Gypsy Moth Research Articles

Development of Enumerative and Binomial Sequential Sampling Plans for Monitoring Lymantria dispar (L.) (Lepidoptera Erebidae) in Mediterranean Oak Forests

Lymantria dispar is the main threat to Mediterranean forests. Sampling methods used for monitoring the pest population density are generally very time-consuming for practical purposes, such as the delimitation of infested areas for control programs. Enumerative and binomial sequential sampling plans were developed using data collected in cork oak forests in Sardinia (Italy). The Taylor’s power law (TPL) was used to evaluate the degree of aggregation of L. dispar egg masses among trees and to develop enumerative sampling plans at precision levels of 0.10 and 0.25 using the Green’s method. Furthermore, binomial plans were computed by Wald’s sequential probability ratio test. Lymantria dispar egg masses on trees were significantly aggregated and the degree of aggregation was similar in all population development phases. Overall, only 31 cork oak trees are to be monitored at the economic damage threshold of 2.5 egg masses/tree with a precision level of 0.25. Binomial sequential sampling plans also required lower sampling sizes (26.9–31.4 trees) than conventional sampling plans. Enumerative and binomial sampling plans could represent suitable methods for sampling L. dispar egg masses in Mediterranean forests, with the practical advantage of lower cost and time consumption than standard sampling plans.

Lymantria dispar, the spongy moth distribution, and global climate data and weather data of South Korea

Lymantria dispar, the spongy moth distribution, and global climate data and weather data of South Korea

Spread rates do not necessarily predict outbreak dynamics in a broadly distributed invasive insect

Biological invasions by insects entail several processes including spread and outbreaks that can cause widespread tree mortality. These processes are commonly viewed as a linear sequence because we often lack the mechanistic understanding needed to partition them. We explored an invasion that occurred over a large enough spatial scale and time frame to examine the conditions under which spread rates may be uncoupled from outbreak severity. Lymantria dispar is an invasive generalist folivore that has spread continuously from its initial point of introduction in North America at variable rates. Since its establishment in Wisconsin, USA in 1998, L. dispar has spread more rapidly there than any other region, but has never irrupted into regionwide outbreaks. In contrast, L. dispar spread more slowly elsewhere, in part due to strong mate-finding Allee effects, but periodically undergoes highly damaging, landscape-scale outbreaks in susceptible forest types. We conducted a 10-year study across 45 stands in northern Wisconsin with a high composition of favorable hosts. We quantified population trends of life stages, natural enemy abundance and impacts, and radial tree growth increment, and assessed biotic and abiotic factors as putative drivers of the decoupling between spread rates and outbreak severity. We then compared the results from these rapid-spread, low-impact sites with those from slow-spread, high-impact sites in Michigan and Pennsylvania, USA. The abundance and richness of natural enemy communities in Wisconsin were either equivalent to or less than those communities reported elsewhere, reducing the likelihood that greater top-down control explains the absence of outbreaks. We also found no differences in larval developmental time or drought that could increase the effects of natural enemies among the different regions. Rather, higher overwintering mortality due to more extreme and frequent lethal minimal temperatures in Wisconsin appeared most responsible for the lack of outbreaks. Overall, it appears that the combination of strong mate-finding Allee effects and low overwintering mortality elsewhere is a more substantial hindrance to spread than are weak mate-finding Allee effects and high overwintering mortality in Wisconsin. Once populations are established, the net contributions of these constraints become reversed: mate-finding limitations become only a minimal challenge whereas regional differences in winter survival best explain differences in outbreak frequency. These results suggest that spread rates of invasive insects should not be used as a proxy for predicting their local or overall impact, and that management efforts should be tailored to underlying processes determining their region-specific relative importance.

