Dispar Larvae Research Articles

Idesia polycarpa (Salicaceae) leaf constituents and their toxic effect on Cerura vinula and Lymantria dispar (Lepidoptera) larvae

Phytochemical investigation of Idesia polycarpa (Salicaceae) resulted in the structure elucidation of nine previously undescribed phenolic natural products along with six known compounds. The compounds are structurally related to salicinoids that are known defense compounds from Salix and Populus species. The I. polycarpa diet was toxic, as shown in feeding experiments with larvae of Lymantria dispar, an herbivorous broadleaf tree generalist insect, and with larvae of Cerura vinula, a specialist adapted to poplar. The survival rate and mass gain of larvae was significantly lower when they fed on I. polycarpa leaves, compared to larvae fed on Populus nigra leaves. Potential reasons for the poor performance of both herbivores on I. polycarpa leaves are discussed.

Characterization of a nucleopolyhedrovirus variant of the gypsy moth, Lymantria dispar (Lepidoptera: Lymantriidae) in Turkey

ABSTRACTThe gypsy moth (Lymantria dispar L., Lepidoptera: Lymantriidae) is one of the most serious pest of various forestal, food and industrial crops worldwide. We have characterized a new Lymantria dispar nucleopolyhedrovirus (LdMNPV-T4) variant, which was isolated from dead L. dispar larvae in Turkey. Scanning electron microscope observations showed that the polyhedral occlusion bodies (OBs) of the LdMNPV-T4 were irregularly shaped. Transmission electron microscopy revealed that OBs of LdMNPV-T4 were occupied with several virions in which multiple nucleocapsids packaged by viral envelope. Restriction analysis of the LdMNPV-T4 DNA purified from the viral inclusion bodies yielded BamHI, BglII, EcoRI and HindIII fragments. The mean size estimated for the complete LdMNPV-T4 genome was calculated to be 163.3 kb. Phylogenetic analysis of amplified polh, lef-8 and lef-9 sequences showed its relation to the other NPVs from Lymantria species. Mortality values of the LdMNPV-T4 at four different concentrations against third instar larvae of L. dispar ranged from 45% to 88%. These results suggest that LdMNPV-T4 isolated from Turkey is a promising microbial control agent to be utilized for the biological control of L. dispar.

Larvicidal activity and insecticidal mechanism of Chelidonium majus on Lymantria dispar

Based on the broad spectrum of its biological activities, Chelidonium majus has been studied extensively in the medical field. However, few studies have focused on the insecticidal activity of C. majus, and the precise mechanism of its insecticidal activity. In the present study, larvicidal activity and insecticidal mechanism of C. majus on Lymantria dispar were investigated using bioassays, in vitro and in vivo enzyme activity assays, determination of the nutritional index, and gene transcription analysis. The results showed that alkaloids are the main insecticidal ingredients in C. majus. Among the five isoquinoline alkaloids, coptisine was present at the highest concentration (1624.23mg/L), while tetrahydrocoptisine showed the lowest concentration (0.47mg/L). Both the crude extract of C. majus (CECm) and the total alkaloids of C. majus (TACm) possessed a potent insecticidal activity toward L. dispar larvae. TACm had significant effects on the relative consumption rate, efficiency of conversion of digested food into growth, approximate digestibility, and approximate digestibility of L. dispar larvae. Enzyme activity assays suggested that both CECm and TACm displayed their strongest inhibitory activity to in vitro glutathione S-transferase (GST) and acetylcholinesterase (AChE), and showed the weakest inhibition of in vitro carboxylesterase (CarE). Moreover, CECm and TACm affected the in vivo activities of five enzymes. The in vivo activities of AChE and CarE in L. dispar larvae were inhibited significantly by CECm and TACm. Additionally, qRT-PCR analysis revealed that the transcription of the five enzymes was also affected by TACm. In conclusion, alkaloids in C. majus showed a prominent toxicity to L. dispar by reducing food intake, influencing nutritional indices, and affecting the activity and mRNA transcription of detoxifying and protective enzymes. This study provides novel insights into the insecticidal mechanism of C. majus.

