Kenneth F. Raffa

Kenneth F. Raffa
University of Wisconsin–Madison | UW · Department of Entomology

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587
Publications
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21,166
Citations

Publications

Publications (587)
Article
Biological invasions by insects entail several processes including spread and outbreaks that can cause widespread tree mortality. These processes are commonly viewed as a linear sequence because we often lack the mechanistic understanding needed to partition them. We explored an invasion that occurred over a large enough spatial scale and time fram...
Preprint
Society is confronted by interconnected threats to ecological sustainability. Among these is the devastation of forests by destructive non-native pathogens and insects introduced through global trade, leading to the loss of critical ecosystem services and a global forest health crisis. We argue that the forest health crisis is a public good social...
Article
Full-text available
Irruptive forest insects such as bark beetles undergo intermittent outbreaks that cause landscape-scale tree mortality. Despite their enormous economic and ecological impacts, we still have only limited understanding of the dynamics by which populations transition from normally stable endemic to irruptive densities. We investigated density-dependen...
Article
Full-text available
Non-native organisms have invaded novel ecosystems for centuries, yet we have only a limited understanding of why their impacts vary widely from minor to severe. Predicting the impact of non-established or newly detected species could help focus biosecurity measures on species with the highest potential to cause widespread damage. However, predicti...
Article
The cover image is based on the Original Article Combined drought and bark beetle attacks deplete non‐structural carbohydrates and promote death of mature pine trees by Nadir Erbilgin et al., https://doi.org/10.1111/pce.14197.
Article
How carbohydrate reserves in conifers respond to drought and bark beetle attacks are poorly understood. We investigated changes in carbohydrate reserves and carbon-dependent diterpene defenses in ponderosa pine trees that were experimentally subjected to two levels of drought stress (via root trenching) and two types of biotic challenge treatments...
Article
Full-text available
Purpose of Review Outbreaks of tree-killing bark beetles have reached unprecedented levels in conifer forests in the northern hemisphere and are expected to further intensify due to climate change. In parts of Europe, bark beetle outbreaks and efforts to manage them have even triggered social unrests and political instability. These events have inc...
Preprint
Full-text available
Irruptive forest insects such as bark beetles undergo intermittent outbreaks that cause landscape-scale tree mortality. Despite their enormous economic and ecological impacts we still have only limited understanding of the dynamics by which populations transition from normally stable endemic to irruptive densities. We investigated density-dependent...
Article
Recent, widespread tree mortality in the western U.S. resulting from changes in climate, pathogens, insect activity, and forest management practices has led to concerns for many ecologically and culturally important species. Within conifers, resin-based defenses have long been recognized as a primary defense mechanism against a variety of insects a...
Article
Warming temperatures are allowing native insect herbivores to expand into regions that previously exceeded their thermal tolerance, encounter new host species, and pose significant threats to native communities. However, the dynamics of these expansions remain poorly understood, particularly in the extent to which outbreaks remain reliant on emigra...
Preprint
How carbohydrate reserves change in conifers during drought and bark beetle attacks are poorly understood. We investigated changes in carbohydrate reserves and carbon-dependent terpene defenses in ponderosa pine trees experimentally subjected to two levels of drought stress (via root trenching) and two types of biotic challenge treatments (pheromon...
Article
Full-text available
Climate warming can influence interactions between plants and associated organisms by altering levels of plant secondary metabolites. In contrast to studies of elevated temperature on aboveground phytochemistry, the consequences of warming on root chemistry have received little attention. Herein, we investigated the effects of elevated temperature,...
Technical Report
Full-text available
Evropské lesy poskytovaly lidské společnosti po staletí mnohé ekosystémové služby a generovaly značné ekonomické hodnoty. Některé z těchto benefitů jsou stále více ohrožovány změnou klimatu, která znásobuje vliv různých disturbančních činitelů, jako jsou např. kůrovci. Zranitelnost evropských lesů nepříznivě ovlivnil i jejich dlouhodobý management....
Article
Full-text available
Wildland fires have a multitude of ecological effects in forests, woodlands, and savannas across the globe. A major focus of past research has been on tree mortality from fire, as trees provide a vast range of biological services. We assembled a database of individual-tree records from prescribed fires and wildfires in the United States. The Fire a...
Article
Full-text available
Assessing the ecological and economic impacts of non-native species is crucial to providing managers and policymakers with the information necessary to respond effectively. Most non-native species have minimal impacts on the environment in which they are introduced, but a small fraction are highly deleterious. The definition of ‘damaging’ or ‘high-...
