Steven J. Seybold's research while affiliated with University of California, Davis and other places

Publications (212)

Article
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 investi...
Chapter
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The introduction, establishment, and spread of invasive species in terrestrial and aquatic environments is widely recognized as one of the most serious threats to the health, sustainability, and productivity of native ecosystems (Holmes et al. 2009; Mack et al. 2000; Pyšek et al. 2012; USDA Forest Service 2013). In the United States, invasive speci...
Article
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...
Article
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Thousand cankers disease (TCD), is an invasive insect-disease complex caused by the walnut twig beetle, Pityophthorus juglandis, and fungal pathogen, Geosmithia morbida. Semiochemical interruption is a viable option for protecting walnut trees from P. juglandis attack. The goal of this study was to test beetle responses to potential repellent compo...
Article
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The walnut twig beetle, Pityophthorus juglandis Blackman, and its associated fungal pathogen that causes thousand cankers disease, currently threaten the viability of walnut trees across much of North America. During a 2011 assessment of seasonal flight patterns of P. juglandis with yellow sticky traps baited with the male-produced aggregation pher...
Article
1. 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. 2. The assay was conducted over 7 days (22 May to 29 May...
Article
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The invasive ambrosia beetle polyphagous shot hole borer is one member of the cryptic species, Euwallacea nr. fornicatus (Eichhoff), and poses a great ecological and environmental threat to ornamental and native hardwood trees and agriculturally important tree crops in southern California, United States. We monitored the emergence of polyphagous sh...
Article
• The host selection behaviour of the walnut twig beetle, Pityophthorus juglandis , was assessed by monitoring the landing rates of the beetles with sticky sheet traps on the host and nonhost hardwood branches. • Sticky sheet traps were deployed for 8 weeks from 6 June to 2 August. 2017 in the Putah Creek Riparian Reserve, Davis, CA . Branches from...
Article
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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 m...
Article
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The walnut twig beetle, Pityophthorus juglandis Blackman (Coleoptera: Scolytidae), vectors a phytopathogenic fungus, Geosmithia morbida Kolařík et al. (Hypocreales), which causes thousand cankers disease (TCD) in walnut (Juglans sp.) and wingnut (Pterocarya sp., both Juglandaceae) trees. We investigated an early point in disease inception in two wa...
Article
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The walnut twig beetle, Pityophthorus juglandis Blackman (Coleoptera: Scolytidae), vectors the fungus Geosmithia morbida, which has been implicated in thousand cankers disease of walnut. Little is known about the flight behavior of the insect across seasons, or about the variability in its flight patterns with weekly fluctuations in weather. We sam...
Article
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Key message We assessed the impact of the polyphagous shot hole borer (PSHB), Euwallacea whitfordiodendrus (Schedl), and Kuroshio shot hole borer (KSHB), E. kuroshio Gomez and Hulcr, on hardwood trees in southern California, southwestern China, and northwestern Vietnam. The highest levels of mortality were recorded from 10 of 39 tree species in the...
Article
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The walnut twig beetle, a native phloem-boring bark beetle originating on Arizona walnut, has invaded urban, orchard, and native forest habitats throughout the USA as well as in Italy. Although the beetle has been associated with dead and dying walnut trees indigenous to riparian forests of the Southwest, the primary impact appears to have been on...
Article
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Biological invasions by insects that vector plant pathogens have altered the composition of natural and urban forests. Thousand cankers disease is a new, recent example and is caused by the complex of walnut twig beetle, Pityophthorus juglandis, and the fungus, Geosmithia morbida, on susceptible hosts, notably some Juglans spp. and Pterocarya spp....
Article
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Thousand Cankers Disease (TCD) affects Juglans and Pterocarya species. This disease poses not only a major threat to the nut and timber industries but also to native stands of walnut trees. Galleries created by Pityophthorus juglandis (vector) are colonized by the fungus Geosmithia morbida (causal agent of necrosis). It is unknown if other fungi co...
Article
We summarize the status of semiochemical-based management of the major bark beetle species in western North America. The conifer forests of this region have a long history of profound impacts by phloem-feeding bark beetles, and species such as the mountain pine beetle (Dendroctonus ponderosae) and the spruce beetle (D. rufipennis) have recently und...
Article
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Thousand Cankers Disease (TCD) of Juglans and Pterocarya (Juglandaceae) involves a fungal pathogen, Geosmithia morbida, and a primary insect vector, Pityophthorus juglandis. TCD was described originally from dying Juglans nigra trees in the western United States (USA), but it was reported subsequently from the eastern USA and northern Italy. The di...
Data
Table A. Cross-amplification of Geosmithia morbida specific microsatellite locus GS 004 across fungal isolates known to co-inhabit walnut tree galleries. Table B. Cross amplification of Pityophthorus juglandis (WTB) specific microsatellite loci across twenty-four woodborning beetle species that are closely related to P. juglandis or are associated...
