brown holes on mother-in-law's tongue (snake plant)
My snake plant developed small round -- oval shaped brown holes at some point this past summer. I saw no signs of spider mites or any type of fungus. I wiped the leaves down with alcohol in October and some brown spots still appeared. I should add that this plant has been growing in a vase with marbles for at least 20 years. I rarely feed it. It gets early morning to mid afternoon sunlight. The holes are very small, most of them about 1-2 cm. -- maybe less. Last week I took the plant out of the water, rinsed out the vase and marbles. The plant had some white fuzz on one group of roots which I was able to wipe off with a damp paper towel. I don't see any new brown holes and it appears some new sprouts might be forming. I would like to know what caused this problem, so I can avoid it happening again. I couldn't find anything on the internet that addressed having small brown holes.
We do not see disease or insect evidence. Therefore, the problem is environmental. Snake plants can be susceptible to bruising. It's possible is was handled too roughly or encountered something. At any rate, you can cut out the affected stems if you like.
Snake plants also prefer bright light, even direct sunlight.
Though they grow slowly, they do need nutrients. It may be time to feed this one. Standard liquid fertilizer can be applied, but half strength and only once a month during the active growing period.
You said it could be enviromental. Like what? The enviroment has been the same for 20 years.
As for being handled or bruised, the plant has never been touched. It sits on a book shelf as it has been for the last 20 years. If youu looked at the picture, you can see I CAN'T cut out the affected leaves, since that would be all of them.
You said feed it during the active growing period. What would that be?
"Environmental" damage is kind of a catch-all for things that can not be blamed on insect pest or disease. It could be things like temperature swings, too much/too little sun, water etc. It's actually good news because it is much easier to deal with than bugs or diseases. We can't say exactly what caused the spots, but just the fact that you have had the plant that long and it is otherwise thriving is great. Individual leaves don't live forever.
The leaves that can be removed or cut off are just the ones that show the biggest oval damage that bothers you. You don't have to remove anything else. You could even cut just below the lowest oval. Or just leave it, it's up to you.
As far as feeding, they don't need much. Spring/summer is the usual growth period. We'd suggest giving a standard liquid fertilizer once a month at half-strength from about May - September.