🍅 Bacterial Spot

Xanthomonas species complex
The tomato-and-pepper bacterium that scorches leaves and scabs fruit — and laughs at your spray bottle once it is in.

Signs and symptoms

Water-soaked leaf spots that turn dark and greasy-looking, sometimes with yellow halos. Dead centres drop out, leaving a shot-hole look, and bad infections scorch leaves from the bottom up. On fruit, lesions start as slightly raised blisters and become raised and scabby — NOT sunken. Sunken fruit lesions point more to target spot, so that raised-versus-sunken check is worth making. In Florida tomato, X. perforans race T4 is now the dominant race. The complex behind it: X. euvesicatoria (T1), X. vesicatoria / X. gardneri (T2), and X. perforans (T3/T4). It spreads on contaminated seed and transplants and in wind-driven rain.

Pepper with bacterial spot caused by Xanthomonas
Bacterial spot (Xanthomonas) on pepper. Photo: Chelsea Hardin, CC0.
Pepper leaves with bacterial spot caused by Xanthomonas
Bacterial spot (Xanthomonas) on pepper. Photo: Chelsea Hardin, CC0.
Pepper plant with bacterial spot caused by Xanthomonas
Bacterial spot (Xanthomonas) on pepper. Photo: Scot Nelson, CC0.

Plants it attacks

Tomato and pepper. This is the tomato/pepper bacterial spot complex with its own races and fruit symptoms — not the same page as the general bacterial leaf spot guide.

What to do

  • Remove badly affected leaves promptly and bag them — do not compost.
  • Do not handle wet plants, and disinfect tools between plants; wet foliage is when this bacterium travels best.
  • Stop overhead watering and switch to watering at the base.
  • Copper is a labelled later option only, and here is the honest version: copper protects, it does not cure. Sprayed on clean leaves it can shield them; it will not heal spots that are already there. Always follow the label.

Prevention

Start with certified disease-free seed and transplants — this is the single most important step, since contaminated transplants are how many gardens get it. Rotate crops, space plants for air flow, water at the base, and choose resistant varieties where available.

Nerdy fact: Bacterial spot has a race problem: as growers planted varieties resistant to one race, another took over. That is why X. perforans race T4 now dominates Florida tomato — the pathogen keeps changing its jersey.

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