Predation Efficiency Research Articles

Life Histories and Functional Responses of Two Predatory Mites Feeding on the Stored-Grain Pest Liposcelis bostrychophila Badonnel (Psocoptera: Liposcelididae)

Cheyletus malaccensis Oudemans and Cheyletus eruditus (Schrank) are predators of stored-grain pests in China. The psocid Liposcelis bostrychophila Badonnel is prone to outbreaks in depots. To assess the potential of large-scale breeding with Acarus siro Linnaeus and the biological control potential of C. malaccensis and C. eruditus against L. bostrychophila, we determined the development times of different stages at 16, 20, 24, and 28 °C and 75% relative humidity (RH) while feeding on A. siro, as well as the functional responses of both species' protonymphs and females to L. bostrychophila eggs at 28 °C and 75% RH. Cheyletus malaccensis had a shorter development time and longer adult survival time than C. eruditus at 28 °C and 75% RH and could establish populations faster than C. eruditus while preying on A. siro. The protonymphs of both species showed a type II functional response, while the females showed a type III functional response. Cheyletus malaccensis showed a higher predation ability than C. eruditus, and the females of both species had a higher predation ability than the protonymphs. Based on the observed development times, adult survival times, and predation efficiency, Cheyletus malaccensis has much greater biocontrol potential than C. eruditus.

Evaluation of Leucopis hennigrata (Diptera: Chamaemyiidae) as a classical biological control agent of Adelges nordmannianae (Hemiptera: Adelgidae) in northern Europe

The silver fly Leucopis hennigrata McAlpine is a predator of the silver fir wooly adelgid, Adelges nordmannianae (Eckstein), a pest in the European production of Christmas trees. While the fly is known to be a common native predator of the adelgid in Georgia, Turkey, and central Europe, it is absent from northern Europe, where the Christmas tree production is an important industry. Therefore, L. hennigrata has been suggested as a classical biological control agent of Ad. nordmannianae in northern Europe. Here, we evaluated the fly’s suitability as a classical biological control agent in terms of (1) differences between Asian and European populations, (2) its abundance relative to other predators of Ad. nordmannianae, (3) larval feeding efficacy, as well as (4) the physiological and (5) ecological prey preference of the fly. The results showed that despite genetic divergence between Western Asian and Central European populations, L. hennigrata is a dominant natural enemy of Ad. nordmannianae in Switzerland, the Pontic mountains in northern Turkey, and in the Greater and Lesser Caucasus mountains. Larvae of L. hennigrata killed on average 57–117 eggs in 24 h, depending on their size, the number of eggs offered to them, and possibly some environmental factors. In no-choice tests, adult flies oviposited on twigs containing different non-target adelgid, aphid, and scale insect species. Larvae of L. hennigrata were observed to feed on several of them. However, only the non-target species Mindarus abietinus Koch supported development of a single specimen to the adult stage. During field surveys in Switzerland and Georgia, L. hennigrata was never found on any sampled non-target species. Based on our findings, we conclude that L. hennigrata is a suitable classical biological control agent because it (1) is already present in countries that neighbor northern Europe, (2) is a dominant natural enemy of the pest in Switzerland, (3) is an efficient predator of the pest’s eggs, and (4) seems to be specific to Ad. nordmannianae in its ecological range.

Reproductive collapse in European beech results from declining pollination efficiency in large trees.

Climate warming increases tree mortality which will require sufficient reproduction to ensure population viability. However, the response of tree reproduction to climate change remains poorly understood. Warming can reduce synchrony and interannual variability of seed production ("masting breakdown") which can increase seed predation and decrease pollination efficiency in trees. Here, using 40 years of observations of individual seed production in European beech (Fagus sylvatica), we showed that masting breakdown results in declining viable seed production over time, in contrast to the positive trend apparent in raw seed count data. Furthermore, tree size modulates the consequences of masting breakdown on viable seed production. While seed predation increased over time mainly in small trees, pollination efficiency disproportionately decreased in larger individuals. Consequently, fecundity declined over time across all size classes, but the overall effect was greatest in large trees. Our study showed that a fundamental biological relationship-correlation between tree size and viable seed production-has been reversed as the climate has warmed. That reversal has diverse consequences for forest dynamics; including for stand- and biogeographical-level dynamics of forest regeneration. The tree size effects suggest management options to increase forest resilience under changing climates.

