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Bacterial canker of tomato: how to recognise and treat it

Disease

Bacterial canker of tomato — Photo: Mary Ann Hansen, Virginia Polytechnic Institute and State University, Bugwood.org, CC BY 3.0 us, Wikimedia Commons

Symptoms

Oldest leaves curl, yellow and wilt, often on one side of a leaf or plant only; leaf edges turn brown as if scorched.
Light, then dark streaks on stems and cankers at the nodes; the pith inside the stem turns yellow to reddish-brown.
Bird's-eye spots on fruit: small spots about 3 mm across with a brown centre and a white halo, often near the stalk.

Organic treatment

Pull out and destroy plants with wilting and streaked stems; do not compost them.
Do not prune, tie or handle plants while they are wet — hands and tools spread the bacteria.
Copper sprays can help protect healthy plants nearby in wet weather; they do not cure infected ones. Follow the label.

Chemical treatment

No spray cures bacterial canker. Copper-based bactericides (for example copper hydroxide) only protect healthy plants; follow the label dose and pre-harvest interval.

Reference information, not a guarantee. Read and follow the label of any product: dose, safety and the days to wait before harvest.

Prevention

Sow certified seed and plant only healthy transplants; never save seed from infected plants.
Keep tomatoes and peppers out of the bed for at least 3 years and dig in or remove all plant debris after harvest.
Clean stakes, cages, trays and tools at the end of the season with a bleach solution (0.5–1% sodium hypochlorite); the bacteria survive for months on wooden stakes.
Remove nightshade weeds, which can carry the bacteria.

Plants it affects

Tomato

Sources

Figures checked against these sources.