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Abstract: We summarize the effects of major weather events such as ice storms, wind storms, and flooding on the abundance and diversity of terrestrial forest insects and their allies. This [...]

1. Host selection and utilization by ambrosia beetles ranges from healthy trees to weakened, dying, or dead trees. Compared to weakened trees, healthy trees emit little to no ethanol, which is stress‐induced and a by‐product of anaerobic respiration. The current study tested the attraction of two invasive ambrosia beetles, Kuroshio shot hole borer (KSHB), one member of the species complex, Euwallacea nr. fornicatus, and fruit‐tree pinhole borer, Xyleborinus saxesenii, to four treatments with or without ethanol. 2. GC–MS analyses confirmed the release of ethanol from the ethanol lure and boxelder log filled with ethanol and not from the other two treatments. Kuroshio shot hole borer was not preferentially attracted to any ethanol treatment, whereas X. saxesenii responded positively to the ethanol treatments. The boxelder bolt infused with ethanol was the most attractive treatment to X. saxesenii. 3. We propose that the differential behavioural responses of these two ambrosia beetles to ethanol correspond to their differential aggressiveness for attacking healthy trees: KSHB attacks healthy trees, whereas X. saxesenii attacks weakened trees. The proposal is further substantiated by a literature survey on bark and ambrosia beetles from Scolytinae. The survey also indicates that the majority of bark and ambrosia beetles from Scolytinae respond positively to ethanol. 4. Although ethanol is widely used and is an effective lure for attraction of many bark and ambrosia beetles, findings from this current study and many others necessitate research and development of alternative lures for more aggressive species which are ecologically and economically more devastating. [ABSTRACT FROM AUTHOR]

The walnut twig beetle, Pityophthorus juglandis Blackman, the vector of thousand cankers disease (TCD), poses a significant threat to North American walnut (Juglandaceae Juglans) trees. Despite discovery of TCD-related tree mortality over a decade ago, management options are lacking. This study represents the culmination of several years of investigating the chemical ecology of P. juglandis in hopes of developing a semiochemical repellent to disrupt the beetle's host colonization and aggregation behaviors. Numbers of P. juglandis landing on semiochemical-treated Juglans regia L. trees in a commercial walnut orchard were compared based on captures on sticky traps. Two repellent combinations were tested: R -(+)-limonene and trans -conophthorin (LimeCon), and R -(+)-limonene, trans -conophthorin, and R -(+)-verbenone (LCV). Both repellents reduced P. juglandis aggregation (captures) equally; thus, we proceeded with the LimeCon combination to reduce potential treatment cost. Subsequent trials included a 2× dose (Dual) of LimeCon. Both LimeCon and Dual significantly reduced the number of P. juglandis caught compared with the baited control, however, only for the lower of two trap positions. Beetle landings were modeled by trap distance from repellent placement on each tree. Beetle responses to the pheromone lure were surprisingly localized and did not bring the whole tree under attack. LimeCon, LCV, and Dual treatments averaged fewer than a single beetle caught for all trap distances; however, performance of the repellents beyond 150 cm is not clear due to the localized landing response of P. juglandis to pheromone lures. Further testing is required to fully analyze the zone of inhibition of the LimeCon repellent. [ABSTRACT FROM AUTHOR]

Host selection behaviour of the walnut twig beetle (WTB) among hardwood trees was investigated in a riparian forest in northern California by monitoring the landing rate of the beetle with sticky traps on branches baited with 3‐methyl‐2‐buten‐1‐ol, the male‐produced aggregation pheromone.The assay was conducted over 7 days (22 May to 29 May 2017) and compared landing rates on branches of six nonhost species paired with northern California black walnut, Juglans hindsii (the host).A total of 2242/1192 WTB were collected on branches of host/nonhost pairs, and more WTB landed on J. hindsii than on nonhosts in 42 of 58 instances. Female landing rate generally exceeded male landing rate, which underscores the influence of the male‐produced synthetic pheromone in this system.Landing rates of WTB males, females, and the combined sexes on boxelder, Acer negundo, and valley oak, Quercus lobata, did not differ significantly from the landing rates on J. hindsii, suggesting that these two nonhost riparian hardwoods do not repel WTB (in the context of the aggregation pheromone).Significantly fewer WTB landed on Oregon ash, Fraxinus latifolia, river red gum, Eucalyptus camaldulensis, Fremont cottonwood, Populus fremontii, and red willow, Salix laevigata, than on J. hindsii, which suggests that these four nonhosts may repel one or both sexes of WTB in the context of the aggregation pheromone. Future analysis of the volatiles from these four hardwood species may lead to the discovery of semiochemical repellents for WTB. [ABSTRACT FROM AUTHOR]

