Yucca Elephantipes - Dark Spots

[Moxie]

I brought a sick Yucca Elephantipes plant home about 2-3 weeks ago - the plant had many dark spots on the leaves. I can see new healthy growth but not sure what to do about the dark spots. Based on my research, these could be related to bacterial leaf spot but I could be wrong and would greatly appreciate your thoughts/treatment suggestions.

Furthermore, it seems to have spread on my other plant in close proximity - Crown of Thorns. Are both plants suffering from the same thing or have separate issues? I have moved them further apart from each other for now. Many thanks in advance.

 

[sorce]

I always cut those ratty leaves off, just cause they bother me. It looks sparse for a while but they seem to appreciate it in the long run.

Sorce

 

[Moxie]

I always cut those ratty leaves off, just cause they bother me. It looks sparse for a while but they seem to appreciate it in the long run.

I thought about it but was a bit concerned with cutting most of the leaves not to have a bald plant :/

 

[Wires_Guy_wires]

I believe they are separate issues.

Yucca can have long lasting mechanical damage, like most desert plants the foliage can stay on for decades. This means every hail stone, dropped pebble, bump from a bird, claw mark or whatever turns into a brown spot and eventually a black one when the tissue dies completely. It doesn't mean the plant is dealing with an infection right now, it doesn't mean it has dealt with an infection in the past.
If the spots occur on new foliage, or they keep expanding on old foliage, then there's reason to worry. If not, then consider them being battle scars of the past. Same goes for the crown of thorns.

 

[Moxie]

I believe they are separate issues.

Yucca can have long lasting mechanical damage, like most desert plants the foliage can stay on for decades. This means every hail stone, dropped pebble, bump from a bird, claw mark or whatever turns into a brown spot and eventually a black one when the tissue dies completely. It doesn't mean the plant is dealing with an infection right now, it doesn't mean it has dealt with an infection in the past.
If the spots occur on new foliage, or they keep expanding on old foliage, then there's reason to worry. If not, then consider them being battle scars of the past. Same goes for the crown of thorns.

Thank you! Unfortunately, I see the dark spots spreading onto new growth I trimmed all suspicious leaves off COT (Crown of Thorns) and gaveYucca a light trim as well. I ordered some anti-pest stuff in the interim and will continue to monitor.

 

[Wires_Guy_wires]

How do the dark spots look in the new growth?
If they turn orange first, then brown, then black, it might just be something with calcium availability (pH of the soil being too high or too low, pretty common in older plants that are commonly kept indoors).

Keep in mind that cutting off foliage that might be infected does two things: it can contaminate your tools and spread to the other plants (use 70% ethanol/alcohol as disinfectant, soak for 15 minutes, adding a little soap or shampoo really helps).
The second thing: Plants respond to infections way differently than we do, so if we remove an infected part entirely, it might not want to fight infections on the other unaffected parts - if you remove one bad tooth from your mouth, it's easier to forget to brush your teeth because they don't hurt as much compared to when the tooth is still there and keeping you awake at night. While plants do have an immune system memory of some sorts, it's sometimes to better to leave damaged parts a little longer.
Cutting stuff off also stops you from seeing if the damage progresses on old foliage, it only gives you a view of the newer parts. Especially nutrient issues can easily be overlooked if we only keep the newest parts
There's a fine balance between cutting something off being the best option, and keeping something on as the best option. I've made the wrong choice on many occasions.

Anti-pest stuff is usually aimed at bugs, insects, mites and such. If you want to fight bacteria, use bactericides. If you want to fight fungi, use fungicides. A bug spray doesn't kill fungi.

Something for us all to remember: no plant dies within a week unless it's cooked or dried out. It's a process that takes months, sometimes years. We humans can take our time for proper diagnosis before we act. And if we can't, then we were already at least a month too late.

 

[hinmo24t]

looks like its outdoors so airflow isnt an issue. no webbing for spider mites.

from the fullsize image it doesnt look like the plant is particularly unhealthy.

could be reason enough to let it do its thing. might be mind over matter for thinking its spreading to other plants.


if these were inside it could be a different ball game

 

[Forsoothe!]

I would treat this with a systemic fungicide like Infuse. This looks like a leafspot typical of grasses.

 

[Moxie]

Quick update: I used Copper Fungicide solution:

• COT (crown of thorns) is 100% fine - no spotty or yellow leaves
• Yucca - all dark spots are still there Furthermore, one leaf started to curl up and almost completely dried out (circled in red). Is there anything else I can try?

ps: trimming Yucca's leaves didn't seem to make a difference - spots are still there. The plant shows strong new growth but there are spots on new leaves as well - light and dark