The paradox of searching efficiency or why are violent population cycles so uncommon in terrestrial ecosystem

The searching efficiency of predators depends on the balance between the adaptations of the predator and the counter‐adaptations of the prey. In this evolutionary race, the prey should normally have the upper hand, as it can perform tradeoffs between efficiency in resource use and ability to avoid predators. In terrestrial predator–herbivore systems, however, the huge difference in food quality between prey and predators seems to give predators an advantage. In productive terrestrial ecosystems, predators thus chronically overexploit herbivores, i.e. regulate them at densities far below the point of maximum sustainable yield. Assuming type II functional response, this should result in violent limit cycle dynamics. In reality, however, such cycles are only common at high latitudes, whereas the herbivory‐based food webs of species‐rich ecosystems at middle and low latitudes are characterized by asymptotic dynamics, where numerical changes only occur in response to external forcing. One way or another, diversity thus seems to beget stability in terrestrial grazing webs. We propose that strong, donor‐controlled energy flows from the detritus web and directly from plants to predators are the key for the prevalence of asymptotic dynamics at middle and low latitudes. These flows support generalists with type III functional response and, therefore, a capacity to curb budding outbreaks at an early stage. The ongoing extinction wave could critically weaken these stabilizing interactions, which could destabilize currently stable food webs. and result in violent limit cycle dynamics in ecosystems, where the dominating species have evolved under asymptotic dynamics. This could cause secondary extinctions and inflict large economic losses.Keywords: extinction, food webs, limit cycles, overexploitation, searching efficiency, stability

Predatory Efficiency of Eupoedes Corollae (Fabricius)( Diptera: Syrphidae) to Different Densities of Aphis Gossypii and Aphis Nerii

Predatory efficiency of Eupoedes corollae predator's larvae toward densities of 25, 50, 75, 100 insect of Aphis gossypii and of Aphis nerii, a study was carried out of the laboratory in growth chamber with a temperature of 24±1 C◦ and 70 ± 10 % RH and photoperiod 12: 12 hours. The results showed that the predator E. corollae larvae consumption in different percentage according to the prey's species and the number provided, and that 50 density of cotton aphid was the best in the daily and total consumption of E.corollae predator, in addition to the relatively low development period of predator larvae at the same density. The average of consumption of the predator's larvae instars was proportional to the different densities of the aphids 25, 50.75 and 100 insect, as it reached to ( 84.64, 143.16, 170.9 and 217.93) of cotton aphid and (56.23, 110.67, 124.78 and 148.16) insects of oleander aphid , respectively. The average of aphid is estimated at 154.2 and 110.2 insect, respectively, for the two species with significant differences between them.

Dietary, locomotory, and metabolic reactions of Abax parallelus (Coleoptera, Carabidae) to acute thiamethoxam intoxication.

Carabids (Coleoptera: Carabidae) are abundant predators in ecosystems and serve as pest biocontrol in agroecosystems and forestry. Here we test the impact of thiamethoxam, among the most used neonicotinoids on the consumption rate, locomotion, metabolomics, and oxidative stress level measuring superoxide dismutase (SOD) activity in a predatory carabid, Abax parallelus (Duftschmid, 1812), after acute exposure in the laboratory trials, to get additional data that might link the use of pesticides and predation efficiency. Beetles were exposed to increasing concentrations of thiamethoxam by dipping method, and left to feed overnight prior to the assays. The results showed that individuals treated with higher concentrations of thiamethoxam (20 and 40 mg/L) consumed significantly less food per body weight and had a higher share of intoxicated and moribund individuals. The mass of consumed food per beetle body weight and observed locomotion did not differ significantly between control and groups treated with lower concentrations of thiamethoxam. There are significant differences in concentrations of some metabolites between treated and control individuals, primary in succinate and d-glucose, indicating a disruption in energy production. On the other hand, there is no statistically significant differences in SOD activity among the groups. To conclude, acute exposure to thiamethoxam can result in negative sub-lethal effects in predatory activity and energy budget, while the effects of long-term exposure to lower doses require further research, as well as field assessment on the predation efficiency after pesticide application.