The southern pine beetle, Dendroctonus frontalis Zimmermann (Coleoptera: Curculionidae: Scolytinae), is among the most destructive bark beetle pests of pines (Pinaceae) of the southeast and mid-Atlantic United States of America, Mexico, and Central America. Numerous volatile compounds can stimulate or reduce attraction of the beetle, but efforts to incorporate these into effective, practical technologies for pest management have yielded mixed results. Attractants have been incorporated into lures used in monitoring traps that are employed operationally to forecast outbreaks and detect emerging populations. The attraction inhibitor, verbenone, shows efficacy for suppressing southern pine beetle infestations but has not yet been adopted operationally. No effective semiochemical tree protectant has been developed for the beetle. We discuss complexities in the chemical ecology of the beetle that likely have impeded research and development of semiochemical management tools, and we describe basic science gaps that may hinder further progress if not addressed. We also report some supporting, original experimental data indicating (1) that a verbenone device can inhibit the beetle's response to sources of attractant in a radius of at least several metres, (2) similar olfactory responses by the beetle to both enantiomers of verbenone, and (3) that pheromone background can cause conflicting results in semiochemical field tests. [ABSTRACT FROM AUTHOR]

Although the use of nonhost plants intercropped among host crops has been a standard agricultural practice for reducing insect herbivory for millennia, the use of nonhost signals to deter forest pests is much more recent, having been developed over the past several decades. Early exploratory studies with synthetic nonhost volatile semiochemicals led to targeted electrophysiological and trapping experiments on a variety of bark and ambrosia beetles (Coleoptera: Curculionidae: Scolytinae) across three continents. This work disclosed a suite of antennally and behaviourally active nonhost volatiles, which are detected in common across a range of coniferophagous bark beetles. It also established the fact that dispersing bark and ambrosia beetles detect nonhost signals while in flight and avoid nonhost trees without necessarily landing on them. Later work showed that groups of synthetic nonhost volatiles, sometimes combined with insect-derived antiaggregants, are effective in protecting individual trees and forest stands. Further work in this system may lead to the development of a variety of new and useful tactics for use in various integrated pest management strategies. [ABSTRACT FROM AUTHOR]

Exotic ambrosia beetles (Curculionidae: Scolytinae) in the tribe Xyleborini include destructive pests of trees growing in horticultural cropping systems. Three species are especially problematic: Xylosandrus compactus (Eichhoff), Xylosandrus crassiusculus (Motschulsky), and Xylosandrus germanus (Blandford). Due to similarities in their host tree interactions, this mini-review focuses on these three species with the goal of describing their host-selection behaviour, characterising associated semiochemicals, and assessing how these interactions relate to their management. All three of these Xylosandrus spp. attack a broad range of trees and shrubs. Physiologically stressed trees are preferentially attacked by X. crassiusculus and X. germanus, but the influence of stress on host selection by X. compactus is less clear. Ethanol is emitted from weakened trees in response to a variety of stressors, and it represents an important attractant for all three species. Other host-derived compounds tested are inconsistent or inactive. Verbenone inhibits attraction to ethanol, but the effect is inconsistent and does not prevent attacks. Integrating repellents and attractants into a push–pull management strategy has been ineffective for reducing attacks but could be optimised further. Overall, maintaining host vigour and minimising stress-induced ethanol are keys for managing these insects, particularly X. crassiusculus and X. germanus. [ABSTRACT FROM AUTHOR]

