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Prior work suggests perceived COVID-19-related threat and existential isolation (EI) would be associated with greater anxiety and depression, worse subjective health and well-being, and lower hope. However, it was unclear whether such concerns might have additive effects (no interaction, two independent main effects) or interact (one effect modifies the other). Two studies collected data via MTurk during the COVID-19 pandemic. Study 1 (N = 110) measured perceived COVID19-related threat, EI, anxiety and depression, subjective well-being, and hope. Study 2 (N = 2,673) measured perceived COVID19-related threat, EI, anxiety, subjective health, and hope. In general, perceived COVID19-related threat and EI were associated with anxiety and depression, worse subjective health and well-being, and reduced hope. On one outcome (hope, Study 2), an interaction was observed: perceived threat was associated with lower hope among those with high EI, but higher hope among those with low EI. However, on most outcomes (6 of 7), across both studies, additive effects were observed: greater cumulative existential stress (perceived COVID-19-related threat, EI) was associated with worse anxiety and depression, subjective health and well-being, and hope. Discussion highlights theoretical considerations, practical implications, and the therapeutic value of addressing existential concerns in mental health. What is already known about this topic:Prior work found perceived COVID-19-related threat and other death-related existential concerns were related to anxiety, depression, and undermined well-being and hopeful engagement.Prior work found existential isolation was related to anxiety, depression, and undermined well-being.COVID-19-related threat was associated with worse anxiety, depression, and well-being, but not subjective health or hope. Prior work found perceived COVID-19-related threat and other death-related existential concerns were related to anxiety, depression, and undermined well-being and hopeful engagement. Prior work found existential isolation was related to anxiety, depression, and undermined well-being. COVID-19-related threat was associated with worse anxiety, depression, and well-being, but not subjective health or hope. What this topic adds:EI was consistently associated with worse anxiety and depression, subjective health and well-being, and reduced hope.In one outcome (hope, Study 2), an interaction found that perceived COVID-19-related threat decreased hope when people felt existentially isolated, but increased hope when people felt a sense of existential connection (e.g., “we’re all in this together”).However, on six of seven outcomes, across two studies, additive effects were observed such that the more existential stress (COVID-19-related threat, existential isolation) experienced the worse the outcome. EI was consistently associated with worse anxiety and depression, subjective health and well-being, and reduced hope. In one outcome (hope, Study 2), an interaction found that perceived COVID-19-related threat decreased hope when people felt existentially isolated, but increased hope when people felt a sense of existential connection (e.g., “we’re all in this together”). However, on six of seven outcomes, across two studies, additive effects were observed such that the more existential stress (COVID-19-related threat, existential isolation) experienced the worse the outcome.

Cowpea (Vigna unguiculata) is one of the most important crops in semiarid areas of the world, where it thrives in hot, dry conditions. While cowpea is able to withstand abiotic stresses, it suffers serious losses from biotic antagonists, including infestation by the cowpea aphid (Aphis craccivora). Cowpea aphid infestations are highly destructive, especially on young plants. However, it is unclear whether cowpea aphid damage is the result of aphids having phytotoxic effects on their hosts, or simple density effects. To better understand cowpea aphid damage and the potential for resistance traits to mitigate aphid impacts, we evaluated phenotypic changes in cowpea in response to variable aphid densities and systemic versus local infestations. Low aphid densities induced leaf distortions and pseudogalling, suggesting that cowpea aphids are phytotoxic to cowpea. Resistance to the cowpea aphid has been previously identified in an African cowpea germplasm, and near isogenic lines (NILs) containing resistance quantitative trait loci (QTL) were generated in the California blackeye cultivar background. Using a series of performance assays, we determined that resistance conferred by the two QTL counteracts aphid phytotoxicity and severely limits aphid growth and fecundity. Using choice assays, a preference by cowpea aphids for the susceptible NIL was observed. Electrical penetration graph analysis revealed that the resistance phenotype includes weak surface level deterrence and strong phloem based resistance that manifests during the sap ingestion phase. Our study provides evidence of phytotoxic traits in A. craccivora while identifying a viable means of counteracting aphid damage and reproductive potential through resistance.

The extensive land use conversion expected to occur to meet demands for bioenergy feedstock production will likely have widespread impacts on agroecosystem biodiversity and ecosystem services, including carbon sequestration. Although arthropod detritivores are known to contribute to litter decomposition and thus energy flow and nutrient cycling in many plant communities, their importance in bioenergy feedstock communities has not yet been assessed. We undertook an experimental study quantifying rates of litter mass loss and nutrient cycling in the presence and absence of these organisms in three bioenergy feedstock crops-miscanthus (Miscanthus x giganteus), switchgrass (Panicum virgatum), and a planted prairie community. Overall arthropod abundance and litter decomposition rates were similar in all three communities. Despite effective reduction of arthropods in experimental plots via insecticide application, litter decomposition rates, inorganic nitrogen leaching, and carbon-nitrogen ratios did not differ significantly between control (with arthropods) and treatment (without arthropods) plots in any of the three community types. Our findings suggest that changes in arthropod faunal composition associated with widespread adoption of bioenergy feedstock crops may not be associated with profoundly altered arthropod-mediated litter decomposition and nutrient release.