Nathan W. Siegert

Michigan State University, East Lansing, Michigan, United States

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Publications (33)33.67 Total impact

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    ABSTRACT: AimEmerald ash borer Agrilus planipennis was identified in 2002 as the cause of extensive ash (Fraxinus spp.) decline and mortality in Detroit, Michigan, and has since killed millions of ash trees in the US and Canada. When discovered, it was not clear how long it had been present or at what location the invading colony started. We used dendrochronological methods to document the onset and progression of ash mortality and the spatio-temporal dynamics of the invasion. Reconstructing the progression of ash mortality serves as a proxy to draw inferences about the colonization and spread of emerald ash borer in North America.LocationSoutheastern Michigan, USA.Methods We collected increment cores from dead, declining or non-symptomatic ash trees on a systematic 4.8 × 4.8 or 2.4 × 2.4 km grid in 2004–2006. Geo-referenced samples were cross-dated to determine the earliest date emerald ash borer-killed trees in each location. Interpolated dates of ash mortality were analysed to determine rates and patterns of emerald ash borer spread across the 1.5 million ha study area.ResultsWe identified a location in southeastern Michigan where ash trees were killed by emerald ash borer as early as 1997. Rates of ash mortality subsequently progressed at 3.84 km year−1 from 1998 to 2001 and then increased to 12.97 km year−1 from 2001 to 2003 as satellite colonies coalesced with the primary infestation. From 1998 to 2003, new satellites formed at a rate of 7.4 per year, with average jump distances of 24.5 km.Main conclusionsEmerald ash borer was likely established in southeastern Michigan by at least the early to mid-1990s. Anthropogenic-aided stratified dispersal and the coalescence of satellite colonies with the primary population resulted in biphasic range expansion, rapidly expanding the footprint of the invasion. Our reconstruction of the emerald ash borer invasion demonstrates this invaders’ remarkable capacity for population growth and spread.
    Diversity and Distributions 04/2014; 20(7). DOI:10.1111/ddi.12212 · 6.12 Impact Factor
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    ABSTRACT: Black ash (Fraxinus nigra Marshall) trees are an important cultural resource and provide the wood used for traditional contemporary basketry by numerous Native American and First Nation tribes in the U.S.A. and Canada. The invasion and subsequent spread of emerald ash borer Agrilus planipennis Fairmaire (Coleoptera: Buprestidae) threatens the ash resource in North America and the basketry tradition. Submersion of infested ash logs has been proposed as a potential tactic to control A. planipennis emergence, although the duration of submergence required to prevent adult beetle emergence is unknown.We assessed the survivorship of A. planipennis prepupae through adult beetle emergence in green ash (F. pennsylvanica Marshall) bolts submerged at weekly intervals for up to 6 weeks and in black ash bolts submerged at 4-week intervals for up to 24 weeks. The moisture content of sapwood at depths where prepupal chambers are commonly found was quantified in the black ash bolts after 0, 12 and 24 weeks of submergence.Mortality of A. planipennis from prepupa to adult was low (5.7 ± 2.3%) for the first 6 weeks of submersion but rapidly increased to 100% in green ash and black ash bolts submerged for 8 weeks or longer. In black ash, the outer 1.3 cm of wood became highly saturated after submersion for 12 weeks (81.0 ± 4.5%) and moisture increased only slightly after 24 weeks (83.9 ± 2.8%).The results obtained in the present study indicate that A. planipennis prepupae in green ash and black ash bolts can survive complete submersion for extended periods of time (i.e. at least 6 weeks) and successfully emerge as adults afterwards. Logs submerged for at least 8 weeks, however, produced no live A. planipennis beetles, indicating that submersion represents an efficacious control option.
    Agricultural and Forest Entomology 03/2014; 16(3). DOI:10.1111/afe.12057 · 1.56 Impact Factor
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    ABSTRACT: Asian longhorned beetle (ALB), Anoplophora glabripennis (Motschulsky), is an invasive insect that has successfully established multiple times in North America. To investigate host colonization and reproductive success (exit holes/eggs), two ALB infested forest stands were sampled in central Massachusetts, USA. Infested Acer platanoides L., Acer rubrum L., and Acer saccharum Marsh. were felled, bucked into 1 m sections and dissected to determine indications of ALB infestations, such as presence of life stages or signs of damage on trees. ALB damage was also aged on a subset of trees to determine the earliest attacks on the three Acer species. In one stand, ALB oviposition was significantly higher on the native A. rubrum and A. saccharum than the exotic A. platanoides. In the second stand, ALB oviposition was significantly higher and cumulative reproductive success was higher on A. rubrum than A. platanoides or A. saccharum. An A. saccharum had the earliest signs of attack that occurred in 2006. Acer rubrum (2007) and A. platanoides (2010) were colonized shortly thereafter. Overall, ALB was more successful in A. rubrum, where adults emerged from 53% and 64% of trees in each stand, compared to A. platanoides (11% and 18%) or A. saccharum (14% and 9%).
