Destruction Of Eggs Research Articles

Isolated and Associated Use of the Nematophagous Fungi Pochonia chlamydosporia and Duddingtonia flagrans to Control Taenia saginata Eggs

The aim of this study was to evaluate the isolated and associated use of the nematophagous fungi Pochonia chlamydosporia (isolate VC4) as an ovicide and Duddingtonia flagrans (isolate AC001) as a predator in the control of Taenia saginata eggs. Viable T. saginata eggs were obtained by dissecting mature proglottids from a specimen. For the experimental assay, four groups were formed in microtubes, as follows: (G1—T. saginata eggs/control); (G2—100 T. saginata eggs + VC4); (G3—100 T. saginata eggs + AC001); (G4—100 T. saginata eggs + VC4 + AC001). All the groups were stored in a B.O.D. incubation chamber at a temperature of 27 °C for 15 days and then the contents of the microtubes were analyzed using an optical microscope with a 40x objective. At the end of the assay the treated groups (G2 to G4) showed ovicidal activity (destruction of eggs) compared to the control group (G1). The highest ovicidal percentage was observed in group G2 (eggs + VC4), with 43.3%. In groups G3 and G4 (combination of fungal isolates), the ovicidal percentages were 25.7% and 25.6%, respectively. The results of this study shed light on a new possibility for the combined use of different species of nematophagous fungi, which could be used in the future for environmental biological control of T. saginata eggs.

Ovicidal Effect of Disinvasive Substances on the Eggs of Nematodiroses Causative Agents

The article deals with the study of the disinvasive effects of various percentage solutions of chemical substances on the eggs of nematodes in cattle under in vitro conditions. Based on the results obtained during the experiments, carried out under in vitro conditions it was found that 3.0% and 5.0% solutions of the deltatrine preparation destroy nematode eggs by 100%, and 3.0% and 5.0% solutions of the citrine preparation by 72.2-80.0%. In a concrete test object, with a 3-hour exposure, helminth eggs (1200 eggs) were destroyed by 100% from the impact of a 3.0% deltathrine preparation, by 63.6% from the impact of a 3.0% citrine solution (800 eggs), and by 58.3% from the impact of 4.0% phenol (700 eggs). Also on a wooden test object, with a 3-hour exposure, helminth eggs (1200 eggs) were destroyed by 100% from the impact of 3.0% deltathrine preparation, by 58.3% from the impact of a 3.0% citrine (700 eggs), and by 63.6% from the impact of 4.0% phenol solutions (600 eggs). For control purposes, ordinary water was added to the helminth eggs, and no decrease in their number was detected. At the next stage, having isolated them from other areas, 4 plots of 1 m2 each were allocated. For the purpose of the experiment, 93.3% of eggs died on a plot sprayed with a 3.0% solution of the deltatrine preparation, 66.7% of eggs died on a plot sprayed with a 3.0% solution of the citrine preparation, and 60.0% of eggs died on a plot sprayed with a 4.0% solution of phenol. Since under in vitro conditions, due to the direct effect of disinvasive substances on Nematodirus eggs, the eggs die quickly, however, in test objects, due to the fact that the eggs are mixed with feces on an area of 1 m2, the duration of action of chemicals increases, and the percentage of destruction of helminth eggs decreases.

Mathematical modeling of helminth eggs inactivation in pig (Sus domestica) manure from a backyard farm

Pathogenic organisms in pig manure can cause serious environmental and health problems. Pigs are susceptible to infection by microorganisms such as fecal coliforms, Salmonella spp., protozoa, and helminths. The latter are found in tropical and subtropical zones, where they are a source of health risk associated with poor sanitation due to contaminated water for agricultural irrigation and the inadequate final disposal of excrements on the ground. For this reason, it is necessary to treat the waste so that it complies with the maximum permissible limits established in the official regulations and is disposed of correctly. In this work, the kinetic parameters of the alkaline inactivation process were determined with different CaO concentrations (10, 15, and 20% m/m) and different time periods (0, 30, 60, 90, and 120 min). In addition, the evaluation of the product DT (ammonia dose and temperature) was carried out for the described process, for which the increase in pH and temperature after the addition of alkaline matter was studied for the inactivation of total helminth eggs in a system open. The mathematical modeling was carried out with the Hom model modified for chemical treatments. The results showed that the process used had an efficiency of 94.7% in the destruction of whole helminth eggs, of which 5.8% was carried out thanks to the ammonia dose and the resulting temperature (9,963 mg/L °C). Although the DT factor was not the leading cause of the helminth eggs inactivation it contributed favorably to the process in addition to the applied CaO dose (20%).

