Echinopsis yellow spots advice

[Dexter]

Hello, first time posting here...

I have been propagating some echinopsis pachanoi for a few years, and recently the plants are developing yellow spots that eventually become dense patches on the plants.

The new growth from the diseased plants is nice and green, so I assume this is a fungus or similar that is spreading, but I would appreciate any advice on how to identify and manage it please...

I live in the wet tropics of norther Australia, so hot wet and humid summers and hot dry winters. The cacti are grown in 50% perlite 50% cactus mix with added fertilizer.

Thanks in advance!

[MikeInOz]

A few thoughts..
-50/50 perlite/cactus mix is very lean. These are heavy feeders. I would suggest a gravel, loam, organic mix for them with good drainage. They may be growing too slowly.
-The organic part of the potting mix may have broken down too much and hold too much water and not enough air. perlite holds quite a lot of water too.
-It may be too warm for this species. Check if there are others growing in the area in the ground and see how they are doing
-It may be too humid during their rest period.
-They may be getting too much water either during the growing season or dormancy (if they have one) or both.
-It seems to be more a physiological problem rather than an infection from what I can see.
-Check for pests such as scale.
-Check your water supply has enough Ca in it. If not you should add it in the form of gypsum quite regularly. Also make sure your fertilizer is well balanced with a 50/50 N/K ratio and contains all nutrients.

[Steve Johnson]

I agree with what Mike just said, although I'd like to add a few things here...

First - sorry to be "Mr. Picky-Fussy", but the patches are beige, not yellow. Beige is the color of corking, and you have corking all over the place. There's a reason for that which I'll discuss in a moment. Second, take a look at this:

20240506_072842.jpg (174.23 KiB) Viewed 152 times

The beige patches with blackish spots indicated in the circle suggest a fungal infection. You'll find a discussion of this here:

https://www.cactiguide.com/cactipests/#fungus

You have quite a few leafy plants sharing the pot with your cacti. I think most of the nutrients in your fertilizer are going to the leafy plants, not the cacti, and I believe that would explain a lot of the corking. My recommendation -- weed out the leafy plants, and let all the nutrients go to your cacti.

Regarding fertilizer, this may be just the ticket for you:

https://www.amazon.com.au/Searles-Flour ... 01&sr=8-46

The fert's analysis:

Searles.jpg (67.56 KiB) Viewed 152 times

Looks good to me. How about you, Mike? Dexter -- if Mike gives us the thumbs-up, go for it.

[anttisepp]

I'd try first fungicide spray then (better!) if no effect systemic fungicide. This fellow is bullet proof and cannot grow outdoors only in Finland.

[MikeInOz]

Looks good to me. How about you, Mike? Dexter -- if Mike gives us the thumbs-up, go for it.

Looks fine as long as Ca and Mg are coming from somewhere...