The hemlock woolly adelgid, Adelges tsugae Annand, is an invasive pest of eastern (Tsuga canadensis (L.) Carrière) and Carolina hemlock (Tsuga caroliniana Engelmann) forests in the eastern United States. Scymnus (Pullus) coniferarum Crotch (Coleoptera: Coccinellidae) is a lady beetle that preys on A. tsugae in the western United States, where A. tsugae infestations on western hemlocks are not lethal. It is thought that S. coniferarum could be an important predator that helps keep A. tsugae populations from reaching damaging levels in this region. This study assesses the potential of this predator as a biological control agent for A. tsugae in the eastern United States. S. coniferarum predation, reproductive potential, and survival were evaluated in field-cages on adelgid-infested T. canadensis at two sites in southwestern Virginia. Sampling was conducted between December 2012 and June 2014 to evaluate the impact of S. coniferarum on both generations of A. tsuage (sistens and progrediens). Adult S. coniferarum fed on both generations and all life stages of A. tsugae during both field trials at rates comparable to other adelgid-specific predators. Evidence of S. coniferarum oviposition was minimal, and may be attributed to low temperatures and prey availability. S. coniferarum mortality was greatest when exposed to winter temperatures at the higher elevation site in 2013, and least throughout the 2014 spring sample period. S. coniferarum demonstrated a high predation rate on A. tsugae and survived for extended periods of time at sites in southwest Virginia, indicating that this species could be an effective predator of hemlock woolly adelgid in similar climates.
The fall cankerworm, Alsophila pometaria (Harris), is a species endemic to North America that feeds on broadleaf trees and shrubs. Fall cankerworm is a generalist folivore and larvae feed on a wide range of deciduous trees and smaller woody plants. Common hosts include oak, maple, cherry, ash, apple, beech, and birch. This pest is prone to repeated outbreaks over large areas, can cause extensive defoliation throughout hardwood forest stands, and can be a public nuisance in developed or highly populated areas. Fall cankerworm defoliation can lead to reduced tree health and impact ecosystem function, carbon sequestration, wildlife habitat, and temperature regulation, especially in urban areas. Elevated populations often occur in areas where host trees are stressed or a high density of a preferred host species is present. Fall cankerworm management is often necessary due to their impacts on the local tree canopy and nuisance to the public. Tree banding and the use of the biological insecticide Bacillus thuringiensis (Bt) are the common management tactics used to reduce fall cankerworm populations. Here we review fall cankerworm distribution, life stages, host plants, damage, scouting and sampling procedures, management options, and discuss commonly associated and co-occurring defoliator species.
The hemlock woolly adelgid (HWA), Adelges tsugae, is an invasive pest of Tsuga spp. in eastern North America. Scymnus coniferarum is a predaceous beetle that was collected from HWA in the western United States. Limited knowledge of this insect in its native habitat led to studies to evaluate its potential for biological control of HWA. Seasonal abundance was sampled at six sites in Tacoma, WA, twice monthly, for one year on different host trees of potential adelgid prey. Tree species included Pseudotsuga menziesii, Pinus contorta, Pinus monticola, and Tsuga heterophylla. Scymnus coniferarum adults were found on all conifer species, except P. menziesii. Each conifer species supported a different adelgid species, suggesting S. coniferarum feeds on multiple adelgid species. More S. coniferarum were found on pine than hemlock. DNA barcoding of S. coniferarum found two distinct clusters that differed by 6% divergence. Beetles in each cluster were co-habiting the same conifer species, and they could not be distinguished morphologically. Further taxonomic studies are needed to understand the significance of DNA barcode sequence divergence. Because S. coniferarum was more frequently associated with pine adelgids than HWA, and because of remaining taxonomic uncertainty, S. coniferarum may not be suitable for HWA biological control.
Fraser fir, Abies fraseri [Pursh] Poir., is one of the most desired Christmas tree species owing to its fragrance, physical appearance, and durability. This species represents a major component of the Christmas tree industry in the southeastern United States, with production occurring in North Carolina, Tennessee, and Virginia. Fraser fir production is a multi-million dollar annual industry despite growing in a limited elevational and latitudinal range. Pest management for Christmas trees is notoriously difficult owing to the near zero-tolerance of most pests, even those causing aesthetic damage. Christmas trees are produced in monocultural environments which make them highly susceptible to several arthropod and fungal pests. We review the major pests affecting Fraser fir Christmas tree production, including their biology, symptoms, and scouting procedures, and current management strategies. In general, pest management in Christmas tree production systems has not changed significantly in the last several decades, and still relies heavily on pesticide usage. We propose several areas in need of research that could help Fraser fir Christmas tree producers mitigate the impacts of climate change and potential new pest species, as well as suggest changes to current or potentially novel integrated pest management strategies which have a chance to provide economic and ecological benefits for this industry.
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