Beyond soil health: the trophic effects of cover crops shape predator communities

Abstract

Maintaining habitat throughout the season in annual cropping systems provides resource stability for arthropod communities. Stabilizing resource availability should lead to diverse predatory communities and their associated ecosystem services such as biological control. There is a need for studies to test change in predator communities due to habitat provisioning and estimate associated food web responses. Here we quantified predator community structure and used molecular gut-content analysis to reconstruct predator food webs in response to winter cover crops (i.e. cereal and legume based) in a cotton agroecosystem. Predators were collected from experimental field plots during each major crop development stage in 2017 and 2018, and PCR was used to estimate predator roles and responses to cover crop treatments. Cotton planted into a rye cover crop residue promoted unique predator communities in the early and mid-season as compared to no-cover fields. Correspondingly, we observed dissimilar prey consumption among cover crop treatments. While predators consumed incidental pests at high frequencies (e.g. aphids), predation on key pests by natural enemies in this system was lacking. The use of winter cover crops and reduced tillage practices increased the consumption of alternative prey by natural enemies on seedling cotton, encouraging high predator diversity that aligns temporally with potential early season pest outbreaks. Therefore, cover crops should be further integrated into integrated pest management strategies.

Identifying Molecular-Based Trophic Interactions as a Resource for Advanced Integrated Pest Management

“…Although such measurements provide valuable information regarding the overall impact of natural enemies on a particular insect pest, we know little about the role that the observed natural enemies play in agroecosystems. MGCA can be used to investigate complex interactions in the agricultural landscapes, such as to track parasitism [ 50 ], predation frequency [ 51 , 52 ], and complex trophic food webs [ 51 , 53 ]. Interactions between natural enemies and pests can be linked to the degree of agricultural landscape complexity (e.g., the proportion of non-crop habitat in the surrounding landscape).…”

Can Generalist Predators Control Bemisia tabaci?

“…Similarly, Hagler and Blackmer [ 17 ] found a high percentage of various predators with B. tabaci DNA in their gut from cotton fields ( Table 3 ). Contrary to these findings, predation during the early, mid, and late season in Georgia cotton and predation on B. tabaci by species within two spider families, including Gnaphosidae and Salticidae, was low [ 59 ]. The difference between studies may be due to overall higher densities of whitefly in Arizona cotton fields relative to Georgia.…”

“…Molecular gut content analysis (MGCA) is an effective method to determine the links between trophic levels in agricultural fields [ 22 , 76 ]. Given the potential of MGCA to unravel natural enemy interactions with pests [ 23 , 24 , 77 , 78 , 79 ], it is surprising that only a few studies have determined key predators of B. tabaci in the US agroecosystems [ 17 , 59 ]. Current understanding of natural enemy- B. tabaci trophic interactions will benefit from studies conducted with a gradient of agricultural land-use practices with a broad spatial extent to model not only the movement of but also trophic interactions between cropping systems.…”