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COVID-19 Updates: CCAPS and the University

NAFIWC Program: 5/26/21

Wednesday, May 26

All times are listed in Central Daylight Saving time.

 

8:00 a.m. – Welcome Remarks

8:15 – Plenary Session 1

Moderator: Jess Hartshorn

Shannon Lotthammer, Assistant Forestry Commissioner, Minnesota Department of Natural Resources

 

EAB Impacts: What Does the Loss of Ash Mean for Wildlife?

Alexis Grinde, Wildlife Ecologist, Natural Resources Research Institute, University of Minnesota Duluth

 

Connections

Eli Sagor, Cloquet Forest, University of Minnesota

 

9:45 – Break

Moderator: Jess Harshorn

 

Following Celtis laevigata Willd. Mortality and the commonly associated insects in the southeastern US

Emilee M. Poole, Michael D. Ulyshen, Scott Horn

Celtis laevigata Willd. (sugarberry) is a native tree commonly found along floodplains and rivers in the southeastern US. This species has been declining in the region since 2008, when reports were first made around Columbia, SC. Consistent symptoms are small yellow leaves, branch dieback, and premature leaf fall. A buprestid species, Agrilus macer LeConte, and a nonnative aphid, Shivaphis celti Das, are commonly associated with dying sugarberry. Efforts have been made to map the geographic range of areas with high mortality and investigate the associated insects to determine whether the species are causal agents. Although symptomatic trees are present throughout South Carolina and Georgia, our findings indicate A. macer is present in the southern United States, while most records centralize around Texas and Louisiana. This beetle is an opportunistic secondary pest on sugarberry but does not transmit harmful fungal pathogens. Future efforts to identify other contributing factors are underway as understudied, S. celti, is currently under investigation to determine its role in the mortality episode.

 

Disease-induced changes in bark structure and pathogen interactions impact host-insect-pathogen dynamics in the beech bark disease system

Ken Windstein, Eric Morrison, Jeff Garnas

Beech bark disease (BBD) arises from the interaction between American beech, an exotic scale insect, Cryptococcus fagisuga, and two species of Neonectria fungi. While the scale insect is a key facilitator of disease along its advancing front, the strength and nature of dynamic feedbacks between insects and fungi – particularly in the context of a variable tree response – are poorly understood in the BBD aftermath range.  BBD development and severity is highly variable across time and space. We hypothesize that feedbacks between disease agents, principally indirect antagonistic effects mediated through BBD-induced changes in bark structure, are largely responsible for this variation, and so are important for understanding and managing BBD. We employed a field experiment implemented in the late summer and early fall of 2019 comprising an artificial challenge assay experiment applying two egg densities of C.  fagisuga on 80 American beech, stratified by bark response type.  On half of these trees, we inoculated Neonectria faginata and N. ditissima (and their combination) in 6mm agar plugs, also across scale insect densities and bark types.  The results of both field experiments were then assessed in late July 2020 to quantify scale insect establishment and fungal lesion growth. Preliminary results indicate that the area of necrosis caused by fungal inoculation growth is independent of initial scale insect density. Host bark structure, however, strongly affects fungal growth and scale insect colonization rate. Furthermore, lesion growth in the co-inoculation treatment was significantly reduced suggesting that these fungi may act as antagonists in the BBD system.

 

Translocation and persistence of dsRNA inducing gene silencing in southern pine beetle: prospects for tree protection

Zachary A. Bragg, Lynne K. Rieske

Exogenously applied double-stranded RNA (dsRNA) can induce potent host specific gene knockdown and mortality in insects. RNA-interference (RNAi) has proven effective in silencing genes and causing mortality in forest pests responsible for catastrophic losses, such as the southern pine beetle (Dendroctonus frontalis) and its conspecific mountain pine beetle (D. ponderosae). Yet deployment of gene silencing technologies for pest suppression in forest systems is lagging. Multiple barriers stand between laboratory screening and deployment; one such barrier is development of an efficient delivery technique. Delivery through host plants could serve as an effective mechanism for introducing pest-specific dsRNA for tree protection, but an understanding of exogenous dsRNA movement and retention through plant tissues is essential. To evaluate the persistence and movement of dsRNA within loblolly pine (Pinus taeda), seedlings were exposed to dsRNAs as a root soak and destructively sampled after exposure. Seedlings were divided into: roots, stems, needles, twigs with needles, and apical meristems, and total RNA was extracted from each tissue type, from which both semiquantitative (gel electrophoresis) and quantitative (melt curve and Sanger sequencing) analysis revealed the presence of the exogenously applied target dsRNAs. These results confirmed the presence of exogenous dsRNAs in each tissue type after 24h, 72h, 120h, and 168h of dsRNA exposure. These findings suggest that application of exogenous dsRNAs via root drench could provide single-tree protection against the southern pine beetle. Current efforts are focusing on evaluating insecticidal activity and determining the dose response.

 

Longleaf pine savanna after wind disturbance: management practices and lower stem and root feeding beetles and their associated blue stain fungi

Crystal Bishop, Kamal J. K. Gandhi, Kier D. Klepzig, Caterina Villari

Hurricane Michael impacted Southwest Georgia in 2018, causing major damage to forests in its path. Following initial wind damage, trees are at an elevated risk of colonization by lower stem and root feeding beetles and their associated blue-stain fungi, which can further decrease their health as well as accrue economic depreciation. To better understand the response of these insect-fungal complexes to extreme wind events, we established a project in a 12,000 Ha longleaf pine ecosystem that had been damaged by Michael. Across this area are 15 plots with three different management treatments: wind disturbed, wind disturbed followed by prescribed burning and salvage logging, and wind disturbed followed by prescribed burning but no salvage logging. We will use data collected from these plots to answer three research questions. First, what effects do current management treatments have on lower stem and root feeding beetle abundance? By using Lindgren funnel traps baited with attractants, we are determining beetle abundance within and among plots for a two-year collection period. Second, what fungi are commonly associated with these insects in the longleaf savanna? This question has been answered by live capturing beetles and culturing associated fungi on media selective for blue-stain fungi. Lastly, what fungi are associated with the roots of damaged pine trees within this system? To determine this, root samples from symptomatic and healthy pines were cultured to identify associated blue-stain fungi. With this project, we aim to better understand how these secondary agents affect longleaf pine forests after extreme wind damage.

 

SPB-specific gene silencing has no effect on nontarget insects

Hannah Hollowell, Lynne K. Rieske

The southern pine beetle (SPB) (Dendroctonus frontalis) has been the most destructive forest pest of the southeastern US for decades. Fortunately, RNA interference (RNAi), an emerging technology in pest suppression, shows promise for its management. RNAi is a cellular antiviral pathway triggered by exogenous double-stranded RNA (dsRNA), inhibiting the expression of targeted genes and preventing key cellular functions, thereby inducing mortality. By carefully designing dsRNAs specific to essential genes in SPB, we can trigger the RNAi pathway, silence target genes, and cause significant SPB mortality. But demonstrating the specificity of this approach is essential to its deployment. Through feeding bioassays assessing SPB-specific dsRNAs on nontarget insects, I evaluated potential lethal and sublethal effects on pine-associated insects. Nontarget insects were fed 10 ug of SPB-specific dsRNAs daily and evaluated. There was no effect on survival of the SPB-specific dsRNAs on the nontarget Ips calligraphus (p>0.05), and no sublethal effects on the pine defoliator, Neodiprion lecontei, when evaluated for larval weight gain or adult emergence (p>0.05). For the predatory Coleomegilla maculata, no effects were found on larval weight gain or fecundity (p>0.05). Food consumption of a detritivore, Reticulitermes flavipes, was also not affected (p>0.05). I plan to also conduct gene expression and bioinformatic analyses to gain a full understanding of potential nontarget effects of this innovative approach to SPB management. These findings are crucial to helping ensure the safety of deploying SPB-specific dsRNAs in forests and provide hope for the addition of gene silencing as a tool in IPM.

