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1. Salinity Influences Plant–Pest–Predator Tritrophic Interactions

   https://doi.org/10.1093/jee/toab133  

   Ali, M P ; Rahman, M S ; Nowrin, Farzana ; Haque, S S ; Qin, Xinghu ; Haque, M A ; Uddin, M M ; Landis, Douglas A ; Howlader, M T ( July 2021 , Journal of Economic Entomology)

   Eigenbrode, Sanford (Ed.)

   Abstract Climate change-induced salinity intrusion into agricultural soils is known to negatively impact crop production and food security. However, the effects of salinity increase on plant–herbivore–natural enemy systems and repercussions for pest suppression services are largely unknown. Here, we examine the effects of increased salinity on communities of rice (Oryza sativa), brown planthopper (BPH), Nilaparvata lugens, and green mirid bug (GMB), Cyrtorhinus lividipennis, under greenhouse conditions. We found that elevated salinity significantly suppressed the growth of two rice cultivars. Meanwhile, BPH population size also generally decreased due to poor host plant quality induced by elevated salinity. The highest BPH density occurred at 2.0 dS/m salinity and declined thereafter with increasing salinity, irrespective of rice cultivar. The highest population density of GMB also occurred under control conditions and decreased significantly with increasing salinity. Higher salinity directly affected the rice crop by reducing plant quality measured with reference to biomass production and plant height, whereas inducing population developmental asynchrony between BPH and GMB observed at 2 dS/m salinity and potentially uncoupling prey–predator dynamics. Our results suggest that increased salinity has harmful effects on plants, herbivores, natural enemies, as well as plant–pest–predator interactions. The effects measured here suggest that the bottom-up effects of predatory insects on rice pests will likely decline in rice produced in coastal areas where salinity intrusion is common. Our findings indicate that elevated salinity influences tritrophic interactions in rice production landscapes, and further research should address resilient rice insect pest management combining multipests and predators in a changing environment. 

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2. Plant damage in urban agroecosystems varies with local and landscape factors

   https://doi.org/10.1002/ecs2.3074  

   Egerer, Monika ; Liere, Heidi ; Lucatero, Azucena ; Philpott, Stacy M. ( March 2020 , Ecosphere)

   Biotic and abiotic factors at local to landscape scales influence insect pest and disease dynamics in agricultural systems. However, relative to studies focused on the importance of these drivers of crop plant damage in rural agricultural systems, few studies investigate plant damage from herbivore insects and plant diseases in urban agroecosystems, and consequently, most urban farmers lack knowledge on crop protection tactics. Here we use three common crop species within urban agroecosystems (community gardens) distributed across an urban landscape as a model system to ask how local, landscape, and microclimate factors relate to herbivore and disease plant damage. We hypothesized that plant damage would be lower in gardens with greater local vegetation complexity, landscape‐scale complexity, and less variable temperatures, but that the importance of factors is species‐ and damage‐specific. By measuringBrassica, cucurbit, and tomato insect pest and disease damage across the growing season, we confirmed that the importance of factors varies with crop species and by damage type. Both local complexity factors (e.g., number of trees and shrubs) and landscape complexity (percent natural cover in the landscape) relate to lower incidence of herbivore and disease damage on some crops, supporting our prediction that habitat heterogeneity at both local and landscape scales lowers plant damage. Greater temperature variability related to higher disease damage on tomatoes linking microclimate factors to disease prevalence. Yet, local complexity factors also related to higher incidence of plant damage for other crop species, indicating variable species‐level impacts of local management factors on plant damage. By measuring the abundance of fungus‐feeding lady beetles (Psyllobora) on cucurbits, we confirmed a strong association between natural enemies and powdery mildew. We provide a case study on how changes in local to landscape‐scale factors relate to plant damage in urban agroecosystems and suggest how urban farmers and gardeners can apply this ecological knowledge to improve sustainable urban food production.

    

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3. Multiscale habitat mediates pest reduction by birds in an intensive agricultural region

   https://doi.org/10.1002/ecs2.2884  

   Heath, Sacha K. ; Long, Rachael F. ( October 2019 , Ecosphere)

