Doubtful the spots are caused by insects or spiders. Most likely a cultural issue.

Tell us about its culture right now. Where is it sitting? Indoors? Outdoors? Cold? Hot? Sun, shade? watering? Fertilizer? By a sunny window? Near a heating vent? Does it have adequate drainage?, How often are you watering? etc. etc.

Hi Dave!

It is indoors, it gets indirect light, but it's not exactly close to a sunny window... Also, it's been raining nonstop for months here, so I don't remember a sunny day in a long time... Right now it is probably equivalent to shade maybe.

No heating vent... I live in Brazil by the way. It's autumn now but it's not cold, about 23ºC / 73ºF.

I suspected inadequate drainage because I wasn't watering too frequently, maybe once every two weeks (but it's humid here) or when I thought the subtract looked dry. I never fertilized. It was in regular potting mix, with some orchid mix and the pot had some drainage holes.

I stopped watering since I posted this, but last week it was looking even worse, with the brown spots getting bigger... So I repotted. I changed to potting mix + orchid mix + fern mix and added a TON of perlite and changed to a pot with bigger and more drainage holes. It had a little root rot, so I cut off the bad roots. Most of the roots looked ok though! I also put it in my balcony so it gets more light. I checked the unfurled leaf and it was brown inside, so I cut it off.

I wonder if I should cut off the brown leaves. Now there's only a couple that are not affected.

I wouldn't cut off any leaves that still have green on them. They're what are producing food for the plant (through photosynthesis) and also they are drawing water up out of the pot. Without those leaves the soil would stay wet longer. Damage done to the leaves is there to stay, it's only new leaves which will look good, and for those you'll have to wait. taking damaged leaves off now will only weaken the plant.

That makes perfect sense! I'll keep my hands off of it! Thanks tropicbreezent.

On the spider, it kind of depends on your local species. Here in the Northeastern US, a much different climate obviously than yours, there are very few spiders that are harmful to humans or want much to do with humans. When they take up residence in my houseplants, as long as they keep themselves hidden and discrete, I just let them be. I figure they do their part in hunting down spider mites and other unfriendlies that cause problems for houseplants.

We have a few dangerous spiders in Brazil, but I've never seen one. Well, once I think I might have seen a Loxosceles reclusa in my mother-in-law's house, but I'm not sure, it's one of the deadliest in the world. Anyway, this tiny one is harmless to humans I believe. But I was worried it could hurt the plant somehow... I didn't know it killed spider mites! I have a problem with them on a strawberry plant. I'll keep the spider and hope it has a lot of babies (lol).

Andrea, yeah it could be that! I've moved it to a place with better air circulation and more light, and it seems that it helped. Do you know if it spreads between leaves? Some leaves died completely now, and I've removed them. Some are ok, no spots at all, and some seem to have stopped getting worse. I'm anxious because It hasn't put any new leaves for a while, even after I repot it with a better draining soil. But it's fall here, getting colder every day, so I guess it might be dormant right? Anyway, I'll start spraying it with the copper fungicide just in case. Thanks!

Well, I had quite a few of one species of philos that had a lot of spots and, like you, I couldn't remove all the spotted leaves because I wouldn't have any leaves left, so I removed the worst ones and treated the plants, when they grew new, healthy leaves I removed most of the bad ones that were left. I did fertilize with half strength liquid after I treated the plants and that seemed to help too. A few spots did show up here and there later but never as bad as the original situation.

Hopefully mine will be ok like yours, I'll have to wait and see. Fingers crossed! :)

Hi! I hope someone can still help. My monstera has yellow spots and no idea what caused it and how to treat it. Would appreciate any advice. thanks