Robigalia Roundup LXXIV: A fungus with 400+ hosts and the researcher fighting back

Sclerotinia sclerotiorum is a necrotrophic fungal pathogen with an exceptionally broad host range, infecting over 400 plant species across oilseeds, pulses, and vegetables. Key global hosts include soybean, canola, sunflower, and dry bean, with major impacts also in chickpea, lentil, peanut, and lettuce.

The disease cycle begins in the soil. Melanised sclerotia, the pathogen's long-term survival structures, can persist for years before undergoing carpogenic germination under cool, moist conditions. This produces apothecia (small cup-shaped fruiting bodies) that release airborne ascospores, which go on to infect senescing or wounded plant tissue. Disease often initiates from infected petals, with the pathogen then rapidly colonising stems, branches, and pods. Symptoms include water-soaked lesions, white cottony mycelium, and black sclerotia within necrotic tissue.

Depending on the host and organ affected, the disease presents as white mould, stem rot, or head rot. In soybean, canola, and pulses, stem infection leads to lodging, premature ripening, and yield losses that can exceed 20 to 30% under conducive conditions.

Sclerotinia sclerotiorum is present across most temperate and cool subtropical cropping regions worldwide, and is particularly damaging in dense, high-yielding canopies where prolonged leaf and stem wetness favours repeated infection events.

Managing the pathogen relies on integration across several approaches. Cultural measures including wider row spacing and reduced seeding rates help limit the canopy microclimate conditions that favour disease development. Rotations away from consecutive susceptible broadleaf hosts reduce, though do not eliminate, sclerotia return to soil over time.

Fungicide applications timed to early to mid-flowering, guided by apothecia monitoring and weather-based risk models, protect petals and primary infection courts. Host resistance is available but generally partial, reinforcing the need for coordinated management rather than reliance on any single tool.

Increasingly, research attention is turning to whether soil microbial communities can contribute to suppression of S. sclerotiorum, particularly through effects on sclerotia survival and germination. That's the focus of this week's plant pathologist.

This week, we introduce Viet-Cuong Han, a recent PhD student from Curtin University’s Centre for Crop and Disease Management.

Cuong's path into plant pathology started in Vietnam, where an undergraduate supervisor with a genuine passion for disease diagnostics helped him see the field as more than applied agronomy. Plant pathology, as Cuong came to understand it, sits at the intersection of microbiology, ecology, and real agricultural impact. That framing has shaped everything for him since.

His Master's degree in South Korea put that framing into practice. There, he trained in molecular diagnostics and pathogen identification, and began working with beneficial microorganisms and their natural secondary metabolites for biocontrol. It was hands-on work with a clear question underneath it: if certain microbes can suppress plant pathogens, what is actually driving that suppression, and how do you harness it reliably?

That question carried him to Australia, where he completed his PhD at Curtin University's Centre for Crop and Disease Management. His doctoral research zoomed in on how soil- and plant-associated microbial communities influence disease outcomes, with a focus on whether those interactions can be leveraged to reduce dependence on chemical inputs. His recent paper with colleagues addresses this directly, examining how antagonistic soil microbiota drive suppressiveness against S. sclerotiorum and what that means for disease management beyond the fungicide schedule.

Running alongside that applied focus is a second thread: diagnosing emerging plant pathogens and characterising their diversity. Both directions reflect the same underlying interest in understanding how pathogens and microbial communities interact across different environments.

Cuong is an active member of APS and APPS, and serves as an academic editor for New Disease Reports and Archives of Phytopathology and Plant Protection. His career has taken him across three countries and counting.

You can chat more with Cuong about his research through LinkedIn.

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See you next Monday!

P.S. Why Robigalia? The name originates from the Ancient Roman festival dedicated to crop protection. You can read all about the history here: