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Forest pests pose a major threat to ecosystem services worldwide, requiring effective monitoring and management strategies. Recently, satellite remote sensing has emerged as a valuable tool to detect defoliation caused by these pests. Lymantria dispar, a major forest pest native to Japan, Siberia, and Europe, as well as introduced regions in North America, is of particular concern. In this study, we used Sentinel-2 satellite imagery to estimate the defoliation area and predict the distribution of L. dispar in Toyama Prefecture, central Japan. The primary aim was to understand the spatial distribution of L. dispar. The normalized difference vegetation index (NDVI) difference analysis estimated a defoliation area of 7.89 km2 in Toyama Prefecture for the year 2022. MaxEnt modeling, using defoliation map as occurrence data, identified the deciduous forests between approximately 35° and 50° at elevations of 400 m and 700 m as highly suitable for L. dispar. This predicted suitability was also high for larval locations but low for egg mass locations, likely due to differences in larval habitats and ovipositing sites. This study is the first attempt to utilize NDVI-based estimates as a proxy for MaxEnt. Our results showed higher prediction accuracy than a previous study based on the occurrence records including larvae, adults, and egg masses, indicating better discrimination of the distribution of L. dispar defoliation. Therefore, our approach to integrating satellite data and species distribution models can potentially enhance the assessment of areas affected by pests for effective forest management. [ABSTRACT FROM AUTHOR]

Cadmium pollution is becoming an increasing problem, especially in parts of the world that have developed industries. To consider the potentially harmful effects of cadmium, we need to examine changes at all different levels of biological organization. The main goal of this study was to detect a possible change in the percentage of midgut mass relative to larval mass (PMM) and determine the plasticity of this trait and the correlations between midgut enzymes and PMM under stress conditions. Fourth-instar larvae were exposed to acute and chronic effects of two cadmium concentrations, 10 and 30 μg Cd/g dry food, as well as a threeday recovery from chronic treatments. PMM is also an indirect indicator of food consumption and was found to be significantly reduced compared to control in both acute effects and chronic treatment at 30 μg and its three-day recovery. The PMM reduction during acute treatments is a consequence of cadmium action, while in chronic treatment, the genetic factor (egg mass) plays a crucial role in the change of PMM. According to the index of plasticity, distinct phenotypes were not produced. Significant correlations were shown between PMM and trypsin (Tryp) and leucine aminopeptidases (LAP) at acute and chronic treatment with higher cadmium concentrations, while significant correlations between proteases and PMM were detected at lower metal concentrations (Acute10 and Chronic10 and 30 μg Cd/g dry food). In contrast to chronic treatment, egg masses respond more uniformly by reducing PMM during the short-term effect of cadmium. Finally, we can conclude that, as an addition to biochemical and molecular research, PMM can be used for studying the cadmium effects to gain a better insight into the state of the organism under stress conditions. [ABSTRACT FROM AUTHOR]

The parasitoid wasp, Ooencyrtus kuvanae (Howard) (Hymenoptera: Encyrtidae), is a natural enemy of the spongy moth, a significant forest pest in North America. We investigated the oviposition behavior of O. kuvanae females on spongy moth egg masses by (i) presenting female parasitoids with a single spongy moth egg mass that was replaced every day, 2nd day, 4th day, 8th day, or 16th day (which is the total length of the oviposition period) and (ii) presenting female parasitoids with 1, 2, 4, or 8 egg masses at a time. Offspring developmental length ranged from 18 to 24 days. On average, male offspring exhibited faster developmental times, emerging approximately 1 day ahead of females. The amount of time that adult females spent on an egg mass affected the number of parasitized eggs. Specifically, more offspring emerged in the 4-, 8-, and 16-day treatments than in scenarios involving daily or every second-day egg mass replacement. The percentage of male offspring decreased as the number of egg masses presented to females increased. Interestingly, the total number of female offspring remained constant, but the number of male offspring decreased with an increase in the number of egg masses and time spent by the parent within a patch. The observed sexual dimorphism in development time, the influence of resource availability on offspring sex ratios, and flexible oviposition patterns illustrate the adaptability of O. kuvanae in response to varying conditions. These insights have implications for our understanding of parasitoid–host interactions and their potential role in biological control strategies. [ABSTRACT FROM AUTHOR]

