Jesse A. Pfammatter

Community Composition and Phenology of Native Siricidae (Hymenoptera) Attracted to Semiochemicals in Minnesota

ABSTRACT As a result of the introduction of Sirex noctilio F. into North America, there has been increased interest in the poorly-described native Siricidae communities. To date, few studies have surveyed specifically for Siricidae, and many reports of native siricid populations are byproducts of sampling efforts targeting Coleoptera. We report results from a survey targeted specifically at native and exotic Siricidae in Minnesota. We used Lindgren funnel traps from 2006 to 2008 baited with &agr; /&bgr;-pinene (Sirex lure), ethanol (EtOH), EtOH + &agr;-pinene, or Ips 3-part lures. We captured 704 native Siricidae comprising seven species, of which none were exotic. To our knowledge, this is one of the largest field collections of Siricidae from a single discrete set of localities in existence. Adult Siricidae began flying in June and continued into October each year. The &agr;/&bgr;-pinene lure was most effective, but the EtOH + &agr;-pinene lure was also moderately effective. We compare our data with those from several states and provinces in the Great Lakes Region of North America. Our data provide insight into the community composition of native Siricidae in Minnesota, while concurrently providing evidence that S. noctilio populations have not yet reached this far into the continental United States.

Mites Phoretic on Ips pini (Coleoptera: Curculionidae: Scolytinae) in Wisconsin Red Pine Stands

ABSTRACT We sampled the bark beetle Ips pini (Say) in Wisconsin red pine stands to describe its phoretic mite community. Nearly 78% of adult beetles carried phoretic mites, with an average of 12.78 ± 0.76 individuals and 1.69 ± 0.05 species per beetle. Phoretic mites from flying beetles represented over 13 families. Five species of mites showed relatively close associations, being present on at least 10% of adult beetles. The most common mite species included one from each of the major guilds on bark beetles, the scavenger/fungivore Histiostoma spp. (41.5% of beetles), the egg predator Iponemus confusus (Lindquist) (41.1% of beetles) and the nematode predator Dendrobebps quadrisetus (Berlese) (32.8% of beetles). Beetles in northern Wisconsin had more diverse phoretic mite communities than those in central or southern Wisconsin. Beetles collected late in the season (July-August) carried more individuals and species of mites than those collected early in the season (May-June). The method we used to collect live bark beetles may be useful for other studies requiring fine-scale quantification of symbionts, such as bacteria, fungi, and nematodes.

Evaluation of tree mortality and parasitoid recoveries on the contiguous western invasion front of emerald ash borer

A recent invader to North America, emerald ash borer Agrilus planipennis Fairmaire (Buprestidae), is expanding its western range into new habitats. We examined how site factors affect the emergence and damage caused by this beetle on the western edge of its contiguous population in eastern Wisconsin, U.S.A. We characterized forest structure and quantified signs and symptoms of A. planipennis from 2010 to 2013. We evaluated the potential for establishment of three host‐specific parasitic Hymenoptera, released as biological control agents of A. planipennis. During June to September 2011, we conducted releases of 1500 Oobius agrili Zhang and Huang (Encyrtidae), 1900 Spathius agrili Yang (Braconidae) and 2700 Tetrastichus planipennisi Yang (Eulophidae) at the same location. Signs and symptoms of A. planipennis increased in abundance during the present study. Emergence of A. planipennis was greater in larger diameter trees and in subplots with more ash trees. More epicormic shoots were on the upper halves of trees in subplots with a higher percentage of ash. Fraxinus nigra exhibited a higher incidence of ruptured bark than Fraxinus pennsylvanica. In January 2013, we felled four infested ash trees and censused insect emergence from the entire trees. We recovered 441 A. planipennis, 41 T. planipennisi and no other released parasitoids. These results suggest that, of these three parasitoids, T. planipennisi has the highest likelihood of contributing to biological control in Wisconsin, although ash mortality will proceed rapidly and likely supersede the effects of the parasitoids. The best opportunity for introduced parasitoids to benefit Wisconsin may arise in post‐outbreak, recovering forests.

Foliar bacterial communities of trembling aspen in a common garden.