PH-responsive subcutaneous implants prepared via hot-melt extrusion and fluidised-bed spray coating for targeted invasive predator control

Globally, invasive mammalian predators are responsible for the depredation and extinction of threatened species. The development of innovative control methods that target the most impactful of these predators is crucial to ensure the successful conservation of threatened species. Feral cats (Felis catus) are one of the most damaging invasive mammalian predators, particularly in Australia, where they are estimated to kill more than 1.5 billion mammals, birds, and reptiles annually. Mammals are disproportionally depredated by feral cats, and efforts to reintroduce or conserve remnant populations of threatened mammal species are hampered by shortfalls in current control methods. To address this challenge, we have prototyped the population-protecting implant (PPI), a subcutaneous implant that is designed to target the most dangerous and efficient predators, so called ‘problem individuals’. Conceptually, the implant has a reverse enteric coating that is stable in the subcutaneous environment of a prey animal but dissolves rapidly in the gastric environment of a predator, resulting in the release of a toxic payload and death of the predator. In this work we report a novel approach for the manufacture of PPIs, that combines hot-melt extrusion and fluidised-bed spray coating, to respectively afford implants with accurate drug loading and a uniform reverse-enteric coating. Most of the implants bearing a 300 μm coating were found to effectively contain their payload for more than 280 d in vitro, in a simulated subcutaneous environment (pH 7.4, 37 °C) but release it within 2.5 h in vitro under simulated gastric conditions (pH 1.5, 37 °C). However, two failures were observed at 64 d and 200 d, likely due to the increased osmotic pressure caused by the soluble core. This work highlights a revised implant design that may improve implant stability in vivo and facilitate the translation of the PPI to field use, for the conservation of threatened species. We also introduce a novel and facile approach to determine the loading of non-chromophoric payloads in hot-melt extruded systems that is highly relevant for the determination of active pharmaceutical ingredients in drug-delivery formulations.

Role of predation efficiency in prey–predator dynamics incorporating switching effect

In the context of foraging behaviour, a species can be classified as a generalist or a specialist based on the breadth of their diet. Specialist species have a restricted diet and occupy a much narrower niche, whereas generalist species consume a wide range of resources and thrive in a variety of habitats. In this article, we propose an ecological model with two types of prey, with different fertility rates and nutritional levels, devoured by their respective specialist and the generalist predators. Further, it is assumed that the hunting process of generalist predator follows the switching mechanism. The growth of generalist predator is also influenced by external food sources and intra-specific competition. Our analyses reveal that the only species that may suffer extinction possibility are the specialist predators. The specialists relying on higher reproducing prey may face the danger of extinction, but this is not the case for those specialist predators that consume nourishing prey. Coexistence of all species is achievable if (i) specialists are sufficiently efficient in comparison to the number of available prey and (ii) the expansion of generalist predator is reduced due to shortage of external food sources. For lower hunting efficiency of both the specialist predators, the coexistence of all specialists with the generalist is expected to be unachievable in nature. In this case, only the specialist who consumes more reproductive and nutritious prey may cohabit with the generalist. Our findings may provide possibilities for empirical research on individual specialization.

Predation efficiency of the carnivorous aquatic plant Utricularia australis against Asian tiger mosquito Aedes albopictus larvae: Implications for biological control

The Asian tiger mosquito, Aedes albopictus, one of the world’s worst invasive animal species and competent vector of many arboviruses, poses a serious threat to human health. An effective and environmentally friendly control strategy is required to mitigate the negative impacts of this pest. The aquatic carnivorous plants of the Utricularia genus, known as bladderworts, feed on invertebrates using their modified leaves as traps (bladders) and could be considered for biological control. The southern bladderwort, U. australis, was used in a no-choice experiment to test its predation ability against Ae. albopictus larvae. Larvae were divided in two size groups: 1st–2nd and 3rd–4th larval instars. Twenty Ae. albopictus larvae were placed inside 1 l plastic cups with a 30 cm long segment of the plant and left for a 7-day period. Twelve segments of U. australis were used, six for each larval size group, counting the number of bladders of each segment at the beginning of the experiment. The 7-day process was repeated five times for each segment/cup over a two-month period. The number of captured larvae and emerged adults was recorded daily. A total of 84 captured larvae were chosen to measure larval length, percentage of larval body trapped within the bladder, bladder perimeter and bladder area, in order to evaluate the ability of the bladders in capturing larvae, by complete or partial suction of the body, depending on the relative sizes of larvae and bladders. Results indicated that U. australis is an effective predator of Ae. albopictus larvae, with a higher efficiency against the 1st–2nd instar group (72%) compared to the 3rd–4th group (39%). The number of captured larvae depended on the number of bladders on each segment and instar group. The percentage of trapped larval body depended on the relationship between bladder size and larval length. Although the bladders effectively captured small larvae by complete suction of the body, they also killed 3rd–4th instar larvae by trapping a small portion of the body within the lumen. The plant segments continuously captured mosquito larvae, with an efficiency that did not decrease during the 2-month period. The use of U. australis as a biocontrol agent against Ae. albopictus larvae could be favoured by its ecological plasticity, broad distribution, its ability to thrive in small containers and the good overlap of the two species regarding phenology and habitat preferences.