Efficacy of a Fungal Formulation with the Nematophagous Fungus Pochonia chlamydosporia in the Biological Control of Bovine Nematodiosis.

In the control of bovine worms, biological control by nematophagous fungi stands out, especially Pochoniachlamydosporia which causes the destruction of helminth eggs. This study aims to test the effectiveness of a formulation containing the nematophagous fungus Pochonia chlamydosporia isolated for the biological control of bovine nematodiosis. Twelve cattle were divided into two groups: control group (GC) and the group that received the formulation (GT). Feces and pasture samples were collected for the research of gastrointestinal nematodes. Lung worms and trematodes were investigated. The animals were weighed monthly. The averages of temperature and rainfall were recorded. The supply of the fungus Pochonia chlamydosporia was not effective in reducing the eggs per gram of feces of gastrointestinal nematodes (EPG) of the animals, not differing statistically (p > 0.05) between the groups. The mean values of larvae recovered in the pasture did not differ significantly (p > 0.05). The genus Haemonchus sp. was the most prevalent. There was no correlation between the number of larvae with temperature and rainfall (p > 0.05). There was a statistically significant difference (p < 0.05) in the penultimate weighing of the experiment. The formulation containing Pochonia chlamydosporia was not efficient in the biological control of bovine gastrointestinal nematodes.

Citizen science survey of non-native Rose-ringed Parakeets Psittacula krameri in the Durban metropole, KwaZulu-Natal, South Africa

The Rose-ringed Parakeet Psittacula krameri (Scopoli, 1769) has become invasive in several countries, including South Africa, mainly through the pet trade releases and escapees. We conducted an online questionnaire survey targeting the residents in Durban, eThekwini Municipality, KwaZulu-Natal, South Africa. We aimed to determine the distribution, habitat and diet of the Rose-ringed Parakeet. We also determined if the public perceived parakeets as pests and if control measures were supported. We found that many parakeet sightings were reported in Durban North, primarily in and around shopping centres. Approximately 64.5% of respondents provided feeding stations for parakeets, with most providing seeds and grains. A total of 173 (55.4%) respondents considered parakeets as a pest. Rose-ringed parakeets were reported to chase nine bird species, of which seven were native and two non-natives. Most respondents stated that parakeets should not be controlled. However, most of those who supported their control suggested shooting and destruction of eggs. We concluded that the distribution of parakeets is likely expanding and associated with anthropogenic activities in this urban landscape. However, public perceptions may make invasive Rose-ringed Parakeet management difficult.

How to build a puncture- and breakage-resistant eggshell? Mechanical and structural analyses of avian brood parasites and their hosts.

Evolved eggshell strength is greater in several lineages of obligate avian brood parasites (birds that lay their eggs in other species' nests) than in their hosts. Greater strength is typically indirectly implied by eggshell thickness comparisons between parasites and hosts. Nevertheless, there is strong evidence that the eggshell structural organization differentially influences its mechanical properties. Using instrumental puncture tests and SEM/EBSD and XRD techniques, we studied the most relevant eggshell mechanical, textural, ultrastructural and microstructural features between several host species and their parasitic cowbirds (Molothrus spp.). These parasitic species display different egg-destructive behaviors, reducing host reproductive fitness, including the more frequently host-egg puncturing M. rufoaxillaris and M. bonariensis, and the host egg-removing M. ater. The results, analyzed using a phylogenetic comparative approach, showed interspecific patterns in the mechanical and structural features. Overall, the eggshells of the two egg-puncturing parasites (but not of M. ater) were stronger, stiffer and required greater stress to produce a fracture than the respective hosts' eggs. These features were affected by eggshell microstructure and ultrastructure, related to the increase in the intercrystalline boundary network acting in cooperation with the increase in palisade layer thickness. Both structural features generate more options and greater lengths of intercrystalline paths, increasing the energy consumed in crack or fissure propagation. The reported patterns of all these diverse eggshell features support a new set of interpretations, confirming several hypotheses regarding the impact of the two reproductive strategies (parasitic versus parental) and parasitic egg destruction behaviors (more versus less frequently puncturing).

