Ladybird Abundance Research Articles

Semi‐natural habitat, but not aphid amount or continuity, predicts lady beetle abundance across agricultural landscapes

Abstract The amount of semi‐natural habitat surrounding farm fields is a common but inconsistent predictor of natural enemy populations and predation services. Standard land cover metrics may not accurately capture the actual availability of limiting resources for natural enemies and can miss important dynamics across space and time. Theory from animal movement and landscape ecology predicts that regions with more, spatio‐temporally continuous resources (i.e. food and shelter) should have larger predator populations and enhanced biological control. To test these predictions empirically, we designed a study measuring aphids, lady beetles and predation services in agricultural landscapes in Wisconsin, USA. In two study years, we sampled lady beetles and aphids in 336 crop fields (corn, soybean, alfalfa and small grains) and adjacent semi‐natural habitat patches (grasslands and woodlands) across 24 1.5 km buffer landscapes at four to seven time points each, and in 1 year, we assessed predation rates with sentinel egg cards. We used aphid counts to model habitat‐specific aphid phenologies, from which we calculated landscape indices of prey amount and continuity. These indices, along with semi‐natural habitat area, were used to predict lady beetle abundance. While there were strong differences in the abundance and timing of aphids by habitat, semi‐natural habitat amount was still a better predictor of lady beetle counts and sentinel egg predation than either aphid amount or continuity indices in these landscapes. Synthesis and applications. Our findings confirm the robust relationship between lady beetles and semi‐natural habitat in agricultural landscapes, and highlight the complexities of measuring fine‐scale resource heterogeneity in real landscapes. Retaining or adding woodland and grassland patches in agricultural landscapes is likely to support larger lady beetle populations and enhance predation in crop fields. Our results suggest that these habitats may be more important for shelter than prey continuity, though this mechanism warrants further investigation. Future work should continue to refine experimental methods for the successful integration of landscape ecology and animal behaviour to support conservation goals.

Field management practices and altitudes drive the abundance of ladybird beetles (Coleoptera: Coccinellidae) in cultivated cucurbit crops in Morogoro, Tanzania

Ladybird beetles are helpful insects in agricultural ecosystems affected by locally accepted agroecological techniques. Conventional farming practices are known to harm these insects, which led to the exploration of agroecology as an alternative. From May to November 2021, yellow pan traps, hand picking, and hand netting were utilised in cultivated cucurbits such as Cucumis sativus, Citrullus lanatus, and Cucurbita moschata. The study found 222 ladybird beetles from nine genera and twelve species. The plateau had 64.9% ladybirds, 46.4% in conventional fields, and 18.47% in agroecological fields. Mountain fields supplied 35.1%, conventional fields 24.77%, and agroecological fields 10.36%. Conventional plateau fields favoured Cheilomenes sulphurea, while agroecological fields selected Hippodamia variegata. Cheilomenes lunata dominated traditional fields in mountainous areas and agroecological fields. Ladybird beetles were more abundant in conventional fields across all seasons and agroecological zones, which were influenced by seasons, management strategies, and elevations. The present study found negative associations between ladybird abundance and maximum temperature, minimum temperature, mean temperature, number of flowers, and relative humidity. Mountainous precipitation increased ladybird abundance. This study shows how management practises, agroecological zones, and seasons affect ladybird populations, which can inform pest management strategies in agricultural systems and help conserve beneficial ladybird beetles.

Frequent insecticide applications in cotton fields offset the positive impact of surrounding semi-natural habitats on in-field ladybeetle abundance

Frequent insecticide applications in cotton fields offset the positive impact of surrounding semi-natural habitats on in-field ladybeetle abundance

Effect of spontaneous vegetation on beneficial arthropods in Mediterranean vineyards

Habitat destruction and land use intensification are major causes of arthropod decline in agroecosystems. Arthropods are key organisms that are linked to many ecosystem functions and sustainability of agriculture. Using 37 vineyards in Southern France as a model system, we analysed which characteristics of spontaneous inter-row vegetation positively influence beneficial arthropods and pest insect predation. We specifically studied the effects of flower cover, grass cover, the ratio of perennials to annuals, plant species richness and extrafloral nectar on beneficial arthropod communities in vineyards. We used direct observation and net hunting to evaluate arthropod abundance. Sentinel cards with Lucilia sp. larvae were placed on grapevine plants to analyse caterpillar predation. We found that most groups of tested beneficial arthropods were positively influenced by flower cover and plant species richness. In particular, the abundance of predators such as ladybirds (adults and larvae) and crab spiders and the abundance of parasitic wasps were positively correlated to flower cover in vineyard inter-row vegetation. The abundance of ladybirds, hoverflies and crab spiders was also positively related to plant species richness. Our results demonstrated the importance of floral resources and plant diversity for beneficial arthropods and caterpillar predation confirming their key role in biological control of pest insects.

