Clavibacter Michiganensis

Class: Bacteria
Common Name: Bacterial canker of tomato
Scientific Name: Clavibacter michiganensis
Potential Host:

Tomatoes, potatoes, eggplants, and peppers

Who Am I?

Bacterial canker of tomato is an economically important disease found throughout the world. It’s main host is tomato, but it can infect a few other crops. Outbreaks can cause tomato plants significant damage.

Bacterial canker enters the host plant mainly through hydathodes, stomates, and wounded tissue. After entering, the pathogen can become systemic and move through the xylem tissue.

Once bacterial canker is established on plants in the field, it can easily spread from plant-to-plant by water splashing and contaminated tools on workers clothes and hands. The disease favors relatively high temperatures (24-29 degrees Celsius) and a high relative humidity (80% and above).

Bacterial canker symptoms usually manifest on lower foliage first and include: curling and wilting of leaves and branches. Chlorosis, brown necrosis, and the shriveling of leaf tissue are also common and may develop only on one side of the leaf. With time, vascular tissue turns tan in color and eventually red-brown.

Observing fruit symptoms is useful in diagnosing bacterial canker. Small, round white to yellow spots with brown centers may develop on green fruits.

In advanced stages, pith separates from the vascular tissue along the stem, and as a result, hollowing of the stem occurs.

Control Measures

Monitoring: Inspect the field regularly so bacterial canker can be detected at an early stage.

Disease-free planting materials: Whenever possible, work with high-quality seeds that were pre-checked and found free of the disease. If available, use resistant cultivars. Do not touch wet plants that are infected. Postpone any scheduled practice in the field until foliage is completely dry.

Sanitation: Sanitize all equipment that came into contact with infected plants.

Chemical management is concentrated around preventative spraying applications of copper hydroxide-based products.

*Names marked in red are considered to be highly poisonous to beneficial insects.

*Names marked in green are considered to be organic and IPM (integrated pest management) compatible.

Caution and careful notice should be taken when using any plant protection products (insecticides, fungicides, and herbicides). It is the grower’s sole responsibility to keep track of the legal uses and permissions with respect to the laws in their country and destination markets. Always read the instructions written on labels, and in a case of contradiction, work in accordance to the product label. Keep in mind that information written on the label usually applies to local markets. Pest control products intended for organic farming are generally considered to be less effective in comparison to conventional products. When dealing with organic, biologic, and to some extent a small number of conventional chemical products, a complete eradication of a pest or disease will often require several iterations of a specific treatment or combination of treatments.

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