Unraveling arbuscular mycorrhizal fungi-induced resistance of purple branch rose (Rosa rugosa ‘Zizhi’) to Lymantria dispar based on metabolomics

Currently, people primarily rely on chemical pesticides to prevent and control insect pests, which not only introduce problems with environmental pollution but also produce chemical residues that will make it difficult to guarantee the safety of edible plants. Arbuscular mycorrhizal fungi (AMF) are soil microorganisms that form a symbiotic relationship with plants, which improves plant resistance. This natural phenomenon provides new ideas for eco-friendly biological control. The present study assessed the effects of AMF (Funneliformis mosseae, Rhizophagus intraradices and their combination) inoculation on rose growth and its resistance to gypsy moth larvae (Lymantria dispar) by investigating the growth performance and metabolomics of rose plants and the growth and physiological parameters of gypsy moth larvae. AMF inoculation improved the growth of both the aboveground and belowground parts of the rose plants. The developmental duration of gypsy moth larvae feeding on mycorrhizal rose leaves was prolonged by 4.8–5.8 days. Moreover, feeding on mycorrhizal rose leaves significantly reduced the body weight of the gypsy moth larvae by 9–24%, body length by 4–6%, and the width of head sheath by 11–15%. The superoxide dismutase (SOD) and carboxylesterase (CarE) enzymes in the larvae that fed on the leaves of mycorrhizal rose were significantly higher than those in the control, while the acid phosphatase (ACP) was inhibited (P < 0.05). Peroxidase (POD) and alkaline phosphatase (AKP) in larvae that fed on mycorrhizal rose leaves were significantly higher than those in the control at 5 days. Glutathione S transferases (GSTs) were significantly higher than the control at 3 and 5 days. Metabolomics analyses showed that inoculation with AMF promoted the accumulation of jasmonic acid (JA) and abscisic acid (ABA) in rose leaves. The treatment groups were 1.6- and 3.4-fold higher than those of the control, respectively. The AMF significantly regulated 1,589 metabolites in rose leaves. The AMF promoted the accumulation of flavonoids and inhibited the accumulation of glycosides in rose leaves. A total of 19 metabolites that significantly correlated with the growth and development of gypsy moths were screened out. Among ABA, glycerophosphocholine, 1-(sn-glycero-3-phospho)-1D-myo-inositol, (-)-catechin, N-acetyl-D-glucosamine 6-phosphate, 3-(4-hydroxyphenyl)-1-propanol and 3-trans-caffeoyltormentic acid were significantly different from those of the control. These compounds may play a role in the resistance of rose to gypsy moth induced by AMF. In conclusion, AMF inoculation improved the resistance of R. rugosa to L. dispar through modifications on the metabolism and physiology. These findings highlight the interaction of “mycorrhizal-plant-insect”. It provides a reference for the application of AMF to control plant pest.

Cd exposure-triggered susceptibility to Bacillus thuringiensis in Lymantria dispar involves in gut microbiota dysbiosis and hemolymph metabolic disorder

The immunotoxicity induced by heavy metals on herbivorous insects reflect the alterations of the susceptibility to entomopathogenic agents in herbivorous insects exposed to heavy metal. In the present study, the susceptibility of gypsy moth larvae to Bacillus thuringiensis under Cd treatment at low and high dosages was investigated, and the gut microbiome-hemolymph metabolome responses that affected larval disease susceptibility caused by Cd exposure were examined. Our results showed that mortality of gypsy moth larvae caused by B. thuringiensis was significantly higher in larvae pre-exposed to Cd stress, and there was a synergistic effect between Cd pre-exposure and bacterial infection. Exposure to Cd significantly decreased the abundance of several probiotics (e.g., Serratia for the low Cd dosage and Weissella, Aeroonas, and Serratia for the high Cd dosage) and increased the abundances of several pathogenic bacteria (e.g., Stenotrophomonas, Gardnerella, and Cutibacterium for the low Cd dosage and Pluralibacter and Tsukamurella for the high Cd dosage) compared to the controls. Moreover, metabolomics analysis indicated that amino acid biosynthesis and metabolism were significantly perturbed in larval hemolymph under Cd exposure at both the low and high dosages. Correlation analysis demonstrated that several altered metabolites in larval hemolymph were significantly correlated with changes in the gut microbial community. The results demonstrate that prior exposure to Cd increases the susceptibility of gypsy moth larvae to B. thuringiensis in a synergistic fashion due to gut microbiota dysbiosis and hemolymph metabolic disorder, and thus microbial-based biological control may be the best pest control strategy in heavy metal-polluted areas.

