Bacterial speck (Pseudomonas syringae pv. tomato) infections occur during cool (63 t 75°F) wet conditions.
Introduction to new fields occurs through infected seedlings or seeds. Bacteria spreads locally in splashing water or on field equipment and tools. Bacteria survive up to three years in plant debris, and for several months on plant stakes and equipment.
Symptoms on leaves are concentrated near margins and are most prominent on the undersides, consisting of brown to black spots with a yellow halo. Spots on fruit are scabby, pinpoint-like, and range in color from brown to black. Damage does not penetrate into the flesh.
Bacterial speck is a minor threat in Utah.
- Start examining undersides of leaves soon after planting, especially following cool, wet weather. Continue through early summer.
- Delay planting until cool, wet conditions are over.
- Avoid overhead irrigation.
- Rotate with a non-host crop such as small grains or corn.