Even parasites have parasites

In the fungal kingdom, no one is safe from parasites – not even other parasites. 

A new study from North Carolina State University finds that Ampelomyces, an intracellular fungus that infects the plant disease powdery mildew, is far more common than previously known. By screening museum samples of powdery mildews up to around 150 years old, researchers discovered that not only is Ampelomyces quite common, but many specimens labeled as Ampelomyces are misidentified. 

Because powdery mildews cannot be cultured, researchers screened over 600 dried samples from the NC State herbarium (a collection of plant and/or fungal samples) to collect data on the prevalence of Ampelomyces. These samples were collected across 28 countries over the past 150 years, and were analyzed alongside samples available on GenBank, a public database of DNA sequences used by scientists to share and study genetic data. In total, scientists screened over 600 samples between GenBank and the herbarium. Researchers found that around 7% of all powdery mildew specimens analyzed were infected by this parasite. 

Michael Bradshaw, corresponding author of the study and an assistant professor of entomology and plant pathology at NC State, said that understanding hyperparasites (parasites of parasites) could open doors to better control methods for the fungi they infect. 

“By understanding hyperparasite diversity and how many different strains are out there, it might give us insights on if some are better at controlling the fungus than others,” Bradshaw said. “There is a degree of host specificity to these hyperparasites, and if we are able to delve deeper they may be very useful in containing this plant disease.”

Another significant finding was that among the GenBank specimens screened, around 15% of those labeled as Ampelomyces were misidentified. Bradshaw said that this level of inaccuracy is part of the risk when relying on large data sets where anyone can input information.

“These parasites are hard to identify, so what happens is someone misidentifies them and enters incorrect data,” Bradshaw said. “Then someone else sees that wrong data and uses it to classify their own samples, which leads to more wrong data, and it amplifies that way.”

These findings demonstrate how herbaria can act as powerful tools for observing a range of biological phenomena such as studying hyperparasites and their interactions with plants and fungi. Further research could focus on expanding sampling across broader geographic regions and diverse host types. 

The paper, “Parasites of Parasites: Herbaria as Archives of Hidden Ecological Interactions,” is published in Proceedings B. Funding for the project comes from the National Science Foundation, Award Number 2402193. This work was also supported by the Research Capacity Fund (HATCH), project award no. 7006142, from the U.S. Department of Agriculture’s National Institute of Food and Agriculture. 

Co-authors include Jacklyn Thomas, Andrew Paul, Uma Crouch and Ignazio Carbone, NC State; Uwe Braun, Martin Luther University; Susumu Takamatsu, Mie University, retired; Márk Z. Németh, HUN-REN Centre for Agricultural Research and ELTE Eötvös Loránd University; Levente Kiss, HUN-REN Centre for Agricultural Research and University of Southern Queensland; James Mitchell, Harvard University; and Henry Van T. Cotter, University of North Carolina at Chapel Hill.

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Note to Editors: The study abstract follows.

“Parasites of Parasites: Herbaria as Archives of Hidden Ecological Interactions”

Authors: Michael Bradshaw, Jacklyn Thomas, Andrew Paul, Uma Crouch and Ignazio Carbone, NC State University; Uwe Braun, Martin Luther University; Susumu Takamatsu, Mie University, retired; Márk Z. Németh, HUN-REN Centre for Agricultural Research and ELTE Eötvös Loránd University; Levente Kiss, HUN-REN Centre for Agricultural Research and University of Southern Queensland; James Mitchell, Harvard University; and Henry Van T. Cotter, University of North Carolina at Chapel Hill.

Published: 11/11/2026, Proceedings of the Royal Society B

DOI: 10.1098/rspb.2026.1772 

Abstract: Hyperparasitism, the infection of parasites by other parasites, is among the least explored ecological interaction types. Ampelomyces, intracellular fungi that infect the plant disease powdery mildews, form a naturally occurring parasite-on-parasite system that is both widespread and poorly understood. This tripartite association among plants, pathogens, and hyperparasites provides a powerful model for studying multi-trophic interactions and the evolution of host specialization. Using DNA from herbarium specimens collected across 28 countries over the past 150 years as well as those available on GenBank, we reveal previously hidden ecological and evolutionary patterns in the Ampelomyces–powdery mildew system. Historical collections allowed us to detect hyperparasites that cannot be easily observed, uncovering multiple novel lineages and global patterns of host association. A global reassessment of all publicly available sequences showed that 15% of entries labeled as Ampelomyces are misidentified revealing a major issue with uncurated, public databases. To resolve this, we developed a curated, voucher-linked phylogenetic framework in T-BAS to serve as a reference for future ecological, genomic, and biocontrol studies. Together, our results demonstrate that herbaria function as large-scale ecological observatories, capable of revealing cryptic interactions across continents and provides a strengthened framework for future ecological and evolutionary research on hyperparasitism.