David W. Crowder's research while affiliated with Washington State University and other places
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Publications (197)
In 2021 and 2022, virus-like symptoms were observed in several cultivars of industrial hemp (Cannabis sativa) in two fields in central Washington, USA. Affected plants had a range of symptoms at different developmental stages, with young plants having severe stunting with shortened internodes and reduced flower mass. Young leaves of infected plants...
Viral insect‐borne plant pathogens have devastating impacts in agroecosystems. Vector‐borne pathogens are often transmitted by generalist insects that move between non‐crop and crop hosts. Insect vectors can have wide diet breadths, but it is often unknown which hosts serve as pathogen reservoirs and which non‐crop host harbours the highest density...
Insect pollinators are declining globally as a result of the anthropogenic pressures that have destroyed native habitats and eroded ecosystems. These declines have been associated with agricultural productivity losses, threatening food security. Efforts to restore habitat for pollinators are underway, emphasizing large-scale habitat creation like w...
Human sewage can introduce pollutants into food webs and threaten ecosystem integrity. Among the many sewage-associated pollutants, pharmaceuticals and personal care products (PPCPs) are useful indicators of sewage in ecosystems and can also cause potent ecological consequences even at minute concentrations (e.g., ng/L). Despite increased study ove...
Transmission of insect-borne pathogens is mediated by interactions between insects and plants across variable environments. Water stress, for example, affects the physiology, defense, chemistry, and nutritional balance of plants in ways that alter their tolerance to herbivores and pathogens. However, few studies have explored interactions between w...
Abstract Flowering crops are heavily managed during bloom to both promote pollination and prevent disease. Disease management practices can alter the floral microbiome, including pathogens and non‐target microbes. However, whether agrochemical presence or altered microbiome composition affect pollinator foraging and pollination services is unclear....
Managers of insect-pollinated orchards face many decisions that can significantly influence crop yields, including managing pollination through use of beehives or the layout of cultivars in the orchard. Understanding the relative importance and interactions between these multiple decisions through empirical field trials is rarely possible, so model...
Background:
Invasive species threaten the productivity and stability of natural and managed ecosystems. Predicting the spread of invaders, which can aid in early mitigation efforts, is a major challenge, especially in the face of climate change. While ecological niche models are effective tools to assess habitat suitability for invaders, such mode...
Pollination involves complex interactions between plants and pollinators, and variation in plant or pollinator biology can lead to variability in pollination services that are difficult to predict. Models that effectively predict pollination services could enhance the ability to conserve plant-pollinator mutualisms in natural systems and increase c...
Biological control programs frequently rely on insect predators to control pests that vector plant pathogens in agroecosystems. Predators affect vectors by eating them (consumptive effects) and by inducing antipredator behaviors (non-consumptive effects), and these interactions may affect transmission of vector-borne pathogens. However, it has prov...
Soil bacteria that associate with plant roots promote host vigor. Legume plants form mutualisms with rhizobial bacteria, and legumes grown with rhizobia have more nutrients and defenses than those grown without rhizobia. However, few studies have tested how stressors such as herbivores affect soil rhizobia, and the mechanisms mediating these intera...
Sustainable agroecosystems provide adequate food while supporting environmental and human wellbeing and are a key part of the United Nations Sustainable Development Goals (SDGs). Some strategies to promote sustainability include reducing inputs, substituting conventional crops with genetically modified (GM) alternatives, and using organic productio...
Drought alters plant traits in ways that affect herbivore performance. However, we lack a comprehensive understanding of the plant-derived mechanisms that mediate insect responses to drought. Water stress occurs along gradients of intensity, and the impacts of drought intensity on plant-insect interactions is understudied. Here, we assessed aphid p...
Seventy five percent of the world's food crops benefit from insect pollination. Hence, there has been increased interest in how global change drivers impact this critical ecosystem service. Because standardized data on crop pollination are rarely available, we are limited in our capacity to understand the variation in pollination benefits to crop y...
