The Cycad Scourge

We hear a great deal about the latest in human diseases, and recently we have heard a lot more about plant blights. Recently in our area we've heard about Ficus Whitefly, Croton Scale, Red Palm Mite, and the latest Citrus disease du jour which will need to be eradicated statewide. Cycads are one of the great and venerable landscape plants for Florida, and are usually pretty trouble-free, but an exotic scale insect has dampened our efforts to grow them.

We have almost forgotten about Cycad Scale, which largely prevents us from growing many species in the genus Cycas, the Sago group. Cycas revoluta , the King Sago, is among the most susceptible and hardest hit, but the scale has a wide menu of cycad species to infest. Some genera are resistant,though. Many of the species in the genera Encephalartos and Dioon seem resistant to the scale. Once the scale has infested a plant,though, it is difficult to eradicate the bug without some protracted efforts. There are 2 main avenues to pursue in dealing with the scale.

The primary and long term solution is to plant scale-resistant species to avoid spraying an infested plant over and over.One plant I see more and more of in local landscapes is Dioon spinulosum, the Giant Dioon. It is fairly fast growing, can grow in a wide range of sun and soil conditions, and it is easy to locate one at your local nursery. This species is very resistant to the Cycad Scale, and makes a nice open crown of sea-green foliage, spreading into a broad rosette.

If you already have a Cycas species, and it is infested with scale, there is hope for the plant. You must be diligent in keeping the pest problem under control; you won't be able to get rid of it easily. You will "manage" the pest, not try to eradicate it. Monthly spraying with an oil-based insecticide such as Organicide will help a lot in managing Cycad Scale. Several systemic insecticides such as Orthene and Cygon will help in the cause, but monthly, full-coverage spraying seems to work best. Managing a pest by planting resistant species is a better alternative than spraying every month, but sometimes we need to tend to the plants we have. Inspect new landscape plants carefully, and do some advance research before you buy.

Craig Morell
Pinecrest Gardens