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Gardening….. Foe!!!
Mealybugs are the common name for several soft-bodied insects in the family Pseudococcidae. Florida has several species of mealybugs and also a wide variety of plants that commonly host them. Lance S. Osborne with University of Florida’s Entomology Department created a great webpage about mealybugs in Florida. I have a link in the notes at the bottom of this post.
Mealybugs are identified by their waxy white appearance. Their tiny bodies are white, but some species can also have a pinkish color. Eggsacs are white and waxy as well. As you can see in the picture below, a waxy-like substance is usually easily seen on the affected area.
Adult female mealybugs are similar to what you see pictured below. Adult males can appear very similar to white flies. They are smaller than females and winged. If you see small white winged insects, you should look for the female mealybugs. If you don't see female mealybugs, you probably have white flies instead.
Why are mealybugs a gardening foe? For starters, they contribute to the stress, damage, and potentially even destruction of plants. This is particularly noticed in edible landscapes where food producing plants are damaged. Food crops that are most likely to host mealybugs include:
Gynura like Okinawa and Longevity Spinaches
Grape Vines
Bromeliaceae both Pineapples and ornamental bromeliads
Citrus
Papaya
Sugarcane
Cotton
Pear
Mulberry
Persimmon
Cassava
Avacado
It is important to note that like many other food eating insects (including caterpillars), that different species of mealybugs host on different species of plants. Even though all of these food producing crops are susceptible to mealybugs, it doesn’t mean that one infestation will move on to other plant species. Unless of course, the other plant species is also a host plant to that species of mealybug.
Ornamental plants are also host plants for mealybugs. Examples are:
Native clumping grasses like muhly grass
Cycads like Coontie Palms
Ferns
Hoyas
Pothos
Aphelandra
Ardisia
Cryptanthus
Dieffenbachia
Dracaena
False Aralia
What does a mealybug do to a plant? Well similar to other soft-bodied insects, they are sap-suckers. By puncturing the plant tissue with their mouths, they feed on the internal plant sap. Although a mealybug’s feeding may cause stress and stunt plant growth, they do not typically destroy a plant by feeding on it. Instead, plant loss is caused by a secondary effect. Let me explain.
As the mealybugs eat the sap of a plant, a byproduct called honeydew is created. This honeydew creates a very good environment for bacteria and fungi. Disease caused by either of these can destroy the plant. One of the most common fungi to appear is black mold or black sooty mold.
By piercing the plant to “suck the sap”, mealybugs are causing damage to the most important defense mechanism of any life form—including humans. The latin word is the same. The epidermis. With the integrity of the epidermis lost, disease can more readily get inside the plant. Disease to the plant is typically what will lead to complete loss of the plant.
Before we move on to control methods, I want to touch on the relationship between ants and mealybugs. Any insect that creates honeydew as a byproduct of feeding has the potential to establish a unique relationship with ants. Ants want honeydew for food. In exchange for the honeydew, ants will protect these insects from predators. Ants will also move the insects around the plant to new areas to increase productivity or move them away from areas where predators arrive. Wild right? This is called “farming” and is commonly seen.
What do we do about mealybugs??
Firstly, you can remove them by hand. They look gross and unsightly. But they won’t harm you. If touching them is out of the question, try spraying them off with a hose. Otherwise, its best to wait for natural predators to show up.
There are a few predators of mealybugs that will do the job for you - if you are patient enough to give them the chance. Lacewing larvae, ladybeetle larvae, and parasitic wasps are effective at helping control mealybug infestations. But they require a little time to show up.
There is a ladybeetle called “Mealybug Destroyers” that are very effective at managing mealybugs … as the name suggests. The larvae even look like mealybugs. This is important to help themselves from ants that attempt to protect the mealybugs. There are online sources for mealybug destroyers for a decent price. They work great in greenhouse settings.
What should you do if there is no time to wait for predators?
There are some chemical control methods that work well for mealybugs. Fortunately, many are organic. Unfortunately, they aren’t target specific. Meaning that they may have accidental kill of other insects. Here’s the list:
Mix 1 part rubbing alcohol, 1 part water, and 2-3 drops of dawn dish soap. Using a cotton ball or a small craft paintbrush, apply solution directly onto mealybugs. The rubbing alcohol will begin killing mealybugs on contact. The dish soap helps the solution stick to the area by using surfactant.
Neem oil is effective at killing mealybugs but also kills other insects that come in contact with it. Neem oil is organic and takes a few days with multiple applications for a complete kill. Make sure to treat only a few leaves at first to make sure the plant can tolerate the neem oil. Application should be done in the evening in cooler temperatures and not in direct sunlight.
You can also look into other horticulture oils if neem oil is not working for you. Make sure you look at the labels carefully for instructions on use.
Try your own brew of insecticidal soap oil by mixing 1 tbl spoon of vegetable oil, 1 cup of water, and 2-3 drops of dawn dish soap. This mix aims at suffocating the insects by the oil smothering the airway.
Insecticidal Soap is available in many places and online.
Please note that the above-mentioned chemical mixtures may have some negative effects on the plants themselves. It is not recommended to use horticulture oils, or alcohol solutions on plants when temperatures are above 86 degrees F. It is also recommended treatments be done in the evening to reduce complications of sunlight on treatments.
Another option is systemic treatment. This kind of treatment works by applying a chemical that will be taken in by the roots of the plants and then ingested when insects eat the plant material. Anything from plant sap to the entire foliage. Online resources indicate that Dominion 2L, Imidacloprid, and Acephate are effective for systemic control. Unfortunately, these systemic control methods can also cause accidental kill of other insect species.
What methods have you used to control mealybugs? If you have some pro tips, comment on this post to keep the conversation going!
Supportive Links
https://mrec.ifas.ufl.edu/lso/Mealybugs.htm
https://www.solutionsstores.com/mealybug-control
https://blogs.ifas.ufl.edu/seminoleco/2019/06/14/mealybugs/