Microbial associations with plants are widely distributed and are structured by a number of biotic and physical factors. Among biotic factors, the host plant genotype may be integral to these plant-microbe interactions. Trees in the genus Populus have become models for studies in scaling effects of host plant genetics and in plant-microbe interactions. Using 454 pyrosequencing of the 16S rRNA gene, we assessed the foliar bacterial community of 7 genotypes of mature trembling aspen trees (Populus tremuloides Michx.) grown in a common garden. Trees were selected based on prior analyses showing clonal variation in their concentration of chemicals conferring resistance against insect herbivores. At broad taxonomic designations, the bacterial community of trembling aspen was similar across all plant genotypes. At a finer taxonomic scale, the foliage of these trees varied in their community composition, but there was no distinct pattern to colonization or abundance related to plant genotype. The most abundant operational taxonomic units (OTUs) were classified as Ralstonia, Bradyrhizobium, Pseudomonas, and Brucella. These OTUs varied across the common garden, but there was no significant effect of host plant genotype or spatial position on the abundance of these members. Our results suggest that aspen genotype is less important in the structuring of its foliar bacterial communities than are other, poorly understood processes.

Beyond Punnett Squares: Student Word Association and Explanations of Phenotypic Variation through an Integrative Quantitative Genetics Unit Investigating Anthocyanin Inheritance and Expression in Brassica rapa Fast Plants

This study explores shifts in student word association and explanations of phenotypic variation through an integrative quantitative genetics unit using Brassica rapa Fast Plants.

Mountain pine beetle dynamics and reproductive success in post-fire lodgepole and ponderosa pine forests in northeastern Utah

Fire injury can increase tree susceptibility to some bark beetles (Curculionidae, Scolytinae), but whether wildfires can trigger outbreaks of species such as mountain pine beetle (Dendroctonus ponderosae Hopkins) is not well understood. We monitored 1173 lodgepole (Pinus contorta var. latifolia Doug.) and 599 ponderosa (Pinus ponderosa Doug. ex Law) pines for three years post-wildfire in the Uinta Mountains of northeastern Utah in an area with locally endemic mountain pine beetle. We examined how the degree and type of fire injury influenced beetle attacks, brood production, and subsequent tree mortality, and related these to beetle population changes over time. Mountain pine beetle population levels were high the first two post-fire years in lodgepole pine, and then declined. In ponderosa pine, populations declined each year after initial post-fire sampling. Compared to trees with strip or failed attacks, mass attacks occurred on trees with greater fire injury, in both species. Overall, a higher degree of damage to crowns and boles was associated with higher attack rates in ponderosa pines, but additional injury was more likely to decrease attack rates in lodgepole pines. In lodgepole pine, attacks were initially concentrated on fire-injured trees, but during subsequent years beetles attacked substantial numbers of uninjured trees. In ponderosa pine, attacks were primarily on injured trees each year, although these stands were more heavily burned and had few uninjured trees. In total, 46% of all lodgepole and 56% of ponderosa pines underwent some degree of attack. Adult brood emergence within caged bole sections decreased with increasing bole char in lodgepole pine but increased in ponderosa pine, however these relationships did not scale to whole trees. Mountain pine beetle populations in both tree species four years post-fire were substantially lower than the year after fire, and wildfire did not result in population outbreaks.

Morphological and genetic characteristics of Brevipalpus lewisi (Acari: Tenuipalpidae) and comparison with other three Brevipalpus species

ABSTRACT The flat mite, Brevipalpus lewisi McGregor was recently found infesting Metasequoia glyptostroboides Hu & Cheng (Taxodiaceae) in China. In order to accurately differentiate this species from other closely related Brevipalpus species and appropriately apply prevention and control strategies, this study focused on morphological description and identification of adults based on electron microscopy and molecular sequencing of the mitochondrial cytochrome oxidase subunit I gene. Morphological analyses showed significant differences and similarities between B. lewisi (McGregor), Brevipalpus phoenicis (Geijskes), Brevipalpus californicus (Banks) and Brevipalpus obovatus Donnadieu in the number and/or quality of dorsal setae, omega on tarsus II, dorsal cuticular patterns and leg chaetotaxy. Phylogenetic analyses of mitochondrial CO I gene fragment (342 bp) indicated B. lewisi is 86% homologous with the other three species. The genetic distance between B. lewisi host-associated populations of M. glyptostroboides and Vitis vinifera (Vitaceae) is 6.7%, suggesting the existence of genetic divergence between hosts.

