Papers by Rodrigo J Mercader
ABSTRACT Background/Question/Methods Although management programs for invasive species are genera... more 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.
Background/Question/Methods Although management programs for invasive species are generally inten... more 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 ovipo...
American Journal of Enology and Viticulture
In comparison to mature vines, the lack of fruit and lower carbohydrate reserves in vines during ... more In comparison to mature vines, the lack of fruit and lower carbohydrate reserves in vines during establishment create a situation in which the lowest source to sink ratios occur early in the season during rapid vegetative growth. This study compared responses of young Vitis labruscana Bailey var. Niagara vines to injury applied early in the season (bloom) and/or late in the season (veraison). Different sets of plants were injured with hole punchers to imitate foliar injury by leaf-skeletonizing beetles either during bloom, during veraison, or during both phenophases in 2000 and 2001, using a 2 x 2 factorial design. In 2000, vines were injured during bloom by removing 30% of the total leaf area of each fully expanded leaf and during veraison by removing 30% of the subsequently expanded leaves on 1.5 m of each shoot. During 2001, injury during bloom and veraison consisted of removing 20% of the total leaf area of all fully expanded leaves, thereby removing the same percentage of the s...
Specialization, Speciation, and RadiationThe Evolutionary Biology of Herbivorous Insects, 2008
The Canadian Entomologist, 2015
ABSTRACT
Population Ecology, 2011
Management programs for invasive species are often developed at a regional or national level, but... more 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.
Canadian Journal of Forest Research, 2011
The emerald ash borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), is a devastating,... more 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.
The ability to manipulate the spread of an invasive species could potentially be integrated into ... more The ability to manipulate the spread of an invasive species could potentially be integrated into an effective management strategy to delay dispersal to uninfested areas while concentrating the population in an area where suppression activities could be applied. Here we examined the influence of clusters of girdled ash trees on the spread of isolated emerald ash borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), populations in forested areas. Two 16-ha (40 ac) forested sites with lowdensity emerald ash borer populations were selected for this study. Each site was divided into sixty-four 50×50 m cells and complete ash inventories by diameter class were conducted. The amount of ash phloem in each 50×50 m cell was calculated as per and two 4-ha (10 ac) blocks with similar ash density and distribution of total ash phloem were selected per site. At each site, four clusters of girdled ash trees (three trees per cluster; n = 12 total girdled trees per site) were established in one of the randomly selected 4-ha blocks. Beetles were released from infested logs placed between the two blocks. Girdled and nongirdled ash trees (n = 230 trees) were sampled the following winter to assess spread of the populations. Preliminary results indicate that clusters of girdled trees strongly influenced the spread of the low-density emerald ash borer populations at both sites. Overall, emerald ash borer densities were 4.6× and 7.0× greater on the 4 ha with clusters of girdled trees compared to the 4 ha without girdled trees at the two sites, respectively. Girdled trees had densities that were 9.0× and 14.6× higher than emerald ash borer densities on nongirdled trees in the control blocks at the two sites.
—The emerald ash borer (EAB), Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), is a destr... more —The emerald ash borer (EAB), Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), is a destructive invasive pest that threatens North American ash (Fraxinus (Oleaceae)) and inflicts substantial aesthetic, ecological, and economic damage in urban forests and rural woodlands. Understanding adult EAB dispersal and spread of infestations is critical to effectively manage and mitigate its potential impact in North America and elsewhere. Challenges of quantifying short-distance and long-distance movement of adult EAB in the field remain exceptionally difficult. Here we review our current understanding of EAB spread. Research to date suggests natural spread of EAB populations is variable and influenced by local environmental conditions, but limited to only a few km per year. In contrast, long-distance spread resulting from anthropogenic movement of infested ash material, such as nursery trees or firewood, can greatly increase local and regional rate of spread through the formation of satellite populations. Key areas in need of future research are highlighted.
