Pest Management Guidelines

Root Mealybugs: Preventing the Serious Pests

CTAHR, Dept. of PEPS, Beaumont Agric. Res. Center, University of Hawaii-Manoa, 461 W. Lanikaula St., Hilo, Hawaii 96720, Phone (808) 935-2885

by Dr. Arnold H. Hara

    Root mealybugs occur only on the roots of their host plants. Because they occur below ground and thus are undetected, root mealybugs can be serious pests.

    Currently the Hawaiian Islands have seven species of root or hypogaeic mealybugs. The most pestiferous species have been the coffee root mealybug, Geococcus coffeae and Rhizoecus hibisci. These root mealybugs infest grasses, palms, citrus, cyperus, pineapple, coffee, mango and syngonium.

    In pots, root mealybugs occur throughout the root mass; however, they are concentrated between the root-ball and the pot. Infestation of root mealybugs is noticeable only if the root-ball is removed from the pot.

Telltale Signs

    Waxy material is the most important sign of root mealybug infestation. Mealybugs secrete lots of white waxy material that cover their bodies.

    Female mealybugs lay eggs or give birth to live young call crawlers. If eggs are laid they usually hatch in less than 24 hours. Crawlers are the dispersal stage and are highly mobile. Once the crawlers find a suitable site, they settle down and begin to feed on roots with their sucking mouth parts. The entire life cycle ranges from two to four months depending on the species. Adults live form 27-57 days, also depending on the species.

Prevention Is Key

Because the root mealybug is very difficult to control, efforts should be made to prevent spread and establishment:

    1. Inspect roots of newly purchased plants by removing the pots.
    2. Avoid root-bound plants, which encourage mealybugs, by re-potting as needed.
    3. Use clean pots and media; if infested, wash with soap and water.
    4. Treat or remove infested plant hosts form your premises.
    5. Do not allow water from infested areas to drain in to clean areas, as crawlers can be transported in water.

Hot Water Dips Kill

    Research conducted by the University of Hawaii College of Tropical Agriculture and Human Resources has demonstrated that hot water dips alone or with insecticides work as insecticides such as Dursban WP and Marathon G. Watering plants prior to drench application will significantly reduce problems with phytotoxicity. Submerging potted Rhapis palms in 120 degrees Fahrenheit (49 degrees Celsius) water until the internal root ball temperature reaches 115 degrees Fahrenheit (46 degrees Celsius) is 100 percent effective in killing root mealybugs and does not significantly affect the potted plants.

    For products good for combating mealybugs, consult the Cooperative Extension Service, Hawaii Department of Agriculture or and reputable agrochemical professional.

Dr. Arnold Hara is a professor in entomology in the Department of Plant and Environmental Protection Sciences at the University of Hawaii Manoa, stationed at Beaumont Agricultural Research Center in Hilo. For more information, call 974-4105, fax 974-4110 or e-mail


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