For the Professional Diagnostician

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Tomato Diseases | Bacterial Speck Fact Sheets

Bacterial Speck of Tomato


Foliar symptoms of bacterial spot and speck are identical therefore fruit symptoms should be used to distinguish between the two diseases. If fruit are not provided with the sample additional diagnostic tests should be conducted to confirm the pathogen causing the disease.


  • Black sunken stippling appears early on green fruit.
  • No vascular discoloration will be observed when the stems are split open lengthwise
  • Spots are small (<1/16 inch) and look like “pin-points” or “specks” on the fruit
  • Spots are superficial and can be easily scraped off the fruit surface with a fingernail

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Bacterial streaming from the margin of a leaf, stem or fruit lesion.

Often Confused With

  • Bacterial Spot – Look for large crusty lesions on the fruit with no light green halo as indicators of bacterial spot.
  • Early Blight – Look for lesions with concentric rings and chlorosis as indicators of early blight.

Isolation Media

Pseudomonas F (PF) medium (pdf) is a semi-selective medium for isolating pseudomonads. Colonies of P. syringae pv. tomato and P. syringae pv. syringae are fluorescent on PF medium. After 2 days at 82 °F colonies of both pathovars are creamy, white, round, entire and flat. Colonies on densely populated plates will form small crystals in the medium after 7 days.


Available Rapid Diagnostic Tests

  • Conventional Polymerase Chain Reaction (PCR) assays