All hibiscus (Hibiscus spp.), whether hardy varieties that grow in U.S. Department of Agriculture plant hardiness zone 4 through 9, or tropical plants suitable only for USDA zones 9 through 11, face occasional mealybug infestations. The pink hibiscus mealybug poses the greatest hibiscus threat because of its toxic, leaf-curling plant-stunting saliva, but all mealybugs disfigure and weaken the plants. Options for getting rid of the insects vary with the severity of the infestation.
Just a Few
If you're lucky enough to spot mealybugs on your hibiscus before their numbers skyrocket, eliminating them organically is relatively easy.
Dip a cotton swab in the rubbing alcohol, then swab a mealybug with enough alcohol to penetrate its protective wax.
Use the other end of the swab to scrape the mealybug off the hibiscus and into a sealable plastic bag. Repeat for each insect.
A Growing Problem
If you hibiscus has enough mealybugs that swabbing them isn't practical, it's time for organic insecticidal soap spray.
Delay spraying an outdoor hibiscus until the temperature is below 90 degrees Fahrenheit and the plant is out of direct sun. If it's an indoor plant, move it to a dimly lit area.
Protect nearby outdoor plants from potential sun damage by covering them with a lightweight cloth. If you're spraying indoors, cover the surrounding surfaces with newspaper so the soap won't stain them.
Water your hibiscus well before treating it. The soap may damage a water-stressed plant.
Wear protective clothing, including a long-sleeved shirt, long pants, waterproof gloves, safety goggles and a respiratory mask while spraying.
Read and follow all the precautions and application instructions on the soap's label.
Spray the soap until it runs from all the plant's surfaces. Make sure to wet the backs of the leaves and parts of the stems the leaves cover. Repeat the application weekly, or as often as the label suggests, until the infestation subsides.
Too Many to Count
When mealybugs seem to be overwhelming your hibiscus, follow the insecticidal soap treatment with a systemic insecticide, which the plant absorbs through its roots. The plant's sap carries it through the plant's vascular system. After reaching the stems and leaves, it kills the sap-sucking insects.
Put on the chemical-proof gloves and measure the granules according to the label's recommended amount.
Sprinkle the granules evenly around the base of the hibiscus. Spread them in a circle extending from 2 inches from the trunk to the dripline, where rainwater falls from the outermost leaves to the soil. For a potted plant, spread them from 1 inch beyond the trunk to the edge of the container.
Use the cultivating fork to work the granules into the top 1 to 2 inches of soil around an in-ground plant. For a container hibiscus, cover the granules lightly with soil, taking care not to damage the roots.
Water the hibiscus thoroughly right after the application , and then sparingly for the next 10 days so it remains in the soil long enough for the roots to absorb it completely.