All About Mealybugs

Mealybugs are a type of scale insect in the family Pseudococcidae. There are a variety of different species but the most common ones we encounter on our houseplants are the long tailed mealybug and the citrus mealybug.

Mealybugs are a sap sucking pest, meaning they pierce the plant and extract the sap, causing stunted growth and deformed, yellowing leaves. As they feed, they leave behind a sticky substance called honeydew, which can be a vector for molds and other plant diseases that can further stress and damage your plant.

Note: Mealybugs are genetically different from root mealybugs, which require different treatment.

The Mealybug Lifecycle

Understanding the mealybug life cycle is essential to treating them successfully.

There are two species of mealybugs most commonly found on our houseplants: The long-tailed mealybug and the citrus mealybug.

Long-tailed mealybugs can produce sexually or asexually, although they more commonly produce asexually. Unlike most other mealybug species, long-tailed mealybugs give birth to live young, depositing first instars beneath a pile of waxy filaments and threads. Their average reproduction rate is about 100-200 nymphs per female over 2-3 weeks. Their life cycle ranges from six weeks in the summer to about 12 weeks in the winter.

Citrus mealybugs are the most common type of mealybug. Although their name suggests they are specific to citrus plants, they can be found on a diverse range of plants, from fruit trees to ornamentals like palms, ficus and roses and also on a variety of vegetables. The number of eggs laid by each female varies from 100 to 600 depending on temperature and host plant, and egg laying occurs during a one to two week period. The length of the life cycle is also high temperature and humidity depending, but usually takes about one to two months.

What Mealybugs Look Like

All life stages of mealybugs are visible to the naked eye, but the adults are easiest to spot. The first instar nymphs are very small (around 0.6 mm long!) and more closely resemble mites than adult mealybugs. The nymphs are referred to informally as “crawlers” because they are the most mobile of all the life stages and move quickly.

As mealybugs become adults, they become much more sedentary, often settling in one place on the plant to feed. The adults are the ones most people are familiar with—fuzzy white oval bugs—are all female. Male mealybugs have wings, which allow them to easily move from plant to plant.

Adult female mealybugs are hairy, white, oval-shaped insects that are about 1/8-inch long and covered in a powdery substance. These are the ones that feed and lay eggs on your plant. Adult males look quite different than the females—more like a gnat, with a thin body and wings (and you can catch them on sticky traps, which can help with population knockdown and management).

They tend to congregate in hidden crevices and just below the soil at the root line, so make sure to check and clean these areas thoroughly if you suspect an infestation. Different species of mealybugs tend to prefer different types of plants, but they are all similar in appearance.

Inspecting for Mealybugs

One good thing about mealybugs is that they are generally easy to spot and identify. In addition to adult mealybugs being slow-moving and easily visible to the naked eye, they leave behind a white, cottony, wax debris that is easy to spot. A sticky substance on the plant—as if juice has been spilled on them—is one of the earliest signs of a mealybug infestation.

As with other houseplant pests, it’s important to check your entire plant thoroughly, including in small spaces and crevices. Mealybugs can also hide just below the soil line; make sure to pull your soil or growing medium back from your plant to check there.

If you see something white on your plant but aren’t sure if it’s a mealybug, you can dab it with a swab dipped in isopropyl alcohol. If it is a mealybug, it will turn brown upon contact with the alcohol.

Examples of Mealybug Damage

Unlike other pests like thrips or spider mites, mealybugs don’t create a distinct damage pattern. Rather, they cause overall plant decline. This normally presents as yellowing leaves, dropped leaves, stunted or distorted new growth, or no new growth at all.

Treatment Overview

A comprehensive, integrated pest management plan for mealybugs includes two equally important components:

  • Manual rinsing and removal of pests.
  • Predators to manage various life stages.
    • For the larger instars and adults: Cryptolaemus larvae or lacewing larvae.
    • For eggs and crawlers in the growing medium: Stratiolaelaps mites.

For active infestations, release fresh foliage predators every two weeks for roughly three consecutive treatments, or until you no longer see mealybugs. This timeline is flexible, however, depending on the severity of the infestation.

When you see mealybugs, the first step is to remove them with water, just like any other pests. Wiping them off with a wet paper towel works well, using a Q-tip to get in the smaller crevices. Also make sure to check and clean just below the soil line—about a half-inch or so—at the base of the plant, where mealybugs often hide.

