Fig 1 - available via license: Creative Commons Attribution-NonCommercial 4.0 International
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Gloomy scale adult female (pink) with dorsal test removed. The white center and black outer ring of ventral test can be seen under the softbodied female. Intact dorsal tests of gloomy scales of various life stages are also shown. Gloomy scale (Diaspididae: Melanaspis tenebricosa) Matt Bertone, https://www.flickr.com/photos/76790273@N07/8631555279, 2013, by permission of Matt Bertone.
Source publication
Gloomy scale, Melanaspis tenebricosa (Comstock), is native to the eastern United States and feeds on deciduous trees. In natural areas, it is a background herbivore that typically remains at low densities. Gloomy scale generally responds positively to warming with greater egg production, size, survival, and abundance. In urban areas, which are warm...
Contexts in source publication
Context 1
... scales are covered ventrally and dorsally by an armored covering called a test (Fig. 1). The ventral test is flat, white in the center and black around the edge, and attaches to the bark of the host tree (Comstock 1881, Metcalf 1922. Gloomy scale, like other armored scales, feed on fluids from parenchyma cells with piercing-sucking mouthparts (Beardsley and Gonzalez 1975). The dorsal test (henceforth referred to as test) ...
Context 2
... soft body of adult female gloomy scales are nearly round and measure 1-1.5 mm long from their pygidium (fused abdominal segments) to the anterior end of their body (Metcalf 1922, Deitz and Davidson 1986, Dale and Frank 2014b. They are slightly convex and are pale cream to dark pink ( Fig. 1). Female gloomy scales lack antennae, eyes, legs, and wings, and their body segmentation is unpronounced. Adult females are morphologically juvenile save mature sexual organs. Including their tests, they are up to 2 mm in diameter ...
Citations
... In addition, water stress on trees, caused by urban warming and drought, exacerbates the negative effects of these scale insects on tree growth [53, 54•, 100]. Gloomy scale (Melanaspis tenebricosa Comstock) is an herbivore of red maples in the southeastern USA where it is native [102]. Its geographic distribution is limited by cold temperatures [103]. ...
Purpose of Review
Our goal is to provide an overview of how urban heat islands affect forests and synthesize recent literature on that topic. We focused on direct effects of high temperatures from urban heat islands on forest trees and indirect effects via changes in soil moisture and pest density. We also focused on the effects of urban heat islands on arthropods with particular emphasis on tree pests.
Recent Findings
Urban heat islands can push trees and arthropods closer to their thermal limits with consequences for tree growth and arthropod fitness. Urban heat islands can alter the distribution of trees and arthropods allowing species to survive at higher altitudes or latitudes than they could otherwise. A primary risk for trees is that urban heat islands can increase pest density and damage.
Summary
Urban heat islands can increase forest air and soil temperature and reduce soil moisture especially when combined with greater climate change. Land managers should consider the surrounding urban density and forest size when trying to determine which plants and animals can persist in urban forests. As forests are fragmented or encroached upon by urbanization, the forest environment will change and become more hospitable for some species and less hospitable for others. Overall, there is insufficient research focused on urban-forest interfaces and the consequences of urbanization for plants and animals within forests. This research is not only important for urban forest conservation. Tree and arthropod responses to urban heat islands will help scientists and land managers predict responses to climate warming in rural areas as well.
... Melanaspis tenebricosa is a univoltine, armored scale insect herbivore that feeds on xylem parenchyma cells within the woody tissue of primarily A. rubrum [49][50][51]. These sessile insects are drastically more abundant and damaging in urban than surrounding rural habitats [27,46,50,52]. ...
... All trees were in the right-of-way and therefore property of the City of Raleigh, NC, USA. In Raleigh, NC and other eastern U.S. cities, A. rubrum is the second most common street tree, comprising nearly 14% of street trees [51]. To select study sites, we used ArcMap 10.2 to overlay a geocoded street tree inventory map onto a Landsat thermal image of surface temperature acquired on 18 August 2007, prepared as described in Meineke et al. [53]. ...
... Acer rubrum represents a significant proportion of the urban and natural forest species composition throughout the eastern U.S. and has traits that many urban trees are selected for, such as rapid growth, high aesthetic quality, dense canopies, and moderate tolerance to water stress [66]. Although previous work has found that the effects of local abiotic factors on urban Acer rubrum pests and tree condition persist across latitudes [45,51], the implications of our results for urban forest health may not translate to other tree species. Therefore, future work should investigate similar interactions with other common urban tree taxa to develop more comprehensive guidelines for urban forest managers. ...
