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In this paper, we revisit a predator-prey model with specialist and generalist predators proposed by Hanski et al. (J Anim Ecol 60:353-367, 1991) , where the density of generalist predators is assumed to be a constant. It is shown that the model admits a nilpotent cusp of codimension 4 or a nilpotent focus of codimension 3 for different parameter values. As the parameters vary, the model can undergo cusp type (or focus type) degenerate Bogdanov-Takens bifurcations of codimension 4 (or 3). Our results indicate that generalist predation can induce more complex dynamical behaviors and bifurcation phenomena, such as three small-amplitude limit cycles enclosing one equilibrium, one or two large-amplitude limit cycles enclosing one or three equilibria, three limit cycles appearing in a Hopf bifurcation of codimension 3 and dying in a homoclinic bifurcation of codimension 3. In addition, we show that generalist predation stabilizes the limit cycle driven by specialist predators to a stable equilibrium, which clearly explains the famous Fennoscandia phenomenon.
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Modelos Biológicos , Conducta Predatoria , Animales , Cadena Alimentaria , Dinámica PoblacionalRESUMEN
This paper deals with a system of reaction-diffusion-advection equations for a generalist predator-prey model in open advective environments, subject to an unidirectional flow. In contrast to the specialist predator-prey model, the dynamics of this system is more complex. It turns out that there exist some critical advection rates and predation rates, which classify the global dynamics of the generalist predator-prey system into three or four scenarios: (1) coexistence; (2) persistence of prey only; (3) persistence of predators only; and (4) extinction of both species. Moreover, the results reveal significant differences between the specialist predator-prey system and the generalist predator-prey system, including the evolution of the critical predation rates with respect to the ratio of the flow speeds; the take-over of the generalist predator; and the reduction in parameter range for the persistence of prey species alone. These findings may have important biological implications on the invasion of generalist predators in open advective environments.
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Conducta Predatoria , AnimalesRESUMEN
The performance (development and reproduction) of generalist predators can vary greatly among the prey species that they use, and these differences can influence the ability of predatory insects to suppress pest populations. The aim of this study was to compare the performance of larvae of the green lacewing Chrysoperla rufilabris (Burmeister, 1839) by offering 16 species of aphids and by assessing the effects of each species on the survival, larval development time, prey consumption, pupal mass and egg load of adult Chr. rufilabris females taking aphid phylogeny into account. Chrysoperla rufilabris larvae preyed on individuals from all 16 aphid species, but complete development, adult emergence and egg load production were achieved only in seven species. As a general pattern, the best levels of performance were achieved for an aphid clade that includes the soybean aphid, Aphis glycines (Matsumara, 1917), and for a milkweed-feeding species, Myzocallis asclepiadis (Monell, 1879). We found significant phylogenetic clustering for most of the performance traits indicating the aspects of specialization in the diet breadth of Chr. rufilabris despite the fact that this species is considered a generalist aphid predator. These findings can help us to understand the interactions of this species in agroecological food webs, where it is commonly found, and provide insights into why natural, conservation biological control or augmentative releases may succeed or fail.
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Áfidos , Animales , Dieta , Femenino , Insectos , Larva , Control Biológico de Vectores , Filogenia , Conducta PredatoriaRESUMEN
A generalist predatory mite, Anystis baccarum (L.), was evaluated as a biological control agent against western flower thrips (WFT), Frankliniella occidentalis (Pergande). Laboratory assays showed A. baccarum was able to kill a mean of five WFT adult females or nine WFT larvae in 24 h, out-performing both Neoseiulus cucumeris (Oudemans) and Amblyseius swirskii Athias-Henriot. Next, a greenhouse assay was conducted to assess the performance of A. baccarum on potted chrysanthemums, comparing their efficacy to that provided by N. cucumeris slow-release sachets which represented the commercial standard in Canada. A combined treatment which incorporated both predatory mite species was also included to assess compatibility and potential additive effects of using both species together for WFT management. Introduction of two A. baccarum per pot was as efficacious as 125 N. cucumeris in terms of WFT control; however, despite the lack of significance between the level of WFT control obtained in the single predatory species treatments and the combined treatment, only the combination treatment suppressed WFT populations to levels that were almost unchanged over 8 weeks. There was no significant difference between the number of N. cucumeris recovered from plants in the single-species and the combination treatments, demonstrating the functional compatibility of the two predators. Additionally, WFT feeding damage was significantly lower on the A. baccarum-treated plants than on the untreated control and the N. cucumeris treatment. This study, together with our development of a prototype mass rearing method, shows that A. baccarum could be successfully used as a biocontrol agent for WFT.
