Fungus? Or something else?

[cameracassidy]

I have two different cacti, both I believe are Myrtillocactus geometrizans forma cristata. Each has problems but I'm having a hard time diagnosing what's going on.

Cactus 1 has been inside under grow lights in the same pot for about 5 years. It has been watered about once a month and fertilized every other year.

It doesn't look quite like scale. I'm not familiar with other cactus ailments and I'm not finding pictures that look similar.

Photo
https://www.dropbox.com/scl/fi/fpqake8f ... rcq9t&dl=0

Cactus 2 was outside in the Phoenix area for about 5 years in a large pot. I repotted it last fall (August) into a different pot. I had cut arms off it a few months before (May). It's been indoor under grow lights since September. Currently watered about once a month.

The yellowing/browning is radiating from the aeroles. It had some damage from high humidity and over watering a few years ago, but that has since hardened and looks more like corking. But there are some areas that look more like an infection.

Photo
https://www.dropbox.com/scl/fi/j1q3hjrw ... oa3va&dl=0

Photo
https://www.dropbox.com/scl/fi/9g90035u ... m516b&dl=0

I'd love any help or ideas you have on what these issues could be.

[Steve Johnson]

First of all, please see this:

https://www.cactiguide.com/forum/viewtopic.php?t=43819

For good or ill, everything starts out in the roots, so let me know about the mix you're using -- ingredients and proportions of each ingredient. From there I can tell you if the mix is good. If it isn't, that'll be one source of your problems, in which case we need to come up with a better mix for you.

Cactus 1 has been inside under grow lights in the same pot for about 5 years. It has been watered about once a month and fertilized every other year.

Fertilizing every other year isn't nearly enough for cacti being grown under pot cultivation, and your cacti are severely nutrient-starved. You can't use any old fertilizer either, so see this:

https://www.cactiguide.com/forum/viewtopic.php?t=47603

My presentation gives you the basics, although I wrote it when I was still using Dyna-Gro All-Pro 7-7-7 with a potassium sulfate supplement. When Dyna-Gro discontinued the 7-7-7, I went over to General Hydroponics FloraMicro 5-0-1 and FloraBloom 0-5-4 supplemented with an ammonium sulfate-potassium sulfate stock solution. If you'd like to go with that, I'll be happy to give you the instructions and recipes.

This last part is really important -- from hydrobuilder.com (https://hydrobuilder.com/learn/npk-rati ... t-balance/):

• "Magnesium and calcium go hand in hand, and are often an area where plants become deficient. Magnesium helps aid in the uptake and utilization of other nutrients, along with producing carbs and sugars to help during flower."

• "Calcium has a similar role in plants as in humans, helping produce strong cells and root walls. This leads to stronger plants. We've recently come to understand that calcium is actually the dominant nutrient in most plants." [My emphasis]

Believe it or not, the hardness in tap water provides Ca and Mg to our plants, although the water needs to be acidified. The 2 acidifiers safe for home use are 5% white vinegar and citric acid. The reaction products are:

• Calcium acetate and magnesium acetate from vinegar.

• Calcium citrate and magnesium citrate from citric acid.

Acetates and citrates are water-soluble, making Ca and Mg available to the plant's roots. Acidification procedures are a bit complicated, so if you don't want to go that far, water your cacti with rainwater or distilled/RO water. In either case, I highly recommend that you include a nitrogen-free CalMag supplement available from TPS Nutrients here:

https://www.amazon.com/True-Organic-Pla ... 9hdGY&th=1

Dilution is 1/4 teaspoon per gallon, although you may want to double it to 1/2 tsp. if you're not acidifying tap water.

[cameracassidy]

Thank you so much for the detailed reply!

I'm using Bonsai Jack's gritty mix:
https://www.bonsaijack.com/category/pre ... lent-soil/

Based on what you're describing, it sounds like they're mostly in need of fertilizing and this damage likely isn't a fungus or something that needs a pesticide/fungicide treatment?

I am using tap water, which is quite hard, though I haven't checked the pH. I can definitely add in something for the acidity.

I'll grab the options you recommended and add that in the next time I water.

This is really helpful, thank you!

[Steve Johnson]

I'm using Bonsai Jack's gritty mix:
https://www.bonsaijack.com/category/pre ... lent-soil/

Based on what you're describing, it sounds like they're mostly in need of fertilizing and this damage likely isn't a fungus or something that needs a pesticide/fungicide treatment?

