Specialist Predators Research Articles

Observation of key phenological stages of hemlock woolly adelgid (Hemiptera: Adelgidae): using citizen science as a tool to inform research and management.

Increasing efficiency of data gathering at the landscape scale on the growing number of pests and pathogens threatening forests worldwide has potential to improve management outcomes. Citizen science is expanding, with growing support and utility in environmental and conservation fields. We present a case study showing how citizen science observations can be used to inform research and management of a devastating forest pest. Hemlock woolly adelgid, Adelges tsugae Annand (Hemiptera: Adelgidae), was introduced to eastern North America, leading to decline and mortality of eastern [Tsuga canadensis (L.) Carrière] (Pinales: Pinaceae)and Carolina hemlock (Tsuga caroliniana Engelmann)trees. Management activities, most notably biological control, rely on observations of A. tsugae phenology to inform the timing of releases and monitoring surveys of their highly synchronized specialist predators. In this article, we outline a citizen science program and report phenological observations on A. tsugae. Additionally, we report data comparing A. tsugae estivation break in Virginia (VA) and New York (NY) State, revealing that estivation break is synchronized between NY and VA. This observation is supported by 6 years of citizen scientist observations, showing similar patterns throughout NY, with egg laying shown to be much more variable than estivation break.

Prey selection by black-footed ferrets (Mustela nigripes): implications for intersexual resource partitioning and conservation

Abstract Intraspecific resource partitioning may play a critical role in how predators optimize prey selection. The Black-footed Ferret (Mustela nigripes; henceforth, ferret) is a highly specialized predator of prairie dogs (Cynomys spp.; henceforth, PDs). Adult ferrets are sexually dimorphic and PDs are of similar size making them a difficult prey item. PD young are born 6 to 8 weeks prior to births of ferrets, producing a crop of smaller prey items during a period when energetic needs of female ferrets are highest. We asked whether relatively small female ferrets select small PDs as prey. We examined survival rates from early to late summer for large and small black-tailed PDs (Cynomys ludovicianus) in Montana and South Dakota as a function of their distance to adult male and female ferrets using capture–mark–recapture of PDs and simultaneous summer monitoring of ferret locations. Survival of small PDs (<600 g) was low when a female ferret was nearby, but distance to nearest female ferret did not affect survival of large PDs. Distance to the nearest male ferret did not influence survival regardless of PD size. Reduced competition from males for a critical food resource needed by females rearing young would benefit fitness of both sexes. If female ferrets depend on young PDs during their reproductive period, existing habitat models may substantially overestimate ferret carrying capacity.

Dynamical behaviors of a specialist predator–prey system in open advective heterogeneous environments

In this paper, we investigate the effect of dispersal and advection on the dynamics of a specialist predator–prey model. More precisely, we show that the linear stability of the semi-trivial steady state is determined by the dispersal rate, the mortality rate of the predator and the advection rate. We point out that compared to homogeneous intrinsic growth rate and carrying capacity, the case in this paper is more complicated. This work gives a investigation to an open problem proposed by Nie et al. in Nie et al. (2020) by considering a more general model, and then, can be seen as a further development of their work (Nie et al., 2020).

Biochemical tracers in spiny icefish (Chaenodraco wilsoni) as indicators of variability in the diet of Antarctic krill (Euphausia superba) in a highly dynamic environment

Spiny icefish (Chaenodraco wilsoni), a common high-Antarctic ichthyofauna icefish, exhibits variable feeding habits in regions around the Southern Ocean. In the Bransfield Strait (BS), C. wilsoni has received considerable attention as it preys predominantly on krill. Antarctic krill (Euphausia superba), the keystone species in the Southern Ocean, has a versatile feeding strategy, particularly in a highly dynamic environment. The central basin of the BS is a highly dynamic environment, providing an ideal place to explore the application of biochemical tracers in a specialist predator to reveal the diet of its prey. In this study, fatty acid and stable isotopic data demonstrated that the trophic niche of C. wilsoni expanded from late austral summer to early fall, which was primarily reflected in variability in the food availability of krill, i.e., herbivorous features were weakened, benthic-feeding features were strengthened, and omnivorous features showed no significant difference. A highly dynamic hydrography, coupled with an unusual diatom bloom in the BS during 2016, may have resulted in krill's prolonged filtering on diatoms in the water column, which was further reflected in the difference in biochemical tracers of C. wilsoni from late austral summer to early fall. The study demonstrated that biochemical tracers can be used to reflect the variability in the diet of prey, particularly in a highly dynamic environment.

