Treatment for Scales on Gardenias

Gardenias are evergreens.

Gardenias are medium-sized shrubs with dark green leaves that are often glossy on top. In early to mid spring, the tips of the branches develop round, white flower blossoms that are highly fragrant. In fact, the gardenia flower oils are used for a variety of perfumes and other scented items. One of the biggest pest problems with gardenias is the scale insect. Treating gardenias infected with scales requires chemical solutions.

Things You'll Need

• Hand-held sprayer
• Narrow range horticultural spray

Instructions

1. Examine the leaves and stems of the gardenia plant closely to identify all areas of scale infestation. The scale insects do not move much, and they look like raised, bumpy areas on the stems that appear brown, gray or slightly reddish in color.

2. Wait until the winter, which is the dormant season for gardenias and the scale insects. You can also treat the scale insects in early summer, if they infest the gardenia then.

3. Open a bottle of narrow-range horticultural oil and pour it into a hand-held spray bottle using the amount specified on the bottle.

4. Spray all stems and leaves of the gardenia plant until no part of the plant is left dry. Pay particular attention to the bottom parts of the leaves, which is where many scale insects live.

Tips & Warnings

• Do not apply the horticultural oil when rain or heavy fog is expected, since it will wash the oil off the plant.

• If desired, you can use the following insecticides to kill the scale insect on the gardenia: carbamate insecticides, organophosphates and pyrethroids.

• Do not purchase products labeled as dormant oil or dormant oil emulsions, since these will damage the gardenia plant.

References

• University of California; Pests in Gardens and Landscapes; S. H. Dreistadt, et al.; March 2007
• Clemson University; Gardenia; Marjan Kluepfel, et al.