Localized control of opportunistic, overabundant species in protected areas: a retrospective modelling approach encompassing future scenarios

AbstractThe yellow‐legged gull (Larus michahellis) is an opportunistic seabird species, whose worldwide demographic increase in the second half of the 20th century was associated to anthropogenic activities, such as the proliferation of open‐air dumps in urban coastal areas. In the small Berlengas archipelago (Peniche, Portugal), the species breeding population reached about 44,000 individuals in 1994, representing a severe ecological pressure in this Biosphere Reserve. In an attempt to control this overpopulation, management actions were implemented in the area, namely, the culling of breeding adults and later egg destruction campaigns. Although the population has been decreasing in recent years, it is unknown how much of this reduction is due to management actions since the closure of open‐air dumps in Portugal might also have influenced the yellow‐legged gull population trends. We developed a dynamic model to test pertinent explanatory hypotheses for this problem, taking into account retrospective population trends under alternative contexts of food availability and management actions. The model was also used to predict population growth patterns under future management scenarios. Our results show that, despite contributing to reduce birds local abundance, egg destruction alone would not be able to trigger the population decrease observed in the last two decades. Instead, the permanent closure of open‐air dumps in 2001 was likely the major driver for the species local decline. In the current context of restricted anthropogenic food sources, our study also suggests that the tendency of the population is to naturally decline. Thus, continuing fertility control campaigns can compromise the future viability of the yellow‐legged gull population on the Berlengas Natural Reserve. Our study highlights the interplay between model‐based research and ecological monitoring to test the effectiveness of ongoing management programmes and to anticipate the ecological consequences of future control of native species.

NESTING BEHAVIOUR AND CURRENT THREATS TO THE INDIAN SARUS CRANE AROUND ALWARA LAKE OF DISTRICT KAUSHAMBI (U.P.), INDIA

The Indian Sarus crane (Grus antigone antigone) is a monogamous, graceful water bird, well known as an eternal symbol of unconditional love, devotion and good fortune with a high degree of marital fidelity. Its occurrence represents a healthy wetland ecosystem. A systematic study was conducted from June 2019 to May 2020 in the villages adjoining the Alwara Lake of district Kaushambi (Uttar Pradesh), India to explore the nesting behavior and current threats to the Sarus crane. During the study, a total number of 43 nests were encountered in the study area. The nests were seen on large wetlands, uplands, paddy fields, scattered irrigation ditches, adjoining areas of Lake etc. around the human settlements. These birds preferred to use local flora in constructing the nests, many of them with medicinal values. The main threats include the egg destruction by predator animals and indirect anthropogenic activities; however farmers tolerate the cranes nesting in their productive sites, despite the considerable crop damage.

Inter‐group conflict in a cooperatively breeding bird: New insights into “home field advantage”

