Management

The Pink Hibiscus Mealybug (PHM) is a pest that has devastated agriculture in many parts of the world. If left uncontrolled, it will kill plants and even trees. Our management options include the use of chemical and biological controls. 

• Biological Controls

  Biological control offers the safest, most economical and long term solution to this problem. This strategy relies on producing sufficient numbers of tiny wasps (parasitoids) that attack and kill the PHM. These wasps lay their eggs inside individual mealybugs. When the eggs hatch the immature stage of the "parasitoid" feeds on the mealybug from the inside. After 2-3 weeks, an adult wasp will emerge, find a mate and then start to lay her eggs in many more mealybugs.  These wasps do not attack plants, other animals or people. In fact, they don't even attack other mealybugs. They are so small most people will never see them. The problem with this system is that it takes time for the natural enemies to build up sufficient numbers to reduce the mealybug population to a tolerable level. USDA-APHIS and the Florida Department of Agriculture, Division of Plant Industry (DPI) have a limited supply of parasitoids to release. In order to prevent significant losses of plant material and allow for more efficient establishment of the natural enemies, we feel that the homeowner could use a couple tactics. 

• Pesticides

  Most pesticides sold in retail garden centers will kill any natural enemies that come in contact with the treated plants. This effect can last for months. The mealybugs are much less sensitive and will begin to build up damaging populations soon after application. Homeowners must choose the correct pesticide or they will make their mealybug problem worse.

  If they choose one of the insecticidal soaps or oils available through their local garden center, they should apply it once prior to the release of natural enemies. Care should be taken to apply the soap or oil or combination of soap and oil to only one plant and observe the plant for damage. Damage will be noticeable within 2 to 3 days. Another pesticide option is available to the homeowner -- Bayer Advanced Tree & Shrub Insecticide. The active ingredient is used to manage mealybugs in nurseries. This material should be mixed and applied exactly as described on the label: to the soil.

  Do not treat all of your infested plants! At least one infested plant should be untreated so that wasps can be released on it. The wasps will establish on this plant which will then serve as a source for control agents that will search your property for other mealybugs.

  For effective management, destroy as much infested material as possible and drench remaining plants with systemic insecticides like thiamethoxam, dinotefuran, or imidacloprid. Soil drenches have proven more effective than foliar sprays. Recent studies at MREC demonstrated successful control of mealybugs on hibiscus using soil drenches.

  Follow up with a spray application of Orthene and a synthetic pyrethroid to target non-feeding mealybugs. While tank mixes are generally not advised, some combinations, like bifenthrin and acephate, have shown increased control efficacy. Always conduct phytotoxicity tests before application.

• Scouting

  Scouting is absolutely essential in the management of mealybugs. When scouting for this pest, it is advisable to also check the root systems. There are reports that PHM will also feed on parts of the plant below the soil line. Although the toxin of PHM can result in much more damage than most mealybug pests, it does aid in finding low or incipient populations whereas other species may not be detected until very dense populations have developed. It is wise to quarantine newly acquired plants and, if careful examination shows living mealybugs are present, apply effective insecticides until the infestation is eliminated.

  Treatments should also be made to the area in which the infested plants were maintained. The crawler stage of mealybugs is the most fragile stage and the most susceptible to chemical control. Under the best of circumstances, chemical control is difficult because the waxy covering protects the mealybugs and eggs from chemical exposure. Sprays should be repeated at two to three week intervals. Persistence in treatment and careful observation of results will be required to bring success. Continue to check for living insects on the foliage, stems, and on the pots and bench. Adult female mealybugs will crawl off plants and can be found on bricks, under benches and ground covers where they lay eggs.

• Disposal of Infected Material

  Another option would be to physically remove most of the infested plant material. Disposal for infested plant material should follow USDA-APHIS and DPI guidelines! Natural enemies will then be released into the remaining population and serve as a source for control agents that will search your property for other mealybugs.