Accurate host plant records are an invaluable tool for anyone conducting research on the Lepidopt... more Accurate host plant records are an invaluable tool for anyone conducting research on the Lepidoptera. Recently, Calhoun (2007a, b) presented excellent reviews of two sets of John Abbot's butterfly life history illustrations. Within this review hickory, Carya sp., is identified as a host of Papilio glaucus (L.) based on Abbot's illustrations and records in the literature. Here we evaluate the potential for hickory, Carya spp., to be used as host plants by the tiger swallowtail butterflies, Papilio glaucus and P. canadensis (R. & J.). Results from larval survival and ovipositional behavior trials indicate that Carya spp. should not be considered hosts for these butterflies.
Bilateral gynandromorphs (half male, half female) have previously been reported in interspecific ... more Bilateral gynandromorphs (half male, half female) have previously been reported in interspecific hybrids. However, we report 6 new nearly perfect bilateral gynandromorphs, three (one Papilio canadensis, and two P. glaucus) of which were collected from areas not near hybrid zones. New interspecific gynandromorphs also are described for apparent P. rutulus x P. multicaudatus hybrids. By using hand-paired in-terspecific hybrids we have generated both diapausing and direct developing (non-diapausing) gynandromorphs. While X (or Z)-linked regulation of diapause in these Papilio may be similar throughout the male and female halves of the individual, the dark melanic color [Y (or W)-linked] is distinctly different. Wing color regulation is differentially implemented on dorsal and ventral surfaces as seen in sexual mosaics described here. The developmental irregularities resulting in bilateral gynandromorphs and sexual mosaics are not solely due to interspecific genetic incompatibilities. However, genetic factors seem to play a major role in their expression. The existence of dark melanic female patchy patterns supports the suggestion that control of the W (=Y)-linked b + melanic gene is both cell-specific and sex-specific in its ability to suppress the BAS enzyme activity that normally shunts dopamine to the yellow papiliochrome pathway. Interspecific hybrids involving dark mothers (with the Y-linked b + gene) mated to P. multicaudatus, P. rutulus, and P. canadensis males (all species lacking the dark morph) have also produced hybrid daughters with " intermediate " suppression of melanism giving a dusty colored appearance (differing from color mosaics). This uniform " dusty " coloration often has been referred to as " cinnamon, " and may reflect incomplete genetic penetrance.
Information on the pattern and rate of spread for invasive wood-and phloem-feeding insects, inclu... more Information on the pattern and rate of spread for invasive wood-and phloem-feeding insects, including the emerald ash borer (EAB) (Agrilus planipennis Fairmaire), is relatively limited, largely because of the difficulty of detecting subcortical insects at low densities. From 2008 to 2011, grids of girdled and subsequently debarked ash (Fraxinus spp.) detection trees were established across a >390 km 2 area encompassing two recently established EAB infestations in Michigan as part of the SLow Ash Mortality (SLAM) Pilot Project. Ash distribution and abundance were inventoried across the project area which included public and private forestland, a state park, and street trees in a small municipality. Spread rates of EAB from 2008 to 2011, based on larval presence in girdled detection trees, were estimated to be 1.2– 1.7 km yr À1 in the larger, presumably older, infestation and 0.4–0.7 km yr À1 in the smaller infestation; suggesting a slower spread rate during the initial stages of population establishment. From 2009 to 2011, a total of 587 ash trees in the project area were trunk-injected with a highly effective, systemic emamectin benzoate insecticide. Potential effects of girdled ash trees and the systemic insecticide treatment on EAB spread were evaluated using a simulation model and a simple descriptive model of observed spread. Not surprisingly, density of trees treated with the insecticide was too low to exert a detectable effect on EAB spread. However, while the density of girdled trees was also relatively low, model results indicated a reduced spread of EAB out of areas containing girdled trees.
