Robigalia Roundup LXVI

Phytophthora capsici is a soilborne, oomycete pathogen in the family Peronosporaceae, order Peronosporales, phylum Oomycota. It is heterothallic, producing thick-walled oospores, sporangia and motile zoospores that underpin its explosive polycyclic epidemics under saturated conditions.

Phytophthora capsici has a broad host range spanning more than 20 plant families, with major impacts in Cucurbitaceae, Solanaceae and Fabaceae. Key hosts include capsicum and chilli, tomato, eggplant, cucurbits (pumpkin, squash, cucumber, watermelon, melon) and grain legumes such as snap and lima beans.

The pathogen causes damping-off, root and crown rot, stem lesions, foliar blight and fruit rot, depending on host and growth stage. Field symptoms include water-soaked, rapidly expanding lesions at the soil line, plant wilting and collapse, and firm, dark, sometimes zonate fruit rots that may be covered with sparse white sporulation under humid, warm conditions.

Phytophthora capsici is now documented on all inhabited continents in most major vegetable-producing regions. It is widely present across the Americas, Europe, Asia and parts of Africa, with records from multiple states in the USA, Brazil, China, India and Mediterranean countries.

Management relies on an integrated approach that combines exclusion, cultural, chemical, and host-resistance strategies. Methods include using clean seed and transplants, well-drained or raised beds, irrigation management to avoid saturated soils, long rotations to non-host cereals where feasible, and sanitation to limit the spread of infested soil and water.

Fungicides such as metalaxyl/metalaxyl-M, phosphonates and copper products are used preventatively, but resistance and regulation necessitate rotation of modes of action and integration with tolerant cultivars and decision-support models.

Keep reading on to meet a PhD student researching Phytophthora capsici at Clemson University!

This week, I’m pleased to introduce Priyanka Gupta, a PhD student at Clemson University whose research focuses on the management of soil-borne pathogens.

Priyanka’s first introduction to plant pathology was during her Bachelor’s (Honours) degree in Agriculture at Chaudhary Charan Singh Haryana Agricultural University. Piquing her interest in the field, this led Priyanka to pursue a Master’s in plant pathology, during which she researched the use of unconventional chemicals to induce systemic resistance in chilli (Capsicum annuum L.) against Fusarium wilt. Eager to continue her research in sustainable, non-chemical strategies for managing soil-borne pathogens, Priyanka moved to the United States to pursue her PhD.

Now pursuing a PhD at Clemson University, Priyanka’s research focuses on managing soil-borne pathogens, specifically Phytophthora capsici and Fusarium oxysporum f. sp. niveum, using anaerobic soil disinfestation in organic watermelon production systems. Her work involves quantifying these pathogens and characterising the soil microbiome to better understand how management practices shape pathogen suppression, soil and plant health.

Throughout her Master’s and PhD, Priyanka is very proud to be learning new techniques and instruments, such as digital PCR. She’s also incredibly grateful for the opportunity to make new connections at plant pathology meetings and conferences, and for the support to attend these meetings through travel grants.

Priyanka’s advice for fellow plant pathologists is to “choose a pathosystem that you really care about and learn its biology, epidemiology, and management in detail."

Be sure to connect with Priyanka on LinkedIn to follow her PhD journey!

Have a job, scholarship or event to advertise? List a scholarship, job, or event in Robigalia. I help you promote your opportunity or event to a global network of plant pathologists for free.

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: