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

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.

Temporal Resource Continuity Increases Predator Abundance in a Metapopulation Model: Insights for Conservation and Biocontrol

“…Recent conceptual models have highlighted the importance of incorporating an understanding of the temporal dynamics of resources in a landscape, in addition to total resource amounts, in order to better understand the abundance of organisms [8,9]. Our metapopulation model showed that both the total amount of basal resources in a landscape and the temporal variance of those resources throughout a season can have large and interacting effects on population dynamics of predators and their prey.…”

“…For example, increasing non-crop habitat surrounding agricultural fields can promote insect abundance, diversity, pollination, and natural pest control [2][3][4][5][6]. Yet, a facile understanding of habitat versus non-habitat or cropland versus natural area ignores the substantial heterogeneity that exists within land use categories [6] as well as the complex temporal dynamics of mobile consumers and their resources [7][8][9].…”

“…The value of temporal resource complementation has received empirical support in beneficial insects such as wild bees, which can benefit from the existence of temporally asynchronous floral resources in heterogeneous landscapes [11][12][13]. However, less is known about how temporal resource complementation affects predatory arthropods, the dynamics of tritrophic interactions, and the consequences for conservation biological control [9]. A population of mobile predators may track ephemeral prey resources across a landscape as they emerge in one location, decline, and then emerge in another.…”

Agriculturally Intensified Landscapes Are Associated With Reduced Body Condition of Lady Beetles

“…Likely reasons for the effects of landscape composition and configuration on lady beetle body condition include differences in spatial and temporal resource continuity and quality. Corn and soybean fields can be heavily colonized by aphids and thus provide abundant prey for lady beetles, but this is only the case during limited time periods; over long periods such fields are characterized by resource scarcity, e.g., before crop emergence, after crop maturity, or after pesticide application (Rand et al 2006;Schellhorn et al 2014;Iuliano and Gratton 2020). In landscapes that are strongly dominated by a few crop monocultures, these periods are synchronized over large areas and habitat patches with alternative food sources are often far away and only accessible at high energetic costs (Bonte et al 2012;Stowe et al 2021b).…”

Tracking research trends on the effects of vegetative strips within agricultural landscapes: A systematic map update

“…see Barrios et al 2018), vegetation around a dam or pond within a field (e.g. see Sawatzky & Fahrig 2019) or planted as bird habitat or beetlebanks (Iuliano & Gratton 2020). There may be crop productivity drawbacks, disservices or management challenges related to within-field strips that discourages land managers from constructing them in these locations (Segre et al 2019;Blancoet al 2020), unless service benefits outweigh costs (Rempelet al 2017;Schulte et al 2017) or if there are other direct benefits, such as harvestable biomass from the strip (Ferrariniet al 2017;Saxhaug et al 2020).…”