What Are Mealybugs?

The mealybug is a pervasive crawling insect, a common pest of plants in homes and greenhouses. The name comes from their appearance; they look like they’ve been rolling around in flour,

Katelyn A. Kesheimer, Ph.D., an assistant professor at the Alabama Cooperative Extension System (Auburn University), says mealybugs can also be a problem outdoors, especially with tropical plants. In the warmest climates, they occasionally attack shrubs or woody ornamentals or infest summer annuals.

What Is a Mealybug?

A small, soft-bodied “scale” insect, mealybugs belong to a family of species closely related to aphids. They generally feed on ornamental plants, including annuals, perennials, shrubs, palms, grasses and trees.

What Do Mealybugs Look Like?

Female mealybugs grow to be about 1/4-in. long and 1/8-in. inch wide. Their oval bodies are covered in a white, waxy secretion that can form filaments resembling tiny spines or hairs.

Male mealybugs are smaller and distinctly different from their female counterparts, with two transparent wings and long tail filaments.

Where Are Mealybugs Found?

Native to Asia, mealybugs are found throughout the Americas, Europe and Oceania.

Of the estimated 275 species inhabiting the continental United States, the citrus mealybug is the most widespread by far. It’s followed by longtailed, Mexican and Pritchard’s ground mealybugs.

What Are Mealybugs Attracted To?

Mealybugs are big fans of warm, moist environments — the warmer, the better. This is why they gravitate to greenhouses. Their favorite types of plants include:

• Citrus and other fruit-bearers;
• Succulents and cacti;
• Ornamental varieties like gardenias;
• Tropical houseplants like ficus, pothos, orchids and philodendrons.

Mealybugs will infest roots, stems and foliage of plants, but usually not flowers.

Are Mealybugs Destructive?

Yes!

“As far as I know, mealybugs do NOT have any redeeming qualities,” Kesheimer says. “They are a pain in the butt and very hard to control.”

Once they settle in on a plant, they can easily migrate to adjacent plants or be carried by the wind. Mealybugs use their piercing mouthparts to penetrate the surface or “skin” of plant matter and feed on its tissue.

“They excrete a sugary waste product called honeydew that can promote the growth of a black fungus called sooty mold,” Keshiemer says. “It is unsightly on ornamental plants but can also reduce plant or fruit quality.”

Negative effects on plants include wilting, yellowing, premature leaf drop and distorted growth. If left unchecked, mealybugs can literally suck the life out of plants.

Note: Some mealybugs are known to transmit viruses on a small number of plants, like grapes. However, home gardens and greenhouses are rarely affected.

Do Mealybugs Bite Humans?

No. Their piercing mouthparts aren’t strong enough to penetrate human skin.

How To Control Mealybugs

As mentioned earlier, mealybugs are hard to get rid of once populations are established. It’s therefore essential to move quickly and employ the right methods to successfully eradicate them.

Monitor regularly

The best defense against an infestation begins with your eyes. If you notice plants seem limp or otherwise sickly, or you see mold forming on the tops of leaves, look closer.

“Mealybugs prefer protected areas on plants where they can be lazy, not move around and just grow their colony,” says Kesheimer.

They could be lurking on stems at the soil line where leaves touch; where fruits/leaves touch; at the plant crown; or where two branches form a tight “V.”

Avoid a mealybug “Trojan Horse”

Many commercial plant growers are known to throw away entire batches of mealybug-infested plants, rather than treat them with chemical insecticides. That’s because most insecticides are ineffective, since mealybugs hide on the underside of leaves and in crevices, protected by their waxy covering.

“For those buying plants and putting them into your home/greenhouse/landscape, always inspect the plants to make sure you are not bringing in mealybugs,” Kesheimer says.

Go ahead and mess with Mother Nature

In greenhouse environments, releasing natural enemies like parasitoids and predators have proven successful at controlling mealybugs. Examples:

• Lacewings (green and brown);
• Parasitic wasps;
• Small ladybeetles (Cryptolaemus montrouzieri).

Kesheimer also suggests “generalist predators” listed below. These beneficial pests capture and eat not only mealybugs but other small insects as well:

• Minute pirate bugs;
• Spiders;
• Assassin bugs;
• Damsel bugs;
• Other ladybug species.

Note: Natural predation may keep mealybug populations at bay, but will not completely eliminate them.

Home remedies

“Honestly, what we do in our greenhouse is scout regularly and when we find mealybugs, we squish them with our fingers,” says Kesheimer. “It is oddly satisfying and works!”

Other ways to get rid of mealybugs:

• Spray plants with water at a high enough pressure to remove them without harming plants.
• Wash plants with soapy water (one tablespoon of dish soap to one gallon of water). Be careful not to overdo the soap! Too much could kill “good” bugs and the plant itself.
• Spot treatments. “I find it easiest to use Q-tips dipped in isopropyl (rubbing) alcohol to remove bugs and their egg masses,” Kesheimer says. Depending on what percentage of alcohol you have, she recommends diluting at 50% to 70% so you don’t damage the plant.

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