Mary Gardiner

Increasing corn for biofuel production reduces biocontrol services in agricultural landscapes

Increased demand for corn grain as an ethanol feedstock is altering U.S. agricultural landscapes and the ecosystem services they provide. From 2006 to 2007, corn acreage increased 19% nationally, resulting in reduced crop diversity in many areas. Biological control of insects is an ecosystem service that is strongly influenced by local landscape structure. Here, we estimate the value of natural biological control of the soybean aphid, a major pest in agricultural landscapes, and the economic impacts of reduced biocontrol caused by increased corn production in 4 U.S. states (Iowa, Michigan, Minnesota, and Wisconsin). For producers who use an integrated pest management strategy including insecticides as needed, natural suppression of soybean aphid in soybean is worth an average of

Maximizing arthropod‐mediated ecosystem services in agricultural landscapes: the role of native plants

33 ha−1. At 2007–2008 prices these services are worth at least

Intraguild Predation and Native Lady Beetle Decline

239 million y−1 in these 4 states. Recent biofuel-driven growth in corn planting results in lower landscape diversity, altering the supply of aphid natural enemies to soybean fields and reducing biocontrol services by 24%. This loss of biocontrol services cost soybean producers in these states an estimated

Integrating conservation biological control into IPM systems

58 million y−1 in reduced yield and increased pesticide use. For producers who rely solely on biological control, the value of lost services is much greater. These findings from a single pest in 1 crop suggest that the value of biocontrol services to the U.S. economy may be underestimated. Furthermore, we suggest that development of cellulosic ethanol production processes that use a variety of feedstocks could foster increased diversity in agricultural landscapes and enhance arthropod-mediated ecosystem services.

Impact of intraguild predation by adult Harmonia axyridis (Coleoptera: Coccinellidae) on Aphis glycines (Hemiptera: Aphididae) biological control in cage studies

Beneficial arthropods, including native bees, predators, and parasitoids, provide valuable ecosystem services worth

Landscape composition influences the activity density of Carabidae and Arachnida in soybean fields

8 billion to US agriculture each year. These arthropod-mediated ecosystem services (AMES) include crop pollination and pest control, which help to maintain agricultural productivity and reduce the need for pesticide inputs. Maximizing survival and reproduction of beneficial arthropods requires provision of pollen and nectar resources that are often scarce in modern agricultural landscapes. Increasingly, native plants are being evaluated for this purpose. Native plants can outperform recommended non-natives and also provide local adaptation, habitat permanency, and support of native biodiversity. We predict that the success of insect conservation programs using flowering plants to increase AMES on farmland will depend on landscape context, with the greatest success in landscapes of moderate complexity. Reintegration of native plants into agricultural landscapes has the potential to support m...

Using native plant species to diversify agriculture

Coccinellid communities across North America have experienced significant changes in recent decades, with declines in several native species reported. One potential mechanism for these declines is interference competition via intraguild predation; specifically, increased predation of native coccinellid eggs and larvae following the introduction of exotic coccinellids. Our previous studies have shown that agricultural fields in Michigan support a higher diversity and abundance of exotic coccinellids than similar fields in Iowa, and that the landscape surrounding agricultural fields across the north central U.S. influences the abundance and activity of coccinellid species. The goal of this study was to quantify the amount of egg predation experienced by a native coccinellid within Michigan and Iowa soybean fields and explore the influence of local and large-scale landscape structure. Using the native lady beetle Coleomegilla maculata as a model, we found that sentinel egg masses were subject to intense predation within both Michigan and Iowa soybean fields, with 60.7% of egg masses attacked and 43.0% of available eggs consumed within 48 h. In Michigan, the exotic coccinellids Coccinella septempunctata and Harmonia axyridis were the most abundant predators found in soybean fields whereas in Iowa, native species including C. maculata, Hippodamia parenthesis and the soft-winged flower beetle Collops nigriceps dominated the predator community. Predator abundance was greater in soybean fields within diverse landscapes, yet variation in predator numbers did not influence the intensity of egg predation observed. In contrast, the strongest predictor of native coccinellid egg predation was the composition of edge habitats bordering specific fields. Field sites surrounded by semi-natural habitats including forests, restored prairies, old fields, and pasturelands experienced greater egg predation than fields surrounded by other croplands. This study shows that intraguild predation by both native and exotic predators may contribute to native coccinellid decline, and that landscape structure interacts with local predator communities to shape the specific outcomes of predator-predator interactions.

The future of habitat management - understanding the role of landscape structure in the provisioning of beneficial arthropods and their services.

Most agricultural production systems harbor many species of herbivorous arthropods capable of damaging crops. However, the vast majority of these species do not reach damaging levels. In this chapter we explore the role of predators and parasitoids in suppressing pest abundance and damage. In particular, we focus on factors that influence the abundance of beneficial arthropods in agricultural landscapes. Finally, we address ways to manage these systems to increase the effectiveness of beneficial arthropods. There are three primary means by which managers influence biological control of insects. Importation of natural enemies against pests of exotic origin is sometimes referred to as classical biological control, while augmentation is the rearing and release of natural enemies already present to increase their effectiveness. Conservation of natural enemies involves improving conditions for existing natural enemies by reducing factors which interfere with natural enemies or increasing access to resources that they require to be successful (Ehler, 1998). Habitatmanagement is considered a subset of conservation practices that focus on manipulating habitats within agricultural landscapes to provide resources to enhance natural enemies (Landis et al., 2000). Managing agricultural landscapes to improve biological control relies on a detailed understanding of factors that influence both pest and natural enemy abundance (Fig. 12.1). We begin by examining landscape processes that influence pests and beneficial insects at larger spatial scales. Next we focus on processes that influence these organisms and their interactions at local scales. Finally, we detail steps that pest managers may take to alter agricultural habitats and landscapes to favor natural enemies in IPM systems. Throughout, we attempt to show how both temporal and spatial factors influence the outcome of pest–enemy interactions.