Management of Nuisance Macromoths in Expressways through Academic-Industrial Collaboration: Light Trap Designed on the Basis of Moths' Preferences for Light Attributes.

Aggregation of flying insects such as gypsy moths at commercial light sources in summer not only has an aesthetically negative impact on public facilities but also permits the establishment of new insect populations there from the next year. Although energy-efficient light traps equipped with light-emitting diodes (LEDs) have recently been used for controlling pest insects in agriculture, there are very few maintenance-free light traps that are available on the market. Based on the results of field surveys, we fabricated a prototype light trap in which the preferences of insects for light irradiation angle and wavelength are implemented. Field experiments revealed that flying moths were attracted more to light with a narrow irradiation angle than to light with a wide irradiation angle. Moreover, there was a tendency for fewer moths to be collected when fluorescent paint was applied to the surface of the flight-interception board, indicating that a high contrast made by illumination and the background is preferred by flying moths. Taken together with our previous results, we found that the moth catch was influenced more by modification of the light design than by change in visible light wavelengths. A semi-portable light trap, named the "Kurihara trap" after the primary contributor to its development, is made of light-weight plastic and is driven by solar power. This light trap is omnidirectional and maintenance-free and is therefore suitable for deployment in the backyards of rest areas as well as at houses for long-term macromoth sampling.

RNAi-based functional analysis of bursicon genes related to wing expansion in gypsy moths

Bursicon is a heterodimeric neuropeptide composed of Burs-α and Burs-β subunits that plays an important role in cuticle tanning and wing expansion in insects. In this study, full-length cDNAs of Burs-α (LdBurs-α) and Burs-β (LdBurs-β) genes were identified in gypsy moth (Lymantria dispar) and cloned. The 480 bp and 420 bp open reading frames (ORFs) encode 159 and 129 amino acid polypeptides, respectively. LdBurs-α and LdBurs-β have 11 conserved cysteine residues, and LdBurs-α and LdBurs-β genes were expressed during all developmental stages according to quantitative reverse transcription PCR (qRT-PCR), with highest expression in the egg stage. High expression levels were also detected in the haemolymph, cuticle and head. To explore the physiological functions of LdBurs-α and LdBurs-β, the genes were knocked down in larvae and pupae using RNA interference (RNAi), and expression levels of LdBurs-α and LdBurs-β were decreased by 42.26–80.09%. Wing defects were observed in L. dispar pupae following Ldbursion silencing, with a phenotypic percentage ranging from 10.17% to 15.00%. RNAi-mediated knockdown of Ldbursicon prevented the expansion of male and female L. dispar adult wings, with malformation rates ranging from 6.38% and 30.00% to 57.69% and 69.23%, but no cuticle tanning defects were observed in pupae or adults. The results indicate that bursicon plays a key role in wing expansion in L. dispar adults, making it a potentially novel molecular target for insecticide-based control of this pest species.

The immunotoxicity of Cd exposure to gypsy moth larvae: An integrated analysis of cellular immunity and humoral immunity

Heavy metal exposure-triggered growth retardation and physiology disorder in phytophagous insects have been widely understood, but only a few studies have investigated its immunomodulatory effects on herbivorous insects. Here, the innate immunity of gypsy moth (Lymantria dispar) larvae under Cd stress was evaluated by integrating cellular and humoral immunity, and the immunomodulation mechanism of Cd stress was further understood by the proteomics analysis of larval hemolymph. Our results showed that the total hemocyte count, as well as phagocytic, encapsulation and bacteriostatic activity, of hemolymph in gypsy moth larvae exposed to Cd stress was significantly lower than that in un-treated larvae. Further proteomic analysis revealed that Cd exposure may reduce the total hemocyte count in larval hemolymph by inducing endoplasmic reticulum pathway-mediated hemocyte apoptosis, thereby causing the collapse of cellular immunity in gypsy moth larvae. In addition, the transcriptional level of signal transduction genes (IMD, Toll, Relish, JAK and STAT) and antimicrobial peptide genes (cecropin and lebocin), as well as the protein abundance of pattern recognition receptors (PGRP and GNBP3) in the Toll, IMD and JAK/STAT signaling pathways was significantly decreased in Cd-treated larvae, clearly implying an immunosuppresive effect of Cd stress on pathogen recognition, signal transduction and effector synthesis of humoral immunity in gypsy moth larvae. Taken together, these results suggest that Cd exposure decreases both cellular immunity and humoral immunity of gypsy moth larvae, and provides a new entry point for systematically and comprehensively unraveling the heavy metal pollutants-caused immunotoxicity.