 

Oystershell scale: the awakening of a sleeper species in the southwestern US

Connor D. Crouch, Amanda M. Grady, Nicholas P. Wilhelmi, Richard W. Hofstetter, Daniel E. DePinte, Kristen M. Waring

Oystershell scale (Lepidosaphes ulmi; OSS) is an emerging invasive insect that poses a serious threat to conservation of quaking aspen (Populus tremuloides) in the southwestern US. Aspen is considered a keystone species in the conifer-dominated West, where it provides critical habitat for a wide range of species and makes a disproportionately large contribution to biodiversity. Although OSS’s origin is uncertain, the insect is believed to have arrived in North America with European settlers and was reported as a pest of apple trees in the 1700s. OSS is now present throughout much of the US and Canada and is a common pest of many deciduous tree species, including aspen, in urban settings. Historically, OSS has not been a concern in natural forests; however, the insect has recently migrated into natural aspen forests in Arizona, where outbreaks are causing aspen dieback and mortality. We hypothesize that OSS is a sleeper species that has recently awoken and entered the spread phase of invasion. In this presentation, we discuss our concerns about OSS’s hypothesized role as a sleeper species, potential interactions between OSS and climate change, and OSS’s polyphagous nature, all of which contribute to its potential as a high-impact invasive insect. We also present preliminary results from our observational studies of OSS, including presence and severity of the insect, mortality rates of aspen in infested stands, and the rate of OSS intensification. We conclude by providing recommendations for future work and highlighting the OSS severity rating system that we have developed for monitoring.

 

Impacts of a catastrophic hurricane on subcortical beetle populations in southern pine stands

Seth Spinner, Brittany F. Barnes, Elizabeth McCarty, Kamal J.K. Gandhi

Catastrophic wind disturbance events, such as hurricanes, tornadoes, and derechos, are major agents of ecosystem disruption in southeastern U.S. forests. On October 10th, 2018, Hurricane Michael made landfall, causing catastrophic damage to forests in Georgia and Florida. In these two states alone, this storm damaged approximately two million hectares of forests, resulting in nearly $2 billion in economic losses. Bark beetles (Coleoptera: Curculionidae: Scolytinae) frequently invade wind disturbed forests due to the influx of resources, such as weakened or recently killed trees. Similar patterns may occur after Hurricane Michael, leading to further economic damages. To date, there has been little to no research into the responses of bark beetles to catastrophic wind disturbance in southern pine forests. Our research objectives are to determine if bark beetle populations will change in number over time and if these changes will differ across various damage levels in southern pine forests. Beetle sampling was conducted during the summers of 2019 and 2020 using baited traps in fifteen loblolly pine stands that experienced 20–70% basal area loss. Preliminary results from June 2019 indicate that bark and ambrosia beetles were the most abundant in stands that experienced 20% damage and least abundant in sites that experienced >20–40 % loss. This may indicate greater diversity and availability of host resources in the least damaged pine sites. Results from this study will provide foresters with critical information regarding the timing of salvage logging in variously damaged sites to minimize economic losses from subsequent bark beetle infestations.

11:30 – Lunch

Founders Memorial Presentation

Speaker: Ken Raffa

Appreciating our careers as brief snapshots of forests, insects, and human values, but also an opportunity to help shape their shared trajectory.

Moderator: Deepa Pureswaran

 

Phytochemical response of loblolly pine (Pinus taeda) to southern pine beetle (Dendroctonus frontalis) symbiotic fungi

John de Soto, Kamal Gandhi, Kier Klepzig, Caterina Villari

Southern pine beetle (Dendroctonus frontalis) (SPB) is one of the most significant pests of pines in the southeast, capable of causing major losses. SPB is closely associated with three fungi; two mutualists, Ceratocystiopsis ranaculosus and Entomocorticium sp. A, serve as a nutritional supplement for SPB larvae, and one antagonist, Ophiostoma minus, competes for resources with SPB larvae and the mutualistic fungi. Prior research shows antagonism as a potential mechanism by which O. minus outcompetes the mutualists, but other mechanisms are possible. We hypothesize that the host defense response to O. minus, a moderately virulent plant pathogen, negatively impacts the mutualists more than O. minus due to the mutualists not being plant pathogens and therefore not having evolved abilities to withstand tree defenses. We are seeking to: (i) determine which terpenoid and phenolic defense compounds are induced in loblolly after inoculation of the three associated fungi, and (ii) test, in vitro, which individual compounds, or combination thereof, have effects on the fungi associated with SPB. We inoculated each of the three fungal species into ten mature trees within a loblolly pine stand at University of Georgia’s Whitehall Forest (Athens, Georgia). We measured lesions three weeks after inoculation and collected phloem samples which we are analyzing for the presence and quantity of defense metabolites. We anticipate that these results will lead to insights into the complex tree-insect-fungus interactions within the SPB system.

 

Identifying attractive semiochemicals for Anisandrus maiche (Stark)

Kelsey Tobin, Matthew Ginzel

Anisandrus maiche Stark (Coleoptera: Curculionidae: Scolytinae), an exotic ambrosia beetle native to Asia, has been spreading throughout the eastern United States since 2005. In the current invaded range, its preferred host plants are not well known, however, A. maiche has been found establishing galleries in plantation grown black walnut (Juglans nigra) and nearby forested land in northwestern Indiana. It is difficult to predict the impact A. maiche could have on North American forests. In this study, we conducted field-based trapping experiments in northwestern Indiana to explore the potential of ethanol and conophthorin as semiochemical attractants for A. maiche, as well as verbenone as a repellant. A. maiche capture in ethanol baited traps was significantly higher (p<0.001) than any other treatment group. These findings demonstrate bottle-traps baited with ethanol are useful in monitoring for A. maiche, and aid stakeholders in establishing effective management programs. Furthermore, it appears that conophthorin repelled A. maiche in our study, suggesting that semiochemicals may hold promise for manipulating the behavior of this species using a push-pull strategy to protect high-value plantings of black walnut from attack.

 

A novel use of protein immunomarking in studying the dispersal of woodboring beetles

Scott Gula, Vanessa M. Lopez, Ann M. Ray, Scott A. Machtley, James R. Hagler, Matthew D. Ginzel

Invasive woodboring beetles are among the most destructive pests of natural and managed forests worldwide. The success of eradication efforts and quarantines to limit the spread of incipient populations of these pests is dependent on understanding their dispersal behavior. Most previous dispersal research involved capturing or rearing beetles en masse, marking them in the laboratory, releasing them in the field, and capturing them again. This process is labor intensive, time consuming, expensive, and human handling during the application of the mark can affect the behavior of the insects. There is a critical need for an affordable, efficient, and non-invasive marking technique to improve research on woodborer dispersal. We tested the efficacy of protein immunomarking for use in understanding the dispersal of woodboring beetles. Specifically, we tested the extent to which a protein mark adheres to the cuticle of emerald ash borers (Agrilus plannipennis Fairmaire) (Coleoptera: Buprestidae) as beetles emerge from protein-treated logs. This method has several advantages over traditional techniques including a low cost for both the protein and ELISA used to detect the protein, no need for mass rearing or capture, and the minimization of handling and disturbance to the beetles. In addition, we tested the extent to which proteins transfer from marked to unmarked beetles as well as the efficacy of various trapping methods. This novel use of protein immunomarking has potential as an effective and reliable marker for use in mark-capture and dispersal studies with buprestids, as well as other woodborers such as cerambycids and scolytids.

