Life Stages Of Prey Research Articles

Neoseiulus mites as biological control agents against Megalurothrips usitatus (Thysanoptera: Thripidae) and Frankliniella intonsa (Thysanoptera: Thripidae) on cowpea crop: laboratory to field.

Megalurothrips usitatus (Bagnall) (Thysanoptera: Thripidae) and Frankliniella intonsa (Trybom) (Thysanoptera: Thripidae) have been detrimental to cowpea production in many countries. Laboratory experiments were conducted to determine the prey stage preference and functional response of 2 predatory mites species, Neoseiulus barkeri (Hughes) (Acari: Phytoseiidae), and Neoseiulus californicus (McGregor) (Acari: Phytoseiidae), towards 2 thrips species (TS), M. usitatus, and F. intonsa, at varying densities and life stages on cowpea. Results shown that Neoseiulus species had a preference for different life stages of prey. Neoseiulus barkeri consumed more M. usitatus nymphs, while N. californicus consumed more F. intonsa (second-instar nymphs). The functional response of the 2 Neoseiulus spp. to nymphs of 2 TS was Type II on cowpea. The higher attack rate coefficient (a') and shorter handling time (Th) values were found on N. barkeri against M. usitatus, and a similar trend was found for those in N. californicus against F. intonsa. Field-caged trials were conducted to evaluate the effectiveness of Neoseiulus spp. in controlling 2 TS. The results have shown that Neoseiulus spp. was effective in controlling the 2 TS, with varying control efficacies at high or low release rates. The study provided valuable information on using Neoseiulus spp. as biological control agents against M. usitatus and F. intonsa in cowpea crops.

Functional responses of predatory mites, Cheyletus eruditus (Schrank) and Cheyletus malaccensis Oudemans (Trombidiformes: Cheyletidae) to Liposcelis decolor (Pearman) (Psocodea: Liposcelididae)

Psocids (Psocodea: Liposcelididae) are stored-product pests that are not easily managed by standard management tools and practices, such as insecticides. Biological control can be an effective alternative or complement to pesticides in the management of psocids in some scenarios. This study was carried out to evaluate the efficiency of two predatory mite species, Cheyletus eruditus (Schrank) and Cheyletus malaccensis Oudemans (Trombidiformes: Cheyletidae) to manage Liposcelis decolor (Pearman) (Psocodea: Liposcelididae), a key stored product psocid pest species that is phosphine tolerant. The functional responses of these two cheyletid mites to nymphs, adult males and females of L. decolor was determined under laboratory conditions at 24 ± 1 °C and 0: 24 (L: D) photoperiod. Based on the results of maximum likelihood estimates (MLE) of a logistic regression analysis, the functional responses of both the predatory mites to nymphs and adult males or females of L. decolor were Holling Type II. Subsequent estimations of attack rate (a), handling time (Th), maximum predation (K), and predation efficiency (η) per day (d) using a linearly transformed Hollings Type II model for predators against prey life stages revealed that C. eruditus performance was preferable compared to that of C. malaccensis. Similarly, the per capita consumption rate and searching efficiency of C. eruditus were considerably higher compared to C. malaccensis for all life stages of L. decolor. Nevertheless, further studies are required to validate the efficiency of C. eruditus and C. malaccensis based on other evaluation criteria including field trials, and their compatibility with other management strategies targeted at stored product pests in order to facilitate the incorporation of these mite species into existing IPM systems for managing psocids.

Prey life stages modulate effects of predation stress on prey lifespan, development, and reproduction in mites.

The non-consumptive effects of predator-induced stress can influence a variety of life-history traits. Many previous studies focused only on short-term effects such as development and reproductive rates. Recent studies have showed that long-term predation stress (given during the whole life of the prey) and short-term predation stress (provided during the immature stage of the prey) could generate completely opposite results: the former could decrease lifespan, whereas the later could increase lifespan. However, it is still unclear whether the advantage is because of the short duration of exposure or the early stage of life during which exposure was exerted. Thus, in this study, the prey (Tyrophagus putrescentiae) was exposed to predation stress from the predator (Neoseiulus cucumeris) during different life stages (larva, protonymph, tritonymph, first 5d of oviposition, the full lifespan or none of the above). The results showed that the predation stress supplied during larval and protonymphal stage delayed development, reduced fecundity and prolonged lifespan of the prey, while the stress given during tritonymphal stage only reduced lifespan slightly and the stress given during the first 5d of oviposition did not change lifespan but reduced fecundity. This study indicated that the effects of predation stress are dependent on prey life stage and the predation stress experienced in the early life stages is important to lifespan modulation.