Faunal community of a new hot vent field on the Amami Rift

Abstract Deep-sea hydrothermal vents host chemosynthesis-based ecosystems inhabited chiefly by specially adapted animals that do not live anywhere else, and depth has been shown to be a major driver of species composition at vents around Japan. Though the Ryukyu region in southern Japan is home to many hot vents, only two – Minami-Ensei Knoll and Yoron Hole – have been found shallower than 1000 m. Here, we report the discovery of a new vent field on the Amami Rift northwest off Amami Ōshima at 630 m deep. A total of 29 macrofaunal species were recorded from Amami Rift, including 19 vent specialists. Comparison of species composition across the three shallow Ryukyu vents revealed only three shared species, highlighting that all three display distinct community structure. Amami Rift exhibits distinct zonation patterns and is generally more similar to Minami-Ensei than Yoron Hole, but the presence of key taxa such as the sulphide worm Paralvinella and the mussel ‘Bathymodiolus’ platifrons as well as the absence of the symbiotic squat lobster Shinkaia and the limpet Lepetodrilus exemplify its difference with Minami-Ensei. Furthermore, the non-vent specific predators seen in these two sites were completely different. Overall, the Amami Rift vent field can be considered a shallow vent with a unique set of fauna, warranting future research on the mechanisms shaping disparate macrofaunal diversity between nearby shallow vents such as Amami Rift and Minami-Ensei. The unusual geological setting of Amami Rift at the converging point of Okinawa Trough and Ryukyu Arc may influence fluid chemistry to drive such differences.

Coexistence of Ammoxenus (Gnaphosidae) spider species on and between termitaria of Microhodotermes viator (Hodotermitidae) at a Karoo site

Previous studies of some species of Ammoxenus spiders demonstrated them to be monophagous predators of certain termites. Upon observing Ammoxenus spiders preying on the hodotermitid, Microhodotermes viator, we examined the distribution of spiders on or off termitaria (termed heuweltjies) at the Tierberg-LTER study site in the Karoo using pitfall traps deployed monthly over two years. Four species of Ammoxenus were found, but only one, Ammoxenus pentheri, has been described, the other three being new to science. Their coexistence prompts questions concerning niche partitioning among several specialist predators. Our initial study revealed that Ammoxenus and other ground spiders were more abundant on heuweltjies than in the matrix between heuweltjies. The different Ammoxenus species appeared to be disparately associated or disassociated with heuweltjies and had different phenologies. This case of niche partitioning among specialist predators warrants further study.

Modelling Predator–Prey Interactions: A Trade-Off between Seasonality and Wind Speed

Predator–prey interactions do not solely depend on biotic factors: rather, they depend on many other abiotic factors also. One such abiotic factor is wind speed, which can crucially change the predation efficiency of the predator population. In this article, the impact of wind speed along with seasonality on various parameters has been investigated. Here, we present two continuous-time models with specialist and generalist type predators incorporating the effect of wind and the seasonality on the model parameters. It has been observed that wind speed plays a significant role in controlling the system dynamics for both systems. It makes the systems stable for both of the seasonally unperturbed systems. However, it controls the chaotic dynamics that occur in case of no wind for the seasonally perturbed system with the predator as a specialist. On the other hand, for the seasonally perturbed system with a generalist predator, it controls period-four oscillations (which occur considering no wind speed) to simple limit-cycle oscillations. Furthermore, the wind parameter has a huge impact on the survival of predator species. The survival of predator species may be achieved by ensuring a suitable range of wind speeds in the ecosystem. Therefore, we observe that seasonality introduces chaos, but wind reduces it. These results may be very useful for adopting necessary management for the conservation of endangered species that are massively affected by wind speed in an ecosystem.