AbstractConflicts between groups of animals have individual‐level fitness consequences that can influence the evolution of social behaviour. In the cooperatively breeding greater ani (Crotophaga major), groups occasionally destroy the eggs of their neighbours, causing the attacked group to abandon their nest. Prior research suggested that such conflicts occur when two groups build nests in close proximity, and that established groups tend to evict newcomers. However, inter‐group conflict had never been directly observed. Here, we report the first photographic evidence of egg destruction by greater anis. Twelve artificial nests containing clay eggs were placed in the field with the intent of attracting nest predators. Camera footage revealed that although only two nests were discovered by heterospecific predators (white‐faced capuchins, Cebus capucinus), five nests were visited by resident anis, who in three cases damaged the clay eggs by grasping them with their bills and ejecting them from the nest cup. Nests were discovered between 2 and 96 hr after being placed in the field (mean = 34 hr) and were visited up to 18 times by up to 4 individuals simultaneously. The distance between artificial nests and the nearest known ani territory ranged from 0.13 to 0.28 km (mean = 0.2 km). Resident groups did not subsequently breed at the nest sites that they attacked, consistent with the hypothesis that the main benefit of inter‐group conflict is to reduce competition for local resources rather than to usurp nest sites. This accidental experiment reveals that greater anis closely monitor nesting activity near their territories, which may contribute to the strong “home field advantage” that resident groups hold over intruders.

Research Note: Indian poultry industry vis-à-vis coronavirus disease 2019: a situation analysis report

Originating in Wuhan city, Hubei province of China, and rapid spread to multiple countries, severe acute respiratory syndrome coronavirus 2 has emerged as a novel public health emergence. During early February, spread of misinformation and rumors driven by the fear of linking chicken meat and eggs in the transmission of coronavirus disease 2019 (COVID-19) among human population is witnessed in India. This resulted drastic reduction in consumption of poultry products with subsequent fall in demand thereby prices. The COVID-19–driven lockdown during March in the country has further accentuated the crippling poultry industry following the arrest of feed and healthcare essentials and destruction of eggs, chicks, and birds. Here, we have analyzed the impact of COVID-19 on the poultry industry and showed the realistic flow of events that resulted in its economic fallout by disruption of poultry protein chain during pandemic crisis. The projected loss caused because of these events for the Indian poultry industry is around USD 3053 million. The economic impact is not uniform across the country owing to regional differences in consumption pattern and percent non-vegetarians.

Nesting Observations on a South American Subspecies of Least Grebe (Tachybaptus dominicus brachyrhynchus)

Despite a wide distribution over much of the New World, the behavior of the Least Grebe (Tachybaptus dominicus) is still poorly known, and most ecological studies have been performed on Northern Hemisphere subspecies. This note reports two observations during breeding in the South American subspecies T. d. brachyrhynchus. Deliberate egg-covering to hide an active nest from an approaching threat was observed, coupled with elusive “hiding” behavior during an opportunistic breeding attempt in a novel habitat (xeric Chaco). Photographic documentation of egg destruction by a domestic Muscovy Duck (Cairina moschata) at a Least Grebe nest is also reported.

A qualitative study of community perspectives surrounding cleaning practices in the context of Zika prevention in El Salvador: implications for community-based Aedes aegypti control

BackgroundIn El Salvador, Aedes aegypti mosquitoes transmitting Zika and other arboviruses use water storage containers as important oviposition sites. Promotion of water storage container cleaning is a key element of prevention programs. We explored community perceptions surrounding cleaning practices among pregnant women, male partners of pregnant women, and women likely to become pregnant.MethodsResearchers conducted 11 focus groups and 12 in-depth interviews which included individual elicitations of Zika prevention measures practiced in the community. Focus group participants rated 18 images depicting Zika-related behaviors according to effectiveness and feasibility in the community context, discussed influencing determinants, voted on community intentions to perform prevention behaviors, and performed washbasin cleaning simulations. In-depth interviews with male partners of pregnant women used projective techniques with images to explore their perceptions on a subset of Zika prevention behaviors.ResultsGeneral cleaning of the home, to ensure a healthy environment, was a strong community norm. In this context, participants gave water storage container cleaning a high rating, for both its effectiveness and feasibility. Participants were convinced that they cleaned their water storage containers effectively against Zika, but their actual skills were inadequate to destroy Aedes aegypti eggs. A further constraint was the schedule of water availability. Even during pregnancy, male partners rarely cleaned water storage containers because water became available in homes when they were at work. Furthermore, prevailing gender norms did not foster male participation in domestic cleaning activities. Despite these factors, many men were willing to provide substantial support with cleaning when their partners were pregnant, in order to protect their family.ConclusionsBehavior change programs for the prevention of Zika and other arboviruses need to improve community members’ mosquito egg destruction skills rather than perpetuate the promotion of non-specific cleaning in and around the home as effective. Egg elimination must be clearly identified as the objective of water storage container maintenance and programs should highlight the effective techniques to achieve this goal. In addition, programs must build the skills of family members who support pregnant women to maintain the frequency of effective egg destruction in all water storage containers of the home.