Prey stage preference and functional response of the seven-spot lady beetle Coccinella septempunctata to the rose aphid, Macrosiphum rosivorum

ABSTRACT The rose aphid, Macrosiphum rosivorum (Zhang), is a serious pest of roses in China. Currently, M. rosivorum is managed using almost exclusively with insecticides; therefore, effective, alternative strategies are needed to reduce this dependence on pesticides and the risk of the development of resistance in rose aphids. This study was conducted to evaluate the potential of the seven-spot ladybird, Coccinella septempunctata (L.), as a biological control agent of M. rosivorum in rose production fields. We determined the prey preference of C. septempunctata at constant densities of M. rosivorum for 1st – 4th instar nymphs and for adults. The results showed that Coccinella septempunctata adults had its highest rate of consumption on 4th instars and its lowest rate of consumption on adults among prey life stages. Furthermore, we defined the functional response of predator adults. C. septempunctata adults displayed a type II functional response on all prey stages. The highest attack rate and shortest handling time were for predators fed 1st instar aphids. The proportion of prey consumed by C. septempunctata was higher at lower densities for all stages of rose aphid, implying that C. septempunctata should be released early in an aphid infestation. Our study indicated that C. septempunctata has the potential to be used for control of rose aphids in rose-production fields.

Effects of predator cues carry over from egg and larval stage to adult life-history traits in a damselfly

Non-consumptive predator effects experienced in early life stages of prey may result in life-history costs in later life stages. Such effects can, for example, alter the growth rate during the juvenile stage, which may carry over to size at maturity. However, we have limited knowledge of the carry-over effects starting from the egg stage through the larval stage to the adult stage. Here, we present results from a laboratory experiment in which we exposed a damselfly, Ischnura elegans, to chemical cues originating from a fish predator, perch. We used a 2 × 2-full-factorial design in which the damselflies were exposed to predator cues during either the immobile egg or the mobile larval stage. The presence of predator cues, i.e., non-consumptive predator effects, during the egg stage caused decreased survival, but only until 2 wk after larval hatching. Predator cues during the larval stage caused decreased survival until emergence and an increase in development time until emergence. However, mass at emergence was not affected by predator cues. When fish cues were present in the egg or larval stage, there was a lower growth rate until final-instar larvae than in larvae that did not receive fish cues. Our results add to the growing number of studies showing that predation-risk cues in the egg stage can carry over to the adult stage, which ultimately could have consequences for adult life-history traits, such as survival and fecundity.

Observations on the feeding preference of the phytoseiid predator, Neoseiulus longispinosus (Evans) on the different life stages of the spider mite, Oligonychu sbiharensis (Hirst)

ABSTRACT A comparative evaluation of feeding preference of the phytoseiid predator, Neoseiulus longispinosus (Evans) was made on the different life stages of spider mite Oligonychus biharensis (Hirst) under laboratory conditions by raising stock cultures of pest mite on leaves of its native host, Bauhinia purpurea. N.longispinosus collected from field was reared on mixed prey stages of O. biharensis. Feeding experiment was conducted following leaf disc method and known numbers of various prey life stages egg, larva, nymphs, and females (pre-oviposition period) were offered simultaneously to the nymph and adult female of N.longispinosus. Number of prey stages consumed by the predator after 24 hours and consumption percentage were recorded. Feeding preference of adult predator towards prey stages decreased as follows: nymph (14.1%)> larva (13.3%)> egg (10.4%) > adult (2.2%). Predator nymph exhibited a similar order of preference with respective consumption rates of 13.3%, 13.3%, 7.5%, and 0% on the egg, larva, nymph, and adult female, respectively. Statistical analysis following ANOVA revealed a significant variation (p < 0.05) in feeding preference of the predator life stages towards varied life stages of the prey mite. Thus, results of the study clearly revealed the bio-control potential of N.longispinosus against the pest mite O. biharensis.