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Ácaros , Thysanoptera , Animales , Femenino , Flores , Control Biológico de Vectores/métodos , Conducta PredatoriaRESUMEN
Ground beetles are natural predators of insect pests and small seeds in agroecosystems. In semiarid cropping systems of the Northern Great Plains, there is a lack of knowledge to how ground beetles are affected by diversified cover crop rotations. In a 2-yr study (2018 and 2019), our experiment was a restricted-randomization strip-plot design, comprising summer fallow, an early-season cover crop mixture (five species), and a mid-season cover crop mixture (seven species), with three cover crop termination methods (i.e., herbicide, grazing, and haying). Using pitfall traps, we sampled ground beetles in five 48-h intervals throughout the growing season (n = 135 per year) using growing degree day (GDD) accumulations to better understand changes to ground beetle communities. Data analysis included the use of linear mixed-effects models, perMANOVA, and non-metric multidimensional scaling ordinations. We did not observe differences among cover crop termination methods; however, activity density in the early-season cover crop mixture decreased and in summer fallow increased throughout the growing season, whereas the mid-season cover crop mixture peaked in the middle of the summer. Ground beetle richness and evenness showed a nonlinear tendency, peaking in the middle of the growing season, with marginal differences between cover crops or fallow after the termination events. Also, differences in ground beetle composition were greatest in the early- and mid-season cover crop mixtures earlier in the growing season. Our study supports the use of cover crop mixtures to enhance ground beetle communities, with potential implications for pest management in dryland cropping systems.
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Biota , Escarabajos , Producción de Cultivos/métodos , Animales , Productos Agrícolas/crecimiento & desarrollo , MontanaRESUMEN
Ecosystems often contain multiple species across two or more trophic levels, with a variety of interactions possible. In this paper we study two classes of models for generalist predators that utilize more than one food source. These models fall into two categories: predator - two prey and predator - prey - subsidy models. For the former, we consider a generalist predator which utilizes two distinct prey species, modelled via a Kolmogorov system of equations with Type II response functions. For the latter, we consider a generalist predator which exploits both a prey population and an allochthonous resource which is provided as a subsidy to the system exogenously, again with Type II response functions. This latter class of model is no longer Kolmogorov in form, due to an exogenous forcing term modelling the input of the allochthonous resource into the system. We non-dimensionalize both models, so that their respective parameter spaces may be more easily compared, and study the dynamics possible from each type of model, which will then indicate - for specific parameter regimes - which generalist predator's preferences are more favorable to survival, including the prevalence of coexistence states. We also consider the various non-equilibrium dynamics emergent from such models, and show that the non-Kolmogorov predator - prey - subsidy model of 10 admits more regular dynamics (including steady states and one type of limit cycle), whereas the predator - two prey Kolmogorov model can feature multiple types of limit cycles, as well as multistability resulting in strong sensitivity to initial conditions (with stable limit cycles and steady states both coexisting for the same model parameters). Our results highlight several interesting differences and similarities between Kolmogorov and non-Kolmogorov models for generalist predators.
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Cadena Alimentaria , Conducta Predatoria , Animales , Ecosistema , Modelos Biológicos , Dinámica PoblacionalRESUMEN
Predators and prey often differ in body mass. The ratio of predator to prey body mass influences the predator's functional response (how consumption varies with prey density), and therefore, the strength and stability of the predator-prey interaction. The persistence of food chains is maximized when prey species are neither too big nor too small relative to their predator. Nonetheless, we do not know if (i) food web persistence requires that all predator-prey body mass ratios are intermediate, nor (ii) if this constraint depends on prey diversity. We experimentally quantified the functional response for a single predator consuming prey species of different body masses. We used the resultant allometric functional response to parametrize a food web model. We found that predator persistence was maximized when the minimum prey size in the community was intermediate, but as prey diversity increased, the minimum body size could take a broader range of values. This last result occurs because of Jensen's inequality: the average handling time for multiple prey of different sizes is higher than the handling time of the average sized prey. Our results demonstrate that prey diversity mediates how differences between predators and prey in body mass determine food web stability.
