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The pine processionary moth Thaumetopoea wilkinsoni (Tams, 1926) (Lepidoptera: Notodontidae) is one of the most harmful species that causes destruction in pine ecosystems and also causes critical skin reactions in humans and animals due to its urticating hairs. This study aimed to evaluate the efficacy of different strains [Bti ATCC 35646 (wild-type strain), Bti pHT315, and Bti pHTppk (mutant strain)] of Diptera-targeted Bacillus thuringiensis subsp. israelensis (Bti) and toxins (spore/crystal mixtures) obtained from these strains against the 4th larval stage of T. wilkinsoni under laboratory conditions. T. wilkinsoni eggs were collected from pine trees at Ondokuz Mayıs University in Samsun, Turkey, in 2022. Pine needles were contaminated with bacterial strains of different concentrations (1 × 107, 1 × 108, 1 × 109 cfu/mL) in 5 mL and toxins in different concentrations (0.15, 0.3, 0.6, 1.25, 2.5, 5 mg/mL) in 2 mL. Larvae were placed in containers with 30 larvae in each group and were observed for 25 days. As a result of the study, Bti ATCC 35646 with 63.4% mortality and the lowest LC50 value of 1.2 × 109 cfu/mL among the three strains of Bti and Bti pHTppk with 76.7% mortality and the lowest LC50 value of 1.2 mL among the toxins from the Bti strains had found to be virulent for T. wilkinsoni. The results obtained from our study suggest that Diptera-targeted Bti is virulent to T. wilkinsoni and that this strain and spore/crystal mixture can be used in the biological control of this species. [ABSTRACT FROM AUTHOR]

Ectotherms are largely impacted by extreme climate events, essentially heatwaves. In Tunisia, the pine processionary moth (PPM), Thaumetopoea pityocampa, is a defoliator typically laying eggs in summer. Its geographical range is expanding northwards in Europe while retracting from southern Tunisia where summer temperatures can reach extreme heats. We explored the effects of climate change over the last 30 years on PPM at its southern range edge. We investigated variations of fecundity and causes of egg mortality over time using historical and contemporary collections of egg masses. Due to incomplete historical series, a clustering method was used to group climatically homologous sampling sites and perform allochronic analyses on clusters instead of individual localities. Our results suggest negative effects of summer heat on egg survival, down to 0% hatching rate in one site during a major heatwave. Such high hatching failures resulted partly from high egg sterility and aborted embryos, with little effects of parasitism rate, suggesting heat susceptibility during embryonic development, but our results do not allow distinguishing impeded mating success from failed egg maturation or early embryo death. Decreasing female fecundity was observed in regions where allochronic comparisons were possible, associated with a decrease in parasitism rate, while climatic variability increased. Previous studies have confirmed experimentally the thermal sensitivity of PPM early instars to temperatures observed in the present work, including one population from southern Tunisia. However, further work is required to evaluate the relative importance of warming summers among populations, since the risk of heat stress depends on the phenology of sensitive instars, and populations from the warmest areas may not necessarily be the most vulnerable to climate change if they already evolved phenological heat avoidance. In addition to heat‐induced mortality, the ultimate fitness of heat survivors should also be explored to determine potential carry‐over effects on subsequent life stages. [ABSTRACT FROM AUTHOR]

Pine processionary moth are known as oligophagous forest pests, usually found in cocoons on Pinus trees. While these moths are found in the south of Europe and the north of Africa worldwide, in Turkey they are found in the Mediterranean, Aegean, Black Sea and Marmara regions. Thaumetopoea pityocampa (Den. & Schiff.) and Thaumetopoea wilkinsoni (Tams) species have been observed in the coastal regions of Turkey. Identification of the species is an important step in the development of biological control strategies. The starting point of this study is the desire to control the pine processionary moth in Marmara University Göztepe Campus. However, since both of these species are found in Turkey, especially in the Marmara Region, the main aim of this study is to determine which species the pine processionary moth in the campus belong to. Morphological and molecular methods were used. As a result of the study, based on both morphology and molecular data, it was determined that the species found on the campus was Thaumetopoea wilkinsoni. [ABSTRACT FROM AUTHOR]

Pinus species, used in traditional medicine and are an important industrial plant, suffer severe ecological and economic losses with the invasion of Thaumetopoea wilkinsoni (the pine processionary moth). Due to the damage caused by T. wilkinsoni, a biotic stress factor, the changes occur in the ecological and physiological parameters of Pinus species, which also try to cope with abiotic stress. The changes in fresh/dry weight, percent water content, chlorophyll a and b content, the total protein content, malondialdehyde (MDA) amounts, and superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX) activities in leaf samples of the pine processionary moth-infested and non-infested Pinus sylvestris L. and P. nigra Arn. species were compared in the study. The leaf samples of P.nigra and P. sylvestris were collected from the Ondokuz Mayıs University Kurupelit Campus in Samsun, Turkey, in 2020. Individuals of the moth-infested and non-infested P. sylvestris and P. nigra formed two distinct experimental groups. It was found that the fresh/dry weight, percent water content, chl a and b content of the moth-infested individuals of both species were significantly decreased compared with non-infested individuals; the total protein contents, lipid peroxidation and SOD, CAT, APX activities were found to be significantly increased. It was also determined that the moth-infested individuals of both species had the most sesquiterpenes and the least monoterpenes. Our results clearly show that P. nigra and P. sylvestris defend themselves when attacked by the pine processionary moth, both by changing the amount of secondary metabolites and by reacting as antioxidative defense responses. [ABSTRACT FROM AUTHOR]

The Pine Processionary Moth (PPM) Thaumetopoea wilkinsoni has long been attacking Mediterranean forests. In its management strategy, Lebanon has focused mainly on pesticides, leaving natural predators as an understudied control option. This study aims to understand the distribution of the Eurasian Hoopoe Upupa epops, by assessing the damage caused by the PPM. We attempted to explain the distribution of the two species, their relation to other factors and, with a Citizen Science (CS) approach, we developed their distribution maps. We found that the varying PPM damage between cadastral units was linked to Important Bird Areas (IBAs), highlighting the importance of multiple birds, including the Eurasian Hoopoe, as natural predators of this pest and calling for their conservation. As understudied species in Lebanon, this paper sets the path and offers guidelines for future researchers willing to work on similar crucial research in a climate change context and reveal the underlying relation between the two species. [ABSTRACT FROM AUTHOR]

