Mealybug

Whether in an orchard or your backyard, you may be familiar with damage from mealybugs.

Adult females, soft-bodied, oval and segmented, are covered with a powdery or waxy white covering and are 1/10 to 1/4 inch long. A white cottony sac on the underside of plant leaves in combination with the appearance of ants is a sign that the mealybug has entered your landscape. Females can lay 300-600 eggs within each white sac. (These cottony sacs are sometimes confused with downy mildew). There are three species of them in the genus Pseudococcus; these obscure, and longtailed mealybugs that are common to California.

Mealybug

mealybugs on step

Spotting the Mealybug

Mealybugs are a common pest of apples, pears, grape vines, avocados, and other landscape plants. These pests damage by contaminating clusters with cottony egg sacs, larvae, adults, and honeydew. Often the honeydew becomes covered with a black sooty mold. Egg laying continues for up to two weeks, after which the female dies. Eggs hatch within one to three weeks, producing active, yellow nymphs who immediately begin looking for food. All three species can transmit grape viruses, according to CU IPM. Longtailed mealybug also affects California avocados.

Ants Symbiotic Relationship with Mealybugs

Mealybugs attack all parts of the plant. They pierce and then suck the sap from the plant, excreting a honeydew substance that is sticky and draws ants. This is the basis for a symbiotic relationship between the mealybug and the ants who protect their food source.

Mealybug Control

If the mealybug infestation is light or just beginning, choose organic options for control without spraying harmful chemicals. Prune severely infested branches, dab with alcohol or spray with a Neem oil solution, making sure to treat stems and the underside of leaves. In fact, using Neem as a part of a regular spray program can keep many pests away before they can get a start in your garden. Sometimes, a strong blast of water will disperse the mealybugs.

Natural enemies often control mealybug infestations. Eliminate ants, who protect the mealybug for the honeydew, so that natural predators can work. According to UC IPM, “Mealybug predators include green lacewing (Chrysoperla spp.) larvae, pirate bugs, predaceous fly larvae, and lady beetles, such as the mealybug destroyer (Cryptolaemus montrouzieri). Parasitic wasps are especially important in controlling outbreaks because the wasps specialize on mealybugs and reproduce rapidly. Acerophagus notativentris, Arhopoideus peregrinus, and Anarhopus sydneyensis (family Encyrtidae) parasitize longtailed mealybug”.

A healthy tree or plant is the best defense against mealybug and other pests. Start by planting a healthy, high quality tree or shrub from the trusted professionals at Paradise Nursery. Keep it healthy by following the care instructions we provide. If questions arise, feel free to contact us. Our experienced staff is available to consult, design, install, and manage your landscape and home orchard.

Not Just a California Pest

More than 275 varieties of mealybug exist in the U.S. In warm climates, mealybugs do extensive damage to citrus and ornamental plants, as well as grapes. These pests infect a wide variety of indoor and tropical plants. While they are small and seldom seen, the damage left behind is unmistakable. Left untreated, plants weaken and may die.

Occasionally, the mealybug can overwinter in egg or nymph form and attack again in spring, but more often the pest enters your landscape on new, affected plant material. Secluding pests is the primary reason to keep new plants separate for a few days after you bring them in.

Mealybugs suck phloem sap, the sap that feeds the plants. As the nymphs feed, they foul plants with the honeydew excretion. Large populations often slow plant growth and cause premature leaf or fruit drop and twig dieback. Mealybugs are often confused with wooly aphids.