Oncidium Leaf Issues - Mites? Other? Help!

[Welfkoondo]

Hello:

I'm a pretty experienced grower but fairly new to Oncidium Intergenerics. I became enchanted with them several years ago and acquired several dozen. Gnerally they have grown well and many have flowered. About a year ago, several started showing yellow spots, sometimes streaks. I did extensive testing with Agdia strips and they were negative (some were positive but not the ones showing these symptoms). I tried several fungicides, also with no results.

I also tried testing for spider mites using the "tissue paper technique" and visual observation with magnifiers. Again it came up negative. Yes, I did have spider mites during the summer, especially on my Cattleyas, but I'm pretty sure I took care of them and they aren't the cause of this. I also noticed that where the spots were, there were typically tiny white specks. I've tried looking at them with magnification, but can't see much. I'm wondering if they could be flat mites or phalaenopsis mites or some tiny specie of mealybugs.

Any and all help appreciated!
Welfkoondo

[JDT]

I have no clue on the spotting on those leaves, hopefully someone will know. The pot marks on the second photo I have seen on some of my Cattleya but since I treated I have not seen them get any worse.

[78Terp]

I began treating my orchids for bugs of some variety with 'acephate' based bug spray. It helped dry up those spots and my infected orchids that had trouble blooming are now able to get the blooms open and to hold them for more than 1 day.

I had originally thought and hoped it was only damage from watering at the wrong time of day. It wasn't.

---------- Post Merged at 12:54 PM ----------

Also be aware that an orchid leave will never heal. Once the damage is present it will remain.

Look to new growth for evidence that you were able to cure the issue. The new growth will not exhibit the problems.

[sciencegal]

Acephate is pretty wicked stuff. Use with caution. I've resorted to using an imidacloprid systemic for a whitefly and mealy bug problem. It's much safer but won't affect mites.

[Welfkoondo]

Thanks 78Terp:
Did your leaves look similar to mine before the Acephate?
Welfkoondo

[Chris in Hamilton]

Welcome to the forum! Where is your growing area?

[ksriramkumar]

2nd one with pitting mark looks like a cold damage to me. Coming to the streaking and spotting of yellow

1. Is it there in all the mature leaves and the newly growing leaves?
2. Is there a visible impact of the spotting, lesser vigor?/lesser flower count/ deformed flowers?

[Dorsetman]

The white spots look to me like areas of the leaf where the cellcontents have been sucked out by some kind of sap sucking insect. Presumably not one of the scale insects, or the old cases of the dead ones would remain after the new nymphs had moved away. One of the thrips I suspect. There are thousands of different species - with different characteristics. Beware "experts" who can tell you how to kill thrips without knowing which one you have ! . If it is thrips, they can be extraordinarily difficult to find and tokill, because they have several stages, often each lasting only hours or days, and in some of the stages -I rhink the correct term is instars - the creature spends tme in the compost doing some kind of metamorphosis from the crawling larva to the brief flying, mating ( although some don't mate, just go straight on ) egg laying, and so on.
To check, try holding the leaf up to the light. The praence of evacuated cells from this kind of action is much more clearly seen then.
If it is thrips or aomething else spending time in the compost, they are sfe from sprays at that time, and a soil drench is the answer , there are various things sold for vine weevil protection - in UK there is a Provade and a Bug Clear, both of which are made in vine weevil versions requiring different dilutions to the standard stuff, but often thse things are sold under different names in different countries.
In UK we had problems with a black thrips - i never saw one, but suffered damage to cymbidium leaves and to my oncidium/odontoglossum collection. It was only when I saw it on cymbidiums, where the symptoms were slightly different, due to the laves being different, that I recognised it. But a combination of spraying, glue traps and soil drenches cleared it in a season - but beware - some plants went on to produce very small flowers the next season, although are now growing out of this, and are back to normal.

[JDT]

Geoff, thanks for the education!!

[Welfkoondo]

North Carolina. I have both a small greenhouse and a fairly substantial array of artificial lights in my basement. Generally, it seems like most of these issues have been in the basement as opposed to the greenhouse....

---------- Post Merged at 09:22 PM ----------

Sounds like an interesting possibility - what sorts of insecticides are effective on thrips, please?