Carnation bacterial wilt bacterium

Taxonomic position and pathogen nature. Burkholderia caryophylli is a Gram-negative, motile, rod-shaped bacterium belonging to the Burkholderiaceae family. It is a soil-borne phytopathogen that primarily impacts ornamental crops. Formerly classified as Pseudomonas caryophylli, it was reclassified due to advanced taxonomic analysis, highlighting its distinct physiological characteristics as a vascular plant pathogen.

Diseases and host plants. This bacterium is the primary cause of bacterial wilt in carnations (Dianthus caryophyllus). It is a systemic disease that severely affects both greenhouse-grown and field-cultivated carnations. The pathogen enters the plant through the root system or via small wounds on the stem, ultimately colonizing the xylem and causing systemic plant failure.

Biology and lifecycle. The bacterium persists in infected plant debris, soil, and contaminated propagating material. Transmission commonly occurs through irrigation water, contaminated pruning tools, and infected cuttings. Within the plant, the bacteria multiply rapidly in the vascular bundles, producing extracellular polysaccharides that physically obstruct water transport, leading to physiological drought and eventual wilting.

Development conditions and damage. The disease development is favored by warm temperatures (20–25°C) and high humidity. The damage caused by Burkholderia caryophylli is significant, often leading to total crop loss. Typical symptoms include:

• wilting and yellowing of the lower leaves;
• longitudinal cracks at the base of the stem;
• brown discoloration of the vascular bundles visible on stem cross-sections;
• rapid collapse of the plant foliage.

Protection and control measures. Management is primarily prophylactic. Growers must prioritize the use of disease-free, certified mother stock. Greenhouse sanitation is critical, including the sterilization of substrates, frequent disinfection of cutting tools using appropriate bactericides or alcohol, and the removal and destruction of symptomatic plants. Once established, the pathogen is extremely difficult to eradicate, making early detection and strict hygiene the most effective defenses.