Exposure to predators, but not intraspecific competitors, heightens herbivore susceptibility to entomopathogens

Prey commonly must compete with conspecifics for resources while also defending themselves against predators. Both competition and defense can reduce feeding opportunities, or otherwise strain prey energy reserves, even when the prey is not killed. This suggests that stress from competition and anti-predator defense might yield non-lethal harm that differs quantitatively rather than qualitatively. We examined this possibility for an herbivorous prey species, the Colorado potato beetle (Leptinotarsa decemlineata), feeding among differing numbers of intraspecific competitors while also avoiding predation by Nabis alternatus and Hippodamia convergens. In a field cage experiment, predators and intraspecific competitors similarly reduced the herbivores’ larval survival. Yet, only exposure to predators heightened the risk of beetles later being killed by entomopathogenic nematodes and fungi, as the beetles pupated in the soil. This suggests that the threat of predation was exerting physiological harm to the prey, although it was also possible that a tradeoff existed where those beetles most resistant to predator attack were most susceptible to pathogen infection. In a second experiment, we found that regular touching of larvae by predatory Nabis or Hippodamia, in the absence of actual predation, consistently induced predator-avoidance behaviors by the larvae (e.g., rearing, vomiting, wiggling, etc.) that might be energetically costly. Indeed, only being touched by predators, but not by a wooden dowel as a disturbance control, led to greater susceptibility to entomopathogens as pupae. Altogether, our findings suggest that non-lethal interactions with predators might carry a particular cost to beetles in heightened pathogen susceptibility, not seen when facing competitors or simple disturbance. Additional work is needed to determine the specific physiological mechanism underlying this apparent synergism in the effects of predators and entomopathogens, which spans prey life stages.

Infection pathology and competition mediate host biomass overcompensation from disease.

Predators can increase the biomass of their prey, particularly when prey life stages differ in competitive ability and predation is stage specific. Akin to predators, parasites influence host population sizes and engage in stage-structured interactions, yet whether parasites can increase host population biomass remains relatively unexplored. Using a stage-structured consumer-resource model and a mesocosm experiment with snails and castrating trematodes, we examined responses of host biomass to changes in infection prevalence under variation in host pathology and resource competition. Equilibrium adult host biomass increased with infection prevalence in the model when parasites castrated hosts and adults were superior competitors to juveniles. Juvenile biomass increased with infection prevalence whether parasites caused mortality or castration, but only when juveniles were superior competitors. In mesocosms, increases in infection by castrating trematodes reduced snail egg production, juvenile abundance, and adult survival. At high competition, juvenile growth and total biomass increased with infection prevalence due to competitive release. At low competition, juvenile biomass decreased with infection due to reduced reproduction. These results highlight how disease-induced biomass overcompensation depends on infection pathology, resource availability, and competitive interactions within and between host life stages. Considering such characteristics may benefit biocontrol efforts using parasites.

The effect of predator presence on the behavioral sequence from host selection to reproduction in an invulnerable stage of insect prey.

Predator-prey interactions primarily focus on prey life-stages that are consumed. However, animals in less vulnerable life-stages might also be influenced by the presence of a predator, making our understanding of predation-related impacts across all life-stages of prey essential. It has been previously demonstrated that Podisus maculiventris is a voracious predator of eggs and larvae of Leptinotarsa decemlineata, and that larvae will alter their behavior to avoid predation. However, the adult beetles are not readily consumed by P. maculiventris, raising the question of whether they will respond to predators to protect themselves or their offspring. Here, we examine the effect of predation risk by P. maculiventris, on three adult behaviors of L. decemlineata; colonization, oviposition, and feeding, and the resulting impact on host plant damage. In an open-field test, there was no difference in natural beetle colonization between plots with predation risk and control treatments. However, subsequent host plant damage by adult beetles was 63.9% less in predation risk treatments. Over the lifetime of adult beetles in field mesocosms, per capita feeding was 23% less in the predation risk treatment. Beetle oviposition was 37% less in the presence of predators in a short-term, greenhouse assay, and marginally reduced in longer term field mesocosms. Our results indicate that predation risk can drive relatively invulnerable adult herbivores to adjust behaviors that affect themselves (feeding) and their offspring (oviposition). Thus, the full impact of predator presence must be considered across the prey life cycle.

