Bacterial Speck

Bacterial speck may sound redundant - we all know bacteria are tiny - but bacterial speck is a bacterial disease of tomatoes that can be controlled with a speck of good cultural practices.

Bacterial speck looks a lot like bacterial spot and bacterial canker, but it is less likely to be fatal. All three diseases appear as small brown or black lesions on leaves, stems, and fruit. These lesions may merge into larger, irregularly-shaped areas. There is normally a yellow halo around these lesions and the interior tissue dies rather quickly. Most of these lesions are found near leaf edges (margins). On fruit, the lesions look like tiny black bumps.

Bacterial speck on tomato (Scot Nelson) Public Domain

Bacterial speck lifecycle

Bacterial speck is caused by Pseudomonas syringae pv. tomato, a cousin of the bacteria that cause angular leafspot, citrus blast, and leaf spot. This bacteria is found in soil and on seeds. Seeds from diseased fruits should not be planted the following season, or you will simply continue the process in your garden. These bacterium can remain dormant for a very long time, until the weather turns cool and damp. Then they start growing like crazy. The bacteria are frequently splashed onto leaf surfaces by rain and overhead watering.

Bacterial speck control

Fixed copper sprays and good air circulation are your best preventative measures. You can also delay spring planting until after temperatures warm up, and avoid overhead watering.  Properly spacing plants can reduce the spread of infection.

Diseased fruits are safe to eat, simply cut out the infected areas and toss them in the trash (or feed them to your chickens). Diseased plants should not be composted. Instead, toss them in the garbage to reduce the likelihood of reinfection.