Female-Male and Female-Female Social Interactions of Captive Kept Capercaillie (Tetrao Urogallus) and Its Consequences in Planning Breeding Programs.

Simple SummaryThe Capercaillie is one of the most endangered bird species in many European countries. To prevent further population decline, breeding centers where birds are bred and later released into the wild were established. However, in many Capercaillie breeding stations, reproductive success is limited due to low fertility and problems with incubation behavior by females. Reasons for these problems are usually multidimensional, including misunderstanding Capercaillie behavior in the breeding environment. Research was conducted in Capercaillie breeding centers where birds were monitored 24 h/day by cameras. We observed that females preferred to mate with males with a longer tooting activity, but when males became too insistent and started to chase the females, they avoided contact. Even when the density of females was only one bird per 132 m2, nesting site competition occurred. In 67% of the nests, female intruder’s presence could be observed. Interactions between females were mainly antagonistic, and while none of the birds were harmed, this caused egg damage and nest abandonment. Nesting site competition in captive Capercaillie is high and may lead to antagonistic interaction between females, consequently lowering breeding success. Our research showed also that mate preference of males by females could be predicted by observing the male’s tooting activity.Capercaillie behavior, both in the wild and in captivity, is poorly known due to this species’ secretive way of life. Female-male and female–female social organization and interactions are especially poorly documented. The research was conducted in Capercaillie Breeding Center in Wisła Forestry District where a breeding flock is kept throughout the year. Thanks to video monitoring, we were able to observe mate choice, and then later, female–female interactions during laying and incubation period. Male individual variation in tooting latency and duration were recorded. Females’ interest in males was related to males’ tooting activity, but when males became too insistent and started to chase the females, the females avoided contact with them. There was a significant relationship between calendar date and when tooting starts, and between the tooting duration the female spent with a male. Two incidents of female-male aggression caused by competition for food were observed. Female intruder presence and competition for nesting place was observed in 66.67% nests. Most female–female interactions were limited to threat posturing, but fights and attempts to push out the intruder from the nest occurred as well. Such interactions may lead to nest abandonment and egg destruction, lowering the breeding success.

Troglodytes troglodytes – probable destructor of eggs of Cinclus cinclus

Interspecific or intraspecific destruction of eggs by other small bird species (Passeriformes) is a relatively rare behaviour. It is known from studies of several new world species from families Mimidae and Troglodytidae, but it has never been documented in the Eurasian wren (Troglodytes troglodytes). While studying the breeding biology of the white-throated dipper (Cinclus cinclus) in northern part of Central Slovakia, we documented seven events (frequency 1.8%) when Eurasian wren occupied a dipper’s nest during the breeding season. None of these breeding attempts by the dippers was successful. In all cases, the breeding pairs abandoned their nest. Except of these seven cases, we also found an abandoned nest (situated in the nest box under a bridge) with damaged eggs of the white-throated dipper. According to the intact nest bottom, we hypothesise that the nest was not predated. Here we probably describe the first case of egg destruction by the Eurasian wren in Europe.

