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Intraspecific genetic variation underpins many evolutionary processes and phenomena. For species considered pests, the dynamics of how genetic variation is distributed geographically take on a greater importance, because they can impact pest-management strategies directly. This is particularly true when management strategies are genetic in nature, such as population manipulation via RNA interference (RNAi; a naturally occurring antiviral response that disrupts translation of messenger RNAs into proteins to silence genes). Using RNAi for gene silencing is highly species specific; however, the efficacy of this approach in geographically distinct populations of widespread pest species has not been evaluated comprehensively. Here, we present a preliminary study evaluating differential susceptibility of geographically disparate populations of southern pine beetle, Dendroctonus frontalis , to RNAi. Although the efficacy of RNAi has been demonstrated in localized populations, D. frontalis has a broad distribution across North and Central America and is expanding its range owing to climate change. We observe differences in response between and within geographically distinct populations from its core range and recently expanded range. Our findings have broad implications for the use of RNAi as a management tool in widely distributed species and highlight the need for a deeper understanding of intraspecific genetic variation in this species and others. [ABSTRACT FROM AUTHOR]

Laurel wilt disease (LWD) is a lethal vascular wilt caused by an exotic ambrosia beetle–fungal complex, the redbay ambrosia beetle, Xyleborus glabratus Eichhoff, and its nutritional symbiont, Harringtonia lauricola (Harr., Fraedrich & Aghayeva) de Beer & Procter. LWD is responsible for the widespread mortality of redbay, Persea borbonia (L.) Spreng., devastating coastal forests in the southeast United States. More recently, LWD is causing mortality of understory sassafras, Sassafras albidum (Nutt.) Nees, in deciduous forests in Kentucky, USA; the biology, epidemiology, and long-term impacts of LWD in deciduous forests are unclear. All North American lauraceous species evaluated have shown susceptibility, and numerous additional ambrosia beetles have demonstrated vector potential, but no studies to date have assessed the presence of H. lauricola in other insects associated with LWD-infected sassafras. We sampled infected sassafras from the leading edge of the LWD range and collected insect associates to evaluate phoretic and internal presence of H. lauricola. We recorded 118 individuals of 38 morphospecies emerging; most were Coleoptera. Of the 48 specimens evaluated for H. lauricola, none tested positive for phoretic presence, but internal presence was evident in the granulate ambrosia beetle, Xylosandrus crassiusculus Motschulsky, and in a hidden snout weevil, Apteromechus ferratus Say. This is the first report of H. lauricola associated with a non-ambrosia beetle and expands our understanding of the vector potential of additional insect species while confirming the role of the granulate ambrosia beetle. These findings contribute to our understanding of LWD epidemiology in sassafras hosts from more northerly latitudes. [ABSTRACT FROM AUTHOR]

Agrilus planipennis Fainnaire (Coleoptera: Buprestidae) is a wood-boring pest of Asian origin that has caused widespread mortality of ash, Fraxinus spp., in North America since its accidental introduction in the 1990s. Studies conducted at the epicenter of the infestation in the Great Lakes region have discovered several species of native parasitoids capable of utilizing A. planipennis-, however, little is known of how these natural enemy complexes vary across the shifting forest types and habitats encompassed by the expanding infestation. We characterized the assemblage of native natural enemies being recruited to A. planipennis at five sites in north-central Kentucky, where infestations have been documented since 2009. Through destructive sampling, dissection, and rearing of infested ash material, 12 native parasitoid morpho-species were found being recruited to A. planipennis, nine of which have not been reported previously. Catogenus rufus (F.) (Coleopter: Passandridae), Phasgonophora sulcata Westwood (Hymenoptera: Chalcididae), and Leluthia asgtigma (Ashmead) (Hymenoptera: Braconidae) have been discovered utilizing A. planipennis in more northerly infested regions of North America and were present in our study. Native hymenopteran parasitoid responses to A. planipennis presence and associated ash decline, measured using visual assessments of canopy decline, revealed a positive correlation between parasitoid guilds and ash decline. [ABSTRACT FROM AUTHOR]

