Damage on begonia leaves + saw a tiny white bug crawling in soil. More info in comment
By - Lilyofgreensboro
I've had my begonia rex for 2 months now. I've noticed some brown an gray dots on the leaves. The edges have also been crispy. I recently got a pebble tray to try to help with humidity and it's 7 feet off a west-facing window.
I'm worried because it holds onto water unlike any plant I've owned. The pot has a drainage hole and I used a mix of 1 part perlite, 2 parts potting soil, to plant it. But I've only had to water it 3 times (maybe 2) in the past 2 months. It's always slightly moist, especially near the base.
I did notice a tiny white bug in the soil today when checking moisture. I dug around and checked the leaves but didn't find any other bugs but I'm worried now.
Sounds like you need better draining soil. Could probably use more light too. Light drops dramatically mere inches away from the window.
Look up springtails and see if that's the bug you saw. They aren't pests per se, unless their numbers get crazy. The like moist soil and eat decaying organic material.
Recently dealing with this. I overwatered my begonia literally like once and this started happening. I think the moist environment caused my poor plant to be eaten alive by some sort of leaf spot disease. I tried neem and 3-1 pesticide but it all happened at once so all my leaves were infected. I'm noticing the plant almost wilting as well. Crazy cause again this happened within a week. I'm going to spray it with the pesticides again when I water in 3 days but it looks like a goner.
Probably not what you wanted to hear but lol. It's called Xanthomonas. Once it spreads to all the leaves it's pretty much going to die. I swear my stems are turning more black by the minute. Very sad because it was just starting to bloom. It was so healthy and then bam. Very very sad.
Here is mine: https://www.reddit.com/r/plantclinic/comments/nrcqys/spots\_on\_indoor\_tuberous\_begonia/