Use Organic Horticultural Oil to Kill Asian Cycad Scale

Responsible Insights /
Asian Cycad Scale Appears on King Sago and Queen Sago Palms

The infestation of Asian cycad scale on sago “palms” throughout Florida is causing homeowners and landscapers to search frantically for a way to kill the devastating insects.

Like most pests that have been introduced from the other side of the world, the Asian cycad scale (known by the scientific name Aulacaspis yasumatsui) has no natural predator in the USA to keep its populations in check.

The favorite targets of this tiny but troublesome pest are the king sago (Cycas revoluta) and queen sago (Cycas rumphii) “palms,” two of the most attractive landscape plants in subtropical Florida.

One of the reasons that Asian cycad scale has become such a landscape pest is that it reproduces extremely rapidly. Asian cycad scale can totally cover a 15-foot-tall queen sago in just a few months. Because the scale insect is white, a heavily infested plant looks like it has been dusted with snow.

“Scale insects suck the juices out of the leaves and stems of the plants they infest,” said Tom Broome, president of the Cycad Society. “If left uncontrolled, the pests will eventually kill the plant.” Although Asian cycad scale is not a difficult insect to kill, its rapidly increasing numbers make control an ongoing battle.

How to Control Asian Cycad Scales?

One effective way to control Asian cycad scale is by spraying the infected plants with a light- weight superior horticultural oil. Unlike many other pesticides that kill insects with toxic chemicals, superior horticultural oil literally smothers insect pests to death. The oil spray blocks an insect’s breathing holes (called spiracles), causing it to die from asphyxiation. A superior horticultural oil, such as OMRI® approved Summit® Year-Round® Spray Oil, is an environmentally responsible insecticide that can be used any time during the year.

Experts such as Tom Broome recommend spraying an Asian cycad scale-infested plant every 7-14 days. To effectively control scale, mix Summit® Year-Round® Spray Oil with water according to label instructions and spray the diluted horticultural oil on the infested plant.

121-6 - Year-Round® Spray Oil

It is important to completely cover all surfaces of the plant so that the horticultural oil spray can suffocate as many scale insects as possible. Spray early in the day before temperatures exceed 90° or late in the day when the temperature cools.  For best results, do not apply after rain or when the relative humidity exceeds 90%.

Regular spraying with horticultural oil every 7-14 days will keep the scale insects in check. Even if there are no visible scale insects present on king sago and queen sago plants, spraying the plants with Summit® Year-Round® Spray Oil every month will help to prevent a future infestation. In a strong wind, immature Asian cycad scale insects can actually become airborne and can be blown onto a previously insect-free plant as far as a half-mile away. So even though a sago palm is in an area that has never been infested before, it can become infested after a storm.

Because of its low toxicity, organic Summit® Year-Round® Spray Oil can also be used on all kinds of landscape and garden plants including trees, shrubs and flowers. It poses minimal risk to beneficial insects, has no odor, and can be used on vegetable garden plants and fruit trees right up to the day of harvest.

Unlike other pesticides which can become less effective after repeated use, there is no known build-up of insect resistance to horticultural oil sprays. Ready-to-mix Summit® Year-Round® Spray Oil concentrate is available in three different sizes—one pint, one quart and one gallon. It’s also available in a handy one-quart hose-end spray bottle. Summit® Year-Round® Spray Oil is available at hardware stores, garden centers and online retailers.