Seed Predation

Increasing demand for produce raised without chemical inputs creates an imperative for agroecologists to develop stronger, ecologically-based, cultural tools for farmers to manage weeds effectively and improve crop yields. An ecological approach to weed management means employing ‘many little hammers’ – a combination of several tactics including crop diversification, rotation, intercropping, cover cropping and conservation biological control as an alternative to a simplified herbicide program. To that end, an extensive body of literature has emerged, focusing on in-field habitat management for epigeal natural enemies in agroecosystems, particularly weed seed predators.

Cover crops are widely used as a cultural control of weeds in low-input agroecosystems, and many studies have investigated their capacity to facilitate weed seed predation services by arthropod natural enemies, particularly within the Carabidae. Ground beetle communities are most frequently examined in invertebrate seed predation studies because of their ubiquity in crop habitats, diversity of food and microclimatic requirements, potential as omnivorous biocontrol agents, and use as bio-indicators.

Figure 1. Ground beetles (Carabidae) are considered the dominant group of granivorous arthropods inhabiting agricultural fields. Many species are omnivorous and will thus consume both weed seeds and insect prey.

Evidence of increased carabid activity density is well-documented under a wide variety of cover crop and living mulch systems. Despite the breadth of work with the Carabidae in cover cropped systems, specific mechanisms of recruitment have not been identified. A combination of several factors likely shape carabid communities in cover crop systems, including structural complexity (i.e., refuge from predation), seed resources, prey resources, and optimal temperature and humidity levels. Currently, the field lacks a mechanistic approach to traditional applied seed predation experiments in cover crop systems, revealing the relative importance of biotic factors affecting carabid activity density and weed seed predation services.

In collaboration with a large team of researchers across the College of Agriculture at Purdue, we are quantifying seed predation as a key ecosystem service provided by granivorous insects in organic vegetable systems, and evaluating habitat management techniques to facilitate their impact on weed communities.

Figure 2. Our work is testing the contribution of local habitat manipulations, such as the use of fall-planted cover crops, in maximizing the ecosystem services provided by beneficial arthropods in annual vegetable systems.