The binomial distribution is often used in modeling, including in applied climatology, when assessing the likelihood of adverse or dangerous climate-related impacts. The article outlines an algebraic algorithm for obtaining such estimates based on climate monitoring data or modeling data. Using only algebraic operations in calculations minimizes calculation time, which is important when performing detailed global assessments. As an example of such a calculation, the result of an assessment of the global climatic range of a dangerous insect pest of forest and garden trees and shrubs, the gypsy moth, is given. [ABSTRACT FROM AUTHOR]

Baculoviruses, especially prevalent in Lepidoptera, have attracted the most attention as biological insect control agents. Infection with baculoviruses is usually fatal and therefore can affect the host population density, especially if virus transmission increases with host density. Lepidoptera larvae show a strong dose-dependent response to pathogens such as baculoviruses, so their response to various pathogen exposures was studied in this work. Models of virus exposure to insect hosts are usually judged by whether or not they generate cyclical population dynamics of multiple host generations. However, the existing theoretical models based on systems of differential equations are of little use for practical application due to the large number of variables and free parameters. In this regard, the possibility of using a mathematical model for describing the epizootic Malacosoma neustria L. and Lymantria dispar L. under the influence of the nuclear polyhedrosis virus is considered. To assess the sensitivity of insects to the effects of baculoviruses, laboratory experiments were carried out on the mortality of caterpillars under various infectious loads. In this paper, we consider the possibility of constructing a model for the lifetime of insects after exposure to baculoviruses as an analog of a second-order phase transition in physical systems and give estimates of the model parameters for two insect species at different titers of baculoviruses and at different ages of caterpillars. The dependence of the parameters of the proposed model on the nuclear polyhedrosis virus strains is shown. The importance of the applied parameters for the organization of forest protection measures is substantiated. [ABSTRACT FROM AUTHOR]

The gypsy moth, Lymanria dispar, is one of the most widespread pest-insects in the Russian Federation. Anastatus japonicus Ashmead and Ooencyrtus kuvanae Howard are parasites that live on the eggs of L. dispar. They can be found in the European part of Russia, where the insects were imported from North Korea in 1988. The usage of O. kuvanae to limit the gypsy moth populations requires recognition of the release rates and effectiveness in preventing mass pest outbreaks, as well as for the evaluation of the possibility of elimination. An experimental release of O. kuvanae (237 500 specimens) was conducted in 2019 during a gypsy moth outbreak in the Orenburg region, which covered the basin of the Ural River within the territory of three forestries. The average number of clutches of O. kuvanae varied from 1 to 20 clutches per tree. The control of efficiency was made 48–52 after the release, during the incubation period of the 3ed generation of O. kuvanae. The clutches were collected and experimentally analyzed. The release rate of L. dispar ranged 82.9–90.3 % at the locations with a density of 107–268 thousand eggs/ha and did not exceed 47.3 % at the locations with a density of 3800 thousand eggs/ha. A coefficient for estimation of the optimal number of O. kuvanae specimens per 1 ha was proposed based on the proportion of the released egg parasitoids per 1 ha and the absolute number of the destroyed eggs of L. dispar. The regulation of the gypsy moth’s population by O. kuvanae should be done at the biggening of the foci formation. The usage of the entomophage in the active reproductive foci of the gypsy moth, with an infestation rate higher than 1.5 clutches per tree, cannot reduce the phytophage numbers to a harmless level. The application of O. kuvanae can be a part of an integrated system of preventive measures: chemical or biological pesticide treatments to reduce gypsy moth populations, and after initiate the release of the entomophages. For citation: Sergeeva Yu.A., Dolmonego S.O. Application of Ooencyrtus kuvanae Howard Against Gypsy Moth. Lesnoy Zhurnal = Russian Forestry Journal, 2023, no. 3, pp. 69–83. (In Russ.). https://doi.org/10.37482/0536-1036-2023-3-69-83

