White Stuff on Sago Palms

Many people have asked us recently about the "white stuff" on their Sago Palms. They say it looks like snow on the plant. It is most easily seen on the bottom of the fronds especially those closest to the ground. This is the cycad or aulacaspis scale(Aulacaspis yasumatsui). It is a very small insect, not a fungus as some people think. It is a relatively new pest of Sago palms in central Florida. It was accidentally brought into this country into Miami in the middle of the 1990's and has spread north to us ever since. The Sago Palm is really misnamed. It is not a palm at all but a type of plant called a cycad. It just looks like a palm. The insect is very specific to this and a small number of other cycads and will not spread to palms or other plants.

The little insect is not hard to kill, but if you see it there are a lot of them. At this time you can control the scale, but it is very difficult to eliminate it completely and permanently. There are two reasons for this. The first is that the scale gets on the trunk of the plant, the roots, and into the ground. It is hard to kill when it does this. The second reason is that your neighbors also probably have the scale and it will be blown back to your plant from theirs.

If not controlled, this little insect will kill your plant.

The scale normally infests the lower side of fronds at first and then moves to the upper surface. They also infest the stem and roots down a foot or more into the soil.

The following is currently the best method of control:

Prune off all totally infested fronds and seal them in plastic bags for disposal. You may want to prune off more fronds to get the plant to "look good" to your satisfaction. This pruning will not hurt the plant as it will grow new fronds.

Next buy some horticultural oil. A paraffin-based ultra-fine horticultural oil, or Organocide, which is 95% fish oil, is best. One or more of these products or similar ones is available at almost any garden shop or store. The label may not give directions for use on the sago palm, but the amount of oil per gallon has a fairly wide range. A couple to three tablespoons per gallon of water should do. What you want to do is coat the frond and the insect with the oil. The oil covers the insect and prevents it from breathing and thus kills it. Make sure to get the underside of the fronds and trunk. You may add a tablespoon of insecticidal soap if you want (also available at most garden shops or stores). The soap will act with the oil to help kill the insect.

You will need to spray the plant weekly for 5 weeks, to kill all of the scale and those that migrate from the trunk, the roots and the ground. Before you spray with the oil you should spray the fronds with the hose set at a very hard spray to wash off any oil build-up and dead scale.

If or when the scale returns, repeat the above procedure. If done correctly it will control the insect and keep your plant healthy.

Recently there have been some experiments done on killing the scale on the roots of the plant. The experiment was done using a 2% solution of the oil (this is a little more than 2.5 tablespoons of oil per gallon of water). 100% of the female scale were killed in the experiments. Enough of the oil and water mixture needs to be used to soak the ground around the Sago Palm to a depth of 1 foot. These experiments were done under controlled experimental conditions and no one yet knows if it will work well for the homeowner. You can try it at home, but we do not know how well it will work.

There is some hope for a less time consuming control of the scale in the future. There are some biological control agents currently being tested. One is a beetle that preys on the scale and the other is a parasitic wasp. Hopefully these tests will prove safe and successful and we will get better control of this pest in the future.

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