Field Identification
Water-soaked specks that yellow and fall out on tomatoes and peppers, or stay angular on cucurbits bounded by veins—caused by several Xanthomonas pathovars. Spread by splash, tools, hands, and infected seed.
Halos may appear around spots on some hosts; under humid conditions lesions look greasy; bacterial streaming can be seen in microscope mounts. Distinguish from Septoria by lack of tiny black pycnidia.
How to Deal With It
Organic Control Methods
Copper-based protectants on a tight schedule through wet periods; Bacillus subtilis biofungicides as a rotational option—start before symptoms, since no organic spray reliably eradicates established bacterial infections.
Serenade (Bacillus subtilis) and other antagonist sprays give partial suppression; must start early.
Stake and prune for airflow; drip irrigate; work when foliage is dry; rotate families; hot-water treat seed where protocols exist; remove volunteers.
Avoid high-pressure sprays that wound leaves; use one-way harvest paths.
Purchase certified transplants; disinfect pruning tools between plants in outbreaks.
Let Nature Handle It
Natural Enemies
- Bacillus subtilis
- Pseudomonas fluorescens
- Competitive Epiphytes