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Pests in Gardens and Landscapes: Quick Tips

Citrus mealybugs.

Obscure mealybug colony.

Ground mealybug.

Mealybugs are small, soft, wax-covered insects that are common problems on houseplants and on outdoor plants in areas with mild winters. Usually found in groups or colonies, mealybugs suck plant sap and often produce sticky honeydew which can cover leaves and lead to the growth of sooty mold. Manage mealybugs by purchasing pest-free plants, discarding infested plants, and relying on biological control outdoors.

What do mealybugs look like?

• Most adult mealybugs are wingless females with oval, segmented bodies covered with wax. Males have wings but are rarely seen.
• Newly hatched mealybug immatures (nymphs) lack wax and can move around plants but soon settle down and produce a waxy covering.
• They may be confused with cottony cushion scale, woolly aphids, soft scales, and whiteflies, which also produce wax and honeydew.
• Mealybugs are sometimes hard to see because they often live in protected areas of plants such as in the crown of a plant, in branch crotches, or on stems near the soil.

Signs and damage from mealybugs.

• Signs of an infestation might include white, cottony egg masses on plants, wax-covered plants, sticky honeydew, black sooty mold growing on top of honeydew or ants feeding on honeydew.
• Mealybugs suck sap, weakening the plants. High populations can slow plant growth and cause leaf drop.
• Although many plants are attacked, citrus, grapes, bird of paradise, cactus, coral bells, cypress, fuchsia, hibiscus, mimosa, and houseplants are the most commonly infested.

To reduce problems, use a combination of practices.

• Inspect plants thoroughly before bringing them into your home and landscape and discard infested ones.
• If you find mealybugs on a houseplant or in your garden, hand pick or prune them out. If the infestation is serious, remove the whole plant.
• Once you’ve found the pest, continue monitoring plants, pots, and stakes on a regular basis.
• Reduce large, exposed populations by spraying with a strong stream of water, repeating this every few days as needed.
• Outdoors, protect natural enemies mealybugs such as parasitic wasps, predatory insects (e.g. lady beetles and lacewings), and spiders.
• Use nitrogen fertilizer correctly. Over application combined with regular irrigation stimulates new plant growth where mealybugs prefer to lay eggs.
• For serious problems on houseplants, dab with a solution of 70% (or less) isopropyl alcohol and water. Test on a small part of the plant first and monitor for leaf burn (phytotoxicity).

What about pesticides?

• The protective waxy coating of adult mealybugs and their tendency to hide makes contact insecticides less effective. Insecticidal soaps, horticultural oils, and neem oil applied directly to immature mealybugs can reduce numbers.
• Avoid the use of broad-spectrum insecticides which reduce natural enemies that control mealybug populations.  

Minimize the use of pesticides that pollute our waterways. Use nonchemical alternatives or less toxic pesticide products whenever possible. Read product labels carefully and follow instructions on proper use, storage, and disposal.