Southern bacterial wilt of tomato is caused by the soil-borne bacterium Ralstonia solanacearum (formerly known as Pseudomonas solanacearum). It is a widespread and potentially devastating disease that affects solanaceous crops and a wide range of ornamentals in the tropical and subtropical regions of the world. The disease develops in high temperatures (over 85°F) and moist soils and is very persistent if introduced. The pathogen enters through microscopic wounds (often injured by insects, cultivation, or transplanting) of susceptible host plants under favorable disease conditions. The bacterium clogs the vascular tissue within the stem and prevents water and nutrients from moving throughout the plant where eventual death of the plant occurs.
The pathogen can affect a wide variety of hosts including tomato, tobacco, potato, eggplant, pepper, sunflower and other solanaceous plants and a wide range of ornamentals including hollyhock, nasturtium, zinnia, marigold, dahlia, geranium and others.
Initial stages of the disease include a wilted appearance of the youngest leaves. As the disease progresses, the base of the plant may show brown cankers, root rot, and a cross section of an infected stem may show a brown discoloration of the vascular tissue. The plant eventually becomes permanently wilted and death occurs. A freshly cut stem at the base of the plant placed in water can also show a stream of a white slimy substance that is a strong indicator of the bacterium present in the vascular tissue.
Bacterial wilt can be very difficult to manage once present in the field. There are no chemical controls that provide effective control. Cultural practices can provide some control of disease incidence. Crop rotation and planting cover crops of non-susceptible plants (i.e. corn, rye, beans, cabbage) can reduce soilborne populations of the pathogen.
The use of bacterial wilt resistant rootstocks has been used successfully in fields where bacterial wilt is prevalent or widespread. A list of resistant rootstocks is available here. For more information on the use of grafted vegetables, visit the Vegetable Grafting website.
For assistance with a specific problem, contact your local North Carolina Cooperative Extension center.
Publication date: Dec. 12, 2017
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