Moth Density Research Articles

Conservation Biological Control of Codling Moth (Cydia pomonella): Effects of Two Aromatic Plants, Basil (Ocimum basilicum) and French Marigolds (Tagetes patula).

Simple SummaryIntercropping apple trees with aromatic plants is a way to attract natural enemies and strengthen biological control services. However, the effects of aromatic plants are still unclear under field conditions. Here, we studied the potential of two aromatic plant species to promote codling moth natural enemies in a full factorial experiment. Ocimum basilicum increases codling moth parasitism. Tagetes patula has a general negative effect on both the codling moth and its natural enemies. We do not find a reduction in codling moth density or damaged apples on trees associated with aromatic plants.The addition of flowering companion plants within or around crop fields is a promising strategy to strengthen pest regulation by their natural enemies. Aromatic plants are frequently used as companion plants, but their effects on natural enemies remain unclear under field conditions. Here, we evaluated the effects of two aromatic plant species on the parasitism of the codling moth (Cydia pomonella) and the recruitment of predatory arthropods (spiders, earwigs) in a factorial field experiment. Apple trees were intercropped with basil (Ocimum basilicum), French marigolds (Tagetes patula), or ryegrass (Lolium perenne). The association between apple trees and O. basilicum increases codling moth parasitism, but does not affect arthropod predator abundances. Furthermore, we find a general negative effect of T. patula on arthropod diversities and abundances, including the pest and its natural enemies. Finally, changes in the parasitism rate and arthropod community structure due to the aromatic plants do not reduce codling moth density or associated apple damage. Further experiments are needed to determine the mechanisms involved in aromatic plant effects on pest repellence and on natural enemy recruitment (volatile organic compound composition, floral resource supply, or pest density dependence).

Native generalist natural enemies and an introduced specialist parasitoid together control an invasive forest insect.

Specialized natural enemies have long been used to implement the biological control of invasive insects. Although research tracking populations following biological control introductions has traditionally focused on the impact of the introduced agent, recent studies and reviews have reflected an appreciation of the complex interactions of the introduced specialist agents with native generalist natural enemies. These interactions can be neutral, antagonistic, or complementary. Here we studied the invasive defoliator winter moth (Operophtera brumata) in the Northeast USA to investigate the role of native, generalist pupal predators along with the introduced, host-specific parasitoid Cyzenis albicans. Prior research in Canada has shown that predation of winter moth pupae from native generalists increased after C. albicans was established as a biological control agent. To explain this phenomenon, the following hypotheses were suggested: (H1 ) parasitoids suppress the winter moth population to a density that can be maintained by generalist predators, (H2 ) unparasitized pupae are preferred by predators and therefore experience higher mortality rates, or (H3 ) C. albicans sustains higher predator populations throughout the year more effectively than winter moth alone. We tested these hypotheses by deploying winter moth pupae over 6 years spanning 2005 to 2017 and by modeling pupal predation rates as a function of winter moth density and C. albicans establishment. We also compared predation rates of unparasitized and parasitized pupae and considered additional mortality by a native pupal parasitoid. We found support for the first hypothesis; we detected both temporal and spatial density dependence, but only in the latter years of the study when winter moth densities were low. We found no evidence for the latter two hypotheses. Our findings suggest that pupal predators have a regulatory effect on winter moth populations only after populations have been reduced, presumably by the introduction of the host-specific parasitoid C. albicans.

Life table simulations of a univoltine codling moth, Cydia pomonella, population 3. Impact of immigration on the effectiveness of mating disruption