 

Evaluating RNAi-mediated gene silencing for suppression of Ips calligraphus

Mary Wallace, Lynne K. Rieske

RNA interference (RNAi), or gene silencing, is a naturally occurring cellular antiviral response. By manipulating the pathway through the introduction of carefully designed exogeneous double stranded RNA (dsRNA), we can trigger the pathway, silence essential genes, and induce mortality. Inducing mortality in a target insect with minimal off-target effects makes this technology advantageous in integrated pest management programs. Thus, RNAi is emerging as a promising pest management strategy, and is already being implemented in agriculture. Susceptibility to RNAi in other Scolytines makes it a promising management tool for Ips calligraphus, the six-spined ips.  Ips calligraphus is a native North American bark beetle that, due to increasingly frequent and severe disturbance events, has become progressively more eruptive, with economic and ecological consequences in both its native and introduced ranges. To evaluate, adult beetles were fed dsRNA designed to silence specific essential genes, evaluated for mortality, and will then be evaluated for gene expression. We found evidence for activation of the RNAi pathway in the mortality assays, and are currently evaluating gene expression via qPCR. We plan to screen additional target genes for RNAi efficacy. This is the first study to investigate the feasibility of gene silencing via exogenous dsRNA in any Ips species, and is an important step toward developing this technology as an additional tool for IPM.

 

Ecological role and forest regeneration impacts of the eastern spruce budworm in Minnesota and Isle Royale

Jessica M. Rootes, Brian H. Aukema

Isle Royale National Park, located off the northeastern shore of Minnesota, consists of more than 450 islands that comprise approximately 130,000 acres of protected wilderness. This unique biosphere reserve is a haven for ungulates such as moose whose numbers have proliferated, resulting in undesirable levels of vegetation defoliation due to overbrowsing. This defoliation is further exacerbated by the native eastern spruce budworm (Choristoneura fumiferana).  Though an ongoing 50+ year study analyzes moose and wolf predator-prey relationships, more studies regarding lower trophic levels and their impacts on the island’s Balsam-fir forests are needed. These studies will help to fill knowledge gaps regarding the ecological impact of efforts to relocate wolves to the island. Despite the eastern spruce budworm’s potential large-scale impact and increasing populations, currently at a 20-year peak, this species has not yet been studied on Isle Royale. Outbreaks occur approximately every 35 years, last 10 years on average, and can result in 70% balsam fir and 40% white spruce mortality. My dissertation research will study the eastern spruce budworm’s ecological role and effects on forest regeneration to evaluate restoration goals on Isle Royale. The project will consist of comparisons of population dynamics and related factors, such as weather conditions, parasitoids, and dispersal, between mainland Minnesota and Isle Royale.

 

Predictors of mountain pine beetle dispersal in western Montana

August C. Kramer, Brian H. Aukema

Mountain pine beetle is an irruptive forest insect and disturbance agent in pine forests of western North America, infesting almost all western pine species. Past outbreaks have killed tens of millions of acres of mature pines across the western United States. In spite of abundant work on the insect’s ecology and tree killing capability, little is known about dispersal dynamics that are important to understand given potential threats of range expansion to pine forests of eastern North America. We exploited a recent outbreak from 2000 to 2015 in Montana that resulted in approximately six million acres of pine mortality to investigate how many fewer mountain pine beetles would be captured at distances farther away from active infestations. In the summer of 2020, we placed twenty baited Lindgren funnel traps along a 180-mile transect through western Montana from areas with established populations of mountain pine beetle to areas with no visible active infestations. Weekly collections were made from 4 August to 26 August. High numbers were captured at sites with no apparent proximate active infestations, and numbers varied weekly. While source populations cannot be confirmed, capture patterns away from pine forests can provide some insight into dispersal pressure given aerial and ground survey data.

 

Forecasting overwintering mortality of Spathius galinae in North America

Jacob T. Wittman, Brian H. Aukema, Jian J. Duan, Robert C. Venette

Matching classical biological control agents to appropriate environments for introduction is necessary to optimize their release and performance. We evaluated the cold hardiness of the parasitoid Spathius galinae Belokobylskij & Strazanac, a classical biological control agent of emerald ash borer (Agrilus planipennis Fairmaire) in North America. We measured supercooling points and lower lethal (i.e., mortality) temperatures of cold acclimated, late-instar S. galinae larvae in controlled cooling assays in the laboratory. The average supercooling point of S. galinae larvae was -25°C. Most S. galinae died after reaching their supercooling point, although several larvae initiated freezing but later successfully eclosed. The presence of larvae that eclose after initiating freezing suggest that some individuals may be partially freeze tolerant. We also monitored development of mature (cocooned) S. galinae larvae in ash segments above and beneath the snow in three locations in Minnesota in the winter of 2019–2020. Larvae that were exposed to -29°C exhibited nearly 100% mortality. We forecast eclosion rates of S. galinae across the range of Fraxinus spp. in North America based on minimum winter temperatures using models developed from these data. Our results indicate that a high proportion of S. galinae may survive in areas where minimum winter temperatures reach as low as -28°C. In areas where temperatures reach lower than -28°C, S. galinae will likely exhibit extensive mortality although a small portion of the population may survive and persist.

Moderator: Jeff Garnas

 

Preference of Geosmithia morbida for low wood moisture content may explain historical outbreaks of thousand cankers disease and predict future fate of Juglans nigra within its Native Range

Geoffrey M. Williams, Matthew D. Ginzel

Given its influence on emergent threats such as thousand cankers disease (TCD), climate change should be a key consideration in the assessment of risks to resources such as the high-value hardwood, Juglans nigra. TCD is caused by Geosmithia morbida and its vector, Pityophthorus juglandis. The success of mutualisms between fungi and bark beetles is likely to be limited by competition with other fungi that are better adapted to the physicochemical conditions of their substrate. These conditions are in turn subject to climatic variation. In particular, wood moisture content is an important factor in fungal competition, and therefore could help determine environmental suitability for thousand cankers disease. We conducted competition experiments in J. nigra wood that was naturally or artificially colonized by G. morbida and other fungi over a range of equilibrium wood moisture content expected across prevailing U.S. climatic conditions. Geosmithia morbida consistently and successfully outcompeted other fungi at very low (< 5%) equilibrium moisture content. However, Aspergillus spp., known pathogens of bark beetles, outcompeted G. morbida when colonizing low-moisture wood from Indiana. We also fit a logistic regression model to the results of the competition experiments to predict survival of G. morbida across the U.S. based on expected wood moisture content. Expected survival of G. morbida was highest in historical TCD epicenters and partly explained the low incidence and severity of TCD in the eastern U.S. Our results also predict that under future climate scenarios, the area impacted by TCD will expand into the native range of J. nigra.

