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International audience; Adoption of practices that reduce the risk of pest outbreaks is one of the pillars of agroecology and is largely based on biological control. Multiple infield and landscape parameters affect biocontrol, but the effects of conservation soil management on biological control have been poorly investigated over crop season. By comparing winter wheat fields within the same landscape but with different soil management, the direct and indirect effects of soil management (conservation and conventional systems) on natural enemies’ communities and their biological control on aphids was studied from the tillering stage to the harvest. In addition to aphid infestation, two families of the main natural enemies’ guilds were monitored, as well as their associated services: aphid parasitoid, a specialist and flying natural enemy, with parasitism service, and carabid beetles, a generalist and ground-dwelling predator, with aphidophagy service. Soil conservation system hosted more abundant and diverse carabid beetles’ assemblages, and received higher aphidophagy service in June than conventional system. However, neither parasitoid abundance, nor parasitism rates, were affected by soil management. Aphid infestation and its associated damage did not depend on soil management either. Our results suggest that ground-dwelling natural enemies are more impacted by soil management than foliage-dwelling natural enemies, which is partly reflected in aphid biocontrol. In agricultural systems with reduced soil perturbation, direct mortality on ground-dwelling communities due to tillage may be lower than in a conventional system, but habitat heterogeneity is also greater, increasing the number of ecological niches for natural enemies. Both factors are supposed to favor an early presence of natural enemies and a tendency toward a precocious aphidophagy service is indeed observed in conservation system.

Extreme temperatures and scarce precipitation in deserts have led to abiotic factors often being regarded as more important than biotic ones in shaping desert communities. The presumed low biological activity of deserts is also one reason why deserts are often overlooked by conservation programs. We provide the first quantification of predation intensity from a desert ecosystem using artificial sentinel prey emulating caterpillars, a standardized monitoring tool to quantify relative predation pressure by many invertebrate and vertebrate predators. The study was conducted in a protected natural area affected by oil spills in 1975 and 2014; hence, we assessed the potential effects of oil pollution on predation rates. We found that predation was mostly due to invertebrate rather than vertebrate predators, fluctuated throughout the year, was higher at the ground level than in the tree canopy, and was not negatively affected by the oil spills. The mean predation rate per day (12.9%) was within the range found in other ecosystems, suggesting that biotic interactions in deserts ought not to be neglected and that ecologists should adopt standardized tools to track ecological functions and allow for comparisons among ecosystems., Extreme environments such as deserts are expected to have low biodiversity and, therefore, reduced biotic interactions. We addressed this assumption by measuring invertebrate and vertebrate predation rates in a hyper‐arid desert using a standardized monitoring tool that allows recording predator activity in a quantitative, comparable way. We found that the mean predation rate (12.9% per day) is within the range found in other ecosystems, suggesting that this biotic function is no less important in deserts than elsewhere.

Frequent extreme weather events, which jeopardize agriculture by affecting crop health, characterize the ongoing climate change. Temporary patches where sown plants are poorly developed (hereafter “field defects”) are likely to increase with climate change and can be colonized by other plant species. Although perennial non-crop habitats can act as refuges for beneficial insects in agricultural landscapes and increase ecosystem services (ESs) in neighbouring arable fields, the relevance of field defects is unknown. Here, we quantified two ESs (pest and weed seed predation) in field defects within oilseed rape crops and related the ES levels with the activity-density of ground beetles and temperature. In 10 fields, we used artificial caterpillars made of plasticine and seed cards of two weed species (Taraxacum sp. and Stellaria sp.) to quantify the ESs in two sampling periods (spring and summer) and three habitat types: field defects, crops grown in standard conditions (field interiors) and crop-defect boundaries. Ground beetles were sampled using pitfall traps and classified into feeding guilds and body-size classes. Insects and mammals were the main pest predators, and predation increased in summer but did not differ among habitats. Seed predation rates for both species were significantly higher in summer. Predation upon Taraxacum seeds was higher in the field interiors, whereas the predation rate upon Stellaria seeds was significantly higher in the field interiors and defects compared to that in the crop-defect boundaries. The predation rate by insects increased with the activity-density of the medium- and large-sized carnivorous carabids, whereas the seed predation rate for both weed species was positively related to the activity-density of medium-sized herbivorous carabids. Finally, the mean and maximum temperatures were negatively linked to the predation rates on artificial caterpillars and seeds of Taraxacum, respectively. Our results suggest that these ephemeral habitats are not related to a strong decrease in ecosystem services; thus, field defects may not cause substantial changes in ES provisioning. We confirmed that ground beetles are important providers of both investigated ESs and showed that microclimatic conditions might play an important role in the regulation of ESs in agroecosystems. Grant Agency of the Czech Republic (18-26542S); Faculty of Environmental Sciences, Czech University of Life Sciences Prague (IGA) (42110/1312/3118) info:eu-repo/semantics/publishedVersion

