Pest Regulation Research Articles

"Generalist" Aphid Parasitoids Behave as Specialists at the Agroecosystem Scale.

The degree of trophic specialization of interacting organisms impacts on the structure of ecological networks and has consequences for the regulation of crop pests. However, it remains difficult to assess in the case of parasitoids. Host ranges are often established by listing host records from various years and geographic areas in the literature. Here, we compared the actual hosts exploited at a local farm-scale by aphid parasitoids (Hymenoptera: Aphidiinae), to the available species listed as hosts for each parasitoid species. We sampled aphids and their parasitoids in cultivated and uncultivated areas in an experimental farm from April to November 2014 and thereafter used DNA-based data to determine whether a differentiation in sequences existed. Twenty-nine parasitoid species were found on 47 potential aphid hosts. Our results showed that the great majority of the parasitoid tested used fewer host species than expected according to data published in the literature and parasitized a limited number of hosts even when other potential hosts were available in the environment. Moreover, individuals of the most generalist species differed in their DNA sequences, according to the aphid species and/or the host plant species. At a local scale, only obligate or facultative specialist aphid parasitoids were detected. Local specialization has to be considered when implementing the use of such parasitoids in pest regulation within agroecosystems.

Does minimal pruning and reduced fungicide use impact spiders in the grapevine canopy?

Agricultural management should aim at high densities of beneficial organisms such as spiders. Here, we asked whether spiders in vineyards can be promoted either by using novel disease resistant grape varieties that allow for a reduced number of fungicide applications, or by minimal pruning which enhances the structural complexity of the grapevine canopy. We compared spider communities in vineyards planted with fungus-resistant varieties (PIWIs) to vineyards with traditional grapevine varieties, and minimally pruned vineyards to vertical shoot positioned vineyards. Densities of Theridiidae were more than doubled in fungus-resistant grape varieties, but the remaining families were not significantly affected. Minimal pruning enhanced Philodromidae and Dictynidae but reduced Salticidae. However, neither pruning method, nor the reduced fungicide use in PIWI vineyards, had significant effects on overall spider abundance or species richness. Hence, effects of vineyard management were family-specific and possible consequences for pest regulation will thus depend on the pest control potential of the involved families.

Investigating the Natural Mortality of Aphis gossypii (Hemiptera: Aphididae) on Cotton Crops in Tropical Regions Using Ecological Life Tables.

Studies on the natural factors contributing to pest regulation are fundamental to developing efficient integrated pest management programs. Chemical control is the main management method used for pests [e.g., Aphis gossypii (Glover)]. The studies of pest management with chemical control provide information that can be incorporated into integrated pest management programs to promote more sustainable pest control approaches. Here, we report the critical stages of A. gossypii and its abiotic and biotic natural mortality factors in cotton crops as a function of plant phenology using a life table. The critical stages of A. gossypii were the first and fourth instars. Together, the abiotic and biotic factors caused 94.31% of the mortality in the A. gossypii populations in cotton crops with plants in the vegetative, flowering, and fruiting stages. The key mortality factors were rainfall and predation. Syrphidae Allograpta exotica (Wiedemann) (Diptera: Syrphidae) and Chrysopidae Chrysoperla externa (Hagen) (Neuroptera: Chrysopidae) larvae, many Coccinellidae species Cycloneda sanguinea (L.) (Coleoptera: Coccinellidae), Eriopsis connexa (Germar) (Coleoptera: Coccinellidae), Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae), Hippodamia convergens (Guérin-Meneville) (Coleoptera: Coccinellidae), Scymnus rubicundus (Erichson) (Coleoptera: Coccinellidae) and Stethorus punctillum (Weise) (Coleoptera: Coccinellidae), one Anthocoridae species Orius insidiosus (Say) (Hemiptera: Anthocoridae), and individuals from the Araneidae family were responsible for the predation of A. gossypii. The results obtained in this study provide support for the idea that efforts to preserve natural enemies (e.g., predators) and rainfall monitoring should be adapted due to their importance for the regulation of A. gossypii populations in all the phenological stages of cotton in tropical regions.

