Q  I bought a phalaenopsis six month ago. The plant has flowered twice and has adapted to my growing conditions (in an apartment). When I bought the plant, I noticed a black scale on one of the leaves. However, I thought this was a bud or something normal for the plant. Two months ago more of the black scales started to appear and also white ones on the flowers and the stem. I removed 14 of the scales, but the white ones continue to return. Could these be mealybugs? What should I do?

A The problem appears to be scale: black ones are adult and the white ones are immature. The most popular remedy is to swab and daub the plant with a Q-tip or ball of cotton dipped in isopropyl (rubbing) alcohol (70 percent isopropyl). Remove all the scales, large and small. Afterward you will still need to repeat the alcohol treatment to remove the yellowish spots that are recently hatched crawlers. Closely monitor your plants to get an idea of the life cycle of the particular species of scale that is your problem, but expect to repeat treatment against the immature scale every one to two weeks. An alternative to swabbing and daubing is to apply the alcohol as a spray with a misting bottle or small pump sprayer. One recipe for a 11/2 quart spray bottle is to mix a 50:50 solution of isopropyl and water, with a few drops to about one teaspoon of liquid soap to act as a spreader. If the infection is heavy, then you may need to consider replacing the potting medium, which can harbor eggs and crawlers. Rubbing alcohol can be used on hard-leaved orchids. However, it may cause injury or death to small and thin-leaved orchids.