    01/2014; 5(1):105-119. DOI:10.3390/insects5010105
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    ABSTRACT: The fungal entomopathogen Entomophaga maimaiga has provided important biological control of gypsy moth, Lymantria dispar (L.), since the first epizootics occurred in the northeastern United States in 1989. Epizootics are initiated by germination of soil-borne resting spores, which are highly sensitive to spring temperature and moisture. We compared gypsy moth infection by E. maimaiga in 33 oak stands in Michigan with infection under optimal laboratory conditions from 1999 to 2001 to assess differences between potential and realized efficacy of E. maimaiga. Field bioassays were conducted by exposing laboratory-reared, fourth-instar gypsy moth to soil at the base of oak trees for 4 d. Additional larvae were similarly exposed to soil collected from the field plots in laboratory bioassays with temperature, humidity, and moisture levels optimal for fungal germination. Overall E. maimaiga infection ranged from means of 3.2-29.8% in the field compared with 20.9-59.7% in the laboratory during three field seasons. Resting spore density in soil and gypsy moth egg mass density were significant predictors of field infections in two of the 3 yr, whereas resting spore density was a significant predictor of laboratory infections each year. Other variables that significantly predicted laboratory infections in one of the 3 yr included egg mass density, canopy cover, and soil pH. In laboratory bioassays, soil pH and E. maimaiga resting spore density were positively associated with increasing E. maimaiga infection rates of gypsy moth larvae.
    Environmental Entomology 10/2012; 41(5):1115-24. DOI:10.1603/EN12137 · 1.42 Impact Factor
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    ABSTRACT: Emerald ash borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), a phloem-feeding pest of ash (Fraxinus spp.) trees native to Asia, was first discovered in North America in 2002. Since then, A. planipennis has been found in 15 states and two Canadian provinces and has killed tens of millions of ash trees. Understanding the probability of detecting and accurately delineating low density populations of A. planipennis is a key component of effective management strategies. Here we approach this issue by 1) quantifying the efficiency of sampling nongirdled ash trees to detect new infestations of A. planipennis under varying population densities and 2) evaluating the likelihood of accurately determining the localized spread of discrete A. planipennis infestations. To estimate the probability a sampled tree would be detected as infested across a gradient of A. planipennis densities, we used A. planipennis larval density estimates collected during intensive surveys conducted in three recently infested sites with known origins. Results indicated the probability of detecting low density populations by sampling nongirdled trees was very low, even when detection tools were assumed to have three-fold higher detection probabilities than nongirdled trees. Using these results and an A. planipennis spread model, we explored the expected accuracy with which the spatial extent of an A. planipennis population could be determined. Model simulations indicated a poor ability to delineate the extent of the distribution of localized A. planipennis populations, particularly when a small proportion of the population was assumed to have a higher propensity for dispersal.
    Journal of Economic Entomology 02/2012; 105(1):272-81. DOI:10.1603/EC11172 · 1.61 Impact Factor
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    ABSTRACT: Effective methods for early detection of newly established, low density emerald ash borer (Agrilus planipennis Fairmaire) infestations are critically needed in North America. We assessed adult A. planipennis captures on four types of traps in a 16-ha site in central Michigan. The site was divided into 16 blocks, each comprised of four 50- by 50-m cells. Green ash trees (Fraxinus pennsylvanica Marshall) were inventoried by diameter class and ash phloem area was estimated for each cell. One trap type was randomly assigned to each cell in each block. Because initial sampling showed that A. planipennis density was extremely low, infested ash logs were introduced into the center of the site. In total, 87 beetles were captured during the summer. Purple double-decker traps baited with a blend of ash leaf volatiles, Manuka oil, and ethanol captured 65% of all A. planipennis beetles. Similarly baited, green double-decker traps captured 18% of the beetles, whereas sticky bands on girdled trees captured 11% of the beetles. Purple traps baited with Manuka oil and suspended in the canopies of live ash trees captured only 5% of the beetles. At least one beetle was captured on 81% of the purple double-decker traps, 56% of the green double-decker traps, 42% of sticky bands, and 25% of the canopy traps. Abundance of ash phloem near traps had no effect on captures and trap location and sun exposure had only weak effects on captures. Twelve girdled and 29 nongirdled trees were felled and sampled in winter. Current-year larvae were present in 100% of the girdled trees and 72% of the nongirdled trees, but larval density was five times higher on girdled than nongirdled trees.