I looked at the ingredients, and you made a good choice. In reviewing your photos, I don't see any signs of a fungal infection, but IMO the roots of your cacti are either underdeveloped or nonexistent because they're not getting the nutrients they need on a regular basis. Now I'll mention something called cation exchange capacity (CEC). Soil-based mixes have relatively high CEC, so any nutrients not taken up by the roots stay in the soil when it dries out. Those nutrients will then be released back to the roots with the next watering. For growers using a soil-based mix, I recommend fertilizing with every 3rd or 4th watering. Your mix has low CEC, so I'll recommend fertilizing with every other watering. I use a semi-hydroponic pumice and granite gravel mix with zero CEC, so I have to fertilize every time I water. I should also mention that fertilizing is done in the spring-summer growing season, although this applies to cacti being grown outdoors or in a greenhouse. If you're keeping your cacti indoors with grow lights 365 days a year, they might put on some growth in the fall and winter depending on how warm your growing space is during the day. Be sure that the space provides some airflow around the plants -- stagnant air invites the possibility of fungal infection.

Right now the major concern is the roots or lack thereof. Unpot your cacti, clean the mix out of the roots so you can see what they look like, and post photos so I can see what they look like too. (By the way, it's easier if you post them as file attachments.) From there I can guide you on what to do next. Don't even think about watering until we know what you're up against.

I am using tap water, which is quite hard, though I haven't checked the pH. I can definitely add in something for the acidity.

You'll need to know the pH of your tap water before you determine the right amount of the acidifier you'll use. My preference has always been a digital pen-style meter, but a reliable meter requires calibration. If you don't want to deal with the complication involved, you can also use test strips. The best I've found -- 20 in 1 Hard Water Test Kit made by Oycevila available on Amazon here:

https://www.amazon.com/Oycevila-Complet ... 58&sr=8-36

pH of the water after acidification should be 6.0-6.5, so it's best if you "sneak up" on your target pH by adding a small amount of acidifier at a time. Once you hit the target, write down the total amount of acidifier you used and make a note of it so you'll know how much you need every time you prepare to water your cacti. Something to be aware of -- tap water pH is higher in summer and fall than it is in winter and spring.

If your indoor growing space has a low above 55 at night and a high above the low 70s during the day, this gives you an advantage you won't have if your cacti were outdoors or in a greenhouse during fall and winter. Let me know if you're maintaining those temps around your cacti, and you can get things going sooner rather than later.

This is really helpful, thank you!

My pleasure!

[cameracassidy]

Sorry it took me so long to get back to you. Here are some close up photos of the problem areas of the cactus as well as the roots. I'm noticing an orange-y something on one section. This hasn't been watered for 60 days, but it seems like the roots are ok. There's not as many as I would have expected, but from what I can tell they're still healthy.

I'd love any suggestions you have though.

[Steve Johnson]

The roots actually look better than I expected. However, the Myrtillocactus is severely malnourished, so you'll need to fertilize it (and the rest of your cacti) every time you water -- and understand that the plant's recovery will be a slow process. Once again, you made a good choice with the Bonsai Jack's gritty mix, so repot using that mix. Let the roots settle in for 2-3 weeks, then water and fertilize the plant. Do this every 2 weeks in spring and summer.

Regarding fertilizer, how many cacti are you growing? My fertilizer regimen is kinda sophisticated, so if it's only a handful of plants, this will be easier for you:

https://www.amazon.com/Fertilizer-13-3- ... 136&sr=8-3

Believe it or not, the fert is good for cacti and succulents as well. Dilution is 1/4 heaping teaspoon per gallon of water -- let the granules dissolve completely before you water. You'll also need a nitrogen-free CalMag supplement from TPS Nutrients, available on Amazon here:

https://www.amazon.com/True-Organic-Pla ... 9hdGY&th=1

I normally add 1/4 tsp. per gallon of my watering solution. but since your Myrtillocactus needs to make up for the nutrient deficit, I'll recommend 1/2 tsp. per gallon. While you get the fert and TPS CalMag, be sure to get this:

https://www.amazon.com/Oycevila-Complet ... =8-36&th=1

Once you have everything together, follow these instructions step-by-step:

• Add the fert and CalMag to a gallon of tap water. Cap the container and shake thoroughly.

• Use a test strip and get a reading of the pH. If it's higher than 7.0 (and I'm sure it will be), you'll need to acidify.

• Use 5% white vinegar as the acidifier. Add 1/4 tsp. to the gallon of watering solution, cap the container and shake, then use a new test strip and get a reading of the pH. If it's still 7.0 or higher, add another 1/4 tsp. of vinegar.

The target pH is between 6.0 and 6.5, so keep adding the vinegar in 1/4-tsp. increments as required until you get there. You may have to go through more than a few test strips. These are the colors to aim for:

Color_chart.jpg (34.55 KiB) Viewed 2709 times

If the pH reads in the red, you over-acidified, so toss out the gallon and start over again. Once you determine how many 1/4-tsp. increments it took to reach your target pH, write down the total amount of the vinegar you need per gallon. That way you won't have to go through the testing exercise again.