 

Evaluating the effects of regional drought and forest management on invasive Sirex noctilio congener, Sirex nigricornis

Kendra E. Wagner, Robert Jetton, Jess Hartshorn, Dimitrios Avtzis, John J. Riggins

The European Woodwasp (Sirex noctilio Fabricius) was detected in North America in 2004. Thus far in North America, S. noctilio has not caused major tree mortality, despite its ability to cause >70% mortality in poorly managed stands throughout the Southern Hemisphere. Forest management practices (i.e. harvesting, stand density, etc.) significantly reduce S. noctilio related mortality, except for during significant drought years. Although not currently classified as invasive in North America, S. noctilio exhibits eruptive population dynamics. These populations often remain at low population levels for up to 12 years before reaching outbreak populations, therefore it should not yet be disregarded as a significant forest pest in North America. The objectives of this study are to determine how drought conditions and basal area interact to influence native woodwasp abundance and to develop forest management recommendations to minimize outbreak potential of their conger Sirex noctilio. A cross-hatched log stack and Lindgren funnel trap was used to sample siricid populations. Treatments included thinned and unthinned pine plantations in drought and non-drought stressed areas in Mississippi, North Carolina and Ontario, Canada. We found that drought-stressed areas presented higher woodwasp capture, but that basal area had no effect. These results may advise forest management as Sirex noctilio increases its range to the southeastern US.

 

Differential effects of fire regime on Ips bark beetles in longleaf pine forests

Haley M.W. Ritger, Steven T. Brantley, Joseph J. O’Brien, Kier D. Klepzig, Clinton T. Moore, Lindsay R. Boring,  Kamal J.K. Gandhi

Investigations into Ips spp. interactions with prescribed fire in the Southeast have been quite limited, and no previous study included species-level analysis of all three species that co-occur in the Gulf Coastal Plain. We assessed the effects of frequent fire, fire exclusion, and fire reintroduction on Ips spp. in mature longleaf pine (Pinus palustris Mill.) stands across two sites with different edaphic properties (mesic and xeric) in Newton, GA. We utilized funnel and pitfall traps baited with tree volatiles and beetle pheromones to trap Ips in 2016 and 2017 and measured forest stand characteristics. We employed an information theoretic statistical approach to determine that effects of factors and their interactions on trap catches of Ips spp. varied distinctly by species. While the highest trap catches for all three Ips species were in the fire exclusion treatment at the xeric site, catches of I. grandicollis (Eichhoff) were similar at both site types for the exclusion treatment. For the fire exclusion treatment, Ips avulsus (Eichhoff) and I. calligraphus (Germar) catches were 2–10 times higher at the xeric site compared to the mesic site. We used multivariate techniques to demonstrate that fire exclusion and site type affected stand conditions. Linear regression showed that I. calligraphus trap catches were positively associated with percent basal area of understory trees and I. avulsus trap catches were negatively correlated with total basal area. Our results suggest that site soil properties and stand conditions may play an important role in how fire regime differentially affects southeastern Ips species.

 

Community assembly of subcortical beetles and their associates on lightning-struck longleaf pine trees

Benjamin M. Gochnour, Tom Sheehan, Kier D. Klepzig, Kamal J. K. Gandhi

Cloud-to-ground lightning strikes are a widespread and rapid disturbance that causes tree damage and mortality in southeastern forest ecosystems. Tree damage by these strikes can create hot-spots for bark and woodboring beetle (Coleoptera: Curculionidae; Buprestidae and Cerambycidae) populations, especially pest species, and may sustain them between outbreak events. The spatial and temporal structure of bark beetle populations and their associated predators and parasitoids may be sustained by lightning-struck trees, as these colonization events are discrete, periodic, ephemeral, and self-propagating. Our research objectives were to: 1) characterize the assembly of subcortical beetles and their associates arriving at lightning struck longleaf pine trees; and 2) assess intrinsic and host variation in insect colonization dynamics. In summer 2020, detonation cord wrapped around the tree trunks of six longleaf pine (Pinus palustris) trees was used to simulate lightning strike trauma. Lindgren funnel traps, hung at several heights along the tree’s trunk, were used to monitor flight and arrival activity around the tree (both before and after detonation). Three trees were cut down and logs placed in emergence chambers to examine colonization success from sections of the tree trunk associated with the funnel traps. We determined arrival order of insect species and their numbers, flight height, and colonization height. Currently, we are identifying adults to species-level, and results will be analyzed using mixed linear models.  Results of this study will contribute to better understanding of the assembly of insect communities centered on lightning, an important and common ecological disturbance agent during storm events.

 

Change in fuel loads following severe drought and bark beetle outbreaks in the central and southern Sierra Nevada

Crystal S. Homicz, Leif A. Mortenson, Beverly M. Bulaon, Christopher J. Fettig

The disturbance ecology of many conifer forests in western North America has deviated drastically from historical conditions largely as a result of fire suppression, extreme drought events, and bark beetle outbreaks. These deviations were exemplified in 2012–2015 when the worst drought in over a millennium occurred throughout parts of California. During and following the drought, a western pine beetle (Dendroctonus brevicomis) outbreak occurred in the central and southern Sierra Nevada causing severe (>90% in some areas) ponderosa pine (Pinus ponderosa) mortality. The objectives of our study are to determine changes and variations in fuel loading over time, and to determine predictive variables of fuel loading following the outbreak. A network of 180 11.3-m fixed-radius plots were installed across three elevation bands on the Eldorado, Stanislaus, Sierra and Sequoia National Forests to monitor tree mortality levels, changes in tree species composition, and changes in fuel loading. Fuels data across the plot network were measured in 2017 and 2019 using modified Brown’s transects, and measurements will be repeated again in 2021 and 2023. Preliminary data show total surface fuel loading has increased from 2017 to 2019 across all national forests and elevation bands, with the largest increase on the Sierra National Forest. 1000-hour fuels increased more than any other fuels class and little change was observed in litter and duff. Better understanding of changes in fuel composition following bark beetle outbreaks in Sierra Nevada forests provides important context for land management decisions, especially as outbreaks likely increase in frequency and severity moving forward.

 

Comparing the effects of various natural and anthropogenic disturbances on insect pollinator diversity in mid-montane forests of the Californian southern Sierra Nevada

Gabriel G. Foote

Flower-visiting insects provide essential pollination services to herbaceous plant communities in temperate coniferous forests, thereby helping to maintain food webs and support the overall functional diversity of these systems. To guide conservation efforts for forest-associated populations in western North America, ecologists have investigated the effects of both natural (drought, insect outbreaks, wildfire) and anthropogenic (forestry operations) disturbances on local insect pollinator abundance and diversity. However, studies comparing their community responses to the different types of forest disturbance (i.e., abiotic versus biotic or anthropogenic) that have co-occurred within an individual forest landscape are few. To address this knowledge gap, we sampled the insect pollinator community during the summer of 2020 in undisturbed forest stands, combined with neighboring stands that underwent recent (post-2015) disturbance (drought, tree harvest, wildfire) located in mid-montane forest landscapes of the Californian southern Sierra Nevada. Disturbed stands had a higher diversity of pollinators compared to neighboring, undisturbed stands. However, the magnitude of these differences varied by both disturbance type and severity. Fire-disturbed plots with intermediate (40-70%) levels of tree mortality had the greatest diversity of insect pollinators, followed by unforested plots that had experienced complete tree removal. Only drought-affected stands that experienced relatively high (> 70%) tree mortality rates had a significantly greater diversity of pollinators compared to neighboring, undisturbed stands. Across the study region, pollinator diversity was positively correlated with mean tree diameter, exposed bare ground surface area, as well as floral resource abundance, while canopy cover, shrub cover and dead wood abundance were all negatively correlated with their diversity. Combined, these results indicate that allowing for certain disturbances (e.g., moderate severity wildfires) that reduce shrub cover, expose bare ground surfaces and promote herbaceous plant growth on the forest floor may be optimal mechanisms for land managers to passively create beneficial habitat for insect pollinators in this ecoregion.

