Effect of Cultural Practices in Controlling Southern Blight of Potato in the Mid-Atlantic Region

View the project final report

Commodities

• Agronomic: potatoes

Practices

• Crop Production: varieties and cultivars
• Education and Training: extension
• Pest Management: cultural control, integrated pest management, Disease management

Over the past decade, occurrence of potato southern blight caused by Sclerotium rolfsii Sacc. has increased on the Eastern Shore of Virginia (ESVA) and surrounding areas. There is no known potato cultivar resistant to S. rolfsii, and traditional management relying on fumigants and fungicides has provided inconsistent results. Field and laboratory research was conducted in 2017 and 2018 evaluating the effect of four planting dates (PD) and ten cultivars as strategies to reduce the impacts of potato southern blight. Artificial field inoculations were performed between 51 to 73 days post-planting, utilizing a composite inoculum of two S. rolfsii isolates associated with previous ESVA potato southern blight outbreaks. In general, less in-field southern blight incidence was observed for the earlier PDs in both years. In 2018 there was less incidence than compared to 2017. Chipping potato cultivars ‘Atlantic’, ‘Snowden’, and ‘Accumulator’ tended to be more tolerant in early PDs, and only ‘Accumulator’ appeared to be more tolerant in latter PDs. Later PDs also resulted in decreased yield and tuber quality and increased percentage of diseased tubers. ‘Accumulator’ consistently produced the greater marketable tuber yields and least diseased tubers across PDs in both years. ‘Atlantic’ and ‘Snowden’ produced the least disease in the earlier PDs only. There was a significant positive correlation between final southern blight incidence and the percentage of diseased tubers. Furthermore, a significant negative relationship was observed between disease incidence and yield, and the percentage of marketable tubers. The laboratory experiment revealed that ‘Snowden’, ‘Accumulator’, and ‘Atlantic’ had the least S. rolfsii penetration. ‘Adirondack Blue’ in 2017, and ‘Red Norland’, ‘Russet Burbank’, together with ‘Adirondack Blue’ in 2018 had the greatest pathogen penetration. ‘Adirondack Blue’ and ‘Russet Burbank’ had the greater diseased tuber tissue in 2017 and 2018, respectively, whereas ‘Accumulator’ and ‘Atlantic’ provided the least percentage of diseased tubers in 2017 and 2018, respectively. In general, early PDs coupled with tolerant cultivars are recommended as strategies to suppress potato southern blight.

The main goal was to identify potential cultural control options in managing southern blight to ensure the sustainability of potato production in regions impacted by this disease through the following objectives:

1. Evaluate the effect of planting dates on southern blight incidence in potato by establishing field trials examining four different planting dates and assessing disease incidence, yield parameters, and tuber quality.
2. Evaluate the effect of cultivar and the interaction with planting dates on the incidence of southern blight, by initiating field trials with ten popular cultivars and assessing disease incidence, yield parameters, and tuber quality.
3. To screen the effect of potato cultivars on the susceptibility of post-harvest infection by rolfsii.