Local perceptions and factors determining ecosystem services identification around two forest reserves in Northern Benin

BackgroundEcosystems provide humanity with goods and services known as ecosystem services. The value of these services represents a basis for political decision-making. To be sure that these decisions are made on a valid basis, policymakers require an understanding of the biophysical processes involved. This study was carried out around two forest reserves (Alibori-Supérieur and Ouénou-Bénou) in Northern Benin. It aimed to highlight the knowledge of the surrounding communities and their perceptions about the importance of the ecosystem services provided by these forest reserves as well as the factors that influence their knowledge and perceptions.MethodsPrimary data were collected from 25 group discussions in 25 villages surrounding the forest reserves based on predefined ecosystems services of the Millennium Ecosystems Assessment (MA). Multiple linear regression models were used to examine how socio-economic characteristics of the communities influenced the ecosystem services identification rate. Perceptions of importance, levels of satisfaction, and trends of services provided were analyzed using descriptive statistics.ResultsOur results showed that education level, poverty index, household size, and proximity to forests played an important role in the variation in knowledge of ecosystem services (P < 0.05). Provisioning services (such as crops supply, fuelwood, lumber, wild food, and medicinal plants) were mostly identified by the poorest villages located very close to the forests (P < 0.05). The importance of the provided services for well-being has been unanimously recognized. The most recognized cultural services were education and knowledge facilitation (84%) and spiritual value (76%). Climate regulation (84%) and pollination (84%) were the best-known regulating services. However, supporting services (soil formation and pest regulation) that are important for improving production systems were unknown to the communities.ConclusionEducation level, poverty index, and village proximity to the forest were important predictors of regulating and supporting services identification. But use of non-tangible services by local rural communities will require more emphasis on targeted environmental education specifically designed according to the needs of each group.

Pest-regulating networks of the coffee berry borer (Hypothenemus hampei) in agroforestry systems

Pest regulation in agroforestry systems (AFS) is beginning to be well-recognized, but the mechanisms implied in the interaction network between the environment, pests and predators in AFS are still not well-described. The aim of this work is to understand how plant diversity associated with AFS regulates the coffee berry borer (CBB) taking into account a tripartite interaction network: pest–predator–environment. It further seeks to understand how farmers' management practices can modify the regulating network. Using field data from coffee-based AFS and structural equation modeling, we assessed the effects of environmental conditions (% shade cover, tree area surface, coffee density) and farm management (conventional, integrated, organic) on (1) ant predatory groups, (2) the abundance and the damage from CBB and (3) their interactions. Percentage of shade cover was positively correlated to CBB initial infestation (through direct effect) and negatively through its effect on coffee phenology. A higher percentage of shade is also negatively related to damage intensity. Farmers’ practices significantly reduced the CBB population without considerable side effects on the ant predatory group, probably due to the high plant diversity within these farms. The abundance of the most diversified ant predatory group has a top-down effect on the peak of the CBB infestation rate. Our approach appears promising for a better understanding of the complex regulating network in coffee AFS and confirms the importance of an integrated management strategy to reduce CBB damage.

Multiple ecosystem services from field margin vegetation for ecological sustainability in agriculture: scientific evidence and knowledge gaps.

BackgroundField margin and non-crop vegetation in agricultural systems are potential ecosystem services providers because they offer semi-natural habitats for both below and above ground animal groups such as soil organisms, small mammals, birds and arthropods that are service supplying units. They are considered as a target area for enhancing farm biodiversity.MethodologyTo explore the multiple potential benefits of these semi-natural habitats and to identify research trends and knowledge gaps globally, a review was carried out following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. A total of 235 publications from the year 2000 to 2016 in the Scopus and Web of Science databases were reviewed.ResultsThe literature showed an increasing trend in the number of published articles over time with European studies leading in the proportion of studies conducted, followed by North America, Asia, South America, Africa and Australia. Several functional groups of organisms were studied from field margin and non-crop vegetation around agricultural lands including natural enemies (37%), insect pests (22%), birds (17%), pollinators (16%), soil macro fauna (4%) and small mammals (4%). Ecosystem services derived from the field margin included natural pest regulation, pollination, nutrient cycling and reduced offsite erosion. Some field margin plants were reported to host detrimental crop pests, a major ecosystem dis-service, potentially leading to increased pest infestation in the field.ConclusionThe majority of studies revealed the importance of field margin and non-crop vegetation around arable fields in enhancing ecosystem biodiversity. Promotion of field margin plants that selectively enhance the population of beneficial organisms would support sustainable food security rather than simply boosting plant diversity. Our analyses also highlight that agro-ecological studies remain largely overlooked in some regions.