Article
Plants resist herbivores using both constitutive and induced defenses. Limited resources and biosynthesis costs of anti‐herbivore compounds may impose tradeoffs between these modalities, but the evidence is conflicting. We postulated that biological and ecological scale may influence potential tradeoffs and analyzed constitutive‐induced relationshi...
Article
Full-text available
Abstract A long‐standing goal of invasion biology is to identify factors driving highly variable impacts of non‐native species. Although hypotheses exist that emphasize the role of evolutionary history (e.g., enemy release hypothesis & defense‐free space hypothesis), predicting the impact of non‐native herbivorous insects has eluded scientists for...
Article
Full-text available
Interactions between water stress and induced defenses and their role in tree mortality due to bark beetles are poorly understood. We performed a factorial experiment on 48 mature ponderosa pines (Pinus ponderosa) in northern Arizona over three years that manipulated a) tree water stress by cutting roots and removing snow; b) bark beetle attacks by...
Article
Full-text available
Drought has promoted large‐scale, insect‐induced tree mortality in recent years, with severe consequences for ecosystem function, atmospheric processes, sustainable resources and global biogeochemical cycles. However, the physiological linkages among drought, tree defences, and insect outbreaks are still uncertain, hindering our ability to accurate...
Article
Plant interactions with herbivores and pathogens are among the most widespread ecological relationships, and show many congruent properties. Despite these similarities, general models describing how plant defenses function in ecosystems, and prioritization of responses to emerging challenges like climate change, invasive species, and habitat altera...
Article
The behavioral strategies and mechanisms by which some insects maintain monogamous mating systems are not well understood. We investigated the mating system of the bark beetle Dendroctonus valens, and identified several contributing mechanisms. Field and laboratory observations suggest the adults commonly form permanent bonds during host colonizati...
Technical Report
Full-text available
Europe’s forests have provided human societies with essential ecosystem services and great economic values for centuries. Some of these values are now increasingly threatened by climate change, which greatly intensifies forest disturbances such as bark beetle outbreaks. However, some past management practices have also increased the vulnerability o...
Article
Conifers possess chemical and anatomical defenses against tree‐killing bark beetles that feed in their phloem. Resins accumulating at attack sites can delay and entomb beetles while toxins are delivered. Trees with high concentrations of metabolites active against bark beetle‐microbial complexes, and more extensive resin ducts, achieve greater surv...
Article
Full-text available
Invasive pathogens that cause stem cankers and wilts of trees, and insects that bore into bark and wood have proven extremely destructive to the world's forests and particularly difficult to manage once established Such pests are especially devastating when evolutionarily naïve host trees lack adequate natural defenses Modern tree improvement progr...
Article
Oak wilt is a lethal disease caused by the invasive fungus Bretziella fagacearum, which is transmitted belowground via root grafts and aboveground by sap beetles (Nitidulidae). Attempts to limit spread and impact of B. fagacearum emphasize limiting harvesting and pruning to periods of vector inactivity. However, there is limited information on sap...
Article
Full-text available
Bark beetles are eruptive forest insects that have the potential to cause landscape level mortality to conifer forests. The pine engraver, Ips pini (Say) (Coleoptera: Curculionidae), is the predominant pest of mature red pine (Pinus resinosa Aiton) plantations throughout the Great Lakes region of North America. Pine engraver attack elicits a locali...
Article
Full-text available
We investigated the influence of larval instar on the structure of the gut bacterial community in the Japanese pine sawyer, Monochamus alternatus (Hope; Coleoptera: Cerambycidae). The diversity of the gut bacterial community in early, phloem-feeding larvae is significantly higher than in later, wood-feeding larvae. Many of these associates were ass...
Article
• The mountain pine beetle Dendroctonus ponderosae (Coleoptera: Curculionidae) is an irruptive tree‐killing bark beetle native to pine stands in western North America. The primary hosts are lodgepole and ponderosa pines. Recent rising temperatures, however, have allowed these beetles to survive at higher elevations more commonly than in the past, t...
Article
Recent mountain pine beetle outbreaks in whitebark pine forests have been extensive and severe. Understanding the climate influences on these outbreaks is essential for developing management plans that account for potential future mountain pine beetle outbreaks, among other threats, and informing listing decisions under the Endangered Species Act....
Article
Plants defend against herbivores and pathogens through integrated constitutive and induced defences. Induced responses may be expressed locally or tissue/plant-wide, i.e. systemically, and may also be primed for subsequent attack. Although the elicitation and efficacy of induced responses are increasingly well-characterised, we have little understa...
Article
Warming climate is allowing tree-killing bark beetles to expand their ranges and access naïve and semi-naïve conifers. Conifers respond to attack using complex mixtures of chemical defenses that can impede beetle success, but beetles exploit some compounds for host location and communication. Outcomes of changing relationships will depend on concen...