Sublethal and transgenerational effects of synthetic insecticides on the biological parameters and functional response of Coccinella septempunctata (Coleoptera: Coccinellidae) under laboratory conditions.

Synthetic insecticides have been an inevitable part of plant protection throughout the world. Sublethal effects of these chemicals on beneficial insect species are one of the contemporary issues these days. Using the age-stage, two-sex life table model, this study evaluated the sublethal and transgenerational effects of six synthetic insecticides (imidacloprid, thiamethoxam, lambda-cyhalothrin, cypermethrin, chlorpyrifos and profenofos) commonly applied to winter vegetables, on the fitness and predation of the seven-spotted ladybeetle, Coccinella septempunctata, which is an efficient predator of aphids worldwide. According to results, all insecticides at their sublethal doses (LC30) significantly suppressed the emergence of adults, adult weight, fertility and fecundity of the parental generation compared to control treatment. The larval stage was prolonged and oviposition, fecundity and total longevity of the adult beetles were decreased in unexposed progeny whose parents were exposed to sublethal doses of all insecticides. Moreover, the biological parameters of adults, including the intrinsic rate of increase (r), finite rate of increase (λ) and net reproductive rate (R 0) were significantly reduced when exposed to sublethal doses of insecticides. The predation rate of the F1 generation adults was also decreased after exposure to the sublethal doses of insecticides. However, chlorpyrifos, profenofos, lambda-cyhalothrin and cypermethrin exhibited more deleterious effects on the fitness and population parameters of beetles than imidacloprid and thiamethoxam.

Temperature fluctuation alters optimal predator community composition for anticipated biological control

Alongside pesticides and specialist predators, natural communities of generalist beetle and spider predators play an important role in suppressing agricultural pests. However, the predation pressure of natural communities can be unpredictable. Overall predation pressure is influenced by a dense network of potential intraguild interactions, which are further shaped by species traits and environmental factors. Understanding how these different influences combine to impact pest control is especially important in the context of changing global temperatures. Recent empirical studies have demonstrated that the foraging behavior of arthropod predators is influenced by an interaction between temperature and predator body size. To explore the consequences of these findings for intraguild interactions and pest control, we expand a previously published model describing interactions between arthropod predators and a pest population. The model assumed that interaction strengths are influenced by body size and habitat preference. In our updated model, we incorporate the effect of temperature on predator foraging activity. We parameterize the model to match empirically observed predator community composition in 10 agricultural fields and use simulations to demonstrate how temperature-dependent behaviors change the expected efficiency of the natural predator community. Then, we use an optimization approach to identify the most efficient composition of natural predators for pest control. We then evaluate whether the most efficient predator compositions would change with increasing average daily temperature and its variability, as is expected under future temperature change. We find that optimal communities often include predators with complementary foraging activity and that in 2 fields, the optimal community changes drastically under future temperatures. We also note that at some temperatures, foraging activity reduces the negative effects of intraguild interference on pest consumption. This work allows us to assess the effect of climate change on the efficiency of natural predator communities to control pest populations and provide guidance for farmers to design pest management strategies tailored to different climate scenarios.

The Adult Tendency of Eleven-Spotted Ladybird, Coccinella undecimpunctata for Preference of Certain Type of Aphid