Warmer temperatures and frequent drought directly affect urban tree health. Both abiotic conditions also affect tree health via increased density of some insect pests. Warming is predicted to benefit urban trees by increasing carbon sequestration and allocation to biomass. However, increased drought and pests are rarely considered despite often co-occurring with heat. To determine the combined effects of these abiotic and biotic factors, we manipulated water availability for established urban red maple trees across a gradient of warming and pest density and measured leaf-level processes and tree growth over two years. We find that water availability is a major determinant of tree growth, physiological processes, and resilience to urban stress factors. Maples performed better with more water, which also made them resistant to effects of temperature and pest density. However, when drought became too severe, leaf-level processes declined with warming. Tree basal area growth was unaffected after two years, but stem elongation increased with increasing water, temperature, and pest density. We discuss potential mechanisms driving these responses and the implications in the context of urban forest management. Urban forest designs that reduce drought and align species adaptations to local conditions are critical for designing more resilient and productive urban forests.
... Research is needed to understand the correlation between elevation and OSS infestation, but temperature is a likely explanation. Fitness and abundance of other scale insect pests has been linked to climate (Frank 2020;Just et al. 2020), and low temperatures are known to reduce survival of overwintering OSS eggs (Tothill 1919). Therefore, colder temperatures at higher elevations might directly limit OSS. ...
... On the other hand, a warmer climate may have directly improved conditions for OSS population growth by increasing the species' fitness and abundance (Frank 2020;Frank and Just 2020). Because OSS appears to be limited to aspen stands below 2500 m (Table 1), cold temperatures may be a limiting factor for its spread, which is consistent with other scale insect pests (Frank 2020;Just et al. 2020) and OSS in other locations (Furniss and Carolin 1977). Temperature changes that have already occurred may have enabled OSS's spread outside urban areas Just et al. 2020), and in the future, warmer temperatures at higher elevations and latitudes may promote further spread of OSS (Frank 2020). ...
... Because OSS appears to be limited to aspen stands below 2500 m (Table 1), cold temperatures may be a limiting factor for its spread, which is consistent with other scale insect pests (Frank 2020;Just et al. 2020) and OSS in other locations (Furniss and Carolin 1977). Temperature changes that have already occurred may have enabled OSS's spread outside urban areas Just et al. 2020), and in the future, warmer temperatures at higher elevations and latitudes may promote further spread of OSS (Frank 2020). The former would threaten the largest, healthiest aspen stands in northern Arizona, which occur at higher elevations, and the latter would threaten the rest of aspen's range in the western US because Arizona is situated on the southwestern edge of the tree's range. ...
Oystershell scale (OSS; Lepidosaphes ulmi) is an emerging invasive insect that poses a serious threat to conservation of quaking aspen (Populus tremuloides) in the southwestern US. Although OSS has been an urban pest in the US since the 1700s, it has recently spread into natural aspen stands in northern Arizona, where outbreaks are causing dieback and mortality. We quantified the ongoing outbreak of OSS at two scales: (1) local severity at two sites and (2) regional distribution across northern Arizona. Our regional survey indicated that OSS is widespread in lower elevation aspen stands and is particularly pervasive in ungulate exclosures. Advanced regeneration had the highest levels of infestation and mortality, which is concerning because this size class is an underrepresented component of aspen stands in northern Arizona. If OSS continues to spread and outbreaks result in dieback and mortality like we observed, then aspen in the southwestern US, and perhaps beyond, will be threatened. Three interacting factors contribute to OSS’s potential as a high-impact invasive insect that could spread rapidly: (1) its hypothesized role as a sleeper species, (2) potential interactions between OSS and climate change, and (3) the species’ polyphagous nature. Invasive pests like OSS pose an imminent threat to native tree species and, therefore, represent an immediate research and monitoring priority. We conclude with recommendations for future research and monitoring in order to understand OSS’s biology in natural aspen stands, quantify impacts, limit future spread, and mitigate mortality and loss of aspen and other host species.
Urban trees often host greater insect pest abundance than trees in rural forests. This may be due, in part, to differences in tree diversity and canopy cover between these settings. Urban trees are often planted in isolation or monoculture, which favors pest accumulation. Gloomy scale, Melanaspis tenebricosa Comstock, is a pest of urban red maples (Acer rubrum L.) that is abundant where impervious surfaces dominate the local landscape. Increasing tree diversity and canopy cover around urban red maples may reduce gloomy scale abundance by supporting natural enemy communities. We investigated the effect that surrounding tree species richness and tree canopy cover had on gloomy scale abundance, natural enemy abundance, and biological control in red maple trees in Raleigh, NC, USA. We collected scales and natural enemies from red maples that spanned a gradient of tree species richness, canopy cover, and impervious surface values. We also measured gloomy scale parasitism and predation of sentinel prey in red maple canopies. Greater tree species richness and canopy cover were associated with lower gloomy scale density. Red maples in diverse settings also hosted fewer scales per natural enemy. Parasitoids were less common in maples in diverse settings, but generalist predator abundance was unaffected by tree diversity. Finally, tree species richness and canopy cover did not increase biological control of scales or sentinel prey. Our findings suggest that higher tree diversity and greater canopy cover may reduce gloomy scale density, but this is not entirely explained by the effects of natural enemies and biological control.