Abstract The spongy moth, Lymantria dispar, is an irruptive forest pest native to Eurasia where its range extends from coast to coast and overspills into northern Africa. Accidentally introduced from Europe in Massachusetts in 1868–1869, it is now established in North America where it is considered a highly destructive invasive pest. A fine‐scale characterization of its population genetic structure would facilitate identification of source populations for specimens intercepted during ship inspections in North America and would enable mapping of introduction pathways to help prevent future incursions into novel environments. In addition, detailed knowledge of L. dispar's global population structure would provide new insight into the adequacy of its current subspecies classification system and its phylogeographic history. To address these issues, we generated >2000 genotyping‐by‐sequencing‐derived SNPs from 1445 contemporary specimens sampled at 65 locations in 25 countries/3 continents. Using multiple analytical approaches, we identified eight subpopulations that could be further partitioned into 28 groups, achieving unprecedented resolution for this species' population structure. Although reconciliation between these groupings and the three currently recognized subspecies proved to be challenging, our genetic data confirmed circumscription of the japonica subspecies to Japan. However, the genetic cline observed across continental Eurasia, from L. dispar asiatica in East Asia to L. d. dispar in Western Europe, points to the absence of a sharp geographical boundary (e.g., the Ural Mountains) between these two subspecies, as suggested earlier. Importantly, moths from North America and the Caucasus/Middle East displayed high enough genetic distances from other populations to warrant their consideration as separate subspecies of L. dispar. Finally, in contrast with earlier mtDNA‐based investigations that identified the Caucasus as L. dispar's place of origin, our analyses suggest continental East Asia as its evolutionary cradle, from where it spread to Central Asia and Europe, and to Japan through Korea.

Temperature and food quality are the most important environmental factors determining the performance of herbivorous insects. The objective of our study was to evaluate the responses of the spongy moth (formerly known as the gypsy moth) [Lymantria dispar L. (Lepidoptera: Erebidae)] to simultaneous variation in these two factors. From hatching to the fourth instar, larvae were exposed to three temperatures (19 °C, 23 °C, and 28 °C) and fed four artificial diets that differed in protein (P) and carbohydrate (C) content. Within each temperature regime, the effects of the nutrient content (P+C) and ratio (P:C) on development duration, larval mass, growth rate, and activities of digestive proteases, carbohydrases, and lipase were examined. It was found that temperature and food quality had a significant effect on the fitness-related traits and digestive physiology of the larvae. The greatest mass and highest growth rate were obtained at 28 °C on a high-protein low-carbohydrate diet. A homeostatic increase in activity was observed for total protease, trypsin, and amylase in response to low substrate levels in the diet. A significant modulation of overall enzyme activities in response to 28 °C was detected only with a low diet quality. A decrease in the nutrient content and P:C ratio only affected the coordination of enzyme activities at 28 °C, as indicated by the significantly altered correlation matrices. Multiple linear regression analysis showed that variation in fitness traits in response to different rearing conditions could be explained by variation in digestion. Our results contribute to the understanding of the role of digestive enzymes in post-ingestive nutrient balancing. [ABSTRACT FROM AUTHOR]

The spongy moth, Lymantria dispar, is an irruptive forest pest native to Eurasia where its range extends from coast to coast and overspills into northern Africa. Accidentally introduced from Europe in Massachusetts in 1868–1869, it is now established in North America where it is considered a highly destructive invasive pest. A fine‐scale characterization of its population genetic structure would facilitate identification of source populations for specimens intercepted during ship inspections in North America and would enable mapping of introduction pathways to help prevent future incursions into novel environments. In addition, detailed knowledge of L. dispar's global population structure would provide new insight into the adequacy of its current subspecies classification system and its phylogeographic history. To address these issues, we generated >2000 genotyping‐by‐sequencing‐derived SNPs from 1445 contemporary specimens sampled at 65 locations in 25 countries/3 continents. Using multiple analytical approaches, we identified eight subpopulations that could be further partitioned into 28 groups, achieving unprecedented resolution for this species' population structure. Although reconciliation between these groupings and the three currently recognized subspecies proved to be challenging, our genetic data confirmed circumscription of the japonica subspecies to Japan. However, the genetic cline observed across continental Eurasia, from L. dispar asiatica in East Asia to L. d. dispar in Western Europe, points to the absence of a sharp geographical boundary (e.g., the Ural Mountains) between these two subspecies, as suggested earlier. Importantly, moths from North America and the Caucasus/Middle East displayed high enough genetic distances from other populations to warrant their consideration as separate subspecies of L. dispar. Finally, in contrast with earlier mtDNA‐based investigations that identified the Caucasus as L. dispar's place of origin, our analyses suggest continental East Asia as its evolutionary cradle, from where it spread to Central Asia and Europe, and to Japan through Korea. [ABSTRACT FROM AUTHOR]