 

Insect community responses to novel and co-evolved bark beetle pheromones: Predicting potential southern pine beetle associates in New England pine forests

Caroline Kanaskie, Matthew P. Ayres, Jeff Garnas

Arthropod communities associated with the southern pine beetle (SPB, Dendroctonus frontalis Zimmermann) are highly studied in southern U.S. forests where the beetle is among the most important pests of pine. This well-characterized community includes natural enemies, co-occurring and potentially competing Ips and other Dendroctonus bark beetles, and a suite of opportunistic species. As SPB moves north with changing climate, it will undoubtedly encounter novel communities. Community differences in the endemic and expanding range of SPB is a plausible driver of divergent behavior and population dynamics of the beetle. The SPB-associated insect community has only recently been described in detail in the expanding range as part of our research. We continue to fill this gap by comparing insect responses in New England forests to 3 different semiochemical lures: 1) SPB-focused (frontalin, alpha/beta pinene, with endo-brevicomin placed several meters away); 2) Ips-focused (ipsenol, ipsdienol, lanierone, alpha/beta pinene); 3) and a tree volatile control (alpha/beta pinene). Our study includes eight paired pitch and white pine sites (n=16) across Maine, New Hampshire, and Massachusetts. We compare traps catch across sites, latitude, and dominant pine species. These comparisons will help predict species’ responses to novel SPB pheromones in the beetle’s expanding range. Building on our previous study of SPB gallery communities in pitch pine in NY, this work provides baseline knowledge of regional species pools and facilitates future study of the consequence of the arrival of a novel keystone species, including community-scale adaptation and/or shifts in composition, abundance, or behavior.

3:00 – Concurrent Sessions 1

Moderators: Angela Mech, Ashley Schulz, Ruth Hufbauer

Availability and accumulation of data over the last few decades has allowed us to reexamine man unanswered questions, with large datasets being at the core of many multifaceted projects that have furthered the field of forest entomology. Our symposium will highlight some of the diverse uses of large data that have helped answer questions about predicting, monitoring, understanding, and controlling forest pests, and how these answers can be used to promote action that will keep our forests healthy.

  • Toward machine-assisted classification of bulk invertebrate specimens: Jarrett Blair
  • Genetic and environmental factors influencing pine host quality in the mountain pine beetle outbreak: Janice Cooke
  • Forest integrated pest management programs in the US with focus on the National Gypsy Moth Slow the Spread Program: Tom Coleman
  • Macroscale pest invasion dynamics and impacts in forest ecosystems across the US: Songlin Fei
  • Synthesis and utilization of big data for forecasting the impacts of non-native forest insects in North America: Ashley Schulz
  • Species-area relationships and other factors explaining numbers of native and non-native insect species utilizing North American and European host tree species: Sandy Liebhold

Moderators: Bob Rabaglia, Sheri Smith

 

Invasive ambrosia beetles have had an impact on the health of North America’s urban and rural forests.  In the past 30 years there has been an increasing number of these non-native beetles and impacts.  This session will discuss the species present in North America, highlight a few species having significant impacts, research to understand and manage them, and potential invaders in Asia.

 

Intro and overview of invasive ambrosia beetles in North America

Bob Rabaglia

There are nearly 70 species of non-native bark and ambrosia beetles established in North America.  Several species of ambrosia beetles in the tribe xyleborini are impacting urban and rural forests in the southeastern US and California.  Surveys by the USDA Forest Service and APHIS target new introductions of these species at ports and high-risk locations across the US.  As introductions and establishments of new non-natives continue it is important to understand pathways, target early detections and assess impacts of current and potential invaders across North America.

 

Update on invasive ambrosia beetles in California

Sheri Smith, Stacy Hishinuma

The Mediterranean oak borer (MOB), Xyleborus monographus, is an invasive ambrosia beetle native to the Mediterranean region, including Europe, the Middle East, and North Africa, where it primarily attacks oak species. The first North American infestations of MOB were confirmed in valley oaks in Napa County, California in late 2019, followed by Lake and Sonoma Counties in early 2020, and Sacramento County in September 2020. MOB attacks at least 12 species of oaks in its native range. In California, it has been found infesting two species of white oak: most commonly valley oak and, to a lesser extent, blue oak.  Several species of fungi have been found associated with MOB in Napa County, and research is underway to determine if these fungi cause tree diseases. For more information and a MOB pest alert can be found here: https://www.ucanr.edu/sites/mobpc/ In southern California, two species within the Euwallacea fornicatus species complex, Euwallacea fornicatus (polyphagous shot hole borer) and E. kuroshio (Kuroshio shot hole borer), have caused extensive tree mortality in urban areas. These beetles are now established in Santa Barbara, Ventura, Los Angeles, Orange, Riverside, San Bernardino, San Diego, and San Luis Obispo Counties with overlapping ranges in some counties. A statewide strategic initiative is underway to control these beetles through: 1) research and technology development; 2) survey, detection, and rapid response; 3) examining greenwaste and firewood as pathways for movement; 4) outreach and education. For more information please visit: https://ucanr.edu/sites/pshb/

 

Update on red bay ambrosia beetle and laurel wilt in the southeast

Bud Mayfield

The redbay ambrosia beetle (RAB), Xyleborus glabratus, was first detected in North America in 2002 near Savannah, GA and has since spread throughout the southeastern United States. One of its symbiont fungi, Raffaelea lauricola, causes a vascular disease known as laurel wilt that has killed hundreds of millions of trees in the family Lauraceae. This presentation will examine the known distribution, hosts, impacts, and management challenges associated with this insect-pathogen complex and its status as a potential threat to lauraceous plants in other regions of the world.

 

Xyleborine ambrosia beetles in southeast Asia and potential new invaders

Sarah Smith, Anthony Cognato

The greatest source of introduced xyleborine ambrosia beetles is Southeast Asia. Yet prior to 2019, a review of the fauna and comprehensive identification keys were non-existent. Recently 315 xyleborines mostly occurring mainland southeast Asia were reviewed in an illustrated monograph. Sixty-three new species were described, and other taxonomic changes were made. Dichotomous keys and web-based multi-entry keys were included. In addition, the foundation for a two gene DNA identification scheme was developed for the fauna.  We discuss the limits of morphological and DNA diagnostic characters, potential new invaders, and future taxonomic research.

Moderator: Rich Hofstetter

Recent studies found that if current trends continue, both the western and eastern monarch populations face migratory collapse within the next 20 years. In the 1990s the eastern population numbered nearly 1 billion butterflies, and the western population numbered more than 1.2 million. Last year’s winter counts recorded fewer than 30,000 western monarchs and around 225 million eastern monarchs. Forest habitat restoration and conservation efforts may benefit or be hampered by listing the monarch under the Endangered Species Act. In this session, we discuss the politics, ecology, citizen science, and conservation of the monarch butterfly as well as its use of forest habitats and interactions with forest ecosystems.                        

