rot on paphiopedilum leaf

[lobotomizedgoat]

I just noticed this today. I'm not sure what the initial cause was as I'm fairly obsessive about keeping water out from between the leaves. Its last watering was 2 days ago, a mealybug treatment applied to the media as a preventative measure. I've seen no bugs on the plant. Most the area is dry to the tough but there was a single sticky spot underneath the leaf.

I'm not entirely sure what to do here. The last time I had a leaf go like this it was at the bottom of the fan. I basically pulled it off and kept the area dry-ish for a week or two and all was fine. Also disconcerting is that it appears it may have spread to the leaf below it. Any suggestions on how to go about saving this plant?

The plant is growing indoors with supplemental lighting, 65-75° F, 55-70% RH, gentle airflow from nearby ceiling fan, watered every 3-4 days, top layer misted/sprayed in between if it gets dry.

[Ray]

Personally, I'd recommend a couple of good doses of probiotic right away, followed by regular treatments.

Arbico Organics has a great price on Inocucor Garden Solution, and the shipping to you shouldn't be too bad.

However, the color of that plant tells me it is either nitrogen-, or magnesium-deficient, or is getting WAY too much light, or some combination of the above. Tell us about the overall culture it's getting.

[Paphluvr]

Even before reading Ray's post, my first thought was that the plant looked awfully pale. I agree with his assessment but have no recommendation as to treatment.

[rbarata]

Originally Posted by Ray

However, the color of that plant tells me it is either nitrogen-, or magnesium-deficient, or is getting WAY too much light, or some combination of the above. Tell us about the overall culture it's getting.

That was my immediate thought as well.

[estación seca]

I agree with the paleness issue. Paphs with mottled leaves like this are low light plants, doing well with light suitable for Phals, or even less. The big strap-leaf multiflorals do well with higher light, but not these.

[lobotomizedgoat]

It sits next to a NE facing sliding glass door that is in-set, so it gets no direct sun. The top of the plant is ~31 inches from a grow light with given specs of 2700 lumen over a 60° arc and a PPF of 66 μmol/s (at which distance it should be getting ~30μmol/s/m^2, in case that's helpful). The light is on 13.5 hours starting just after sunrise (up from 12.5 hrs in winter).

It usually gets a flush with tap water every 10-14 days and distilled spray in between. I haven't given it a flush since I started mealybug treatments a couple weeks ago, which themselves are mixed with tap. Fertilizer has been roughly once per month with a 20-10-20 diluted to 33 ppm N (urea free). No calcium or magnesium in the fertilizer. If I recall correctly, my tap is ~200-300 TDS, but I don't remember if a more detailed composition was given. I'll update if I can find it.

There's another mottled leaf phal that sits next to it and has also seemed a bit pale to me recently. It's the one that lost a lower leaf to rot back in early November. Though, I feel like the affected area on that one looked browner than this does.

[lobotomizedgoat]

It just occured to me that the original photos may have been a bit overexposed, so for reference here is the plant and its neighbor from above over a white sink.

[Ray]

Whew! Much better.

33 ppm N once per month??? At that concentration, you’d be better applying it twice a week.

[estación seca]

What do you mean by distilled spray? Most people need to water Paphs every few days, not 10-14.

[Dimples]

Southern California municipal water supply should have decent calcium and magnesium levels. Usually around 30-70ppm (+/-) for each depending on what water source they pull from. It would be good to double check your water quality report to be sure.

I don’t grow these, are they especially sensitive to sodium or chloride? It’s not uncommon for water around here to have 50-80ppm (+/-) of both of those.