Simple Summary: Thaumetopoea pityocampa caterpillars are a significant pest of conifer trees in Europe and live gregariously in a communal tent with siblings and conspecifics from other colonies. Despite their economic and medical importance, there has been a lack of quantitative information on the tent construction and foraging behaviour in T. pityocampa colonies. In this study, we observed the tent construction and foraging behaviour of T. pityocampa caterpillars in the field at Tregnago, Verona, Italy. At around sunset, large male caterpillars emerged from the tent first to construct the tent, while many female caterpillars emerged later in the night only to forage. As younger instar caterpillars moulted to older larval instars, the environmental temperature decreased, which consequently increased the duration of their foraging activities. The final tent structure constructed by later instar caterpillars was not isodiametric; more silk was applied on the southern side of the tent to receive maximum insolation during the winter months. This study demonstrated the importance of the winter tent and individual variation in tent construction and foraging behaviour of T. pityocampa caterpillars amongst sex, body size, and larval instar and lays the basis for further investigation in polyethism. As a social organism, living in a communal structure is one of the most important physical barriers against environmental elements and natural enemies. Thaumetopoea pityocampa (Notodontidae, Thaumetopoeinae) caterpillars are conifer pests that spend most of their larval stage in winter. Although T. pityocampa holds economic and medical significance, the tent construction and foraging behaviour are poorly understood. We observed the tent construction behaviour in autumn (October and November) when third- and fourth-instar T. pityocampa caterpillars build the 'winter tent' that can withstand winter conditions. Just before sunset, with no rain and temperatures over 12 °C, tent construction was undertaken by early active individuals, primarily larger male caterpillars. Early active caterpillars emerge from the tent first and spin silk on the tent for expansion and strength. Once temperatures dropped below 12 °C and twilight had passed, the early active caterpillars went out to forage and were later joined by the late active caterpillars, which were predominantly smaller females that had remained inside the tent. Foraging behaviour was continuously monitored for the first to fourth larval instars in the field. Foraging was more frequent in younger instars when environmental temperatures were warmer and became continuous and prolonged in later instar caterpillars as temperatures dropped. The final tent structure built by later instar caterpillars had the thickest layer of silk on the southern side of the tent compared to other orientations to receive maximum solar radiation during the winter. Our study provided additional insights into the collective nest building, foraging and social behaviours observed in Lepidoptera, as well as the roles of individuals within non-eusocial insect colonies. [ABSTRACT FROM AUTHOR]

Abstract Background The pine processionary moth Thaumetopoea wilkinsoni Tams, 1926 (Lepidoptera: Notodontidae), causes severe skin reactions to animals and humans. The insect also destroys pine ecosystems by feeding on pine leaves at its larval stage. Instead of chemical control, eco-friendly biological control methods should be preferred to combat this species. Results The purpose of this study was to evaluate the efficacy of Beauveria bassiana isolate (GOPT-331) and Metarhizium brunneum isolates (ORP-13 and ORP-18) against the second and fourth larval instars of T. wilkinsoni under laboratory conditions. T. wilkinsoni eggs were collected from pine trees at Ondokuz Mayıs University in Samsun, Turkey, in 2021, and the second and fourth larval instars were used for the experiment. Two milliliters of a spray of the three fungal isolates was applied to the larvae for each concentration (1 × 105–1 × 108 conidia ml−1). The mortality rates of GOPT-331, ORP-13, and ORP-18 were changed between 91.1 and 100% for the second-instar larvae and between 86.6 and 97.7% for the fourth-instar larvae at 1 × 108 conidia ml−1. The ORP-13 isolate showed the lowest LC50 values. Conclusion In conclusion, it is suggested that all the three isolates were virulent to T. wilkinsoni and can be used for biological control of this species. The promising results from the study were obtained from trials conducted under controlled laboratory conditions, and it will be critical to explore the potential of these promising entomopathogenic fungi in field conditions.

Pine species are a key social and economic component in Mediterranean ecosystems, where insect defoliations can have far-reaching consequences. This study aims to quantify the impact of pine processionary moth (PPM) on canopy structures, examining its evolution over time at the individual tree level using high-density drone LiDAR-derived point clouds. Focusing on 33 individuals of black pine (Pinus nigra)—a species highly susceptible to PPM defoliation in the Mediterranean environment—bitemporal LiDAR scans were conducted to capture the onset and end of the major PPM feeding period in winter. Canopy crown delineation performed manually was compared with LiDAR-based methods. Canopy metrics from point clouds were computed for trees exhibiting contrasting levels of defoliation. The structural differences between non-defoliated and defoliated trees were assessed by employing parametric statistical comparisons, including analysis of variance along with post hoc tests. Our analysis aimed to distinguish structural changes resulting from PPM defoliation during the winter feeding period. Outcomes revealed substantive alterations in canopy cover, with an average reduction of 22.92% in the leaf area index for defoliated trees, accompanied by a significant increase in the number of returns in lower tree crown branches. Evident variations in canopy density were observed throughout the feeding period, enabling the identification of two to three change classes using LiDAR-derived canopy density metrics. Manual and LiDAR-based crown delineations exhibited minimal differences in computed canopy LiDAR metrics, showcasing the potential of LiDAR delineations for broader applications. PPM infestations induced noteworthy modifications in canopy morphology, affecting key structural parameters. Drone LiDAR data emerged as a comprehensive tool for quantifying these transformations. This study underscores the significance of remote sensing approaches in monitoring insect disturbances and their impacts on forest ecosystems.

Background: The pine processionary moth Thaumetopoea wilkinsoni Tams, 1926 (Lepidoptera: Notodontidae), causes severe skin reactions to animals and humans. The insect also destroys pine ecosystems by feeding on pine leaves at its larval stage. Instead of chemical control, eco-friendly biological control methods should be preferred to combat this species. Results: The purpose of this study was to evaluate the efficacy of Beauveria bassiana isolate (GOPT-331) and Metarhizium brunneum isolates (ORP-13 and ORP-18) against the second and fourth larval instars of T. wilkinsoni under laboratory conditions. T. wilkinsoni eggs were collected from pine trees at Ondokuz Mayıs University in Samsun, Turkey, in 2021, and the second and fourth larval instars were used for the experiment. Two milliliters of a spray of the three fungal isolates was applied to the larvae for each concentration (1 × 105–1 × 108 conidia ml−1). The mortality rates of GOPT-331, ORP-13, and ORP-18 were changed between 91.1 and 100% for the second-instar larvae and between 86.6 and 97.7% for the fourth-instar larvae at 1 × 108 conidia ml−1. The ORP-13 isolate showed the lowest LC50 values. Conclusion: In conclusion, it is suggested that all the three isolates were virulent to T. wilkinsoni and can be used for biological control of this species. The promising results from the study were obtained from trials conducted under controlled laboratory conditions, and it will be critical to explore the potential of these promising entomopathogenic fungi in field conditions. [ABSTRACT FROM AUTHOR]