  • Warranted, but precluded: what that means for monarchs and the people who care about them: Karen Oberhauser
  • Partnering to bring all hands on deck for monarch conservation: Wendy Caldwell
  • Adult monarch abundance is higher in burned sites than in grazed sites: Julia Leone
  • Historical monarch overwintering colonies in central Mexico, 1976–1991: Wayne Thogmartin
  • Southwest milkweeds and their use by Monarchs: Rich Hofstetter
  • Open slot - TBD

Moderator: Nathan Havill

 

Healthy Trees, Healthy Cities

Chuck Bargeron, Michelle Johnson, Rich Hallett, Rachel Holmes

New tree-killing insects and diseases are often spotted first in cities, making tree health monitoring a priority not only for these trees themselves, but for the health of the entire North American forest ecosystem. Seven years ago, The Nature Conservancy, USDA Forest Service, and University of Georgia partnered on the development of a scientifically rigorous, non-stressor specific tree health monitoring protocol called Healthy Trees, Healthy Cities. The protocol is non-stressor specific making it a critical tool for the early detection of new, unknown insects or diseases. Furthermore, the protocol and an associated smart phone application (app) and web-based “dashboard” leverage the expertise of civic scientists and professionals alike, increasing public awareness of tree health issues. Learn about the methodology, new tools and updated training resources, as well as examples of where these tools have been used to improve tree health efforts in cities.

 

Balsam woolly adelgid mortality patterns in Idaho: from invasion to long-term establishment

Gina Davis, Laura Lowrey, Tom Eckberg, Jeffrey A. Hicke

More than 110 years after first reported in Brunswick, Maine the nonnative balsam woolly adelgid, BWA (Adelges piceae), continues to be a significant pest of true fir (Abies) species in eastern and western North America. Over the decades, reports of BWA-caused damage demonstrated that the intensity and extent of tree mortality varied temporally, spatially, and among host species. Further investigation into stand-level mortality patterns occurred during two separate monitoring efforts in Idaho where BWA-caused mortality rates were estimated following the discovery of BWA in the state (1986-2004) and after it was well established in most of the state (2008-2018). Observations from these two monitoring efforts are synthesized and address two key question; should forest managers expect similar stand-level mortality of true fir forests from BWA into the future; and if so, how much time do they have for mitigating losses once BWA infestations are evident?

 

Stand structure and climate influences on balsam woolly adelgid damage in Idaho:  A statistical analysis of field measurements

Jeffrey A. Hicke, Gina Davis, Ekaterina Smirnova, Leonid Kalachev, Laura Lowrey, Tom Eckberg

Balsam woolly adelgid (BWA) is an invasive insect in the western United States, attacking subalpine firs (Abies lasiocarpa) and grand firs (Abies grandis). Little is known about the stand structure and climate conditions favorable for BWA in these forests.  In 2018, tree and insect characteristics at 28 sites in Idaho were measured for the third time; previous measurements occurred 5 and 10 years before.  Here our objective was to identify stand and climate variables leading to BWA damage and tree mortality.  We used generalized additive modeling, which allows nonlinear relationships between the response and explanatory variables.  We modeled the proportion of host trees associated with BWA infestation.  We considered multiple explanatory variables grouped by process (insect pressure, stand structure, host species and size preferences, temperature, and precipitation) to avoid multicollinearity issues.  We used a modified forward selection process and considered AIC and cross-validation.  The top model included insect pressure (proportion of live host species basal area with BWA present five years ago) as the most important variable.  Basal area (BA) of host species 10 years ago, growing season precipitation, and water-year mean temperature were also included.  The BWA response variable linearly increased with increasing insect pressure, increased roughly linearly with increasing host BA, decreased with increasing temperature, and had a humped-shaped relationship with precipitation in which the highest BWA damage occurred at intermediate values.  Our results inform forest managers about the stand and climate conditions that make subalpine and grant fir stands susceptible to balsam woolly adelgid.

 

Insects respond to different systemic insecticides in different ways

Rhoda deJonge, Breanne Aflague, Jeff Garnas

Here we explain the unique mode-of-action of azadirachtin-based insecticides, and review recent studies that use this active ingredient to control the invasive emerald ash borer (EAB).  Azadirachtin is a plant-based active ingredient used in a number of organic insecticides on the market.  It controls insect pests by working within the insect-specific hormonal pathways, preventing molting, as well as limiting feeding and fecundity. We will share preliminary findings from a recent study conducted by Lallemand Plant Care (LPC) and the University of Toronto that reviews survivorship of azadirachtin-treated ash trees after ~10 years of EAB presence.  As well, we will share results of a recent field trial conducted by the University of New Hampshire to determine the efficacy of azadirachtin-based insecticides in a New England woodlot during peak EAB invasion. This brief talk will inform urban forestry professionals on actions they can take to maintain the health and survivorship of ash trees in their urban forests in order to preserve a diversity of age-classes and urban canopy cover, even during the peak of an EAB invasion.

 

Asian Giant Hornet Program Update

Karen Ripley

Asian giant hornet (Vespa manadarinia) was first detected in WA in 2019.  Information about the pest including biology, range, and potential impacts are discussed.  An overview of the response from WSDA is given including accomplishments from 2020.  Program status in 2021 is provided and research projects being conducted are outlined.

 

What is an adelgid, anyway? Species delimitation and invasion history in Adelgidae

Nathan Havill

Several adelgid species are high-impact invasive pests in forests and tree plantations in North America and Europe. Adelgid taxonomy is notoriously unstable due, in part, to their complex polymorphic life cycles that complicate morphological species delimitation. Genetic studies to inform adelgid systematics and population genetics can help us better understand their biology and inform pest management. I will discuss recent progress towards understanding the biogeographic history of adelgids using genetic data, focusing on hemlock woolly adelgid, balsam woolly adelgid, and pine adelgids (Pineus spp.).  It is common for adelgid species complexes to be in the midst of transition between a holocyclic life cycle (with host alternation and a sexual generation) and an anholocyclic life cycle (with no host alternation and only asexual generations). This pattern has implications for their taxonomy, pest impact, and invasion history.

5:00 – Poster Session and Student Poster Competition

Moderator: Rich Hofstetter

Marie Hallinen, Brian Aukema, Angie Ambourn, Robert Venette

The elongate hemlock scale (EHS), Fiorinia externa Ferris (Hemiptera: Diaspididae), is an insect from eastern Asia introduced to New York in the early 20th century. While it was historically found relatively close to its introduction point, it has greatly expanded its range since the 1970s and is now found in several New England and mid-Atlantic states and as far west as Michigan. In 2018, 2019, and 2020 EHS was found infesting wreaths, trees, and other greenery shipped into Minnesota to supplement Minnesota-grown Christmas trees. This armored scale has a wide host range and may feed and reproduce on many native local hosts, including firs and spruces, threatening forest health in addition to the Christmas tree industry in Minnesota. To assess the ability of EHS to survive winter temperatures in Minnesota we plan to measure the supercooling point, lower-lethal temperature, and lower lethal time of its overwintering stage. We will use these experiments to evaluate EHS’s ability to potentially expand westward and overwinter in Minnesota.

