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Xanthomonas euvesicatoria and related Xanthomonas species Xanthomonas euvesicatoria Jones et al., 2006 (with X. vesicatoria, X. perforans and X. gardneri) · formerly or also: Xanthomonas campestris pv. vesicatoria
Bacterial spot covers tomato and pepper leaves with small, dark, greasy spots and the fruit with raised, scabby lesions. In warm, wet weather leaves drop, fruit sunburns and its market value falls. Four related Xanthomonas species cause it; they are carried on seed and transplants and spread by rain and overhead irrigation. It is one of the hardest diseases of these crops to control in humid climates.
Bacterial spot of tomato and pepper is caused by Xanthomonas euvesicatoria and related Xanthomonas species Xanthomonas euvesicatoria Jones et al., 2006 (with X. vesicatoria, X. perforans and X. gardneri), a bacterium (Gram-negative) (order Lysobacterales (formerly Xanthomonadales), family Lysobacteraceae).
Older or alternative scientific names: Xanthomonas campestris pv. vesicatoria.
Found wherever tomatoes and peppers are grown in warm, humid or rainy conditions: the Americas, Africa, South and East Asia, Europe and Oceania. Different species dominate in different regions.
| Region | Status |
|---|---|
| Americas | Widespread; X. perforans dominant on tomato in parts of North America |
| Africa and the Middle East | Widespread |
| Asia | Widespread |
| Europe and Oceania | Present; regulated in some areas |
Rod-shaped bacteria that form yellow colonies; species and races are identified in the laboratory. They survive on seed, in crop debris, on volunteer plants and in transplant production. The four species are X. euvesicatoria, X. vesicatoria, X. perforans and X. gardneri (now X. hortorum pv. gardneri); X. gardneri tolerates cooler weather than the others.
| Crop stage | What you see |
|---|---|
| Transplants and young plants | Small, water-soaked, dark spots on leaves; spots may have yellow halos. |
| Established plants | Many small dark brown to black spots, often merging; leaves yellow and drop, especially lower leaves; spots on stems and leaf stalks. |
| Fruit | Raised, dark, scabby, rough spots on green fruit, sometimes with a water-soaked halo; reduced market quality. |
Bacteria from infected seed or transplants or from debris are splashed by rain and overhead irrigation onto leaves and enter through pores and wounds. Warm, wet weather and wind-driven rain spread the disease quickly through a field; handling wet plants spreads it too.
| Stage | Duration | Notes |
|---|---|---|
| Survival | Seed, debris, volunteers | Seed is the main long-distance route. |
| Infection | During warm, wet periods | Through stomata and wounds. |
| Lesion development | About 5-10 days | Bacterial ooze in wet weather. |
| Spread | Repeated cycles | Rain splash, irrigation, handling. |
Most severe at about 24-30 °C with rain, high humidity and wind-driven rain; dry weather slows it.
Many cycles in warm, wet seasons.
Warm, wet weather; overhead irrigation; infected seed and transplants; working in wet fields; and continuous solanaceous cropping.
There is no numeric economic threshold; protection is preventive from transplanting in warm, wet seasons, combined with clean seed and transplants.
Thresholds are local. They depend on crop price, control cost, variety and natural-enemy activity, so use the figure your local extension service publishes where one exists.
Defoliation and fruit spotting cause yield and quality losses of 10-50% in wet seasons, and fruit for fresh markets may be rejected.
Control works best as a sequence: prevent, monitor, then act only when a threshold or a risk forecast says so, using the least disruptive option that works.
Copper-based protectants, often combined with other products, are the main chemical tool, but copper-resistant strains are widespread; plant defence inducers are used in some regions. What is registered differs by country and changes over time; follow the label and your local plant-protection authority.
| Scheme | Group | Mode of action | Notes |
|---|---|---|---|
| FRAC | M01 | Inorganic (copper) - multi-site | Copper-resistant strains widespread. |
| FRAC | P01 | Host plant defence induction (benzothiadiazoles) | Preventive where registered. |
| FRAC | M03 | Dithiocarbamates and relatives (multi-site), as a partner with copper | Improves copper activity. |
Tomato and pepper (sweet and hot); some strains infect other solanaceous plants such as nightshades.
How to grow the crop well is the first line of defence. Laisha's free grow guides cover each crop from sowing to harvest:
Written by Laisha from the sources above, in its own words. This page is general reference, not a prescription: confirm identification locally and follow the label and your plant-protection authority.