Bacteria associated with carminic acid metabolism in the intestinal tract of three predators of Dactylopius opuntiae

AbstractDactylopius spp. produce carminic acid as part of defence against predation. The average carminic acid concentration varies depending on the species, e.g., for prickly pear cochineal, Dactylopius opuntiae (Cockerell), and cochineal, Dactylopius coccus Costa (Hemiptera: Dactylopiidae), it is 3–5 and 19–25%, respectively. Generalist predators such as Laetilia coccidivora Comstock (Lepidoptera: Pyralidae) and specialist predators such as Leucopis bellula Williston (Diptera: Chamaemyiidae) and Hyperaspis trifurcata Schaeffer (Coleoptera: Coccinellidae) require detoxification mechanisms, which could be provided by gut bacteria. We determined the diversity of gut‐associated cultivable bacteria in these three predators and their ability to metabolize carminic acid. The bacteria were identified morphologically and by partial sequencing of the 16S rRNA gene. In vitro assays were done to determine their ability to metabolize carminic acid. The greatest culturable bacterial diversity was found in L. coccidivora larvae and H. trifurcata adults, followed by H. trifurcata larvae. The lowest diversity was found in L. bellula larvae. DNA sequencing revealed the presence of Bacillus cereus Frankland & Frankland, Enterococcus gallinarum (Bridge & Sneath) Collins et al., and Enterococcus casseliflavus Collins et al. in L. coccidivora larvae, Enterobacter spec. in larvae of H. trifurcata, Lactococcus lactis (Lister) Schleifer in adults of H. trifurcata, and Staphylococcus spec. in larvae and adults of H. trifurcata. Bacillus pumilus Meyer & Gottheil was only found in L. bellula larvae. In vitro assays showed that all isolates evaluated could metabolize carminic acid, suggesting they play an important role in the predators' ability to metabolize carminic acid. Presence of E. gallinarum, which had the most efficient metabolism of carminic acid, might allow L. coccidivora to feed on the two Dactylopius species regardless of carminic acid concentration.

Nonconsumptive effects of black sea bass (Centropristis striata) on a crustacean mesopredator and the indirect effects on bivalve survival

The consumptive and nonconsumptive effects of predators on their prey and the indirect effects of these interactions that cascade through food webs have been studied for over half a century. In the northwest Atlantic, the stock of black sea bass (Centropristis striata) steeply declined during the 1980s. While population crashes of fished bivalve species coincided with those of black sea bass, the role of black sea bass in driving trophic cascades that indirectly influence bivalve survival has largely been overlooked. Over the past decade, black sea bass have not only been recovering in abundance but warming water temperatures have been driving a northward expansion of the extent of their seasonal migration, resulting in a particularly strong relative recovery along the south shore of Long Island, New York. To explore whether black sea bass alter the foraging rates of mud crabs (Dyspanopeus sayi) on a species of bivalve, blue mussels (Mytilus edulis), we manipulated the presence and position of sea bass within an array of mesocosm tanks. We found that the presence of black sea bass reduced the proportion of blue mussels consumed by mud crabs. Black sea bass presence indirectly elevated blue mussel survival by as much as 47.7% by reducing mud crab per capita consumption of blue mussels by 57.9%. However, there were limitations to the nonconsumptive effects of black sea bass that appeared to depend on their proximity to mud crabs. While our results are from an experimental setup with a simplified food chain and are context dependent, they emphasize the importance of studying how nonconsumptive effects of specific marine predators influence trophic cascades from both conceptual and applied coastal resource management standpoints. Our results suggest that the recovery of black sea bass may bode well for the population restoration of several species of bivalves within estuaries throughout their range. Further, our study provides evidence that indicates that the nonconsumptive effects of a recovering marine predator can indirectly elevate the survival of a basal food resource species.