ABSTRACT The potential for immigration of female codling moth, Cydia pomonella (L.), to affect the efficacy of control by mating disruption was simulated by incorporating different rates of disruption and immigration into previously published life tables for a univoltine codling moth population on unsprayed apple trees in Nelson, New Zealand. Eight-year simulations were conducted using an initial codling moth density of 1.22 adults per tree at 330 trees per ha, as in the original life tables. Life table simulations without mating disruption served as controls for comparison with simulations that included various rates of disruption, and then various rates of immigration by virgin or mated female moths into trees subjected to 85% or 98% disruption. Model outputs were evaluated principally in relation to a nominal low export tolerance of fresh codling moth damage on harvested fruit of one per million. The simulations suggested that 85% disruption reduced the codling moth population too slowly for such export production, and that this rate of disruption was highly susceptible to immigration of virgin or mated female moths. Mating disruption of 98% provided rapid reduction of codling moth to extremely low population density, even in the presence of virgin female immigration up to ∼30 females per ha. However, although this efficacy should allow export by reducing simulated damage to less than one per million fruit, this was undermined by immigration of mated females as low as ∼0.7 per ha, or one per ∼3500 trees, in modern high-density orchards at 2400 trees per ha.

The Impact of Microbial and Botanical Insecticides on Grape Berry Moths and Their Effects on Secondary Pests and Beneficials

According to the European Directive 2009/128/EC and the subsequent provisions activated in member states, conventional pesticides should be progressively replaced by “non-chemical tools and/or measures”. The identification of reliable alternatives to pesticides is crucial to achieve this objective. A European project (PURE) was funded to investigate this topic with reference to annual and perennial crops. In this framework, a number of natural insecticides, in particular microbial and botanical ones (Bacillus thuringiensis ssp. kurstaki, Beauveria bassiana, azadirachtin, pyrethrins and spinosad) were selected to test their effectiveness against grape berry moths, the key pests in most European vineyards. Trials were conducted in 2011 and 2012 in two experimental vineyards located in Italy (Tuscany and Veneto regions), following a randomized block design. Additional investigations were carried out in the Veneto region during 2013. Trial results stressed the high performance of spinosad and B. thuringiensis in controlling berry moth densities and the related damage. The use of B. bassiana mixed with B. thuringiensis did not significantly improve the impact of B. thuringiensis alone. Azadirachtin, and especially pyrethrins, proved to be less effective on berry moths than previous insecticides. The use of selected insecticides caused side-effects on a number of secondary pests, in particular leafhoppers. In 2011, densities of Empoasca vitis were higher in spinosad-treated plots probably because of a reduced egg parasitization rate. One year later, the population density of Zygina rhamni was higher in the plots treated with spinosad or pyrethrins. This trend was confirmed on spinosad-treated plots in the last experimental year. At the same time, spinosad and pyrethrins significantly reduced the predatory mite populations compared to other treatments. The use of these insecticides in viticulture is discussed in the framework of organic viticulture and Integrated Pest Management (IPM).

Spatial structure of natural boxwood and the invasive box tree moth can promote coexistence

In the absence of top-down and bottom-up controls, herbivores eventually drive themselves to extinction by exhausting their host plants. Poorly mobile herbivores may experiment only local disappearance, because they can recolonize intact plant patches elsewhere, leaving time to previously over-exploited patches to regrow. However most herbivores such as winged insects are highly mobile, which may prevent the formation of spatial heterogeneity. We test if long-distance dispersal can preclude coexistence using the invasion of box tree moth (Cydalima perspectalis) in Europe as a model system. We build a lattice model and estimate the parameters with a combination of field measurements, experimental data and literature sources. Space corresponds either to a realistic boxwood landscape in the Alps, or to theoretical landscapes of various sizes. We find that both species persist under a large range of realistic parameter values, despite a severe reduction in boxwood biomass, with an alternation of outbreaks and near-to-extinction moth densities. Large landscapes are necessary for coexistence, allowing the formation of spatial structure. Slow plant regrowth combined with long-distance dispersal could drive moths to extinction, because of resources depletion at the global scale even without a complete synchronization of the local dynamics. The spatial dynamics leads to formation of small plant patches evenly distributed in the landscape, because of a combination of local plant dispersal and global indirect competition between plants through their positive effect on moth population size. Coexistence is favoured by such heterogeneous landscapes, because empty patches increase moth mortality during dispersal: the system thus creates its own stability conditions.

