Scab
Pseudomonas gladioli
What is Gladiolus Bacterial Scab (Burkholderia gladioli)?
Gladiolus Bacterial Scab, caused by Burkholderia gladioli pv. gladioli (formerly Pseudomonas gladioli pv. gladioli). It doesn't kill the plants, and corms usually produce normal flower spikes unless severely affected. The bacteria can be introduced through infected corms or survive from a previous planting. Symptoms include shallow, sunken black lesions on corms with a definite rim and a hard, shiny black layer. Lesions are more common at the base of the corms, while Stromatinia lesions are prevalent in the upper portion and leaf scar region.
How does Gladiolus Bacterial Scab (Burkholderia gladioli) occur?
The bacterium enters gladiolus plants through wounds caused by insects or mechanical damage. It then proliferates within the plant tissue and releases toxins that harm the plant cells. The damaged cells eventually die, leading to the formation of scabs on the corm's surface. These scabs can vary in color, ranging from black, and brown, to gray, and can reach up to 1 cm in diameter. The bacterium can persist in the soil for several years and can be transmitted between plants through water, tools, and human activities.
Symptoms
1 - Effects on Plants
• Bacterial scab is a destructive disease that causes the death of cells. This disease negatively impacts flower production, leading to reduced yields. Additionally, scabs increase the plants' susceptibility to other diseases, further compromising their health and overall productivity.
2 - Effects on Soil and the Environment
• Bacterial scab has significant impacts on the soil and environment. The bacterium responsible can persist in the soil for extended periods, leading to contamination. • The disease spreads through water, tools, and human activities, challenging future gladiolus cultivation. Additionally, bacterial scab contaminates water supplies and hinders crop growth, posing risks to animals and humans.
Solutions
1 - Preventions
• Use scab-free corms for planting. Obtain corms from reputable dealers who test for diseases and sell only healthy corms. • Avoid using corms from heavily scab-infested soil. • Keep corms dry before and after planting as bacterial scab is more likely to occur in wet conditions. • Avoid planting gladiolus in the same area for at least two to three years to break the disease cycle.
2 - Balanced Fertilizer and Bulb mite control
• Use a balanced fertilizer to promote strong and healthy plant growth, reducing susceptibility to diseases. • Manage bulb mite populations to prevent feeding wounds. • Use insecticides or cultural practices to control mites.