Generalist predators’ complex feeding relationships make it difficult to predict their contribution to pest suppression. Alternative prey can either distract predators from attacking pests, weakening biocontrol, or provide food that support larger predator communities to enhance it. Similarly, predator species might both feed upon and complement on...
Background:
Generalist predators that kill and eat other natural enemies can weaken biological control. However, pest suppression can be disrupted even if actual intraguild predation is infrequent, if predators reduce their foraging to lower their risk of being killed. In turn, predator-predator interference might be frequent when few other prey a...
Long-term monitoring networks that generate data on pest abundance are the foundation of integrated pest management. Monitoring can estimate local risk from pests and identify when pests first arrive in particular fields. However, while data on pest abundance are collected for the purpose of making management decisions in individual fields, it is o...
Auchenorrhyncha (Hemiptera) includes several families of sap-feeding insects that tend to feed on a wide-range of host plants. Some species within Auchenorrhyncha are major agricultural pests that transmit plant pathogens or cause direct feeding damage. Nearly all pest Auchenorrhyncha are highly polyphagous, have mobile nymphs, and colonize crops f...
The abundance and diversity of pollinator populations are in global decline. Managed pollinator species, like honey bees, and wild species are key ecosystem service providers in both natural and managed agroecosystems. However, relatively few studies have exhaustively characterized pollinator populations in diverse agroecosystems over multiple year...
Agricultural diversification often promotes biodiversity and ecosystem services by increasing habitat diversity. However, responses to agricultural diversification are context dependent, differentially impacting functional groups of service-providing organisms and crop yields.
Conservation and no tillage are promoted as agricultural diversification...
Bees are key pollinators that promote greater yield and seed quality of oilseed crops such as canola. Canola acreage has increased over 1,000% in the past decade in the Pacific Northwest USA, providing a major pulse of sugar-rich nectar and pollen resources that may affect bee health and community structure. However, because canola does not require...
Global efforts to assess honey bee health show viruses are major stressors that undermine colony performance. Identifying factors that affect virus incidence, such as management practices and landscape context, could aid in slowing virus transmission. Here we surveyed viruses in honey bees from 86 sites in the Pacific Northwest, USA, and tested eff...
Wild bee communities persist in cities despite major disruption of nesting and food resources by urban development. Bee diversity and abundance is key for urban agriculture and maintenance of plant diversity, and assessing what aspects of cities enhance bee populations will promote our capacity to retain and provision bee habitat. Here, we assessed...
Global efforts to assess honey bee health show viruses are major stressors that undermine colony performance. Identifying factors that affect virus incidence, such as management practices and landscape context, could aid in slowing virus transmission. Here we surveyed viruses in honey bees from 86 sites in the Pacific Northwest, USA, and tested eff...
Accurately predicting the distribution of emerging invasive species is crucial for early detection and eradication. While ecological niche models are often used to forecast invasions, such models are limited when invasive populations of a species have realized niches that differ from native populations, or when invasive populations are not at equil...
Plants are often attacked by multiple antagonists, and traits of the attacking organisms, and their order of arrival onto hosts, may affect plant defenses. However, few studies have assessed how multiple antagonists, and varying attack order, affect plant defense or nutrition. To address this, we assessed defensive and nutritional responses of Pisu...
Herbivores assess predation risk in their environment by identifying visual, chemical, and tactile predator cues. Detection of predator cues can induce risk-avoidance behaviors in herbivores that affect feeding, dispersal, and host selection in ways that minimize mortality and reproductive costs. For herbivores that transmit plant pathogens, includ...
Ecological theory predicts that host-plant traits affect herbivore population growth rates, which in turn modulates predator–prey interactions. However, while vector-borne plant pathogens often alter traits of both host plants and vectors, a few studies have assessed how pathogens may act as interaction modifiers within tri-trophic food webs. By ap...
BACKGROUND
Biological control by generalist predators can be mediated by the abundance and biodiversity of alternative prey. When alternative prey draw predator attacks away from the control target, they can weaken pest suppression. In other cases, a diverse prey base can promote predator abundance and biodiversity, reduce predator–predator interfe...
