Spots on Leaves Reason for Concern

[Junebug]

Originally Posted by King_of_orchid_growing:)

All I know is that, according to what I've seen so far in my collection of plants, fungus doesn't cause the white spotty depressions like the ones on one of your plants (pic #1). Fungus spots are usually black or dark brown, so there's a possibility the black spots on the leaves of your plant from pic 2 could be fungal, but I'm not 100% sure.

Bacteria tends to make a plant's tissues turn into mush. From what I've seen of your pics, it doesn't appear anything is all that soft or mushy.

I don't think it's viral because the signs of damage are too erratic. I mean one is a series of white spots, the other is yellowing leaves, and yet others are black spots; they seem like it's all over the place to be caused by a virus.

Some of the pics of a few of your plants honestly look more like they've received damage from sunburn (particularly the plant from pic #3). But then again, from what you've said, I'm not 100% sure anymore.

If it's not sunburn, it could be temperature related, such as the climate being too hot or too cold. This could be true especially after a storm, where the tendency is for it to get too cold.

I have a Vanda subconcolor that received cold damage after a rainstorm during the fall and winter months. The spotting is very similar to the ones on pic #2.

However, here's an example of black spots being caused by being too hot...

I have a Diplocaulobium regale seedling that has one of its leaves develop the same spotting as the black spots on one of your plants (pic #2). That's most likely because my Diplocaulobium regale is a highland plant accustomed to cooler and more intermediate temperatures; however, lately it became blazing hot (over 100 F in the past week), due to forest fires around the surrounding mountains (I live in the valley of the San Gabriel Valley area).

Addressing the problem in pic 3...I've had many Cattleyas and Laelias that showed the same sign of yellowing and reddish brown marks that appear around some black spotting, much like the damage done on one of your plants (pic #3). And I've concluded that they've been from sunburn.

I even currently own a Vanda lilacina that got sunburned because it's one of the shade growing species, and it developed light yellow patches and streaks. It's healing now, but it still retains the damage done. I can show you if you like.

The white spots, I honestly think is also a sign of sunburn. But if you're thinking they're not, then I don't know what they are.

I also highly doubt ants are the culprits behind the damage on the leaves. Ants are more likely to chew on and leave behind visible damage on the flowers than the thick succulent leaves. I've seen ants chew up the flowers on my Isochilus linearis, going as far as to remove the lip of one of the flowers. But no damage was done to the leaves.

As far as snails are concerned, they come in all shapes and sizes. The large garden snails you see are just one species. There are a group of very small snails that are about 3 mm or 4 mm in diameter and they're dark coffee brown in color. I've seen these around orchids pretty often hiding in the root zones. The shells are flatter than the garden snail and resemble miniature ram's horn snails. These are hard to catch because they're small and they move pretty fast (for a snail). I'm not exactly sure what these species of snail eat, what kind of damage they can cause (if any), or if they're beneficial to orchids or us as hobbyists (I have suspicions they're not beneficial).

I want to thank for for spending so much thought and time trying to diagnose my plants.

I checked on them this morning and there was no visible changes except for a lot more ant poop and debris on the lower plant. There's a Schomburgkia hanging just above it and the tiny particles are probably a result of ants tunneling the Schoms. pseudobulbs. Some of this was evidenced in the second photo. It does appear to be just debris. It never moves and can be blown off when the leaves are dry with no evidence of damage remaining. I'm planning to rotate these 2 plants to test my theory.

I'm beginning to wonder if the damage is coming from the sun reflecting off the wall behind the plants. The damage begins behind the leaves instead of on their sun exposed surfaces. There is 2 different shades of paint behind them. The shadier side of the plants are growing in front of the lighter shade of paint.

I'll continue to closely monitor these guys. I have an arsenal of chemical treatments on hand but choose the conservative approach when caring for my plants. The only time I bring out the heavy artillary is if there is a positive diagnosis of an evil threat.