Spatiotemporal Aspects of Enemy-Risk Effects
Enemy-risk effects and direct consumptive effects frequently occur on different spatiotemporal scales, with many risk effects occurring over larger areas and longer times than CEs. This means that many studies focusing on CEs lack the scale necessary to capture enemy-risk effects, a topic that has been reviewed elsewhere (Hermann & Landis 2017) and covered with respect to biological control in Table 2. Beyond expanding the scales of biocontrol enemy-risk effect research in the future, current theory and evidence from the broader literature may help biocontrol practitioners conceptualize and predict how enemy risk affects pest abundance and interactions with other pest management measures in time and space.
            Just as pests act within a “landscape of fear” shaped by enemy cues that are heterogeneous through time and space (Laundré et al. 2001), agricultural landscapes exhibit spatiotemporal variability across multiple scales. Agroecosystems are spatially heterogeneous at the within-plant, between-plant, within-field, and between-field scales, especially when farmers use practices such as intercropping or planting hedgerows. They also change throughout time, as many crops undergo a relatively predictable growth pattern, changing in vulnerability to various pests and in their spatial structure. Farmers apply pesticides, irrigate, and harvest crops according to schedules, creating temporal patterns of disturbance. By superimposing the temporally variable landscape of risk and the temporally variable agricultural landscape, we may be able to integrate enemy-risk effects into predictions on interactions between biocontrol agents and other IPM strategies. We outline specific ways in which enemy-risk effects in space and time may interact with agricultural practices in the following sections.