    Environmental Entomology 10/2011; 40(5):1239-52. DOI:10.1603/EN11099 · 1.42 Impact Factor
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    ABSTRACT: The invasion spread of the emerald ash borer (Agrilus planipennis Fairmaire) (Coleoptera: Buprestidae) is characterized by the formation of satellite populations that expand and coalesce with the continuously invading population front. As of January 2010, satellite infestations have been detected in 13 states and two Canadian provinces. Understanding how newly established satellite populations may affect economic costs can help program managers to justify and design prevention and control strategies. We estimate the economic costs caused by EAB for the 10-yr period from 2010 to 2020 for scenarios of fewer EAB satellite populations than those found from 2005 to 2010 and slower expansion of satellite populations found in 2009. We measure the projected discounted cost of treatment, removal, and replacement of ash trees (Fraxinus spp.) growing in managed landscapes in U.S. communities. Estimated costs for the base scenario with the full complement of satellites in 2005-2010 and no program to mitigate spread is $12.5 billion. Fewer EAB satellites from 2005 to 2010 delay economic costs of $1.0 to 7.4 billion. Slower expansion of 2009 satellite populations delays economic costs of $0.1 to 0.7 billion. Satellite populations that are both distant from the core EAB infestation and close to large urban areas caused more economic costs in our simulations than did other satellites. Our estimates of delayed economic costs suggest that spending on activities that prevent establishment of new satellite EAB populations or slow expansion of existing populations can be cost-effective and that continued research on the cost and effectiveness of prevention and control activities is warranted.
    Journal of Environmental Management 09/2011; 92(9):2170-81. DOI:10.1016/j.jenvman.2011.03.043 · 3.06 Impact Factor
  • Nathan W Siegert, Deborah G McCullough
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    ABSTRACT: We investigated host preference of the pine shoot beetle, Tomicus piniperda (L.) (Coleoptera: Scolytidae), in a large-scale field study in 1997 and 1998. This Eurasian pest, first discovered in North America in 1992, is capable of developing and shoot-feeding in many North American pines. We hypothesized, however, that T. piniperda would preferentially colonize Scots pine (Pinus sylvestris L.), a Eurasian species, more frequently than North American red pine (Pinus resinosa Ait.) and jack pine (Pinus banksiana Lamb.). We placed freshly cut Scots, red, and jack pine logs in Scots, red, and jack pine forest stands each year in southwestern Michigan, where T. piniperda populations have been established for several years, and in central and northern Michigan, where T. piniperda populations were low to rare. Following T. piniperda progeny emergence, logs were retrieved and debarked and T. piniperda attack density was determined for each log. Tomicus piniperda colonized 80%–90% of the pine logs in the southwestern Michigan stands compared with 2%–19% of logs in the central Michigan stands. No logs in the northern Michigan stands were colonized by T. piniperda in either year. In the southwestern pine stands, T. piniperda attack densities were significantly greater on Scots pine logs than on jack and red pine logs, regardless of stand species.
    Canadian Journal of Forest Research 02/2011; 33(11):2238-2244. DOI:10.1139/x03-156 · 1.66 Impact Factor
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    ABSTRACT: The emerald ash borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), is a devastating, invasive insect pest of ash trees, Fraxinus spp., in North America. Using a simulation model, we evaluated three potential management options to slow the spread of A. planipennis in discrete outlier sites: (i) removing ash trees to reduce available host phloem resource, (ii) girdling ash trees to attract ovipositing female beetles and destroying the trees before larvae complete development, and (iii) applying a highly effective systemic insecticide. Simulations indicate that systemic insecticide applications provided the greatest reduction in the radial spread of A. planipennis. In simulations in which management options were applied only within a 300 m radius from the origin of the infestation, insecticide applications reduced the radial spread by 30% and larval consumption of ash phloem by 40% beyond the treated area. In contrast, girdling ash trees reduced the radial spread by 15% and larval consumption of ash phloem by 20% beyond the treated area. Both of these management options significantly reduced the spread of A. planipennis when treatments were applied 1 to 4 years after infestations were initiated. Reducing ash phloem by removing ash trees decreased population size within treated areas but did not reduce the radial spread, population size, or larval consumption of ash phloem beyond treated areas.