Annual flower strips and honeybee hive supplementation differently affect arthropod guilds and ecosystem services in a mass-flowering crop

Intensively managed agricultural landscapes have degraded the provisioning of diverse and continuous forage and shelter habitats for arthropods and weakened the delivery of ecosystem services such as insect crop pollination and biological pest control. In response, farmers are incentivised to sow flower strips along field margins to counteract resource bottlenecks. Yet, it is poorly understood how effective this diversification practice is when combined with the supplementation of honeybee (Apis mellifera L.) hives, which is commonly used to boost insect pollination in flowering crops. Honeybees share floral resources with wild pollinators and natural enemies of pests, which could lead to competition for food resources. We sampled pollinators, natural enemies and their pests as well as estimated the benefit of insect pollination in 17 organic faba bean (Vicia faba minor L.) fields in southern Sweden either with or without sown annual flower strips and with or without added honeybee hives. In fields with flower strips, bumblebee (Bombus spp.) densities were redistributed from field edges to interiors but without affecting their overall densities. Flower strips enhanced silver Y moth (Autographa gamma L.) densities and carabid beetle Shannon diversity along the field edge, and overall spider activity density. The supplementation of honeybee hives enhanced honeybee densities, overall ladybird beetle densities, black bean aphid (Aphis fabae Scop.) densities along field edges, but deterred silver Y moths and pushed bumblebees towards the field interior. Bean mass per plant was higher in insect pollinated plants compared with bagged, self-pollinated plants. This insect pollination benefit was independent of honeybee hive supplementation and the flower strip treatment suggesting that faba bean fields were not deficient in pollinator visits. We conclude that flower strips did not provide sufficient floral resources to increase overall wild pollinator densities in faba bean fields. Yet, annual flower strips attracted and facilitated ground-dwelling predators, especially spiders, to faba bean fields, likely by providing beneficial shelter habitats. It is worth noting that 2018, in which we collected our data, was characterised by late frosts in spring followed by an unusually hot and dry summer. While these unforeseen weather conditions together with a relatively small sample size might limit the generalisation of our results, we argue that conducting experiments under such conditions provide insights into the effectiveness of agri-environmental schemes under climate change, especially considering that such weather conditions are becoming increasingly more frequent.

Life table simulations of a univoltine codling moth, Cydia pomonella, population 1. Biological control with Mastrus ridens

ABSTRACT The potential for the newly established ichneumonid Mastrus ridens (Horstmann) to provide biological control of codling moth, Cydia pomonella (L.), was simulated by incorporating different rates of parasitism into previously published life tables for a univoltine codling moth population on unsprayed apple trees in Nelson, New Zealand. Simulations over eight years were conducted using high and low initial codling moth densities, as occur respectively on neglected apple trees and commercially managed orchards. Life table simulations without M. ridens served as control treatments for comparison with simulations that included various rates of parasitism by each of the estimated three annual generations of the parasitoid. Based on the percentage parasitism recorded in New Zealand and the international literature, M. ridens is projected by the models to provide a valuable reduction of codling moth populations on neglected host trees in Nelson and thereby reduce the numbers of immigrant adult moths invading commercial apple orchards. In contrast, the codling moth is maintained at such extremely low densities within commercial apple orchards growing fruit for export that M. ridens is projected to make only a small contribution to parasitism within the orchard. These simulation results confirm the validity of the rationale for the introduction of M. ridens to New Zealand, which aimed to reduce the numbers of immigrant codling moths arriving in orchards from highly infested and neglected host trees in the wider environment.