Simple Summary: Globalization accelerates the mixing of populations, including those of humans, animals and plants. Consequently, some species invade new natural communities and alter them. One illustrative example is the spongy moth, which was accidentally introduced into North America, where it became a major forest pest after its establishment there. In its native Eurasian environment, the spongy moth's range has recently shown significant northward expansion, presumably as a consequence of global warming. In its North American range, a similar northward advance is yet to be fully documented. Eurasian populations of the spongy moth show significant developmental plasticity, which allows them to establish themselves in the much colder northern regions due to an acceleration of larval development. The mechanism responsible for this acceleration is not well understood, but our earlier studies point to genetic and epigenetic factors as playing a role. This plasticity indicates that new introductions of Eurasian spongy moths from the northernmost populations pose a more significant threat to North America than previously expected. The spongy moth, Lymatria dispar, is a classic example of an invasive pest accidentally introduced from Europe to North America, where it has become one of the most serious forest defoliators, as in its native range. The present study was aimed at (i) identifying the current northern limit of L. dispar's Eurasian range and exploring its northward expansion in Canada using pheromone trap data, and (ii) comparing northern Eurasian populations with those from central and southern regions with respect to male flight phenology, the sums of effective temperatures (SETs) above the 7 °C threshold necessary for development to the adult stage, and heat availability. We show that the range of L. dispar in Eurasia now reaches the 61st parallel, and comparisons with historical data identify the average speed of spread as 50 km/year. We also document the northern progression of L. dispar in southern Canada, where the actual northern boundary of its range remains to be identified. We show that the median date of male flight does not vary greatly between northern and southern regions of the spongy moth range in Eurasia despite climate differences. Synchronization of flight at different latitudes of the range is associated with an acceleration of larval development in northern Eurasian populations. Similar changes in developmental rate along a latitudinal gradient have not been documented for North American populations. Thus, we argue that this feature of spongy moths from northern Eurasia poses a significant invasive threat to North America in terms of enhanced risks for rapid northward range expansion. [ABSTRACT FROM AUTHOR]

One of the subspecies of the Eurasian spongy moth, Lymantria dispar asiatica, is a destructive forest pest in native regions and also an important quarantine pest in non-native regions. Its polyphagous nature, together with occasional outbreaks, may seriously threaten ecosystems and result in costly management programs. In this study, we examined the effect of chilling temperatures (−12, −6, 0, 6, and 12 °C) during the diapause phase on the survival and post-diapause development of L. d. asiatica eggs, collected before winter, in order to characterize their thermal response. The eggs were exposed to treatment temperatures for 100 days, followed by 25 °C incubation to determine their survival and development time. The eggs hatched in all the treatments, indicating that all the examined conditions could partly or sufficiently satisfy the thermal requirement for eggs to enter post-diapause development. However, exposure to chilling temperatures significantly affected both the survival and development times of overwintering eggs in a given temperature range. The survival rates declined at −12 °C, and the development rates accelerated as the chilling temperature increased. This information could offer clues for the assessment of the outbreak potential in native regions and the possibility of range expansion in non-native regions through the consideration of winter conditions that favor L. d. asiatica egg hatching and their subsequent development. [ABSTRACT FROM AUTHOR]

Abstract Remote sensing imagery can provide critical information on the magnitude and extent of damage caused by forest pests and pathogens. However, monitoring short‐term changes in deciduous forest condition caused by defoliating insects is challenging and requires approaches that directly account for seasonal vegetation dynamics. We implemented a previously published harmonic modeling approach for forest condition monitoring in Google Earth Engine and systematically assessed the relative ability of condition change products generated using various model parameterizations for predicting pest abundances and defoliation during the 2016–2018 gypsy moth (Lymantria dispar) outbreak in southern New England. Our comparisons revealed that most models made reasonable predictions of changes in canopy condition and egg and larval abundances of L. dispar, indicating a strong correlation between our harmonic‐based estimates of condition change and defoliator activity. The greatest differences in predictive ability were in the spectral domain, with assessments based on Tasseled Cap Greenness, Simple Ratio, and the Enhanced Vegetation Index ranking among the top models, and the commonly used Normalized Difference Vegetation Index consistently exhibiting poorer performance. We also observed notable differences in the magnitude of scores for different baseline periods. Additionally, we found that Landsat‐based condition scores better explained larval abundance than egg mass counts, which have historically been used as a proxy for later‐season larval abundance, indicating that our remote sensing approach may be more accurate and cost‐effective for generating consistent retrospective assessments of L. dispar population abundance in addition to estimates of canopy damage. These findings provide important linkages between spectral changes detected using a harmonic modeling approach and biophysical aspects of defoliator activity, with potential to extend monitoring and prediction to regional or even continental scales.

