Global change is expected to modify the frequency and magnitude of defoliating insect outbreaks in forest ecosystems. Bats are increasingly acknowledged as effective biocontrol agents for pest insect ...populations. However, a better understanding is required of whether and how bat communities contribute to the resilience of forests to man- and climate-driven biotic disturbances.We studied the responses of forest insectivorous bats to a major pine defoliator, the pine processionary moth Thaumetopoea pityocampa, which is currently expanding its range in response to global warming corrected. We used pheromone traps and ultrasound bat recorders to estimate the abundance and activity of moths and predatory bats along the edge of infested pine stands. We used synthetic pheromone to evaluate the effects of experimentally increased moth availability on bat foraging activity. We also evaluated the top-down regulation of moth population by estimating T. pityocampa larval colonies abundance on the same edges the following winter. We observed a close spatio-temporal matching between emergent moths and foraging bats, with bat activity significantly increasing with moth abundance. The foraging activity of some bat species was significantly higher near pheromone lures, i.e. in areas of expected increased prey availability. Furthermore moth reproductive success significantly decreased with increasing bat activity during the flight period of adult moths. These findings suggest that bats, at least in condition of low prey density, exhibit numerical and functional responses to a specific and abundant prey, which may ultimately result in an effective top-down regulation of the population of the prey. These observations are consistent with bats being useful agents for the biocontrol of insect pest populations in plantation forests.
•How defoliating insects affect Mediterranean pine forests in the long term?•We used a 43-year long field survey of pine processionary moth (PPM) defoliation.•We assessed growth and cover by using ...tree-ring and Landsat remote-sensing data.•Several vegetation indices reflected the PPM defoliations.•Dendroecology and remote sensing allow detecting PPM outbreaks in pine forests.
Outbreak insects are among the major biotic disturbances affecting Mediterranean forests by reducing their growth and vitality through severe defoliations. Despite their relevance for the management of these drought-prone areas, we lack information on the relationships between growth, canopy cover and insect defoliations at ample spatial and temporal scales. Here, we combine remote sensing (vegetation indexes) and dendrochronological information (basal area increment, BAI) to assess the effects of pine processionary moth (Thaumetopoea pityocampa, PPM) defoliations on growth and cover changes of several pine species, mainly focusing on Pinus nigra. We compared both datasets with a long-term field survey of PPM stand defoliations carried out in eastern Spain during the period 1970–2012. Lastly, we fitted linear-mixed models of BAI using as predictors climatic variables and a multi-scalar drought index to distinguish drought-related growth reductions from those attributed to PPM outbreaks. PPM severe defoliations mainly affected edge or low-density stands. Several vegetation indices (Moisture Stress Index, Normalized Burn Ratio and Normalized Difference Infrared Index) reflected the cover decrease corresponding to severe PPM defoliations. We found that trees affected by various severe PPM defoliations took at least 2years to recover BAI values similar to those observed before the outbreak. The combined use of remote sensing and dendrochronology allows monitoring the impact of PPM defoliations from stands to trees, and these are valuable approaches to forecast outbreaks and their effects on Mediterranean forest. We consider both powerful tools to further assess the interacting effects of climate warming and PPM dynamics on drought-prone forests.
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-bicyclo2.2.1heptanyl) 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.
Climate warming is inducing dramatic changes in species distribution. While many studies report the poleward range expansion of some species, some others report the range retraction and extinction ...risk of other species. Here we explore how climate warming affects the southern edge in North Africa of the pine processionary moth,
Thaumetopoea pityocampa
, which is a model insect currently expanding northwards and toward higher elevation in Europe. This Mediterranean forest insect was found in southern Tunisia until 2003. Field surveys were conducted to map the current southern edge of the species in Tunisia. Pheromone traps were installed on a north-south gradient, a translocation experiment of egg masses was conducted on this gradient, and local temperature change was analyzed. We thus proved that the pine processionary moth has disappeared from southern Tunisia, and that no more adult males were actually flying there. We also found a decrease of egg hatching and of the proportion of individuals able to reach larval stages along this gradient, while daily minimal and maximal temperatures globally increased. Furthermore, we showed that daily maximal and minimal temperatures as well as indices of extremely high temperatures have substantially increased during the study period (1980–2019). This study reveals the retraction of the pine processionary moth from southern Tunisia due to higher mortality rates that could be attributed to a significant local warming. The role of other factors (mainly the response of host trees and natural enemies to climate change) may amplify this direct effect and should be further explored.
Divergence between populations sharing the same habitat can be initiated by different reproductive times, leading to allochronic differentiation. A spatially localized allochronic summer population ...(SP) of the pine processionary moth Thaumetopoea pityocampa, recently discovered in Portugal, occurs in sympatry with the local winter population (WP). We examined the level of genetic differentiation between the two populations and estimated the current gene flow within the spatial framework of their co‐occurrence. Mitochondrial data indicated that the two sympatric populations were genetically closer than other WP populations. Conversely, microsatellite genotyping uncovered greater differentiation between the two sympatric populations than between allopatric ones. While male trapping confirmed that reproduction of SP and WP occurred at distinct times, clustering approaches demonstrated the presence of a few LateSP individuals emerging within the WP flight period, although genetically identified as SP. We also identified rare recent hybridization events apparently occurring mainly in the margins of the current SP range. The ongoing gene flow detected between the ancestral and the emerging allochronic populations revealed an incomplete reproductive isolation, which must therefore be taken into account and integrated with studies focussed on ecological drivers, so that a complete understanding of the ongoing speciation process might be achieved.