 

Spraying with a strong jet of water also works well. Just make sure to spray your plant at an angle that avoids the growing medium. You want to wash your mealybugs down the drain, not into your growing medium where they can just crawl back up onto your plant.

Manual Rinsing and Removal

This manual removal with water—also referred to as “population knockdown”—is an essential part of integrated pest management. Skipping this step is a common mistake that hinders the ability for beneficial insects to be effective and results in a longer-lasting, potentially more widespread infestation.

Spraying with a strong jet of water also works well. Just make sure to spray your plant at an angle that avoids the growing medium. You want to wash your mealybugs down the drain, not into your growing medium where they can just crawl back up onto your plant.

This manual removal with water—also referred to as “population knockdown”—is an essential part of integrated pest management. Skipping this step is a common mistake that hinders the ability for beneficial insects to be effective and results in a longer-lasting, potentially more widespread infestation.

Here’s how we recommend manually removing mealybugs (before releasing beneficial insects):

  1. As soon as you notice mealybugs on a plant, isolate it from any other plants.
  2. Check neighboring plants for mealybugs or signs of mealybugs (white powdery debris, leaf yellowing, plant decline).
  3. Manually wipe or rinse off the plant to remove visible mealybugs.
  4. Order beneficial insects (see below for which ones).
  5. Continue to check your plant and spot-remove any mealybugs until your beneficial bugs arrive.
  6. On the day your beneficial bugs arrive, wipe down your entire plant once more before applying the predators.

Selecting Predators

Cryptolaemus larvae (the larvae of cryptolaemus montrouzieri) are extremely effective foliage predators for mealybugs—it’s no wonder they carry the nickname “mealybug destroyer.” They are a bit more aggressive than lacewing larvae and may require fewer consecutive releases, depending on the extent of the mealybug infestation. Cryptolaemus larvae are especially recommended for heavy mealybug infestations.

Two important notes:

  • Cryptolaemus larvae look very similar to adult mealybugs. Make sure you can tell the difference so you don’t accidentally spot-remove the good guys!
  • Make sure to order cryptolaemus larvae, not cryptolaemus beetles (the adult form of cryptolaemus montrouzieri) are not recommended for houseplants. In a home environment, the larvae are more effective than the beetles; beetles work better in a larger greenhouse environment where they are able to reproduce.

Lacewing larvae are another very effective foliage predator for mealybugs. They do not require the same amount of food as cryptolaemus larvae and can be a more cost-effective option for larger collections, but may require three to four consecutive releases (every two weeks) in order to fully rid your plant of mealybugs.

If your budget allows, you can release both cryptolaemus larvae and lacewing larvae on your first release, followed by only one or the other for subsequent releases.

Stratiolaelaps mites are an excellent soil predator (in fact, they work for both soil and semihydro growing setups). They are an effective complement to foliage predators, as Stratiolaelaps will venture along the surface of and down into your growing medium to patrol for eggs and larvae that foliage predators can’t reach.

Stratiolaelaps should live up to eight weeks in ideal conditions, so you generally only need to release them with your first release.

Release Timeline

If you’re new to beneficial insects or are using a new type of predator, visit our Release Tutorials for step-by-step guides.

In two-week increments:

  • Release 1: Cryptolaemus larvae or lacewing larvae (or both), and stratiolaelaps.
  • Release 2: Cryptolaemus larvae or lacewing larvae.
  • Release 3+: Lacewing larvae, as needed if you are still seeing signs of mealybugs.

For protection and prevention once you have eliminated your mealybug population, do one final release of lacewing larvae four weeks later, and another six weeks after that. If the population has not returned during this time, you can switch to a regular prevention schedule of releasing lacewing larvae every 3-4 months. Cryptolaemus larvae are not recommended for preventative releases.

Common Mistakes When Treating Mealybugs

  • Not wiping or rinsing off a plant to manually remove mealybugs before releasing beneficial insects.
  • Not scouting and manually removing mealybugs while treating (you and your predators are a team!).
  • Not checking nearby plants when you find evidence of mealybugs on a plant.
  • Not checking and cleaning just below the soil line of the plant.