Temporal Resource (Dis)continuity for Conservation Biological Control: From Field to Landscape Scales

Benjamin Iuliano,Claudio Gratton

doi:10.3389/fsufs.2020.00127

Benjamin Iuliano, Claudio Gratton

Open Access

https://doi.org/10.3389/fsufs.2020.00127

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Abstract

Conservation biological control (CBC) seeks to promote the occurrence of natural enemies of agricultural pests by managing habitat to provide key resources in and around farm fields. In particular, vegetation diversity may help ensure temporal resource continuity such that natural enemies are less likely to experience detrimental gaps or bottlenecks as they move through and use different habitats. While the conceptual value of resource continuity has long been recognized by CBC researchers and practitioners, empirical studies have tended to focus on snapshots in space and time. Here we review how continuity of trophic (food) and structural (shelter) resources affect natural enemy conservation and pest control outcomes within farm fields and across agricultural landscapes. Key trophic resources include alternative prey and non-prey food (such as floral nectar and pollen), which can bolster natural enemy nutrition when pests are scarce. Vegetative and non-vegetative structural resources can protect enemies when crop fields are disturbed and provide important overwintering habitat in temperate regions. Within fields, non-crop plantings such as wildflower strips or beetle banks are the most popular habitat management strategies, but temporal intercropping, asynchronous planting/harvesting, and the construction of artificial shelters have high potential to contribute to resource continuity. Analogously, semi-natural habitat at the landscape scale may contribute to resource continuity in some cases, but crop diversity, asynchrony, and urban habitat can also be important. Simultaneous consideration of resource diversity and continuity could generate better predictions and more targeted management interventions for particular pest and enemy assemblages. Future research should strive to expand our understanding of natural enemy resource requirements in space and time.

Highlights

Farmers, scientists, and policymakers are increasingly looking for ways to “ecologically intensify” agricultural production to meet the needs of human populations while minimizing negative effects on the environment and protecting biodiversity (Bommarco et al, 2013; Tittonell, 2014; Kleijn et al, 2019)
Temporal Continuity and Conservation Biocontrol pests while avoiding the downsides of indiscriminate insecticide use (Landis et al, 2000; Gurr et al, 2017). This typically entails diversifying fields and landscapes to minimize the occurrence of herbivores and promote their natural enemies, an approach known as conservation biological control (CBC; Begg et al, 2017)
Habitat management with temporal complementation in mind could maintain the pest control benefits of diversification while minimizing negative effects of direct plant competition that result in yield losses (Letourneau et al, 2011), since the benefits of diversity are spaced over time

Summary

INTRODUCTION

Scientists, and policymakers are increasingly looking for ways to “ecologically intensify” agricultural production to meet the needs of human populations while minimizing negative effects on the environment and protecting biodiversity (Bommarco et al, 2013; Tittonell, 2014; Kleijn et al, 2019). In studies of the landscape ecology of predator-prey interactions, so-called “semi-natural habitat,” or non-crop vegetation around farm fields, is the landscape-level feature most often considered to enhance natural enemy populations and pest control outcomes (Chaplin-Kramer et al, 2011; Karp et al, 2018; Dainese et al, 2019), but others may include landscape-scale crop diversity, asynchronous planting/harvesting, and urban development (Figure 2; section Landscape Features). We reviewed titles and abstracts for relevance, resulting in a final set of 55 papers From these we extracted the geographic location (country or U.S state) in which field work was conducted, the cropping system, the scale(s) (field or landscape) of manipulation or observation, the habitat feature(s) observed or manipulated, the resource type(s) (trophic or structural) considered, the pest and natural enemy group(s) studied, and a brief summary of the main findings (Supplementary Table 1). A modeling study by Spiesman et al (2020) showed that fields or landscapes that

DISCUSSION

Research Outlook and Conclusion