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Cadena Alimentaria , Insectos/fisiología , Conducta Predatoria , Animales , Tamaño Corporal , Escarabajos/fisiología , Dípteros/fisiología , Modelos Biológicos , Odonata/fisiología , Oligoquetos/fisiologíaRESUMEN
We consider hybrid spatial modeling approaches for ecological systems with a generalist predator utilizing a prey and either a second prey or an allochthonous resource. While spatial dispersion of populations is often modeled via stepping-stone (discrete spatial patches) or continuum (one connected spatial domain) formulations, we shall be interested in hybrid approaches which we use to reduce the dimension of certain components of the spatial domain, obtaining either a continuum model of varying spatial dimensions, or a mixed stepping-stone-continuum model. This approach results in models consisting of partial differential equations for some of the species which are coupled via reactive boundary conditions to lower dimensional partial differential equations or ordinary differential equations for the other species. In order to demonstrate the use of this approach, we consider two case studies. In the first case study, we consider a one-predator two-prey interaction between beavers, wolves and white-tailed deer in Voyageurs National Park. In the second case study, we consider predator-prey-allochthonous resource interactions between bears, berries and salmon on Kodiak Island. For each case study, we compare the results from the hybrid modeling approach with corresponding stepping-stone and continuum model results, highlighting benefits and limitations of the method. In some cases, we find that the hybrid modeling approach allows for solutions which are easier to simulate (akin to stepping-stone models) while maintaining seemingly more realistic spatial dynamics (akin to full continuum models).
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Ecosistema , Modelos Biológicos , Dinámica Poblacional , Conducta Predatoria , Animales , Ciervos , Cadena Alimentaria , Frutas , Salmón , Ursidae , LobosRESUMEN
In Focus: Hunter, M. D., & Kozlov, M. V. (2019) The relative strengths of rapid and delayed density-dependence acting on a terrestrial herbivore change along a pollution gradient. Journal of Animal Ecology, 88, 665-676. Teasing apart the interactions between biotic and abiotic factors affecting animal population dynamics is a difficult task when based solely on the analysis of natural populations. Experimental manipulations of systems using microcosm studies can be powerful tools for probing such interactions, but microcosms are ultimately limited by their lack of complexity compared with nature. Hunter and Kozlov (2019) take a novel field-based experimental approach to studying abiotic influences on biotic interactions by quantifying how the presence of a pollutant source alters biotic processes driving populations of a forest leaf miner. They find that populations in proximity to a pollutant source show weaker direct density dependence and stronger delayed density dependence than more distant populations unaffected by pollution. These differences in density dependence cause higher equilibrium densities near the pollution source but surprisingly they do not alter leaf miner oscillatory dynamics. This creative study provides useful insight into how abiotic forces alter biotic population processes and how density dependence shapes the spatial dynamics of animal populations.
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Contaminación del Aire , Animales , Ecología , Bosques , Insectos , Densidad de Población , Dinámica PoblacionalRESUMEN
The flower bug Orius sauteri is a generalist predator that occurs throughout Japan, and is a promising indigenous natural enemy for micro-pests such as thrips, aphids, and spider mites. We aimed to manipulate the attraction, dispersal, and settlement behavior of Orius bugs using natural chemical substances emitted by the bugs themselves. To identify potential candidates, we screened components in the whole-body extract of O. sauteri based on antennal response and then determined their chemical structure. A gas chromatograph electroantennographic detector (GC/EAD) indicated that the antennae of males responded to two components in the extract of females. GC/mass spectrometry (MS) showed that these two components were octenal and octadienal. Derivatization or GC-FT-IR analysis identified these components as (E)-2-octenal and (E)-2,7-octadienal. To assess the effect of these components on O. sauteri behavior, we conducted two assays. A field bioassay demonstrated that a blend of the two components functioned as a sex pheromone, and a dispersal assay showed that (E)-2-octenal generated a dose-dependent dispersal response. Our study will provide baseline information for enhancing the retention of O. sauteri on important commercial crops to prey on pest species.