Article
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Due to recent outbreaks of native bark beetles, forest ecosystems have experienced substantial changes in landscape structure and function, which also affect nearby human populations. As a result, land managers have been tasked with sustaining ecosystem services in impacted areas by considering the best available science, public perceptions, and mo...
Article
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Winter survivorship of insects is determined by a combination of physiological, behavioral, and microhabitat characteristics. We characterized the cold tolerance of the walnut twig beetle, Pityophthorus juglandis Blackman, a domestic alien invasive bark beetle that vectors a phytopathogenic fungus. The beetle and fungus cause thousand cankers disea...
Article
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Fungi in the genus Geosmithia (Ascomycota: Hypocreales) are frequent associates of bark beetles and woodborers that colonize hardwood and coniferous trees. One species, Geosmithia morbida, is an economically damaging invasive species. The authors surveyed the Geosmithia species of California and Colorado, USA, to (i) provide baseline data on taxono...
Article
The walnut twig beetle, Pityophthorus juglandis Blackman, and associated fungus Geosmithia morbida Kolařík, Freeland, Utley, & Tisserat constitute the insect-fungal complex that causes thousand cankers disease in walnut, Juglans spp., and wingnut, Pterocarya spp. Thousand cankers disease is responsible for the decline of Juglans species throughout...
Article
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The walnut twig beetle [WTB (Pityophthorus juglandis Blackman)] is the primary insect vector for a pathogen that causes thousand cankers disease (TCD), a disease complex that leads to mortality in species of walnut (Juglans L.). We performed field and laboratory trials to determine if reproduction by WTB varies between two black walnut (Juglans nig...
Article
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Recent bark beetle outbreaks in North America and Europe have impacted forested landscapes and the provisioning of critical ecosystem services. The scale and intensity of many recent outbreaks are widely believed to be unprecedented. The effects of bark beetle outbreaks on ecosystems are often measured in terms of area affected, host tree mortality...
Poster
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Thousand Cankers Disease (TCD) complex involves Juglans spp., the fungal pathogen, Geosmithia morbida, and the vector, Pityophthorus juglandis. TCD, originally described from the western United States (USA), has now expanded to the eastern USA and northwestern Italy. The disease complex is often difficult to diagnose because of the absence of sympt...
Article
The polyphagous shot hole borer (PSHB), Euwallacea sp., was first detected in 2003 in Los Angeles County, California, USA. Recently, this invasive species has become a major pest of many hardwood trees in urban and wildland forests throughout southern California. PSHB is nearly identical in morphology and life history to the tea shot hole borer (TS...
Poster
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The USDA Forest Service works with a wide assortment of partners to detect, respond to, and manage invasive species that threaten the Nation’s wildland and urban forests, and rangelands, but a current comprehensive and integrated assessment of the state of invasive species science and research is lacking. Increased science that focuses on quantifyi...
Chapter
This chapter discusses the native ranges, histories of introduction, recent research efforts, and the potential impacts of some of 22 species of invasive scolytids in California’s Mediterranean forest ecosystems. The diversity of native and ornamental tree species, the varied climatic zones, and the widespread importation of nursery stock and packa...
Chapter
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In 2008, the goldspotted oak borer, Agrilus auroguttatus Schaeffer (Coleoptera: Buprestidae), was first linked to elevated levels of oak mortality in southern California (CA), but it appears to have impacted oak woodlands and mixed conifer forests across all land ownerships in this region for nearly two decades. This unexpectedly damaging indigenou...
Research
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1.Eastern black walnut parent cultivars tested in the field appear to be equally suitable hosts for walnut twig beetle reproduction. 2.Black walnut and butternut appear to be equally suitable hosts when tested in the field. 3.Eastern black walnut parent cultivars and butternut from the Midwest, USA, tested in the laboratory, appear to be equally su...
Article
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The walnut twig beetle (WTB), Pityophthorus juglandis Blackman (Coleoptera: Curculionidae), vectors a fungus, Geosmithia morbida Kolařík, Freeland, Utley, and Tisserat (Ascomycota: Hypocreales), which colonises and kills the phloem of walnut and butternut trees, Juglans Linnaeus (Juglandaceae). Over the past two decades, this condition, known as th...
Article
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Thousand cankers disease (TCD) of walnut trees (Juglans spp.) results from aggressive feeding in the phloem by the walnut twig beetle (WTB), Pityophthorus juglandis, accompanied by inoculation of its galleries with a pathogenic fungus, Geosmithia morbida. In 1960, WTB was only known from four U.S. counties (in Arizona, California, and New Mexico),...
Article
The invasive goldspotted oak borer, Agrilus auroguttatus, is threatening the health and survival of oak trees in San Diego Co., CA, USA. From two sites in the core area of the infestation, we report a 2.5-yr investigation of the impact of A. auroguttatus on coast live oak, Quercus agrifolia, before and after treatment with two systemic insecticides...