The pine processionary moth Thaumetopoea pityocampa is a Lepidopteran pest species occurring in the Western Mediterranean. It causes heavy pine defoliations and it is a public and animal health concern because of its urticating caterpillars. Very little is known about the viruses associated to this species, as only two viruses were described so far. We here present a dataset corresponding to 34 viral transcripts, among which 27 could be confidently assigned to 9 RNA and DNA viral families (Iflaviridae, Reoviridae, Partitiviridae, Permutotetraviridae, Flaviviridae, Rhabdoviridae, Parvoviridae, Baculoviridae and PolyDNAviridae). These transcripts were identified from an original transcriptome assembled for the insect host, using both blast search and phylogenetic approaches. The data were acquired from 2 populations in Portugal and 2 populations in Italy. The transcripts were de novo assembled and used to identify viral sequences by homology searches. We also provide information about the populations and life stages in which each virus was identified. The data produced will allow to enrich the virus taxonomy in Lepidopteran hosts, and to develop PCR-based diagnostic tools to screen colonies across the range and determine the distribution and prevalence of the identified viral species.

The impact of larval and pupal parasitoids of Thaumetopoea pityocampa was studied in laboratory conditions, during the period February-October 2021. The material, 138 hibernating caterpillars of summer form and 415 larvae of winter form intercepted during processions, was collected from two localities -- Dobrostan Vill. and Gotse Delchev, respectively. In the land of Kovil Vill., which is occupied by the winter form, the winter nests of T. pityocampa were checked for infection by parasitoids. In this study, all isolated parasitoids belong to the family Tachinidae. As a result, 3 species -- Phryxe vulgaris (Fallén, 1810), Compsilura concinnata (Meigen, 1824) and Bothria frontosa (Meigen, 1824) were found to parasitized T. pityocampa. A relatively high parasitism rate of T. pityocampa winter form by tachinids was observed -- 21%, of which P. vulgaris parasitized 15.2% of the sample. Conversely, the parasitism rate of T. pityocampa summer form is low -- 5%, in which C. concinnata parasitized 1.4% from the sample. Two puparia of B. frontosa were collected from larval winter nests of T. pityocampa in the region of Kovil Vill. This is the first record of the Notodontidae family as a host of Bothria frontosa. A complete up-to-date list of trophic connections of T. pityocampa with tachinid parasitoids, reported in Bulgarian and international publications is provided, as well as their impact on pest populations. [ABSTRACT FROM AUTHOR]

The tachinid parasitoids (Diptera: Tachinidae) of the pine processionary moth (Thaumetopoea pityocampa) were studied in 2019 and 2020 in the Eastern Rhodopes (Fotinovo, Kandilka and Sarnak vills.), the Western Rhodopes (Dobrostan vill.) and the Struma Valley (town of Sandanski). In total, 1193 larvae and pupae of T. pityocampa were collected in 40-50-year-old Pinus nigra plantations. They were transported and observed in laboratory conditions at 20-22 °С. Three parasitoids, Compsilura concinnata, Exorista (Exorista) fasciata and Phryxe vulgaris were reared from the host. In this study, E. fasciata was established for the first time in trophic association with T. pityocampa. In addition, P. vulgaris was confirmed as a parasitoid of the host. The mortality of the pine processionary moth caused by tachinids in different localities was 0.5-5.3%, with an average of 2.6% for the country.

As a social organism, living in a communal structure is one of the most important physical barriers against environmental elements and natural enemies. Thaumetopoea pityocampa (Notodontidae, Thaumetopoeinae) caterpillars are conifer pests that spend most of their larval stage in winter. Although T. pityocampa holds economic and medical significance, the tent construction and foraging behaviour are poorly understood. We observed the tent construction behaviour in autumn (October and November) when third- and fourth-instar T. pityocampa caterpillars build the ‘winter tent’ that can withstand winter conditions. Just before sunset, with no rain and temperatures over 12 °C, tent construction was undertaken by early active individuals, primarily larger male caterpillars. Early active caterpillars emerge from the tent first and spin silk on the tent for expansion and strength. Once temperatures dropped below 12 °C and twilight had passed, the early active caterpillars went out to forage and were later joined by the late active caterpillars, which were predominantly smaller females that had remained inside the tent. Foraging behaviour was continuously monitored for the first to fourth larval instars in the field. Foraging was more frequent in younger instars when environmental temperatures were warmer and became continuous and prolonged in later instar caterpillars as temperatures dropped. The final tent structure built by later instar caterpillars had the thickest layer of silk on the southern side of the tent compared to other orientations to receive maximum solar radiation during the winter. Our study provided additional insights into the collective nest building, foraging and social behaviours observed in Lepidoptera, as well as the roles of individuals within non-eusocial insect colonies.

The pine processionary moth Thaumetopoea wilkinsoni (Tams, 1926) (Lepidoptera: Notodontidae) is one of the most harmful species that destroys to the pine ecosystem and causes severe skin reactions in humans and animals due to its urticating setae. The aim of this study is to evaluate the efficacy of the hypertoxic strain of Diptera-targeted Bacillus thuringiensis var. israelensis against the second instar larvae of T. wilkinsoni under laboratory conditions. A total of 5 mL of bacterial strain spray was applied to 30 larvae at concentrations of 101, 103, 105, 107, and 109 cfu/mL. As a result of the study, it was determined that the survival rate of the larvae exposed to Bti pHTppk decreased with increasing bacterial concentration, and the survival rate of the 109 cfu/mL concentration group was 33.3%. It is suggested that Bti pHTppk is virulent for T. wilkinsoni larvae and that this strain can be used in the biological control of this species. [ABSTRACT FROM AUTHOR]