A comparison of the adaptations of strains of Lymantria dispar multiple nucleopolyhedrovirus to hosts from spatially isolated populations

The adaptation of pathogens to either their hosts or to environmental conditions is the focus of many current ecological studies. In this work we compared the ability of six spatially-distant Lymantria dispar (gypsy moth) multiple nucleopolyhedrovirus (LdMNPV) strains (three from eastern North America and three from central Asia) to induce acute infection in gypsy moth larvae. We also sequenced the complete genome of one Asian (LdMNPV-27/0) and one North American (LdMNPV-45/0) strain which were used for bioassay. We found that all of the North American virus strains, with the exception of one, demonstrated higher potency than the Asian virus strains, either in North American (Lymantria dispar) larvae or, in Asian (Lymantria dispar asiatica) larvae. Complete genome sequencing revealed two gene deletions in the LdMNPV-27/0 strain: the virus enhancin factor gene (vef-1) and the baculovirus repeated orf gene (bro-p). These deletions were not seen in the LdMNPV-45/0 strain nor in other American strains available in archiving systems. We also found deletions of the bro-e and bro-o genes in LdMNPV-45/0 strain but not in the LdMNPV-27/0 strain. The phylogenetic inference with an alignment of the 37 core gene nucleotide sequences revealed the close relationship of the LdMNPV-45/0 strain with other American strains accessed in GenBank (Ab-a624 and 5-6) while the LdMNPV-27/0 strain was clustered together with the LdMNPV-3054 strain (isolated in Spain) instead of predicted clustering with LdMNPV- 3029 (isolated in Asia). Our study demonstrated that first, different LdMNPV isolates from the same metapopulations of L. dispar exhibit little or no difference in the degree of virulence towards host larvae and second, that locality of host population is not an important driver of LdMNPV virulence. Virulence of LdMNPV is determined only by viral genetics. The genetic differences between North American and Central Asian virus strains are discussed.

BAZI HERBİVOR BÖCEKLER HAKKINDA BİYOLOJİK GÖZLEMLER

Some biological characteristics of the herbivorous Archips rosana (Linnaeus) (Lepidoptera: Tortricidae), Melitaea didyma (Esper) (Lep.: Nymphalidae), Melitaea cinxia (Linnaeus) (Lep.: Nymphalidae), Allophyes oxyacanthae (Linnaeus) (Lep.: Noctuidae), Aporia crataegi (Linnaeus) (Lep.: Pieridae), Periclistus brandtii (Ratzeburg) (Hymenoptera: Cynipidae), Lymantria dispar (Linnaeus) (Lep.: Erebidae) and Mustha spinosula (Lefèbvre) (Hemiptera: Pentatomidae) obtained from Thrace Region during field studies in the period of 2013-2016 were monitored in laboratory conditions and the observations were evaluated. The carnivorous behaviour of A. rosana and M. didyma larvae, egg production by adult females of A. oxyacanthae through parthenogenesis, the defense/predatory behaviour of M. spinosula adults on L. dispar larvae and the association of P. brandtii with Pyrus communis (Linnaeus) plant are the observations reported for the first time. Furthermore, from Melitaea cinxia larva, the parasitoid Erycia festinans (Meigen) (Diptera: Tachinidae) emerged. E. festinans is a new record for Diptera fauna of Turkey. Correspondingly, M. cinxia and E. festinans is a new host-parasitoid association for Turkey.