Alternative prey impedes the efficacy of a natural enemy of mosquitoes

Adaptive foraging behaviour in the presence of multiple prey types may mediate stability to predator-prey relationships. For biological control agents, the presence of alternative prey may thus reduce ecological impacts towards target organisms, presenting a key challenge to the derivation of agent efficacies. Quantifications of non-target effects are especially important for generalist biocontrol agents in their regulation of pests, vectors and invasive species. We examined the predatory impact of the notonectid Anisops debilis towards larvae of the vector mosquito complex Culex pipiens in the presence of varying densities of alternative daphniid prey. Experimentally, we quantified functional responses of A. debilis towards target mosquito prey under different background daphniid compositions, and also tested for prey switching propensities by the notonectid predator. Increasing background densities of daphniids significantly reduced the predatory impact of notonectids on mosquitoes, characterised by reductions in attack rates, lengthening of handling times and lessening of maximum feeding rates. Furthermore, notonectids displayed a significant selective preference in favour of daphniid prey over mosquitoes, irrespective of prey proportions in aquatic environments. Accordingly, notonectids did not display a prey switching pattern. We thus demonstrate that the presence of alternative prey can dampen predatory impacts of notonectids towards mosquitoes, as compared to more simplistic pairwise systems with singular prey choice. Accordingly, the effects of stabilising mechanisms, such as adaptive foraging, should be further integrated in biocontrol agent assessments.

SensorTalk: An IoT Device Failure Detection and Calibration Mechanism for Smart Farming.

In an Internet of Things (IoT) system, it is essential that the data measured from the sensors are accurate so that the produced results are meaningful. For example, in AgriTalk, a smart farm platform for soil cultivation with a large number of sensors, the produced sensor data are used in several Artificial Intelligence (AI) models to provide precise farming for soil microbiome and fertility, disease regulation, irrigation regulation, and pest regulation. It is important that the sensor data are correctly used in AI modeling. Unfortunately, no sensor is perfect. Even for the sensors manufactured from the same factory, they may yield different readings. This paper proposes a solution called SensorTalk to automatically detect potential sensor failures and calibrate the aging sensors semi-automatically. Numerical examples are given to show the calibration tables for temperature and humidity sensors. When the sensors control the actuators, the SensorTalk solution can also detect whether a failure occurs within a detection delay. Both analytic and simulation models are proposed to appropriately select the detection delay so that, when a potential failure occurs, it is detected reasonably early without incurring too many false alarms. Specifically, our selection can limit the false detection probability to be less than 0.7%.

Characterization of Hymenopteran Parasitoids of Aphis fabae in an African Smallholder Bean Farming System through Sequencing of COI 'Mini-Barcodes'.