In the present work the survival of summer and winter form of pine processionary moth (Thaumetopoea pityocampa) during the hibernation period and the influence of its factors are studied. The investigation was carried out under laboratory conditions at room temperature and natural light. The development of 1224 individuals was followed, of which 708 individuals of the summer form found in the ground (224 hibernating larvae and 484 cocoons) and 516 larvae of the winter form (taken from processions). Prepupae were found in all summer form cocoons excavated at the end of the winter season. In the winter form, an average higher parasitism rate by Tachinidae was observed – 10.5% against 0.6% in the summer one. At the same time, in the summer form the mortality caused by entomopathogenic fungi was much higher – av. 35% against 1% in the winter form. In both phenological forms, the mortality caused by unknown factors (av. 10.7%) was low, as well as the number of unemerged pupae (av. 5.3%). Within the summer form, the mortality caused by entomopathogenic fungi was high – av. 27.7% (larvae) and 37.4% (prepupae), respectively. A significant difference was found in the mortality caused by unknown factors – av. 31.7% (larvae) vs. 2.5% (prepupae). In both hibernating stages of the summer form, the rates of parasitism and unemerged pupae were negligible. [ABSTRACT FROM AUTHOR]

Oecanthus pellucens (Scopoli, 1763) (Gryllidae) is recorded for the first time as a predator on the larvae of Thaumetopoea pityocampa (Denis & Schiffermüller, 1775) (PPM) in Bulgaria. The Italian tree crickets were observed in black pine plantations (Pinus nigra Arn.), in the region of Fotinovo vill. (Eastern Rhodope Mts.), occupied by the PPM summer population.

Climate change profoundly alters the phenology of insects, yet the mechanisms at play remain particularly elusive for univoltine species. Those species typically have to deal with contrasting thermal conditions across their development and life stages occurring at different seasons may have different thermal sensitivity. A modeling framework taking into account stage-specific thermal biology is lacking to predict the effect of climate change on the phenology of such species. Insect development rate scales non-linearly with temperature. This can be described with a thermal performance curve within each developmental stage, enabling higher accuracy near developmental thresholds than linear degree-day models. This approach, however, requires ample data to be correctly estimated. We developed a phenological model based on stage-specific performance curves to predict the phenology of a univoltine species undergoing uninterrupted larval development from summer to next spring, the pine processionary moth (Thaumetopoea pityocampa). This gregarious species is an important pine defoliator and is known to readily respond to climate change with a consistent and sustained range expansion/shift since the 1990s, as winter warming facilitates its survival in previously unsuitable areas. First, we determined the thermal performance curve of development rate for each stage from the egg to the fourth larval instar by monitoring molting in larval colonies exposed to fluctuating thermal treatments in controlled conditions. Second, we developed a phenology model to simulate the cumulated development rate across successive life stages, using observation data of adult flights and daily mean temperatures as input variables. A good fit was found between predictions and observations. Finally, the model was used to explore phenological consequences of hypothetical climate variations. With a simulated increase of temperature by 3°C, the model successfully predicted atypical ends of larval development before winter, which are being observed in nature in some regions or during years with autumnal heatwaves. With a simulated heatwave, carry-over effect on life stages development were predicted. On this winter-active species, we illustrate how variations in development rate caused by climate variations in early development can feedback into subsequent stages typically developing slowly in the cold season.

The tachinid parasitoids (Diptera: Tachinidae) of the pine processionary moth (Thaumetopoea pityocampa) were studied in 2019 and 2020 in the Eastern Rhodopes (Fotinovo, Kandilka and Sarnak vills.), the Western Rhodopes (Dobrostan vill.) and the Struma Valley (town of Sandanski). In total, 1193 larvae and pupae of T. pityocampa were collected in 40-50-year-old Pinus nigra plantations. They were transported and observed in laboratory conditions at 20-22 °?. Three parasitoids, Compsilura concinnata, Exorista (Exorista) fasciata and Phryxe vulgaris were reared from the host. In this study, E. fasciata was established for the first time in trophic association with T. pityocampa. In addition, P. vulgaris was confirmed as a parasitoid of the host. The mortality of the pine processionary moth caused by tachinids in different localities was 0.5-5.3%, with an average of 2.6% for the country. [ABSTRACT FROM AUTHOR]

Abstract Gradients in elevation impose changes in environmental conditions, which in turn modulate species distribution and abundance as well as the interactions they maintain. Along the gradient, interacting species (e.g., predators, parasitoids) can respond to changes in different ways. This study aims to investigate how egg parasitism of a forest pest, the pine processionary moth (PPM), Thaumetopoea pityocampa, vary along an elevational gradient (190–2000 m.a.s.l.) in a mountain range of SE Spain, including areas of recent elevational expansion, for a seven years period (2008–2014). We used generalized linear mixed models to ascertain the effect of both elevation and the winter North Atlantic Oscillation (NAO) index (a proxy of interannual climatic conditions) on the rate of parasitism, and the occurrence probabilities of two parasitoid species: a PPM specialist and a generalist species. Since four pine species are stratified along the elevational gradient, we repeated all the analyses separately for lowlands (190–1300 m. a.s.l.) and uplands (1350–2000 m. a.s.l.). Results showed a decrease in both parasitism rate and probability of occurrence of the two main parasitoid species with elevation, although decline was more severe for the specialist species. The effect of elevation was more conspicuous and intense in uplands than in lowlands. Positive NAO winter values, associated with cold and dry winters, reduced the rate of parasitism and the probability of occurrence of the two main parasitoid species—but particularly for the generalist species—as elevation increases. In a context of climate warming, it is crucial to mitigate PPM elevational and latitudinal expansion. Increasing tree diversity at the PPM expansion areas may favor the establishment of parasitoids, which could contribute to synchronizing host– parasitoid interactions and minimize the risk of PPM outbreaks.

Gradients in elevation impose changes in environmental conditions, which in turn modulate species distribution and abundance as well as the interactions they maintain. Along the gradient, interacting species (e.g., predators, parasitoids) can respond to changes in different ways. This study aims to investigate how egg parasitism of a forest pest, the pine processionary moth (PPM), Thaumetopoea pityocampa, vary along an elevational gradient (190–2000 m.a.s.l.) in a mountain range of SE Spain, including areas of recent elevational expansion, for a seven years period (2008–2014). We used generalized linear mixed models to ascertain the effect of both elevation and the winter North Atlantic Oscillation (NAO) index (a proxy of interannual climatic conditions) on the rate of parasitism, and the occurrence probabilities of two parasitoid species: a PPM specialist and a generalist species. Since four pine species are stratified along the elevational gradient, we repeated all the analyses separately for lowlands (190–1300 m. a.s.l.) and uplands (1350–2000 m. a.s.l.). Results showed a decrease in both parasitism rate and probability of occurrence of the two main parasitoid species with elevation, although decline was more severe for the specialist species. The effect of elevation was more conspicuous and intense in uplands than in lowlands. Positive NAO winter values, associated with cold and dry winters, reduced the rate of parasitism and the probability of occurrence of the two main parasitoid species—but particularly for the generalist species—as elevation increases. In a context of climate warming, it is crucial to mitigate PPM elevational and latitudinal expansion. Increasing tree diversity at the PPM expansion areas may favor the establishment of parasitoids, which could contribute to synchronizing host– parasitoid interactions and minimize the risk of PPM outbreaks. [ABSTRACT FROM AUTHOR]

