mealy bugs- horticultural oil dunk?

[Roberta]

Mealies are especially resistant to "surface treatment" - their waxy coating will repel water, even with the addition of soap or even oil. Isopropyl alcohol (70%) sprayed on them works quite well - dissolves that coating, but will only get the adults that it hits, won't touch the eggs or larvae (so you have to do it again and again, and the eggs are probably down in the medium or in inaccessible crevices) So use the alcohol while the plant is in bloom, but it's a temporary fix. A systemic gets into the plant, and nails successive generations when they chomp onto it. Use that imidacloprid product (Bayer's Advanced 3-in-1 or equivalent) to have a longer term effect. And hit again in a week or so... once is not enough. Obviously keep it away from food, children and animals while you are spraying. Once dry, it's quite safe in the house since orchids are not on the menu (I hope!)