Description
Mealybugs are soft-bodied insects recognized by the white waxy secretions covering their bodies. They are piercing-sucking insects, closely related to soft scale. Like soft scale they suck plant sap, reducing plant vigor, and can produce abundant honeydew. They are often associated with black sooty mold.
Mealybugs are a challenging pest to control due to their tendency to hide in protected locations, their wide host range, waxy coating and ability to survive for several weeks on greenhouse surfaces without plant material. The citrus mealybug (Planococcus citri) and the longtailed mealybug (Pseudococcus longispinus) are two common species.
Target Crops
Mealybugs prefer tropical and foliage plants, spring annuals, orchids and herbaceous perennials. A few of the susceptible crops are begonia, citrus, coleus, croton, dracaena, hoya, English ivy, ficus, fuchsia, schefflera, hibiscus, mandevilla, jade plants, palms, prayer plants and gardenia.
Life Cycle
Life cycle vary by species, but most adult female mealybugs lay 100-200 eggs in cottony egg sacs over a 10–20-day period. Newly hatched mealybug nymphs (crawlers) are quite mobile and yellow to orange pink and lack wax. As they age into adults, they settle into one spot to feed and excrete a waxy covering. They don’t move very far or very rapidly. Depending on species and environment, mealybugs may have two to six generations a year. All stages may be present throughout the year. Outdoors they may overwinter on or under bark as eggs or as first stage nymphs. Adult males of most species are small, winged insects that do not feed. Their primary role is to fertilize females.
Beneficial Insect Control
Cryptolaemus mountrouzieri, the mealybug destroyer, is a small beetle native to Australia. The larval stage of Crytpolaemus, which resembles a mealybug, is also an active predator. They prefer warm temperatures (over 70°F). It is helpful to release both larvae and adults from April to October for mealybug control. Rates are .5-1/ft² or 5 beetles/plant, or 1,000-5,000/acre.
Anystis baccarum or the Crazee Mite is a generalist predator that will feed on mealybug and their eggs. Anystis prefers moist, warm conditions. Rates are 0.25/ft² for prevention or 1 - 2 mites/ft² for control. Anystis works well when combined with Cryptolaemus.
Chrysoperla rufilabris and Micromus variegatus, the green and brown lacewings respectively, are also generalist predators. For egg release, lightly mist foliage before scattering eggs to help them stick. Always control ants so they don’t interfere with these predators. Rates for green lacewings are 1-5 larvae/ft² on hot spots, 5 eggs/ft² or .25 adults/ft²Rates for brown lacewing adults are 1-3/10ft².
Insecticide Options
Contact insecticides, such as soaps, oils and insect growth regulators, can control mealybug, but is difficult because of the mealybug’s tendency to hide and form dense colonies. Repeated applications are necessary. The following products are labeled for mealybug control.
Velifer is a biological pesticide preferred for its mode of action that provides management on contact of mealybugs. Provide optimum conditions for efficacy.
Pyganic is a broad-spectrum insecticide derived from Chrysanthemums (pyrethrins).
Suffoil-X suffocates and kills soft bodied insects.
Molt-X is a bioinsecticide that contains azadirachtin, an insect growth regulator.
M-Pede insecticidal soap works for soft bodied insects, mites and powdery mildew.
Ecotec Plus targets greenhouse pests with rosemary and peppermint oil as the active ingredients.
Cultural Control Tips
- Inspect incoming plant material and avoid overfeeding plants with high nitrogen fertilizers.
- When scouting, look for white flecks or cottony residues along the leaf midribs, stem axils and underneath leaves.
- Use a forceful jet of high-pressure water to remove mealybugs from their hiding places.
- Since mealybugs can lay their eggs under pots and on greenhouse benches, power wash and sanitize the greenhouse between crops. If feasible, keep the greenhouse empty for two weeks. Do not re-use infested pots.
- Keep greenhouses weed free and destroy heavily infested plants.
- Where tolerated, chilling plants (such as fuchsia, citrus or camellia) for 36 hours or longer at 36°F can kill mealybug. Hot water treatment also does a good job. Be sure plants can tolerate these conditions.
- Remove plant debris from the greenhouse and don’t keep plants long term.
- Avoid the use of broad-spectrum insecticides which will kill both pests and beneficial insects.
Sources
Menacing Mealybugs, Greenhouse Management
Mealybugs in Greenhouses, UMass Extension
Mealybugs Only Seem Invincible, Greenhouse Management
Managing Mealybugs in the Greenhouse, UConn Extension