Question

Cymbidium spots   QUESTION: Wayne:
See attached image.  Small black spots (1-3mm long)appeared about 1 month ago on the older foliage. New growth looks healthy. These spots extend 3-4 inches from the very tip. Spots appear quite uniformly distributed near the tip areas. Also noted was black tips, again on older scattered foliage. Plant is about 2-3 ft tall. I surmised a root related stress. Pot seems a bit small. Have not examined roots.

Your thoughts.

Steve

ANSWER: Steve, unfortunately this is a fairly common problem with cymbidiums and thin leaved varieties in general.  It appears to be caused by one of several fungi.  The entire plant (upper and lower sides of the leaves) should be sprayed with a copper-based fungicide.  While this will not remove the damage already done, it seems to be quite effective in preventing the spread to newly emerging growth. This spraying should be repeated every 2-3 weeks during the growing season.  It has the unpleasant effects of leaving a build-up of copper salt on the leaves.

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QUESTION: Thanks Wayne for the information.
Can you recommend a particular fungicide? Can you get any phytotoxic effects?

What fungi are the most common ones responsible?

Steve

Answer
Steve, I have used Kocide (copper hydroxide) without phytochemical consequences.  Be sure to follow the label. We need a fairly broad spectrum control because it could be one of the rust group of fungi or the leaf spot group of fungi. If you can obtain a specific identification of the fungus, this might help with a more targeted fungicide. Other fungicides which I have not tried include captan, zineb, or Plantvax- 75w.