Article
1 Newly-established populations of invasive wood-inhabiting insects provide an opportunity for the study of invasion dynamics and for collecting information to improve management options for these cryptic species. 2 From 2011 to 2013, we studied the dynamics of the goldspotted oak borer Agrilus auroguttatus Schaeffer (Coleoptera: Buprestidae), a ne...
Conference Paper
The walnut twig beetle (WTB), Pityophthorus juglandis, causes thousand cankers disease of walnut, Juglans sp., when phoretic Geosmithia morbida spores are introduced as WTB bores into the phloem. Thousand cankers disease has caused widespread mortality among native and adventive California black walnut, Juglans hindsii, as well as adventive eastern...
Conference Paper
Walnut twig beetle, Pityophthorus juglandis Blackman, is a domestic invasive insect that has expanded its geographic range within the United States from the Southwest, through the West, and into isolated areas in the East. This beetle vectors a phytopathogenic fungus, Geosmithia morbida (Kolařík), found to cause cankers in many species of Juglans....
Conference Paper
Thousand cankers disease of walnuts, caused by the fungal pathogen, Geosmithia morbida, has led to the decline and death of native and introduced walnut trees, Juglans spp., throughout the USA. The pathogen is vectored as conidia by the walnut twig beetle (WTB), Pityophthorus juglandis, as it bores through the bark and enters the phloem. We trapped...
Article
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The ascomycete Geosmithia morbida and the walnut twig beetle Pityophthorus juglandis are associated with thousand cankers disease of Juglans (walnut) and Pterocarya (wingnut). The disease was first reported in the western United States (USA) on several Juglans species, but has been found more recently in the eastern USA in the native range of the h...
Conference Paper
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Goldspotted oak borer, Agrilus auroguttatus, has killed approximately 27,000 mature oaks in southern California. Consequently, the future spread of this insect is a significant concern to many oak woodland managers in California and across the United States. “Risk” reflects the likelihood that A. auroguttatus will continue to spread in North Americ...
Article
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The Douglas-fir tussock moth (DFTM), Orgyia pseudotsugata McDunnough (Lepidoptera:Erebidae:Lymantriinae), is a native western North American defoliator of true fir, Abies spp. Mill., and Douglas-fir, Pseudotsuga menziesii (Mirb.) Franco. We investigated the population genetics and impact associated with the first recorded outbreak of DFTM in southe...
Article
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Seasonal and diurnal flight patterns of the invasive walnut twig beetle, Pityophthorus juglandis, were assessed between 2011 and 2014 in northern California, USA in the context of the effects of ambient temperature, light intensity, wind speed, and barometric pressure. Pityophthorus juglandis generally initiated flight in late January and continued...
Conference Paper
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Background/Question/Methods Physiological drought stress triggers a cascade of responses that, depending on the level of stress experienced, may or may not predispose the tree to a successful bark beetle attack. Our hypotheses were that 1) under moderate physiological drought stress, resin production is stimulated, and turgor potential of the bol...
Article
Geosmithia morbida, the causal agent of thousand cankers disease (TCD), is vectored by the walnut twig beetle (WTB), Pityophthorus juglandis, causing decline in eastern black walnut, Juglans nigra (4), and canker development on many Juglans species (5). In the summer of 2012, a survey for TCD incidence in English walnut, J. regia, in orchards in Ca...
Article
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The goldspotted oak borer, Agrilus auroguttatus Schaeffer (Coleoptera: Buprestidae), is an invasive species that has colonized oak woodlands in southern California. To better define its seasonal flight activity, assist with forest and integrated pest management activities, and define the current distribution in California, an effective monitoring t...
Article
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The straw itch mite, Pyemotes tritici Lagrèze-Fossat and Montané (Acari: Pyemotidae), was discovered parasitising the goldspotted oak borer, Agrilus auroguttatus Schaeffer (Coleoptera: Buprestidae), an invasive exotic species to California, United States of America, and the Mexican goldspotted oak borer, Agrilus coxalis Waterhouse (Coleoptera: Bupr...
Article
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First records of Pityophthorus solus (Blackman, 1928) (Coleoptera: Curculionidae: Scolytinae) for Europe are reported. Twenty one specimens were obtained unintentionally during surveys for Ips sexdentatus (Boemer, 1767) and for Pityophthorus juglandis Blackman, 1928 using multiple funnel traps baited with specific attractants for both species in th...
Article
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We investigated within-tree population density of a new invasive species in southern California, the goldspotted oak borer, Agrilus auroguttatus Schaeffer (Coleoptera: Buprestidae), with respect to host species and the community of other borers present. We measured emergence hole densities of A. auroguttatus and other borers on the lower stem (bole...
Article
Goldspotted oak borer, Agrilus auroguttatus Schaeffer (Coleoptera: Buprestidae), is a new invasive species in southern California, USA. The extent of the host range of this insect is not known, but this knowledge will have a major impact on assessment of the risks that this pest poses to oaks [Quercus spp. (Fagaceae)]. We conducted laboratory tests...