I have problems with them on my Clivias too. I've had to resort to the toxic stuff for the scale. My lemon and lime trees get several types of scale, and mealies, and the new Citrus Leaf Miner, and the lemon and avocado trees both get mites. Unfortunately, my orchids and Epiphyllums live under the lemon tree in summer, so I have to forgo "organic", and use the Bayer Fruit, Citrus, and Vegetable on the trees. It helps, but the timing is a bit tricky, if you don't want to kill the bees too. I followed Ursula's lead and used the bayer 3in1 on my orchids before I brought them in this year, and I really have only found a few mealies on them.