Three species of ambrosia beetles (Trypodendron lineatum (Olivier), Gnathotrichus sulcatus (LeConte), and G. retusus (LeConte) (Coleoptera: Curculionidae: Scolytinae)) have been estimated to cause annual losses of $95–$189 million in degrade of logs and lumber on the British Columbia coast, in Canada. A consultant-run semiochemical-based integrated pest management programme was implemented in 1982 against these beetles, following fulfilment of four prerequisites: (1) presence of receptive potential clients, (2) availability of semiochemical lures, (3) invention of an operational trap, and (4) proof of concept of mass trapping technology. The programme is based on two broad strategies: maintain the problem at a tolerable level and, if necessary, reduce the problem to a tolerable level. One measure of effectiveness over 12 years of mass trapping at a dryland sort near Sooke, on Vancouver Island, British Columbia, was 16.4 million beetles trapped and an estimated five to one benefit-to-cost ratio. Despite success, several factors have conspired to reduce the programme from 50 sites serviced in early years to 7 in 2018. Timber companies in British Columbia are currently showing renewed interest and are taking steps to incorporate the integrated pest management programme as a formal component of their overall operations. [ABSTRACT FROM AUTHOR]

This paper reviews the literature on the identification of 3-methylcyclohex-2-en-1-one (MCH) as the antiaggregation pheromone of the Douglas-fir beetle (Dendroctonus pseudotsugae Hopkins) (Coleoptera: Curculionidae) and the development of successful management applications using the pheromone. Previously unpublished data from two studies on novel uses of MCH are included. The successful development of antiaggregation pheromone-based treatments for the Douglas-fir beetle is discussed in relation to efforts to develop similar treatments for other bark beetle species, and opportunities for future research on MCH and the Douglas-fir beetle are suggested. [ABSTRACT FROM AUTHOR]

This paper is intended as an assessment of the state of knowledge and development of semiochemical methods for control of bark beetles (Coleoptera: Curculionidae) in western North America and as a roadmap for future research and development in this field. It is based on a keynote presentation given at the symposium Managing Bark and Ambrosia Beetles with Semiochemicals, held in 2018 in Vancouver, British Columbia, Canada, at the Joint Meeting of the Entomological Society of America, the Entomological Society of Canada, and the Entomological Society of British Columbia. We describe currently available active ingredients, formulations, and release devices. Furthermore, we describe the most urgently needed new products and techniques, and constraints to their further development. Finally, we speculate about opportunities afforded by new advances in microbial synthesis of semiochemicals, streamlining of regulatory processing, and aerial application using unmanned aerial vehicles. [ABSTRACT FROM AUTHOR]

On 14 November 2018, a symposium Managing bark and ambrosia beetles with semiochemicals was held in Vancouver, British Columbia, Canada, at the Joint Meeting of the Entomological Society of America, the Entomological Society of Canada, and the Entomological Society of British Columbia. The focus was on the application of behavioural chemicals for management of bark and ambrosia beetles (Coleoptera: Curculionidae: Scolytinae) in conifers and hardwoods in North America and Europe. Contributors included nine invited speakers from Canada, Slovakia, and the United States of America who summarised the current state of knowledge and latest technologies and shared career-long experiences and insights. This special issue features publications derived from those presentations. [ABSTRACT FROM AUTHOR]

Porapak Q-captured volatiles from both sexes of Trypodendron betulae Swaine (Coleoptera: Curculionidae: Scolytinae) excised from newly attacked logs of paper birch, Betula papyrifera Marshall (Betulaceae), as well as volatiles from unattacked birch logs, were analysed by coupled gas chromatographic electroantennographic detection analysis. Active compounds were identified by gas chromatographic mass spectroscopy. The enantiomeric ratio of 6-ethenyl-2,2,6-trimethyloxan-3-ol (linalool oxide pyranoid) was determined using a Cyclodex B column. Field-trapping experiments disclosed that the female-produced aggregation pheromone of T. betulae is a blend of the (3S,6R)-trans- and (3R,6R)-cis-linalool oxide pyranoid. Trap catches were synergistically increased when the pheromone was combined with both the host volatile ethanol and with conophthorin, which was found in female beetles as well as host volatiles. Use of linalool oxide pyranoid reproductively isolates T. betulae from sympatric Trypodendron Stephens species for which only (+)-lineatin has been identified as an aggregation pheromone. [ABSTRACT FROM AUTHOR]

When I accepted the invitation to serve as the lead-off speaker for the symposium Managing Bark and Ambrosia Beetles with Semiochemicals on which this special issue is based, I noted that everything one needed to know was published in Seybold et al. (2018), a really good review of the subject. So, I took another course. About 25 years ago, I gave an oral presentation in the form of a letter to an imaginary graduate student. It seemed to go over well, so I decided to do it again. Here is a version of that letter to Sarah, the latest prospective graduate student conjured up by my imagination. [ABSTRACT FROM AUTHOR]