Hydnophytum spots

[Mauspad]

Hello everyone, for the past few weeks my approx. 1 year old hydnophytum moseleyanum seedling has been showing leaf spots where the tissue appears to have thinned and collapsed. It has progressed at a moderate rate since I first noticed it. My first thought was thrips, but the spots are not silvery and none of the other plants kept in the same tank (including other hydnophytum seedlings) have been affected.

I live in CT zone 6b. Plants are grown in 100% LFS with just a few pellets of osmocote long release fertilizer and allowed to dry out almost all the way before watering. They are kept in an open top 20 gal aquarium in an east window, temperature in the house is set to be between 62-68 F but I would not be surprised if it dipped lower sometimes at night by the window. Humidity is around 20%. I rubbed the affected leaves with neem when I first noticed the issue but it does not seem to have helped.

I would greatly appreciate any insight. 

Edited January 28, 2019 by Mauspad
Added more detail to cultural conditions

[Frank]

Hi Mauspad,

Welcome to the forum.  I had someone else email photos last week of very similar leaves on Hydnophytums.  You say this is in a tank near a window and this is the only plant affected.  Was this plant in a position that might be colder than the other Hydnos in the tank?  62 is pushing the 60 that is considered the bottom line for safe night temperature, esp if it is long term.  

I would suggest you also examine both sides of the leaves with a very good hand lens or dissecting microscope looking for small mites.  

Winter is tough on Hydnopytums and Squamellaria guppyanum.  They tend to yellow and than loose a lot of leaves.

If your other Hydnos are not affected I would suggest isolating this plant.  Perhaps grow it in a zip lock bag for a while and see what happens.  This stops it from spreading to the other plants if it is insects

Perhaps some other growers here have suggestions or experience?. 

 

[Mauspad]

Thank you Frank for the info and the welcome! Wow, I did not realize I was pushing the low temps that much. Great to know. All 3 in the tank were clustered right next to each other rather close to the glass, but the others (puffii and simplex) are much younger in addition to being different species— not sure how much that is relevant. I don’t have access to a scope but my husband has an opti-visor at work that I will ask to borrow. In the meantime I sprayed it thoroughly with the homemade Castile soap pest solution I use on my succulents and have moved all of them under some grow lights away from the window; at least the temperatures there are stable. In the worst case scenario, I have a warm snake tank that I place cuttings on top of for rooting (the heat lamp does wonders); maybe I could rig something up for the hydnos there.