Simple Summary: The spongy moth (SM) lives in the temperate latitudes of Europe and Asia, as well as in North America (as an invasive species). Caterpillars of the spongy moth feed on tree leaves. They cause significant economic damage, as they lead to the defoliation of trees over vast areas. Studies of the ecology of the spongy moth are necessary to predict possible outbreaks of this insect, as well as to develop effective methods for controlling their numbers. In North America, where the SM is an invasive species, its range is still expanding. Therefore, it is vitally important to build adequate models that will help predict the regions where the SM may appear in the future. The results of our study of Asian SM populations suggest another possible pathway for the SM to spread in the forests of North America. It turns out that the temperature of the rock surface, where the spongy moth lays eggs overwinter, is significantly higher than the temperature of the winter air. Therefore, insects (or their eggs) wintering on rocks can survive colder winter air temperatures than their physiology allows. These results help to reassess the role of the mountain landscape in the spread of insect species. Many insect species overwinter in various rock shelters (cavities and crevices), but the microclimates of rock biotopes remain poorly understood. We investigated the temperature dynamics in rock microhabitats where clusters of egg masses of the wintering spongy moth Lymantria dispar L. (SM) were observed. Our research objective was to find the relation between the ovipositing behaviour of females and the landscape features in different parts of this species' range. Studies of the ecology of the SM are important from a practical point of view, as the moth causes significant economic damage to forests of the Holarctic. We found that the average monthly temperature of rock surfaces in the studied microhabitats was 2–5 °C above the average air temperature. More importantly, the minimum temperatures in these microhabitats were 4–13 °C higher than the minimum air temperature. These results help to reassess the role of the mountain landscape in the spread of insect species. Rock biotopes provided a significant improvement in the conditions for wintering insects. We believe that, when modelling the spread of invasive species (such as the SM), it is necessary to account for the influence of rock biotopes that may facilitate shifts in the northern boundaries of their range. [ABSTRACT FROM AUTHOR]

Temperature and food quality are the most important environmental factors determining the performance of herbivorous insects. The objective of our study was to evaluate the responses of the spongy moth (formerly known as the gypsy moth) [Lymantria dispar L. (Lepidoptera: Erebidae)] to simultaneous variation in these two factors. From hatching to the fourth instar, larvae were exposed to three temperatures (19 °C, 23 °C, and 28 °C) and fed four artificial diets that differed in protein (P) and carbohydrate (C) content. Within each temperature regime, the effects of the nutrient content (P+C) and ratio (P:C) on development duration, larval mass, growth rate, and activities of digestive proteases, carbohydrases, and lipase were examined. It was found that temperature and food quality had a significant effect on the fitness-related traits and digestive physiology of the larvae. The greatest mass and highest growth rate were obtained at 28 °C on a high-protein low-carbohydrate diet. A homeostatic increase in activity was observed for total protease, trypsin, and amylase in response to low substrate levels in the diet. A significant modulation of overall enzyme activities in response to 28 °C was detected only with a low diet quality. A decrease in the nutrient content and P:C ratio only affected the coordination of enzyme activities at 28 °C, as indicated by the significantly altered correlation matrices. Multiple linear regression analysis showed that variation in fitness traits in response to different rearing conditions could be explained by variation in digestion. Our results contribute to the understanding of the role of digestive enzymes in post-ingestive nutrient balancing.