Cora Davies, Thomas Seth Davis

In North American conifer forests, thinning operations are broadly implemented as a means of fire hazard mitigation, ecological restoration, and timber harvest. Effects of thinning on forest bee communities are poorly understood but could be important for conservation of biodiversity and ecosystem services. Here, we test the hypothesis that thinned forest stands have greater diversity of native bee species than non-treated forests. To address this, native bee assemblages were collected across the growing season and compared between ponderosa pine stands treated by mechanical thinning and non-treated stands. Associations between native bee communities and forest conditions were analyzed. Forest structure, floral resources, nesting habitat, and bee assemblages differed between treated and non-treated stands. Forest basal area at non-treated sites was on average 3.5 times greater than treated sites, and canopy openness was greater at treated sites. Fuel loads were similar between treated and non-treated sites. Floral resources were >2.5 times more abundant at treated sites; floral abundance was highest in June and decreased throughout the summer.  Native bees were two times more abundant in treated stands. Our results suggest that (1) forest thinning has significant impacts on both floral resources and bee nesting habitats within 2-8 years post-treatment; (2) bee assemblages likely respond to this variation, and this difference is especially apparent later in the growing season. We conclude that forest thinning for ecological restoration in ponderosa pine habitats is likely to improve resources utilized by native bees and are associated with increased bee abundances in the wildland-urban interface.

Pheylan A. Anderson, Hailey N. Shanovich, Brian H. Aukema

Hybrid hazelnut crosses between the European hazelnut (Corylus avellana) and the American hazelnut (Corylus americana) are an emerging agroforestry crop in the Midwestern United States. European hazelnuts typically produce high yields, while American hazelnuts exhibit greater cold-hardiness and disease resistance. Hybrid hazelnuts are envisioned as a foundational species for making agroecosystems more sustainable: the perennial shrubs hold soil tightly, cycle nutrients, and do not require annual tillage inputs. However, little is known about how local insect communities will affect this novel crop. The hazelnut weevil, Curculio obtusus, is native to the US and typically infests native hazels in forests throughout the eastern United States. Curculio obtusus has been found to infest these new hybrid hazelnut cultivars across the Midwest, but little is known about what factors influence the severity or distribution of field infestations. We studied within-field distribution of C. obtusus by collecting a subsample of ten nuts from each of the 184 nut-bearing plants in an experimental hybrid hazelnut field in Rosemount, MN, and checked each for larvae or exit holes. Approximately 25% of the nuts were infested with hazelnut weevil larvae, highlighting the need for understanding factors influencing the insect’s infestation patterns. We analyzed spatial trends and whether factors such as plant genotype, historical rates of nitrogen application, plant height, and yield could predict weevil infestation using generalized linear mixed effect models.

Emily R. Althoff, Brian H. Aukema

Eastern larch or tamarack, Larix larcina (Du roi) K. Koch, ranges from Maine to Minnesota and Alaska in the United States, spanning almost 40,000 ha. of northern Minnesota. Within this range, tamaracks contribute to habitats for several birds and mammals and provide water filtration in northern wetlands, playing an essential role in these ecosystems. However, in the last 19 years, 40% of the state’s 1.26 million acres of tamarack stands have been killed by eastern larch beetle, Dendroctonus simplex LeConte. Historically, ELB has only attacked tamarack stressed by windfall, fire, mechanical injury, defoliation, drought, or flooding. This trend has changed in recent years as an outbreak of ELB has been ongoing in Minnesota since 2000. Previous studies have shown that warmer summer and/or extended growing seasons are facilitating bivoltine life cycles in a proportion of the population, demonstrating that some insects can reproduce without an obligate overwintering period. Information on the management of ELB is currently sparse as it has not been a widespread problem historically. In our future work, we plan to investigate stage-specific development and temperature triggers of a potential diapause in ELB, investigate potential semiochemical attractant or repellent lures for monitoring or management, and further advance understanding of associated natural enemies and competitors. Ultimately, we hope to assist in improving management practices and expand knowledge on how climate change influences insect development.

Breanne Aflague, Rhoda deJonge, Jeff Garnas

Injection of systemic insecticides is currently the most effective way to protect trees from the emerald ash borer, Agrilus planipennis Fairmaire (EAB). While previous academic studies have shown emamectin benzoate to be a highly effective active ingredient of these systemics, research on the use of azadirachtin-based insecticides in the control of EAB are limited.  Azadirachtin is a botanically-derived active ingredient that is used when an effective low-toxic option for insect control is desired. Azadirachtin persists in trees for up to two years but can fluctuate seasonally; therefore, injection frequencies and doses are important factors to consider. We tested the efficacy of two azadirachtin-based systemics, Lalguard Aza (6% a.i. at both 4 ml and 6.5 ml/inch DBH dose rates) and TreeAzin (5% a.i. at a  12.5 ml/inch DBH dose) injected either annually or biennially, and compared them to untreated ash trees in a New Hampshire woodlot. Live larval densities where highly variable and differed moderately across treatments (including controls). Late instar larvae, however, were significantly reduced by the annual application of the Lalguard’s low dose and at both injection frequencies by TreeAzin and Lalguard’s high dose (Likelihood ratio chi-squared = 130.2; df = 6; P < 0.001). We also found an important effect of tree microenvironment (i.e., soil saturation) and old gallery density on larval densities and  growth. These results suggest that both doses and injection frequencies of the Lalguard AZA and TreeAzin products are equivalently effective against EAB, though uptake can be inhibited in water-saturated microsites.

Christine Favorito, James A. Martin, Angela Larsen-Gray, Daniel Greene, Christine Cairns Fortuin, Brittany F. Barnes, Elizabeth McCarty, Kamal J.K. Gandhi

Insect pollinators provide critical services to both people and forest ecosystems through crop and native plant pollination. Of the many insect pollinators present in forests, two of the most important indicators of ecosystem function and health are Hymenoptera (bees) and Diptera (flies). Unfortunately, bees are globally declining due to many factors including habitat loss and climate change, while the trend for many fly species is unknown. It is important to recognize the various and common aspects of forest structure and composition that best support these pollinators. Few studies have focused on pollinators in forests, and even less have focused on private, working forests, which make up 86% of forests in the southeastern US. We aim to compare populations and communities of wild bee and fly pollinators in various age classes of working forests, and to test the effects of stand-level structure and composition on bee and fly populations and communities. We are sampling bee and fly pollinators in 32 loblolly pine (Pinus taeda) stands with four age-classes in the Upper Coastal Plain region of Georgia using pan and blue vane traps in a randomized block design. We are measuring aspects of forest structure and composition (e.g., understory plants and coarse-woody debris) critical for these pollinators. We are currently identifying collected specimens to species.  Results from this study will inform land managers of beneficial forest management practices for these pollinators that provide billions of dollars in pollination services annually.

Jessica M. Rootes, Brian H. Aukema

Isle Royale National Park, located off the northeastern shore of Minnesota, consists of more than 450 islands that comprise approximately 130,000 acres of protected wilderness. This unique biosphere reserve is a haven for ungulates such as moose whose numbers have proliferated, resulting in undesirable levels of vegetation defoliation due to overbrowsing. This defoliation is further exacerbated by the native eastern spruce budworm (Choristoneura fumiferana).  Though an ongoing 50+ year study analyzes moose and wolf predator-prey relationships, more studies regarding lower trophic levels and their impacts on the island’s Balsam-fir forests are needed. These studies will help to fill knowledge gaps regarding the ecological impact of efforts to relocate wolves to the island. Despite the eastern spruce budworm’s potential large-scale impact and increasing populations, currently at a 20-year peak, this species has not yet been studied on Isle Royale. Outbreaks occur approximately every 35 years, last 10 years on average, and can result in 70% balsam fir and 40% white spruce mortality. My dissertation research will study the eastern spruce budworm’s ecological role and effects on forest regeneration to evaluate restoration goals on Isle Royale. The project will consist of comparisons of population dynamics and related factors, such as weather conditions, parasitoids, and dispersal, between mainland Minnesota and Isle Royale.