    Canadian Journal of Forest Research 02/2011; 41(2-10.1139/X10-201):254-264. DOI:10.1139/X10-201 · 1.66 Impact Factor
  • Entomological Society of America Annual Meeting 2010; 12/2010
  • Entomological Society of America Annual Meeting 2010; 12/2010
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    ABSTRACT: Emerald ash borer, Agrilus planipennis (Fairmaire) (Coleoptera: Buprestidae), a phloem-feeding beetle native to Asia, has become one of the most destructive forest pests in North America. Since it was first identified in 2002 in southeast Michigan and Windsor, Ontario, dozens of isolated A. planipennis populations have been discovered throughout Michigan and Ontario, and in 12 other states and the province of Quebec. We assessed realized A. planipennis dispersal at two discrete outlier sites that originated 1 yr and 3 yr earlier from infested nursery trees. We systematically sampled ash trees within an 800 m radius of the origin of each infestation to locate galleries constructed by the progeny of dispersing A. planipennis adults. Our sampling identified eight trees at the 1 yr site infested with a mean +/- SE of 11.6 +/- 8.4 A. planipennis larvae and 12 trees at the 3 yr site with 25.8 +/- 11.1 larvae per meter squared. Dendroentomological analysis indicated that A. planipennis populations were predominantly undergoing a 2 yr (semivoltine) life cycle at both sites. Colonized trees were found out to 638 and 540 m from the epicenters at the 1 yr and 3 yr sites, respectively. Logistic regression was used to determine whether the likelihood of A. planipennis colonization was affected by wind direction, ash phloem abundance, distance from the epicenter, or land-use type (i.e., wooded, residential, agricultural, or urban). Results show that the probability of A. planipennis colonization was significantly affected by ash phloem abundance and decreased with distance from the epicenter.
    Environmental Entomology 04/2010; 39(2):253-65. DOI:10.1603/EN09029 · 1.42 Impact Factor
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    ABSTRACT: Management programs for invasive species are often developed at a regional or national level, but physical intervention generally takes place over relatively small areas occupied by newly founded, isolated populations. The ability to predict how local habitat variation affects the expansion of such newly founded populations is essential for efficiently targeting resources to slow the spread of an invasive species. We assembled a coupled map lattice model that simulates the local spread of newly founded colonies of the emerald ash borer (Agrilus planipennis Fairmaire), a devastating forest insect pest of ash (Fraxinus spp.) trees. Using this model, we investigated the spread of A. planipennis in environments with different Fraxinus spp. distributions, and explored the consequences of ovipositional foraging behavior on the local spread of A. planipennis. Simulations indicate that increased larval density, resulting from lower host tree density or higher initial population sizes, can increase the spread rate during the first few years after colonization by increasing a density-dependent developmental rate and via host resource depletion. Both the radial spread rate and population size were greatly influenced by ovipositional foraging behavior. Two known behaviors of ovipositing A. planipennis females, attraction towards areas with high ash tree density and attraction to stressed trees, had opposing effects on spread. Results from this model illustrate the significant influence of resource distribution and foraging behavior on localized spread, and the importance of these factors when formulating strategies to monitor and manage invasive pests. KeywordsBiological invasions–Buprestidae–Dispersal–Forest insect pests–Invasive species–Ovipositional behavior
    Population Ecology 04/2010; 53(2):271-285. DOI:10.1007/s10144-010-0233-6 · 1.70 Impact Factor
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    ABSTRACT: Emerald ash borer (Agrilus planipennis Fairmaire), a phloem-feeding beetle native to Asia, was discovered near Detroit, Michigan and Windsor, Ontario in 2002. As of March 2009, isolated populations of emerald ash borer (EAB) have been detected in nine additional states and Quebec. EAB is a highly invasive forest pest that has the potential to spread and kill native ash trees (Fraxinus sp.) throughout the United States. We estimate the discounted cost of ash treatment, removal, and replacement on developed land within communities in a 25-state study area centered on Detroit using simulations of EAB spread and infestation over the next decade (2009-2019). An estimated 38Â million ash trees occur on this land base. The simulations predict an expanding EAB infestation that will likely encompass most of the 25 states and warrant treatment, removal, and replacement of more than 17Â million ash trees with mean discounted cost of $10.7Â billion. Expanding the land base to include developed land outside, as well as inside, communities nearly double the estimates of the number of ash trees treated or removed and replaced, and the associated cost. The estimates of discounted cost suggest that a substantial investment might be efficiently spent to slow the expansion of isolated EAB infestations and postpone the ultimate costs of ash treatment, removal, and replacement.
