Mites? Or?
 

I've had this plant going on two years. It was outside last summer and I noticed silvering on a leaf. Figuring it was spider mites, I treated it. It bloomed like crazy and this year I kept it inside to avoid any chance of mites. Low and behold, last pictures, I see pitting and silvering on a new leaf or two.

I've wiped the leaves and see no streaks. I do see few tiny dark dots, pinprick size, which fall right off the Kleenex used to wipe. I first sprayed it with Bayer 3 in 1 which says it kills spiders, and contains synthetic nicotine (Leisurely just posted about some dendros bring sensitive to this compound). I have been spraying with dish soap, alcohol and water at 5 day (or closer intervals) for about a month. When I wipe the leaves I see a black dot or two and on most leaves, nothing. Today I noticed a couple yellow leaves on the oldest canes.

I wonder if I injured it by spraying? Did it really have mites? Am I perhaps underwatering?

Humidity and temp are both in the mid 60s and I water once a week maybe a little more often. Light is bright indirect. Nothing else seems effected. Thoughts?

First photo is old damage, second one is new.

The "old" photo is pretty typical mite damage, but I don't really see too much in the "new" one.

Didn't show well in the photo. Do you have any other thoughts? No red streaks etc. I do think it looks a little dehydrated and that might account for wrinkly leaves. I'm perplexed as to what to do.

I agree with Ray. Sometimes old damage looks like the tiny pits you see. I agree it might be or have been underwatered.

You have to be extremely careful about spider mites indoors in the winter. In my experience Dendrobiums wintered indoors are extremely susceptible to spider mites. Pay close attention to them.

When I grew cacti under lights for the winter in the Midwest, I sprayed all of them with 70% isopropyl alcohol (rubbing alcohol) every 2 weeks to prevent big infestations. That was not enough to eliminate occasional breakouts, which I treated more intensively, but I never had bad infestations.

I would vote for increasing the watering frequency... as it gets colder outside, the humidity in the house is lower and so watering frequency that worked in the humid summer might be inadequate now. Even in my mild climate, I'm watering the orchids that are in the house (which is where I bring them when they're blooming) about every 3 days because they get quite dry by that time.

I still get very very confused about the different hydration needs of all of these plants. :blushing:

My trick is to water everything pretty much the same. The difference is the media. So I have to make a decision for an individual plant, perhaps every 2-3 years or so... big bark, small bark, sphagnum or mount... research and observation give a guess as to what they need to get the desired effect when they are watered... and I love to water. So the things that need to dry out just get the mounts or big bark, they are dry in a few hours no matter how much I water. But making an evaluation for each plant once every few years is a whole lot easier than having to think about it on a daily basis (which would be quite impossible for the number of plants that have found their way into my house and yard)

You have to watch and understand plants over time to figure out watering. After enough experience, growers can walk into a room, and in less than a second notice, out of the corner of their eye, which plants in the room need water.

Any chance you can visit a greenhouse with a lot of orchids, and chat for several hours with the greenhousekeeper? It could be an orchid business, a botanical garden, a really good grower not to far away.... It would be worth the trouble to go.

I generally follow Roberta's method. I inspect each plant weekly. This is why I'm puzzled. I see silvering but no streaks. I leaves may look slightly wrinkly because I need to step up the water and that may present to my naked eye as silvering. Also there are the two yellowing leaves in the center of the plant.

To add to this, I have dendros I know are clean but came with leaves that look mite damaged. So, I wondered if any other problems present with similar symptoms? This was a difficult problem to accurately present. I am continuing to spray with an alcohol, soap and water mixture. But I may return the plant to it's former place.

The problem with mites is the same with most plant pests. If a few are missed, they will continue to reproduce and, when the population has grown enough, it causes enough damage to be noticed. With many types of treatments, the eggs are not damaged so, with contact treatments, you must spray often and thoroughly. I find it best to wash the plant well with soapy water, let it dry, then treat it with my preferred treatment (currently neem oil). Then I repeat the treatment a few more times, spraying the entire collection.

Some plants tend to be more popular with certain pests. The other plants might host a few of these pests but no real damage is done because the pests keep moving off that plant to the one that they prefer. That is why treating all the plants thoroughly is important, even if you do not see any damage on them.

Good luck!