Not sure what the orange spots are, but they don't appear to be life-threatening. The main thing is to start feeding your cacti -- when they show signs of "greening up", they're on the way to recovery.

[cameracassidy]

Thank you for another thorough response. I was also pleasantly surprised at how the roots looked.

I have probably 5-10 cacti but about 200 succulents total. I've started using a fertilizer recommended/sold by Bonsai Jack: https://www.bonsaijack.com/shop/bonsai- ... izer3-5oz/

It's one of the few slow release I trust as he's always very careful with products he creates and tests all of them thoroughly.

Your approach is definitely more precise and sophisticated than I usually do (reminds me of Jack's approach), but it'll be worth it to get these looking good again.

Given how long it's taken to get to this point, I'm not surprised it will take a while to get back to good health again.

Just to clarify on one point... you said to let the roots settle for 2-3 weeks. So repot it now, but don't water for 2-3 weeks? I typically wait a few days after repotting to give the roots a chance to heal from any little cuts and breaks.

Since these are already so yellow, do you have a suggestion on what to look for in terms of over-watering? I typically wait 3-4 weeks between watering my cacti indoors, even with the well draining soil. Watering every 2 weeks I'm guessing shouldn't be an issue with the fertilizer, but I've never been able to tell if I'm getting close to rot or over watering.

[Steve Johnson]

Thank you for another thorough response. I was also pleasantly surprised at how the roots looked.

My pleasure -- I'm glad to be working with you on this!

I have probably 5-10 cacti but about 200 succulents total. I've started using a fertilizer recommended/sold by Bonsai Jack: https://www.bonsaijack.com/shop/bonsai- ... izer3-5oz/

It's one of the few slow release I trust as he's always very careful with products he creates and tests all of them thoroughly.

Too bad Jack doesn't know as much about this as our horticulturalist-in-residence MikeInOz. I learned a whole lot from him, and at the risk that it might make smoke come out of your ears, dig into the following:

https://www.cactiguide.com/forum/viewtopic.php?t=47603

Now we'll investigate Bonsai Jack's succulent fertilizer:

Total Nitrogen (N) … ……………… 14.00%
6.187% Ammoniacal Nitrogen
5.263% Nitrate Nitrogen
2.550% Urea Nitrogen
Available Phosphate (P2O5) ……… 14.00%
Soluble Potash (K2O) ……………… 14.00%
Molybdenum (Mo)………………..0.0007%

The oxygen in P2O5 and K2O supports the plant's health, but it has no nutrient value, so all we're concerned about is the amount of elemental P and K. The calculations are:

14% P2O5 x 0.436 = 6.1% P
14% K2O x 0.83 = 11.62% K

Using N as a constant of 1, the ideal ratio of N, P, and K should be 1:0.25-0.35:1.1-1.7. 6.1% P/14% N = 0.436 -- too high. 11.62%K/14% N = 0.83 -- too low. Biggest problem is with P much higher than it should be. I should know, because after 9 years of feeding my cacti with P at the same number (0.436), quite a few of them were showing obvious signs of reduced stem growth and reduced flower production. (In fact, a few of my reliable bloomers stopped flowering entirely.) When I changed my fertilizer regimen to bring the P down into acceptable range early last spring, the improvements were substantial. Here are some of the highlights:

https://www.cactiguide.com/forum/viewto ... 52#p401552

No disrespect to Bonsai Jack, but there's not even one slow-release fert on the market that gets it right. 'Such being the case, a water-soluble or liquid concentrate fert is the only way to go. I had to rethink the MSU orchid fertilizer because its P and K are actually too low. This looks more promising:

https://www.amazon.com/Better-Gro-Orchi ... 43&sr=8-10

Now we'll break the 20-14-13 down into a ratio:

14% P2O5 x 0.436 = 6.1% P. 6.1% P/20% N = 0.305 -- much better than the Bonsai Jack's and MSU ferts.
13% K2O x 0.83 = 10.79% K. 10.79% K/20% N = 0.54 -- too low, but guess what? You can add the right amount of potassium sulfate to your watering solution, and that'll bring the K up into an acceptable range. None of the ferts we're discussing have any sulfur, but S will be provided by the potassium sulfate. By the way, S is an important minor nutrient.

Potassium sulfate comes in powder form, and while it is water-soluble, it doesn't dissolve right away. I found that it's better to make a 1-gallon stock solution instead, so let me run some numbers and give you the recipe. Given the fact that you have 5-10 cacti and 200 succulents, how much water are you using per watering session? If you let me know about the volume of your watering container in gallons, I'll run the numbers accordingly.

Just to clarify on one point... you said to let the roots settle for 2-3 weeks. So repot it now, but don't water for 2-3 weeks?