Urbanization is one of the most important global trends which causes habitat reduction and alteration which are, in turn, the main reasons for the well-documented reduction in structural and functional diversity in urbanized environments. In contrast, effects on ecological mechanisms are less known. Predation is one of the most important ecological functions because of its community-structuring effects. We studied six forest habitats along a riverside urbanization gradient in Szeged, a major city in southern Hungary, crossed by the river Tisza, to describe how extreme events (e.g., floods) as primary selective pressure act on adaptation in riparian habitats. We found a generally decreasing predation pressure from rural to urban habitats as predicted by the increasing disturbance hypothesis (higher predator abundances in rural than in urban habitats). The only predators that reacted differently to urbanization were ground active arthropods, where results conformed to the prediction of the intermediate disturbance hypothesis (higher abundance in moderately disturbed suburban habitats). We did not find any evidence that communities exposed to extreme flood events were preadapted to the effects of urbanization. The probable reason is that changes accompanied by urbanization are much faster than natural landscape change, so the communities cannot adapt to them.

We studied the impact that two agro-ecological service crops or ASC, (vetch and barley), and two different ASC termination techniques (using a roller crimper or green manure) had on predation pressure in an organic vegetable system. We compared these two ASC termination techniques with a biodegradable plastic mulch, commonly used to control weeds in vegetable organic systems, over two consecutive growing seasons (2014–2015). Predation pressure was evaluated by means of artificial caterpillars made of green plasticine. Attack marks left on them were assigned to predators including chewing insects, birds and mammals. The frequencies of attack were significantly correlated with the activity density of carabids. In both experiments, carabid activity density was higher in ASC terminations than in the biodegradable plastic mulch control. Predation rate was significantly higher in the field with vetch flattened by roller crimper, while no significant difference was detected between termination techniques or in comparison with the control when barley was used as an ASC. The rate of ASC decomposition was higher in vetch than in barley and this could be the reason for the higher activity density of springtails in vetch. Carabid activity density was also positively correlated with springtail abundance. In conclusion, our field experiments showed that artificial caterpillars could represent a good standardized method to assess predation pressure in different habitats.

Humankind draws important benefits from large-scale ecological processes termed ecosystem services, yet the status of several of them is declining. Reliable monitoring methods are essential for tracking the status of ecosystem services. Predation is the mainstay of natural pest control, a key ecosystem service. We used green plasticine caterpillars to monitor predation pressure, and to obtain baseline data on predator activity in transgenic Bt versus non-Bt maize fields in Old and New World countries. Predation pressure was measured at ground and canopy levels using an identical, small-plot experimental design in four European countries (Denmark, Slovakia, Romania and Italy) and Argentina. Total predation rate in maize was 11.7%d −1 (min. 7.2%d −1 in Argentina, max. 29.0%d −1 in Romania). Artificial caterpillars were attacked both by invertebrates (mostly chewing insects with 42.0% of the attack marks, and ants with 7.1%, but also predatory and parasitoid wasps, spiders and slugs), and vertebrates (small mammals 25.5%, and birds 20.2%). Total predation at ground level (15.7%d −1 ) was significantly higher than in maize canopies (6.0%d −1 ) in all countries, except Argentina. We found no significant differences between predator pressure in Bt versus non-Bt maize plots. The artificial caterpillar method provided comparable, quantitative data on predation intensity, and proved to be suitable for monitoring natural pest control. This method usefully expands the existing toolkit by directly measuring ecological function rather than structure.