Behaviours of phoretic mites (Acari) associated with Ips pini and Ips grandicollis (Coleoptera: Curculionidae) during host-tree colonization

Studies on interactions between bark beetles and phoretic mites have focused largely on dispersal life stages. However, many of these interactions occur within trees, where beetles and mites develop. Within‐tree interactions are potentially important to beetle and mite reproduction, as well as beetle–mite phoretic pairings. We performed experiments aiming to characterize the behaviours of mites associated with Ips pini (Say) and Ips grandicollis (Eichoff) during nondispersal life stages. Mites are highly specific in the location on which they attach to beetles. Detachment from beetles is elicited by cues associated with both beetle vectors and tree hosts. Beetle condition can trigger rapid mite departure and Iponemus confusus Lindquist detach more rapidly from beetles colonizing tissue amended with the host tree secondary compound α‐pinene than in un‐amended tissue. Within‐plant movement by detached mites is elicited by host plant volatiles. In olfactometer assays, Dendrolaelaps quadrisetus (Berlese) preferred volatiles from beetle‐infested phloem over fresh phloem and blank controls. Within host plant tissue, fungal symbionts of beetles provide a resource for mites. Histiogaster arborsignis Berlese fed and reproduced more successfully on Pinus resinosa (Ait) phloem inoculated with the symbiotic fungus Ophiostoma ips (Rumbold) than on phloem with the opportunistic fungus Aspergillus fumigatus or blank controls.

Do Phoretic Mites Influence the Reproductive Success of Ips grandicollis (Coleoptera: Curculionidae)?

ABSTRACT Ips grandicollis (Eichhoff) can be an important pest of plantation trees in the Great Lakes region. Mites commonly occur in phoretic association with this beetle, but little is known about their effects on beetle population dynamics. We assessed the effects of phoretic mites on the reproductive success of I. grandicollis using complementary correlative and manipulative approaches. First, we allowed beetles to colonize Pinus resinosa (Ait) logs from sites across Wisconsin, reared them in a common environment, and related the species identities and abundances of mites with beetle production from each log. We found a positive relationship between I. grandicollis abundance and the presence of five mite species, Histiostoma spp., Dendrolaelaps quadrisetus (Berlese), Iponemus confusus (Lindquist), Trichouropoda australis Hirschmann, and Tarsonemus spp. While the abundance of individual mite species was positively correlated with beetle abundance, assessments of mite community structure did not explain beetle reproduction. Next, we introduced beetles that either had a natural complement of mites or whose mites were mechanically reduced into logs, and compared reproductive success between these beetles. We found no difference in colonization rates or beetle emergence between mite-present and mite-reduced treatments. Collectively, these results suggest a correlative, rather than causal, link between beetle reproductive success and mite incidence and abundances. These mites and beetles likely benefit from mutually suitable environments rather than exerting strong reciprocal impacts. Although mites may have some effects on I. grandicollis reproductive success, they likely play a minimal role compared to factors such as tree quality, beetle predation, and weather.

Evaluating predators and competitors in Wisconsin red pine forests for attraction to mountain pine beetle pheromones for anticipatory biological control.

ABSTRACT Mountain pine beetle, Dendroctonus ponderosae Hopkins (Coleoptera: Curculionidae), is an irruptive tree-killing species native to pine forests of western North America. Two potential pathways of spread to eastern forests have recently been identified. First, warming temperatures have driven range expansion from British Columbia into Albertan jack pine forests that are contiguous with the Great Lakes region. Second, high temperatures and drought have fostered largescale outbreaks within the historical range, creating economic incentives to salvage killed timber by transporting logs to midwestern markets, which risks accidental introduction. We evaluated the extent to which local predators and competitors that exploit bark beetle semiochemicals would respond to D. ponderosae in Wisconsin. We emulated D. ponderosae attack by deploying lures containing synthetic aggregation pheromones with and without host tree compounds and blank control traps in six red pine plantations over 2 yr. Predator populations were high in these stands, as evidenced by catches in positive control traps, baited with pheromones of local bark beetles and were deployed distant from behavioral choice plots. Only one predator, Thanasimus dubius F. (Coleoptera: Cleridae) was attracted to D. ponderosaes aggregation pheromones relative to blank controls, and its attraction was relatively weak. The most common bark beetles attracted to these pheromones were lower stem and root colonizers, which likely would facilitate rather than compete with D. ponderosae. There was some, but weak, attraction of potentially competing Ips species. Other factors that might influence natural enemy impacts on D. ponderosae in midwestern forests, such as phenological synchrony and exploitation of male-produced pheromones, are discussed.