|Bacterial brown spot|
|Two onions showing signs of center rot caused by P. ananatis|
| Brown spot
Bacterial brown spot (Pantoea ananatis) is a Gram-negative bacteria of the family Enterobacteriaceae.
Foliar symptoms of center rot are typically observed as severe chlorosis or bleaching of one or more of the center leaves of infected onions. Infected leaves are usually collapsed and hang down beside the onion neck. In harvested bulbs, reddish, collapsed scales near the neck area have been associated with center rot. 
Some growers apply a regular application of a copper-based pesticide for center rot although some experts do not consider this an effective treatment. Growers avoid onion cultivars that have been documented to be more susceptible to center rot. Some growers plant varieties that mature earlier to reduce the risk of infection.