Феромонный мониторинг вредителей леса в условиях Бирского района Республики Башкортостан

In the Republic of Bashkortostan, the gypsy moth (Lymantria Dispar) periodically causes economic damage, in order to monitor it in the conditions of the Birsky district, glue traps with dispensers containing artificial sex pheromone cis-7,8-epoxy-2-methyloctadecane or (+)-disparlure, which was synthesized by the laboratory of insect bioregulators of the Ufa Institute of Chemistry of the Ufa Academy of Sciences, were used. During May-June 2021, it was found that traps with dispensers attract harmful insects compared to untreated controls. Traps with pheromones are not toxic, but warning labels were used to preserve them. A monitoring program with the use of a disparlure is proposed to detect populations, assess their density and select the optimal timing of treatment with pesticides, which will significantly reduce the environmental burden on the environment and preserve beneficial insects. Keywords: GYPSY MOTH LYMANTRIA DISPAR, FOREST PROTECTION, PHEROMONE PREPARATION DISPARLUR, PHEROMONE TRAPS

Functional characterization of a diuretic hormone receptor associated with desiccation, starvation and temperature tolerance in gypsy moth, Lymantria dispar

Variety of diuretic hormone neuropeptides is known to regulate water and ion balance in invertebrates. By activating their specific neuropeptide, diuretic hormone receptor (DHR) transmits extracellular signals into the cell, and then produces functional cell activity, which plays an important role in regulating physiology and behavior. However, little is known about the function of DHR gene in Lymantria dispar. DHR gene was firstly identified in L. dispar and its physiological functions were investigated using RNA interference (RNAi) technology. The results showed that except for the 6th instar larvae, the expression levels of DHR gene in the larval stages are higher than that in the egg, pupal and adult stages. The DHR gene is highly expressed in hindgut and midgut tissues. The L. dispar larvae significantly increased their water content and high temperature tolerance after the DHR was silenced, while decreasing excretion and feeding behavior. The physiological function of DHR is associated with desiccation, high temperature and starvation resistance. DHR could contribute to future development of novel insecticide to manage this global forest pest population.

Outbreaks of Lymantria dispar (L.) in Tyva, Research History

The gypsy moth Lymantria dispar (L., 1758) is a widespread and damaging forest pest in the Republic of Tyva. Outbreaks of the phytophage lead to chronic weakening of trees and reduction in their growth and seed germination capacity. From 1950 to 2004, studies of gypsy moth in Tyva were carried out by researchers taking part in forest health surveys headed by such scientists as O. A. Kataev, V. P. Grechkin, G. I. Golutvin, V. A. Sevastyanyuk, N. I. Berdnikov, V. V. Popov, A. A. Liberman, and others. The researchers have described the phenology of the gypsy moth and its regional morphological and bioecological features. The present work attempts, based on the generalization of the accumulated data on gypsy moth in Tyva, to restore the chronology of pest outbreaks, show their spatial coverage, and propose approaches to their reconstruction over a longer period in the Republic of Tyva. The results of the study showed that in Tyva, four outbreaks of gypsy moth, which occurred in 1950, 1969–1983, 1993–2004, and 2018, were detected. Outbreaks were of a protracted nature and simultaneously covered up to 80 % of forest districts (in some years, the area affected by the pest reached half a million hectares or more). The most intense outbreaks were observed in the central part of the Republic, in the warm conditions of larch and birch forests – in the Kaa-Khem, Tandinsky, Tes-Khem, and Shagonarsky forest districts

Assessing drivers of localized invasive spread to inform large-scale management of a highly damaging insect pest.