Barking up which tree? Characterizing farmers, farms, and a behavioral framework regarding livestock guardian dog use in South Africa

Livestock guardian dogs are one of several predator control methods employed by livestock farmers around the world, but little is known about the factors that predict their use. Here we aim to understand the dimensions which influence guardian dog use by farmers. In a quantitative survey among 113 livestock farmers in South Africa, using Boosted Regression Trees, we explored and characterized the factors associated with guardian dog use. We showed that practical factors (e.g., predator type, number of farming enterprises, mitigation methods, and the frequency and extent of specific predator problems) were more likely to be significant determinants of guardian dog use than sociodemographic factors. However, psychosocial constructs relating to wildlife value orientations, empathy for predators, tolerance to predators, tangible and intangible cost, benefits of predators, like or dislike of predators, and number of positive experiences, were also determinants of guardian dog use. Utilizing the foundational constructs of the Theory of Planned Behavior (TPB) and Wildlife Tolerance Model (WTM) we built upon these findings to show that constructs of attitude, subjective norms, and perceived behavioral control explained 49 % of the variance in behavioral intention to use or continue using a guardian dog. The relationship between attitude and the behavioral intent to use or continue using a guardian dog had less significant association with guardian dog use than either perceived behavioral control or subjective norms had. Nonetheless, attitude was most strongly associated with the constructs of belief in a specific non-governmental organization, mutualistic Wildlife Value Orientations and perceptions of affordability, ease of use and the effectiveness of guardian dogs. The TPB model, incorporating elements of the WTM, provides a framework to guide and improve adoption of guardian dog programs or other intervention strategies within conservation contexts.

Ontogeny of color development in two green-brown polymorphic grasshopper species.

Many insects, including several orthopterans, undergo dramatic changes in body coloration during ontogeny. This variation is particularly intriguing in gomphocerine grasshoppers, where the green and brown morphs appear to be genetically determined (Schielzeth & Dieker, 2020, BMC Evolutionary Biology, 20, 63; Winter etal., 2021, Heredity, 127, 66). A better understanding of how these color morphs develop during ontogeny can provide valuable insights into the evolution and ecology of such a widespread color polymorphism. Here, we focus on the color development of two green-brown polymorphic species, the club-legged grasshopper Gomphocerus sibiricus and the steppe grasshopper Chorthippus dorsatus. By following the color development of individuals from hatching to adulthood, we found that color morph differences begin to develop during the second nymphal stage, are clearly defined by the third nymphal stage, and remain stable throughout the life of an individual. Interestingly, we also observed that shed skins of late nymphal stages are identifiable by color morphs based on their yellowish coloration, rather than the green that marks green body parts. Furthermore, by assessing how these colors are perceived by different visual systems, we found that certain potential predators can chromatically discriminate between morphs, while others may not. These results suggest that the putative genes controlling color morph are active during the early stages of ontogeny, and that green color is likely composed of two components, one present in the cuticle and one not. In addition, the effectiveness of camouflage appears to vary depending on the specific predator involved.

High importance of indirect evolutionary rescue in a small food web.

Evolutionary rescue may allow species to survive environmental change, but how this mechanism operates in food webs is poorly understood. Here, the evolutionary rescue was investigated in a small model food web, systematically allowing the evolution of each single species in order to reveal how its adaptation affects the persistence of itself and others. The impact of evolution was highly species-specific and not necessarily positive: only one species, the specialist predator, consistently had a positive impact on overall persistence. Most strikingly, evolution overwhelmingly affected other species: rescue of others (indirect rescue) was far more frequent than self-rescue, and negative effects were nearly always indirect. This demonstrates that evolutionary rescue in food webs is inextricably bound up with species interactions, as the effects of evolution in one species ripple through the entire community. It is therefore critically important to consider the food web context in efforts to understand how species may survive global change.

