Study finds a parasite of powdery mildew in about 7% of samples

The screening found Ampelomyces in about 7% of all powdery mildew specimens analyzed. Ampelomyces acts as a hyperparasite, a parasite of a parasite: it infects the fungi that cause powdery mildew. The finding suggests that a less visible ecological interaction has remained partly hidden in preserved collections and reference records.

The researchers did more than count infections. They also checked the names attached to GenBank entries. Among samples labeled as Ampelomyces, they classified around 15% incorrectly. Bradshaw called the error a risk of relying on large data sets that anyone can contribute to.

Could Ampelomyces help control powdery mildew?

Michael Bradshaw, the study’s corresponding author (the researcher to whom outside questions about the paper are directed), is an assistant professor of entomology (insect biology) and plant pathology (plant-disease science) at North Carolina State University. He said that understanding hyperparasite diversity could help researchers identify strains better suited to controlling the fungus. He put the prospect cautiously:

“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. 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.”

Host specificity, which describes how narrowly a parasite is associated with the organism it infects, could make strain differences matter. Bradshaw’s comments describe a possible route to disease control, not a treatment already demonstrated by the study. The reported screening measured prevalence and identification accuracy, while the potential control value remains a hypothesis for further study.

What can herbaria show next?

These findings show that herbaria can serve as powerful tools for studying hyperparasites and their interactions with plants and fungi. Infected preserved specimens offered a historical, geographically broad record that the team could compare with DNA sequence data. The study treats these collections as archives of ecological relationships that may remain difficult to observe directly.

The researchers identified two directions for expansion:

• Sampling across broader geographic regions.
• Studies spanning more diverse host types.

Both would extend a collection already spanning 28 countries and 150 years, although the reported percentages apply to the screened materials rather than every specimen worldwide.

The paper, “Parasites of parasites: Herbaria as archives of hidden ecological interactions,” appeared in 2026 in Proceedings of the Royal Society B: Biological Sciences (Proceedings B). Jacklyn Thomas and colleagues listed it under DOI 10.1098/rspb.2026.1772.

Taken together, the results show that the fungal parasite was more common than previously recognized, while shared genetic records still require biological checks.