Genetic determination of tannins and herbivore resistance in Quercus ilex

Genetic variability of trees influences the chemical composition of tissues. This determines herbivore impact and, consequently, herbivore performance. We evaluated the independent effects of plant genotype and provenance on the tannin content of holm oak (Quercus ilex) and their consequences for herbivory and performance of gypsy moth (Lymantria dispar) larvae. Oak seedlings of 48 open-pollinated families from six populations were grown in a common garden in central Spain. Half the plants were subjected to defoliation by gypsy moth larvae and the other half were destructively sampled for chemical analysis. Tannin content of leaves did not differ significantly among populations but differed significantly among families. Estimates of heritability (h 2) and quantitative genetic differentiation among populations for tannin content (Q ST) were 0.83 and 0.12, respectively. Defoliation was not related to the tannin content of plants nor to spine and trichome densities of leaves, although positive family–mean associations were observed between defoliation and both seed weight and plant height (P < 0.003). Among the oak populations, differential increase in larval weight gain with defoliation was observed. Leaf tannin content in Q. ilex is genetically controlled but does not influence defoliation or predict performance of the larvae. Different efficiencies of food utilisation depending on the oak genotypes indicate that other plant traits are influencing the feeding patterns and fitness of L. dispar and consequent population dynamics.

First report of Toxomerus dispar (Fabricius, 1794) (Diptera: Syrphidae) preying Spodoptera frugiperda (J.E. Smith, 1797) (Lepidoptera: Noctuidae) in laboratory.

The fall armyworm Spodoptera frugiperda (Smith, 1797) (Lepidoptera: Noctuidae) is one of the most important pests in Brazilian maize fields that causes damage to approximately 57% of the crop (Cruz etal., 1999 S.). However, several biological control agents occur freely in agroecosystems and are known to suppress the S. frugiperda population (Dequech et al., 2004 ; Bortolotto et al., 2014 ). Among the predator insects, hoverflies have been reported to occur in maize fields but are usually associated with aphid infestation (Swaminathanet al., 2015). Thus far, few studies have investigated hoverflies preying on lepidopteran pests, and the spectrum of preys examined is unclear. To our knowledge, this is the first report of Toxomerus dispar larvae (Fabricius, 1794) (Diptera: Syrphidae) preying on S. frugiperda caterpillars (Figure 1).Thirty specimens of hoverfly larvae were collected from 100 plants (in V

An alphabaculovirus isolated from dead Lymantria dispar larvae shows high genetic similarity to baculovirus previously isolated from Lymantria monacha – An example of adaptation to a new host

A new isolate of baculovirus, Lymantria dispar multiple nucleopolyhedrovirus-BNP (LdMNPV-BNP), was found in dead gypsy moth (L. dispar) caterpillars collected in the Biebrzanski National Park in Poland. Here, we examined its biological activity, structure, genetic content and phylogeny. Multiple nucleocapsids of LdMNPV-BNP are enveloped together in 2–26 virions embedded in occluded bodies (OBs) very similar to the OBs previously described in viruses infecting Lymantriinae. This isolate kills pest larvae in a relatively short time (LT50 of approximately 9days for a dose of 2×107OBs/ml), highlighting the possibility for its use as a biopesticide. Next-generation sequencing of LdMNPV-BNP revealed gene content (e.g. DNA photolyase) that is not present in any LdMNPV isolate sequenced to date. The genome is 157,270 base pairs long and has a notably lower G+C content in comparison to other LdMNPVs (50.3% G+C content compared to an average of 57.4% among other LdMNPVs). According to our phylogenetic analysis based on 37 core genes, LdMNPV-BNP is a member of group II alphabaculoviruses, which are closely related to LdMNPV and LyxyMNPV (Lymantria xylina multiple nucleopolyhedrovirus). Molecular evolution inference based on the partial sequence of lef-8, lef-9 and polh genes shows that LdMNPV-BNP and isolates of Lymantria monacha nucleopolyhedrovirus (LymoNPV) may share a very recent common ancestor or be isolates of the same virus species. LdMNPV-BNP, like other baculoviruses, could be beneficial as an active component of biopesticides that can be used during forest integrated pest management.

