Mealybugs

Need to know 

• Mealybugs are small oval insects that are covered in wax.  The wax makes them look powdery white. Their wax covered egg masses look like puffs of cotton.
• Mealybugs are a serious pest of houseplants as they use their piercing-sucking mouthparts for feed and produce large amounts of sticky honeydew. 
• Mealybugs can be managed by hand on a small number of plants by dabbing each insect with alcohol-soaked cotton swab
• Insecticides may also be used (including soap or oil-based products), but be sure to check labels to ensure mealybugs and the plant you are treating are listed.

Description of mealybugs

Ornamental houseplants are prone to a wide assortment of insect pests. One of the most common and easy recognize is the mealybug. Mealybugs are oval and

covered in wax which gives them a white powdery look, they often have longer waxy filaments around their bodies, which are about 1/8 to 1/4 inch in size depending on the age of the mealybug.  Mealybug egg masses look like small white puffs of cotton or fluffy deposits of white powder because the female covered the eggs in waxy filaments.

There are many species of mealybugs and each has its own host range.  In Iowa, mealybugs are most commonly a pest of ornamentals kept indoors or in a greenhouse.  Mealybugs are commonly found on succulents, Ficus, Dracaena, ponytail palms, zz plants, poinsettia and many others.

Life cycle of mealybugs

The mealybugs found on houseplants lay eggs in a compact, white waxy sac, usually in the axils where the leaves join stems. Three hundred or more yellowish or orange eggs may be deposited by a single female. The eggs hatch into tiny, immature mealybugs called nymphs that move about on the plant searching for a place to settle and eventually insert their beaks into the plant and begin sucking out the sap. As mealybugs feed numerous waxy filaments start forming as white, threadlike projections located along the edge of the body. The filaments grow, curl and tangle until the entire body is covered. Mealybugs usually remain in one place for their entire life span of four to ten weeks.

Damage caused by mealybugs

Mealybugs are related to aphids and scale insects. Like these, the mealybugs feed on the plant’s sap by extracting it through a long slender beak pierced into the plant tissue. Heavily infested plants are weakened from excessive sap loss and may die. Lightly infested plants may only be stunted, yellowed or malformed. The sweet honeydew excreted by these sap feeders provides a substrate for the distracting black fungus called sooty mold.

Management of mealybugs

Mealybugs may be difficult to control and unless the plant is particularly valuable, it may be best to throw away infested plants before the insects spread to other houseplants.  The standard, well-known remedies for houseplant pests are often successful if applied with diligence and persistence. Picking off individual mealybugs and egg sacs or dabbing each one with an alcohol–soaked cotton swab may be satisfactory for lightly–infested plants [Video].

Insecticide sprays are available for mealybugs and other houseplant pests. Use aerosol or hand pump spray products made just for houseplants. These may contain any of several different ingredients, including insecticidal soaps, pyrethrin, neem, or a synthetic pyrethroid such as permethrin, bifenthrin or resmethrin. Granular insecticides that you add to the soil of infested houseplants may be effective.  Use with caution and read and follow all label directions. 

Biological control is often used to keep mealybug populations at low levels on large houseplants grown in greenhouses and botanical centers. A specific ladybug called the mealybug destroyer is particularly effective. These ladybugs, originally from Australia, are mass-produced by several companies in the U.S. The predators are purchased from the suppliers and released onto infested plants at regular intervals. The ladybug adults and larvae feed on the mealybug eggs and small nymphs. A very tiny wasp that parasitizes mealybugs is also sometimes used to supplement control by the predators. As attractive as this option seems, it is unlikely to be practical for homeowners with a few, relatively small plants or with a limited infestation of mealybugs.