Apparent niche differences between native and exotic lady beetles

Generalist predators can enhance biological control by filling unique niches and complementing other natural enemies, or disrupt it by preying upon other predators and parasitoids, complicating their net value for biological control. We searched for evidence of complementarity and/or interference between native (primarily Eriopis chilensis and E. eschscholtzi) and exotic (primarily Hippodamia variegata and Harmonia axyridis) lady beetles attacking aphids in alfalfa (Medicago sativa) fields near Santiago, Chile. Across 60 fields and three growing seasons, exotic lady beetle adults and larvae reached peak abundance relatively earlier in the growing season than the natives. Furthermore, exotic lady beetle peaks aligned more closely with aphid peak abundance than did native lady beetle peaks. Abundances of native lady beetle adults and larvae were weakly positively correlated with those of exotics, and peak aphid densities were generally lowest in fields where native and non-native lady beetle adults were similarly abundant. Therefore, we did not see evidence of strong interference between exotics and natives. Natural-agricultural habitat edges reduced native, but not exotic, larval lady beetle lag behind aphid peaks and was associated with greater lady beetle and lower aphid densities. Moreover, farms embedded in landscapes with greater natural habitat cover supported more exotic, but not native, lady beetles, and increased the lag between larval lady beetles and aphids for natives but not exotics. These findings support the idea that farms embedded within mosaics of natural and agricultural habitats may provide greater interaction potential between native lady beetles and aphid pests on farms as they move across the landscape, leading to greater top-down control. In contrast, exotic lady beetle lags were unaffected by landscape composition or configuration, but their greater densities in farms surrounded by more natural habitats might reflect a 'concentration effect' whereby exotic lady beetle abundance becomes concentrated in the agricultural habitats that they prefer. Our findings suggest that some lady beetles introduced for biocontrol may be better adapted to intensively managed habitats than natives, possibly leading to spatiotemporal complementarity between native and exotic lady beetles.

The Biology and Ecology of Parasitoid Wasps of Predatory Arthropods.

Parasitoid wasps are important components of insect food chains and have played a central role in biological control programs for over a century. Although the vast majority of parasitoids exploit insect herbivores as hosts, others parasitize predatory insects and arthropods, such as ladybird beetles, hoverflies, lacewings, ground beetles, and spiders, or are hyperparasitoids. Much of the research on the biology and ecology of parasitoids of predators has focused on ladybird beetles, whose parasitoids may interfere with the control of insect pests like aphids by reducing ladybird abundance. Alternatively, parasitoids of the invasive ladybird Harmonia axyridis may reduce its harmful impact on native ladybird populations. Different life stages of predatory insects and spiders are susceptible to parasitism to different degrees. Many parasitoids of predators exhibit intricate physiological interrelationships with their hosts, adaptively manipulating host behavior, biology, and ecology in ways that increase parasitoid survival and fitness.

A roadmap for ladybird conservation and recovery.

Ladybirds (Coleoptera: Coccinellidae) provide services that are critical to food production, and they fulfill an ecological role as a food source for predators. The richness, abundance, and distribution of ladybirds, however, are compromised by many anthropogenic threats. Meanwhile, a lack of knowledge of the conservation status of most species and the factors driving their population dynamics hinders the development and implementation of conservation strategies for ladybirds. We conducted a review of the literature on the ecology, diversity, and conservation of ladybirds to identify their key ecological threats. Ladybird populations are most affected by climate factors, landscape composition, and biological invasions. We suggest mitigating actions for ladybird conservation and recovery. Short-term actions include citizen science programs and education, protective measures for habitat recovery and threatened species, prevention of the introduction of non-native species, and the maintenance and restoration of natural areas and landscape heterogeneity. Mid-term actions involve the analysis of data from monitoring programs and insect collections to disentangle the effect of different threats to ladybird populations, understand habitat use by taxa on which there is limited knowledge, and quantify temporal trends of abundance, diversity, and biomass along a management-intensity gradient. Long-term actions include the development of a worldwide monitoring program based on standardized sampling to fill data gaps, increase explanatory power, streamline analyses, and facilitate global collaborations.

