Tomato Bacterial Canker

The bacterium Clavibacter michiganense pv. michiganense is responsible for the occurrence of bacterial canker in tomato plants. This infectious disease affects both fresh-market and processing tomatoes, leading to decreased yields and premature fruit drop. The development of white blisters on infected tomatoes significantly diminishes their value in the fresh-market. Bacterial canker has the potential to rapidly spread throughout a crop, resulting in substantial losses. Identifying the disease at an early stage is crucial in order to effectively control its spread.

Disease Cycle

Bacterial canker can be introduced to the garden through infected seeds or transplants, even if they do not display any disease symptoms.

The bacteria exude from the cankers and easily spread to other plants. This transmission can occur through water splashing from rain or irrigation, as well as through the hands and tools of workers.

The bacterium has the ability to survive for up to three years on plant debris and remains viable for several months on stakes and equipment. Additionally, it can infect and persist on nightshades and closely related weeds, as well as tomato plants that grow from fallen fruit of the previous season.

Disease progression is particularly favored by warm temperatures and high moisture or relative humidity levels.

Signs and Symptoms

Symptoms associated with bacterial canker manifest in various parts of the tomato plant, primarily affecting the above-ground portions. However, the initial signs tend to emerge on older leaves and their appearance can vary depending on factors such as plant age, infection type, and environmental conditions.

Seedlings are prone to developing small, raised spots on their leaves, which are white in color. In severe cases, these seedlings may undergo complete wilting and eventual death.

Infected leaves exhibit the formation of yellow to tan patches between the veins. The leaf edges turn brown and are accompanied by a yellow border. Dark, sunken veins also appear on the leaves and petioles. Lower leaves tend to wilt, often on one side only, and in severe instances, the entire plant may collapse and perish.

When the stem is dissected, brown streaks become apparent within the vascular system. Long, brown cankers form on the stem, leading to its splitting. Upon squeezing, a yellow sticky fluid may be released from the cut stem.

Fruit affected by bacterial canker develops small, creamy white spots with tan or brown centers, resembling “bird’s eye” spots. The fruit’s surface may exhibit a netted or marbled appearance.

Disease Management

Chemical control

To achieve effective control of bacterial canker disease, it is recommended to utilize copper-based fungicides. Copper has the ability to inhibit and impede the movement of bacteria in the soil.

Here are some examples of copper-based fungicides commonly used:

  • GREENCOP 500WP
  • TRINITY GOLD 452 WP
  • COLONIZER 440WP

Furthermore, crops that are sprayed with BIODISTINCTION XTRA exhibit enhanced protection against bacterial infections.

Another method to suppress bacterial activity within the plant is through the application of a drench treatment using PYRAMID 700WP.

It is important to note that these recommendations contribute to effective control strategies for bacterial canker disease.

Non-chemical control methods

  • Utilize disease-free or certified planting materials.
  • Promptly remove old tomato plants after the final harvest.
  • Prevent the growth of volunteer plants between seasons or among cover crops, as they can serve as a reservoir for the disease.
  • Manage solanaceous weeds, such as nightshades, in and around the crop.
  • Avoid rotating or intercropping tomato plants with crops from the same family, such as capsicum, potato, or eggplant.
  • Ensure proper fertilization and irrigation, as both stressed and excessively vigorous plants can be more susceptible to disease.
  • Prefer drip irrigation over overhead irrigation to minimize the spread of the pathogen through water splashing. If overhead irrigation is the only option, water during the day to allow ample drying time for the plants before nightfall.
  • Regularly monitor the crops for bacterial and other diseases.
  • Refrain from working in the fields when the plants are wet.
  • Thoroughly disinfect spray equipment and machinery with a general disinfectant before and after use.
  • Do not save seeds from infected plants.
  • Opt for tomato varieties that have tolerance or resistance to the disease.

Note:

  • When spraying fungicides, it is recommended to mix them with INTEGRA at a rate of 3ml per 20 liters. INTEGRA acts as a sticker, spreader, and penetrant, enhancing the fungicide’s effectiveness.
  • Providing proper nutrition to the crops improves their ability to resist infections.
  • Timely disease control measures are crucial for effective management.

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