Emerald ash borer, Agrilus planipennis Fairmaire, has become the most destructive forest insect t... more Emerald ash borer, Agrilus planipennis Fairmaire, has become the most destructive forest insect to invade North America. Unfortunately, tactics to manage A. planipennis are limited and difficult to evaluate, primarily because of the difficulty of detecting and delineating new infestations. Here we use data from a unique resource, the SL.ow A.sh M.ortality (SLAM) pilot project, to assess whether treating a small proportion of trees with a highly effective systemic insecticide or girdling ash (Fraxinus spp.) trees to serve as A. planipennis population sinks can result in discernable effects on A. planipennis population growth or ash mortality. Components of the SLAM pilot project included an extensive inventory of ash abundance across a heterogenous area encompassing >390 km 2 , treatment of 587 ash trees with a highly effective systemic insecticide, and girdling 2658 ash trees from 2009 to 2012. Fixed radius plots were established to monitor the condition of >1000 untreated ash trees throughout the area from 2010 to 2012. While only a very small proportion of ash trees in the project area were either treated with insecticide or girdled, both tactics led to detectable reductions of A. planipennis densities and protected ash trees in areas surrounding the treatments. The number of trees treated with the systemic insecticide reduced larval abundance in subsequent years. In contrast, the area of phloem in the insecticide-treated trees had no discernable effect on A. planipennis population growth, indicating that the number of treated trees was more important than the size of treated trees. Significant interactions among girdled trees, larval density, and the local abundance of ash phloem indicate girdling trees has a positive, but complex potential as a management tactic.
Emerald ash borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), a phloem-feeding pest... more Emerald ash borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), a phloem-feeding pest of ash (Fraxinus spp.) trees native to Asia, was Þrst 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 efÞciency 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 threefold 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.
The response of potted fruitless Vitis labrusca (L.) var. Niagara grapevines to early and late se... more The response of potted fruitless Vitis labrusca (L.) var. Niagara grapevines to early and late season mechanical and insect defoliation was recorded. Twenty percent of the leaf area was removed with a hole puncher to simulate insect injury early and/or late in the season. Measurements of growth, singleleaf photosynthesis, and whole-vine photosynthesis indicated a higher tolerance to foliar injury late in the season than early in the season. Because defoliation was made on a percentage basis, the results were due to the stage of vine development at the time of damage rather than to the amount of leaf area injured. In a second experiment, measurements of vines injured early in the season by the rose chafer, Macrodactylus subspinosus (F.), and late in the season by the Japanese beetle, Popillia japonica (N.), indicated qualitatively similar impacts of beetle feeding on growth parameters compared to vines injured mechanically. Feeding injury by the Japanese beetle had a negative impact on whole-vine carbon assimilation not observed in mechanically injured vines. A final experiment comparing the effect of mechanical and beetle injury early and late in the season on single leaves indicated no significant differences between rose chafer and mechanical injury early in the season. However, 17 days after injury, leaves injured late in the season by the Japanese beetle had lower carbon assimilation rates than mechanically injured leaves. This response was detected on both injured and uninjured sections of injured leaves.
The response of potted fruitless Vitis labrusca (L.) var. Niagara grapevines to early and late se... more The response of potted fruitless Vitis labrusca (L.) var. Niagara grapevines to early and late season mechanical and insect defoliation was recorded. Twenty percent of the leaf area was removed with a hole puncher to simulate insect injury early and/or late in the season. Measurements of growth, singleleaf photosynthesis, and whole-vine photosynthesis indicated a higher tolerance to foliar injury late in the season than early in the season. Because defoliation was made on a percentage basis, the results were due to the stage of vine development at the time of damage rather than to the amount of leaf area injured. In a second experiment, measurements of vines injured early in the season by the rose chafer, Macrodactylus subspinosus (F.), and late in the season by the Japanese beetle, Popillia japonica (N.), indicated qualitatively similar impacts of beetle feeding on growth parameters compared to vines injured mechanically. Feeding injury by the Japanese beetle had a negative impact on whole-vine carbon assimilation not observed in mechanically injured vines. A final experiment comparing the effect of mechanical and beetle injury early and late in the season on single leaves indicated no significant differences between rose chafer and mechanical injury early in the season. However, 17 days after injury, leaves injured late in the season by the Japanese beetle had lower carbon assimilation rates than mechanically injured leaves. This response was detected on both injured and uninjured sections of injured leaves.
