Bacterial Spot
Xanthomonas spp.
Small dark water-soaked leaf spots that expand and merge. Common on tomato, capsicum and brassicas after warm wet weather.
Not sure it is Bacterial Spot? Photograph it. Every member gets a free Plant Check, one answer for one photo. Pro includes 20 photo checks each month.
Identify from a photoBackground
Several Xanthomonas species cause bacterial spot on vegetables. On tomato and capsicum, the classic symptoms are small dark water-soaked spots on leaves, later dry and papery, often with a yellow halo. On fruit, raised scabby lesions develop. Bacterial spot is typically seed-borne and splash-spread in warm wet weather.
How to identify
- Small dark water-soaked leaf spots, 2-5mm, often with yellow halo
- Older lesions become tan and papery, sometimes with a shot-hole appearance
- Raised scabby lesions on fruit
- On brassicas: V-shaped yellow lesions starting from leaf margin (bacterial black rot)
Life cycle
Bacteria survive on and in seed, crop residue and volunteer plants. Splash-spread by rain and irrigation. Enters through stomata and wounds.
Weather triggers
- Temperature: 20-32°C
- Humidity: >85%
- Rainfall trigger: >5mm
- Warm wet weather, especially with driving rain, is peak risk.
Peak season (southern hemisphere)
Red = active season · Dark red outlined = this month
Affected vegetables & crops
Click any crop to see current prices and growing info.
Climate zones at risk
Organic & low-impact control
- Copper-based bactericides. Regular protectant sprays during wet weather
- Remove and destroy affected leaves and fruit
- Avoid working in the crop when foliage is wet
Chemical control
- Copper is the main option; streptomycin-based bactericides are restricted
Always read product labels. Registrations change.
Prevention
- Use certified clean seed or treat seed with hot water
- Rotate solanaceous and brassica beds on a 3-4 year cycle
- Avoid overhead watering
Companion planting
No direct companion effect.
Biosecurity
Certain strains of Xanthomonas campestris have regulatory significance on brassica seed.
Know when Bacterial Spot is actually about
The calendar above is the season. It cannot tell you what is happening in your street this week. Get the free weekly email, or see live pressure for your own postcode on Pro.
The free weekly garden email
One email a week: what to plant, what to harvest, and what to watch for in your climate zone. Free, and you can stop it in one click.
Live pest pressure, for your postcode
The season tells you it is possible. This tells you it is happening.
- Risk scored for your own postcode, next 7 days
- Queensland fruit fly tracking
- GardenBuddy.au Check: photograph it, get it identified, 20 photo checks each month
- Weekly Pest Alert matched to your zone, season and crops
$59 a year or $7.99 a month. Every paid plan starts with a 30 day free trial. Cancel any time.
Just this one problem? Every member gets a free Plant Check, one photo, one answer.