Behavioral and morphological responses of an insect herbivore to low nutrient quality are inhibited by plant chemical defenses

Animals have several strategies to contend with nutritionally poor diets, including compensatory consumption and enhanced food utilization efficiencies. Plants produce a diversity of defense compounds that affect the ability of herbivores to utilize these strategies in response to variation in food nutritional quality. Little is known, however, about effects of allelochemicals on herbivores utilizing integrated behavioral and morphological responses to reduced food quality. Our objectives were to (1) examine how variation in diet nutritional quality influences compensatory responses of a generalist insect herbivore, and (2) determine how plant defenses affect these processes. Gypsy moth (Lymantria dispar) larvae were administered one of nine combinations of diet having low, moderate, or high nutritional quality and 0, 2, or 4 % purified aspen (Populus tremuloides) salicinoids. We quantified larval growth, consumption, frass production, and biomass allocation to midgut tissue over a 4-day bioassay. In the absence of salicinoids, larvae compensated for reduced nutritional quality and maintained similar growth across all diets through increased consumption, altered midgut biomass allocation, and improved processing efficiencies. Dietary salicinoids reduced larval consumption, midgut biomass allocation, digestive efficiencies, and growth at all nutritional levels, but the effect size was more pronounced when larvae were fed nutritionally suboptimal diets. Our findings demonstrate that integrated behavioral and morphological compensatory responses to reduced food quality are affected by plant defenses, ultimately limiting compensatory responses and reducing larval performance.

Lymantria mathura nucleopolyhedrovirus: Identification, occurrence and genetic diversity in Iwate Prefecture, Japan

A high prevalence of nuclear polyhedrosis has been observed in larval outbreaks of Lymantria mathura in Iwate Prefecture, Japan. However, the virus responsible has not been identified. Here the virus was designated Lymantria mathura nucleopolyhedrovirus (LymaNPV), based on partial sequence results of the lef-8, lef-9, and polh genes and transmission electron microscopic observations. Diagnosis by polymerase chain reaction targeting of the partial polh gene and a subsequent restriction fragment length polymorphism (RFLP) analysis indicated that LymaNPV was an exclusive causative agent for the nuclear polyhedrosis of the L. mathura larvae. LymaNPV was also detected from a very small fraction of L. dispar larvae that co-occurred with L. mathura larvae where the prevalence of LymaNPV-caused disease was high. A bioassay using LymaNPV against L. dispar larvae produced infection with the inoculated virus. This finding was consistent with the results of the field sample analysis. LymaNPV contained six genome types in the L. mathura populations sampled, as determined by RFLP of LymaNPV genomic DNA and southern blot hybridization analyses. None of the genome types was unique to any sampling site, indicating that some flow had occurred among sites. However, genome-type composition seemed to differ among sites. This study provides basic information about the interaction between L. mathura and LymaNPV.

Life history traits and the activity of antioxidative enzymes in Lymantria dispar L. (lepidoptera, lymantriidae) larvae exposed to benzo[a]pyrene

Increased presence of benzo[a]pyrene in the environment underlines the need for development of sensitive biomarkers for monitoring. Antioxidative enzymes could be used as early-warning signals because of their sensitivity and applicability. The activity of 2 antioxidative enzymes, superoxide dismutase (SOD) and catalase (CAT), were measured in midgut tissues of fifth instar Lymantria dispar larvae exposed to different concentrations of benzo[a]pyrene: 2 ng, 10 ng, 20 ng, 100 ng, 200 ng, and 2000 ng benzo[a]pyrene/g dry food weight. Larval development, larval mass, and relative growth rate were also monitored. The authors detected prolonged larval development, as well as reduced larval mass and relative growth rate in larvae exposed to all benzo[a]pyrene concentrations. The L. dispar midgut SOD activity was significantly increased, and 2 SOD isoforms were detected on native polyacrylamide gel electrophoresis in larvae fed on artificial diet supplemented with benzo[a]pyrene. In contrast, the control group had only 1 isoform. Catalase activity was significantly increased in all benzo[a]pyrene-treated larvae. Native gel electrophoresis showed that a switch in active CAT isoforms occurred after benzo[a]pyrene treatment. Thus, SOD and CAT in polyphagous herbivorous L. dispar larvae are very sensitive to low concentrations of benzo[a]pyrene. Therefore, they could be used as biomarkers for exposure and effects of this toxic polycyclic aromatic hydrocarbon.

