This disease, caused by the bacterium Pseudomonas syringae pv. tomato, does not affect pepper or other solanaceous crops but may survive on nonhost plants. Tiny, 1 ⁄16-inch-diameter, dark spots appear on leaves, surrounded by yellow halos.
However, as with bacterial spot and bacterial canker, the fruit symptoms are most characteristic. The numerous specks that develop on young green fruit are slightly raised, 1 ⁄32 to 1 ⁄16 inch in diameter, and have well-defined margins (Figure 14). The specks are considerably smaller than the spots caused by bacterial spot, do not penetrate the fruit deeply, and can be scraped off with a fingernail. Although bacterial speck seldom reduces yields greatly, it can harm fruit quality. Infection is favored by cool (less than 70° F), wet conditions.
Epidemics often follow rainstorms that cause abrasion of leaves and splash soil onto the foliage.P. syringae pv. tomato overwinters in seed, in plant debris, in soil, and on many other plants. To control bacterial speck, follow the same cultural measures as for Septoria leaf spot. Plant only disease-free transplants.
Destroying weeds around a tomato field or garden will help to reduce survival of the causal bacterium. A fixed copper product can help control spread of bacterial speck if applications begin when the first symptoms appear.