Egg Destruction by Males in the Western Grebe and Clark’s Grebe

Egg Destruction by Males in the Western Grebe and Clark’s Grebe

VIABILITY OF THE POPULATIONS OF PERDIX PERDIX L. AT MT. FRUŠKA GORA AND SREMSKA RAČA, REPUBLIC OF SERBIA

UDK: 639.124(497.11)&#x0D; Perdix perdix L. (also known as the Grey partridge, English partridge, and Hungarian partridge) populations have been declining for years in natural habitats and areas in which this species of wildlife has been introduced. Hunting grounds at the base of Mt. Fruška Gora and Sremska Rača in the Republic of Serbia provide excellent conditions for its breeding. In addition to the data from hunting records about population quantity of the P. perdix, a direct monitoring allows a relevant inside to its' quantity in hunting associations’ hunting grounds. The decline of population quantity is mostly the result of the use of chemicals for protection of agricultural crops (10%), destruction of nests and bird eggs (12.5%), and the failure to implement failure wildlife-protection measures, by forbidding the hunt of P. perdix (5%) , and the use of poisons on agricultural crops, such as the forbidden poison Furadan (5%). Although no significant results have been obtained on the impact of predators and abandoned animals on the reduction of P. perdix population, there is a justified concern by hunting associations’ in terms of finding ecologically and biologically viable solutions for impact on predators on feathered game, and especially abandoned dogs. The results of the study were obtained by the method of directly determining the number of P. perdix in the crop fields, in the hunting grounds of L.D. "Fazan Mala Remeta", L.D. "Fazan" Jazak, L.D. "Stejanovci" Stejanovci, L.D. "Zec" Vrdnik and L.D. "Srndać" Sremska Rača. The obtained results directly the need to introduce the principle of integral protection of P. perdix, which implies control over the implementation of measures for the protection of agricultural crops and the implementation of P. perdix protection measures during the organization of hunting on other game species in hunting grounds.

Large river habitat complexity and productivity of Puget Sound Chinook salmon.

While numerous studies have shown that floodplain habitat complexity can be important to fish ecology, few quantify how watershed-scale complexity influences productivity. This scale mismatch complicates population conservation and recovery strategies that evaluate recovery at regional or multi-basin scales. We used outputs from a habitat status and trends monitoring program for ten of Puget Sound’s large river systems to examine whether juvenile Chinook salmon productivity relates to watershed-scale habitat complexity. We derived habitat complexity metrics that quantified wood jam densities, side and braid to main channel ratios, and node densities from a remote sensing census of Puget Sound’s large river systems. Principal component analysis revealed that 91% of variance in these metrics could be explained by two principal components. These metrics revealed gradients in habitat complexity across Puget Sound which were sensitive to changes in complexity as a result of restoration actions in one watershed. Mixed effects models revealed that the second principle component term (PC2) describing habitat complexity was positively related to log transformed subyearling Chinook per spawner productivity rates from 6–18 cohorts per watershed. Total subyearling productivity (subyearlings per spawner) and fry productivity (subyearling fry per spawner) rates were best described by models that included a positive effect of habitat complexity (PC2) and negative relationships with log transformed peak flow recurrence interval, suggestive of reduced survival due to egg destruction during floods. Total subyearling productivity (subyearlings per spawner) and parr productivity (subyearling parr per spawner) rates were best described by models that included a positive effect of habitat complexity (PC2) and negative relationships with log transformed spawner density, suggestive of density dependent limits on juvenile rearing habitat. We also found that coefficient of variation for log transformed subyearling productivity and subyearling fry productivity rates declined with increasing habitat complexity, supporting the idea that habitat complexity buffers populations from annual variation in environmental conditions. Therefore, we conclude that our watershed-scale census-based approach provided habitat complexity metrics that explained some of the variability in productivity of subyearling juveniles among Chinook salmon populations. Furthermore, this approach may provide a useful means to track and evaluate aggregate effects of habitat changes on the productivity of Endangered Species Act (ESA) listed Chinook salmon populations over time.

Floating bird nests provide resources for wildlife: ecological roles of vertebrates using Aechmophorus grebe nests at Clear Lake, California