Within the framework of finding new biological control methods to suppress allergic effects of pine processionary moth (PPM), Thaumetopoea wilkinsoni Tams, less toxic and environmentally friendly, entomopathogenic fungi and essential oils are considered to be an alternative to chemical insecticides. The aim of the present study was to investigate the effects of essential plant oils and two isolates of Metarhizium brunneum (V275 and ARSEF4556) on PPM larvae and pupae under field and controlled laboratory conditions. PPM larvae inside the nest and late instar larvae preparing to pupate were highly susceptible to both strains of M. brunneum, which caused 100% mortality in the laboratory and 45–100% mortality in field trials. The insecticidal effects of essential oils (ginger, eucalyptus and rosemary) on the first, third and fourth instar larvae of PPM were proportional to dosage and life stage of insect. Ginger oil diluted in water was toxic to first instar larvae even at a dose as low as 1% and 3% (v/v). Field trials showed that injection of essential oils into nests of third instar larvae caused significant mortality (87.4%) but <5% mortality of fourth instar larvae. Surface application of all essential oils at a concentration of 5% killed half of the larvae in one day, while 1% concentration caused from 0% to 20% mortality. Only 1% ginger caused 63% mortality at the end of the trial. This study shows that ginger oil and M. brunneum strains ARSEF 4556 and V275 show promise for the control of PPM larvae under field conditions. [ABSTRACT FROM AUTHOR]

The dynamics of the larval emergence of the "summer form" and "winter form" of Thaumetopoea pityocampa was studied in the period July-October 2020 in laboratory conditions. The biological material was collected from two sampling sites - Sandanski in the western foothills of Prirn Mts. and Dobrostan on the northern slope of the Rhodopes Mts. The region of Sandanski is occupied by the winter form and the region of Dobrostan - by the summer form. The phenological calendars of the two populations of T. pityocampa were found to be in agreement with the known temperature thresholds of the species. The culmination of the larvae hatching of the winter form was in early October - well after midsummer heats, while the culmination of the summer forms was in early August and coincided with the hottest period. In both populations, however, the culmination of hatching occurred at average monthly maximum air temperatures of about 28°C. [ABSTRACT FROM AUTHOR]

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Oecanthus pellucens (Scopoli, 1763) (Gryllidae) is recorded for the first time as a predator on the larvae of Thaumetopoea pityocampa (Denis & Schiffermüller, 1775) (PPM) in Bulgaria. The Italian tree crickets were observed in black pine plantations (Pinus nigra Arn.), in the region of Fotinovo vill. (Eastern Rhodope Mts.), occupied by the PPM summer population. [ABSTRACT FROM AUTHOR]

In the Mediterranean and temperate regions, an increase in the frequency and intensity of drought events has been recorded, probably due to climate change. In consequence, trees will more frequently experience hydric stress, a condition that can be expected to affect insect–tree interactions, while adaptation mechanisms may be further in course. The effect of tree water stress on the performance of two allochronic populations of Thaumetopoea pityocampa was here studied. Namely, we compared a unique population of this insect, in which the larvae develop in the summer (SP), with the typical population having winter larval development (WP), to test the adaptation hypothesis to host plant status. Larvae of each population were fed on needles of young potted Pinus pinaster plants under two water supply regimes: (i) well-watered (control) and (ii) subjected to 3 months of drought stress. Compared to control, stressed plants had higher amounts of soluble sugars, phenols, and higher C/N ratio, whereas water content and chlorophylls concentrations were lower. In general, T. pityocampa larvae had lower performances on water-stressed plants, as shown by lower survival rates, lower needle consumption, and longer development times. Yet, the detrimental effects of tree stress were only significant for the WP larvae, while SP larvae were able to overcome such conditions. Results demonstrate that tree water stress can negatively affect T. pityocampa populations. Furthermore, the evidence is also provided that responses to the physiological condition of the host trees may occur at the population level, as a result of adaptation mechanisms driven by climate change. [ABSTRACT FROM AUTHOR]

The pine processionary moth, Thaumetopoea pityocampa (Denis and Schiffermüller), is an important insect in the Mediterranean region, as it defoliates pines and its urticating hairs can cause allergic reactions in humans and animals. Moreover, this species exhibits an interesting genetic structure as recently a distinct East-North African mtDNA lineage ('ENA clade') has been described. This clade has been recently detected in Greek populations where it has currently expanded its range by replacing the 'endemic' T. pityocampa lineages. Here, we report new data on the rapid spread of 'ENA clade' in the Greek island Evoia in only a few years. As the underlying mechanisms of the 'ENA clade' range expansion has not been studied so far, we screened T. pityocampa for an infection with the heritable bacterial endosymbionts Wolbachia (Bacteria: Anaplasmataceae), Cardinium (Bacteria: Bacteroidaceae), Rickettsia (Bacteria: Rickettsiaceae) and Spiroplasma (Bacteria: Spiroplasmataceae). These bacteria can manipulate the reproduction of infected hosts, something that could potentially explain the rapid spread of 'ENA clade' lineage. Therefore, we screened 28 individuals that exhibited T. pityocampa 'ENA clade' and 'endemic' T. pityocampa haplotypes from nine populations scattered all over Greece. None of them was infected with any of the four endosymbionts, suggesting that these bacteria do not cause reproductive manipulations in T. pityocampa lineages and, thus, other factors should be explored in future research efforts. [ABSTRACT FROM AUTHOR]

In this study, Metarhizium anisopliae TR 106 and Beauveria bassiana TR 217 was tested against fourth instar larvae of Thaumetopoea pityocampa. The LT50 and LT90 of 1 × 106 concentration of M. anisopliae against T. pityocampa were 3.60 and 4.11 for direct application, while these were 2.87 and 3.60 days, respectively in leaves application. The LT50 and LT90 of the 1 × 108 concentration of the same isolate were 2.50 and 2.95 days for direct application, and 2.98 and 3.74 days for leaves application. The LT50 of insect and leaves application for 1 × 106 of B. bassiana were 3.75 and 3.49 days, respectively. The LT90 of same concentration for insect application was 4.48 days, while LT90 for leaves application was 4.63 days. Similarly, LT50 of insect and leaves application for 1 × 108 of B. bassiana were 3.03 and 3.31 days, while LT90 were 3.68 and 4.29 days, respectively. Approximate 100% mycosis was observed in all treatments. [ABSTRACT FROM AUTHOR]