OCCURRENCE OF INTESTINAL PARASITES IN PAPER MONEY CIRCULATING IN THE LOCAL TRADE OF THE CITY OF SÃO MATEUS, ESPÍRITO SANTO, BRAZIL

Helminth eggs and protozoan cysts have great resistance to aggressions and environmental factors. In order to verify the involvement of inanimate objects in the transmission mechanisms of parasitic infections, a parasitological study was carried out with paper money circulating in the city of São Mateus, ES, Brazil, among September 2010 and September 2012. Notes were sent to Laboratório de Análises Clínicas of the Universidade Federal do Espírito Santo, distributed in plastic containers containing distilled water, stirred and scraped manually. The material from scraping and rinsing was centrifuged and the pellet fraction was analyzed in a light microscope. From a total of 270 samples analyzed, 22 (8.15%) were positive for eggs or cysts of intestinal parasites and R$ 2.00 bill was the most contaminated. Among the parasite species found Giardia duodenalis was the most frequently, which was observed in 2.22% of the samples, followed by Entamoeba coli and hookworm, both with 1.48%, Ascaris lumbricoides, Taenia sp., E. histolytica/E. dispar and free-living nematode larvae all with 0.74% positivity. From the 30 shops analyzed, 10 (33.33%) had paper money positive for parasitic forms and the greater positive frequency was observed in downtown establishment. Considering the large resistance of eggs/cysts of intestinal parasites to environmental conditions and the importance of paper money as transmitting disease, it is noteworthy the imminent need for investments in studies in São Mateus in order to provide better epidemiology survey for parasitic infections.

Effects of leaf maturity and wind stress on the nutrition of the generalist caterpillar Lymantria dispar feeding on poplar

AbstractThe growth rates of insect herbivores commonly decrease when they feed on mature leaves due to the combined effects of several nutritional and physiological mechanisms. Environmental stresses during leaf development may also decrease herbivore performance. The present study tests two main hypotheses to help clarify the importance of these factors for the nutrition and growth of an insect herbivore: (i) decreases in nutrient levels, consumption rates and nutrient assimilation efficiencies impact negatively on herbivores feeding on mature leaves and (ii) wind stress has a negative impact on herbivores feeding on mature leaves. The results show that mature poplar (Populus alba × Populus tremula) leaves have decreased levels of protein and increased levels of fibre, and that growth rates of gypsy moth (Lymantria dispar L.) are decreased on mature leaves in association with decreased consumption rates. However, in contrast to the first hypothesis, protein and carbohydrate are assimilated efficiently (74–82% and 84–87%, respectively) from immature and mature poplar leaves. The larvae are able to chew mature leaves as efficiently as immature leaves, potentially maximizing nutrient extraction. By contrast to the second hypothesis, wind‐stressed leaves have no significant detrimental effects on nutrient assimilation efficiencies, and the lower growth rates of L. dispar larvae feeding on mature wind‐stressed leaves can be explained by lower consumption rates. Therefore, the availability of nutrients to herbivores feeding on mature tree leaves is not necessarily impacted by lower assimilation efficiencies, even when leaves develop under wind stress. These results help explain some of the large variation between the nutritional qualities of trees for forest Lepidoptera.

Effects of methoxyfenozide on ecdysone receptor complex expression in larval Asian gypsy moth

Abstract As a target of insect growth regulators, the ecdysone receptor complex binds ecdysone agonists to regulate gene transcription, development, and growth. To understand the response of Lymantria dispar to methoxyfenozide, we studied receptor complex transcription profiles following larval exposure to methoxyfenozide, and observed important variations amongst post-embryonic stages. After the exposure of 2nd and 3rd instar larvae to LC5 and LC20 methoxyfenozide for 72 h, the transcription levels of ecdysone receptor complex genes were mainly upregulated in 2nd instar larvae, but downregulated in 3rd instar larvae. These results provide expression characteristics of the ecdysone receptor complex in L. dispar larvae after methoxyfenozide exposure.