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Heterópteros/fisiología , Atractivos Sexuales/análisis , Aldehídos/análisis , Aldehídos/aislamiento & purificación , Aldehídos/farmacología , Animales , Conducta Animal/efectos de los fármacos , Femenino , Cromatografía de Gases y Espectrometría de Masas , Heterópteros/química , Masculino , Atractivos Sexuales/aislamiento & purificación , Atractivos Sexuales/farmacología , Espectroscopía Infrarroja por Transformada de FourierRESUMEN
The behavioral response of a generalist phytoseiid predator, Cydnoseius negevi (Swirskii & Amitai) (Acari: Phytoseiidae) to the complicated webbing of the date palm mite (DPM) Oligonychus afrasiaticus (McGregor) (Acari: Tetranychidae) was evaluated for the first time on date palm leaves and fruits, both in the laboratory and on field-collected samples. Cydnoseius negevi used its first pair of legs in a swimming-like to-and-fro movement to penetrate the complicated webbing of DPM and demonstrated three attack behaviors, i.e., patrolling (PG), web invasion (WI), and web penetration (WP), against the webbing of DPM on date fruits and leaves. The time spent by the predator on attack behaviors was significantly longer in the laboratory for treatments where either more prey females or immature stages along with females were present. The time spent by C. negevi on response behaviors such as searching, grooming, and resting increased with increased number of DPM females and with the addition of immature stages along with DPM females. Cydnoseius negevi, even though being a generalist phytoseiid predator, showed its potential towards penetrating the complex dense webs of DPM on date palm fruits and leaves. If released in suitable numbers prior to establishment of DPM colonies, C. negevi may prove to be an effective biological control agent.
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Acaridae/fisiología , Conducta Animal , Phoeniceae , Acaridae/crecimiento & desarrollo , Animales , Femenino , Masculino , Conducta PredatoriaRESUMEN
Analytical modeling of predator-prey systems has shown that specialist natural enemies can slow, stop and even reverse pest invasions, assuming that the prey population displays a strong Allee effect in its growth. We aimed to formalize the conditions in which spatial biological control can be achieved by generalists, through an analytical approach based on reaction-diffusion equations. Using comparison principles, we obtain sufficient conditions for control and for invasion, based on scalar bistable partial differential equations. The ability of generalist predators to control prey populations with logistic growth lies in the bistable dynamics of the coupled system, rather than in the bistability of prey-only dynamics as observed for specialist predators attacking prey populations displaying Allee effects. As a consequence, prey control is predicted to be possible when space is considered in additional situations other than those identified without considering space. The reverse situation is also possible. None of these considerations apply to spatial predator-prey systems with specialist natural enemies.
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Especies Introducidas , Modelos Biológicos , Conducta Predatoria , Animales , Control de Plagas , Dinámica PoblacionalRESUMEN
The seven-spot ladybird beetle, Coccinella septempunctata, is a major natural enemy of aphids in the field and in greenhouses in China and is part of integrated pest management (IPM). Imidacloprid, a highly efficient insecticide that not only kills aphids at lethal concentrations, but also can cause various sublethal effects in nontarget organisms. To strengthen IPM and its sustainability, it is important assessing possible side effects on natural enemies. When the effects of sublethal concentrations (LC5 and 10%LC5) of imidacloprid on C. septempunctata were evaluated, the adult longevity was shortened by 23.97 and 28.68 %, and the fecundity reduced by 52.81 and 56.09 % compared to control population. In the F1 generation (i.e., the progeny of the exposed individuals), the juvenile development was slower by 1.44 days and 0.66 days, and the oviposition period was shortened by 10 and 13 days, respectively. The fecundity of the F1 generation decreased by 17.88, 44.03 and 51.69 % when exposed to 1%LC5, 10%LC5, and LC5, respectively. The results of demographical growth estimates showed that the intrinsic rate of increase (r m ) and net reproductive rate (R 0 ) were lower in C. septempunctata populations that had been exposed to sublethal concentrations of imidacloprid. The results emphasize the importance of assessing side effects of low imidacloprid concentrations on such predator species, even at the transgenerational level.
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Escarabajos/efectos de los fármacos , Imidazoles/toxicidad , Insecticidas/toxicidad , Nitrocompuestos/toxicidad , Animales , Escarabajos/fisiología , Neonicotinoides , Pruebas de Toxicidad SubagudaRESUMEN
Landscapes in nature can be viewed as a continuum of small total habitable area with high fragmentation to widely spreading habitats. The dispersal-mediated rescue effect predominates in the former landscapes, while classical density-dependent processes generally prevail in widely spread habitats. A similar principle should be applied to populations of organisms utilizing microhabitats in limited supply. To test this hypothesis, we examined the population dynamics of a web spider, Neriene brongersmai, in 16 populations with varying degrees of microhabitat availability, and we explored whether: (i) high microhabitat availability improves survival rate during density-independent movement, while the resultant high density reduces survival rate in a density-dependent manner; and (ii) temporal population stability increases with microhabitat availability at the population level. Furthermore, we conducted two types of field experiments to verify whether high microhabitat availability actually reduces mortality associated with web-site movement. Field observations revealed that demographic change in N. brongersmai populations was affected by three factors at different stages, namely the microhabitat limitation from the early to late juvenile stages, the density dependence from the late juvenile to adult stages and the food limitation from the adult to the next early juvenile stages. In addition, there was a tendency for a positive association between population stability and microhabitat availability at the population level. A small-scale experiment, where the frequency of spider web relocation was equalized artificially, revealed that high microhabitat availability elevated the survival rate during a movement event between web-sites. The larger spatiotemporal scale experiment also revealed an improved spider survival rate following treatment with high microhabitat availability, even though spider density was kept at a relatively low level. The population dynamics of N. brongersmai can be determined primarily by density-independent processes based on web-site fragmentation and density-dependent processes driven by interference competition. We conclude that depending on the amount of habitat resources, the relative importance of the two contrasting paradigms-equilibrium and non-equilibrium-appears to vary, even within a particular system.