South America is undergoing a rapid and large scale conversion of natural habitats to cultivated land. Ecosystem services (ESs) still remain important but their level and sustainability are not known. We quantified predation intensity in an Argentinian agricultural landscape containing remnants of the original chaco serrano forest by using artificial sentinel prey. We sought to identify the main predators, and the effect of landscape configuration and maize phenology on predation pressure by invertebrate and vertebrate predators in this landscape. The most common predators were chewing insects (50.4% predation events), birds (22.7%), and ants (17.5%). Overall predation rates in forest fragments (41.6% d-1) were significantly higher than in the surrounding maize fields (21.5% d-1). Invertebrate predation was higher inside and at the edge of forest fragments than within fields, and did not change with increasing distance from a fragment edge, indicating a lack of spillover from the native habitat remnants to the cultivated matrix at the local scale. Distance from a continuous forest had a positive impact on predation by invertebrates and a negative impact on vertebrate predation. Fil: Ferrante, Marco. Aarhus University. Flakkebjerg Research Centre. Department of Agroecology; Dinamarca Fil: González, Ezequiel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; Argentina Fil: Gabor L., Lovei. Aarhus University. Flakkebjerg Research Centre. Department of Agroecology; Dinamarca

Urbanization is one of the most important processes shaping our environment, which causes habitat reduction and alteration which are, in turn, the main reasons for the reduced structural and functional diversity in urbanized environments. Predation is one of the most important ecological functions because of its community-structuring effects. Quantification of predation on invertebrate prey is difficult, because the attacks are mostly cryptic and it is rare when evidence is present. Using dummy prey, which is fixed to a surface, the marks left by predators allows us to identify them. Current evidence indicates that predation pressure is lower in urban than rural areas. According to the natural flow-regime paradigm, extreme events (e.g. floods) constitute a primary adaptive pressure in riparian habitats. We tested the validity of the paradigm in urbanized habitats. Our study site was in and around the city of Szeged (Hungary), along two urbanization gradients selected according to the Globenet protocol along the banks of the river Tisza and Maros. Data collection was conducted from April to October, 2014-2016. Both urbanization gradients included rural, suburban and urban areas, each characterised by an increase in the built up area (0%-25%-50%), intensity of forest management, and visitation rates by city residents. Overall 12672 dummy caterpillars ware placed, 6336 were on the ground level and 6336 on tree trunks. The dummy caterpillars (20 mm long, 3 mm thick) were made of light green plasticine, using a modified garlic press, fixed to the bark of trees or on a suitable surface on the ground with superglue, exposed for 24 h. The marks were identified using a hand-held magnifying glass (10 x). Overall the most active predator group was small mammals, followed by insects and birds. Urban predation activity on ground level, caused mainly by carabid beetles was significantly lower than the suburban or rural ones. Carabid predation pressure was higher in suburban than in rural habitats, while all other predator groups (other insects, birds and small mammals) had a decreasing trend towards urban habitats. This means, that all studied predator groups act according to the Gray’s increasing disturbance hypothesis, while carabid beetles react to urbanization according to Connell’s intermediate disturbance hypothesis. We found no evidence for the natural flow-regime paradigm along the examined urbanization gradients.

Non-crop habitats can act as refuge for insects in agricultural landscapes and increase ecosystem services (ESs) in neighboring arable fields. Among the different types of non-crop habitats, field defects are temporary patches where sown plants are poorly developed and other plant species emerge. These defects can be common and large in years with extreme weather conditions. However, their relevance as habitat for beneficial insects and ESs provision is unknown. Here, we quantified two ESs (pest and weed seed predation) in field defects within oilseed rape crops and related ESs levels with the activity-density of ground beetles and temperature. In 10 fields, we used artificial caterpillars made of plasticine and seed cards of two weed species (Taraxacum sp. and Stellaria sp.) to quantify ESs in two sampling periods (spring and summer) and in three habitat types: field defects, standardly grown crop (field interiors) and crop-defect boundaries. Ground beetles were sampled using pitfall traps and classified into feeding guilds and body size classes. Insects and mammals were the main pest predators and predation increased in summer, but did not differ among habitats. Seed predation rates for both species were significantly higher in summer. Predation of Taraxacum seeds was higher at field interiors, whereas predation of Stellaria was significantly higher at field interiors and defects, compared to crop-defect boundaries. Insect predation increased with the activity-density of medium and large carnivorous carabids, whereas seed predation for both weed species was positively related to the activity-density of medium-sized herbivorous carabids. Finally, temperature was negatively linked to predation of artificial caterpillars and seeds of Taraxacum.

