First record of Pyrrhalta viburni (Coleoptera: chrysomelidae) in Bosnia and Herzegovina

Pyrrhalta viburni (Coleoptera: Chrysomelidae), is a chrysomelid native to Eurasia. It gained importance as an invasive species in North America due to its ability to cause serious damage to native and ornamental Viburnum spp. plants. In our study Pyrrhalta viburni was recorded as a new record in the fauna of Bosnia and Herzegovina. It has been recorded on four locations in Bosnia and Herzegovina in the region of Sarajevo. As it is feeding on Viburnum spp. that are commonly used as ornamental plants, its monitoring in urban and other habitats is suggested.

First Insights into the Chemical Ecology of an Invasive Pest: Olfactory Preferences of the Viburnum Leaf Beetle (Coleoptera: Chrysomelidae)

The viburnum leaf beetle (VLB), Pyrrhalta viburni (Paykull), is an invasive chrysomelid in North America where it infests native Viburnum shrubs in woody areas and managed landscapes. Despite its invasive and destructive nature, little is known about the chemical ecology of this beetle, and efficient chemical lures for monitoring and trapping this insect have yet to be developed. Using two of the main host plants of VLB in its native range, Viburnum opulus L. (Caprifoliaceae) and V. lantana L., we examined the olfactory preferences of adult females of VLB under laboratory conditions and measured volatile emissions of Viburnum twigs with and without VLB damage. VLB females had a clear preference for V. opulus and V. lantana twigs compared to blank odor sources. In addition, twigs with foliar damage and fresh egg masses were found to be more attractive than noninfested twigs in V. opulus when VLB infestation was recent, but not when twigs had been infested for several weeks. Chemical analyses revealed consistent treatment-specific blends of compounds, which may be used for the elaboration of attractive lures. Future research should focus on the identification of these compounds and on exploring the olfactory preferences of VLB with Viburnum species present in North America.

Mites associated with egg masses of the viburnum leaf beetle Pyrrhalta viburni (Paykull) on Viburnum tinus L.

The viburnum leaf beetle Pyrrhalta viburni (Coleoptera: Chrysomelidae) is a specialist Viburnum leaf-feeder that is native to Eurasia and invasive in North America. Eggs of P. viburni are laid in round cavities excavated by the ovipositing female beetle and covered with a protective secretion. We document in this paper the mite fauna associated with P. viburni egg masses on Viburnum tinus in southern France. We then report the results of experiments investigating the seasonal patterns of mite infestation and the effects of the most common mite found within egg masses, Trichoribates trimaculatus (Oribatida: Ceratozetidae), on P. viburni egg survivorship. A diverse mite fauna of 18 species was found on V. tinus twigs, often living within P. viburni egg masses, including predaceous, phytophagous, and detritivorous species. Mite abundance and diversity were higher on Viburnum twigs containing at least one intact egg mass and were positively correlated with the number of intact egg masses per twig. Detritivorous mites were more abundant on twigs nine months after oviposition than one and four months after oviposition. Finally, we found no evidence that T. trimaculatus impacts P. viburni egg survivorship and overwintering success. These findings show that P. viburni egg masses and their associated cavities form a microhabitat favorable for the establishment of several mite species. It seems likely that these associations are cases of commensalism where mites benefit from the presence of food and shelter in these protected cavities, with no direct negative impact on P. viburni eggs.

Oviposition strategy as a means of local adaptation to plant defence in native and invasive populations of the viburnum leaf beetle

Herbivores have been hypothesized to adapt locally to variation in plant defences and such adaptation could facilitate novel associations in the context of biological invasions. Here, we show that in the native range of the viburnum leaf beetle (VLB, Pyrrhalta viburni ), two populations of geographically isolated hosts— Viburnum opulus and Viburnum tinus —have divergent defences against VLB oviposition: negative versus positive density-dependent egg-crushing wound responses, respectively. Populations of beetles coexisting with each host show an adaptive behavioural response: aggregative versus non-aggregative oviposition on V. opulus and V. tinus , respectively. In parallel, we show that in North America, where VLB is invasive, defences of three novel hosts are negatively density-dependent, and beetles' oviposition behaviour is aggregative. Thus, local adaptation to plant defences has the potential to facilitate the invasion of herbivores onto novel hosts.