Spontaneous weed strips associated with chili pepper agroecosystems impact the abundance and survival of aphid predators

Habitat manipulation has been used as strategy to enhance beneficial insects in agroecosystems. Spontaneous plant strips have the potential of supplying resources for maintaining natural enemies even when pest densities are low. In tropical agroecosystems there is a paucity of information relating to the specific resources provided by spontaneous plants and their interactions with natural enemies. In this study we evaluated a) whether spontaneous plants within chili pepper fields affected diversity and abundance of aphidophagous species; b) whether there are direct interactions between spontaneous plants and aphidophagous arthropods; and c) the importance of spontaneous plant floral resources for survival and reproduction of two coccinelids commonly found in chili pepper agroecosystems in Brazil. Aphidophagous arthropods were dominated Coccinellidae, Syrphidae, Anthocoridae, Neuroptera and Araneae, and these natural enemies were observed to be readily preying on aphids, feeding on flowers or extrafloral nectarines, and using plant structures for oviposition and/or protection. The most abundant plant species harboring aphidophagous predators were Ageratum conyzoides, Sonchus oleraceus, Bidens pilosa, Digitaria sp., Solanum americanum and Senna obtusifolia. Differential survival of Cycloneda sanguinea adults was observed between plant species, with significantly greater survival on A. conyzoides and B. pilosa flowers compared to S. oleraceus flowers. No evidence was gathered to suggest that floral resources provided nutritional benefit to Harmonia axyridis. This research has provided evidence that spontaneous plants in chili pepper crops can affect aphid natural enemy abundance and survival, indicating further research is required to characterize the structure and function of plant resources in tropical agroecosystems.