Ibrahim, A.K. 2023. The Adult Tendency of Eleven-Spotted Ladybird, Coccinella undecimpunctata for Preference of Certain Type of Aphid. Arab Journal of Plant Protection, 41(4): 369-374. https://doi.org/10.22268/AJPP-41.4.369374 This study explored the extent of eleven ladybirds preference to a specific aphid species, i.e., Aphis fabae, A. nerii, Macrosiphoniella sanborni and Hyalopterus pruni and the extent of the host plant and type of prey in attracting predators. Results obtained showed a preference of adult ladybird predators for H. pruni, Macrosiphoniella sanborni, Aphis nerii, whereas Aphis fabae was the least attractive and consumed by predators. The consumption rate of apricot aphid reached 23.66% in the presence of aphids and the host plant together. The most attraction to apricot leaves in the presence of the plant only was 55.90%. The time required for ladybirds to reach the first prey was 2.15 min for the apricot aphid in the presence of aphids and plants together. Furthermore, the ladybirds reached the prey within 1.30 minutes in the presence of aphids only. The predation efficiency of the four larval instars varied according to the type of aphids. It reached 86.30% for the fourth larval instar on apricot aphids and was the highest compared with the rest of the aphid species, which ranged between 7.10 and 84%. The general average predation efficiency values on aphids were 57.45% for H. pruni, 53.13% for Macrosiphoniella sanborni, 46.05% for A. nerii and 41.16% for A. fabae. The relative efficiency values for the larval instars reached 12.25, 42.27, 60.20 and 83.50%, respectively, for the first, second, third and fourth instars. This was confirmed by the high attraction of predatory ladybirds towards H. pruni and Macrosiphoniella sanborni, compared to Aphis nerii and Aphis fabea. The proportion of aphids consumed by ladybirds in the presence of the plant host was highest for H. pruni and lowest on Aphis fabea. Keywords: Aphids, ladybugs, plant host, predation efficiency

Complex oscillatory patterns in a three-timescale model of a generalist predator and a specialist predator competing for a common prey

In this paper, we develop and analyze a model that studies the interaction between a specialist predator, a generalist predator, and their common prey in a two-trophic ecosystem featuring three timescales. We assume that the prey operates on a faster timescale, while the specialist and generalist predators operate on slow and superslow timescales respectively. Treating the predation efficiency of the generalist predator as the primary varying parameter and the proportion of its diet formed by the prey species under study as the secondary parameter, we obtain a host of rich and interesting dynamics, including relaxation oscillations, mixed-mode oscillations (MMOs), subcritical elliptic bursting patterns, torus canards, and mixed-type torus canards. By grouping the timescales into two classes and using the timescale separation between classes, we apply one-fast/two-slow and two-fast/one-slow analysis techniques to gain insights about the dynamics. Using the geometric properties and flows of the singular subsystems, in combination with bifurcation analysis and numerical continuation of the full system, we classify the oscillatory dynamics and discuss the transitions from one type of dynamics to the other. The types of oscillatory patterns observed in this model are novel in population models featuring three-timescales; some of which qualitatively resemble natural cycles in small mammals and insects. Furthermore, oscillatory dynamics displaying torus canards, mixed-type torus canards, and MMOs experiencing a delayed loss of stability near one of the invariant sheets of the self-intersecting critical manifold before getting attracted to the adjacent attracting sheet of the critical manifold have not been previously reported in three-timescale models.

Efficacy of Some Predators and Lecanicillium lecanii Fungus in Controlling of Aphis gossypii (Glover) and Myzus persicae (Sulzer) in Potato Crop

Lokma, N., A.A.A. Saleh, S.A.M. Amer and M F.M. Zawrah. 2023. Efficacy of Some Predators and Lecanicillium lecanii Fungus in Controlling of Aphis gossypii (Glover) and Myzus persicae (Sulzer) in Potato Crop. Arab Journal of Plant Protection, 41(2): 152-160. https://doi.org/10.22268/AJPP-041.2.152160 This study was conducted to evaluate the efficiency of predators and Lecanicillium lecanii suspension as bicontrol agents against Myzus persicae and Aphis gossypii in potato crop, whereas Aphis gossypii had two peaks in the third week of March and April in 2020 and 2021 seasons. In addition, M. persicae had two peaks for both seasons in the fourth week of March and third week of April in 2020 and in the third week of March during 2021. The common predators observed in potato fields were: Coccinella undecimpunctata L., Chrysoperla carnea Steph., Coccinella septumpunctata, Metasyrphus corollae F. and Cydonia vicina isis (Muls.). Regarding potato predators, one peak was found in the second week of March (60 predators/25 leaves) during the 2020 season, and two peaks were found in the third week of March and second week of April (53 and 38 predators/25 leaves, respectively), in 2021 season. On the 8th day after treatment, the entomopathogenic fungus L. Lecanii produced maximum aphid mortality at highest concentration of 108 conidia/ml and 50% concentration of fungal metabolites for both M. persicae and A. gossypii. Meanwhile, L. lecanii 50% metabolites solution had more latent effect by decreasing the longevity and the number of nymphs than when using the spore suspension of 108 conidial/ml. Keywords: A. gossypii, M. persicae, aphid predators, Lecanicillium lecanii, potato.