Ecology of outbreak populations of the western spruce budworm

AbstractWe sampled outbreak populations of western spruce budworm, Choristoneura occidentalis (Lepidoptera: Tortricidae), between 1997 and 2016 in Douglas‐fir forests in the interior of British Columbia, Canada. Annual rates of change in population densities were correlated with generation survival, modulated by egg recruitment via dispersal of moths. Most temporal variation in generation survival was the result of variation in survival of small, non‐feeding larval stages. Survival rates of feeding larval and pupal stages determined the magnitude of generation survival but contributed little to temporal trend. Survival of small larvae was the product of density‐related losses of larvae dispersing to and from hibernation sites and weather‐related stress caused by warm temperatures in late summer and early spring. Overwinter survival improved in cooler years and at higher elevations. Survival of feeding larvae and pupae was associated with mortality by natural enemies, in particular a few species of dominant, ubiquitous endoparasitoids, and an episodic, virulent baculovirus. Recruitment of eggs indicated emigration of gravid moths independent of defoliation but proportional to density of local moths. During periods of increasing and decreasing population densities over a large outbreak area, a marked differential in adult densities among locations resulted in greater than expected per‐capita egg recruitment to areas of relatively low density and vice versa, indicative of net exchange of gravid moths from high‐ to low‐density populations. The result was homogenization of egg densities among locations, apparent synchrony of the outbreak at the large scale, and extended duration of the outbreak at some locations, despite declining generation survival. These results are compared with field studies of the closely related spruce budworm, Choristoneura fumiferana. We suggest our interpretation applies more generally and outbreaks of conifer‐feeding budworms are maintained for several years by compensatory survival of sequential life‐history stages and spatio‐temporal smoothing of densities via dispersal of gravid moths. Parasitoids and pathogens can cause sudden declines in densities, but populations inevitably wane as a result of cumulative degradation of their resource. The interaction and temporal sequence of bottom‐up and top‐down factors explain the similarities and differences in outbreak characteristics within‐ and among‐budworm species.

Comparison of Sex Pheromone and Kairomone-Enhanced Pheromone Lures for Monitoring Oriental Fruit Moth (Lepidoptera: Tortricidae) in Mating Disruption and Non-Disruption Tree Fruit Orchards.

Oriental fruit moth, Grapholita molesta (Busck), populations were monitored using standard sex pheromone lures (OFM L2) and kairomone-enhanced lures to aid the interpretation of trap captures with enhanced relative to conventional lures. Initially, comparison of 10 different lures showed that a10X load of OFM pheromone, codlemone, terpinyl acetate, and acetic acid were key components of the most attractive lures (TRE11034 and 1123). Subsequent trapping studies in mating disruption and non-disrupted orchards in the United States and Spain compared trap captures with TRE1123 and OFM L2 lures. Compared to the OFM L2 lure, the TRE1123 lure captured more moths in mating disruption and non-disrupted orchards, caught female moths, improved the precision of mean population estimates, and led to greater resolution of generational flights. Suppression of trap captures in mating disruption versus non-disrupted orchards was similar with both lures. There were significant linear correlations between weekly trap captures with the two lures in the majority of mating disruption and non-disrupted orchards across locations and years. Furthermore, regression of the slopes of trap capture regressions (i.e., attractiveness of enhanced lures relative to sex pheromone lures alone) versus moth density (as measured by mean cumulative moth capture with TRE1123 and OFM L2 lures) exhibited a significant positive relationship in non-disrupted orchards, indicating enhanced lures were relatively more attractive under high population densities. This relationship was not significant in mating disruption orchards, likely due to the density independent, non-competitive mechanism of mating disruption for oriental fruit moth when using high-dose reservoir dispensers.

Successful biological control of winter moth, Operophtera brumata, in the northeastern United States.