Pine processionary moth is one of the most important forest pests in the Mediterranean Basin. There is need to explore its distribution behaviour to undertake effective control and determine the edge effect of its horizontal distribution in the stand. Five trial sites damaged by the insect were selected and traps installed in all trees in the sites. The number of nests and larvae was counted and diameter increment cores were taken. The distance to the edge of the stand revealed that there was no statistical difference in the number of nests and larvae up to 25 m while there was a statistically significant difference (0.5%) at > 25 m. There was a 2-fold difference in the density of nests between 0 and 25 m and > 25 meters, and a 3.8-fold difference in the number of larvae. The effect of pine processionary moth on tree diameter was not significant between trees at the edge of the stand and those in the stand. [ABSTRACT FROM AUTHOR]

Changing climate conditions have allowed the pine processionary moth [Thaumetopoea pityocampa (Den. & Schiff. 1775) (Lepidoptera: Notodontidae: Thaumetopoeidae) and T. wilkinsoni Tams. 1925 (Lepidoptera: Notodontidae: Thaumetopoeidae)] which is one of the most important insects in Mediterranean forest ecosystems, to distribute to larger areas. More effective control of this moth is necessary to prevent its expansion to northern and higher altitudes. Mechanical, biological, chemical, and biotechnical control methods are currently being applied. These methods are either not effective alone, are very expensive, have low impact, or are problematic with respect to the environmental and human health. The purpose of this study was to develop a new approach to control the pine processionary moth and to develop an economical, ecological, and effective trap exploiting its behavioural characteristics. Traps attached to tree trunks caused mature larvae to be trapped as they landed on the soil in convoys to become pupa. In 2013, the average number of nests per tree was 4.7, while it decreased to 2.0 in 2015; furthermore, the average number of larvae decreased from 265 to 57. As a result of this 3-year study, it was found that these traps could catch nearly all of the adult larvae and reduce the moth population; it was also evident that these traps can be used as a new alternative method to control the pine processionary moth, alone or in combination with other methods. [ABSTRACT FROM AUTHOR]

Terpenoids make up the biggest and most diversified class of chemical substances discovered in plants, encompassing over 40,000 individual compounds. In conifers, the production of terpenoids, either as oleoresin or emitted as volatile compounds, play an important role in the physical and chemical defence responses against pathogens and herbivores. In the present work, we examined, for the first time to the best of our knowledge, the terpenic defensive relations of Calabrian pine (Pinus nigra subsp. laricio (Poiret) Maire), facing the attack of the pine processionary moth (Thaumetopoea pityocampa (Denis and Schiffermüller, 1775)), brought about in the open on adult plant individuals growing at two distinct forest sites. Among the volatile terpenoids emitted from pine needles, bornyl acetate [(4,7,7-trimethyl-3-bicyclo[2.2.1]heptanyl) acetate] was the most frequently and selectively associated with the infestation, increasing during the period of most intense trophic activity of the caterpillars (defoliation), and decreasing thereafter. Although further work is needed to clarify whether the observed response reflects defence reactions and/or they are involved in communication among the infested plants and their biotic environment, the present results boost the currently growing interest in the isolation and characterization of plant secondary metabolites that can be used to control pests, pathogens, and weeds.

The variegated caper bug (CB) Stenozygum coloratum (Klug, 1845) is common in the Eastern Mediterranean region and a minor agricultural pest. CB eggs were recently shown to serve as alternative hosts for Ooencyrtus pityocampae Mercet, 1921, an important natural enemy of the pine processionary moth (PPM) Thaumetopoea wilkinsoni Tams, 1924 (Lepidoptera: Notodontidae). In this study various aspects of the life history of CB were studied, including its distribution, host range, development, reproduction and ability to develop on various cultivated species of plants. CB occurs in almost all areas and habitats in Israel, except in the coldest regions, attacking several caper species (Capparis spp.). When reared on Capparis zoharyi at 25°C, one generation lasted 6 weeks and females laid a single 12-egg cluster every 3 days. Decreases in temperature, but not changes in day length, terminated reproductive activity. CB nymphs survived for up to three months, or even completed their development, on some agricultural plants. However, reproductive activity was initiated only if adults were fed capers. These findings emphasize the importance of capers in the CB life cycle and account for why other plants are rarely attacked. These plants may serve as a temporary refuge for CB when capers are scarce or unsuitable, mainly late in the season. Morphology of developmental stages, egg deposition, cannibalistic behaviour, sex ratio and effects of temperature on egg production were also studied. The possibility of using CB for enhancing the biological control of PPM is discussed.

Thaumetopoea pityocampa (pine processionary moth) is one of the most important pine pests in the forests of Mediterranean countries, Central Europe, the Middle East and North Africa. Apart from causing significant damage to pinewoods, T. pityocampa occurrence is also an issue for public and animal health, as it is responsible for dermatological reactions in humans and animals by contact with its irritating hairs. High throughput sequencing technologies have allowed the fast and cost-effective generation of genetic information of interest to understand different biological aspects of non-model organisms as well as the identification of potential pathogens. Using these technologies, we have obtained and characterized the transcriptome of T. pityocampa larvae collected in 12 different geographical locations in Turkey. cDNA libraries for Illumina sequencing were prepared from four larval tissues, head, gut, fat body and integument. By pooling the sequences from Illumina platform with those previously published using the Roche 454-FLX and Sanger methods we generated the largest reference transcriptome of T. pityocampa. In addition, this study has also allowed identification of possible viral pathogens with potential application in future biocontrol strategies.

