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Aphelinus mali (Haldeman) (Hymenoptera: Aphelinidae) in China is comprised of two clades (termed, the Shandong and Liaoning clades). In order to clarify the genetic relationship between these two clades, we compared and analyzed the morphological characteristics and the mitochondrial genome of each, and performed a hybridization experiment. Morphological results showed that both males and females of the Liaoning clade were larger than Shandong clade, in terms of whole body, abdominal, wing and antennal lengths, however, there were no significant differences between clades for total length of the middle or hind leg of females. The length of the mitochondrial genome of the Shandong clade was 14415 bp and, for the Liaoning clade, it was 14804 bp. Each contained 31 genes, including 13 protein-encoded genes, 16 tRNA genes, and 2 rRNA genes. The highest AT level among the 13 protein-coding genes for the two clades were the same gene (ATP8) (Shandong clade, 91.52%; Liaoning clade, 90.91%). By hybridization and backcrossing, we found that there was no cross incompatibility between these two clades of A. mali. Our results indicate that the historic geographical isolation between these clades has not yet caused reproductive isolation of these populations, and they belong to the same species.

The hemlock woolly adelgid (HWA), Adelges tsugae, has threatened the sustainable management of Tsuga canadensis in the eastern United States. Biological control efforts have led to the establishment of Laricobius nigrinus, a specialist predator of HWA. Although L. nigrinus has a significant impact on HWA populations, its effect on the health of HWA’s host is unknown. In 2020, 14 eastern hemlocks at one site in Virginia were selected to determine whether predation of L. nigrinus at different densities on HWA populations had an effect on tree health. Laricobius nigrinus predation significantly impacted the HWA sistens generation, resulting in significantly more new shoots produced on treatment branches with the greatest density of L. nigrinus adults. Final HWA density was lowest on treatment branches with L. nigrinus, followed by the negative control, and the treatment without L. nigrinus. In June, the photosynthetic rate was significantly greater for the negative control, followed by L. nigrinus treatments. There were no statistical differences among measured tree physiological parameters in July and October, indicating a temporary effect from L. nigrinus predation on hemlock tree physiology.

Hemlock woolly adelgid (HWA), Adelges tsugae Annand, threatens hemlock forests throughout eastern North America. Management efforts focus on early detection of HWA to ensure rapid management responses to control and stop the spread of this pest. This study's goal was to identify an affordable, efficient trap to aid with airborne environmental DNA (eDNA) sampling approaches as an early monitoring tool for HWA. We initially compared HWA detection success between a standard sticky trap, commonly used for HWA monitoring, and trap designs potentially compatible with eDNA protocols (i.e., passive trap, funnel trap, and motorized trap). Passive, funnel, and motorized traps' estimated capture success probabilities compared to sticky traps were 0.87, 0.8, and 0.4, respectively. A secondary evaluation of a modified version of the motorized trap further assessed trap performance and determined the number of traps needed in a set area to efficiently detect HWA. By modifying the original motorized trap design, its estimated capture success probability increased to 0.67 compared to a sticky trap. Overall, the cumulative capture success over the 16-week sampling period for the motorized trap was 94% and 99% for the sticky trap. The number of traps did impact capture success, and trap elevation and distance to infested hemlocks influenced the number of adelgids captured per trap. As eDNA-based monitoring approaches continue to become incorporated into invasive species surveying, further refinement with these types of traps can be useful as an additional tool in the manager's toolbox.