At Which Spatial Scale Does Crop Diversity Enhance Natural Enemy Populations and Pest Control? An Experiment in a Mosaic Cropping System

The importance of plant richness to enhance the presence, biodiversity and efficiency of natural enemies in agricultural systems has largely been studied and demonstrated these last decades. Planting and preserving non-crop plants or manipulating crop richness in fields are practices that have proven their efficiency. However, the impact of crop-richness continuity in space and time on pests and natural enemies at a landscape scale remains poorly studied. In a two-year study, we assessed the effect of crop richness (single crop vs. multiple crops) on pest and natural enemy abundance and spillover in a field experiment in north-east China. Overall, we found crop diversity had a limited impact on pest and natural enemy abundance at the spatial scale tested (0.025 vs. 0.2 ha). The total pest and natural enemy abundances were not different between single-crop and multi-crop plots in either year, and the community composition at the functional group level was mostly determined by the crop but not crop diversity. However, we found that crop diversity influenced the numeric response of ladybirds to aphids in wheat; their negative response (higher abundance where aphid abundance was lower, suggesting predation) was attenuated in multi-crop plots (no correlation of aphid and ladybird abundance, suggesting the use of alternative resources). This pattern was not found in maize. Finally, crop succession enhanced the spillover of ladybirds from wheat and maize to cotton plots but with limited benefits for aphid control. Because of these limited impacts, we hypothesized that crop diversity may benefit natural enemy populations and enhance pest control at larger spatial scales; while we found similar abundances of ladybirds between our small (0.025–0.2 ha) plots and in large (2 ha) close-by cotton fields, aphid abundances were more than ten times higher in large cotton fields. Our study highlights the need to accurately estimate the spatial scale at which crop biodiversity may benefit pest control, in relation to the ecology of the target pest and natural enemies.

A multi-site experiment to test biocontrol effects of wildflower strips in different French climate zones

Sowing of wildflower strips has been integrated in agri-environment schemes of several European countries. Their beneficial effects on natural enemies of pest insects are well documented but (1) the desired spill-over into crop fields has not always been demonstrated, and (2) the need to adapt sown mixtures to regional climatic differences has been rarely addressed.We set up a multi-site experiment in different French climatic regions to compare effects of a wildflower strip with a grass mixture and spontaneous vegetation. The design included five regions, three to five fields per region and the three strip treatments being repeated in each field. We tested strip treatment effects on vegetation (plant species richness, plant and flower cover) and on natural enemies (hoverflies, ladybirds, aphid predation). In a subset, we further analysed the spill-over into winter wheat fields including natural enemies and pest insects (cereal aphids, leaf beetles).The wildflower strip mixture developed well in all regions and increased plant species richness and flower cover compared with grass strips and spontaneous vegetation. We found a corresponding higher hoverfly abundance and aphid predation in wildflower strips that were consistent in all regions, whereas ladybird abundance was not affected. A significantly higher hoverfly abundance, aphid predation and aphid parasitism in wheat fields close to wildflower strips indicated a spill-over. No corresponding margin treatment effects were observed for aphid and leaf beetle abundance in the field. A multivariate analysis comparing the influence of climate and vegetation parameters showed that floral cover better explained variation in natural enemy abundance and predation than climate. Our results demonstrated that similar mixtures of native plants can be used over large climatic gradients to improve biocontrol. Further research is needed to improve spill-over into crop fields and to obtain consistently strong effects in different climate zones.

An updated checklist to the biodiversity data of ladybeetles (Coleoptera: Coccinellidae) of the Azores Archipelago (Portugal).