Winter moth, Operophtera brumata, native to Europe, invaded the northeastern United States in the late 1990s, where it caused widespread defoliation of forests and shade trees ranging from 2,266 to 36,360ha/yr between 2003 and 2015 in Massachusetts. In 2005, we initiated a biological control effort based on the specialist tachinid parasitoid Cyzenis albicans, which had previously been introduced along with the generalist ichneumonid parasitoid Agrypon flaveolatum to control winter moth in Nova Scotia in the 1950s and British Columbia in the 1970s. Due to concerns of possible non-target impacts by A.flaveolatum, we focused entirely on the specialist C.albicans. Each year for 14yr, we collected several thousand individuals of C.albicans from British Columbia and released them in widely spaced sites in the northeastern United States. As of 2020, we had established C.albicans at 41 of 44 sites from coastal Maine to southeastern Connecticut. By 2016, winter moth densities (pupae/m2 ) had declined from 100-500 to 0-10pupae/m2 at six release sites at least 10km apart and this was coincident with the onset of 10-40% parasitism. At one site in Wellesley, Massachusetts, the decline occurred in 2012 and winter moth densities have remained low for seven subsequent years. Defoliation in Massachusetts has been reduced to undetectable levels by aerial survey since 2016. DNA sequencing of the barcoding region of the mitochondrial gene CO1 confirmed that all C.albicans reared from winter moth matched the C.albicans collected from Vancouver Island and were distinct from parasitic flies (presumably a native species) reared from a native congener of winter moth, Bruce spanworm (O.bruceata). Successful establishment of C.albicans on winter moth represents a rare, if not the only, example of the biological control of a major forest defoliator that attacks a wide range of tree species anywhere in the world by the establishment of a single specialist natural enemy.

Siland a R package for estimating the spatial influence of landscape

The spatial distributions of populations are both influenced by local variables and by characteristics of surrounding landscapes. Understanding how landscape features spatially structure the frequency of a trait in a population, the abundance of a species or the species’ richness remains difficult specially because the spatial scale effects of the landscape variables are unknown. Various methods have been proposed but their results are not easily comparable. Here, we introduce “siland”, a general method for analyzing the effect of landscape features. Based on a sequential procedure of maximum likelihood estimation, it simultaneously estimates the spatial scales and intensities of landscape variable effects. It does not require any information about the scale of effect. It integrates two landscape effects models: one is based on focal sample site (Bsiland, b for buffer) and one is distance weighted using Spatial Influence Function (Fsiland, f for function). We implemented “siland” in the adaptable and user-friendly R eponym package. It performs landscape analysis on georeferenced point observations (described in a Geographic Information System shapefile format) and allows for effects tests, effects maps and models comparison. We illustrated its use on a real dataset by the study of a crop pest (codling moth densities).

Impact of Diamondback Moth Density and Infestation Timing on Broccoli Yield.

The diamondback moth (DBM), Plutella xylostella (L.) (Lep.: Plutellidae), is an important pest of broccoli (Brassica oleracea L. var. italica Plenck). Few studies have focused on the real DBM impact on broccoli yield. We performed greenhouse studies to assess the effect of DBM densities and infestation timing (at pre-heading, heading, or during the entire cycle) on broccoli head weight. Polynomial trend analysis revealed a downward linear response of head weight to DBM densities, indicating that broccoli is susceptible to DBM attack. As for the infestation timing, infestations during the pre-heading stage significantly impacted head weight, whereas the same did not occur for infestations during the heading stage. DBM density did not affect plant height or total leaves but was upward-related to plant defoliation, and head weight correlated negatively with plant defoliation. These findings indicate that pre-heading is the determining stage for head weight loss of plants under DBM attack. In order to prevent quantitative losses, efforts for DBM management should be focused on this particular stage.

Relative impacts of gypsy moth outbreaks and insecticide treatments on forest resources and ecosystems: An experimental approach

Abstract1. Gypsy moth outbreaks cause severe defoliation in Holarctic forests, both in North America where it is invasive, and in its native range in Eurasia. Defoliation can hamper timber production and impact ecological communities and processes. Aerial insecticide applications are regularly performed in outbreak areas to mitigate economic losses. These operations can be financially costly and harmful to non‐target species and may disrupt species interaction networks. However, replicated studies of the relative impacts of gypsy moth outbreaks and insecticide application on forest growth and animal communities are rare and have yet to be carried out in the species' indigenous range.2. Here, we review the pathways in which gypsy moth outbreaks and the chemical control of these outbreaks affect forest ecosystems. We then present an experimental design established in South Central Germany in early 2019, aiming to study the ecological and economic consequences of gypsy moth eruptions and insecticide application in oak forests. The study's full factorial design comprises forest stands at high and low defoliation risk, either treated with tebufenozide or left unsprayed, within 12 experimental blocks. Measurements of forest growth and structure, tree mortality, gypsy moth density, and composition of lepidopteran, bird, bat, ground beetle, and canopy arthropod communities will be conducted for several years.3. One‐year intensive monitoring of gypsy moth populations and damage across the selected sites showed substantial differences in population density between plots at high and low defoliation risk and high efficacy of tebufenozide in suppressing gypsy moth populations in treated plots. In the first year of the experiment, gypsy moth density and defoliation in predicted outbreak plots differed strongly, confirming the importance of using many replicates and blocking to control spatial heterogeneity. The experiment will be running continuously during the coming years to produce short‐ and medium‐term economic and ecological data to improve our understanding and management of gypsy moth outbreaks.