    Ecological Economics 01/2010; 69(3):569-578. DOI:10.1016/j.ecolecon.2009.09.004 · 2.52 Impact Factor
  • Entomological Society of America Annual Meeting 2009; 12/2009
  • Entomological Society of America Annual Meeting 2009; 12/2009
  • Entomological Society of America Annual Meeting 2009; 12/2009
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    ABSTRACT: 1 Emerald ash borer Agrilus planipennis Fairmaire (Coleoptera: Buprestidae) is an invasive forest insect pest threatening more than 8 billion ash (Fraxinus spp.) trees in North America. Development of effective survey methods and strategies to slow the spread of A. planipennis requires an understanding of dispersal, particularly in recently established satellite populations. 2 We assessed the dispersal of A. planipennis beetles over a single generation at two sites by intensively sampling ash trees at known distances from infested ash logs, the point source of the infestations. Larval density was recorded from more than 100 trees at each site. 3 Density of A. planipennis larvae by distance for one site was fit to the Ricker function, inverse power function, and the negative exponential function using a maximum likelihood approach. The prediction of the best model, a negative exponential function, was compared with the results from both sites. 4 The present study demonstrates that larval densities rapidly declined with distance, and that most larvae (88.9 and 90.3%) were on trees within 100 m of the emergence point of the adults at each site. The larval distribution pattern observed at both sites was adequately described by the negative exponential function.
    Agricultural and Forest Entomology 11/2009; 11:421-424. DOI:10.1111/j.1461-9563.2009.00451.x · 1.56 Impact Factor
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    ABSTRACT: The fungal pathogen Entomophaga maimaiga Humber, Shimazu et Soper has become an important biocontrol for gypsy moth (Lymantria dispar (L.)) in the northeastern United States and is commonly introduced into new areas with established gypsy moth populations. Germination of the fungus is dependent on spring temperature and moisture, but specific conditions associated with epizootics have not been determined. Whether E. maimaiga will be as effective in other regions that experience different weather conditions is not yet known. We examined similarity of weather conditions associated with 16 documented E. maimaiga epizootics with conditions at 1351 North American locations using the climate-matching software CLIMEX. Based on CLIMEX’s overall index of climatic similarity, long-term annual climatic patterns across much of the eastern United States were 60%–80% similar to the conditions associated with epizootics. Monthly weather records from 1971 to 2000 in nine North Central states were examined to compare precipitation and temperature with conditions observed during epizootics. Based on climatic averages identified with the documented epizootics, temperature and precipitation conditions in Illinois, Indiana, Iowa, Kentucky, Missouri, and Ohio were more conducive for epizootics than conditions in Minnesota, Wisconsin, and Michigan, which were likely to support E. maimaiga epizootics in fewer than 6 of the 30 years considered.
    Canadian Journal of Forest Research 10/2009; 39(10):1958-1970. DOI:10.1139/X09-117 · 1.66 Impact Factor
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    ABSTRACT: Background/Question/Methods Although management programs for invasive species are generally intended at a regional or national level, physical intervention generally takes place in smaller management units. The ability to predict how local habitat variation will affect the dispersal of invasive species is an essential tool for the efficient targeting of resources to manage the spread of an invasive species. Here we describe a coupled map lattice model for the local spread of a recently discovered devastating pest of Fraxinus spp. in North America, the Emerald Ash Borer, Agrilus planipennis. The model is based on field estimates of population growth, dispersal, larval consumption rates, and developmental thresholds and is designed to be able to incorporate site specific spatially explicit resource variation. We present the functionality of this model by using it to investigate the influence of resource distribution on the spread of A. planipennis, and the relative importance of oviposition site foraging behavior assumptions on the local spread of A. planipennis. Results/Conclusions Simulations performed in environments varying in the spatial distribution of resources indicated that the local spread was strongly dependent on both resource distribution and quantity. In particular, a decrease in resource quantity lead to a small increase in the spread rate, while greater resource heterogeneity can lead to either an increase or a decrease in the spread rate. Simulations also indicated that resource consumption rate and a density dependent variation in developmental rate (1 or 2 year larval stages) exhibited by A. planipennis are likely to be key components of this species spread rate. Differences in resource distribution, in environments containing identical quantities of resources, also had a strong impact on the local population size. In addition, the simulations indicated that foraging behavior assumptions, built on top of dispersal estimates from homogeneous sites, can lead to large differences in both the spread rate and population sizes. Together these results illustrate 1) the need to incorporate habitat heterogeneity when considering potential management options, and 2) the importance of considering behavior in the population dynamics of invasive insect species.
    94th ESA Annual Convention 2009; 08/2009