Article
Male preference for mating with large females and its benefits on fitness have been shown in several animal taxa. However, the mechanisms underlying this preference are less well known. Dendroctonus valens, a primarily monogamous bark beetle whose females initiate tunnels beneath the bark of host trees, provides a useful system for testing how male...
Article
Climate change is altering the frequency and severity of forest disturbances such as wildfires and bark beetle outbreaks, thereby increasing the potential for sequential disturbances to interact. Interactions can amplify or dampen disturbances, yet the direction and magnitude of future disturbance interactions are difficult to anticipate because un...
Article
Full-text available
Fire injury can increase tree susceptibility to some bark beetles (Curculionidae, Scolytinae), but whether wildfires can trigger outbreaks of species such as mountain pine beetle (Dendroctonus ponderosae Hopkins) is not well understood. We monitored 1173 lodgepole (Pinus contorta var. latifolia Doug.) and 599 ponderosa (Pinus ponderosa Doug. ex Law...
Data
Correlations between fire injury measures within lodgepole and ponderosa pines. (DOCX)
Data
Model parameters for the number of bark beetles caught in flight intercept traps. (DOCX)
Data
Model parameters for binomial models of fire injury categories predicting tree mortality and MPB attack. (DOCX)
Data
Parameters providing the best fit for the likelihood of attack by mountain pine beetle on lodgepole pine. (DOCX)
Data
Parameters providing the best fit for the likelihood of attack by mountain pine beetle on ponderosa pine. (DOCX)
Data
Comparisons of mountain pine beetle performance in presence or absence of Ips. (DOCX)
Data
Mean numbers of Ips spp. and other Scolytinae beetles caught in unbaited flight intercept traps. (TIF)
Data
Parameters for mountain pine beetle reproduction models. (DOCX)
Data
Mensurational characteristics of lodgepole and ponderosa pines in study sites. (DOCX)
Data
Likelihood ratio tests for binomial models of fire injury categories predicting tree mortality and MPB attack. (DOCX)
Article
Full-text available
For insects that aggregate on host plants, both attraction and antiaggregation among conspecifics can be important mechanisms for overcoming host resistance and avoiding overcrowding, respectively. These mechanisms can involve multiple sensory modalities, such as sound and pheromones. We explored how acoustic and chemical signals are integrated by...
Article
Subterranean termites need to minimize potentially pathogenic and competitive fungi in their environment in order to maintain colony health. We examined the ability of Actinobacteria isolated from termite guts in suppressing microorganisms commonly encountered in a subterranean environment. Guts from two subterranean termite species, Reticulitermes...
Article
Full-text available
Extensive mortality of whitebark pine, beginning in the early to mid-2000s, occurred in the Greater Yellowstone Ecosystem (GYE) of the western US, primarily from mountain pine beetle but also from other threats such as white pine blister rust. The climatic drivers of this recent mortality and the potential for future whitebark pine mortality from m...
Article
Full-text available
The evolution of cellulose degradation was a defining event in the history of life. Without efficient decomposition and recycling, dead plant biomass would quickly accumulate and become inaccessible to terrestrial food webs and the global carbon cycle. On land, the primary drivers of plant biomass deconstruction are fungi and bacteria in the soil o...
Data
Comparative analysis of CAZy genes across the Streptomyces genus. Multilocus phylogenetic tree of 126 strains with genomes. Taxonomy tree is a RAxML tree calculated from an alignment of 97 genes conserved across all species. Tree is rooted with the outgroup Kitasatospora setae, and bootstrap support for each node is indicated (100 bootstraps). Tree...
Data
Comparative analysis of Streptomyces phylogeny and the CAZy gene profile. Streptomyces multilocus phylogeny is shown on the left side and is annotated with the filter-paper degrading activity. The tree on the right represents the similarity of CAZy gene content in each genome. Total CAZy profiles were analyzed by Spearman rank correlation, and the...
Data
Comparative analysis of ABC sugar transporter genes across the Streptomyces genus. Multilocus phylogenetic tree of 126 strains with genomes. Taxonomy tree is a RAxML tree calculated from an alignment of 97 genes conserved across all species. Tree is rooted with the outgroup Kitasatospora setae, and bootstrap support for each node is indicated (100...
Data
Evolution of the CebR transcriptional regulator in cellulolytic and low activity strains. (a) Comparison of Streptomyces multilocus phylogenetic tree and the CebR gene tree. Tree is rooted with the outgroup Streptomyces sp. MnaMP-M17. Posterior probabilities for each node are indicated. CebR gene tree is annotated with the number of CebR binding si...