Insect Herbivory Strongly Modifies Mountain Birch Volatile Emissions.

Insect herbivory is known to augment emissions of biogenic volatile organic compounds (BVOCs). Yet few studies have quantified BVOC responses to insect herbivory in natural populations in pan-Arctic regions. Here, we assess how quantitative and qualitative BVOC emissions change with increasing herbivore feeding intensity in the Subarctic mountain birch (Betula pubescens var pumila (L.)) forest. We conducted three field experiments in which we manipulated the larval density of geometrid moths (Operophtera brumata and Epirrita autumnata), on branches of mountain birch and measured BVOC emissions using the branch enclosure method and gas chromatography-mass spectrometry. Our study showed that herbivory significantly increased BVOC emissions from the branches damaged by larvae. BVOC emissions increased due to insect herbivory at relatively low larvae densities, causing up to 10% of leaf area loss. Insect herbivory also changed the blend composition of BVOCs, with damaged plants producing less intercorrelated BVOC blends than undamaged ones. Our results provide a quantitative understanding of the relationship between the severity of insect herbivore damage and emissions of BVOCs at larvae densities corresponding to background herbivory levels in the Subarctic mountain birch. The results have important and practical implications for modeling induced and constitutive BVOC emissions and their feedbacks to atmospheric chemistry.

Invasions of insect pests and fungal pathogens of woody plants into the northwestern part of European Russia

«Вестник Санкт-Петербургского университета. Науки о Земле» — научно-теоретический рецензируемый журнал, обобщающий результаты исследований в области геологии, гидрогеологии и геохимии, петрологии и экологии, ландшафтного планирования и геоморфологии, экономической и социальной географии.

Influence of Bacillus thuringiensis application timing on population dynamics of gypsy moth in Mediterranean cork oak forests.

The gypsy moth, Lymantria dispar, is one of the main pests of oak forests worldwide and causes extensive defoliation during its periodic outbreaks. In the Mediterranean region, control of gypsy moth populations in cork oak forests is based on application of Bacillus thuringiensis serovar kurstaki (Btk) formulations. This research investigated the effects of Btk applications carried out in two different population development phases on gypsy moth population dynamics. With this aim, temporal and spatial fluctuation patterns of L. dispar egg density were monitored in cork oak forests treated with Btk applications from 2004 to 2009 in Sardinia (Italy). Applications undertaken during the progradation and culmination phases protected the oak canopies equally in the year of application, leading to a similar decrease in pest population density in the following year. However, the medium-term effectiveness of Btk differed between the two application timings, because only applications in the culmination phase caused a gradual decrease in L. dispar infestations throughout subsequent years. By contrast, when the application was undertaken during the progradation phase, population density increased again after 2-3 years. Moreover, Btk applications in the culmination phase reduced significantly the number of years in which gypsy moth density was damaging compared with those done in progradation. Our results indicate that Btk applications during the culmination phase were more effective than those in the progradation period, because application in the latter case did not suppress the population, but only postponed the outbreak peak by 2-3 years. © 2019 Society of Chemical Industry.

