Ecological intensification for biocontrol of aphids requires severing myrmecophily

Abstract

With the rollback of insecticides, novel tools for pest control are urgently needed. Aphids are particularly a major concern with few sustainable control alternatives. Ecological intensification has been promoted as a way of “inviting" back nature’s self-regulating abilities into agricultural production systems. Although such measures enhance the presence of natural enemies in agroecosystems, we demonstrate that in an ecologically intensified apple orchard, biocontrol of rosy apple aphid was minimal. We verified why the biodiverse settings did not result in enhanced ecosystem services, i.e., biological control of the rosy apple aphid. Close monitoring of food–web interactions in thousands of aphid colonies showed that tending ants dominated responses, while those of natural enemies were weak or absent. However, application of artificial aphid honeydew diverted ants from tending aphids and flipped the myrmecophily-dominated state into favoring numerical responses of a guild of natural enemies. Responses were swift and controlled both Aphis pomi and Dysaphis plantaginea, provided intervention was synced with aphid and predator phenology. Although myrmecophily in aphids is well-known on its own accord, it has been completely overlooked in ecological intensification. To unlock the aphid-biocontrol potential provided through ecological intensification, myrmecophily needs to be disrupted. Although particularly true for perennial systems, generally practices that reduce soil disturbance favor ants and may amplify aphid pests, thereby reducing biocontrol impacts in ecological intensification efforts. Harnessing ecosystem services requires careful analysis and good understanding of agroecosystem intricacies.