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Distribución Animal , Ecosistema , Estadios del Ciclo de Vida , Arañas/fisiología , Animales , Femenino , Bosques , Japón , Densidad de Población , Dinámica Poblacional , Conducta PredatoriaRESUMEN
Within the framework of a food web, the foraging behavior of meso-carnivorous species is influenced by fear responses elicited by higher trophic level species, consequently diminishing the fecundity of these species. In this study, we investigate a three-species food chain model comprising of prey, an intermediate predator, and a top predator. We assume that both the birth rate and intraspecies competition of prey are impacted by fear induced by the intermediate predator. Additionally, the foraging behavior of the intermediate predator is constrained due to the presence of the top predator. It is essential to note that the top predators exhibit a generalist feeding behavior, encompassing food sources beyond the intermediate predators. The study systematically determines all feasible equilibria of the proposed model and conducts a comprehensive stability analysis of these equilibria. The investigation reveals that the system undergoes Hopf bifurcation concerning various model parameters. Notably, when other food sources significantly contribute to the growth of the top predators, the system exhibits stable behavior around the interior equilibrium. Our findings indicate that the dynamic influence of fear plays a robust role in stabilizing the system. Furthermore, a cascading effect within the system, stemming from the fear instigated by top predators, is observed and analyzed. Overall, this research sheds light on the intricate dynamics of fear-induced responses in shaping the stability and behavior of multi-species food web systems, highlighting the profound cascading effects triggered by fear mechanisms in the ecosystem.
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Ecosistema , Cadena Alimentaria , Animales , Dinámica Poblacional , Modelos Biológicos , Conducta Predatoria/fisiología , MiedoRESUMEN
The tarnished plant bug, Lygus lineolaris, is a major strawberry pest. Only marginally effective control methods exist to manage this pest. Various predators attack L. lineolaris, but their potential is overlooked. In this study, we explore the potential of two omnivorous predators of the tarnished plant bug: the damsel bug, Nabis americoferus, and the minute pirate bug, Orius insidiosus. Firstly, the predation rate of these predators was measured in laboratory tests. Secondly, their potential release rates and release periods were determined in the field using strawberry plants. The results show that N. americoferus feeds on all nymphal stages and adults of the tarnished plant bug, while O. insidiosus attacks only smaller nymphs (up to the N2 stage). In the field, all tested densities of N. americoferus (0.25, 0.5, and 0.75 individual/plant) reduced the population of the tarnished plant bug for several weeks compared with the control treatment, but the effect of O. insidiosus alone was marginal. Additionally, for all the release periods tested, Nabis americoferus was efficient in reducing the pest population. These results demonstrate the potential of N. americoferus to control the tarnished plant bug in strawberry fields. We discuss the possible application of these results for establishing an effective and economically viable biological control strategy.
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Phytoseiid predatory mites are efficient biocontrol agents of important thrips pests, such as the western flower thrips, Frankliniella occidentalis Pergande (Thysanoptera: Thripidae). Until recently, it was believed that first instars, and to a lesser extent second instars, were the most vulnerable developmental stages of thrips to be attacked by phytoseiids. However, recent evidence showed that some phytoseiids can detect and prey upon thrips eggs inserted in the leaf tissue. As phytoseiid predatory mites often co-occur with other beneficial insects, such as mirid and anthocorid predatory bugs which also insert their eggs inside leaf material, this raises the question whether phytoseiid predatory mites may also feed on predatory bug eggs. Here we first tested the potential of Amblyseius swirskii Athias-Henriot, Transeius montdorensis Schicha, and Amblydromalus limonicus Garman and McGregor (Acari: Phytoseiidae) to kill eggs of F. occidentalis in leaf tissue. Secondly, we tested whether those phytoseiids were capable of killing eggs of Orius laevigatus Fieber (Hemiptera: Anthocoridae), Macrolophus pygmaeus Rambur and Nesidiocoris tenuis (Reuter) (Hemiptera: Miridae), three biocontrol agents that also insert their eggs inside plant tissue. Our results showed that A. swirskii and A. limonicus could kill thrips eggs, whereas T. montdorensis could not. Furthermore, we show that the presence of phytoseiid predatory mites does not affect the hatch rate of predatory bugs that insert their eggs inside leaves.
