Meet the researcher: Getting ahead of the fungus

Why is understanding powdery mildew so important for South African vineyards?

My research focuses on understanding how powdery mildew behaves under South African conditions. We look at how it survives between seasons, when spores are released and how sensitive different pathogen populations are to fungicides.

We also study how frequently the pathogen reproduces sexually and how its populations change. All of this helps us better understand how the disease develops and how we can manage it.

What are you trying to find out that could help growers make better disease-management decisions?

Understanding how pathogens respond to fungicides is an important part of my work. I use genetic markers and other methods to investigate fungicide sensitivity, resistance and population dynamics.

We also need to understand the influence of climate and the host plant on disease development. Together, this knowledge helps inform more sustainable disease-management strategies.

My work also extends to canker and dieback pathogens, biological and chemical control, and managing diagnostic services for grapevine and fruit tree pests and pathogens at the Agricultural Research Council (ARC).

What is one thing your research has revealed about powdery mildew that South African growers might not know?

One thing growers may not realise is that grapevine powdery mildew has more than one way of surviving between seasons. In addition to surviving in dormant buds, the fungus can produce tiny, dark structures called chasmothecia on infected plant material. These structures contain sexual spores that can contribute to infections in the following season. This means that the disease cycle can begin long before the first powdery colonies become visible. Understanding when and how the pathogen survives and releases spores is important for improving disease monitoring and timing control measures. By the time the familiar powdery mildew appears, the infection process is already underway. Additionally, the asexual life cycle that occurs throughout the growing season can replicate every 14 days. It takes 14 days for the fungus to sporulate, spread, infect new host tissue and sporulate.

What first made you interested in studying fungal diseases? 

My interest in plant diseases probably started long before I realised it could become a career. As a child, I was happiest outside in the garden, propagating Clivia plants and trying to keep them healthy. I became fascinated by the pests and pathogens that affected my plants and wanted to understand how to control them. Looking back, that childhood curiosity was the beginning of my journey into plant pathology. I think that same curiosity still drives my research today: wanting to understand why a disease develops, how a pathogen survives and spreads, and how we can manage it more effectively.

What is the biggest mistake or misconception growers have about powdery mildew orfungicide resistance? 

One of the biggest misconceptions about fungicide resistance is that it develops overnight. In reality, it is a gradual process that can take many years. Fungal populations are not static; they can adapt over time. Repeated exposure to fungicides with the same mode of action places selection pressure on the population, allowing individuals with reduced sensitivity to survive and gradually become more common. Eventually, a fungicide that once provided effective control may no longer work as well. Interestingly, resistance is not always permanent. When a fungicide is withdrawn from a spray programme, the fungal population can change over time, and sensitivity may increase again, potentially allowing the product to regain some of its efficacy if it is reintroduced. However, this depends on the resistance mechanism and the fitness of resistant individuals, so it is not guaranteed. This is why resistance management is so important, even when a fungicide is still performing well. Rotating fungicides with different modes of action and integrating other disease management strategies can help slow the development of resistance and preserve the effectiveness of available products.

What has been a defining moment in your research career?

Receiving the John and Petakin Mildenhall Best PhD Award. It gave me the confidence and opportunity to secure a permanent research position in the industry I had always dreamed of working in.

If you could collaborate with any researcher, past or present, who would it be?

Prof Eben Archer.

What is the best advice you’ve ever received?

Read all emails in a positive or neutral tone.

And when deadlines are looming, what’s playing in the background?

Supertramp’s Goodbye Stranger.

If you weren’t a researcher, what would you be doing?

Either forensic pathology or running a plant nursery.

Where do you go to switch off?

Hermanus. Watching the waves with a good glass of wine.

Finally, if your research were a wine, what would it be?

A wooded Chardonnay. Complex, occasionally misunderstood and very susceptible to powdery mildew.