Structured foraging of soil predators unveils functional responses to bacterial defenses

Predators and their foraging strategies often determine ecosystem structure and function. Yet, the role of protozoan predators in microbial soil ecosystems remains elusive despite the importance of these ecosystems to global biogeochemical cycles. In particular, amoebae-the most abundant soil protozoan predator of bacteria-remineralize soil nutrients and shape the bacterial community. However, their foraging strategies and their role as microbial ecosystem engineers remain unknown. Here, we present a multiscale approach, connecting microscopic single-cell analysis and macroscopic whole ecosystem dynamics, to expose a phylogenetically widespread foraging strategy, in which an amoeba population spontaneously partitions between cells with fast, polarized movement and cells with slow, unpolarized movement. Such differentiated motion gives rise to efficient colony expansion and consumption of the bacterial substrate. From these insights, we construct a theoretical model that predicts how disturbances to amoeba growth rate and movement disrupt their predation efficiency. These disturbances correspond to distinct classes of bacterial defenses, which allows us to experimentally validate our predictions. All considered, our characterization of amoeba foraging identifies amoeba mobility, and not amoeba growth, as the core determinant of predation efficiency and a key target for bacterial defense systems.

Impact of elevated CO2 on feeding potential of wolf spider against brown planthopper (Nilaparvata lugens)

An experiment was conducted at Department of Entomology, Indian Agricultural Research Institute, New Delhi during 2015–16 and 2016–17 to study the impact of elevated CO2 on functional response of wolf spider, Pardosa pseudoannulata (Boesenberg and Strand, 1906) against brown planthopper, Nilaparvata lugens (Stal, 1854) (Hemiptera: Delphacidae). Spider feeding rate on BPH was higher in jar arena compared to microcosm arena both under ambient CO2 and elevated CO2 conditions. Regression of number of attacked prey (1/Ha) upon prey density per unit area (H) over time duration of experiment (T) in microcosm and in jar arena under ambient and elevated CO2 revealed type II functional response. Attack rate, maximum attack rate and efficiency parameters were higher and handling time was lower in both jar arena and microcosm under elevated CO2 condition compared to ambient CO2 condition. Simultaneously, predators might have consumed more number of preys due to their poor nutrient quality under elevated CO2 compared to ambient CO2. It was revealed that with increase of predator density within the same prey density in same area under both ambient and elevated CO2 conditions, the prey control might have optimized. This information generated would support the planthopper management by regulating predator number for increased predator efficiency.

Pharmaceutical pollution disrupts the behavior and predator-prey interactions of two widespread aquatic insects.

Pharmaceutical pollution represents a rapidly growing threat to ecosystems worldwide. Drugs are now commonly detected in the tissues of wildlife and have the potential to alter the natural expression of behavior, though relatively little is known about how pharmaceuticals impact predator-prey interactions. We conducted parallel laboratory experiments using larval odonates (dragonfly and damselfly nymphs) to investigate the effects of exposure to two pharmaceuticals, cetirizine and citalopram, and their mixture on the outcomes of predator-prey interactions. We found that exposure to both compounds elevated dragonfly activity and impacted their predation success and efficiency in complex ways. While exposure to citalopram reduced predation efficiency, exposure to cetirizine showed varied effects, with predation success being enhanced in some contexts but impaired in others. Our findings underscore the importance of evaluating pharmaceutical effects under multiple contexts and indicate that these compounds can affect predator-prey outcomes at sublethal concentrations.

Predation capacity of Bradymonabacteria, a recently discovered group in the order Bradymonadales, isolated from marine sediments.