Lymantria dispar (Lepidoptera: Erebidae) is a significant defoliator both in its native and introduced regions. To better monitor and predict outbreaks for appropriate management of L. dispar , we estimated the defoliation distribution by L. dispar and performed nonlinear time-series forecasting of the vegetation anomaly dynamics. The Normalized Difference Vegetation Index (NDVI) obtained from Sentinel-2 was utilized to detect defoliation of the forests in the Altai Republic of Western Siberia. During the L. dispar outbreak in 2017, forest defoliation was captured by at two sites. The difference between NDVI in defoliated sites and seasonal NDVI was compared to characterize the NDVI dynamics of L. dispar defoliation. Results show that the NDVI of the two defoliated sites decreased by −0.101 and −0.087 during the season, respectively. The spatial distribution (100 m resolution) of the defoliation using NDVI showed a decreasing trend from 2017 to 2021. It showed heavy defoliation with a maximum of 10 % of the forest area from 2017 to 2018, in contrast to forest recovery in subsequent years. The defoliation was influenced by topographic factors, which occurred at relatively low elevations (916–1466 m) along roadways and open slopes. The NDVI model was built with dynamic mode decomposition (DMD) to represent the spatiotemporal dynamics of normal vegetation changes. The negative deviations between observed NDVI and the DMD-predicted NDVI then indicated anomalous vegetation changes such as defoliation by L. dispar. The study area's vegetation anomaly dynamics were forecasted using the local manifold distance-based regression (LMDr), a nonlinear forecasting technique that employs the state space reconstruction technique. The nonlinear time-series model demonstrated the best forecasting skill (ρ = 0.612) with the embedding (time-delay) dimension E = 11, suggesting the potential for anomaly detection and outbreak forecasting by the model. The study provided a good monitoring and forecasting framework for L. dispar defoliation in native ranges by combining a high-resolution imagery dataset with nonlinear anomaly detection. • Defoliation by Lymantria dispar was detected using NDVI from Sentinel-2. • NDVI decreases in the season showed defoliation in outbreak years. • Defoliation was influenced by elevation and slope. • The vegetation anomaly was forecasted by the nonlinear time-series model. • Satellite monitoring and predictive defoliation model provide pest management tools. [ABSTRACT FROM AUTHOR]

This study evaluated the efficacy of the commercially available insecticide Lepidocide based on Bacillus thuringiensis var. kurstaki and Lymantria dispar multiple nucleopolyhedrovirus (LdMNPV) and their combination with an optical brightener to control L. dispar L. Efficacy against both second and fourth instar L. dispar larvae was evaluated, and the type of interaction between the tested components was determined using second instar L. dispar larvae. Most combinations of Lepidocide and LdMNPV containing a 5 mg ml−1 optical brightener had synergistic effects, and their mixtures were most effective in reducing the number of second instar larvae. In contrast, mixtures containing Lepidocide and LdMNPV with an optical brightener caused significantly lower mortality of fourth instar L. dispar larvae than mixtures without Lepidocide. This result suggests that an increased concentration of Lepidocide in a mixture containing LdMNPV and an optical brightener leads to an antagonistic effect on insect mortality. The possible reasons for the differences in the observed effects of the components on the second and fourth instar L. dispar larvae may be associated with the resistance of fourth-instar larvae to the antifeedant effect of B. thuringiensis. [ABSTRACT FROM AUTHOR]

The population dynamics and impacts of non-native species often change following their initial establishment, with impacts either increasing or decreasing over time. The reasons why the abundance of an invading species may change are varied but often reflect changes in the way in which populations interact with resident communities. Here we analyze changes in the outbreak dynamics of Lymantria dispar (formerly known to as the "gypsy moth"), a Eurasian foliage-feeding insect that has been established in N. America for ca. 150 years. We find that during the course of this species' presence in N. America, it has continually exhibited population dynamics in which populations reach outbreak levels, resulting in defoliation of large forested areas. However, there is evidence of some changes in both the periodicity and synchrony of these outbreaks. We hypothesize that the accidental introduction of an entomopathogenic nucleopolyhedrosis virus around 1906 resulted in populations shifting from a pattern of sustained outbreaks to oscillatory dynamics with periodic outbreaks synchronized over large distances. We analyze historical L. dispar population data that provide some evidence in support of this hypothesis. There is also evidence that the more recent establishment of the fungal pathogen Entomophaga maimaiga has caused a decrease in the amplitude of L. dispar outbreaks since its emergence in 1989. [ABSTRACT FROM AUTHOR]

Hughes and Madden's binary power law was used to analyse sample data of three life stages of gypsy moth (Lymantria dispar) and adult emerald ash borer (Agrilus planipennis), both important invasive forest pests in North America.Tally thresholds were used to convert quantitative gypsy moth data to binomial, presence–absence data for binary power law analysis.Presence–absence data from two emerald ash borer surveys were analysed, an initial highly intensive and expensive survey expanding out from the point of introduction in Michigan and a second extensive survey designed to detect and track the leading edge of the beetle's expanding range.Emerald ash borer was found to be moderately aggregated in the initial survey data, but very near to random in the leading edge survey. The latter result is consistent with other findings that spatial distribution is less aggregated at range edges than near the centre of the range.Estimates of the proportion of positive observations in the initial intensive survey were found to be more precise than those obtained in the leading edge survey.Comparisons of binomial power law estimates and Taylor's power law estimates of the gypsy moth data suggest the possibility of a fundamental connection between the two power laws. A possible connection, the effect of tally thresholds and their relationship with sampling efficiency are discussed. [ABSTRACT FROM AUTHOR]

Quantifying tree defoliation by insects over large areas is a major challenge in forest management, but it is essential in ecosystem assessments of disturbance and resistance against herbivory. However, the trajectory from leaf‐flush to insect defoliation to refoliation in broadleaf trees is highly variable. Its tracking requires high temporal‐ and spatial‐resolution data, particularly in fragmented forests.In a unique replicated field experiment manipulating gypsy moth Lymantria dispar densities in mixed‐oak forests, we examined the utility of publicly accessible satellite‐borne radar (Sentinel‐1) to track the fine‐scale temporal trajectory of defoliation. The ratio of backscatter intensity between two polarizations from radar data of the growing season constituted a canopy development index (CDI) and a normalized CDI (NCDI), which were validated by optical (Sentinel‐2) and terrestrial laser scanning (TLS) data as well by intensive caterpillar sampling from canopy fogging.The CDI and NCDI strongly correlated with optical and TLS data (Spearman's ρ = 0.79 and 0.84, respectively). The ΔNCDIDefoliation(A‐C) significantly explained caterpillar abundance (R2 = 0.52). The NCDI at critical timesteps and ΔNCDI related to defoliation and refoliation well discriminated between heavily and lightly defoliated forests.We demonstrate that the high spatial and temporal resolution and the cloud independence of Sentinel‐1 radar potentially enable spatially unrestricted measurements of the highly dynamic canopy herbivory. This can help monitor insect pests, improve the prediction of outbreaks and facilitate the monitoring of forest disturbance, one of the high priority Essential Biodiversity Variables, in the near future. [ABSTRACT FROM AUTHOR]

Abstract Insect outbreaks often occur in the absence of natural enemies and in the presence of excess suitable host materials. Outbreaks of gypsy moths are especially problematic in remote areas located in high-latitude regions in Japan because the majority of adults emerge during the short summer season and initiate synchronous mass flight toward artificial lights. The aggregation of moths in public facilities not only is an annoyance to visitors but also permits the establishment of new populations the following year. The aim of this study was to establish a method to reduce the numbers of large moths that are attracted to lights in the rest areas of expressways in Hokkaido based on the results of research on their behavioral ecology and physiology. First, we conducted extensive insect surveys using light traps that emit light at different wavelengths; the traps were set along the expressways in the summers of 2014–2018. The insects attracted to the light were roughly classified into those showing a preference for broadband light wavelengths (from UV-A to green) and short light wavelengths (from UV-A to blue). The former included aquatic insects and winged ants, and the latter included moths and beetles. Next, we analyzed correlations between moth emergence and daily meteorological data. When gypsy moths were abundant during an outbreak, the daily catch of gypsy moths was positively correlated with the highest ambient temperature on the catch day but not with the visibility range, wind speed, or moon phase. In contrast, the daily catch of oak silkmoths did not correlate with any of these parameters. Our results provide guidance for the management of forest insects inhabiting cool-temperate to subarctic regions based on light wavelengths with reference to weather variables.

The gypsy moth, Lymantria dispar (L.), and the tent caterpillar, Malacosoma neustrium (L.), are the main cork oak, Quercus suber L., pests in the Mediterranean area and cause complete defoliation in large forest districts. In order to control infestations, large scale aerial applications of insecticides based on Bacillus thuringiensis subsp. kurstaki (Btk) have been carried out in Sardinia (Italy) since 2001. This paper evaluated the frequency of outbreaks in forest districts with varying homogeneity of land use, forest areas annually exposed to defoliation and the effectiveness of control programs based on Btk insecticide applications. The volume of areas annually exposed to defoliation depends on forest homogeneity, as infestations are more frequent in cork oak areas with a lower than 25% canopy cover rate. The microbiological control programme efficiently protected cork oaks from lepidopteran defoliators and caused an overall annual mean mortality of over 60%, with maximum rates of 89.9 and 98.0% for L. dispar and M. neustrium, respectively. To date, approximately 180,000 hectares of cork oak forests have been protected by spraying Btk-based insecticides.

