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.
