"I have several catts and mini-catts with leaves that turn black and fall
off. What causes this? I don't see evidence of insects. Sometimes the
black patch starts with spots throughout the leaf and sometimes it is a
gradually-spreading patch.
I also have some catts with leaves that are almost rose-coloured. They used
to be green. I know this can be a sign of too much light, but they are just
under fluorescents and not many of those. I noticed today that there was an
insect strip close by so I have removed it. It was quite old and not likely
very potent so I don't know if that's the cause. Any ideas would be
appreciated.
Gail Friesen"
Dear Gail:
The spreading black patches may well be a fungus. But given the "rose color" on other plants, I think you have a water quality problem. Often people growing under lights do not apply enough water with each watering to prevent salts from accumulating in the potting mix. A decomposing potting mix would exacerbate this. You might have an excess of zinc or magnesium salts in your water (due to a change in the municipal water source, or a shift to well water), or perhaps you have added a softener to your water system and sodium is now building up in the pots.
Oddly, the tolerance of different species/hybrids to water quality varies, so different plants would show different damage.
Hope this helps,
Dennis
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