Climate change affects the life cycle of many species. Yet, responses to yearly variation of weather can either help species track optimal conditions or be maladaptive.
We analysed phenological data ...of 46,479 pine processionary moths (Thaumetopoea pityocampa) during 15 years along an altitudinal gradient in southern France. These larvae were sampled in situ and allowed to pupate in a common garden at lower elevation.
Individuals originating from higher elevation emerged earlier than those sampled at low elevation, which suggests local adaptation. Yearly variations in temperature also affected phenology. Warm springs caused an earlier adult emergence, while autumn temperatures had an opposite effect. Environmental cues could thus induce contradictory plastic responses.
Synchronization mechanisms were identified. Variability in the duration of the pupal phase is a key parameter to synchronize adult emergence in spite of different larval development rates that only marginally influenced emergence dynamics. Semivoltine individuals experiencing prolonged diapause were synchronized with univoltine individuals emerging the same year.
These data highlight some contradiction in the effect of spatial versus temporal variations of the temperature on adult emergence. This suggests that phenological responses to the current climate change cannot easily be anticipated by space‐for‐time substitution designs.
Mapping species spatial distribution using spatial inference and prediction requires a lot of data. Occurrence data are generally not easily available from the literature and are very time-consuming ...to collect in the field. For that reason, we designed a survey to explore to which extent large-scale databases such as Google maps and Google Street View could be used to derive valid occurrence data. We worked with the Pine Processionary Moth (PPM) Thaumetopoea pityocampa because the larvae of that moth build silk nests that are easily visible. The presence of the species at one location can therefore be inferred from visual records derived from the panoramic views available from Google Street View. We designed a standardized procedure allowing evaluating the presence of the PPM on a sampling grid covering the landscape under study. The outputs were compared to field data. We investigated two landscapes using grids of different extent and mesh size. Data derived from Google Street View were highly similar to field data in the large-scale analysis based on a square grid with a mesh of 16 km (96% of matching records). Using a 2 km mesh size led to a strong divergence between field and Google-derived data (46% of matching records). We conclude that Google database might provide useful occurrence data for mapping the distribution of species which presence can be visually evaluated such as the PPM. However, the accuracy of the output strongly depends on the spatial scales considered and on the sampling grid used. Other factors such as the coverage of Google Street View network with regards to sampling grid size and the spatial distribution of host trees with regards to road network may also be determinant.
Insect bites and Lepidopterism are a major sensitization hazard for forestry workers. In recent years, different species of the genus Thaumetopoea are expanding their habitat in Bulgaria and ...represent a serious health threat for people working in the forests. The present epidemiological pilot study aims to investigate the specific sensitization of the forestry workers to the caterpillars of the most spread Thaumetopoea species in Bulgaria, as well as to evaluate their hypersensitivity to a range of inhalant, insect and food allergens.Thirty four forestry workers (28 men and 6 women) were surveyed. The sensitization to pine processionary (Thaumetopoea pityocampa); oak processionary (Thaumetopoea processionea) and Thaumetopoea solitaria was assessed by skin prick tests. Blood samples were taken for determination of total and allergen-specific IgE against a range of inhalant, insect and food allergens. Fourteen (41%) of the forestry workers reported skin rash, itching, runny nose and sneezing during their daily professional activities in the forest. Sixteen (47%) were sensitized to one or more representatives of the Thaumetopoeidae family. The most common is poly-sensitization to all three Thaumetopoea species - in 6 (38%), as well as mono-sensitization to pine processionary - in other 5 (31%). In 13 (39%) increased levels of total IgE, were found. A prevalence of insect allergy was also found. In conclusion, this pilot study provided important information on the impact of the different Thaumetopoea species on the health of the forestry workers. It also outlined the key role of different environmental allergens for the development of symptoms of IgE-mediated allergy and the need for more detailed epidemiologic and allergologic study on the medico-social importance of the sensitization to Thaumetopoea species.
Assessing and reconstructing the impacts of defoliation caused by insect herbivores on tree growth, carbon budget and water use, and differentiating these impacts from other stresses and disturbances ...such as droughts requires multi-proxy approaches. Here we present a methodological framework to pinpoint the impacts of pine processionary moth (
Thaumetopoea pityocampa
), a major winter-feeding defoliator, on tree cover (remote-sensing indices), radial growth and wood features (anatomy, density, lignin/carbohydrate ratio of cell walls, δ
13
C and δ
18
O of wood cellulose) of drought-prone pine (
Pinus nigra
) forests in north-eastern Spain. We compared host defoliated (D) and coexisting non-defoliated (ND) pines along with non-host oaks (
Quercus faginea
) following a strong insect outbreak occurring in 2016 at two climatically contrasting sites (cool-wet Huesca and warm-dry Teruel). Changes in tree-ring width and wood density were analyzed and their responses to climate variables (including a drought index) were compared between D and ND trees. The Normalized Difference Infrared Index showed reductions due to the outbreak of –47.3% and –55.6% in Huesca and Teruel, respectively. The D pines showed: a strong drop in growth (–96.3% on average), a reduction in tracheid lumen diameter (–35.0%) and lower lignin/carbohydrate ratios of tracheid cell-walls. Both pines and oaks showed synchronous growth reductions during dry years. In the wet Huesca site, lower wood δ
13
C values and a stronger coupling between δ
13
C and δ
18
O were observed in D as compared with ND pines. In the dry Teruel site, the minimum wood density of ND pines responded more negatively to spring drought than that of D pines. We argue that multi-proxy assessments that combine several variables have the potential to improve our ability to pinpoint and reconstruct insect outbreaks using tree-ring data.
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.
PDF
