Bacterial Brown Spot of Orchid

Disease Information

Bacterial Brown Spot

Acidovorax (syn.eudomonas)



The symptoms may appear anywhere on the leaf as a small, soft, water soaked blister. Initially dirty green in color, the infected spot enlarges, coalesces and eventually becomes brown or black, dried up and sunken. It oozes bacteria-laden liquid, particularly when the disease reaches the tip of the leaf. It is most prevalent during the warmer weather.

In Cattleya, the infection enters through wounds on older plants and usually affects only older leaves.

It advances slowly and is rarely fatal.

In Phalaenopsis, the blister-like spots may be surrounded with a yellowish or pale green halo.

Spots coalesce, and the infection spreads rapidly.

If the diseased area invades the crown, the plant will die.


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.

Cultural control

Pseudomonas cattleyais a water-borne pathogen that prefers warm, moist conditions. Reduce humidity and temperature (if possible), eliminate overhead watering and increase air circulation.





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