Q I have a hobby greenhouse in central Florida. My plants are now being infested with scale. Last winter, I was busy at work and the orchids received some frost damage and lack of attention that al lowed the scale to get a good start and I cannot get it under control. I started spraying with malathion (two teaspoons per gallon) and Safer’s Soap every two weeks for four to five weeks. Then someone told me to use Cygon (two teaspoons per gal lon) and Safer’s Soap. I have used it every 10 days on four occasions and I am still seeing the scale under many of the leaves on the cattleyas. Please recommend something else to try. I have about 500 cattleya plants.

A The pesticides and soaps that you are using are suitable for control of scale. The problem is that you need to replace the potting medium, which can harbor eggs and crawlers. Dispose of it in a compost pile or in the garbage. When repotting, closely inspect the plants, and, if necessary, clean away the scale and spray the roots before placing the rootball into new medium. Use caution when clean­ing the roots because of the delicate na­ture of the velamen (this is the spongy, white layer that covers the roots). Some types of soft scales have their body cov­ered with soft wax, which may be dull or glassy, clear or opaque, translucent or netlike. This wax protects them from pes­ticides or soaps. In these instances, you must swab the plants to clean it off. It is also advisable to alternate the use of malathion with oil sprays (Volck Oil or simi­lar). Cygon 2E works well for scale, but this should be applied as a drench, mak­ing sure the plants have been watered re­cently prior to applying the Cygon. Be sure to spray all sides of the leaves for com­plete coverage.