Phenology of Leucotaraxis argenticollis, a specialist predator of the invasive hemlock woolly adelgid, in the eastern United States.

In hemlock stands within eastern US forests, classical biological control has been one of the main strategies used to manage the hemlock woolly adelgid, Adelges tsugae Annand. Specialist predator species may offer a management solution to help regulate A. tsugae populations. In the Pacific Northwest, a suite of specialist predators has been a focus of research and includes 2 species of silver fly, Leucotaraxis argenticollis (Zetterstedt) and Leucotaraxis piniperda (Malloch) (Diptera: Chamaemyiidae). Leucotaraxis spp. phenology has been documented in the Pacific Northwest, but the phenology of either western Leucotaraxis species is unknown in the eastern United States. This study sought to document the phenology of Le. argenticollis in NY in 2021 and in VA in 2021 and 2022. Nylon mesh cages were applied over eastern hemlock branches infested with A. tsugae to contain Le. argenticollis adults. Biweekly and monthly branch samples were taken in 2021 and 2022, documenting all life stages of A. tsugae and of Le. argenticollis that were observed. In 2021 and 2022, Le. argenticollis adults and eggs were present during the oviposition stage of the 2 generations of A. tsugae. In addition, Le. argenticollis larvae were present when A. tsugae ovisacs had eggs and while A. tsugae nymphs of both generations were present. These observations indicate that Le. argenticollis phenology is well synchronized with A. tsugae in the eastern United States.

Golden mimics use multiple defenses to counter generalist and specialist predators

Abstract Many prey species employ multiple defenses during interactions with predators. Multiple defenses can provide a selective advantage against a single predator at different stages of the interaction or attack, as well as against multiple predator types. However, the efficacy of multiple defenses both during different sequences of an attack and against multiple predator types, remains poorly understood. We measured and classified defensive traits used by five mimics (Müllerian and Batesian) of the myrmecomorphic golden mimicry complex and one non-mimetic species. We then performed predatory trials using two different predators that differed markedly in their body size, trophic specialization, and how they handle prey—one being an ant specialist (spider) and the other a generalist which avoided ants (skink). We identified 12 defensive traits and classified them into four groups (primary, chemical, mechanical, and behavioral), which were strongly correlated. Skinks were much less likely to attack and capture mimics than the ant-eating spider predators. Our results show that multiple defenses (five or six) were used against each predator. The defensive behaviors and features that were most effective against skinks included appendage waving and large body size, whereas the golden “shine” warning signal, large body size, cuticle thickness, and defensive gland size were most effective against spiders. Most defenses appeared to be predator-specific. We conclude that potential prey in the golden mimicry complex have been selected for multiple defenses because of their vulnerability to different predator types and consequently, the efficacy of some of these defenses likely represents a trade-off.

Expression and function analyses of sex-lethal gene in Phytoseiulus persimilis

Phytoseiulus persimilis is a specialist predator of spider mites, with promising control effects. Its population generally has a stable sex ratio. Under appropriate conditions, the proportion of female offspring can reach 80%. But the mechanisms of sex determination in P. persimilis is still unclear. Sex-lethal (sxl) is an important gene in studying sex regulation mechanisms in insects. In the model organism Drosophila melanogaster, it has been proved to be a switch controlling sex determination. Herein, we screened one sex-lethal gene ortholog in the genome of P. persimilis (Ppsxl). We separated male and female offspring successfully based on the order of the egg laid, and found Ppsxl is expressed in both sexes at different stages. The expression peak was found in females 10 h after mating, and it was also highly expressed in eggs that developed into males. RNA interference was used to study the function of Ppsxl. When Ppsxl was interfered, all female individuals remained fertile. However, their cumulative fecundity decreased by 18.0%, daily fecundity decreased by 13.4%, and the proportion of female offspring decreased by 22.7%. This study showed that Ppsxl gene has a certain influence on the reproduction of P. persimilis, but its influence on sex determination may not be as critical as that in D. melanogaster. The regulation of sxl on P. persimilis was different from that in D. melanogaster.

