Hibiscus Plant Care

Mealybugs

There are small, bright white spots all over my hibiscus!

Mealybugs Look Like Spots of White Cotton

Mealybugs are not a common pest on hibiscus the way aphids are; however, from time to time these pests may show up on your hibiscus. If not controlled, they can rapidly spread to all your hibiscus (and other plants) where they suck juices and create a real mess as they excrete excess plant sugars onto the leaves. This "honeydew" is food for black mold which grows in it and discolors the leaves. Defoliation (loss of leaves) of the entire plant is often the result of all this stress.

What do Mealybugs Look Like?

You are most likely to notice mealybugs when they reach the adult stage and begin to cover themselves with a white, waxy, protective material that looks somewhat like cotton balls. This bright white color stands out against the green of the leaves. One difference that distinguishes mealybugs from other pests, such as snow scale, is that mealybugs can be found on both tops and bottoms of leaves, on flower buds, on the stem that holds the buds (the peduncle), or anywhere else on the plant. Once they cover themselves with the cottony mass they rarely move, continuing to feed on the plant in the same place. Mealybug young are called runners, and are more difficult to see. These are the bugs that spread from plant to plant. They are good climbers and can climb down to the ground and back up another plant. This is the stage of growth that is susceptible to chemical pest control sprays, but it is nearly impossible to spot mealybugs at this stage. Mealybug females lay egg masses on the plants or even on the sides of pots. These egg masses resemble the adults in that they are covered with the same waxy, white, protective material.

What do I do if I See Mealybugs?

Every White Spot is a Mealybug or Egg Mass

Once you spot mealybugs on your hibiscus or other plants, do not expect them to just go away. They probably won't, although predatory insects will help control them in an outside garden. More than likely the mealybugs will spread to all of your garden plants unless you intervene. They can live and reproduce on weeds, which makes removing weeds near your hibiscus very important. The reason mealybugs are such a formidable pest is that the white waxy material they cover themselves and their eggs with is like an armor that protects them from normal pesticide sprays. When they are young they are not covered with the white waxy "cotton" and can be killed with sprays, which is helpful. But the protected adult females will continue to lay and protect eggs more rapidly than you can kill the young runners with pesticides. The result is that no matter how much you spray, your mealybug population will continue to spread out of control.

To eliminate a mealybug invasion, you need a 2-pronged response: a systemic pesticide and physical cleaning of the plant, since even a systemic pesticide works more slowly than mealybugs reproduce in many cases. An optional 3rd prong is adding beneficial insects to your garden at the end of the process to make sure any new mealybugs that may still survive are dispatched of quickly.

 

Step 1 ~ A Systemic Pesticide:

Start with a systemic pesticide - one that is absorbed through the roots of the hibiscus and remains present in the plant sap. When the mealybugs consume the sap they are eventually poisoned. Imidicloprid is the active ingredient that works best. It is found in Bayer Rose & Flower available from us or from your favorite garden center. Using the heaviest of the recommended doses on the label for your plant or pot size, sprinkle the product onto the soil at the base of the plant, then water it just enough to dissolve the granules. Don't water again until the potting soil or ground is fairly dry (but well before the plants wilt). Mealybugs are harder to kill this way than aphids or whiteflies, but eventually they will either leave the treated plants or die. You may have to make a second application if the first one does not make a significant difference within 3-4 weeks after applying it.

 

Step 2 ~ Physically Clean the Plant:

Mealybugs Lay Eggs on Sides and Under Rims of Pots

Once you have applied the systemic pesticide, you should physically clean away the existing, adult mealybugs. Since they don't move and are easy to see, they are easy to remove. If you have only one or two infected plants, use Q-tips and rubbing alcohol. Just dip a Q-tip in the alcohol, then touch the mealybug with the alcohol. It will start to eat through the waxy armor and kill the mealybug. Use the Q-tip to wipe the mealybug off the plant completely, and deposit it into a plastic bag. It's a slow process, but if you remove each adult mealybug and each egg deposit this way, along with the application of Bayer Rose & Flower to kill any new mealybugs, you can control your infestation very quickly. You will need to check your plant over very thoroughly several times a week for a while and use Q-tips and alcohol to remove any new mealybug adults that appear.

If you have lots of hibiscus plants, the Q-tips and alcohol method is just not practical. For a large infestation on many plants, a new cleaning product called Limonene, if used in the right dosage, can be sprayed on large numbers of plants, and it will melt away the mealybug's waxy coating, as well as the sugary honeydew and sooty mold. Limonene is made from the skin of citrus fruit - ours is made from orange peels - and is popular in many new household cleaners. For live plants, you need pure limonene and water, without any of the other harsh ingredients in household cleaning products. To get the strength of limonene right requires some experimentation: too strong a solution will cause the hibiscus to defoliate completely, and too weak will not melt the waxy coating. We are now offering Limonene for cleaning your plants that is mixed in water at the optimum strength. You spray it straight onto the mealybugs, and leave it on the plant to clean away the waxy coating and the mealybugs without you having to physically wipe them off. Be sure to use the limonene to clean your plant pots too - around all sides, under the rims, the ground under the pot, everywhere! Inspect your hibiscus several times a week, and spray any new mealybugs you see with the limonene until they completely disappear.

 

Optional Step 3 ~ Beneficial Insects:

An optional final prong of a 3-prong response to mealybugs is to purchase some predator insects that eat mealybugs. One that is widely available is the pretty garden ladybug. If the ladybugs stick around, they will eat mealybugs, aphids, and other common insect pests. The problem with such beneficial insects is that they will often fly away and not stick around to do the job. We consider them an optional, but potentially valuable way to combat mealybugs.

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