Brown spots surrounded by yellow on Stanhopea leaves

[turbosloth10]

I have a Stanhopea jenischiana that lives in moss in a net pot hanging over my kitchen sink. For the past several months, it has been slowly developing dead brown spots on two of the leaves, the spots being dry and surrounded by yellowish leaf tissue. The plant is otherwise robust, with tons of healthy looking root growth and three other unaffected leaves. It is also currently putting out two new growths.

The plant hangs next to three other plants, none of which show any issues. The leaves are never wet, and the room is reasonably humid being over my kitchen sink, but not crazy wet or anything. The two leaves that are affected are also nearest to the window, though it is not a terribly bright window.

Any ideas on what this could be? I've tried searching the internet and no common orchid pathogens seem to fit perfectly. I would suspect it could be something related to sun exposure because of the leaves proximity to the window, but the spots don't really look like sunburn to me. Any advice would be appreciated!

[SouthPark]

If the issue isn't due to an element deficiency or nutrient deficiency or not due to heat scorch due to direct sun or a hot window, then could consider the external conditions.

If the area is mainly still air, and if it is humid ----- then fungus can grow on leaves.

A kitchen area might not be as bad as a still-air bathroom though.

Occasional relatively weak application of mag-cal and fertiliser will be beneficial too. Do you use fertiliser and mag-cal?

[rbarata]

Seems bacterial infection. Apply a bactericide (don't know which one) and increase air flow.

[turbosloth10]

Originally Posted by SouthPark

If the issue isn't due to an element deficiency or nutrient deficiency or not due to heat scorch due to direct sun or a hot window, then could consider the external conditions.

If the area is mainly still air, and if it is humid ----- then fungus can grow on leaves.

A kitchen area might not be as had as a still-air bathroom though.

Occasional relatively weak application of mag-cal and fertiliser will be beneficial too. Do you use fertiliser and mag-cal?

I generally fertilize every other week with half strength MSU RO/DI.

I wouldn't call the kitchen air stagnant. We are in and out of the kitchen all day long, and frequently have the ceiling fan on. Were talking 55% humidity in the kitchen when the rest of the house is ~47% with the A/C on. Intermittently higher when cooking or doing dishes. The windows in the kitchen often get opened at night, including the one right above the sink where the plants live. Though I have been thinking about putting this plant and a few others outside for the fall since it is finally starting to cool down here in Sac.

[SouthPark]

TS - also check to see if that kind of orchid drops leaves or if it has a dormancy period.

If it's not time for leaf-drop or dormancy, then I'd go with rbarata's diagnosis - about an infection. Could check to see if copper spray is safe for stanhopea. Otherwise, also consider other treatment such as Monterey garden phos.

Orchids are known to be able to grow indoors. But how well they grow, or how long they last for probably is case-by-case. For some growing areas, the various different changing conditions at various times of the day - air-con, heating, windows open, then later no wind movement for long periods, plus other factors can maybe give an orchid a hard time.

If the brown patches are dry and no spreading, and new growth remains nice ------ then maybe no need for concern, and no need to apply any treatment ---- if dry and no spread.

[estación seca]

It's drying out, not diseased. These are wet growing, high humidity, no direct sun plants. What is it potted in? How are you watering it?