BackgroundA recently-published review from 2021 presents a comprehensive checklist of ladybeetles of Portugal, including the Azores and Madeira Archipelagos. Until then, the available information was very scattered and based on a single revision dating back to 1986, a few international catalogues and databases, individual records and studies on communities of agroecosystems. However, no information was available on faunal composition across the Azorean islands and their habitats, using standardised inventories. Here, we present data about the biodiversity of ladybeetles and their distribution and abundance in five Islands of the Azores (Faial, Graciosa, Pico, São Jorge and São Miguel). Surveys included herbaceous and arboreal habitats from native to anthropogenic-managed habitats: ruderal road vegetation, vegetable garden, mixed forest of endemic and non-native host plants, coastal prairies, coastal mixed vegetation, cornfields and urban areas. We aimed to contribute to the ongoing effort to document the terrestrial biodiversity of Portugal, including the Archipelago of the Azores, within the research project AZORESBIOPORTAL–PORBIOTA (ACORES-01-0145-FEDER-000072).New informationIn this study, a total of 1,487 specimens of Coccinellidae belonging to 19 species are reported for several habitats. The listed species are from one single sub-familiy (Coccinellinae) and six tribes; Chilocorini (one species), Coccidulini (three species), Coccinellini (six species), Noviini (one species), Scymnini (seven species), Stethorini (one species). The number of species collected per island differed; Faial (10 species), Graciosa (four species), Pico (seven species), São Jorge (seven species) and São Miguel (12 species). For six species, new island records are given. Currently, the number of species known to occur in the Azores are 32, including two doubtful records. The majority of species are Scymnini, being Scymnus (Scymnus) interruptus (Goeze, 1777) and Scymnus (Scymnus) nubilus Mulsant, 1850, the most abundant species (relative abundance 71.1%). This database will be the baseline of a long-term monitoring project allowing assessment of the impact of ongoing global changes in the distribution and abundance of ladybeetles.

Effects of Aphid Density and Plant Taxa on Predatory Ladybeetle Abundance at Field and Landscape Scales.

Simple SummaryIn agroecosystems, predatory ladybeetles play an important role in suppressing aphid populations. How ladybeetles make use of host plant diversity in multicropping landscapes has rarely been documented in China. In this study, we examined the relationship between aphid densities and ladybeetle densities at both the local field and landscape scales. Overall, we found that there was a positive correlation between aphid densities and ladybeetle densities. However, plant taxa had no significant influence on predatory ladybeetle abundance at the local field scale. In addition, the effect of aphids on ladybeetles abundance was influenced by the crop type and growing season at the regional landscape scale. There was a significant positive correlation between aphid and ladybeetle populations on cotton only in July and August, whereas the correlation was significant for maize throughout the whole growing season. The δ13C value indicated that most prey aphids for ladybeetles originated from crops where aphids are abundant (cotton in June and July; both maize and cotton in August). These findings improved our understanding of the migration and dispersal of ladybeetles among different habitats and plant species and provided insight into the promotion of regional conservation and pest control of natural enemies in Northern China.In agroecosystems, predatory ladybeetles play an important role in restraining aphid population growth and suppressing aphid populations. They can adapt to various habitats and make use of various aphid species associated with multiple host plants during their life cycle. Agricultural landscapes in China are composed of a mosaic of small fields with a diverse range of crops, and how ladybeetles make use of host plant diversity in such landscapes has rarely been documented. In this study, we examined the relationship between aphid densities and ladybeetle densities in two different settings: (i) on the majority of plant species (including crops, trees, and weeds) at a local field scale in 2013 and 2014, and (ii) in paired cotton and maize crop fields at a regional landscape scale in 2013. Overall, we found that aphid abundance determined predatory ladybeetle abundance at both the local field and landscape scales, and there was a positive correlation between aphid densities and ladybeetle densities. However, plant taxa had no significant influence on the predatory ladybeetle abundance at the local field scale. In addition, the effect of aphids on ladybeetles abundance was influenced by the crop type and growing season at the regional landscape scale. There was a significant positive correlation between aphids and ladybeetles populations on cotton only in July and August, whereas the correlation was significant for maize throughout the whole growing season. We also conducted an analysis of the stable carbon isotope ratios of the adult ladybeetles caught in cotton and maize fields (C3 and C4 crops, respectively) in a regional landscape-scale survey in 2013. The δ13Cvalue indicated that most prey aphids for ladybeetles originated from crops where aphids are abundant (cotton in June and July; both maize and cotton in August).These findings improved our understanding of the migration and dispersal of ladybeetles among different habitats and plant species and provided insight into the promotion of the regional conservation and pest control of natural enemies in northern China.