Yes. Cacti undergo a certain amount of "transplant shock", and if you water only a few days after you repot, you'll probably end up with rotted roots.

Since these are already so yellow, do you have a suggestion on what to look for in terms of over-watering? I typically wait 3-4 weeks between watering my cacti indoors, even with the well draining soil. Watering every 2 weeks I'm guessing shouldn't be an issue with the fertilizer, but I've never been able to tell if I'm getting close to rot or over watering.

Some growers are able to weigh their pots by hand and tell if the mix is wet or dry, but I never developed the talent for it, so I had to take a more scientific approach. You can do the same:

• Weigh each pot on a digital scale while the mix is bone-dry. Write down the weight.

• Water the pots deeply, as in water coming out the drain hole. When they stop dripping, weigh them again and write down the wet weight.

• Weigh the pots daily until they go back to their dry weight, and write down the number of days it took going from wet to bone-dry.

If each pot took about 7 or 8 days to get there, water every 2 weeks.

[cameracassidy]

Thank you! This is definitely a lot to dig into, but will definitely be helpful.

[cameracassidy]

Ok, so just diving into this deeper and I think I'm more confused than when we started

I've ordered the fertilizer and calmag you mentioned in a previous comment. When mixed up that should be sufficient, correct?

The orchid fertilizer you mentioned most recently would need a potassium supplement added to it but would create a similar fertilizer to the combo mentioned previously?

I've definitely used the weighing method for determining if my soil is dry. For most of my succulents now though I feel the leaves to see if it's time to water again. Cacti aren't as friendly that way but I generally allow quite a bit of time between watering, maybe too much just to be on the safe side. Easier to revive from under watering than over.

[Steve Johnson]

Ok, so just diving into this deeper and I think I'm more confused than when we started

Yeah, I know -- that was me trying to figure all of this out a few years ago . Trying to explain it ain't easy either, but I'll do my best.

I've ordered the fertilizer and calmag you mentioned in a previous comment. When mixed up that should be sufficient, correct?

Which fertilizer did you order? Was it the MSU Orchid Fertilizer 13-3-15 I originally recommended or the Better-Gro Orchid Plus 20-14-13 I think might be preferable? If it's the 13-3-15, you can supplement it with monopotassium phosphate (MKP) -- the right amount will bring the P and K up to an acceptable range. If you're going with the 20-14-13, all you need is potassium sulfate. You'll get the same result either way, so let me know the fert you selected, and I'll crunch a bunch of numbers for the supplement that'll go with it. Quite honestly, you don't need to wait for the supplement just yet, so dilute as follows according to the fert you selected:

• MSU 13-3-15 -- 1/4 heaping tsp. per gallon.

• Better-Gro 20-14-13 -- 1/8 heaping tsp. per gallon.

1/2 tsp. TPS CalMag per gallon applies regardless of the fert. Not sure if it matters, but I fill my 1-gallon watering jug about 3/4 of the way, add my ferts and stock solutions, fill up to the 1-gallon mark, then add the TPS CalMag last. Cap the jug, shake well, then water away.

I've definitely used the weighing method for determining if my soil is dry. For most of my succulents now though I feel the leaves to see if it's time to water again. Cacti aren't as friendly that way but I generally allow quite a bit of time between watering, maybe too much just to be on the safe side. Easier to revive from under watering than over.

I agree -- when it comes to desert cacti, under-watering beats over-watering, and beginners kill their cacti with kindness by watering them too often. This rule comes from an expert grower who used to be on the forum -- "when in doubt, don't".

[Steve Johnson]

This just in...

I just found a fertilizer that'll simplify the matter:

https://www.amazon.com/Grow-More-5118-T ... 166&sr=8-9

17-8-22, so we'll do a little math:

• 8% P2O5 x .436 = 3.49% P. 3.49%P/17% N = 0.205. Maybe a little bit low, but good enough and your cacti won't be complaining about it.

• 22% K2O x .83 = 18.26% K. 18.26%K/17% N = 1.07. The difference between 1.07 and 1.1 (the lower end of the optimal K range) is negligible -- no need for supplementing with potassium sulfate.

The product appears to be a water-soluble powder, so dilute 1/8 level teaspoon per gallon. Sorry that I made you waste your money on the orchid fert, but at least I'm giving you a much better choice for your cacti.

[cameracassidy]

Awesome! That definitely makes things simpler to just use one things. Would you still add the CalMag as well?

I was looking for something like this but had a hard time finding one. I appreciate all your efforts with this!

[Steve Johnson]

That definitely makes things simpler to just use one things. Would you still add the CalMag as well?

Yes -- add 1/2 tsp. TPS CalMag per gallon of watering solution. This supplements all NPK fertilizers.

I was looking for something like this but had a hard time finding one. I appreciate all your efforts with this!

You're welcome and happy growing!