International audience; The sustainability of organic vegetable cropping relies on ecosystem services such as biocontrol. Vegetable agroforestry can combine perennial woody crops and non-woody crops, which may alter ground predator activity-density and predation potential. We used living sentinel prey (Cydia pomonella) to assess predation in two different months, as a function of three levels of canopy openness in an agroforestry system combining lettuce crops and grassy strips. Ground beetles and arachnids were sampled throughout the year and we analyzed summer data conjointly to assess potential differences in the activity-density of these major predators between treatments. We found significantly higher predation potential in June in all agroforestry treatments compared to the control. In August, however, no differences were observed. Ground beetles and Opiliones were the major predators involved in observed predation events at both sampling periods. Differences in predation potential in June (- 35% in the control compared to agroforestry treatments) could be due to differences in Pterostichus madidus and Opiliones activity-density, which may have increased due to warmer temperatures under trees compared to the control plot.

Lepidoptera is one of the most diverse orders of insects, their larvae are very abundant in many habitats, and frequent prey of various predators. To decrease predation risk, caterpillars developed several means of defence, among them timing their activity to avoid predators (seeking enemy-free time). Although the enemy-free time hypothesis is often invoked to explain caterpillar behaviour, empirical evidence for it is scarce. We tested whether such enemy-free time exists in a temperate forest by comparing predation pressure on artificial caterpillars during day and night on the ground in forest fragments in Denmark. We found a high predation rate, 23.9% d(-1), and higher predation rate at night (30.9% d(-0.5)) than during the day (17.0% d(-0.5)), both by invertebrate (23.3% d(-0.5) vs. 12.4% d(-0.5)) and vertebrate (8.5% d(-0.5) vs. 3.3% d(-0.5)) predators. The most important predators were chewing insects (73.4% of all attacks) and small mammals (19.0%). Attack rates on red caterpillars were higher (30.0% d(-1)) than on green ones (19.5% d(-1)). Overall, these data do not support the idea that night activity can provide enemy-free time for solitary caterpillars on the temperate forest floor.

Urbanisation results in a marked modification of habitats and influences several ecological processes, some of which give rise to beneficial ecological services. Natural pest control, the effect of predators on prey is one of such services. We quantified changes in the incidence of predation with increasing levels of urbanisation using artificial caterpillars made of green plasticine. Potential predators can be identified by the "attack marks" they leave on these artificial caterpillars. We conducted this study from May to October 2010 around the city of Sorø (Zealand, Denmark), in forests along an urbanisation gradient (rural-suburban-urban). Artificial caterpillars were placed on the ground in order to obtain an estimate of the incidence of predation at ground level. Half (50%) of the 1398 caterpillars were "attacked" and 28.8% of the bites were those of chewing insects. We attributed the majority of these to carabids, the most common group of ground-active arthropods. Chewing insects exerted the greatest predation pressure in the original forest (52.1%), with lower values recorded in the suburban (10.1%) and urban (16.4%) forest fragments. Ants were responsible for only 4.7% of the attacks in forest, 11.3% in suburban and 16.4% in urban forest fragments. Mammals exerted the highest predation pressure in suburban habitats (22.2% vs. 4.9% in forest, and 8.1% in urban forest fragments).

The sentinel prey method can quantify predation pressure in various habitats. Real prey is assumed to more realistically mimic the predator experience but the predator can rarely be identified. Artificial prey made of plasticine may lack real chemical cues, but provides information about predator identity. However, the relationship between predation pressure registered by artificial versus real prey is not clear. We tested the relative attractiveness of artificial caterpillars, and intact, wounded, or dead larvae of the cabbage moth (Mamestra brassicae) for the carabid predator Pterostichus melanarius Illiger (Coleoptera: Carabidae). P. melanarius adults were attracted to dead caterpillars more than to live or wounded ones. Coating artificial caterpillars with caterpillar haemolymph increased their attractiveness. However, predators were not attracted more to healthy, real caterpillars than to “untreated” artificial ones. We conclude that using artificial caterpillars does not underestimate predation pressure by this carabid on healthy caterpillars.

