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Clear‐fell harvesting of non‐native plantation forests in the southern hemisphere creates large amounts of woody debris that is used for breeding by non‐native bark beetles and wood borers. Limited competition and a shortage of natural enemies allow some invasive pine bark beetles and wood borers to become highly abundant and cause phytosanitary issues. Replicated transects (550–750 m long) of funnel traps baited with alpha‐pinene and ethanol spanning even‐aged Pinus radiata stands were established in New Zealand's largest plantation forest and monitored from pre‐harvest until up to 5 years post‐harvesting to test the effects of harvesting residue resource pulses on the spatio‐temporal population dynamics of Hylurgus ligniperda, Hylastes ater and Arhopalus ferus. Generalised additive mixed model analyses of trap captures of >687,000 H. ligniperda, >7600 H. ater and >5000 A. ferus individuals showed greatly elevated populations for the first 2–3 years post‐harvest. Subsequently, populations returned to very low levels once the resource pulse was exhausted. Spatial patterns of captures reflecting beetle dispersal from breeding material showed a curvilinear decline along the breeding resource gradient by up to 95% from the interior of a recently harvested stand into an adjacent, previously harvested stand with exploited resources. Synthesis and applications. The results show that forest management characterised by ongoing harvesting of neighbouring stands facilitates the build‐up of large populations of bark beetles and wood borers of phytosanitary concern. This is due to recurrent resource pulses caused by the supply of substantial amounts of breeding material from tree felling. Our findings can inform forest planning aimed at avoiding such harvesting patterns, by assisting with the development and implementation of strategies for the management of beetle populations across the landscape. Most beetles dispersed <400 m beyond the source stand edge, although some beetles are likely to have dispersed further. Keeping a distance of 1–2 km between recently felled stands and those scheduled for felling would be expected to reduce rapid population growth. This knowledge can also be used to reduce seedling attack, minimise infestation of logs, and ultimately, mitigate pathway and biosecurity risks, with important implications for forest product exports and quarantine measures. [ABSTRACT FROM AUTHOR]

In 2023, the invasive black twig borer Xylosandrus compactus (Eichhoff, 1875) (Coleoptera: Scolytinae) was found for the first time in Switzerland. Outbreaks of this non-native species have been recorded during phytosanitary survey activities in four municipalities south of the Alps in the Canton of Ticino. Conducting genetic analyses using the mitochondrial COI barcode region, specimens found in Switzerland were identical with those from France, Italy, and Spain, suggesting a European source of invasion. So far, only ornamental plants in urban areas were found to be affected by attacks of X. compactus. However, because of the increasing proportion of broadleaved evergreen plant species, the availability of suitable host plants such as Laurus nobilis may also favour the spread of X. compactus into insubric forest systems. Three previously undescribed host plant species, Argyrocytisus battandieri, Mahonia aquifolium, and Wisteria sp., were identified. In addition, fungal isolations from adult beetles and breeding galleries revealed eight fungal species likely or potentially associated with X. compactus. These include Ambrosiella xylebori (Ascomycota: Ceratocystidaceae), the obligate ambrosia fungus of X. compactus, and a Thyridium species (Ascomycota: Thyridiaceae) that has been found as an associated fungus in previous studies. [ABSTRACT FROM AUTHOR]

During the last two decades there has been growing recognition of the importance of Allee effects in population dynamics and applied ecology. The Allee effect, that is decreased fitness at lower population densities, has been recognized as potentially playing an important role in the conservation of endangered species, in the practice of biological control, and the eradication of invasive species. Although a number of theoretical studies have been devoted to the role of Allee effects in the population dynamics of insects and other terrestrial arthropods, experimental evidence documenting Allee effects is still scarce. Here, we reviewed the literature reporting on density-dependent relationships in low-density populations and conducted a meta-analysis of 191 case studies to identify the occurrence of Allee effects and associated species traits. Allee effects are not rare in terrestrial arthropods, as they were reported in 47% of the cases we reviewed, comprising 46 out of 68 species. Ample examples exist for both demographic Allee effects (28 out of 74 cases cases), and component Allee effects (61 out of 117 cases). Insufficient mating success, cooperative feeding, and enemy escape were the three main mechanisms associated with Allee effects in terrestrial arthropods. Insufficient reproductive success was the mechanism with the highest proportion of related Allee effects (71%). Voltinism and host specialization were common species traits behind demographic Allee effects. Host specialists with univoltine life cycles tended to have stronger Allee effects. The high frequency of Allee effects in terrestrial arthropods reported here and the identified mechanisms behind them have important implications for the selection of management strategies. [ABSTRACT FROM AUTHOR]