Wireworms are the larval stage of click beetles (Coleoptera: Elateridae), and some of their species are serious pests of many crops. In the present study, we evaluated the efficacy of naturally occurring and commercial entomopathogenic nematode species against the sugar beet wireworm, Limonius californicus (Mannerheim), in the laboratory. First, ef...
Crop-associated microbiota are key factors affecting host health and productivity. Most crops are grown within heterogeneous landscapes, and interactions between management practices and landscape context often affect plant and animal biodiversity in agroecosystems. However, whether these same factors typically affect crop-associated microbiota is...
Current global nutrient availability poses a barrier to the complete shift from conventional to organic food production. Policies must be developed to overcome nutrient limitation and increase grower experience with organic production methods.
Beneficial plant-associated soil microbes can promote plant tolerance to stress and promote nutrient uptake. Yet, the benefits of microbes for plant health can be altered by aboveground stressors like herbivores and pathogens. However, few studies have assessed reciprocal plant-mediated interactions between beneficial soil microbes and multiple abo...
Grasslands are globally imperilled ecosystems due to widespread conversion to agriculture and there is a concerted effort to catalogue arthropod diversity in grasslands to guide conservation decisions. The Palouse Prairie is one such endangered grassland; a mid-elevation habitat found in Washington and Idaho, United States. Ants (Formicidae) are us...
Crop diversification often promotes farm sustainability. However, proper management of newly introduced crops is difficult when pests are unknown. Characterizing herbivore dynamics on new crops, and how they respond to agronomic factors, is crucial for integrated pest management. Here we explored factors affecting Lygus spp. (Hemiptera: Miridae) he...
Natural enemies often move among habitats to track prey and resources. Indeed, biocontrol often depends on natural enemies dispersing into crops after disturbances such as tillage and pesticide applications. However, the small size of many natural enemies makes it difficult to observe such movements. Here we used genetic relatedness among entomopat...
Greater arthropod diversity may promote biological control by bringing together predator species that occupy complementary feeding niches. Diverse prey communities could further accentuate such niche differences and decrease predator-predator antagonism. However, much evidence of these effects comes from simple experiments that do not reflect the e...
Wild bee communities persist in cities despite major disruption of nesting and food resources by urban development. Bee diversity and abundance is key for urban agriculture and maintenance of plant diversity, and assessing what aspects of cities enhance bee populations will promote our capacity to retain and provision bee habitat. Here, we assessed...
Plants are often attacked by multiple antagonists, and traits of the attacking organisms, and their order of arrival onto hosts, may affect plant defenses. However, few studies have assessed how multiple antagonists, and varying attack order, affect plant defense or nutrition. To address this, we assessed defensive and nutritional responses of Pisu...
Drought threatens arthropod communities worldwide. Water limitation affects the quantity and quality of plants available to herbivores as food, and can also affect higher trophic-level consumers through variability in prey quality and reduced availability of suitable habitats. Our study assessed the response of an arthropod community to water limit...
Grasslands are globally imperiled ecosystems due to widespread conversion to agriculture, and there is a concerted effort to catalogue arthropod diversity in grasslands to guide conservation decisions. The Palouse Prairie is one such endangered grassland; a mid-elevation habitat found in Washington and Idaho, United States. Ants (Formicidae) are us...
Arthropods are responsible for pollinating the majority of food and fuel crops worldwide. However, global declines in bee populations threaten the delivery of pollination services in both managed and natural ecosystems. Alternative pollinators such as flies, butterflies, beetles, and wasps may provide a buffer that protects agriculture from bee pop...
Plants are often attacked by multiple antagonists, and traits of the attacking organisms, and their order of arrival onto hosts, may affect plant defenses. However, few studies have assessed how multiple antagonists, and varying attack order, affect plant defense or nutrition. To address this, we assessed defensive and nutritional responses of Pisu...
Arthropods that vector plant pathogens often interact with predators within food webs. Predators affect vectors by eating them (consumptive effects) and by inducing antipredator behaviors (non-consumptive effects), and these interactions may affect transmission of vector-borne pathogens. However, it has proven difficult to experimentally tease apar...