Résumé Les forêts de l’Atlas saharien représentent la bordure sud des aires de distribution naturelle du pin d’Alep (Pinus halepensis Mill.). Elles sont exposées à un stress climatique lié à la sécheresse et aux attaques de la chenille processionnaire (CP, Thaumetopoea pityocampa Schiff.). L’objet de notre travail consiste à étudier la variation du taux d’infestation par la CP et la densité de celle-ci en utilisant des facteurs climatiques et les paramètres dendrométriques. Le taux d’infestation par la CP (7,82 %) et la densité de celle-ci (2,74 ± 2,61 nids/arbre) ont été moins importants dans nos pinèdes que dans celles du nord. Il est apparu que les attaques de CP augmentent principalement avec la baisse du nombre de jours de gelée et de canicule. Les paramètres dendrométriques ont été négativement corrélés avec la densité de CP par arbre. En revanche, cette dernière a été positivement corrélée avec le taux de défoliation. Les résultats ont été discutés dans un cadre biogéographique à la lumière des connaissances sur la répartition de la CP du pin d’Alep et en relation avec les conditions climatiques. Abstract The forests of the Saharan Atlas represent the southern edge of the natural range of the Aleppo pine (Pinus halepensis Mill.). These are exposed to climatic stress in relation to drought and attacks of the pine processionary moth (Thaumetopoea pityocampa Schiff., denoted by CP in the French text). The purpose of our work is to study the variation of the infestation rate by the pine processionary moth and its density with climatic factors and dendrometric parameters. The infestation rate (7.82%) by the pine processionary moth and its density (2.74 ± 2.61 nests/tree) were lower in our pine forests than in the northern ones. It appeared that the attacks of the moth increase mainly with the number of days of frost and heatwave. The dendrometric parameters were negatively correlated with the moth's density per tree. On the other hand, the latter was positively correlated with the defoliation rate. The results were discussed in a biogeographic framework in the light of the current knowledge of the distribution of the pine processionary moth in the Aleppo pine, in relation with the climatic conditions. [ABSTRACT FROM AUTHOR]

Bioassays were conducted to determine the susceptibility of egg masses and young larvae of two pine processionary moth species, Thaumetopoea pityocampa and Thaumetopoea wilkinsoni, to two strains (ARSEF4556, V275) of the entomopathogenic fungus Metarhizium brunneum. Mortality of treated eggs by both strains ranged from 96% to 99% but not all of this was caused by M. brunneum since control groups also experienced egg mortality due to saprophytic fungi. Still, larvae hatched in the laboratory from eggs treated with M. brunneum were all killed by this fungus, acquiring M. brunneum conidia, whereas larval mortality was 0% in the control groups. Young larvae of both pine processionary moth species were also highly susceptible to ARSEF4556 and V275 with larval mortality ranging between 94% and 100%, 8 days post-inoculation, with the vast majority of larvae being killed within the first 2-4 days. Larval mortality was dose dependent. Results were consistent across the two pine processionary moth species, showing that the pathogenicity of M. brunneum to both eggs and young larvae might be promising for biological control of these insect pests. The study also showed that non-target parasitoids of pine processionary moth eggs were also susceptible to M. brunneum. Further work is required to understand and reduce the M. brunneum effect on non-target insects. [ABSTRACT FROM AUTHOR]

Microbial communities associated to the gut of insects are attracting an increasing interest, mainly because of their role in influencing several host life-traits. The characterization of the gut microbial community is pivotal for understanding insect ecology and, thus, to develop novel pest management strategies. The pine processionary moth, Thaumetopoea pytiocampa (Denis & Schiff.) (Lepidoptera: Thaumetopoeidae), is a severe defoliator of pine forests, able to feed on several pine species. In this work, we performed a metabarcoding analysis to investigate, for the first time, the diversity of the gut bacterial community of pine processionary larvae associated with three different host pine species ( Pinus halepensis, Pinus nigra subsp. laricio, and Pinus pinaster). We found that the gut microbial community of T. pityocampa larvae collected on P. halapensis was different from that associated with larvae collected from P. nigra and P. pinaster. Moreover, the high presence of bacteria belonging to the genera Modestobacter, Delftia, and unidentified Methylobacteriaceae retrieved in larvae feeding on P. halapensis suggested that specific interactions can occur. Our results provide the evidence that different host plant differently impact on the microbiota diversity of T. pityocampa larvae, contributing to the general knowledge of this pest with information that could be useful in shaping the next generation of pest control strategies. [ABSTRACT FROM AUTHOR]

The winter pine processionary moth complex includes some major defoliating insects of Pinus and Cedrus forests in southern Europe and the Mediterranean Basin, where they also cause health problems to humans and animals., The complex includes at least two species that were separated recently based on molecular and morphological evidence: Thaumetopoea pityocampa in the west and Thaumetopoea wilkinsoni in the east of the Mediterranean Basin., Individuals from two populations, selected as representative of Th. pityocampa and Th. wilkinsoni, were used to test whether hybridization is possible under controlled conditions., The hybrid offspring showed intermediate morphological and performance traits, whereas heterosis for pupal weight was detected in one of the hybrid lines. The genetic analysis confirmed the crosses., Both species have large phenological plasticity and may come into contact at the edge of their range, where they could hybridize., Based on the evidence accumulated so far, it is recommended that the current species designations are maintained, although a deeper study of the trait variability is required, especially in the contact zones. [ABSTRACT FROM AUTHOR]

Abstract: Understanding the processes of adaptive divergence, which may ultimately lead to speciation, is a major question in evolutionary biology. Allochronic differentiation refers to a particular situation where gene flow is primarily impeded by temporal isolation between early and late reproducers. This process has been suggested to occur in a large array of organisms, even though it is still overlooked in the literature. We here focused on a well‐documented case of incipient allochronic speciation in the winter pine processionary moth Thaumetopoea pityocampa. This species typically reproduces in summer and larval development occurs throughout autumn and winter. A unique, phenologically shifted population (SP) was discovered in 1997 in Portugal. It was proved to be strongly differentiated from the sympatric “winter population” (WP), but its evolutionary history could only now be explored. We took advantage of the recent assembly of a draft genome and of the development of pan‐genomic RAD‐seq markers to decipher the demographic history of the differentiating populations and develop genome scans of adaptive differentiation. We showed that the SP diverged relatively recently, that is, few hundred years ago, and went through two successive bottlenecks followed by population size expansions, while the sympatric WP is currently experiencing a population decline. We identified outlier SNPs that were mapped onto the genome, but none were associated with the phenological shift or with subsequent adaptations. The strong genetic drift that occurred along the SP lineage certainly challenged our capacity to reveal functionally important loci. [ABSTRACT FROM AUTHOR]

