I think you have nailed a very important factor, Carol. Air movement. I don't think I have ever had scale on any of my plants, at least none that I have seen. I have over 500 orchids, from tiny 1" to blooming size. I have three fans in each greenhouse, running from 8 AM until 5 PM (fall/winter) and from 7 AM until 7 PM (spring/summer).
