on the same plant. Concerning the substrate-born cues, T. basalis females (naïve or rewarded by an oviposition experience) ability to discriminate between female and male of H. halys were tested. Naïve T. basalis wasps did not discriminate between areas contaminated by chemical footprints left by the non-associated host female or male on the contrary experienced female of T. basalis, re-encountering after 1 hour, discriminated between male and female chemical footprints but they were not able to discriminate H. halys gender after 24 hours. This indicates that invasion by an alien herbivore can interfere with local established semiochemical webs. Overall the outcomes are discussed by evaluating the possible consequences of alien insect spread on local parasitoid foraging behaviour.
Martorana, L.Impact of an invasive pest in local semiochemical networks.
|Titolo:||Impact of an invasive pest in local semiochemical networks|
|Citazione:||Martorana, L.Impact of an invasive pest in local semiochemical networks.|
|Appare nelle tipologie:||4.2 Tesi di dottorato|