Floating bird nests occur ephemerally in many wetlands, providing resources for wildlife, but the species using such nests and their ecological roles are poorly studied. Grebes (Podicipedidae) construct floating nests anchored to vegetation. During 2010–2017 we studied the vertebrates using nests of the colonially-nesting western grebe (Aechmophorus occidentalis) and Clark’s grebe (A. clarkii) at Clear Lake, California. In addition to both grebe species using each other’s nests for copulation and egg dumping, we identified 47 other species of vertebrates using Aechmophorus grebe nests, including one fish, one amphibian, two turtles, one snake, 39 birds, and three mammals. Ecological roles of vertebrates using grebe nests included: egg dumping (one bird); predation on grebe eggs, chicks, or adults (four birds and three mammals); scavenging on broken grebe eggs (five birds); resting (one amphibian, three reptiles, and 15 birds); foraging for non-avian prey on nests (13 birds) or in adjacent water (five birds); and incidental destruction of grebe eggs (one fish and two reptiles) and nests (many species). Floating grebe nests undergo a process of ecological succession. Egg dumping, predation, and scavenging occur during early stages of nest development and maintenance. Once abandoned, older nests are used for resting or foraging for prey in nearby water. Decomposing nests are colonized by arthropods which are preyed upon by birds. Because floating bird nests increase food web complexity by attracting aquatic, semiaquatic, and terrestrial organisms at all trophic levels, protecting the engineers and their nests should be considered a conservation priority by wetland managers.

When warmer means weaker: high temperatures reduce behavioural and immune defences of the larvae of a major grapevine pest

Phytophagous insects evolving in agroecosystems express numerous defences when faced with myriads of natural enemies. Such defensive traits might impair the effectiveness of biological control relying on these natural enemies, mostly parasitoids. In the case of parasitoid threat, these defences consist of the avoidance of the parasitoid (reduced exposure to antagonists through shortening of developmental time), hindrance of oviposition (evasive behaviours and morphological protection) or destruction of the parasitoid eggs (encapsulation and melanisation by means of the immune system). Previous works focused on one defensive trait only when investigating the effects of temperature on host resistance. By doing so, they assumed that all defensive traits would respond uniformly to a change occurring in thermal environment, which remains an undocumented fact. To test this assumption in the context of global warming, we adopted a global overview of host resistance by examining the effects of rising temperatures on multiple defensive traits used by the grape pest, Lobesia botrana, against its larval parasitoids. Although warmer conditions led to reduced exposure to parasitoids by accelerating larval development, warmer conditions also elicited extensive weakening of behavioural and immune defences. These results confirm that temperatures might differently modulate the levels of expression of several defensive traits. An increase in growth rate and pupal mass also occurred, especially for females, which may contribute to greater pest fecundity in the future. However, the decline of L. botrana resistance might enhance the efficiency of the biological control naturally exerted by parasitoids in vineyards, thereby limiting the damage to crops.

Cost-benefit analysis for invasive species control: the case of greater Canada goose Branta canadensis in Flanders (northern Belgium).

BackgroundSound decisions on control actions for established invasive alien species (IAS) require information on ecological as well as socio-economic impact of the species and of its management. Cost-benefit analysis provides part of this information, yet has received relatively little attention in the scientific literature on IAS.MethodsWe apply a bio-economic model in a cost-benefit analysis framework to greater Canada goose Branta canadensis, an IAS with documented social, economic and ecological impacts in Flanders (northern Belgium). We compared a business as usual (BAU) scenario which involved non-coordinated hunting and egg destruction with an enhanced scenario based on a continuation of these activities but supplemented with coordinated capture of moulting birds. To assess population growth under the BAU scenario we fitted a logistic growth model to the observed pre-moult capture population. Projected damage costs included water eutrophication and damage to cultivated grasslands and were calculated for all scenarios. Management costs of the moult captures were based on a representative average of the actual cost of planning and executing moult captures.ResultsComparing the scenarios with different capture rates, different costs for eutrophication and various discount rates, showed avoided damage costs were in the range of 21.15 M€ to 45.82 M€ under the moult capture scenario. The lowest value for the avoided costs applied to the scenario where we lowered the capture rate by 10%. The highest value occurred in the scenario where we lowered the real discount rate from 4% to 2.5%.DiscussionThe reduction in damage costs always outweighed the additional management costs of moult captures. Therefore, additional coordinated moult captures could be applied to limit the negative economic impact of greater Canada goose at a regional scale. We further discuss the strengths and weaknesses of our approach and its potential application to other IAS.