Is Your Sago "Palm" Dying? 
Oriental or Aulacaspis cycad scale likely is your problem
by Karl Slatner, Master Gardener

All around south Florida, sago "palms" are suddenly turning completely white and beginning to die. The culprit is a newly (accidentally) introduced (1994) cycad scale insect.

There have been various (changing) recommendations on what to do from authorities such as the University of Florida. Previously, various chemical insecticides typically used on scale insects have been recommended with various combinations and application frequencies. Apparently, those recommendations did not work: sagos kept dying!

The latest (February, 1999) recommendation is to spray a highly refined horticultural oil spray at 10-day intervals and at least four times. Doing so, you will find the scale does not fall off your sago. Your sago will remain white with the dead bodies of the scale insects. The suggestion, therefore, is to use a power spray of water 7-10 days after the 4th (last) oil spraying to help wash away the scale bodies.

At Master Gardener it has been our experience that it is effective to remove the food supply these scales are feeding on -- namely the sago fronds themselves. We have been successful at vanquishing other varieties of cycad scales by cutting off all the fronds as close as possible to the main trunk then allowing new green fronds to grow back in. (Note: If you do this, make sure that you carefully dispose of the infected fronds.) If you use this technique, we further recommend fertilizing your sago 2-3 weeks before frond removal. We would then also use the oil spray applied thoroughly over every visible part of your sago right down to the ground. Expect to wait at least several weeks before new fronds appear.

Another official recommendation for sagos not yet infected by the scale is to use "Garlic Barrier" as an insect repellent. I am not familiar with this product nor do I know where to buy it. Companies that sell organic gardening supplies are said to carry the product.

Update, March 28, 1999

Georgia Tasker reported today in the Miami Herald that sagos are now also "being battered by another, possibly lethal enemy: a fungal infection that enters the interior of the plants through roots weakened by the (scale) insects." The fungus is fusarium. The scale is said to weaken the plants allowing the fusarium to enter. The top fronds of sagos collapse, "seemingly overnight." To combat the fungus, homeowners may use Captan fungicide which is said to be effective.

To fight the scales themselves, the latest suggestion is to use an organic fish and sesame oil product called Organocide. The product is said to work well against the "crawler" stage of the scale's life cycle. Also suggested as effective is using ultra-fine oil, a paraffin product. Use these products as recommended in the first part of this page.

Update, September, 1999 

Organocide is now commonly available in garden centers and at your favorite local nursery. Organocide remains the recommended product. If you have the scale (and almost everyone does), buy the product and apply it ASAP. Don't forget to buy a good sprayer when you're out shopping. 

We have received many emails saying that, after application, sagos remain white (the scale color). People are fearful the spray has not worked. To know if your applications are working, you'll have to touch the white scale areas. The best thing is to run your finger along the bottom rib of an affected frond. If white comes off on your finger, you have removed dead scales. If a yellow or orange color "goo" comes off, you have rubbed live scales. Dead white scales remain on the fronds after they are dead. Only repeated strong water sprayings will remove the white. Also, you can be patient and, over time, new fronds will replace the white appearance.

A major problem is scale re-infection. Even if you kill off all the scales on your sagos, they can come back -- and frequently they do. They come from other infected sagos near your home. The point is, re-check often (say, monthly) with the finger test. If re-infection occurs, re-spray (the whole 4x or 5x cycle) all over again.

Remember, as a sago is weakened by scale infestation, fungus can attack the plant. The fungus may be the actual fatal enemy. It is important to take action ASAP. 

Good luck.

Note: This article was originally published online on the Master Gardener Online website (http://mgonline.com/cycadscale.html)  and is reprinted here with permission.

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