Pest monitoring networks form the foundation of many integrated pest management programs in agroecosystems throughout the world. These monitoring networks tend to focus on widely dispersed and highly variable insect pest populations that can cause significant crop loss without intervention. By assessing the distribution and abundance of insects ove...
Crop-associated microbiota are key factors affecting host health and productivity. Most crops are grown within heterogeneous landscapes, and interactions between management practices and landscape context often affect plant and animal biodiversity in agroecosystems. However, whether these same factors typically affect crop-associated microbiota is...
Insect alarm pheromones are chemical substances that are synthesized and released in response to predators to reduce predation risk. Alarm pheromones can also be perceived by predators, who take advantage of alarm cues to locate prey. While selection favors evolution of alarm pheromone signals that are not easily detectable by predators, predator e...
Insect alarm pheromones are chemical substances that are synthesized and released in response to predators to reduce predation risk. Alarm pheromones can also be perceived by predators, who take advantage of alarm cues to locate prey. While selection favors evolution of alarm pheromone signals that are not easily detectable by predators, predator e...
Changing climate and land‐use practices have the potential to bring previously isolated populations of pest insects into new sympatry. This heightens the need to better understand how differing patterns of host plant association, and unique endosymbionts, serve to promote genetic isolation or integration. We addressed these factors in populations o...
Crop tissues harbor microbiomes that can affect host health and yield. However, processes driving microbiome assembly, and resulting effects on ecosystem services, remain poorly understood. This is particularly true of flowering crops that rely on pollinators for yield.
We assessed effects of orchard management tactics and landscape context on the...
Mutualistic plant-pollinator interactions are critical for the functioning of both non-managed and agricultural systems. Mathematical models of plant-pollinator interactions can help understand key determinants in pollination success. However, most previous models have not addressed pollinator behavior and plant biology combined. Information genera...
The Asian giant hornet (Vespa mandarinia) was recently detected in western British Columbia, Canada and Washington State, United States. V. mandarinia are an invasion concern due to their ability to kill honey bees and affect humans. Here, we used habitat suitability models and dispersal simulations to assess potential invasive spread of V. mandari...
The larvae of click beetles (Coleoptera: Elateridae), known as "wireworms," are agricultural pests that pose a substantial economic threat worldwide. We produced one of the first wireworm genome assemblies (Limonius californicus), and investigated population structure and phylogenetic relationships of three species (L. californicus, L. infuscatus,...
Invasive species are among the leading threats to global ecosystems due to impacts on native flora and fauna through competition and predation. The lily leaf beetle, Lilioceris lilii Scopoli (Coleoptera: Chrysomelidae), is an invasive pest of lilies (Lilium spp.) and other genera of Liliaceae (Liliales). A habitat suitability model was created usin...
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...
Many studies have shown that virus infection alters phytohormone signaling and insect vector contact with hosts. Increased vector contact and movement among plants should increase virus survival and host range. In this study we examine the role of virus-induced changes in phytohormone signaling in plant-aphid interactions, using Pea enation mosaic...
Understanding factors that affect the population dynamics of insect pest species is key for developing integrated pest management strategies in agroecosystems. Most insect pest populations are strongly regulated by abiotic factors such as temperature and precipitation, and assessing relationships between abiotic conditions and pest dynamics can aid...
The Asian giant hornet (Vespa mandarinia) is the world's largest hornet. It is native to East Asia, but was recently detected in British Columbia, Canada, and Washington State, USA. Vespa mandarinia are an invasion concern due to their potential to negatively affect honey bees and act as a human nuisance pest. Here, we assessed effects of bioclimat...
Greater natural enemy diversity generally increases prey mortality. Diversity can be beneficial when natural enemy species occupy distinct niches (complementarity effects) or when diverse communities contain the most impactful species by chance (identity effects). Most research assessing effects of natural enemy diversity focuses on aboveground pre...