Diet analyses of the pelagic thresher shark, Alopias pelagicus (Lamniformes: Alopiidae), from the Lombok Strait waters, Indonesia

Abstract. Alghozali FA, Salsabila R, Gustianto MWD, Putri HMIH, Himawan MR, Yuneni RR, Hatmoro CK, Rezkiani M. 2023. Diet analyses of the pelagic thresher shark, Alopias pelagicus (Lamniformes: Alopiidae), from the Lombok Strait waters, Indonesia. Biodiversitas 24: 3708-3714. The pelagic thresher shark, Alopias pelagicus, is an endangered shark species estimated to be declining in the Pacific and Indian Oceans because of overexploitation, including from target fisheries and bycatch. Despite its importance in providing better information for species management, the ecological aspects of this species are still rarely studied. This study aims to provide information on the feeding ecology of the pelagic thresher sharks from the Lombok Strait. Stomach samples from 178 specimens were sampled from 2020-2021, and 149 stomachs that contained food contents were analyzed for species diet characterization. Prey Species Accumulation Curve slope values are <0.1 and the percentage of prey coverage for all sharks combined is 92.1%, suggesting reliable inventory in the number of prey represented. The resulting diet indexes suggest that A. pelagicus in Lombok Strait waters is a specialist predator (Ba=0.3) with few prey variations (H=2.21) and no competition between sexes and maturity stages of the species (C=0.64 and 0.81, respectively). The top three prey species found for A. pelagicus in the study area are the Auxis thazard (85.8 %IRI), Sthenoteuthis oualaniensis (8.5 %IRI), and Dasyscopelus spinosus (1.11 %IRI). A better understanding of the overlap of A. pelagicus and its diet, which includes economic fish commodities, will inform authorities to develop better fisheries and conservation management for the species in Indonesia.

Canada lynx foraging strategies: Facultative specialists become obligate generalists toward the distribution edge

AbstractSpatial and temporal variation in prey availability can affect predator foraging strategies, but it is unclear how large‐scale gradients in prey availability shape predator diets in space and time. The facultative specialist hypothesis predicts that niche expansion by specialist predators is advantageous when preferred prey are limited and alternate prey are available, as might be expected following the collapse of primary prey populations in species‐poor environments or at range margins where species assemblages shift. Canada lynx (Lynx canadensis) are broadly distributed and prey predominantly on snowshoe hares (Lepus americanus), with other species serving as alternate prey when hares are limited. We used stable isotope analysis of lynx, snowshoe hare, and red squirrel hair during periods of high/low snowshoe hare availability from five regions throughout their distribution, to measure spatiotemporal changes in diet and test the facultative specialist hypothesis. Hares were the primary food item in all lynx diets, irrespective of space and time. Core lynx populations consumed the greatest proportion of hares overall and increased the use of alternate prey when hares were limited. Despite fluctuations in hare availability, lynx toward the southeastern extent of their distribution invariably consumed alternate prey in similar proportions to those exhibited by core populations during hare lows. The temporal consistency of lynx diets in these regions indicates that broader diets are obligate along this distribution edge. Our results provide new evidence for the facultative specialist hypothesis across a broad spatial scale and emphasize that, as specialist–generalist paradigms operate along a continuum, so too can obligate–facultative strategies depending on environmental context.

