The response of epigeic predators to contrasting agricultural managements of South Africa

Maria Makwela, Caswell Munyai and Rob Slotow, School of Life Sciences, University of KwaZulu-Natal, Durban, South Africa

Background/Question/Methods
Agriculture is facing an enormous challenge of producing enough food for the increasing human population worldwide, leading to greater cropland intensification and expansion. This has numerous negative impacts on biodiversity and associated ecosystem services. Epigeic predators are components of agricultural landscapes and provide essential ecosystem services of biological pest control. Therefore, knowledge of how farming management affects the predator assemblage is crucial. The study investigates the effect of conventional and conservation management practices on epigeic predators (carabids, rove, ants, and spiders) in two grain-producing areas, Free State, South Africa. Arthropod predators were sampled in 10 replicated sampling sites (monoculture, rotational and continuous grazing, crop rotation, and cover crops) using pitfall traps. Six pitfall traps spaced 5 m apart were placed in a parallel transect at the center of each sampling site. Traps were filled with 65% propylene glycol and were left open for 5 days. During sampling collection, trap contents were pooled for analysis within each sampling site. Total predator species data were analyzed independently. Statistical analyses were carried out with R statistical software (version 3.2.0.)
Results/Conclusions
Overall, 984 predator species and 7316 individuals were sampled during this study. The predator assemblage consisted of carabids (652 spp., 4 681 ind.), spiders (215 spp., 1551 ind.), ants (101 spp., 650 ind.), and rove beetles (16 spp., 321 ind.). Carabid beetles (28 % spp., 109 % ind.) followed by spiders (18 % spp., 5 % ind.) dominated the predator assemblages. Agroecosystem management were found to have a prominent impact on predator species richness, and abundance across all taxonomic groupings. Species richness and abundance were significantly greater under conservation management across all groupings with an exception of rove beetle species richness. Conservation management consistently improved predator species richness and abundance relative to conventional management. Our preliminary results underpin that promoting sustainable measures that consist of cover crops, crop rotations, and mulching can maximize the abundance of predator arthropods, and the efficacy of agricultural pests and weeds control, thereby reducing the use of chemical inputs. Therefore, farmers need to implement sustainable managements that may foster biodiversity and related ecosystem services and enhance environmental sustainability and productivity.