North Carolina Plant Disease and Insect Clinic
Plant Disease Fact Sheets

Bacterial Wilt : The "Second Hand" Wilt Effect

Figure 1: Unilateral wilting (wilting on one side of the plant)


Figure 2: Unilateral wilting and chlorosis


Figure 3: Wilt symptoms on tomato


Figure 4: Vascular Discoloration


Figure 5: Bacterial Streaming Test


Figure 6: Bacterial Streaming Test


Map 1: Distribution of Bacterial Wilt


Your Tomatoes and Peppers Might Be at Risk

Emma Lookabaugh, Mina Mila

Tomato and pepper crops may be at risk if planted in old tobacco growing areas. Bacterial wilt (BW) is caused by the bacterium Ralstonia solanacearum. Ralstonia is a tropical/subtropical pathogen that causes disease in numerous crops. Economically important hosts include tobacco (Nicotiana tabacum), tomato (Solanum lycopersicum), potato (S. tuberosum), eggplant (S. melongena), and pepper (Capsicum annuum).   Ralstonia can also infect several common garden plants including zinnias, geraniums, sunflowers, and marigolds. In the United States, BW occurs predominately in the southeast and is most devastating at temperatures >28C. 

The most obvious symptom of BW is unilateral wilting (wilting beginning on one side of the plant), followed by a sudden collapse of the entire plant (Figures 1, 2, 3).  The bacteria plug up the vascular tissue resulting in the plant's inability to transport water from the soil to the leaves. Infected plants wilt and eventually die. At early stages of infection, cutting open an infected stem reveals tan to yellow-brown discoloration of the vascular tissue (Figure 4).  As the pathogen moves up the stem, portions of the pith and cortex become deep brown as they are invaded and destroyed.  

A quick and easy diagnostic test for BW is the bacterial streaming test: After observing vascular discoloration, cut the stem and put it in a glass of water (Figure 5).  Do not disturb the water.  After a few minutes, you should be able to see a thin, milky line of bacteria streaming out of the cut stem (Figure 6).  

In North Carolina, BW has been reported on tobacco crops since 1880.  Tobacco growers know this disease as Granville wilt, named for Granville County where BW was first reported on tobacco.  Since then, BW has been widely distributed across the southeast (Map 1).  In a recent study sponsored by the Tobacco Trust Fund, bacterial wilt strains collected from tobacco crops were used to infect tomato and pepper plants.  Bacterial strains collected from tomato crops were used to infect tobacco plants.  Results indicate that strains from tobacco were able to infect tomatoes and peppers, but strains from tomatoes were not able to infect tobacco.  

Ralstonia solanacearum can survive in most soils for years without a host present.  Land previously planted with tobacco may have Ralstonia infested soil. If you are a solanaceous crop grower or a homeowner interested in planting tomatoes or peppers in your home landscape, be sure to acquire a field pest history.  

BW strains from tobacco kill both tomato and pepper crops, so your plants may be at risk.

 

We would like to thank the N.C. Tobacco Trust Fund Commission for financial support towards this research.