Sara K. O’Shields, Kamal J.K. Gandhi, Brian T. Sullivan, Holly L. Munro

Southern pine beetle, Dendroctonus frontalis Zimmerman (SPB) is a forest pest that has destroyed millions of acres of pines (Pinus spp.) in the eastern United States. SPB utilizes semiochemicals to initiate mass attacks and overcome host defenses. Likely because of SPB’s close evolutionary history with host pines, specific host volatiles can enhance or inhibit SPB’s response to its aggregation pheromone. One host volatile, 4-allylanisole (4 AA), was demonstrated in the 1990s to be an inhibitor of SPB aggregation, however, in recent field tests 4AA strongly enhanced SPB attraction when paired with commercial lures. It is not yet understood why the results of the earlier and recent studies were different, and thus the biological significance of the contrasting studies is unknown. The goal of our current research is to explore this relationship and determine what factors influence SPB response to 4 AA. We will investigate how proximity of infested trees, trap-type, and presence of other semiochemicals (such as isomers of the SPB pheromone brevicomin and specific host odors) may affect SPB’s responses to 4 AA.

Carrie E. Preston, Scott Salom, Albert Mayfield, Mark Whitmore, Jerome Grant, Tim Tomon, Biff Thompson, John Seiler, Tim Kring

Laricobius nigrinus, a biological control agent of Adelges tsugae, the hemlock woolly adelgid (HWA), has been able to establish populations at a high percentage of release sites throughout the eastern United States. While this specialist predator of HWA sistens nymphs and progrediens eggs impacts the sistens generation, progrediens populations appear to be able to rebound, likely due to the lack of specialist predators for this generation. Recently, Leucopis argenticollis and Leucopis piniperda, predators that are host specific to HWA in the Pacific Northwest, have been proposed as additional biological control agents that could aid in controlling HWA populations in the eastern US. Leucopis spp. have been observed feeding on both generations of HWA, therefore if Leucopis spp. were able to establish in areas where L. nigrinus is present, there could be constant predation pressure on HWA, potentially preventing HWA populations from rebounding. In 2019, four sites with established L. nigrinus populations and high HWA populations were selected for a study to determine the impact of L. nigrinus and Leucopis spp. on HWA populations and to see if their predation would also have an effect on hemlock tree health. Mesh cages were applied on treatment branches with high HWA densities and to control branches, with low HWA densities, to compare the effect of both predators together and separately on the HWA population, to determine mesh cage effects, and to compare hemlock tree health measurements.

William P. Shepherd, Brian T. Sullivan

Commercial devices for releasing forest insect attractants and repellants (used for monitoring pest populations and protecting trees) are commonly stored in a variety of packaging and conditions for extended periods.  The packaging is permeable to varying degrees depending on its composition, thickness, closure type, storage temperature, and the chemical properties of the lure components.  The packaging typically used by manufacturers, as well as practitioners who repackage the lures, consists of various plastics sometimes combined with other materials.  Excessive permeability of the packaging may result in significant cross-contamination among different lures stored in proximity, which can alter the activity of the devices when deployed.  Additionally, escape of chemicals from insufficient packaging may affect lure shelf-life and increase personnel exposure.  We sent a survey to U.S. Forest Service, Forest Health Protection entomologists who regularly use semiochemical lures, asking them to describe semiochemicals used, target insects, release device construction, storage and transport practices, and general observations and concerns.  Responses were used to help select relevant variables that we could test in experiments aimed at formulating recommendations regarding packaging of release devices.  We measured rate of weight loss from lures and packaging both at room temperature and in consumer-grade freezers for (1) single vs. multiple layers of polyethylene bags and (2) various brands and thicknesses of Mylar bags, closed with zip lock-type seals or heat-sealed.  The polyethylene bags were unable to prevent loss of volatiles at room temperature from any of the lures tested, although additional layers of bags delayed or slowed these losses.

 

Jennifer Klutsch, Andy Graves, John Formby, Anna Schoettle, Dan Ryerson

Janet’s looper (Nepytia janetae) recently jumped 200 miles north in NM defoliating 12,000 acres and expanding into Rocky Mountain bristlecone (Pinus aristata) and limber pine (P. flexilis). The addition of another invasive threat on top of white pine blister rust to high-elevation ecosystems can have major consequences for the maintenance of particularly Rocky Mountain bristlecone. While Janet’s looper can cause significant mortality in its native range, factors driving outbreaks are generally not known. Tree chemical defenses are associated with host suitability in other tree-defoliator systems and may be factors determining host suitability in the expanded host range of Janet’s looper. We describe this recent expansion and propose a project to investigate site conditions and tree defenses in the expanded range of Janet’s looper in the Sangre de Cristo Mountains, NM. Stands of Douglas-fir (Pseudotsuga menziesii), one of the historical hosts of Janet’s looper along with 5-needle pines that have been defoliated and not defoliate will be sampled for needle defenses to identify factors associated with potential host suitability. Identifying the defenses that protect these high-elevation trees against this climate change-facilitated native invasive and site conditions are crucial to monitor the forest health in ecosystems already threatened by the invasive white pine blister.

Chelsea N. Miller, Brittany F. Barnes, Sarah Kinz, J. T. Vogt, Kamal J. K. Gandhi

Catastrophic wind disturbances including hurricanes, tornados, and derechos are a major cause of tree mortality in the southeastern U.S. Hurricane Michael, a Category 5 hurricane with wind speeds of 259 kph, made landfall in Florida on 10 October 2018, damaging ~1.13 million hectares of forest and over $1 billion in timber damage. Trees were uprooted, crowns, stems, and boles were snapped; stands were further subjected to prolonged flooding. Additional losses may occur from bark (Curculionidae) and woodboring (Buprestidae, Cerambycidae) beetles that infest wind-disturbed forests. Epidemic outbreaks following catastrophic disturbances can result in the spread of beetles from damaged to healthy trees, further exacerbating losses. Here, we characterize the responses of woodboring beetles to Hurricane Michael in Florida pine-dominated stands. We hypothesize that: 1) beetle populations will increase over the sampling period, and 2) that changes in populations will vary across stands with different levels of damage. To test these hypotheses, we sampled woodboring beetles using baited traps in 2019 and 2020 from 15 stands with low (<25% loss), moderate (25-75%), and high (>75%) damage (5 plots/category). Species thus far include at least 19 species such as Monochamus spp., Acanthocinus spp., Curius dentatus, Xylotrechus sagittatus, and Buprestis lineata. Preliminary results from 2019 indicate support for intermediate disturbance hypothesis, where highest numbers of woodboring beetles were trapped in moderately disturbed forests, particularly in September. Hence, moderately disturbed forests may need to be managed first to minimize future economic losses from beetle outbreaks following this and future wind disturbance events.

6:30 – Adjourn for the day