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Data and code from: Aphid honeydew reduces soil nitrogen and increases host plant growth

Yang, Louie1; Gonzalez, Lizbeth1; Solís, Sarah1; Singh, Prabhjot1

Published Jul 15, 2026 on Dryad. https://doi.org/10.5061/dryad.mcvdnckcz

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Abstract

Plants affect their soils in ways that can have positive or negative effects on themselves and other plants. We report the results of an experiment that investigated how a plant-herbivore interaction affected later seedling growth via changes to the soil. Many sap-feeding insect herbivores produce and expel a copious, post-digestion solution of excess photosynthate sugars called honeydew. Previous ecosystem-level studies suggest that this carbon-rich input of labile dissolved organic matter commonly drives nitrogen immobilization (and reduces nitrogen availability) as it is transported into the soil. Here, we ask if seasonal pulses of accumulated aphid (Aphis nerii) honeydew reduce the availability of soil nitrogen below milkweed (Asclepias fascicularis) host plants, and how honeydew-conditioned soil affects the subsequent growth of multiple seedling species. We find that the addition of honeydew at accumulated levels reduced total inorganic soil nitrogen by 48.8 % relative to controls. Unexpectedly, milkweed seedlings grew 4.2 times larger by mass and 90 % taller than those in the control group. We did not observe any honeydew effects on the growth of two potentially competing species (cheatgrass, Bromus tectorum, and yellow star-thistle, Centaurea solstitialis). These results suggest the possibility of a positive plant-soil feedback for milkweeds, mediated by aphid honeydew.