Fecundity is a key factor in modulating population growth rate, and is of particular significance when considering the invasiveness of introduced species. In insects, fecundity is affected by body size, age, and nutrition. We investigated the potential fecundity of the invasive Asian chestnut gall wasp Dryocosmus kuriphilus Yasumatsu (Hymenoptera: Cynipidae), an introduced parthenogenetic gall former of Asian origin and a global pest of chestnut ( Castanea spp.), to better understand its invasiveness. We compared ovarian, egg, and body metrics of adult wasps of different age. We evaluated insect weight, body length, mesosomal and metasomal lengths and widths, hind femur length, number of eggs, and size of eggs in wasps from four age cohorts. Adult weight and metasomal width were positively correlated with number of eggs. Egg load decreased with wasp age, and egg size initially increased before decreasing. Our findings suggest that adult D. kuriphilus, previously reported as proovigenic, may be resorping eggs in the absence of suitable hosts, and reallocating nutritive resources for body maintenance and egg quality to increase fitness, implicating a plasticity in its reproductive strategy. D. kuriphilus may be able to vary its potential fecundity in response to nutrition and host availability, thus increasing its invasiveness. [ABSTRACT FROM AUTHOR]

Sleeve cages for enclosing or excluding arthropods are essential components of field studies evaluating trophic interactions. Microclimatic variation in sleeve cages was evaluated to characterize its potential effects on subsequent long-term experiments. Two sleeve cage materials, polyester and nylon, and two cage sizes, 400 and 6000 cm2, were tested on eastern hemlock, Tsuga canadensis (L.) Carrière. Temperature and relative humidity inside and outside cages, and the cost and durability of the cage materials, were compared. Long-term effects of the sleeve cages were observed by measuring new growth on T. canadensis branches. The ultimate goal was to identify a material that minimizes bag-induced microclimatic variation. Bagged branches whose microclimates mimic those of surrounding unbagged branches should have minimal effects on plant growth and may prove ideal venues for assessing herbivore and predator behavior under natural conditions. No differences were found in temperature or humidity between caging materials. Small cages had higher average temperatures than large cages, especially in the winter, but this difference was confounded by the fact that small cages were positioned higher in trees than large cages. Differences in plant growth were detected. Eastern hemlock branches enclosed within polyester cages produced fewer new growth tips than uncaged controls. Both polyester and nylon cages reduced the length of new shoot growth relative to uncaged branches. In spite of higher costs, nylon cages were superior to polyester with respect to durability and ease of handling. [ABSTRACT FROM AUTHOR]

In the eastern United States, eastern hemlock Tusga canadensis (L.) Carriere forests are threatened by the invasive hemlock woolly adelgid, Adelges tsugae, a pest that is causing widespread hemlock mortality. Eastern hemlock is an essential component of forested communities. Adelgid-induced hemlock mortality is causing a shift in forest composition and structure, altering ecosystem function and thereby influencing the arthropod community. Using pitfall traps at three sites, we monitored ground-dwelling arthropods at 30-d intervals in hemlock-dominated and deciduous-dominated forests in central Appalachia over 2 yr. Here, we focus on the ant community (Hymenoptera: Formicidae) collected in the summer months. Ants form a ubiquitous and integral component of the invertebrate community, functioning at various trophic levels as predators, herbivores, and omnivores, and fulfilling important roles in forest ecosystems. We found no difference in overall ant abundance between hemlock-dominated and deciduous-dominated forests but did detect significant differences in the genera Prenolepis between forest types (P < 0.01) and Aphaenogaster across study locations (P¼0.02). Three genera were unique to deciduous forests; one was unique to hemlock forests. Not surprisingly, total formicids and several genera demonstrated temporal differences in abundance, with greater numbers captured in July than in August. As hemlock woolly adelgid-induced mortality of eastern hemlock becomes more pervasive, changes in forest composition and structure are imminent, accompanied by shifts in hemlock associates. [ABSTRACT FROM AUTHOR]

The article focuses on a research conducted in order to identify the effects of jasmonic acid (JA) and a JA-inhibitor, diethyldithiocarbamic acid on the growth and defense of the Asian chestnut gall wasp, Dryocosmus kuriphilus galls formed on American chestnut, Castanea dentata. It discusses the importance of JA in defenses against insects and pathogens as well as the regulation of nutrient partitioning. The study revealed the importance of JA treatments on gall wasps.

