Mealybug Infestation

Question

I have been fighting an ongoing mealybug infestation in myPhalaenopsiscollection for more than two years. Using insecticides has caused me more problems than it cured. Lately, I have been using Ultrafine Sun Oil pesticide, but if I stop for a week, the bugs come right back. I have been told that systemic pesticides do not work on orchids. Is this true? Can you recommend a safe and effective pesticide for my problem? —Steven Schneider 

The best time to control mealybugs is when there are just a few. They multiply rapidly and control becomes difficult- photo © 1998 Greg Allikas

Answer

I have never found systemic insecticides particularly effective against mealybugs. However, Orthene does seem to be good for treatment when used at the strength recommended on the label. Because mealybugs are such a problem with fast-growing, soft-leaved orchids like Phalaenopsis, it is important to bring them under control, and then treat as necessary to keep an infestation from reestablishing. The classic prescription is to treat every seven to 10 days for three treatments, alternating insecticides. For example, you might choose to use Orthene and Malathion. The use of a wetting agent is also important with mealybugs to penetrate their waxy coatings. —Ned Nash