Landscape Context Influences the Abundance and Richness of Native Lady Beetles Occupying Urban Vacant Land

Urban insect communities are structured by hierarchical filters including regional processes, human facilitation, and species interactions. We sought to inform future urban conservation endeavors by identifying how landscape composition and configuration as well as the management of vacant lot greenspaces affect native lady beetle (Coccinellidae) community structure within the city of Cleveland, Ohio, USA. We found no effect of habitat treatment on native lady beetle abundance when comparing vacant lots seeded with native wildflowers and those with naturally occurring weedy vegetation mown monthly or annually. Nonetheless, establishing conservation plantings that vary in plant height, biomass, and bloom abundance could aid in supporting a greater richness of coccinellid species, as these variables had differential effects on the abundance of fungivorous and aphidophagous feeding guilds. Further, we found that vacant lots embedded within landscapes with increased impervious surface and a high degree of greenspace isolation contained fewer aphidophagous native and exotic lady beetles. Our findings suggest that landscape context is a critical consideration when aiming to utilize vacant land as conservation habitat for coccinellids. Given their large holdings of vacant land, shrinking cities offer a unique opportunity to incorporate landscape-scale planning into future sustainable development initiatives. For instance, with over 27,000 vacant lots, the city of Cleveland could aid lady beetle conservation by electing to maintain vacant lots that promote greenspace connectivity while targeting isolated lots within intact neighborhoods for new residential development.

Whorl-stage maize provides a microclimate refuge for predatory ladybeetles

Ladybeetles are voracious predators and contribute to the in-field suppression of herbivorous pests, yet are especially vulnerable to variable climatic conditions. In this study, we surveyed the temporal dynamics of ladybeetles on maize plants (Zea mays L.) at different phenological stages within experimental plots (2010–2014) and commercial fields (2013–2014). Ladybeetle adults attained high abundance on whorl-stage maize, despite a relative scarcity of prey items (e.g., aphids, insect eggs). Field work in 2015 further revealed how ladybeetle abundance on whorl-stage maize was higher than on adjacent cotton plants – with > 88% of ladybeetle adults occurring within the maize whorl. Whorl-inhabiting adults were the most abundant at 12:00, when air temperature was the highest; abundance levels dropped at 6:00, 18:00 and 24:00 with declining ambient temperature. Within maize whorls, average temperature was 3.9 °C lower and presence of free water 50.1% higher than under ambient conditions. Hence, whorl-stage maize plants offer suitable micro-climatic conditions for foraging ladybeetles and could act as a refuge during seasonally hot or dry conditions in agro-ecosystems. Our work offers novel information on how crop diversification (i.e., addition of maize strips) can benefit in-field abundance and activity patterns of ladybeetles, and thereby eventually promote conservation biological control in agro-ecosystems of northern China.

Impacts of weed management on ladybird (Coleoptera: Coccinellidae) abundance and diversity on resident vegetation in a citrus orchard

Citrus fruits are markedly affected by aphids on the island of Réunion (France). These pests are generally controlled with pesticides, which have adverse effects on human and environmental health. Furthermore, resident vegetation in orchards is often eliminated with herbicides due to suspected competition with citrus trees for resources. Yet this resident vegetation could serve as a habitat for natural enemies of crop pests, particularly ladybirds (Coleoptera: Coccinellidae), which are well-known aphid predators, thus reducing the need for pesticide treatments. Results of a 2-year study conducted in an experimental citrus orchard, on the impacts of four different weed management treatments on ladybird populations, viz: i) M: hedge-trimmer mowing; ii) T: disk harrow tilling; iii) HM: hammer mill crushing/mulching; iv) H: herbicide spraying are presented. Ladybirds were captured over a 5 week period each year using Malaise-derived flight interception traps. A total of 690 ladybird specimens, belonging to 12 species distributed across four subfamilies, were captured. These were mainly aphidophagous, with Scymnus constrictus Mulsant being largely dominant. There was a significant effect of distance to a field border with diversified vegetation on ladybird abundance and diversity. Ladybirds were also significantly more abundant on tall vegetation cover than on short cover. Although proportionately fewer ladybirds were trapped in the ‘H’ treatment than in the other three, there were no clearcut effects of weed management treatments on ladybird abundance. This study nevertheless confirmed the efficacy of interception traps for assessment of ladybird population abundance and diversity. It also demonstrated the potential of these natural enemies as bioindicators of habitat disturbance.

