Need a little help please

[Cheddarbob14]

Having an issue with my Oncidium Hilo Firecracker. Plant is doing really well right now but I just noticed a couple dark spots on top side of 1 of the leaves, then realized the bottom side looks almost like a rash. There are maybe a total of 4 other leaves that have similar "stuff" on it, but nowhere near the degree that the 1 pictured has. Any idea what it is? What to do to fix it? I've been fortunate to have not had any issues like this yet, which leaves me clueless on the current situation though!

[rbarata]

Just to put things in context so that it can be educational to those like me that can't help you... How do you grow it (temp, HR, etc).

[Cheddarbob14]

Indoors, east facing bay window, changed to full water culture 4/10 of this year. House is usually between 68-70 degrees (around 21C), whole house humidifier is around 40%. Plant seems to be very happy other than the leaf issue. I've seen the sticky stuff produced before, but never "sweating" out of a newer growth like this....


Edit-about 20% of the roots are always in water, once a week, I completely soak all of the roots for 30 minutes with k-lite fertilizer at 25ppm N, Kelpmax, and Inocucor.

[rbarata]

I see a wrinkled leaf, even if it's only slighlt wrinkled.
My oncidiums and related all seat like that. I always atribbuted it to evapotranspiration, which is normal, I think.
And what about fertilizer?

[AnonYMouse]

Take a alcohol soaked cotton ball and swipe along the underside of the leaf. If you get an orange smear, you have mites. If not, you have some other sucking pest. Examine under a magnifying glass.

Treat according to your level of comfort. A vigorous shower will remove some, alcohol will remove more and reduce microbial actions, blast with the big guns (systemics).

[Cheddarbob14]

Using the cotton ball trick it did come up with an orange tinge. After a little research, which included a handful of other threads here, I am ordering azamax to do battle with. Orchid is in a room seldomly used, no where near any other orchids. Contemplating treating all of my other orchids (about 20) for preventative maintenance. No signs currently on any of the others, just a bit nervous, especially with 2 new cattleyas arriving Wednesday from SVO ! Any suggestions for a general monthly preventative maintenance pest treatment? A little less harsh than the "agent orange" I'm about to deploy?

[rbarata]

Mites develop in low HR.

[Dollythehun]

I bought an all natural product, called Mite X. I might use it as a preventative for awhile. For sure there will be more than one battle. You see them more as temps rise and humidity drops.

[bil]

My immediate thought was spider mite.

Hit it hard with a good acaricide, and don't mess about. They can do real damage.

[estación seca]

Certain plants are highly susceptible to spider mites when humidity is too low for them. Many Oncidiums with thin leaves are in this group. Other orchids are Catasetums and relatives, Cymbidiums, thin-leafed Dendrobiums, Phalaenopsis. Other plants often attacked by spider mites are Brugmansia, some cacti, jasmine, peppers and some Yuccas.

Focus on raising humidity in that room. If you can get it to the 60%-70% range you will have much less spider mite trouble.

Mites can be controlled, and the current infestation sometimes eliminated, by spraying both leaf surfaces of all plants with insecticidal soap or a 70%-90% alcohol solution (sold as rubbing alcohol in the US.) These don't kill mite eggs, so you have to spray every 2-3 days for 4-5 treatments. This kills the mites as they hatch.

Regular spraying with plain water will also eliminate them. They cannot climb back onto the plants. After all eggs hatch, and they have all been knocked off, the plant will be mite-free until reinfested.

Mites have a very short generation time, so they develop resistance to pesticides rapidly. If you use pesticides you need to rotate them often.

They are naturalized outdoors here in metro Phoenix, so I don't ever use pesticides to kill them. They can't be eliminated here. I pay close attention. Susceptible plants I spray with water weekly. At the first sign of mites I use alcohol on every susceptible plant in my collection.