Studies of biological invasions at the macroscale or across multiple scales can provide important insights for management, particularly when localized information about invasion dynamics or environmental contexts is unavailable. In this study, we performed a macroscale analysis of the roles of invasion drivers on the local scale dynamics of a high‐profile pest, Lymantria dispar dispar L., with the purpose of improving the prioritization of vulnerable areas for treatment. Specifically, we assessed the relative effects of various anthropogenic and environmental variables on the establishment rate of 8010 quadrats at a localized scale (5 × 5 km) across the entire L. dispar transition zone (the area encompassing the leading population edge, currently from Minnesota to North Carolina). We calculated the number of years from first detection of L. dispar in a quadrat to the year when probability of establishment of L. dispar was greater than 99% (i.e., waiting time to establishment after first detection). To assess the effects of environmental and anthropogenic variables on each quadrat's waiting time to establishment, we performed linear mixed‐effects regression models for the full transition zone and three subregions within the zone. Seasonal temperatures were found to be the primary drivers of local establishment rates. Winter temperatures had the strongest effects, especially in the northern parts of the transition zone. Furthermore, the effects of some factors on waiting times to establishment varied across subregions. Our findings contribute to identifying especially vulnerable areas to further L. dispar spread and informing region‐specific criteria by invasion managers for the prioritization of areas for treatment.

Cd exposure-triggered metabolic disruption increases the susceptibility of Lymantria dispar (Lepidoptera: Erebidae) larvae to Mamestra brassicae nuclear polyhedrosis virus: A multi-omics study

Biological control is an environmentally friendly and effective pest control strategy, but it is often affected by a variety of abiotic factors in the pest control area. Here, the susceptibility of gypsy moth larvae to Mamestra brassicae nuclear polyhedrosis virus (MbNPV) under Cd treatment at the low and high dosages was investigated, and the mechanism of Cd stress affecting virus susceptibility of gypsy moth larvae was analyzed from a metabolic perspective by combining transcriptome and metabolome of the larval fat body. Our results showed that the mortality of MBNPV infection on gypsy moth larvae pre-exposed to Cd was significantly higher than that of larvae without Cd pre-exposure, and the joint effects of Cd exposure and virus infection on larval mortality were demonstrated to be synergistic. Transcriptome analysis revealed that amino acid and carbohydrate transport and metabolism accounted for most of the differently expressed genes in the low Cd and high Cd treatment groups. Consistent with the transcriptome results, metabolome analysis also showed that most metabolites affected by Cd exposure were involved in amino acid and carbohydrate metabolism. Function analysis showed that the contents of several amino acids (e.g. tryptophan and tyrosine) with antioxidant properties were significantly increased in Cd-treated gypsy moth larvae. Taken together, Cd exposure as an environmental factor, promotes the susceptibility of gypsy moth larvae to MbNPV, and metabolic disruption, especially amino acids and carbohydrates-related metabolism, is responsible for the increased susceptibility of gypsy moth larvae to virus under Cd stress.

Metabarcoding of canopy arthropods reveals negative impacts of forestry insecticides on community structure across multiple taxa

Abstract Insecticides used to combat outbreaks of forest defoliators can adversely affect non‐target arthropods. Forestry insecticides typically suppress Lepidoptera larvae which are the cornerstone of the canopy community of deciduous oak forests. The abrupt removal of this dominant component of the food web could have far‐reaching implications for forest ecosystems, yet it is rarely investigated in practice owing to several methodological shortcomings. The taxonomic impediment and the biased nature of arthropod sampling techniques particularly impede the assessment of insecticide impacts on diverse communities. To tackle this issue, we propose an experimental approach combining sampling by pyrethrum knockdown and species determination via DNA metabarcoding, using community subsampling to derive estimates of species abundances. We applied this protocol to investigate the short‐term effects of the insecticides diflubenzuron (DFB) and Bacillus thuringiensis var. kurstaki (BTK) on canopy‐dwelling arthropod communities in German oak woodlands. Our approach allowed us to detect most of the diversity and integrate species abundances in our analyses. By classifying arthropod species into assemblages based on their expected sensitivity rather than coarse taxonomic groupings, we could unveil substantial effects of DFB across multiple taxa 5 weeks after application. Although strong effects on single species appear related to direct toxicity, substantial impacts of DFB on parasitoids and xylophagous beetles suggest that anti‐defoliator treatments can have previously unsuspected indirect effects on some components of forest arthropod communities. The impacts of BTK on community structure were consistent with that of DFB though much weaker. Synthesis and applications. Comparing diversity patterns in the arthropod communities of sprayed and unsprayed oak canopies, our results show that selective insecticides can alter species diversity in presumably non‐sensitive taxa. Even though the ecological significance of these impacts has yet to be assessed in an operational setting, their existence calls for increased regulatory scrutiny on indirect effects. As community approaches become more attainable with the rapid development of DNA metabarcoding, we suggest the inclusion of community‐level end points as regulatory requirements for the approval of forest‐use insecticides.

