Dry rot or bacterial spot?

Trouble shoot problems you are having with your cactus.
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Download
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Dry rot or bacterial spot?

Post by Download »

I've previously asked for help ID'ing this cactus (viewtopic.php?t=46903). I suspect Pilosocereus or Espostoa.

Regardless, it has a big problem:

Image

Image

It started off about two winters back as a little brown on some areole. Come summer it didn't spread so I paid it little mind. I then spotted the same brown spots on my Espostoa mirabilis, but it did not spread to any other of my plants. I then purchased a second E mirabilis near the end of summer.

As I had a rust problem last winter on some of my Ferocacti, I preemptively sprayed all of my plants with mancozeb fungicide after moving them under the eves of the house for winter, and reapplied mancozeb every month or so.

During that time I noticed that the little brown spots around the areole had grown very substantially, hence the very large incisions visible in the photo (around this time I noticed that my second E mirabilis also has the same infection). I then moved the plant indoors into my heated and well lit grow cabinet. The plant seemed to heal up fine, but about a month ago I noticed that the brow spots had returned. In particular is a spot near the base, which hasn't encompassed the plant near the base yet, but probably will soon.

I've seen recommendation in some guides that the plant is basically lost and should be discarded, but I am very hesitant to do that with a plant that I can not replace. It's also a bit odd that it only seems to infect this plant and my E mirabilis.

I took the unusual step yesterday of breaking up a 100mg pill of doxycycline (broad spectrum antibiotic), dissolving about 1/10th of it in water and injecting it into the plant, both around the brown spots and into the brown spot (I did that last as not to spread it to clean flesh). If it's bacterial spot, it might work? I figured it was worth trying.

I discovered while injecting that the brown spots are slightly crunchy, something I did not notice while slicing bits off last time. I might try injecting fungicide into it next time, so it gets absorbed better.

Does anyone else have any suggestions? If it gets worse I'll try some more slicing and dicing, but I suspect the base won't support the plant any more if I do that. I will probably cut the top off and graft it as a last resort.
Download
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Re: Dry rot or bacterial spot?

Post by Download »

Bumping as I am still looking for help.
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Steve Johnson
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Re: Dry rot or bacterial spot?

Post by Steve Johnson »

Download wrote: Wed Nov 02, 2022 3:55 am Bumping as I am still looking for help.
Harald (AKA hegar) was our resident fungus and bacteria expert, but he hasn't posted since September 2021, so that must've been right before the forum went down. Unfortunately we lost quite a few members with the 3-month downtime -- and it looks like hegar may have been one of them. You may want to try sending him a PM, and he'll get an email notification -- if he responds to the email, I'm sure he'll rejoin the forum and respond to your PM. Best of luck!
If you just want photos without all the blather, please visit my Flickr gallery.
My location: Los Angeles, CA (Zone 10b)
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jerrytheplater
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Re: Dry rot or bacterial spot?

Post by jerrytheplater »

I sent Hegar a PM soon after we came back online and he still has not responded or even opened it. He has not been online. Anyone know a member of the El Paso Cactus Club? He might be a member there. Maybe you'd get through that way.
Jerry Smith
Bloomingdale, NJ
45 inches (114 cm) rain equivalent per year, approx. evenly spread per month
2012 USDA Hardiness Zone 6b: -5F to OF (-20C to -18C) min.
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Steve Johnson
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Re: Dry rot or bacterial spot?

Post by Steve Johnson »

Download, I'm so sorry that I didn't remember this a lot sooner:

https://www.cactiguide.com/forum/viewto ... 89#p376789

If you're able to get a demethylation inhibitor like tebuconazole or another Triazole, you can apply it as a soil soak. Topical sprays don't do much once a fungal infection gets ahold of cacti, but the systemic action of a soil soak attacks it from the inside out -- this may be your only shot at saving the plant assuming that it's not too far gone. Now here's a bit of good news -- our fall is your spring, so now would be a good time to do a soil soak with a fungicide that fits the description of what you're looking for.
If you just want photos without all the blather, please visit my Flickr gallery.
My location: Los Angeles, CA (Zone 10b)
Download
Posts: 251
Joined: Mon Mar 01, 2021 5:22 am
Location: Adelaide, Australia

Re: Dry rot or bacterial spot?

Post by Download »

Steve Johnson wrote: Wed Nov 02, 2022 6:05 pm Download, I'm so sorry that I did remember this a lot sooner:

https://www.cactiguide.com/forum/viewto ... 89#p376789

If you're able to get a demethylation inhibitor like tebuconazole or another Triazole, you can apply it as a soil soak. Topical sprays don't do much once a fungal infection gets ahold of cacti, but the systemic action of a soil soak attacks it from the inside out -- this may be your only shot at saving the plant assuming that it's not too far gone. Now here's a bit of good news -- our fall is your spring, so now would be a good time to do a soil soak with a fungicide that fits the description of what you're looking for.
I have triforine, which a quick google says is a DMI fungicide. Tebuconazole is available but only through farming supply stores, and I have to buy 20L at once.

Any idea what concentration I should use for a soil soak and for how long? The bottle only specifies spraying on leafy plants to control rust, mildew and black spot (what I purchased it for). Concentration is 20g/L triforine and specifies 14ml/L dilution (0.28 g/L).

Edit: I don't know what they are called elsewhere, but DMIs are called "Group 3" fungicides here. Knowing that now (the labelling system isn't used on small consumer packs of fungicide), I was able to find some other DMI fungicides at more reasonable prices. I'll order some when I run out of triforine.
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Steve Johnson
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Re: Dry rot or bacterial spot?

Post by Steve Johnson »

Download wrote: Thu Nov 03, 2022 6:51 amAny idea what concentration I should use for a soil soak and for how long?
I've never had to do fungicide soil soaks, but this may give us a clue -- the label from Bayer (now BioAdvanced) 3-in-1:

Bayer_3-in-1_active_ingredients.pdf.jpg
Bayer_3-in-1_active_ingredients.pdf.jpg (12.43 KiB) Viewed 1292 times
When I was still using the 3-in-1, my dilution rate was 1 cup per gallon of water. Although I have zero experience with fungal infections, my guess is that A. the percentage of 0.65% Tebuconazole would've been effective given my dilution rate, and B. you'll probably have to soak 2 or 3 times to knock the infection down. (With Imidacloprid, a soil soak once in the spring gives us protection from mealies for the rest of the growing season. I think fungal problems may be a tougher nut to crack.)
If you just want photos without all the blather, please visit my Flickr gallery.
My location: Los Angeles, CA (Zone 10b)
Download
Posts: 251
Joined: Mon Mar 01, 2021 5:22 am
Location: Adelaide, Australia

Re: Dry rot or bacterial spot?

Post by Download »

Steve Johnson wrote: Thu Nov 03, 2022 8:25 am
Download wrote: Thu Nov 03, 2022 6:51 amAny idea what concentration I should use for a soil soak and for how long?
I've never had to do fungicide soil soaks, but this may give us a clue -- the label from Bayer (now BioAdvanced) 3-in-1:


Bayer_3-in-1_active_ingredients.pdf.jpg

When I was still using the 3-in-1, my dilution rate was 1 cup per gallon of water. Although I have zero experience with fungal infections, my guess is that A. the percentage of 0.65% Tebuconazole would've been effective given my dilution rate, and B. you'll probably have to soak 2 or 3 times to knock the infection down. (With Imidacloprid, a soil soak once in the spring gives us protection from mealies for the rest of the growing season. I think fungal problems may be a tougher nut to crack.)
Cheers.
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