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Bacterial wilt and canker of tomato appears on stem and tomatoes. Photo by Heinz USA, Bugwood.org. -
Bacterial wilt and canker of tomato on leaves of tomato plant. Photo by Gerald Holmes, Strawberry Center, Cal Poly San Luis Obispo, Bugwood.org. -
Stem showing pith decay caused by bacterial canker and wilt of tomatoes. Photo by Paul Bachi, University of Kentucky Research and Education Center, Bugwood.org. -
Bird's-eye spots on tomato caused by bacterial wilt and canker. Photo by Mary Ann Hansen, Virginia Polytechnic Institute and State University, Bugwood.org.
Scientific name: Clavibacter michiganensis subsp. michiganensis (Cmm)
Native range: first described in Michigan in 1909
At Risk
Cmm affects solanaceous plants including tomato, pepper, eggplant and potato. It is most pathogenic in tomato. Solanaceous weeds, such as nightshade, are also potential hosts and may act as a reservoir for the bacteria.
Once introduced, Cmm can be a significant problem in greenhouses and high tunnel tomato production. In gardens and field-grown tomatoes, bacterial canker can occur but is only severe when weather conditions favor disease.
Distribution
This pathogen occurs in tomato production areas worldwide but has only occasionally caused significant production issues. Before 2015, the occurrence and distribution of bacterial canker of tomato in Minnesota were unknown. Since then, the Minnesota Department of Agriculture (MDA) surveys have identified Cmm in 17 counties in Minnesota.
Biology
Clavibacter michiganensis subsp. michiganensis (Cmm) causes bacterial wilt and canker of tomatoes. It is a major issue for tomato production globally and spread easily through infected seeds or transplants.
Once introduced to a growing area, Cmm can persist in host plants and plant residue for years. However, it survives only briefly in soil without host material. There is no cure for infected plants, so the best defense is to avoid the introduction of contaminated seeds or plants into growing areas.
Identification
A laboratory test is required to confirm the presence of Cmm. Testing is available through the University of Minnesota Plant Disease Clinic.
Symptoms of infection may include:
- yellowing, browning or wilting of leaves
- stems with yellow to brownish pith (the center of the stem)
- fruits with raised yellow or brown spots surrounded by lighter colored halos
Look-Alikes
Many other tomato diseases occur in Minnesota and can resemble bacterial cancer. For help with diagnosis, visit the University of Minnesota plant disease webpage.
Regulatory Status: Non-Regulated
There are no federal, state or local regulations for this pathogen. However, the sale or export of tomato seed may require documentation showing that the pathogen is not present in the seed.
What Can Be Done?
- Buy seeds and plants only from trusted, disease-free sources.
- Be cautious when planting pepper or other solanaceous crops near tomatoes as these can also carry the pathogen.
- Avoid introducing Cmm into gardens and greenhouses.
The Minnesota Department of Agriculture is currently monitoring for Cmm through our pathways survey.
Contact the MDA via Report a Pest if you suspect bacterial wilt and canker of tomato.
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