Efficiency against the Two-spotted spider mite Tetranychus urticae and prey-age-related choice of three predatory mites

Specialist and generalist predator mites have been recommended against the Two-spotted spider mite (Tetranycus urticae) as biological control agents, but their effectiveness in population regulation has been rarely examined under circumstances when prey had the opportunity to express antipredatory responses. We tested the efficiency and preference for prey life stages of three predator mites, one specialist (Phytoseiulus persimilis) and two generalists (Amblyseius swirskii and Iphiseius degenerans). We used two predator densities and performed the experiment under ‘seminatural’ conditions. We found that significantly less eggs and adult spider mites survived in the presence of P. persimilis compared to the control group, and this predator mite consumed more eggs at high density than the other predators. In the presence of A. swirskii fewer adult spider mites survived at low density compared to the control, whereas egg survival was lower than in the control group at both densities. In the presence of I. degenerans, only the survival of eggs was lower than in the control group and only at high density. Our results suggest that the generalist A. swirskii, but not I. degenerans, may be efficient in regulating prey populations through egg consumption, and, thus, represents an alternative to the effective specialist predator.

Harbour seals target juvenile salmon of conservation concern

Knowing the species and life stages of prey that predators consume is important for understanding the impacts that predation may have on prey populations, but traditional methods for determining diets often cannot provide sufficient detail. We combined data from two methods of scat analysis (DNA metabarcoding and morphological prey ID) to quantify the species and life stages of salmon (Oncorhynchus spp.) consumed by harbour seals (Phoca vitulina) in the Strait of Georgia, Canada, where juvenile Chinook (Oncorhynchus tshawytscha) and coho (Oncorhynchus kisutch) salmon survival is poor. Harbour seals primarily consumed adult salmon of lesser conservation concern in the fall (August–November): chum (Oncorhynchus keta: 18.4%), pink (Oncorhynchus gorbuscha: 12.6%), sockeye (Oncorhynchus nerka: 7.4%), Chinook (7.1%), and coho (1.8%). However, the opposite species trend occurred during the spring when seals preferred juvenile salmon of greater conservation concern (April–July): coho (2.9%), Chinook (2.9%), sockeye (2.5%), pink (1.4%), and chum (0.8%) — percentages that can equate to many individuals consumed. Our data suggest that harbour seals select juveniles of salmon species that out-migrate at ages &gt;1 year and provide evidence of a potential causal relationship between harbour seal predation and juvenile salmon survival trends.

Diet of the insectivorous batPipistrellus nathusiiduring autumn migration and summer residence

Migration is widespread among vertebrates, yet bat migration has received little attention and only in the recent decades has a better understanding of it been gained. Migration can cause significant changes in behaviour and physiology, due to increasing energy demands and aerodynamic constraints. Dietary shifts, for example, have been shown to occur in birds before onset of migration. For bats, it is not known if a change in diet occurs during migration, although breeding season-related dietary preference has been documented. It is known that a diet rich in fats and the accumulation of fat deposits do increase the flight range of migratory bats. Some bat species can be regarded as long-distance migrants, covering up to 2000km between summer and winter roosting areas. Pipistrellus nathusii (Vespertilionidae), a European long-distant migrant, travels each year along the Baltic Sea from north-eastern Europe to hibernate in central and southern Europe. This study presents data on the dietary habits of migrating Pipistrellus nathusii compared with those during the breeding season. We analysed faecal samples from bats on fall migration caught at the Ornithological Field Station in Pape, Latvia and from samples collected in North-Latvian summer roosts. We applied both morphological identification and molecular methods, as morphological methods also recognize life stages of prey and can contribute frequency data. The diets of bats on migration and breeding bats were similar, with Diptera and Lepidoptera comprising the major prey categories. However, certain prey groups could be explained by the different hunting habitats exploited during migration vs. summer residence.

