Blackleg usually first shows as water-soaked lesions at the base of the stem. The lesions later coalesce, darken and progress up the stem. The internal tissues of the stem rot and turn black, hindering the adequate supply of water and nutrients to the aerial parts of the plants. Leaves on affected stems may wilt and become first chlorotic and later brown, with their margins curled. Plants may collapse or can be easily pulled out from the soil. Tubers generally start to blacken and rot at the stolon attachment site. As the disease progresses either the entire tuber or just the inner core might decay.
Disease development usually starts with the rotting of the seed tuber before or soon after emergence. Moist conditions favor the development of the rot. Planting sites with high soil compaction and waterlogging are especially vulnerable to blackleg. The bacterium enters the plant via rotten roots or dead leaves near the ground. Damage of the plants from insects or tools can result in wounds that serve as entry points for the pathogen.
No biological approach is possible against the bacteria
Always consider an integrated approach with preventive measures together with biological treatments if available. To prevent the spread of the pathogen copper compounds may be used. However, such compounds may harm the environment and human health