Responses of young non-fruiting grapevines, Vitis labrusca (L.) var. 'Niagara', to defoli... more Responses of young non-fruiting grapevines, Vitis labrusca (L.) var. 'Niagara', to defoliation were examined at two stages of vine growth when beetles typically infest vineyards. In the first experiment, vines were caged and sub- jected to two weeks of feeding by 0, 10, 20, or 40 adult Macrodactylus subspinosus Fabricius (Scarabaeidae: Macrodactylini) during bloom, or to the same range of
Oecologia, 2009
Climate warming has lead to increased genetic introgression across a narrow hybrid zone separatin... more Climate warming has lead to increased genetic introgression across a narrow hybrid zone separating the eastern and Canadian tiger swallowtails (Papilio glaucus and Papilio canadensis). This situation has led to the formation of an allochronically separated hybrid population with a delayed emerging phenotype or ''late flight''. Here, we assess how the recombination of the parental genomes that lead to this phenotype may have facilitated another major ecological shift, host-use divergence. We first contrast the ovipositional profiles of the late flight population to that of the parental species P. glaucus and P. canadensis. Subsequently we contrast the larval survival and growth of the late flight, a P. canadensis and a P. glaucus population, and a population from the northern edge of the hybrid zone on five hosts. Our results indicate that the ovipositional preference of this hybrid swarm is identical to that of the introgressing parental species, P. glaucus. Due to the absence of the preferred hosts of P. glaucus (Liriodendron tulipifera L. and Ptelea trifoliata L.) where the late flight occurs, this ovipositional pattern implies a functional specialization onto a secondary host of both parental species, Fraxinus americana L. In contrast, the larval host-use abilities represent a mixture of P. glaucus and P. canadensis, indicating divergence in larval host-use abilities has not taken place. However, high genetic variability (genetic coefficient of variation) is present for growth on F. americana in the late flight hybrid swarm and tradeoffs for larval performance on the preferred hosts of the parental species are evident; indicating a strong potential for future specialization in larval host-use abilities. This current scenario represents an instance where a shift in a major ecological trait, host use, is likely occurring as a byproduct of a shift in an unrelated trait (delayed emergence) leading to partial reproductive isolation.
Journal of Applied Entomology, 2004
Bioassays were conducted to compare the residual toxicity and leaf protection activity of convent... more Bioassays were conducted to compare the residual toxicity and leaf protection activity of conventional broad-spectrum and reduced-risk insecticides against the rose chafer, Macrodactylus subspinosus. Insecticides were applied to a Vitis labrusca (F.) vineyard and residues were aged for 1, 3 or 7 days before leaves were collected and exposed to beetles in no-choice tests. Azinphosmethyl caused rapid knockdown and mortality for up to 1 week after application, with 1-day-old residues providing 95.6% protection against feeding, dropping to 51.6% when residues were a week old. Fenpropathrin caused mortality and knockdown after beetles had been exposed to fresh residues for 72 h. Although these effects diminished as residues aged, this compound provided the best protection of leaves against beetle feeding, with 77.9% reduction in feeding compared with the control after 7 days of aging in the vineyard. Of the reduced-risk insecticides, imidacloprid caused the greatest initial mortality and knockdown of beetles, providing protection against feeding that was equivalent to azinphosmethyl. Exposure to azadirachtin caused a low level of knockdown and mortality when residues were 1-and 3-days old. Protection against feeding was also low, lasting for only 3 days. Beetles were minimally affected by capsaicin and kaolin, with mortality and knockdown seen only when beetles were exposed to 1-day-old residues for 72 h. Foliage protection from these compounds was minimal, with between 10 and 15% reduction in feeding injury. Results are discussed in relation to development of semi-field bioassay methods for evaluating reduced-risk insecticides, and the management of M. subspinosus within grape pest management programs.
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Papers by Rodrigo J Mercader