Characterization of the transcriptome of the Asian gypsy moth Lymantria dispar identifies numerous transcripts associated with insecticide resistance

Although the Asian gypsy moth Lymantria dispar causes extensive forest damage worldwide, little is known regarding the genes involved in its development or response to insecticides. Accordingly, characterization of the transcriptome of L. dispar larvae would promote the development of toxicological methods for its control. RNA-seq analysis of L. dispar larvae messenger RNA (mRNA) generated 62,063 unigenes with N50 of 993 bp, from which 23,975 unique sequences (E-value < 10−5) were identified using a BLASTx search of the NCBI non-redundant (nr) database. Using functional classification in the Gene Ontology (GO) and Clusters of Orthologous Groups (COG) databases, 7,309 indentified sequences were categorized into 51 functional groups and 8,079 sequences were categorized into 25 functional groups, respectively. Moreover, we identified a large number of transcripts encoding known insecticide targets, or proteins involved in the metabolism of insecticides. Reads per kilobase of unigene length per million mapped reads (RPKM) analysis identified 39 high abundance transcripts, of which 27 exhibited significantly altered expression patterns across the egg, larvae, pupae, male and female adult stages. Our study provides the most comprehensive transcriptomic sequence resource for L. dispar, which will form the basis for future identification of candidate insecticide resistance genes in L. dispar.

Nutrients are assimilated efficiently byLymantria disparcaterpillars from the mature leaves of trees in the Salicaceae

The efficient aquisition of nutrients from leaves by insect herbivores increases their nutrient assimilation rates and overall fitness. Caterpillars of the gypsy moth (Lymantria dispar L.) have high protein assimilation efficiencies (PAE) from the immature leaves of trees such as red oak (Quercus rubra) and sugar maple (Acer saccharum) (71–81%) but significantly lower PAE from their mature leaves (45–52%). By contrast to this pattern, both PAE and carbohydrate assimilation efficiencies (CAE) remain high for L. dispar larvae on the mature leaves of poplar (Populus alba × Populus tremula) grown in greenhouse conditions. The present study tests two alternative hypotheses: (i) outdoor environmental stresses cause decreased nutrient assimilation efficiencies from mature poplar leaves and (ii) nutrients in the mature leaves of trees in the poplar family (Salicaceae) remain readily available for L. dispar larvae. When poplar trees are grown in ambient outdoor conditions, PAE and CAE remain high (approximately 75% and 78%, respectively) in L. dispar larvae, in contrast to the first hypothesis. When larvae feed on the mature leaves of species in the Salicaceae [aspen (Populus tremuloides), cottonwood (Populus deltoides), willow (Salix nigra) and poplar], PAE and CAE also remain high (68–76% and 72–92%, respectively), consistent with the second hypothesis. Larval growth rates are strongly associated with protein assimilation rates, and more strongly associated with protein assimilation rates than with carbohydrate assimilation rates. It is concluded that tree species in the Salicaceae are relatively high-quality host plants for L. dispar larvae, in part, because nutrients in their mature leaves remain readily available.

Environmental induction of larval diapause and life-history consequences of post-diapause development in the Large Copper butterfly, Lycaena dispar (Lepidoptera: Lycaenidae)

Many insects in temperate zones withstand the adverse conditions of winter through entering diapause and the two most important environmental stimuli that induce diapause are photoperiod and ambient temperature. The Large Copper butterfly, Lycaena dispar Haworth (Lepidoptera: Lycaenidae), is a Palearctic butterfly that hibernates as larvae. Since this butterfly is a near threatened species in some regions, there has been a growing need for a standardized protocol for mass rearing of this butterfly based on the adequate knowledge of its ecology. In the present study, we first identified that L. dispar larvae were sensitive to the photoperiodic induction of diapause during their first larval instar. We then investigated to what extent the diapause-inducing effects of photoperiod could be modified by ambient temperatures in L. dispar larvae by exposing them to the range of day-lengths (L:D 14:10, 12:12, 10:14 and 8:16) at three different temperatures (15, 20 and 25 °C). All larvae were induced to enter diapause at low ambient temperature (15 °C) regardless of photoperiod, whereas most of them (86 %) exhibited direct development when temperature was high (25 °C). The photoperiodic induction of diapause was evident when day-length was shorter than 14 h at intermediate temperature (20 °C). Pre-diapause development was prolonged at low temperatures. Finally, we found that post-diapause development of L. dispar larvae was determined by both the chilling temperature experienced by diapausing larvae and the duration of larval diapause. Adult emergence was enhanced when larvae were chilled at 8 °C and when they had been under the state of diapause for 20 days before they were treated to terminate diapause.