Organic management is rapidly expanding as an alternative to conventional agriculture, but maintaining sufficient available soil nitrogen (N) supply is a challenge for organic systems in the semiarid regions of the US Pacific Northwest (PNW). Quinoa (Chenopodium quinoa Willd.) is a potential new crop for such systems, but there are many knowledge g...
• Pollinators are introduced to agroecosystems to provide pollination services. Introductions of managed pollinators often promote ecosystem services, but it remains largely unknown whether they also affect evolutionary mutualisms between wild pollinators and plants.
• Here, we developed a model to assess effects of managed honey bees on mutualisms...
Mutualistic plant-pollinator interactions are critical for the functioning of both non-managed and agricultural systems. Mathematical models of plant-pollinator interactions can help understand key determinants in pollination success. However, most previous models have not addressed pollinator behavior and plant biology combined. Information genera...
Characterizing factors affecting insect pest populations across variable landscapes is a major challenge for agriculture. In natural ecosystems, insect populations are strongly mediated by landscape and climatic factors. However, it has proven difficult to evaluate if similar factors predict pest dynamics in agroecosystems because control tactics e...
Organic farming can improve soil quality and provide effective pest control with reduced inputs compared to conventional farming. Although organic and conventional farming are often viewed as dichotomous, they may overlap in pest management and soil quality goals and outcomes. Here, we assessed similarities and differences between conventional and...
Significance
Organic agriculture promotes environmental and socioeconomic sustainability to a greater degree than conventional agriculture. However, it is unknown whether effects of organic agriculture on sustainability metrics such as biodiversity, crop yields, and profitability vary across the diverse landscapes where organic farming is practiced...
Pollinators provide ecosystem services that are threatened by the loss of wild and managed bees. Citizen scientists can monitor bees to yield useful data that may guide conservation of threatened bee populations. However, the factors that promote data collection in pollinator citizen science projects are largely unknown, inhibiting development of c...
Bees are ecosystem service providers that are globally threatened by losses of plant diversity. However, effects of multi‐species floral displays on bees in agro‐ecosystems with variable landscape context remain poorly understood, hindering pollinator conservation tactics. We addressed this knowledge gap through a novel application of the modified...
Volatile crop prices and a desire for sustainability have farmers considering alternative practices to increase revenue diversity and protect soil health. Organic management is rapidly expanding as an alternative to conventional agriculture, and quinoa (Chenopodium quinoa Willd.) is a potential new crop for organic systems in the Pacific Northwest....
A growing number of studies indicate that plant viruses enhance their own transmission by modifying host phenotypes and vector behavior, leading to the hypothesis that such effects are manipulations resulting from virus adaptations. However, few studies have linked putative manipulations with virus components, and the true frequency and magnitude o...
Herbivores that transmit plant pathogens often share hosts with non-vector herbivores. These co-occurring herbivores can affect vector fitness and behaviour through competition and by altering host plant quality. However, few studies have examined how such interactions may both directly and indirectly influence the spread of a plant pathogen. Here,...
Many insect herbivores are vectors that transmit plant pathogens as they forage. Within food webs, vectors interact with a range of host plants, other herbivores, and predators. Yet, few studies have examined how tri‐trophic interactions involving vectors affect the spread of pathogens. Here we assessed effects of food web structure on aphid vector...
To promote food security and sustainability, ecologically intensive farming systems should reliably produce adequate yields of high-quality food, enhance the environment, be profitable, and promote social wellbeing. Yet, while many studies address the mean effects of ecologically intensive farming systems on sustainability metrics, few have conside...
European earwig, Forficula auricularia L. (Dermaptera: Forficulidae), is an omnivore found in fruit orchards and vineyards worldwide. Earwigs are predators in many crop systems, but may be pests in others. To address uncertainty regarding the pest status of European earwig, we review its biology, effects in fruit agroecosystems, and management. Cur...
Within food webs, vectors of plant pathogens interact with individuals of other species across multiple trophic levels, including predators, competitors, and mutualists. These interactions may in turn affect vector‐borne pathogens by altering vector fitness and behavior. Predators, for example, consume vectors and reduce their abundance, but often...