Evaluating the Structure of Enemy Biodiversity Effects on Prey Informs Pest Management

Evaluating the structure of enemy biodiversity effects on prey in agroecosystems can provide insights into biological pest control functioning. With this aim, theoretical models that describe biological mechanisms underlying prey suppression can be developed and confronted with experimental data by means of model selection. Here, we confront multiplicative risk models to evaluate the structure of multiple predator effects on the whitefly Trialeurodes vaporariorum provided in tomatoes by two spiders (Oxyopes lineatus and Pityohyphantes phrygianus) and two mirids (Nesidiocoris tenuis and Macrolophus melanotoma). Biologically meaningful parameters retained in the best models showed that several predator traits differently affected pest control: species-specific per capita predation rates, prey use extent, different type of interactions between predators, and the response of predator species to prey density and environmental temperature. Even from a limited perspective of single-pest control and short term experiment, this study suggests that assembly of the four predator species results in predator complementarity across prey life stages and density, interactions of prey and predators with environmental conditions, and interactions between predators that do not result in whitefly control disruption. Such information about enemy biodiversity and whitefly control functioning can drive hypotheses about sustainable pest management options in local agroecosystems.

Propagation, Synchrony, and Impact of Introduced and Native &lt;I&gt;Laricobius&lt;/I&gt; spp. (Coleoptera: Derodontidae) on Hemlock Woolly Adelgid in Virginia

Synchrony and impact of the predators Laricobius nigrinus Fender and Laricobius rubidus LeConte, on hemlock woolly adelgid, Adelges tsugae Annand, were studied in an eastern hemlock field insectary in Virginia. First, a field insectary for propagation of the introduced L. nigrinus was established by planting hemlocks in 2001, infesting them with hemlock woolly adelgid in 2002 and 2003, followed by releasing 258 L. nigrinus in 2003. Initial sampling showed that the native L. rubidus was present in the area. Hemlock woolly adelgid and both Laricobius species populations increased annually, from which 305 F3 L. nigrinus adults were collected and redistributed to forests in 2007. Second, the phenology of hemlock woolly adelgid and Laricobius spp. life cycles were monitored in 2005 and 2006. Adult L. nigrinus (F2) and L. rubidus were active on hemlock from fall through mid-spring and overlapped with second-instar sistentes nymphs through progredientes eggs. The predators' eggs were oviposited and larvae developed (i.e., F3 L. nigrinus) from late winter to mid-spring on progredientes eggs, indicating synchrony with suitable prey life stages. Third, a predator exclusion experiment was used to examine the relationships between the predators and prey in 2005 and 2006. When exposed to L. nigrinus (F2 adults and F3 larvae) and L. rubidus, hemlock woolly adelgid survival and ovisac density were lower and ovisac disturbance was higher than hemlock woolly adelgid protected in cages. The establishment and production of L. nigrinus at a field insectary, synchronization with, and impacts on hemlock woolly adelgid after a small release 2 yr earlier makes it an important potential biological control agent of hemlock woolly adelgid.

Functional benefits of predator species diversity depend on prey identity

Abstract. 1. Determining the functional significance of species diversity in natural enemy assemblages is a key step towards prediction of the likely impact of biodiversity loss on natural pest control processes. While the biological control literature contains examples in which increased natural enemy diversity hinders pest control, other studies have highlighted mechanisms where pest suppression is promoted by increased enemy diversity.2. This study aimed to test whether increased predator species diversity results in higher rates of predation on two key, but contrasting, insect pest species commonly found in the rice ecosystems of south‐east Asia.3. Glasshouse experiments were undertaken in which four life stages of a planthopper (Nilaparvata lugens) and a moth (Marasmia patnalis) were caged with single or three‐species combinations of generalist predators.4. Generally, predation rates of the three‐species assemblages exceeded expectation when attackingM. patnalis, but not when attackingN. lugens.In addition, a positive effect of increased predator species richness on overall predation rate was found withM. patnalisbut not withN. lugens.5. The results are consistent with theoretical predictions that morphological and behavioural differentiation among prey life stages promotes functional complementarity among predator species. This indicates that emergent species diversity effects in natural enemy assemblages are context dependent; they depend not only on the characteristics of the predators species, but on the identity of the species on which they prey.