An Analysis of the Fruit-Sucking and Fruit-Piercing Moth Complex in Citrus Orchards in South Africa

Fruit-piercing moths are a sporadic pest of citrus, especially in the Eastern Cape Province of South Africa, where the adults can cause significant damage in outbreak years. However, growers confuse fruit-piercing moths with fruit-sucking moths that do not cause primary damage. In this study we trapped these moths during the 2013–2015 growing seasons. A large number of diverse fruit-feeding moths were collected through weekly sampling in citrus orchards in the Eastern Cape and northern Limpopo provinces. Twenty-three species of fruit-feeding moth were trapped. However, only two were fruit-piercing species, capable of causing primary damage, namely Serrodes partita (Fabricius) (Erebidae) and Eudocima divitiosa (Walker) (Erebidae). Surprisingly S. partita, which has been reported as the main fruit-piercing moth pest of citrus in South Africa, comprised only 6.9 % of trap catches. The categorisation of moths as fruit-piercing or fruit-sucking (causing secondary damage) was confirmed by examining the morphological structures (tearing hooks and erectile barbs) of these moths’ proboscides. This study has shown that in non-outbreak seasons, S. partita comprised only a small percentage of fruit-feeding moths in citrus orchards. However, growers may misidentify the harmless fruit-sucking species as fruit-piercing species, and thus overestimate the density of fruit-piercing moths.

Variation du taux d’infestation par Thaumetopoea pityocampa du pin d’Alep : effet sur les paramètres dendrométriques dans les forêts de la région de Djelfa (Atlas saharien, Algérie)

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±2.61nests/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.

Relationship between efficacy of mating disruption and gypsy moth density

ABSTRACTMating disruption tactics involve the deployment of pheromones to interfere with mate finding behaviors in insect populations. This management strategy is the dominant one used against expanding gypsy moth populations in the United States, and historically it has been assumed to be most effective against low-density populations. Operationally, mating disruption is used in areas where the season-long trap catch is <30 males/trap, however the maximum population density at which mating disruption is effective remains unknown. We analysed historical gypsy moth mating disruption treatment data from 2000 to 2010, and used this information to guide the mating disruption field studies conducted from 2012 to 2015 against artificially-created populations of various densities, from 0 to 116 males/trap/day. We observed that mating disruption tactics at a dose of 15 g AI/ha were effective against gypsy moth populations with a season-long trap catch of at least 115 males/trap. This research highlights the utility of mating disruption in higher gypsy moth densities than what is currently recommended in management programs.

Identification and impact of hyperparasitoids and predators affecting Cyzenis albicans (Tachinidae), a recently introduced biological control agent of winter moth (Operophtera brumata L.) in the northeastern U.S.A.

The success or failure of an introduced biological control agent may depend on its rate of mortality from disease, predation, and hyperparasitism. Cyzenis albicans Fallén (Diptera: Tachinidae) was introduced to the northeastern U.S. as a biocontrol agent of the invasive species winter moth, Operophtera brumata L. (Lepidoptera: Geometridae). This study aimed to determine the rates of mortality from predation by generalist ground predators and hyperparasitism of C. albicans puparia, identify any hyperparasitoids, and assess the impact of predation and hyperparasitism on the potential success of C. albicans in controlling the winter moth. Mortality of C. albicans puparia was primarily due to predation, but there was also hyperparasitism. Predation and parasitism of C. albicans puparia were consistently high across the six study sites and two years of study, but somewhat lower than was reported from British Columbia, where successful establishment of C. albicans in the 1970s was followed by a decrease in winter moth densities. In this study, three genera of ichneumonid hyperparasitoids were detected and identified using a combination of morphological and molecular approaches: Phygadeuon (1 species), Pimpla (2 species), and Gelis (2 species), all of which contain species with broad host ranges and were likely acting as facultative hyperparsitoids. We conclude that while total mortality of C. albicans puparia is high, it is unlikely to have a significant effect on biological control of winter moth in this system, although it may explain why C. albicans has been slow to establish in this region. Our study emphasizes the importance of assessing the mortality of introduced biological control agents caused by native predators and hyperparasitoids.