There have been four subspecies of hemlock dwarf mistletoe (Arceuthobium tsugense: Viscaceae) described by various investigators of this complex group of parasitic flowering plants: subsp. tsugense, subsp. amabilae, subsp. contortae, and subsp. mertensianae. As suggested by their subspecific epithets, these taxa differ in their host affinities; parasitizing different and the same hosts to varying degrees. Although these taxa also have morphological differences, their classification has been under debate for many years. Therefore, we compared the morphological characteristics of each subspecies using both univariate and multivariate statistical analyses in order to better assess their differences. Because some investigators have grouped hemlock dwarf mistletoe with western dwarf mistletoe (A. campylopodum), we also compared the subspecies of hemlock dwarf mistletoe with western dwarf mistletoe. Our morphometric analyses demonstrated that all of the subspecies are morphologically distinct from western dwarf mistletoe and that subsp. contortae is the most morphologically differentiated of the subspecies. Overlap in the morphological characters across two of the other three subspecies was evident; yet, subsp. amabilae and subsp. mertensianae were also consistently delimited using female and male plant morphologies. Statistical comparisons of female or male plants via standard and stepwise discriminant function analyses demonstrated that without consideration of host plant, female and male A. tsugense subsp. tsugense are morphologically similar to corresponding plants of subsp. amabilae and mertensianae but not subsp. contortae or A. campylopodum. Ha habido cuatro subespecies de muérdago enano (Arceuthobium tsugense: Viscaceae) descritos por varios investigadores en este grupo complejo de angiospermas parásitas: subsp. tsugense, subsp. amabílae, subsp. contortae, and subsp. mertensianae. Corno se sugiere por sus epitetos subespecificos, estos taxa difieren en sus afinidades por los huéspedes; parasitando diferentes y el mismo huésped en varios grados. Aunque estos taxa también tienen diferencias morfológicas, su clasificación ha estado en debate durante muchos años. Sin embargo, hemos comparado las características morfológicas de cada subespecie usando análisis estadísticos tanto univariantes corno multivariantes para evaluar mejor sus diferencias. Como algunos investigadores han agrupado este muérdago enano con otro muérdago enano del oeste (A. campylopodum), nosotros también comparamos las subespecies de ambos muérdagos. Nuestro análisis morfométrico demostró que todas las subespecies son distintas morfológicamente del muérdago enano del oeste y que la subsp. contortae es la más diferenciada morfológicamente de las subespecies. El solapamiento en los caracteres morfológicos entre dos de las otras tres subespecies fue evidente; aunque, subsp. amabilae y subsp. mertensianae fueron también delimitadas consistentemente usando morfologias de plantas masculinas y femeninas. Las comparaciones estadísticas de plantas masculinas o femeninas mediante análisis de función discriminante standard y aumentada demostró que sin consideración de la planta huésped, los ejemplares masculinos y femeninos de A. tsugense subsp. tsugense son similares morfológicamente a las plantas correspondientes a las subsp. amabilae y mertensianae pero no a la subsp. contortae o A. campylopodum.

We developed an approach using sticky trap arrays as an early detection tool for populations of first-instar nymphs of the hemlock woolly adelgid (Adelges tsugae Annand), a pest of hemlocks (Tsuga spp. [Pinaceae]) in North America. We considered the detection rate of at least one nymph from trapping arrays consisting of one to six sticky panels, where we varied both the surface area of each trap that we assessed and the length of the trapping duration. We also estimated the time needed to set up, service, and assess groups of traps and attempted to relate capture of nymphs on traps to incidence and abundance of A. tsugae in the canopy above the traps. Arrays consisting of two traps provided a detection rate of 75% when 87.5% of the surface area of each trap was assessed, a process that required 38 min per array.The probability of detecting nymphs on traps left in the field for 5–6 d was similar to that for traps left for 12 d. The number of nymphs trapped in an array predicted the probability of finding A. tsugae in the canopy but only when all six traps were fully assessed. To reliably detect incipient A. tsugae infestations, we recommend placing arrays of traps at 1 km intervals along the perimeter of a stand during peak activity of first-instar sistentes nymphs and servicing these arrays every 5–7 d.

The wool of the invasive, non-native hemlock woolly adelgid, Adelges tsugae Annand (Hemiptera: Adelgidae), occurs mostly on hemlock (Tsuga sp.) twigs, but can be dislodged from the canopy and end up on the forest floor and tree stem underneath the canopy. Herein, we developed and tested the efficacy of two novel sampling techniques, which are based on a visual examination of the forest floor and the hemlock stem for A. tsugae wool. Subsequently, we compared these two techniques to a visual examination of foliage and ball sampling which are two methods currently used operationally. We sampled 11 hemlock stands, with low to moderate incidence A. tsugae populations, near Ithaca, New York in 2016 and assessed the probability of detecting wool on a tree and in a stand, as well as the relative variation and relative net precision for each of the four techniques. We found that sampling the tree stem outperformed foliage and ground sampling, likely because of its higher detection rate and lower relative variation, but not ball sampling. Our findings suggest that combining stem, ball and ground sampling was the most effective combination of techniques and gave a high probability of detecting an infested tree or an infested stand. All techniques were an improvement over foliage sampling, even after increasing the foliage sampling effort fivefold.