Adjacent habitat type affects the movement of predators suppressing soybean aphids.

Landscape complexity influences soybean aphid suppression by generalist predators in North America, but the role of adjacent habitats as sources of these predators has not been studied directly. We quantified movement of aphidophagous predators between soybean and five adjacent habitats common in Manitoba using bi-directional Malaise traps. To test the contribution of predators from neighboring habitats to soybean aphid suppression, we performed experimental manipulations in adjacent soybean and alfalfa fields and monitored the movement of sevenspotted lady beetles, Coccinella septempunctata, using mark-release-recapture experiments. The identity of adjacent habitats affected the net movement of predators into soybean. The most abundant predators were hover flies (Diptera: Syrphidae), moving from woodlands to soybean. Similar (but non-significant) trends were found for lady beetles, minute pirate bugs, and green and brown lacewings. There was also a net movement of hover flies and green lacewings from soybean to canola. Lady beetles showed higher bidirectional movement in alfalfa and wheat borders than in woodland and canola borders in a high lady beetle abundance year. Soybean aphid populations in predator exclusion cages were 21- to 122- fold higher than populations exposed to predators, both in alfalfa and soybean fields. Aerial predators provide similar levels of aphid suppression as aerial and epigeal predators combined. Mark-release-recapture experiments showed high dispersal of C. septempunctata between soybean and alfalfa, with a net movement towards alfalfa, probably due to the lack of aphids in soybean. These results demonstrate that predator assemblages from both soybeans and alfalfa can suppress soybean aphids. Our findings indicate that the type of adjacent habitat and predator identity affect the directionality of predator movement into soybean. This study suggests that information on predator movement can be used to design the distribution of crops and natural habitats in agricultural landscapes that maximize pest control services.

Non-crop habitats promote the abundance of predatory ladybeetles in maize fields in the agricultural landscape of northern China

Ladybeetles are promising contributors of biological control services in agricultural landscapes, potentially providing significant economic gains in agricultural production. In northern China, ladybeetles are the most common predators in the annual double-crop rotation system, where the dominant crops are wheat in the spring and maize and cotton in the summer. Land-use features at the landscape level affect ladybeetle populations in a number of ways, and our previous studies have estimated the effects of landscape composition on ladybeetles abundance in wheat and cotton fields in northern China. However, these landscape effects on ladybeetle abundance in maize remain insufficiently documented in this specific agro-ecosystem. We assessed the relationships between ladybeetle abundance and landscape composition at four spatial scales (0.5, 1.0, 1.5, and 2.0 km) in a summer maize system at the whorl stage (the main period for ladybeetle colonization). We found that both semi-natural habitats (woodlots and grasslands) and vegetation around water bodies increased the abundance of ladybeetles in maize fields, and maize area played a dilution effect on ladybeetle abundance in this crop. These non-crop habitats might serve as source of emigrants that disperse to maize fields. The smallest scale (0.5 km) studied was the most predictive spatial scale in this colonization period for ladybeetles. Propylaea japonica, the dominant ladybeetle, showed response to landscape variables in a similar way as the whole ladybeetle population did. These findings suggest that leaving some non-crop habitats and reducing human disturbance to this vegetation within a landscape will enhance ladybeetle abundance in maize fields. Consistent with our previous studies in wheat and cotton fields in the same system, maintaining the continuity in time and space of functional habitats was essential for the persistence of ladybeetle populations within the landscape. In the future, habitat management and landscape design to ensure resource continuity should be encouraged to maximize the conservation of ladybeetles in agricultural ecosystems in northern China.