Parasitoids are among the most frequently reported natural enemies of insect pests, particularly aphids. The efficacy of parasitoids as biocontrol agents is influenced by biotic and abiotic factors. For example, hyperparasitoids can reduce the abundance of the primary parasitoids as well as modify their behavior. A field study was conducted at three contrasting elevations on Mount Kilimanjaro, Tanzania, to identify the parasitoids of aphids in smallholder bean farming agroecosystems. Sentinel aphids (Aphis fabae) on potted bean plants (Phaseolus vulgaris) were exposed in 15 bean fields at three elevations for 2 days. The sentinel aphids were then kept in cages in a greenhouse until emergence of the parasitoids, which were collected and preserved in 98% ethanol for identification. Of the 214 parasitoids that emerged from sentinel aphids, the greatest abundance (44.86%) were from those placed at intermediate elevations (1000–1500 m a.s.l), compared to 42.52% from the lowest elevations and only 12.62% from the highest elevation farms. Morphological identification of the parasitoids that emerged from parasitized aphids showed that 90% were Aphidius species (Hymenoptera: Braconidae: Aphidiinae). Further characterization by sequencing DNA ‘mini-barcodes’ identified parasitoids with ≥99% sequence similarity to Aphidius colemani, 94–95% sequence similarity to Pachyneuron aphidis and 90% similarity to a Charipinae sp. in the National Center for Biotechnology Information (NCBI) database. These results confidently identified A. colemani as the dominant primary aphid parasitoid of A. fabae in the study area. A Pachyneuron sp., which was most closely related to P. aphidis, and a Charipinae sp. occurred as hyperparasitoids. Thus, interventions to improve landscapes and farming practice should monitor specifically how to augment populations of A. colemani, to ensure any changes enhance the delivery of natural pest regulation. Further studies are needed for continuous monitoring of the hyperparasitism levels and the dynamics of aphids, primary parasitoids, and secondary parasitoids in different cropping seasons and their implications in aphid control.

Perceiving the invisible: Formal education affects the perception of ecosystem services provided by native areas

Landowners' decisions reshape landscapes, affecting the distribution and maintenance of ecosystem services (ESs). In Brazil, 53% of all remaining native vegetation is on private farms, reinforcing the importance of these stakeholders. The aim of this study was to identify landowners’ perceptions of the native areas on their properties as sources of ESs, to support future conservationist management strategies. We tested whether personal variables (gender, age and years of formal education), and farm characteristics (type and size) were determinant in their perceptions. We interviewed 75 landowners in the Brazilian savanna region, using a questionnaire and paired images strategy (e.g., pictures of soybean cultivation with and without native forest vegetation). Our analyses revealed that landowners perceive native areas as providing ESs. Gender, age and size of farm did not affect the landowners’ perceptions of ESs. However, we observed that years of formal education increased the chance of perceiving ESs which are more difficult to observe (pollination and pest regulation). Those services may require more scientific background to be understood. These results highlight with regard to perception of some ESs, education is a stronger factor than experience based on land-use activities.

Effects of cover crops on multiple ecosystem services: Ten meta-analyses of data from arable farmland in California and the Mediterranean

Cover crops are considered to be beneficial for multiple ecosystem services, and they have been widely promoted through the Common Agricultural Policy (CAP) in the EU and Farm Bill Conservation Title Programs, such as the Environmental Quality Incentives Program (EQIP), in the USA. However, it can be difficult to decide whether the beneficial effects of cover crops on some ecosystem services are likely to outweigh their harmful effects on other services, and thus to decide whether they should be promoted by agricultural policy in specific situations. We used meta-analysis to quantify the effects of cover crops on five ecosystem services (food production, climate regulation, soil and water regulation, and weed control) in arable farmland in California and the Mediterranean, based on 326 experiments reported in 57 publications. In plots with cover crops, there was 13% less water, 9% more organic matter and 41% more microbial biomass in the soil, 27% fewer weeds, and 15% higher carbon dioxide emissions (but also more carbon stored in soil organic matter), compared to control plots with bare soils or winter fallows. Cash crop yields were 16% higher in plots that had legumes as cover crops (compared to controls) but 7% lower in plots that had non-legumes as cover crops. Soil nitrogen content was 41% lower, and nitrate leaching was 53% lower, in plots that had non-legume cover crops (compared to controls) but not significantly different in plots that had legumes. We did not find enough data to quantify the effects of cover crops on biodiversity conservation, pollination, or pest regulation. These gaps in the evidence need to be closed if cover crops continue to be widely promoted. We suggest that this novel combination of multiple meta-analyses for multiple ecosystem services could be used to support multi-criteria decision making about agri-environmental policy.

