| You can use neem oil to eliminate the scale, but I would use it a couple of times, a week or two apart. Look for ants. They will bring scale to your plants and farm them. Outdoor growing is tough, as your plants will probably get reinfected from nearby non-orchids. You say a scale mite. Did you mean scale and mites? There is no such thing as a scale mite.
Neem can be used on mites too, but I have read recently that neem doesn't kill the adult mites, although I have had good luck with it when the entire greenhouse is treated. Maybe the adults starve to death not wanting to eat the oil covered plants. Some times you can find neem oil combined with pyrethrins. This will probably do the job. But still I would use the neem a couple of times, a week or two apart. Most insectacides will not kill mites, unless they say so on the label. Also, I have been very disapointed with systemics. The newest ones don't seem to transfer thru the plant, and the older ones no longer work on mites.
Neem oil comes in two forms. One is pure neem, and needs to be mixed with water and a little soap. Not having used this version yet, I can't give any instructions. The other version is called a hydrophylic extract of neem. I have used this according to container instructions, and the wetter/stcker is already in the version I use, as there is no instruction to add any soap. This mixture needs to be agitated often.
ALWAYS, keep the plants out of warm air and under low light conditions for a day or so after spraying the plant very thoroughly. If you are having very warm weather, another product should be used , or the plants brought into an airconditioned house. If weather is cool, you may just be able to cover the plants with extra shade cloth for a day, or spray in the evening. If you do not do the above, the plants can develope a mottled appearence on the leaves, phytotoxicity and phototoxicity. Cynthia  |