I have a lovely big Bl. Chia Lin "New City" plant that has been blasting its sheaths since September. It put on four new pb's through the summer, and each produced a sheath that did not bloom.
I had it in a spot where I couldn't see the leaves too well, and when I finally hauled it out into the open today, discovered these white deposits, fungus or something on the backs of the leaves. Where the white stuff is on the back of the leaf, the front of the leaf has a yellow spot. The white stuff rubs off easily with my finger. I looked with my magnifying glass and can't see any insects, but they might be under the white fluffy stuff. Doesn' t look like mealybugs, I've had recent experience with them elsewhere in the garden.
Anybody know what this is? Your suggestions on how to treat it would be appreciated.
I can't clearly see the formation of the white fuzz but it looks like you might have both cottony cushion scale and Boisduval scale. You must bomb the plants. They are very aggressive and not only are on the leaves you are seeing but in the potting medium. This is when organic treatments have never worked for me. You can neem 'til your blue. I've tried many organic fixes and have, after months of diligence, always lost the plant. Two rounds of Bayer, three or four weeks apart works. This is to catch any lingering eggs. You will need to treat all plants even vaguely near this one and all in your collection. Scale is the horror story of orchid growers.
I wipe my leaves with weak methelated spirits and spray with a pesticide and white oil spray. Yes it does take more than one treatment as scale are hard to see esp. under old sheaths and in the orchids roots. I repot and spray sometimes cutting off any roots that have alot of scale on them. Ants move the scale from pot to pot and your whole collection can have them in no time.
Bree, to translate in "American", you treat your plants with diluted rubbing alcohol and mineral oil. These are very good organic treatments but they have no residual effect. A lot of the stronger chemical treatments available here are not available in other countries. Maybe a good thing. Still, the advantage (and disadvantage) is that these chemicals have a residual effect and a couple of sprays do the job for a year. A larger problem is the misuse of these products and the resistance the insects develop. Commercial growers switch their chemicals frequently to avoid resistant bugs. If one uses chemical sprays one should do their research, weigh the options and be responsible in their use.
Thank you for pointing out the "over use" of these products, Laurel. I had a pestecide applicator's liscense for 20 years, and had to do continous training seminars every year. The problem for CalTrans was that Round-up was the cure-all for weeds ,and used by everyone. Monsanto has had to change their formulation since then because many weeds had developed an immunity to it. I fear the wide spread use of Imidacloprid is doing the same for insects. I think that even though we probably learned this stuff in highschool biology, we tend to forget that pathogyns, plants, and insects evolve much faster than the chemists can keep up with. Bayer and Monsanto sure aren't going to point this out.
I've said it repeatedly; there is no substitute for good culture. This means taking the time to inspect your orchids frequently and take care of problems quickly. I try to spend some time each day to enjoy my orchids and use that time to check plants. My goal is that each plant is checked for problems once a week. That is what limits my collection number, not space.
I'm now recovering from a bad scale attack and my very first run in with mealies. My own fault for the neglect this past summer while preoccupied with DD's wedding. For most of us things come up in life that get in the way of ideal orchid culture. This is my reason to weigh how many orchids are enough and what I choose to grow. It's a bummer to have to toss Andy's or Ecuagenera orchids because I brought home an infested, $1.00 bargain raffle orchid from a society meeting.