Beallara with chlorotic mottling/leaf patches

[KleioP]

Hi all,

I am relatively new to orchids, and trying to find my way around, especially with identifying pathogens! About 3 weeks ago I first saw weird mottling on a single leaf of a tiny growth on my Beallara Joe's Drum. I unpotted the plant (which was overdue, it was still in the peat mix in which I received it) and found rot in the rhizome. I cut off infected tissue and potted in fresh bark but a few days later the leaves of the bigger rot-free growths started showing the mottling.

I have had this plant 2 months now. It did get intense sun and heat for a couple of days, so I moved it to a different location where only weak sunlight reaches it. The room where it grows has day temps of about 25oC these days, which is I think a few degrees above the recommended maximum.

Can someone tell me if this looks like a virus or something else environmental? Something to do with heat stress or root damage from the repotting? If it is a pathogen, should I worry that other plants might have it (I have to share water unfortunately). Thanks a lot for your help!

[estación seca]

Welcome to the Orchid Board.

I think root damage from repotting, causing trouble taking up water, is most likely. You can't identify virus without a virus test.

I'm not sure the rhizome had rot. That's uncommon with Oncidiums unless temperatures are far too high. 25C by day should be fine. If the rhizome had rot it's unlikely the plant would still be alive.

Repotting to fresh medium is a good idea. The time to do it is when new growth is first forming new roots, when they are only 1-5mm long. Repotting damages old roots. Oncidium roots are thin and easy to damage. If repotted when not forming roots the plant may struggle to absorb water until new roots form.

Fortunately these tend to make new growths multiple times per year, so you should not need to wait long for new roots. Keep it evenly moist. Direct sun may not be good but they grow better with bright light, not deep shade.

[KleioP]

Thank you for your reply! Regarding the rhizome rot, I thought it was obvious at the time (of course now doubting myself). The problem was that the oldest pseudobulb (which had the two tiny growths one on each side) was growing much lower in the substrate compared to the second oldest pseudobulb, which had the 2 big growths. As a consequence, the first pseudobulb and the small growths' rhizomes had been buried deep in what was very dense soily media... the first bulb was black and squishy and same for the rhizomes of its tiny (non viable in my opinion) growths. However, the rhizome section leading to the second oldest bulb and biggest growths was climbing up so was not so deeply buried. I found that upper section to be unaffected.

Luckily I have one new growth now so hopefully there will be roots soon, I put it back with more light now since it is not so hot anymore, to increase the speed of growth. To further promote the new growth, is it making a big difference to cut off the flower spikes? If so I would do that.

And in regards to the spotting being due to root loss, would it not then be expected that the leaves show signs of dehydration as well? In this case only the pseudobulbs are wrinkled but the leaves look completely fine besides the mottling. Thanks again!

[estación seca]

The leaves look dehydrated to me. Rather than smooth and shiny, they are wrinkled, pitted and dull.

Another thought now that I see the photos with higher quality - there may be spider mites. Press a piece of tissue paper along the underside of the leaf, from base to tip. If you see brown or red streaks there are spider mites.

[KleioP]

Makes sense I guess that they would be dehydrated Hoping for the new roots soon!

I just did the spider mite test, all clear.

Although this really is most likely nutritional deficits, in case it would be a virus, how fast would the symptoms develop? Or is there no normal timeline?

[estación seca]

Virus infection is unpredictable. Normal appearing plants can be infected. Spotted plants can be normal.

Nutritional deficiencies causing spots in orchids are usually due to nitrogen, magnesium or calcium.

[KleioP]

That's very helpful, thank you so much for your help!