The spongy moth, Lymatria dispar, is a classic example of an invasive pest accidentally introduced from Europe to North America, where it has become one of the most serious forest defoliators, as in its native range. The present study was aimed at (i) identifying the current northern limit of L. dispar’s Eurasian range and exploring its northward expansion in Canada using pheromone trap data, and (ii) comparing northern Eurasian populations with those from central and southern regions with respect to male flight phenology, the sums of effective temperatures (SETs) above the 7 °C threshold necessary for development to the adult stage, and heat availability. We show that the range of L. dispar in Eurasia now reaches the 61st parallel, and comparisons with historical data identify the average speed of spread as 50 km/year. We also document the northern progression of L. dispar in southern Canada, where the actual northern boundary of its range remains to be identified. We show that the median date of male flight does not vary greatly between northern and southern regions of the spongy moth range in Eurasia despite climate differences. Synchronization of flight at different latitudes of the range is associated with an acceleration of larval development in northern Eurasian populations. Similar changes in developmental rate along a latitudinal gradient have not been documented for North American populations. Thus, we argue that this feature of spongy moths from northern Eurasia poses a significant invasive threat to North America in terms of enhanced risks for rapid northward range expansion.

Remote sensing imagery can provide critical information on the magnitude and extent of damage caused by forest pests and pathogens. However, monitoring short‐term changes in deciduous forest condition caused by defoliating insects is challenging and requires approaches that directly account for seasonal vegetation dynamics. We implemented a previously published harmonic modeling approach for forest condition monitoring in Google Earth Engine and systematically assessed the relative ability of condition change products generated using various model parameterizations for predicting pest abundances and defoliation during the 2016–2018 gypsy moth (Lymantria dispar) outbreak in southern New England. Our comparisons revealed that most models made reasonable predictions of changes in canopy condition and egg and larval abundances of L. dispar, indicating a strong correlation between our harmonic‐based estimates of condition change and defoliator activity. The greatest differences in predictive ability were in the spectral domain, with assessments based on Tasseled Cap Greenness, Simple Ratio, and the Enhanced Vegetation Index ranking among the top models, and the commonly used Normalized Difference Vegetation Index consistently exhibiting poorer performance. We also observed notable differences in the magnitude of scores for different baseline periods. Additionally, we found that Landsat‐based condition scores better explained larval abundance than egg mass counts, which have historically been used as a proxy for later‐season larval abundance, indicating that our remote sensing approach may be more accurate and cost‐effective for generating consistent retrospective assessments of L. dispar population abundance in addition to estimates of canopy damage. These findings provide important linkages between spectral changes detected using a harmonic modeling approach and biophysical aspects of defoliator activity, with potential to extend monitoring and prediction to regional or even continental scales. [ABSTRACT FROM AUTHOR]

Based on the long-term laboratory rearing of gypsy moth larvae on an artificial diet with different modifications, which were taken from egg masses in the same forest area in different phases of the population dynamics, we have studied the effect of biotic and abiotic factors on the duration of the development and survival rate of larvae at younger instars in the group- and solitary-rearing regimes. It is shown that the duration of larval development at younger instars is influenced by the sum of effective temperatures at the early embryonic stage of development, as well as by the duration of embryo exposure to temperatures below the developmental threshold and by the food composition. The effect of the group rearing regime (group effect) on the rate of larval development is associated with the population dynamics phase; its most significant positive effect has been recorded in the eruptive period. It has been revealed that the response of larvae to the food composition through the development duration differs in different rearing regimes, depending on the population density phase. With respect to the food composition, the group effect can be determined both by the acceleration of larval development in the group regime and by the deceleration of larval development in the solitary rearing regime. The studied effects have been quantitatively assessed. [ABSTRACT FROM AUTHOR]

BACKGROUND: Treatments for the suppression and eradication of insect populations undergo substantial testing to ascertain their efficacy and safety, but the generally limited spatial and temporal scope of such studies limit knowledge of how contextual factors encountered in operational contexts shape the relative success of pest management treatments. These contextual factors potentially include ecological characteristics of the treated area, or the timing of treatments relative to pest phenology and weather events. We used an extensive database on over 1000 treatments of nascent populations of Lymantria dispar (L.) (gypsy moth) to examine how place‐based and time‐varying conditions shape the success of management treatments. RESULTS: We found treatment success to vary across states and years, and to be highest in small treatment blocks that are isolated from other populations. In addition, treatment success tended to be lower in treatment blocks with open forest canopies, possibly owing to challenges of effectively distributing treatments in these areas. CONCLUSIONS: Our findings emphasize the importance of monitoring for early detection of nascent gypsy moth colonies in order to successfully slow the spread of the invasion. Additionally, operations research should address best practices for effectively treating with patchy and open forest canopies. © 2021 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]