Question
I noticed you had a question on the white specs on the leaves. I have the same problem and I also live in a sub-tropical region with high humidity however, the white specs are turning my sego palm yellow.  What might this be and what should I use on it to heal my plant.

Answer
Hi Jennifer,

These are most likely Asian (white) scale insects.

Many scale-infested cycads have yellow and brown leaves, and are encrusted with a white substance.

It seems to affect only cycads, particularly favoring cycads of the genus Cycas, which includes the common Cycas revoluta (king sago) and Cycas rumphii (queen sago). If left unchecked, this scale insect can kill a mature Cycas.


Once infestations become severe, the signs are pretty obvious. Catching an infestation before it gets out of hand, however, will take some close inspection. Take a magnifying glass and look carefully at the underside of your plant's leaflets and at the base of the leaves. It's easiest to find the adult females: look for round white dots about 1/16 inch in diameter. The female's body is actually under the white, waxy disk you see. The disk protects the female and gives the insect its name: scale. The males are about the same size and color, but are thread-like in shape. And if you look very closely, you might see tiny yellow specks moving about. These are the newly-hatched scale insects, called crawlers. This is the only stage of a scale insect's life in which it can move to new plants, carried by wind currents. Once the immature insects settle on a plant, they will stay there for the remainder of their lives.

The best control measures are the natural predators of the scale insect.  However, introduction of these beneficial insects will take time. Meanwhile, you will have to rely on chemical warfare.

Your garden center will have insecticidal soaps and horticultural oils that may help control the infestation.  Horticultural oils labeled as summer oils or Volck oil can be used.  Read directions very, very carefully as temperature is a problem, and the dosage may need to be changed depending on the temperature.

Be aware that dead scale insects adhere to the plant and are difficult to distinguish from live insects. To test, scrape them with your fingernail. If they are juicy, they're alive. If they are dry and flake off, they're dead. But even if you have killed the individuals on your cycad, continue to monitor your plant. If you are using sprays, be careful. Add a little dish detergent to your mix to reduce beading on waxy cycad leaves. Make sure to cover all plant surfaces thoroughly.
The typical insecticidal oil is a petroleum product designed to kill insects without harming plants. It works by covering and suffocating the insects, not by poisoning them.

To control aulacaspis scale on a cycad

Remove only dead or completely yellow leaves. Your plant needs all of its green leaves to produce energy for its recovery.

If the white covering of scale insects is very thick, spray the leaves and stems with a jet of water to wash away as much of the covering as possible. Adjust the spray to a level that does not damage the leaves.

After the cycad has dried, read the insecticidal oil label, mix and spray accordingly. Be sure to cover the scale thoroughly, especially on leaf undersides.

Repeat the insecticidal oil spray weekly for four to five weeks. The oil does not kill insect eggs and you must kill new hatchlings.

The dead scale will not fall off plant easily and new scale insects will find your plant again. Check your cycad for live scale by rubbing your finger across the white covering. If you see an orange coloration on your finger, some of the insects are still alive and you should start the spray program again.