http://www.google.ca/url?sa=t&rct=j&...70810081,d.aWw
(page 25) Bacterial Brown Spot. Acidovorax (syn. Pseudomonas).
Prevention: Pseudomonas cattleya is a water-borne pathogen that prefers warm, moist conditions. Reduce humidity and temperature (if possible), eliminate overhead watering and increase air circulation.
Treatment: Immediately remove infected tissue and spray the plant with a bactericide like Physan or copper compounds following label instructions. Disinfect growing area with 10% bleach solution.