Flowering plants mediate stronger top-down pest regulation in maize fields

Ecological engineering using flowering plants may counteract biodiversity loss and enhance biological control in intensified agricultural systems. In this study, we investigated the effects of flowering plants on the abundance and richness of parasitoids in maize fields and examined the relationships among these plants, parasitoids, pests, and parasitism rates. A field experiment was conducted in eight maize plots, consisting of four treatment plots with flowering plants and four control plots without flowering plants, to compare parasitoid communities, pest abundance, and parasitism rates. Pests were sampled across maize ages using up to 300 plants per field. Seventeen parasitoid families were recorded in the maize fields, with Scelionidae, Encyrtidae, and Mymaridae being the most abundant in both flowering and non-flowering plots. The results showed that flowering plants positively influenced the abundance and richness of several parasitoid families, although these benefits diminished with increasing maize age. Although flowering plants did not directly boost parasitoid populations, structural equation modeling demonstrated that increased parasitoids substantially elevated pest parasitism rates. Total pest abundance was positively associated with parasitoid abundance and richness, which was consistent with a bottom-up numerical response. Intriguingly, no significant linear relationship was found between the distance from flowering plants and pest or parasitoid communities. These findings highlight the critical, albeit complex, role of flowering plants in modulating natural enemy services for sustainable pest management.