Bacterial Spot & Speck: Identification & Natural Management

Bacterial Spot & Speck

Bacterial spot and speck (Xanthomonas and Pseudomonas) cause water-soaked leaf and fruit lesions in tomato, pepper, stone fruit and other crops, spreading fast in warm, wet weather. Bacterial diseases cannot be cured once established, so the Vegalab program supports protection and plant defense — a Spore Control program plus strict sanitation and clean seed.

Common crops affected

Tomato
Pepper
Peach
Stone fruit

What is it?

These are bacterial pathogens that enter through stomata and wounds and multiply in wet conditions, producing spots on leaves, stems and fruit. Because they're bacterial, the goal is protection of healthy tissue and slowing spread — not cure.

How to identify it

Small, dark, water-soaked spots on leaves, often with a yellow halo; spots may merge and tatter the leaf.
Raised, scabby or sunken spots on fruit, downgrading quality.
Rapid spread after rain, overhead irrigation, wind-driven storms or handling.
Defoliation and fruit blemishing in severe outbreaks.

Life cycle & spread

Survives on debris, seed and volunteers; spreads in water (splash, overhead irrigation, storms) and on hands/tools; enters through natural openings and wounds; multiplies fast in warm, humid weather.

Conditions that favour it

Warm, wet, humid weather; overhead irrigation; wind-driven rain and hail wounds; contaminated seed/transplants and handling.

Damage and how it spreads

Leaf spotting and defoliation cut photosynthesis and yield; fruit lesions downgrade or cull produce; once established it can move quickly through a crop.

Monitoring & scouting

Watch after warm wet/stormy weather; scout new growth and fruit; act preventively and tighten sanitation rather than expecting a cure.

How to control it

Use clean seed/transplants, avoid working plants when wet, switch to drip from overhead, remove infected debris, and apply protectant programs preventively to protect healthy tissue and support plant defense.

Role	Product	Use
Primary control	Spore Control

Preventing it next season

Clean seed/transplants, drip vs overhead irrigation, sanitation and tool hygiene, avoid handling wet plants, resistant varieties where available, and rotation.

Not sure this is what's affecting your crop? Ask an agronomist about your crop →

Claims and product availability vary by jurisdiction. Always read and follow the product label.

Frequently asked questions

Can bacterial spot be cured?

No — bacterial diseases can't be cured once established. The program protects healthy tissue and slows spread, so prevention and sanitation are essential.

What does Vegalab recommend?

A preventive Spore Control program plus clean seed, drip irrigation, sanitation and avoiding handling wet plants.

How does it spread?

In water — splash, overhead irrigation, storms — and on hands and tools, entering through natural openings and wounds.

Which crops are affected?

Tomato, pepper, stone fruit (bacterial spot of peach) and other vegetables and fruit.

Why avoid working plants when wet?

Bacteria spread readily in water films, so handling wet plants moves the disease through the crop.