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Heterópteros , Ácaros , Thysanoptera , Animales , Insectos , Control Biológico de Vectores/métodos , Conducta PredatoriaRESUMEN
A generalist predatory mite, Anystis baccarum (L.), has been identified as a key predator of small, soft-bodied pest species in various agroecosystems around the world. The foxglove aphid Aulacorthum solani (Keltenbach) is a new problematic pest in Canadian greenhouses. Laboratory colonies of A. baccarum were established and its predatory efficacy against A. solani was assessed. In laboratory trials, A. baccarum ate approximately one adult aphid or seven first instar aphids in 24 h. In a greenhouse bench trial on sweet peppers with the free-flying aphid parasitoid, Aphidius ervi Haliday, the population dynamics of A. solani in the presence or absence of A. baccarum was evaluated. Although the parasitoid alone successfully eradicated A. solani, when A. baccarum were present on the plants, the aphid population was eradicated more rapidly. Fruit yield was also 15% higher from plants where A. baccarum was released than the control (without A. baccarum). Furthermore, plants were naturally infested by Frankliniella occidentalis (Pergande) during the trial, which caused visible feeding damage to the fruits. Anystis baccarum also predates on thrips and thrips' feeding damage to the fruits was reduced on plants where A. baccarum was released. Anystis baccarum was able to establish in sweet peppers and was determined to be complementary to the current practice of using A. ervi for the biological control of A. solani.
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Increasing host plant quality affects higher trophic level predators, but whether such changes are simply a result of prey density or are also affected by changes in prey quality remain uncertain. Moreover, whether changes in prey quality affect measures of predator performance is understudied. Using a combination of field and greenhouse mesocosm experiments, we demonstrate that the survival and body size of a hunting spider (Pardosa littoralis Araneae: Lycosidae) is affected more by prey species identity than the trophic level of the prey. Furthermore, increasing host plant quality does not necessarily propagate through the food web by altering prey quality. While changes in plant quality affected spider body mass, they did so in opposite ways for spiders feeding on Prokelisia (Hemiptera: Delphacodes) herbivores relative to Tytthus (Hemiptera: Miridae) egg predators, and had no impact on spider body mass for two additional species of intraguild prey. These changes in body mass were important because greater body mass increased spider egg production. To examine the generality of this pattern, we reviewed the literature and found a consistent positive relationship between female body size and egg production for Pardosa species, indicating that body size is a reliable proxy for fitness. While many studies emphasize the importance of nitrogen to arthropod diets, this focus may be driven largely by our understanding of herbivore diets rather than predator diets. Thus, the positive impact of host plant quality on higher trophic level predators appears to be driven more by altering prey composition, density, and availability rather than simply providing predators with more nutritious prey.
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BACKGROUND: Generalist predators play a key role in the biocontrol of insect pests in agricultural systems. However, predators are subject to frequent mortality events due to periodic disturbance regimes such as crop planting and harvest, which inevitably affect the population development of predators. Conservation of predators in this critical period is important for double-cropping systems such as winter wheat and summer maize, the most widely used cropping system in North China. RESULTS: Planting Cnidium monnieri flower strips at field borders could not only serve as a bridge habitat to conserve the dominant predator Propylaea japonica in wheat fields during harvest but also help the predator immigrate to adjacent maize fields. The predator abundance was 7-fold higher on flower strips than that on natural vegetation strips during the wheat postharvest period and before the maize plant emergence for about a month, and its abundance in maize fields planted with flower strips was nearly 2-fold higher than that in maize fields planted with natural vegetation strips. Moreover, 77.56% of predators that entered maize fields were proven to originate from flower strips. CONCLUSION: Our findings provided evidence that manipulating flower strips as a bridge habitat in wheat-maize rotation fields could conserve P. japonica during crop phenophase changes, and we quantitatively testified that the proportion of this predator in maize fields derived from flower strips. In practice, such a strategy may also be applied in other double-cropping and triple-cropping systems. © 2020 Society of Chemical Industry.