Potato growers and agricultural professionals across Europe are facing an emerging challenge as phytoplasma infections, particularly those caused by Candidatus Phytoplasma solani (the agent responsible for Stolbur disease), are being detected in seed potato stocks. The Netherlands Inspection Service for Horticulture (NAK) has been preparing since June for the potential appearance of Stolbur in seed potatoes, prompted by reports of its expanding range in neighboring countries.
The Stolbur Threat and Regulatory Status
Candidatus Phytoplasma solani holds a RNQP (Regulated Non-Quarantine Pest) status in European legislation with a zero tolerance threshold in seed potatoes. This bacterial pathogen causes severe symptoms in potatoes including leaf and stem deformations, aerial tuber formation, pearl tubers, and rubbery-textured tubers that render crops unmarketable. The economic impact can be devastating, with infected lots subject to immediate rejection under current certification schemes.
Vector Expansion and Climate Connections
The primary vector for Stolbur disease, the planthopper Hyalesthes obsoletus, is experiencing expanded range and population growth linked to warming temperatures. Research indicates that for every 1°C increase in average temperature, planthopper populations can increase by 10-15%, significantly elevating disease transmission risk. Compounding this threat, another pathogen—Candidatus Arsenophonus phytopathogenicus, responsible for Syndrome Basses Richesses (SBR) in sugar beets—is spreading through the same vector species, creating a complex disease pressure scenario.
Current Findings and Surveillance Efforts
While NAK has confirmed the first phytoplasma infections in seed potatoes, no Stolbur-specific infections have been identified to date. The diagnostic laboratory has detected other phytoplasma species not currently regulated at the European level, allowing affected seed lots to remain in certification. Comprehensive surveillance efforts initiated in June now include monitoring aphid traps for planthopper presence, though species identification challenges remain due to the diversity of captured insects.
Global Context and Production Impact
Phytoplasma diseases cause estimated annual yield losses of 10-30% in affected potato production areas globally. In recent outbreaks in Eastern Europe, some regions reported complete crop failures in infected fields. The Food and Agriculture Organization (FAO) has noted a 27% increase in phytoplasma-related crop issues over the past decade, correlating with changing climate patterns.
Management Recommendations and Future Directions
The NAK is developing revised protocols for handling non-regulated phytoplasma infections through consultation with advisory boards and standing committees. Current recommendations for growers include:
- Implementing enhanced vector monitoring using yellow sticky traps and suction traps
- Maintaining border vegetation management to reduce vector habitat
- Considering insecticide treatments during critical vector flight periods
- Sourcing certified disease-free seed potatoes from reputable suppliers
Ongoing research focuses on developing resistant potato varieties and improving molecular detection methods for earlier and more accurate pathogen identification.
The emergence and spread of phytoplasma infections in European seed potatoes represents a significant challenge requiring coordinated response from growers, certification agencies, and researchers. While Stolbur disease specifically has not yet been confirmed in Dutch seed potatoes, the detection of related phytoplasmas signals the need for enhanced vigilance and adapted management strategies. The expanding range of vector insects due to climate change, combined with the zero-tolerance regulatory status for Stolbur, creates a complex landscape for potato producers. Continued investment in surveillance, research on resistant varieties, and development of rapid diagnostic tools will be essential for protecting potato production against this growing threat.