Crop rotations in a climate change scenario: short-term effects of crop diversity on resilience and ecosystem service provision under drought

Given the challenges posed to agriculture by future climatic changes, and the need to reduce environmental impacts, a key challenge is to develop resilient food production systems. Ecological intensification is an approach proposed to partially replace external inputs with the provision of biodiversity-derived ecosystems services to either maintain or increase food production. One promising practice is crop diversification, which has the potential to improve the provision of multiple ecosystem services underpinning agricultural production, and to confer resilience to abiotic stresses. This study measured a variety of ecosystem services (yield quantity and quality, soil services, pest regulation), and resistance indicators (canopy temperature and senescence rates) under stressed and controled conditions, at three levels of crop rotational diversity in the third year of the rotations. We found that increased crop diversity can maintain yields with reduced external inputs, under varying climatic conditions, with yield increases of 1 t/ha on average, and that diversifying crop rotations can improve stress resistance resulting in more resilient systems. Higher crop diversity resulted in no trade-offs between our measured ecosystem services and increased synergistic effects between stress resistance and crop production and stress resistance and pest regulation. However, farmers will need to use a combination of management approaches, alongside diversifying crop rotations, to maximise the potential of ecological intensification.

Servicios de la avifauna (high-mobile link species) en mosaicos agroforestales: regeneración forestal y regulación de plagas

Rebollo, S., Rey-Benayas, J.M., Villar-Salvador, P., Perez-Camacho, L., Castro, J., Molina-Morales, M., Leverkus, A.B., Baz, A., Martinez-Baroja, L., Quiles, P., Gomez-Sanchez, D., Fernandez-Pereira, J.M., Meltzer, J., Monteagudo, N., Ballesteros, L., Cayuela, L., de las Heras, D. Garcia-Salgado, G., Martinez-Hesterkamp, S. 2019. Services provided by birds (high-mobile link species) in farmland and forest mosaics: forest regeneration and plague regulation. Ecosistemas 28(2): 32-41. Doi.: 10.7818/ECOS.1736 The elements that support functions and ecosystem services are not well known yet, and this gap reduces our capacity to plan the conservation, restoration, and management of ecosystems. Among these elements, the role of avifauna is especially relevant as birds are high-mobile link species that connect different landscape units. This article analyzes important ecosystem services driven by biological interactions that are mediated by birds in farmland and forest mosaics. We propose three specific goals: to assess the role of (1) corvids in the dispersal and recruitment of oak species, (2) insectivorous birds in pest regulation of woody crops, and (3) raptors in regulation of plague birds in vineyards. Our results show that the avifauna performs key functions and services for forest regeneration and pest regulation in agroforestry mosaics. We identified species that were not known to perform relevant functions, particularly the magpie (Pica pica) and its effective dispersion of nuts and acorns, and the honey buzzard (Pernis apivorus) and its high consumption of Asian black hornet (Vespa velutina). The installation of nest-boxes in woody crops increases the populations of insectivorous birds that regulate pests; however, the capacity of pest control is moderate and depends on the environmental context or case study. The diurnal raptors thriving in the studied landscapes contribute to the control of agricultural pests such as the spotless starling (Sturnus unicolor). We propose to integrate the services provided by birds in landscape planning to achieve more sustainable development systems.

Wheat genotypic diversity and intercropping to control cereal aphids

Increasing intrafield plant diversity has been shown to regulate pest populations. Mixing wheat cultivars and intercropping winter wheat and white clover are both promising agroecological practices. On field experiments over two growing seasons, we combined both practices and examined the impact on aphid populations and on wheat production. Results show that combining intra- and interspecific diversity did not outperform each practice individually in reducing aphid populations. Taken separately, intercropping tended to have lower aphid infestation, while it was intermediate in cultivar mixtures. Yearly variation in climatic conditions impacted wheat and clover development, as well as the appearance of aphid peaks. Wheat yields and grain nitrogen content were reduced in intercropping by 10% and 7%, respectively, but not in cultivar mixtures. Our findings suggest that intrafield diversification may regulate wheat aphids to some extent, but combining two diversification practices did not result in an attractive trade-off between pest regulation and wheat production in real farming conditions.

Bottom-up regulation of a tritrophic system by Beet yellows virus infection: consequences for aphid-parasitoid foraging behaviour and development.