Geographical variation in forest insect sensitivity to environmental conditions is often overlooked. Yet considering regional variation in response to climate is necessary to better predict the consequences of climate change on pest population dynamics and associated damage. We investigated the climatic drivers of demographic fluctuations in a forest tree defoliator, the pine processionary moth (PPM), in 8 biogeographical regions in France. We studied the effects of precipitation and temperature for both cold and warm periods, in accordance with PPM biology. We trained second-order log-linear models of infestation dynamics based on records spanning over 32 years (1981–2014) and 1239 forest plots, and tested their forecast accuracy on two additional years (2013–2014). PPM population growth rate decreased with higher precipitations in 5 regions and increased with increasing temperatures in the cold period in 4 regions. The magnitude and direction of temperature effects in the warm period varied among biogeographical regions. Our results also revealed that PPM population dynamics were largely triggered by density-dependent factors independent from climatic drivers. Short-term forecasts were generally accurate irrespective of the inclusion of climatic variables into the models. To better predict the consequences of climate change on insect population dynamics, it is advisable to take geographical variability of species response into account and develop regional forecasting models. [ABSTRACT FROM AUTHOR]

The larvae of the pine processionary moth (PPM),Thaumetopoea pityocampa, feed on the needles of pine and cedar. The urticating hairs of older instars pose a threat to human and animal health. Strains of the entomopathogenic fungi,Metarhizium brunneum(V275, ARSEF 4556) andBeauveria bassiana(KTU-24), were assayed against first to fourth instarT. pityocampausing doses ranging from 1 × 105to 1 × 108conidia mL−1. The three strains differed slightly in their virulence but caused 100% mortality of all instars at the highest dose. The newly emerged or first instar larvae were extremely susceptible with 100% mortality being achieved 2–4 days post inoculation with V275 at all but the lowest dose. The fourth instar larvae appeared to be less susceptible than earlier instars. There was good horizontal transmission of conidia from treated to un-inoculated larvae. However, mortality was higher in third and fourth instars and where the ratio of inoculated versus untreated larvae was high. This we presume is due to spores being more readily trapped by the urticating hairs found on third and older instar larvae. Injection of the nests offers a simple and environmentally friendly way of controlling the pest with reduced risk to operators. [ABSTRACT FROM PUBLISHER]

Pine processionary moth (PPM) is one of the most destructive insect defoliators in the Mediterranean for many conifers, causing losses of growth, vitality and eventually the death of trees during outbreaks. There is a growing need for cost-effective monitoring of the temporal and spatial impacts of PPM in forest ecology to better assess outbreak spread patterns and provide guidance on the development of measures targeting the negative impacts of the species on forests, industry and human health. Remote sensing technology mounted on unmanned aerial systems (UASs) with high-resolution image processing has been proposed to assess insect outbreak impacts at local and forest stand levels. Here, we used UAS-acquired RGB imagery in two pine sites to quantify defoliation at the tree-level and to verify the accuracy of the estimates. Our results allowed the identification of healthy, infested and completely defoliated trees and suggested that pine defoliation estimates using UASs are robust and allow high-accuracy (79%) field-based infestation indexes to be derived that are comparable to those used by forest technicians. When compared to current field-based methods, our approach provides PPM impact assessments with an efficient data acquisition method in terms of time and staff, allowing the quantitative estimation of defoliation at tree-level scale. Furthermore, our method could be expanded to a number of situations and scaled up in combination with satellite remote sensing imagery or citizen science approaches. [ABSTRACT FROM AUTHOR]

Habitat selection is especially important for pupae of holometabolous insects because this stage is usually immobile and to a certain extent unable to react to environmental changes. In the present study, we analyze how habitat and soil moisture determine the fate of pupae of the pine processionary moth Thaumetopoea pityocampa, a defoliator pest in pine woodlands of Europe and the Circunmediterranean region. The pine processionary moth pupates buried in the soil and can spend up to 9 years in an extra-long diapause., We considered the impact that different habitats, as well as the manipulation of soil water conditions in the preferred habitat (i.e. in bare ground with null or sparse herbaceous vegetation), can exert on pupation., Less than half of the buried larvae successfully pupated, even in the most favourable habitats and soil water conditions, whereas, on average, 2.5% underwent extra-long pupae diapause (2 years after pupation)., Although habitat influenced mainly pupation success and pupal survival, changing moisture conditions in the preferred habitat affected primarily the phenology of emergence, whereas pupal survival remained unaffected., The results of the present study reveal the importance of both habitat and soil moisture on the pupal stage, providing valuable information with respect to adequately forecasting the effects of changes in climate or land use on the population dynamic of this important forest pest. [ABSTRACT FROM AUTHOR]

There are two tested hypotheses related to past distribution of the eastern pine processionary moth, Thaumetopoea wilkinsoni, which is one of the most destructive forest pests, in the Anatolian peninsula. One of them posits that the eastern pine processionary moth expanded its range from south to north of Anatolia, and the other one posits that this range expansion occurred during the last 100 years due to heavy afforestation practices in the region. The latter hypothesis was disproved by using the information obtained from both the documents that has waited its time until today in the Ottoman archives and also notes of a German traveler and lepidopterist, Albert Kindermann, who visited Anatolia in the 19th century. According to this proof, the eastern pine processionary moth occurred in Anatolia long before the hypothesis posits. Testing the first hypothesis was conducted through genetic tools. Analyses of mitochondrial DNA revealed that the eastern pine processionary moth expanded its range from south to north, similar to most of the species in Anatolia. This finding, which looks like one of the most important characteristics of the Anatolian biogeography, is most probably a consequence of recolonization of regions that become temperate and favorable after the Last Glacial Maximum. [ABSTRACT FROM AUTHOR]

The realized host range of herbivores is expected to increase with herbivore population density. Theory also predicts that trait similarity and phylogenetic relatedness between native and exotic plants is expected to increase the susceptibility of introduced plants to feeding by native herbivores. Whether the ability of native herbivores to extend their host range to introduced species is density dependent is still unknown. We addressed this question by monitoring pine processionary moth (PPM, Thaumetopoea pityocampa) attacks during nine consecutive years on 41 pine species (8 native and 33 introduced) planted in an arboretum. The survey encompassed latent and outbreak periods. A total of 28 pine species were attacked by PPM. There was no difference in the probability of attack between native and introduced pine species. Host range increased and was more phylogenetically clustered during outbreak than latent periods. When population density increased, PPM expanded its diet breadth by attacking introduced pine species that were closely related to native hosts. This study demonstrates the density dependence of host range expansion in a common pine herbivore. Importantly, it supports the idea that the degree of phylogenetic proximity between host species can be a better predictor of attacks than the introduction status, which may help to predict the outcomes of new plant-herbivore interactions. [ABSTRACT FROM AUTHOR]