With brilliant blooms sometimes measuring several inches across, hibiscus secures a place among the showiest flowering shrubs grown in the West. The attractive plant draws hummingbirds and butterflies to the garden. Unfortunately, other, less-welcome visitors are captivated by the hibiscus, too. A number of insect pests do great damage to the shrub, either by chewing or sucking. The American Hibiscus Society has compiled an extensive database to help identify the cause of any damage.
The most important enemy of the hibiscus, these tiny, white insects suck out the plant's juices from the undersides of leaves. After their meal, they secrete a substance called honeydew that can provoke the growth of a sooty, black fungus on the affected leaves. In the wake of a whitefly attack, hibiscus leaves may turn yellow and drop off. To remove whiteflies naturally, suck them up with a vacuum cleaner as you shake the bush. Or, since the pests are attracted to the color yellow, trap them by hanging yellow cards coated with petroleum jelly or another sticky substance around your plants.
Most common in the spring and fall, aphids damage hibiscus by sucking leaves and flower buds. As do whiteflies, they secrete honeydew. Many times the aphids will be accompanied by swarms of ants that "herd" them, so they will release the honeydew secretions that ants crave. Although the ants themselves usually leave the hibiscus alone, you probably do not want them in your garden. A blast from a water hose often wipes out both sets of insects.
Though classified as a chewing insect, the hibiscus beetle (Macoura concolor) is satiny black and tapered at each end to allow it easy entry between the closed folds of a hibiscus flower bud to enjoy the pollen and nectar of the unopened blossom. A female beetle lays her egg in the damaged bud. The bud decays quickly, and the beetle larva hatches, consuming the remains of the bud. Growing only varieties with darker red and orange flowers may discourage the hibiscus beetle, as it shows a preference for the lighter colors of white, yellow and pink.
Among the best weapons against insect pests that prey on hibiscus are friends of the garden, such as ladybugs and toads. The aptly named assassin bug hides amid the plant's dense foliage and attacks insects as they move closer to their target. Frogs, toads and centipedes consume hibiscus beetle larvae, while the ladybug beetle regularly feeds on aphids. Parasitic miniature wasps have been developed that lay their eggs in the body or eggs of hosts, such as aphids and whiteflies. And hybridization continues to improve the hardiness of the species; newer hybrids, such as "Turn of the Century," resist most insect pests.
Your Planting Articles
- The New Sunset Western Garden Book; Kathleen Norris Brenzel
- American Hibiscus Society: Identification of Insects, Pests and Diseases
- National Gardening Association: Those Pest-y Houseplants
- The Garden Primer; Barbara Damrosch
- Learn2Grow: Hibiscus "Turn of the Century"
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