Why Are the Leaves Turning White on My Sago Palm?

Identification

• Native to southeast Asia and first identified in the U.S. in 1996, Cycad aulacaspis scale covers a sago palm in such large quantities that the leaves and the entire plant seem to be ensconced in a distinct, white covering. The white substance is a layer of both living and dead scales, often numbering up to 3,000 scales per square inch. The scale lives underground in the root system of the plant and, upon hatching, quickly moves upward to other areas.

Process

• Leaves lower to the ground will typically be the first to be infested by the scale, although the pest will eventually attack every section of the plant. The scale proliferates quickly, although activity will normally slow during the cooler, drier months of the year, with reproductive activity commencing in the spring -- usually in May. It sucks away the sap of the underside of leaves, causing them to turn yellow and be unable to conduct photosynthesis.

Damage

• Eventually, the leaves will turn brown and die, with the growth of new leaf flushes stunted because of the damage. Females are coated with a hard, white, waxy substance that serves as a sort of armor and allows them to feed unmolested and also provides protection for the eggs that the female lays under her body. The eggs hatch in one to two weeks and turn into crawlers -- immature scales that leave the protection of the armor and move elsewhere to feed.

Prevention/Solution

• The crawlers spread easily through the wind and are capable of infesting plants across a wide area. A deadly insect, the Cycad aulacaspis scale can kill the sago palm within one year of infestation. The black lady beetle (Rhyzobius lophanthae) is an effective biological control agent and should be introduced if infestation is rampant. Because the female is protected with its white covering and feeds on the underside of leaves -- a place difficult to reach with sprays -- insecticide application is rarely useful.