Effects of plants on herbivores can cascade up the food web and modulate the abundance of higher trophic levels. In agro-ecosystems, plant viruses can affect the interactions between crops, crop pests, and natural enemies. Little is known, however, about the effects of viruses on higher trophic levels, including parasitoids and their ability for pest regulation. We tested the hypothesis that a plant virus affects parasitoid foraging behaviour through cascading effects on higher trophic levels. We predicted that the semi-persistent Beet yellows virus (BYV) would influence plant (Beta vulgaris) quality, as well as aphid host (Aphis fabae) quality for a parasitoid Lysiphlebus fabarum. We determined amino acid and sugar content in healthy and infected plants (first trophic level), lipid content and body size of aphids (second trophic level) fed on both plants, as well as foraging behaviour and body size of parasitoids (third trophic level) that developed on aphids fed on both plants. Our results showed that virus infection increased sugars and decreased total amino acid content in B. vulgaris. We further observed an increase in aphid size without modification in host aphid quality (i.e., lipid content), and a slight effect on parasitoid behaviour through an increased number of antennal contacts with host aphids. Although the BYV virus clearly affected the first two trophic levels, it did not affect development or emergence of parasitoids. As the parasitoid L. fabarum does not seem to be affected by the virus, we discuss the possibility of using it for the development of targeted biological control against aphids.

Hysteresis and critical transitions in a coffee agroecosystem

Seeking to employ ecological principles in agricultural management, a classical ecological debate provides a useful framing. Whether ecosystems are controlled from above (predators are the limiting force over herbivores) or from below (overutilization of plant resources is the limiting force over herbivores) is a debate that has motivated much research. The dichotomous nature of the debate (above or below) has been criticized as too limiting, especially in light of contemporary appreciation of ecological complexity-control is more likely from a panoply of direct and indirect interactions. In the context of the agroecosystem, regulation is assumed to be from above and pests are controlled, a way of using ecological insights in service of an essential ecosystem service-pest control. However, this obvious resolution of the old debate does not negate the deeper appreciation of complexity-the natural enemies themselves constitute a complex system. Here we use some key concepts from complexity science to interrogate the natural functioning of pest regulation through spatially explicit dynamics of a predator and a disease operating simultaneously but distributed in space. Using the green coffee scale insect as a focal species, we argue that certain key ideas of complexity science shed light on how that system operates. In particular, a hysteretic pattern associated with distance to a keystone ant is evident.

Farmers’ management of functional biodiversity goes beyond pest management in organic European apple orchards

Supporting functional biodiversity (FB), which provides natural pest regulation, is an environmentally sound and promising approach to reduce pesticide use in perennial cultures such as apple, especially in organic farming. However, little is known about farmers’ practices and motivations to implement techniques that favor FB, especially whether or not they really expect anything from FB in terms of pest regulation. In fact, FB-supporting techniques (FB-techniques) are massively questioned by practitioners due to inadequate information about their effectiveness. An interview survey was performed in eight European countries(i) to describe farmers’ practices and identify promising FB-techniques: (ii) to better understand their perceptions of and values associated with FB; and (iii) to identify potential drivers of (non-)adoption. Fifty-five advisors and 125 orchard managers with various degrees of experience and convictions about FB were interviewed and a total of 24 different FB-techniques which can be assigned to three different categories (ecological infrastructures, farming practices and redesign techniques) were described. Some were well-established measures (e.g., hedges and bird houses), while others were more marginal and more recent (e.g., animal introduction and compost). On average, farmers combined more than four techniques that had been implemented over a period of 13 years, especially during their establishment or conversion period. In general, it was difficult for farmers to evaluate the effectiveness of individual FB-techniques on pest regulation. They considered FB-techniques as a whole, targeting multiple species, and valued multiple ecosystem services in addition to pest regulation. The techniques implemented and their associated values differed among farmers who adopted various approaches towards FB. Three different approaches were defined: passive, active and integrated. Their appraisal of FB is even more complex because it may change with time and experience. These findings provide empirical evidence that the practical implementation of promising techniques remains a challenge, considering the diversity of situations and evaluation criteria. Increased cooperation between researchers, farmers and advisors should more effectively target research, advisory support and communication to meet farmers’ needs and perceptions.

Mass Seasonal Migrations of Hoverflies Provide Extensive Pollination and Crop Protection Services

Despite the fact that migratory insects dominate aerial bioflows in terms of diversity, abundance, and biomass [1-6], the migration patterns of most species, and the effects of their annual fluxes between high- and low-latitude regions, are poorly known. One important group of long-range migrants that remain understudied is a suite of highly beneficial species of hoverfly in the tribe Syrphini, which we collectively term "migrant hoverflies." Adults are key pollinators [7-10] and larvae are significant biocontrol agents of aphid crop pests [11], and thus, it is important to quantify the scale of their migrations and the crucial ecosystem services they provide with respect to energy, nutrient, and biomass transport; regulation of crop pests; and pollen transfer. Such assessments cannot be made by sporadic observations of mass arrivals at ground level, because hoverflies largely migrate unnoticed high above ground. We used insect-monitoring radars [12] to show that up to 4 billion hoverflies (80tons of biomass) travel high above southern Britain each year in seasonally adaptive directions. The long-range migrations redistribute tons of essential nutrients (nitrogen [N] and phosphorus [P]) and transport billions of pollen grains between Britain and Europe, and locally produced populations consume 6 trillion aphids and make billions of flower visits. Migrant hoverfly abundance fluctuated greatly between years, but there was no evidence of a population trend during the 10-year study period. Considering that many beneficial insects are seriously declining [7, 10, 13-19], our results demonstrate that migrant hoverflies arekey to maintaining essential ecosystem services.

Of bugs and men: How forest pests and their management strategies are perceived by visitors of an urban forest

Larger forest patches in urban areas are highly valuable recreation sites that provide the urban population with various ecosystem services. Yet they are highly vulnerable to biological pests, especially in the light of climate change. The growing need to intervene against forest pests needs to be clearly but carefully communicated to the urban forest visitors in order to minimize conflicts. In this paper, a survey with 554 complete responses, conducted in the forest district of the “Teufelssee” in south-east Berlin, Germany, sheds first light on visitors’ perceptions of biological pests and their management. Results of Chi square statistics and a series of Logit models indicate a clear predisposition against pesticide or biocide interventions, while at the same time, showing remarkable positive tendencies towards mechanical interventions or measures taken on the individual-tree level. There are positive correlations between the age and the knowledge about pests (Kendall-Tau-b τB = 0.165) and between the age and the knowledge about pest regulation (τB = 0.182). Positive correlations also exist between level of education and pest knowledge (τB = 0.1) and knowledge about their regulation (τB = 0.08), respectively. Elderly respondents tend to vote for faster interventions. Overall, a large majority of the respondents would be willing to participate in a volunteer mapping of pests while visiting the forest. The results of this study can be used to inform urban forest management to modify and optimize their communication and information policies concerning pests and substantiated interventions.

Functional diversity of predators and parasitoids does not explain aphid biocontrol efficiency

Many studies demonstrate an important role of natural enemy biodiversity in the regulation of agricultural pests, but the role of different aspects of biodiversity in influencing this crucial ecosystem service remain controversial. We hypothesised that the functional diversity generated by combining divergent consumer groups (roaming coccinellid predators and parasitoid wasps) fosters complementarity, enhancing aphid biocontrol. We tested this using experimental mesocosms containing plants, aphids and natural enemies located in a greenhouse. We compared the aphid control efficiency (final aphid abundance) of low functional diversity treatments (two parasitoid species, or two predator species) with high functional diversity treatments (all four possible predator-parasitoid combinations). We also included all four enemies as single species treatments to allow calculation of the non-additive effects of combining natural enemies. Results showed that biocontrol (final aphid abundance) was driven by the species identity of natural enemies and positive non-additive effects in two treatments in which the most efficient predator species was combined with a parasitoid species and the other predator species, respectively. Functional diversity did not consistently influence biocontrol or non-additive effects. In conclusion, functional diversity, as defined by differences between roaming predator and parasitoid functional groups, failed to consistently explain biocontrol efficiency in our study. This calls for consideration of finer-scale functional traits and how they govern natural enemy interactions and cascading effects across ecosystems.