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Managing Bacterial Diseases of Tomatoes and Peppers

Suggested Management Strategies

Bacterial pathogens are difficult to control — there are no silver bullets. Bacteria are water-loving organisms — they multiply best in water, they are spread in water, and the infection process is usually closely linked with the presence of water. A collection of management strategies must be used to minimize damage to tomato and pepper crops from these diseases. The strategies to consider are:

Preseason Sanitation

  1. Greenhouses can never be "too clean". Contamination from the previous year can provide sufficient inoculum to start an epidemic. A researcher in Michigan recommends that greenhouses be cleaned to the point where your neighbors think you are being excessive! It makes no sense to buy expensive clean seed and inadvertently contaminate it in the greenhouse with carry over pathogens from the previous year.
  2. All greenhouse tables, flats, containers, hoses, etc should be handled as if they are contaminated, and disinfested prior to use for the season. Sterilized soil, potting mix, and pots or flats should be used in the greenhouse.
  3. Irrigation equipment (pipes, tubes, drip lines) used in infested fields should be disinfested before being reused.
  4. All plastic should be removed from the field before a new crop of tomatoes or peppers is planted.
  5. All stakes and ties for tomato production should be disinfested if they are to be reused. One recommendation is to steam treat the stakes or wash them with a bleach solution
  6. Only new crates and boxes which have never been used should be used for shipping transplants. Reusable plastic or wooden containers brought to the field should be cleaned and disinfested before they are reused.

Seed and Transplant Selection

  1. Purchase seed or transplants that are certified disease free.
  2. Select tolerant varieties.
  3. Request treated seed to reduce the chance for contamination. Unfortunately, seed treatments can reduce germination and vigor in some varieties. Seed treatments do not come with a 100% guarantee that the seed will be disease free.

Disease Prevention in the Greenhouse

  1. Scout greenhouses on a weekly basis, looking for any signs of leaf spots or inappropriate wilting among plants.
  2. Keep varieties separated in the greenhouse. The bacteria are rapidly spread in water, and close spacing in the greenhouse is ideal for rapid disease development. Keeping the varieties separate will help you identify problematic varieties.
  3. Destroy volunteer tomato plants and Solanaceous weeds growing in or near the greenhouse and production fields.
  4. Transplants should only be handled when the foliage is dry.

Disease Prevention in the Field

  1. Do not dip or water transplants in crates or boxes — this will effectively spread the bacteria.
  2. Do not mechanically clip or top transplants.
  3. Do not locate fruit or transplant cull piles in or close to production fields.
  4. Clean all transplanting equipment before and after each use.
  5. Workers should not enter the fields if the foliage is wet. People handling the foliage while staking and tying are likely to spread the disease. Damage to the plants provides a site for entry of the bacteria into the plant.
  6. Clippers and pruning tools should be disinfected between plantings and rows.
  7. A 3 year rotation with a nonhost is encouraged.

Disease Management

  1. If a bacterial disease is detected in the greenhouse, consider all plants at the location to be contaminated. Do not attempt to separate healthy from diseased plants...many plants will be contaminated, but will not be showing symptoms.
  2. If a bacterial disease is detected in the field, apply appropriate bactericides. Unfortunately, copper and antibiotic resistant strains of the bacteria are common. Where strains are sensitive to copper, this material can help reduce bacterial populations on the plants.
  3. If bacterial diseases are present in a field, the plants should be incorporated into the soil to encourage the decomposition of debris.
  4. Contact your local Cornell Cooperative Extension Educator for assistance in diagnosing plants with suspicious symptoms

Closing Remarks

Bacterial pathogens are notoriously aggressive and challenge the best grower's management skills. Successful growers have found that following as many prevention strategies as possible is the most effective way to manage bacterial diseases on tomatoes. In this case, an ounce of prevention is truly worth a pound of cure, because effective cures are nonexistent.