Author(s): Kross, Sara M. | Abstract: Farmers have few tools with which to objectively assess the true impact of avian species on crop production, partly because ecologists and conservationists have been slow to quantify the role of birds within agricultural settings. At an annual value of over $5.5 billion dollars, vineyards are the third-most-valuable agricultural crop produced in California. Vineyard area has rapidly expanded in California and now covers at least 820,000 acres. Encouraging growers to retain existing natural habitat around vineyards or install new habitat, such as hedgerows, is likely to have positive effects on biodiversity. However, viticulturists are often wary of actions that could increase wildlife numbers on their land, particularly birds, since they are considered one of the most damaging pests to vineyards worldwide. In California, over 67% of vineyard acres have some degree of bird damage, with estimates ranging from between 5.4% and 16.1% of crops damaged. Conversely, birds may provide vineyards with valuable pest control services by consuming insects in high numbers in the spring and summer. Quantifying these costs (bird damage) and benefits (insect pest control) for vineyards from birds as they relate to natural habitat is an essential step in understanding the net value of nature in vineyard ecosystems. In July 2015, I used a sentinel prey experiment in a California vineyard to measure the relationship between insect pest-control, bird damage, and distance from a riparian corridor. I found that over 40% of sentinel prey were consumed at the edge of the vineyard, and that birds damaged 12% of grapes. Depredation of sentinel prey and grape damage dropped at a similar rate with increasing distance from riparian habitat. These results suggest that birds may remove insect pests at a rate that could offset the damage caused by avian foraging once grapes are ripe, but further studies are needed to confirm this.

In cultivated landscapes, predatory arthropods play an important role for pest control. Traditionally, monitoring their effect on pests was done using indirect measures (e.g. characterising predator activity by the numbers of predators caught). However, the contribution of predators to predation is complicated by interactions such as cannibalism, intra-guild predation, and competition. Directly measuring predation is preferred, although ecological and logistical constraints make it difficult. Using artificial caterpillars to quantify arthropod predation is gaining more attention, as model prey are cheap, easy to use, and are informative about predator identity. In a field experiment in Denmark, performed between May and July 2014, we tested the relationship between predation rate measured using artificial caterpillars and the activity density of large (≥15mm) ground beetles collected using pitfall traps in winter wheat (Triticum aestivum). Forty-six percent (n=756/1637) of the artificial sentinel prey were attacked after 24 h, mostly by chewing insects (88%, n=665/756), and 1102 carabids with a size of ≥15mm were collected. Ground beetles were also the most common predatory group, followed by spiders and rove beetles (42.3%, 23.6%, and 22.9% of the total, respectively). We found a significant positive relationship (p

International audience; The biological control of crop pests is a valuable service provided by various beneficial organisms that are naturally present in agricultural landscapes. Semi-natural habitats has long been recognized as essential to preserve beneficial insects, but proof of their efficiency to enhance biological control of pests remains non conclusive. Here, we examined the variability of landscape effect on biological pest control and the way local agronomic practices may modulate it. Biological pest control was monitored in 80 commercial fields (arable crops and orchards) during three consecutive years in four contrasting French agricultural landscapes distributed along a double gradient of pesticide use and landscape complexity measured in a 1 km2 area centred on each field. Biocontrol efficacy in each field was assessed using three types of sentinel preys (weed seeds, moth eggs, and aphids). The effects of landscape simplification, pesticide use intensity and their interaction on the predation of each sentinel prey were analysed using generalised linear mixed models. At local level, the intensity of pesticide use reduced the predation of weed seeds and aphids. At landscape level, the proportion of the monitored crop reduced the predation of weed seeds and moth eggs. Finally, significant interactions between local and landscape factors were detected for each sentinel prey: (i) the predation of moth eggs was negatively influenced by landscape simplification at low pesticide use intensity only, whereas the effect was positive at high pesticide use intensity; (ii) aphid predation significantly decreased with increasing crop-wood interface length and proportion of meadow, but only at high pesticide use intensity; (iii) weed seed predation significantly decreased when land use diversity around the fields increased under high pesticide use intensity and, inversely, increased with land cover diversity around the fields at of low pesticide use intensity. These results suggest that reduction in pesticide use should be associated with the reinforcement of semi-natural habitats in agricultural landscape to enhance natural biocontrol.