Locusts are grasshoppers (Orthoptera: Acrididae) that are characterised by their capacity for extreme population density-dependent polyphenism, transforming between a cryptic solitarious phase that avoids other locusts, and a swarming gregarious phase that aggregates and undergoes collective migration. The two phases differ in many aspects of behaviour, physiology and ecology, making locusts a useful model through which to investigate the phenotypic interface of molecular processes and environmental cues. This review summarises recent progress in understanding the mechanisms and consequences of locust phase change, from differential gene expression and epigenetic regulation through to neuronal plasticity and altered behaviour. The impact of techniques such as RNA interference (RNAi), and the sequencing of the first locust genome is discussed, and we consider the evidence from comparative analyses between related locust species for the possible evolution of locust-like phenotypic plasticity. Collective movement, and new ways of measuring the behaviour of both migrating bands in the field and individuals in the laboratory, are analysed. We also examine the environmental factors that affect phase change, along with the wider impact of land use and management strategies that may unwittingly create environments conducive to outbreaks. Finally, we consider the human costs of locust swarming behaviour, and use combined social, economic and environmental approaches to suggest potential ways forward for locust monitoring and management.

Minnesota was dubbed the ‘raspberry consumption capital of America’ in 2017 by wholesaler Driscoll’s, Inc. Local production of this high-demand fruit, however, is limited by the invasive pest, spotted wing Drosophila (Drosophila suzukii Matsumura, Diptera: Drosophilidae). Recent research to develop integrated pest management (IPM) programs for MN berry crops indicates that raspberry growers are particularly vulnerable to significant spotted wing Drosophila-related yield losses. Spotted wing Drosophila was detected in Minnesota in 2012 across 29 counties. This analysis explores the economic impact of raspberry yield losses associated with spotted wing Drosophila in Minnesota as part of a multifaceted research initiative. An electronic survey of 157 MN berry growers was conducted in November 2017. Eighty-two individual grower surveys were returned (52% response rate). The survey included questions about production acreage, marketing practices, spotted wing Drosophila-related yield losses and future production intentions. The results of the e-survey indicate that raspberry growers have borne the highest levels of infestation among MN fruit growers surveyed. Spotted wing Drosophila-related yield losses for raspberry growers ranged from 2 to 100% of planted acreage.The median yield loss for this group of growers was 20% in 2017. Applying the median yield loss to ex-ante production estimates, we conclude that MN growers lost approximately $2.36 million in raspberry sales during the 1 yr studied. Investing in spotted wing Drosophila control measures will help MN growers reduce some of these losses in the future.

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Coupled human and natural systems (CHANS) are systems of feedback linking people and ecosystems. A feature of CHANS is that this ecological feedback connects people across time and space. Failing to account for these dynamic links results in intertemporal and spatial externalities, reaping benefits in the present but imposing costs on future and distant people, such as occurs with overgrazing. Recent findings about locust-nutrient dynamics create new opportunities to address spatiodynamic ecosystem externalities and develop new sustainable strategies to understand and manage locust outbreaks. These findings in northeast China demonstrate that excessive livestock grazing promotes locust outbreaks in an unexpected way: by lowering plant nitrogen content due to soil degradation. We use these human-locust-livestock-nutrient interactions in grasslands to illustrate CHANS concepts. Such empirical discoveries provide opportunities to address externalities such as locust outbreaks, but society's ability to act may be limited by preexisting institutional arrangements.