   Habitat augmentation on farms is predicted to conserve biological diversity and support beneficial animals that reduce crop pests. Effectiveness of local habitat enhancement and subsequent pest reduction services can be mediated by the amount of habitat at larger scales. We tested whether the presence and increase of local and landscape scale bird habitat increased avian predator abundance and pest reduction by birds. We surveyed birds and performed a sentinel prey exclosure experiment in walnut orchards in the Sacramento Valley, California,USA—comparing predation probability between orchards with (n = 10) and without (n = 10) woody habitat in uncultivated orchard margins. We digitized seminatural habitat cover in landscapes around orchards to test the effectiveness of avian predators in reducing sentinel prey along a seminatural cover gradient of 0–38%. Experimental prey were diapausing larvae ofCydia pomonella(L.) (Lepidoptera: Tortricidae; codling moth), a significant pest of walnuts, which overwinter in cocoons in orchards, emerge as adults, and produce larvae that feed on the nuts the following spring. Permitting bird access to cocoons increased larval predation from 11% (caged) to 46% (no cage), and predation increased with increasing proportions of seminatural habitat within 500‐m of orchard transects. Predation also increased as the size and bark furrow depth of walnut trees increased, likely because these characteristics were associated with increasing abundance of avian predators with functional traits specific to consuming tree‐dwelling cocoons (e.g., woodpeckers). The presence and increasing complexity of local margin habitat increased the species richness and abundance of avian predators but was not predictive of cocoon predation. Consistent with intermediate landscape‐complexity hypothesis predictions, the effect size of woodpecker abundance on predation was large in simple landscapes (1–20% seminatural cover) and low in complex landscapes (>20% cover). Contrary to predictions, effect size was large in cleared landscapes (<1% cover), suggesting that orchards supported predators in cleared landscapes, with positive effects on pest reduction. We provide evidence that increasing the abundance of avian predators with traits specific for consuming target pests—by retaining old trees and seminatural cover—can increase orchard pest reduction services in an intensive agricultural region.

    

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4. Crowdsourced online images provide insights into predator-prey interactions of putative natural enemies

   https://doi.org/10.1016/j.fooweb.2019.e00126  

   Hernandez, Madison ; Masonick, Paul ; Weirauch, C. ( January 2019 , Food webs)

   Most megadiverse clades of insects are herbivores, but several large radiations consist almost entirely of predators. Their species numbers make comprehensive direct observations of predator-prey interactions difficult to obtain. Citizen science approaches are increasingly utilized to harvest ecological data for organisms including insects. We use crowdsourced images documenting predator-prey interactions of assassin bugs (Hemiptera: Reduviidae), a speciose clade of predatory insects, to (1) determine the breakdown of assembled online images by geographic region and reduviid subfamily; (2) evaluate if the accumulated images provide new insights into prey diversity; and (3) assess evidence for taxa that feed on pest species, pollinators, and engage in intraguild predation. Photographs were assembled (n = 832) and resulted in an image database that included representatives of 11 subfamilies; most records belonged to diurnal Harpactorinae and Phymatinae, but some subfamilies with poorly understood prey diversity were also documented. Taxa with substantial image representation of prey (21–242 predation events) showed significant overlap with prey reported in the literature. A high percentage of images for Apiomerus Hahn and Phymata Latreille documented predation events on native and non-native bees; percentages varied widely among species of Zelus Fabricius. Arilus cristatus (Linnaeus) was documented to prey on several pest species, with little evidence for pollinator predation. Potential effects of these natural enemies on pollinators and intraguild predators should be further investigated, providing important insights into mechanisms influencing community structure and ecosystems processes. 

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5. An aggressive nonconsumptive effect mediates pest control and multipredator interactions in a coffee agroecosystem

   https://doi.org/10.1002/eap.2653  

   Morris, Jonathan R. ; Perfecto, Ivette ( June 2022 , Ecological Applications)

   Natural pest control is an alternative to pesticide use in agriculture, and may help to curb insect declines and promote crop production. Nonconsumptive interactions in natural pest control that historically have received far less attention than consumptive interactions, may have distinct impacts on pest damage suppression and may also mediate positive multipredator interactions. Additionally, when nonconsumptive effects are driven by natural enemy aggression, variation in alternative resources for enemies may impact the strength of pest control. Here we study control of the coffee berry borer (CBB),Hypothenemus hampei, by a keystone arboreal ant species,Azteca sericeasur, which exhibits a nonconsumptive effect on CBB by throwing them off coffee plants. We conducted two experiments to investigate: (1) if the strength of this behavior is driven by spatial or temporal variability in scale insect density (an alternative resource thatAztecatends for honeydew), (2) if this behavior mediates positive interactions betweenAztecaand other ground‐foraging ants, and (3) the effect this behavior has on the overall suppression of CBB damage in multipredator scenarios. Our behavioral experiment showed that nearly all interactions betweenAztecaand CBB are nonconsumptive and that this behavior occurs more frequently in the dry season and with higher densities of scale insects on coffee branches. Our multipredator experiment revealed that borers thrown off coffee plants byAztecacan survive and potentially damage other nearby plants but may be suppressed by ground‐foraging ants. Although we found no non‐additive effects betweenAztecaand ground‐foraging ants on overall CBB damage, together, both species resulted in the lowest level of plant damage with the subsequent reduction in “spillover” damage caused by thrown CBB, indicating spatial complementarity between predators. These results present a unique case of natural pest control, in which damage suppression is driven almost exclusively by nonconsumptive natural enemy aggression, as opposed to consumption or prey behavioral changes. Furthermore, our results demonstrate the variability that may occur in nonconsumptive pest control interactions when natural enemy aggressive behavior is impacted by alternative resources, and also show how these nonconsumptive effects can mediate positive interactions between natural enemies to enhance overall crop damage reduction.

    

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