Assessment of defoliation and subsequent growth losses caused by Lymantria dispar using terrestrial laser scanning (TLS)

Key messageTLS scans of three surveys before, during and after gypsy moth gradation, allowed high-resolution tracking of defoliation and subsequent inter-annual growth losses on an individual tree level.Foliation strongly determines all tree growth processes but can be reduced by various stress factors. Insect defoliation starts at variable times and is one stress factor that may affect photosynthetic processes and cause immediate reactions like refoliation, which are difficult to detect by surveys repeated at 1-year intervals. This study used a large-scale field experiment in German oak/mixed forests affected by gypsy moths (Lymantria dispar) to test the use of terrestrial laser scanning (TLS) for detecting inter-annual foliation and growth losses at the individual tree level caused by the gypsy moth. The experiment comprised two levels of gypsy moth defoliation risk, high (H) and low (L), as well as two pest control treatment levels: spraying with the insecticide Mimic (M) or unsprayed control (C). The factorial design consisted of four treatment combinations (HC, HM, LC, and LM), applied to 11 spatial blocks with a total of 44 plots. The TLS approach detected the defoliation caused by the gypsy moth, estimated as leaf area and crown perforation parameters. For the first time, TLS-derived tree foliation was evaluated based on inter-annual stem growth. Leaf area and crown perforation showed a correlation of + 0.6 and – 0.35, respectively, with basal area increments. Furthermore, this study revealed subsequent growth losses in the same year due to defoliation. Our results show that TLS can offer new opportunities to develop new indicators that monitor foliation at the individual tree level. The crown perforation can describe defoliation or the tree’s vitality based on one scanning campaign, whereas the leaf area needed at least two.

Lymantria umbrosa (Hokkaido gypsy moth)

Lymantria umbrosa (Hokkaido gypsy moth)

Чувствительность гусениц непарного шелкопряда (Lepidoptera: Erebidae: Lymantria dispar) с юга Хабаровского края к различным штаммам вируса ядерного полиэдроза

The article discusses data on the effect of the nuclear polyhedrosis virus (NPV) on gypsy moth caterpillars of the Far Eastern population. In particular, the article provides data on the dynamics of caterpillar mortality under laboratory conditions under different viral load of four NPV strains: Kyrgyz, Japanese, Krasnodar, and Siberian. The difference in the duration of the incubation period of a strain and infectious load has not been established. The maximum virulence was observed for the strain Kyrgyz (about 96% at the maximum titer). The duration of the mortal period differed for all tested strains. The indicator L50 was achieved for all infectious loads of the Kyrgyz and Krasnodar strains. The maximum daily mortality was detected at the maximum infectious loads of the Kyrgyz and Japanese strains (29.7% and 39.9%, respectively) on the second day of the mortal period.

Integration of Mirna and Mrna Expression Profiles in Asian Gypsy Moth Lymantria Dispar in Response to Cyantraniliprole

Integration of Mirna and Mrna Expression Profiles in Asian Gypsy Moth Lymantria Dispar in Response to Cyantraniliprole

Gut Bacterial Microbiota of Lymantria Dispar Asiatica and its Involvement in Beauveria Bassiana Infection

Gut Bacterial Microbiota of Lymantria Dispar Asiatica and its Involvement in Beauveria Bassiana Infection

Response of Cavity Nesting Birds to Lymantria Dispar (Lepidoptera) and Aerial Spraying – an Experimental Approach

Response of Cavity Nesting Birds to Lymantria Dispar (Lepidoptera) and Aerial Spraying – an Experimental Approach