Hemlock woolly adelgid (Adelges tsugae [Annand]), an invasive insect in the eastern United States, has caused widespread decline of eastern hemlock, Tsuga canadensis (L.) Carriére. Imidacloprid basal drench treatments were assessed 4–7 yr after a single treatment to determine hemlock woolly adelgid population suppression and effects on hemlock canopy health. The effects of sampling site, years post-treatment, and hemlock diameter at breast height (DBH) size classes were evaluated relative to imidacloprid treatment on hemlock woolly adelgid populations and hemlock canopy health characteristics. The influence of hemlock woolly adelgid populations on canopy health characteristics was also assessed. Imidacloprid treatments resulted in low-level hemlock woolly adelgid populations 7 yr post-treatment. Hemlock woolly adelgid was present on more hemlocks 7 yr compared with 4–6 yr post-treatment. Smaller hemlocks, dosed with 0.7 g active ingredient (AI)/2.5 cm DBH, had higher populations of hemlock woolly adelgid than the largest size class, which were treated at twice that dosage. Concentrations of imidacloprid and its olefin metabolite below the LC50 were sufficient for suppression of hemlock woolly adelgid populations, which suggests an additive effect of imidacloprid and olefin that compounds hemlock woolly adelgid mortality over many generations. Hemlock woolly adelgid populations observed in this study were too low to have an observable effect on hemlock canopy health, indicating that application intervals of up to 7 yr may be adequate to protect hemlocks.

Abstract Forests provide critical ecological and economic services in Bhutan. After reports of a heavy adelgid infestation damaging trees in a forest nursery in Changaphu in 2019, a country-wide survey was conducted between 2020 and 2022. Eight adelgid species were found. Four were described elsewhere before this survey: Adelges (Annandina) tsugae Annand, Ad. (Gilletteela) glandulae, Pineus (Pineus) armandicola Zhang, Zhong and Zhang, and P. (P.) wallichianae Yaseen and Ghani. The remaining 4 were new species described in a separate paper: Ad. (Cholodkovskya) changaphuensis Havill and Brunet, Ad. (Cassiadelges) coccipus Havill and Brunet, Ad. (Dreyfusia) densae Havill and Brunet, and Ad. (An.) lepsimon Havill and Brunet. The distribution, DNA barcode diversity, and biology of each species are discussed here. In addition, fungi associated with P. (P.) armandicola from different sites were identified using internal transcribed spacer and 28S DNA sequences as phylogenetically diverged members of the sooty mold family Capnodiaceae, suggesting that the association may not be species-specific. Finally, the dipteran predators associated with adelgids were summarized as a potential source of biological control agents. Immature morphology and DNA barcodes identified 3 operational taxonomic units of Lestodiplosis (Cecidomyiidae), one each of Episyrphus, Parasyrphus, and Melangyna (Syrphidae), 1 Leucopis and 4 Neoleucopis (Chamaemyiidae). DNA barcodes also identified hymenopteran parasitoids inside some cecidomyiid specimens as Playtgastridae and inside some chamaemyiid specimens as Figitidae and Pteromalidae, highlighting the multitrophic nature of potential pest management.

The abundance of eastern hemlock ( Tsuga canadensis ) in eastern US forests has declined since the 1950s owing to the introduction of the non-native insect, hemlock woolly adelgid (HWA, Adelges tsugae ). In southern New England, eastern hemlock is being replaced by the deciduous tree species, black birch ( Betula lenta ). To date there is little understanding of whether hemlock loss will fundamentally alter ecosystem C balance and component fluxes. In this study, we use a comparative approach to study potential changes in C fluxes and N cycling associated with HWA-induced hemlock decline and replacement. The stands include primary- and secondary-growth hemlock forests (>230 and 132 years old, respectively), recently disturbed stands (5 and 18 years old) that now have rapidly growing black birch saplings, and a mature black birch stand of age similar to the second-growth hemlock stand. We found that aboveground net primary production was higher in the aggrading black birch stand and significantly so at 18-years post-HWA compared to the secondary-hemlock stand it would likely replace. Rapid forest regrowth was accompanied by significantly higher rates of N uptake from the soil but also higher N-use efficiency because most of the N taken up from the soil was allocated to the production of wood with a high C-to-N ratio. In contrast to patterns of aboveground production, the rate of soil respiration was lowest in the young stands and not significantly different from the second-growth hemlock stand, suggesting little net effect of stand replacement on soil C efflux. The leaf litter decomposition study showed that black birch litter decomposed more rapidly than hemlock litter but that there was no effect of stand type on the rate of decomposition. Analyses of extracellular microbial exoenzyme activity painted a more nuanced pattern of variation among stands, with fine root biomass the only weakly explanatory variable. In combination with our prior work on C stocks, these results suggest that forests affected by HWA in southern New England will remain a sink for atmospheric CO 2 despite reorganization of stand structure and species composition.