Stability of native and exotic lady beetle populations in a diverse landscape

AbstractThe stability of populations is a central, yet challenging concept in ecology. Here, we examine the stability of annual abundance for populations of nine native and four exotic lady beetle species (Coccinellidae) in a mixed landscape in Michigan, USA, over 23 yr. The species have similar life histories, live together in the same habitats, and have been disturbed by the sequential introduction of exotic lady beetle species. The publicly available dataset was collected in a diverse landscape of three forest habitats, four annual crop habitats with different intensities of management, and three perennial crops. Replicated 1‐ha plots were sampled weekly with yellow sticky cards during the summer season for each habitat, three plots for each of the three forest types and six plots for each of the seven crop habitats. We quantified stability for each species and each species by habitat combination, using three parameters: trends in abundance, persistence, and temporal population variability. The most abundant lady beetle species were more stable than the uncommon and rare species. Habitat generalists had more stable population dynamics than specialists, but habitat breadth was confounded with lady beetle abundance. Exotic and native species with similar abundances had similar levels of stability. Exotic species disrupted the native populations, leading to declines in abundance for eight of nine species and increased population variability for the native species. The abundances of exotic lady beetles rose quickly to the long‐term mean. Our findings support the hypothesis that populations exhibit species‐specific levels of stability, not greatly affected by stochastic variations in environmental conditions or by habitat characteristics. We also show that exotic species can decrease the stability as well as the abundance of native species in a community of lady beetles.

Mixed effects of landscape complexity and insecticide use on ladybeetle abundance in wheat fields

Although the abundance of insect natural enemies in crop fields may be influenced by the surrounding landscape and local field management, particularly insecticide use at the local scale, few studies have examined these factors simultaneously. In this study, we investigated the effects of landscape context and insecticide use in local fields on ladybeetle abundance in wheat fields in northern China. Woodlots and fallow land were the most important landscape variables enhancing ladybeetle abundance. We used the cumulative percentage of these land types to characterize landscape complexity. Comparing the change in ladybeetle abundance in wheat fields within different landscapes and with different in-field insecticide regimes, we found that although more complex landscapes enhanced ladybeetle abundance, the negative effects of insecticide use on ladybeetle populations were not offset by landscape complexity. Additionally, the positive effects of more complex landscapes on ladybeetle abundance were not significant in wheat fields subjected to high insecticide use. Ladybeetle abundance is enhanced by landscape complexity, but this is modified by insecticide use in local fields. Within-field efforts to maximize the conservation biological control of pests to improve crop yield should take into account the influence of the surrounding landscape. © 2018 Society of Chemical Industry.

Predatory Lady Beetles (Coleoptera, Coccinellidae) in Cereal Agrocenoses in the Northern Forest-Steppe of West Siberia and the Influence of Agrotechnical Methods on Them

Predatory lady beetles (Coccinellidae) form one of the prevalent and effective groups of entomophages in the forest-steppe zone of West Siberia. Among 17 species of predatory lady beetles recorded in cereal agrocenoses and on bird cherry trees, Propylea quatuordecimpunctata, Coccinella septempunctata, Hippodamia tredecimpunctata, H. variegata, and H. arctica are predominant. This paper presents data on the species composition and ecological features of lady beetles in agrocenoses of winter rye, spring wheat, and oats as well as on the impact of agrotechnical methods (the main treatment of soil, application of chemicals, and forecrops) and cultivation technology on the abundance of lady beetles.

Influence of the margin vegetation on the conservation of aphid biological control in apple orchards

The influence of three margin strip treatments (wildflower strips, grass strips and spontaneous vegetation) adjacent to apple orchards on the biological control of Dysaphis plantaginea Passerini (Hemiptera: Aphididae) was compared during two consecutive years. The wildflower strips provided the highest amount of floral resources. Within the margin strips, hoverflies responded positively to higher resource provisioning whereas ladybird abundance did not differ between strip treatments. Within the orchards, the presence of parasitoids, hoverflies, and ladybirds in aphid colonies and the predation of sentinel aphids were not significantly affected by the adjacent strip treatments. The number of natural enemies observed in aphid colonies was mainly driven by aphid number. Aphid numbers were higher close to the margin strips suggesting that aphid colonization from orchard edges may counteract the positive effect of wildflower strips on natural enemy abundance and on a reduction of aphid infestation. The results confirm the positive influence of floral resource provisioning by wildflower strips on the conservation of aphid natural enemies, but also suggest that effects of wildflower strips on aphid regulation inside orchards are not very strong compared with spontaneous vegetation naturally occurring in the margins.