Bacterial predation is a vital feeding behavior that affects community structure and maintains biodiversity. However, predatory bacterial species in coastal sediments are comparatively poorly described. In this study, the predation capacity of all nine culturable Bradymonabacteria strains belonging to the recently discovered order Bradymonadales was determined against different types of prey. The predatory efficiency of Bradymonabacteria increased as the initial prey proportion in a mixed culture decreased. When the initial prey proportion was 0.5, the number of surviving prey bacterial cells significantly decreased after 4h of predation with the Bradymonabacteria strains TMQ1, SEH01, B210 and FA350. However, growth of the prey strain occurred in the presence of the Bradymonabacteria strains TMQ4, TMQ2, TMQ3, V1718 and YN101. When the initial prey proportion decreased to 0.1 or 0.01, most of the Bradymonabacteria strains preyed efficiently. Furthermore, established neighboring colonies of prey were destroyed by Bradymonabacteria. This invading predation capacity was determined by the predation ability of the strain and its motility on the agar surface. Our findings provide new insights into the potential ecological significance of predatory Bradymonabacteria, which may serve as a potential probiotic for use in the aquaculture.

Predatory efficiency of dragonfly nymphs, Crocothemis servilia and Rhyothemis variegata against the mosquito, Culex quinquefasciatus Say

This study compared the predatory potential of nymphs of two dragonfly species viz. Crocothemis servilia (Drury, 1773) and Rhyothemis variegata (Linnaeus, 1763) using the different larval instars and pupae of Cx. quinquefasciatus (Say, 1823) as preys in normal laboratory settings. Field-collected fed and 24 h starved nymphs of C. servilia and R. variegata were offered 1st, 2nd, 3rd and 4th instar larvae and pupae of Cx. quinquefasciatus to monitor the rate of predation. A 24 h starved nymph of C. servilia showed the highest predation on the 2nd instar larvae (92.00±4.06%) followed by the 3rd (83.00±5.61%), 4th (80±6.89%) and 1st (76.00±4.85%) instar larvae and the pupae (26.00±2.91), respectively, whereas, that of R. variegata exhibited the highest consumption of the 1st instar larvae (90.00±3.54 %) followed by the 2nd (88.00±5.61 %), 3rd (82.00±3.74 %), 4th (70.00±7.91 %) larval instar and the pupae (23.00±4.63), respectively within 24 h exposure. In the same period, the fed nymphs of C. servilia showed maximum consumption of the 2nd instar larvae (77.00±3.54%) followed by the 3rd (76.00±4.58%), 4th (64.00±4.00%) and 1st instar (55.00±3.53%) larvae and the pupae (24.00±3.67), respectively, whereas, that of R. variegata exhibited highest consumption of the 1st instar larvae (67.00±5.38 %) followed by the 2nd (65.00±10.12 %), 3rd (58.00±8.46 %) and 4th (53.00±4.06 %) instar larvae and the pupae (21.00±2.92), respectively. The rate of predation was significant on all the larval instars and the pupae compared to their control counterparts (p<0.05) and the starved larvae and nymphs of both the dragonfly species showed higher predation compared to the fed nymphs. The aforementioned findings suggest that nymphs of both of the dragonfly species exhibited considerable predation potential against the immature stages of the Cx. quinquefasciatus mosquito. The present study recommends assessing the feasibility of using these species in large-scale mosquito control programs.

Effects of Crop Resistance on the Tritrophic Interactions between Wheat Lines, Schizaphis graminum (Hemitera: Aphididae), and Propylaea japonica (Coleoptera: Coccinellidae).

Crop resistance and biological control are both considered efficient and environmentally friendly methods of sustainable pest control. In this study, we aimed at investigating the direct influence of four wheat lines with varying resistance level on the life-history traits of the greenbug, Schizaphis graminum, and the mediational effect on the functional response of a predatory ladybird, Propylaea japonica, under laboratory conditions. Results showed that the aphid fitness was the lowest for aphids that had been feeding on wheat line ‘98-10-19’ for one year. These aphids had the longest development time, and least adult mass, minimal mean relative growth rate, and lowest reproductive fitness. In contrast, the aphids that fed on wheat line ‘98-10-30’ were the fittest, with the shortest development time and highest levels of reproductive fitness. The predatory activities of the ladybeetle, especially the adult male significantly decreased following the consumption of aphids belonging to the ‘98-10-19’-acclimated population. However, there were no significant differences in predatory efficiency (net attack frequency) among the four aphid acclimated populations. Our results showed that the wheat line ‘98-10-19’ has a relative higher resistance to S. graminum than the other three wheat lines, which could further decrease the amount of prey available for consumption. However, the ecological effect of the resistance of ‘98-10-19’ to S. graminum posed no negative influence on the biocontrol potential of P. japonica to these aphids, as their predatory efficiency increases at the fourth instar larvae phase.