Eastern hemlock [Tsuga canadensis (L.) Carribre] is a foundation species in forests of eastern North America that plays a key role in ecosystem function. It is highly susceptible to the exotic invasive hemlock woolly adelgid (Adelges tsugae Annand), which is causing widespread hemlock mortality. We surveyed the spider communities of eastern hemlock and deciduous canopies over 2 yr, collecting over 4,000 spiders from 21 families. We found that eastern hemlock canopies harbored a more abundant, rich, and diverse spider community than did deciduous canopies. Five spider families were present in our hemlock collections that were absent from the deciduous collections, including Mysmenidae, Theridiosomatidae, Mimetidae, Lycosidae, and Agelenidae. In hemlock canopies there were 4x the number of web builders, consisting primarily of the Tetragnathidae and Araneidae, than active hunters, consisting primarily of the Anyphaenidae and the Salticidae. Ours is the first in depth study of the spider community in eastern hemlock. Spider abundance in hemlock canopies suggest that they may play a role regulating herbivore populations, and could possibly affect the invasive hemlock woolly adelgid, either through direct consumption of the adelgids themselves or through interactions with classical biological control agents. [ABSTRACT FROM AUTHOR]

We examined the arthropod community on eastern hemlock, Tsuga canadensis (L.) Carr, in the context of its role in providing potential prey items for hemlock-associated web-weaving spiders. Using sticky traps simulating spider webs, we evaluated what prey items are available to web-weaving spiders in eastern hemlock based on web orientation (horizontal versus vertical) and cardinal direction. We found that the overwhelming majority ( >70%) of prey items available to spiders in hemlock canopies were Diptera. Psocoptera, Hymenoptera, and Hemiptera comprised most of the remaining potential prey. A significant direction X orientation interaction, and greater trap capture in some directionorientation combinations, suggests that spiders might locate their webs in eastern hemlock canopies for thermoregulatory purposes, ultimately optimizing prey capture. We also evaluated these findings in the context of hemlock infestation by the invasive hemlock woolly adelgid, Adelges tsugae Annand. The adelgid is a sedentary insect with a mobile crawler stage that provides a readily available, easily obtained food source for predators in hemlock canopies. However, an abundance of alternative prey will affect within canopy spider distribution and the potential intensity with which spiders consume these prey. Understanding the response of spiders to potential prey availability is essential to understanding the trophic interactions involving these predators and their potential for influencing herbivore populations. [ABSTRACT FROM AUTHOR]

Gall wasps (Hymenoptera: Cynipidae) induce structures (galls) on their host plants that house developing wasps and provide them with protection from natural enemies. The Asian chestnut gall wasp, Dryocosmus kuriphilus Ya.sumatsu, is an invasive pest that is destructive to chestnut (Castanea spp.). An improved understanding of the interactions among D. kuriphilus, its host, and its natural enemies is critical for the development of effective management strategies against this pest. The objective of our study was to evaluate the D. kuriphilus community interactions, and relate these interactions to variations among gall traits. Galls were collected from four locations throughout the eastern United States from May (gall initiation) through August (after gall wasp emergence), and January, Gall characteristics (volume, weight, and schlerenchyma layer thickness) ,gall inhabitants (D. kuriphilus, parasitoids, and chamber fungi), and other community associates (insect herbivores and lesions thought to be caused by endophytes) were evaluated and correlated using canonical correlation analyses. The primary mortality factors for D. kuriphilus were parasitism, gall chamber-invading fungi, and failure of adult gall wasps to emerge. Larger gall size and thicker schlerenchyma layers surrounding the larval chambers were negatively correlated with parasitoids and chamber fungi, indicating these gall traits are important defenses. External fungal lesions and insect herbivory were positively correlated with the absence of D. kuriphilus within galls. This study provides support for the protective role of cynipid galls for the gall inducer, identifies specific gall traits that influence gall wasp mortality, and improves our knowledge of D. kuriphilus ecology in North America. [ABSTRACT FROM AUTHOR]