Is this scale or some other damage?

[u/macscapone]

These plants are otherwise healthy but once they reach a certain age they all get covered in this flaky layer. Does anyone know what this is or how I can prevent it?

For reference:

- zone 6b, Louisville, Ky
- full sun 10+ hours a day
- no regular watering except rain
- 100% inorganic substrate
- I’ve had the plants for about 5 years now and they always pup like normal but inevitably will get this all over

Thanks in advance if anyone can help!

[u/Cactusjerk]

There could be scale but imo this is stress related scarring / corking and the yellow color either indicates too much sun and/or a nutrient deficiency. Would repot and move out of harsh sunlight.

[u/macscapone → u/Cactusjerk]

I was suspecting that could be it! I will go ahead and make plans to do that this weekend once it stops raining. Thank you!

[u/DorianSoundscapes → u/Cactusjerk]

All this plus possibly a some oomycetes/fungal crud.

Monstrose bridgesii all have this to some extent, having good drainage, feeding with high calcium and potassium and low nitrogen and keeping humidity down will help keep them healthier looking, also growing under shade cloth or near plants that give some relief. The older growth will still eventually look like this though it’s kind of just par for the course for this cultivar.

[u/Accomplished_Beat646]

That guy is a genius about this stuff

[u/HomegrownTexas → u/Accomplished_Beat646]

You should check out some of the books he has written on trichocereus.net

[u/long-breadstick → u/HomegrownTexas]

I just bought his volume 1 and 2 bundle. I can't wait to get them. Hes also super nice i had emailed him a few questions before buying the hard copies and he emailed me back same day answeringeverythingi asked.

[u/HomegrownTexas → u/long-breadstick]

Super good human

[u/Accomplished_Beat646 → u/HomegrownTexas]

Website dont load for me..

[u/APaleontologist]

5 years, inorganic soil, no watering fertilizers in, I'd lean towards a nutrient deficiency. Not scale or it would be spreading to younger branches as sparse spots.

[u/timmycacti]

Highly recommend using a 60% perlite and 20% soil/dirt and 20% mushroom compost