Supraoptimal temperatures influence the range dynamics of a non‐native insect

AbstractAimTo examine the relationship between the range dynamics of the non‐native species Lymantria dispar (L.) and supraoptimal temperatures during its larval and pupal period.LocationWest Virginia and Virginia, United States, North America.MethodsWe linked the annual frequency of supraoptimal temperatures during the larval and pupal period of L. dispar with annual changes in its range dynamics based upon a spatially robust 20‐year dataset. Correlation analyses were used to estimate the association between exposure time above the optimal temperature for L. dispar larval and pupal development, and the rate of invasion spread when adjusted for spatial autocorrelation.ResultsWe documented L. dispar range expansion, stasis, and retraction across a fairly narrow latitudinal region. We also observed differences in the amount of exposure above the optimal temperature for L. dispar larval and pupal development across this region. Temperature regimes in the Coastal Plain and Piedmont regions of Virginia, where the L. dispar range has retracted or remained static, were warmer than those in the Appalachian Mountains of Virginia and West Virginia, where L. dispar has expanded its range. Our analyses at a smaller spatial scale confirmed a statistically negative association between exposure time above the optimal temperature for L. dispar larvae and pupae, and the rate of L. dispar invasion spread over the 20‐year period.Main conclusionsThe shifting, expansion and retraction of species distributional ranges holds critical implications to both invasion ecology and conservation biology. This work provides novel empirical evidence of the importance of supraoptimal temperatures on the range dynamics of a non‐native invasive insect with application to both non‐native and native species whose physiological processes are strongly regulated by temperature.

Prothoracicotropic hormone-producing neurosecretory neurons and antioxidative defense in midgut of Lymantria dispar in trophic stress

As a very invasive insect species, Lymantria dispar is adaptable and sensitive to a changing environment. In insects the neuroendocrine system first reacts to stress by production of prothoracicotropic neurohormones (PTTH) that control ecdysteroid synthesis (morphogenetic and stress hormones). In this article, we report changes in the L2' brain neurosecretory neurons that synthesize PTTH in L. dispar larvae after feeding on locust tree leaves (Robinia pseudoacacia), an unsuitable host plant. Groups of larvae (n = 20 per experimental group) were offered this in comparison with oak leaves (Quercus robur), a suitable control diet, for 3 days after molting into the fourth instar. L2' neurons and their nuclei were enlarged and the amount of neurosecretory product in the cytoplasm was increased (15.5%) after consumption of locust tree leaves in comparison to the control. Furthermore, activities of the following antioxidative defense components were estimated: superoxide dismutase (SOD), catalase (CAT), and amount of glutathione in the midgut. Higher SOD activity (13.85 ± 0.9 U/mg prot.) and glutathione amount (0.56 ± 0.06 mMGSH/g tissue) but unchanged CAT activity was found in the midgut of larvae offered locust tree leaves when compared to the control.

Potential improvement of Lymantria dispar L. management by quercetin

Lymantria dispar, a polyphagous insect pest, copes with a wide variety of host-specific allelochemicals. Glutathione S-transferases (GST) are important for catalyzing detoxification in L. dispar. Larval mortality, GST activity in midgut tissue and mass of L. dispar with different trophic adaptations (originating from two forests with a suitable host, Quercus robur, and an unsuitable host, Robinia pseudoacacia), differed after feeding on quercetin supplemented diets (2% or 5% w/w). Quercetin inhibited GST most potently in oak forest larvae that were less adapted to flavonoids in their diet. The larvicidal effect of quercetin on L. dispar larvae depended on the host-use history. We believe this is important in strategies for sustainable control of insect pests.