Intraguild Prey Served as Alternative Prey for Intraguild Predators in a Reciprocal Predator Guild between Neoseiulus barkeri and Scolothrips takahashii

The predatory mites Neoseiulus barkeri (Hughes) and the predatory thrips Scolothrips takahashii (Priesner) are known as potential biocontrol agents for the two-spotted spider mite Tetranychus urticae (Koch). These two predator species occur simultaneously on crops in agricultural ecosystems and are proved to be involved in life-stage specific intraguild predation. The intraguild prey may play a role in securing the persistence of the intraguild predators during food shortage periods. To understand the potential of intraguild prey as food source for intraguild predators in the N. barkeri and S. takahashii guild at low T. urticae densities, the survival, development and reproduction of both predators was determined when fed on heterospecific predators. The choice tests were conducted to determine the preference of the intraguild predator between the intraguild prey and the shared prey. Results showed that 53.3% N. barkeri and 60% S. takahashii juveniles successfully developed when fed on heterospecific predators. Female intraguild predators of both species fed on intraguild prey survived and laid eggs throughout the experiment. In the choice test, both intraguild predator species preferred their extraguild prey T. urticae. This study suggested that intraguild prey served as an alternative prey for intraguild predators prolonged survival and ensured the reproduction of intraguild predators during food shortage, ultimately decreasing the need for the continual release of the predators.

Trophic chain of the pelagic thresher, Alopias pelagicus, in the Southeastern Pacific Ocean: An approach through stable isotopes of carbon and nitrogen

The pelagic thresher, Alopias pelagicus, plays a vital role in coastal and marine ecosystems as a top predator that feeds on species from low trophic levels. It is a commercial species relevant in Ecuador. The feeding chain of A. pelagicus was analyzed through carbon and nitrogen stable isotopes in the Southeast Pacific Ocean. Considering the lack of studies regarding this topic, this would elucidate the flow of nutrients and energy from the base up to this predator. Its diet composition included 19 prey species, out of which 10 were cephalopods and nine Osteichthyes. The most relevant species were the squid Ommastrephes bartramii, Dosidicus gigas, Stenoteuthis oualaniensis, and the fish Merluccius gayi peruanus. The pelagic thresher is a carnivore predator, and its prey species belong to tertiary and quaternary trophic levels. The carbon and nitrogen male isotopic ratios were similar to those of females, as were immature and mature organisms. This suggests that this species feeds in oceanic regions of low depths and could be exploiting and sharing an area with similar feeding resources. According to the mixing models, squids were the most important prey group, in which the squid Ommastrephes bartramii contributed most to its diet. Furthermore, this shark was characterized as a specialist predator with a trophic overlap by sex and maturity stages.

Updating integrated mite management fifty years later: comparing laboratory pesticide susceptibility of a "new" generalist predatory mite to a cornerstone specialist predator.

Historically, integrated mite management in Washington apple orchards has focused on the conservation of the predatory mite Galendromus occidentalis (Nesbitt) to reduce secondary pest mite pressure. However, pesticide use has changed to include more selective products, coinciding with a shift in the predatory mite community composition to include a new major predator, Amblydromella caudiglans (Schuster). There is evidence that A. caudiglans is more pesticide sensitive than G. occidentalis. Therefore, updates on pesticide selectivity recommendations are needed to conserve this "new" key predator. Using bioassays, we examined lethal (female mortality) and sublethal effects (fecundity, egg hatch, larval survival) of four fungicides and 11 insecticides on A. caudiglans, to determine if existing conservation recommendations can be applied to this predatory mite. Susceptibility was compared to prior research on G. occidentalis. Mancozeb was the least selective fungicide tested on A. caudiglans; it caused high acute toxicity and sublethal effects. Carbaryl was the least selective insecticide and caused 100% mortality. Captan was the most selective fungicide. Chlorantraniliprole and cyantraniliprole were the most selective insecticides and therefore least likely to disrupt biological control by A. caudiglans. Non-target effects on A. caudiglans and G. occidentalis were similar, but A. caudiglans experienced higher mortality to some broad-spectrum insecticides. All products tested had some non-target effects on A. caudiglans. However, A. caudiglans sensitivity to most tested pesticides was similar to G. occidentalis. In general, existing spray recommendations for conserving G. occidentalis can be adjusted slightly and applied to A. caudiglans conservation. This article is protected by copyright. All rights reserved.