Impacts of Contrasting Alfalfa Production Systems on the Drivers of Carabid Beetle (Coleoptera: Carabidae) Community Dynamicsby H. B. Goosey, S. C. McKenzie, M. G. Rolston, K. M. O’Neill, F. D. Menalled

Environ Entomol

About

Year
2015
DOI
10.1093/ee/nvv104
Subject
Ecology / Insect Science / Ecology, Evolution, Behavior and Systematics

Text

COMMUNITY AND ECOSYSTEM ECOLOGY

Impacts of Contrasting Alfalfa Production Systems on the

Drivers of Carabid Beetle (Coleoptera: Carabidae) Community

Dynamics

H. B. GOOSEY,1,2 S. C. MCKENZIE,3 M. G. ROLSTON,1 K. M. O’NEILL,3 AND F. D. MENALLED3

Environ. Entomol. 1–13 (2015); DOI: 10.1093/ee/nvv104

ABSTRACT Growing concerns about the environmental consequences of chemically based pest control strategies have precipitated a call for the development of integrated, ecologically based pest management programs. Carabid or ground beetles (Coleoptera:Carabidae) are an important group of natural enemies of common agricultural pests such as aphids, slugs, and other beetles. Alfalfa (Medicago sativa L.) is one of the most common forage crop species in the semi-arid western United States. In 2011, Montana alone produced 4.0 106 Mg of alfalfa on 8.1 105 ha for gross revenue in excess of US$4.3 108, making it the third largest crop by revenue. We conducted our study over the 2012 and 2013 growing seasons. Each year, our study consisted of three sites each with adjacent systems of monoculture alfalfa, alfalfa nurse cropped with hay barley, and an uncultivated refuge consisting of a variety of forbs and grasses. Carabid community structure differed and strong temporal shifts were detected during both 2012 and 2013. Multivariate fuzzy set ordination suggests that variation in canopy height among the three vegetation systems was primarily responsible for the differences observed in carabid community structure. Land managers may be able to enhance carabid species richness and total abundance by creating a heterogeneous vegetation structure, and nurse cropping in particular may be effective strategy to achieve this goal.

KEY WORDS Carabidae, community assembly, conservation biocontrol, alfalfa production, multivariate fuzzy set ordination

Growing concerns about the environmental consequences of chemically based pest control strategies have precipitated a call for the development of integrated, ecologically based pest management programs (Altieri et al. 1983, Matson et al. 1997, Robertson and Swinton 2005). Instead of relying primarily on synthetic inputs, these programs are based on augmenting ecological processes to stabilize or manage pest populations (Liebman and Gallandt 1997, Magdoff 2007, Altieri et al. 2012).

Conservation biological control, in which a producer manipulates the ecological conditions in their system to enhance populations of natural enemies, is one such strategy (Barbosa 1998). Habitat management is a subset of conservation biocontrol that includes altering disturbance spatio-temporal regimes to decrease natural enemy mortality, improving shelter or microclimatic conditions to prevent their emigration, or providing refugia to which they can escape during managementimposed disturbances (Landis et al. 2000).

Carabid or ground beetles (Coleoptera:Carabidae) are an important group of natural enemies of common agricultural pests such as aphids, slugs, and other beetles (Holland 2002, Sunderland 2002). They comprise one of the most abundant and diverse families of beetles and are abundant and ubiquitous in northern temperate agroecosystems (Lovei and Sunderland 1996). Many carabid beetle species, especially those in the Zabrini and

Harpalini tribes, are seed predators and may help regulate weed populations (Tooley and Brust 2002, Menalled et al. 2007, Gaines and Gratton 2010). For these reasons, carabids are often regarded as target species of conservation biocontrol. However, many carabid species have very specific habitat preferences and are highly sensitive to changes in their environment (Lovei and

Sunderland 1996). Thus, habitat management practices could have important ramifications for carabid beetle conservation in highly disturbed agricultural systems.

Alfalfa (Medicago sativa L.) is one of the most common forage crop species in the semi-arid western

United States (Putnam et al. 2000). In 2011, Montana alone produced 4.0 106 Mg of alfalfa on 8.1 105 ha for gross revenue in excess of US$4.3 108, making it the third largest crop by revenue and area harvested in the state after spring and winter wheat (Triticum aesativum L.; National Agricultural Statistics Service [NASS] 2013). A major threat to alfalfa production is herbivory by insect pests such as the alfalfa weevil (Hypera postica Gyllenhal), aphids (Hemiptera: Aphididae), and cutworms (Lepidoptera: Noctuidae) (Summers 1998,

Brewer and Hoff 2002, Salisbury 2004). For example, herbivory by the alfalfa weevil alone can result in yield losses of up to 30–40% in the Intermountain West of the United States (Salisbury 2004). 1 Department of Animal and Range Sciences, 103 Animal Bioscience Building, P.O. Box 172900, Montana State University, Bozeman, MT 59717-3120. 2 Corresponding author, e-mail: hgoosey@montana.edu. 3 Department of Land Resources and Environmental Sciences, 334

Leon Johnson Hall, P.O. Box 3120, Montana State University, Bozeman, MT 59717-3120.

VC The Authors 2015. Published by Oxford University Press on behalf of Entomological Society of America.

All rights reserved. For Permissions, please email: journals.permissions@oup.com

Environmental Entomology Advance Access published July 9, 2015

In contrast to most other major commodities in the region, alfalfa is a perennial crop, thus providing temporally stable habitat for insect pests as well as their natural enemies, including carabids (Summers 1998).

Therefore, habitat management to enhance natural carabid communities in alfalfa could be an important ecologically based component of an integrated pest management strategy (Clark et al. 1997). Specifically, increasing plant diversity at both the within-field (a-diversity) and between-field (b-diversity) scales may help assemble a more diverse array of natural enemies and thereby enhance biological control (Altieri and

Letourneau 1982, Altieri 1999, Benton et al. 2003,

Letourneau et al. 2011).

Barbosa and Wratten (1998) argue that habitat management is only an effective means of conservation biological control if the natural enemy populations have the proper spatial and temporal distribution within an agroecosystem. Thus, understanding the community dynamics of target natural enemies and how those dynamics relate to changes in the environment is imperative for proper habitat management. Nurse cropping (also known as relay cropping or companion cropping), in which one species with a short life cycle is grown simultaneously with a second, longer-lived species, is a method by which to increase vegetative a-diversity in agroecosystems (Roslon and Fogelfors 2003). Nurse cropping can provide a variety of agronomic benefits including weed suppression, soil stabilization, alternative sources of revenue, and pest management (Canevari 2000). Uncultivated areas within farmlands can increase b-diversity as they may provide refugia or alternative habitats to natural enemies (Lee et al. 2001,