They may look like little fluffy cotton balls with legs, but the damage mealybugs can do on houseplants and in the outdoor garden is serious. Mealybugs, a cousin to other garden pests like scale and whiteflies, can damage many flowering and ornamental plants by direct feeding and by introducing diseases into the garden. Organic gardeners can control this pest in several ways without resorting to pesticides.
Mealybugs are tiny insects, about 1/8 inch in length, but their color and clustering habit make them easy to find on garden plants. Most common mealybug species are white and have filaments covering their bodies and giving them a fuzzy or hairy appearance. An exception is the hibiscus mealybug, which is pinkish-brown and lacks the fringe.
Mealybugs feed on garden plants by inserting their sharp mouthparts into the leaves and stems to suck sap. Damaged leaves look wrinkled or puckered. They can also contaminate cut flowers with webby egg sacs and clusters of larvae. The honeydew excreted by mealybugs compounds the damage from feeding, as it harbors black sooty mold and encourages the spread of plant viruses.
3 Ways to Get Rid of Mealybugs Naturally
You can manage small mealybug infestations with a simple blast of water. Use a plain jet of water to disrupt the bugs' feeding, and spray plants with neem oil to discourage the bugs from coming back. Neem oil spray will not affect bees, making it ideal for the pollinator-friendly landscape. You can also kill mealybugs directly by wiping them with a cotton swab dipped in rubbing alcohol.
For more extensive problems, consider integrated pest management (IPM) or biological treatment, or you can simply spray for the bugs with organic insecticide.
Integrated Pest Management
IPM strategies often employ natural predators of the target pest to help eliminate it or reduce its numbers. Several species of parasitic wasps prey on mealybugs. If you have a flower garden, you can attract these predators with nectar-rich plantings of yarrow, sweet alyssum, and bee balm. Lacewings and pirate bugs also feed on mealybugs. Therefore, be careful not to eradicate these pests with insect spray, even if the spray is organic, to avoid affecting other creatures.
The honeydew excreted by mealybugs attracts ants, which aren’t pests themselves, but they protect mealybugs from natural predators. Planting common vetch as a cover crop can draw ants away from mealybugs by providing a supplemental nectar source. Gardeners can also discourage ant colonies by tilling the surface of the soil to disrupt nests.
Organic gardeners have at least two commercial options for biological mealybug control. The ladybug species Cryptolaemus montrouzieri, commonly called the mealybug destroyer, feeds voraciously on mealybugs at all stages of development. In fact, gardeners must take care not to mistake this beneficial insect for a pest, as the larvae of this ladybug resemble mealybugs. Gardeners can order adult mealybug destroyers to release during periods of high infestation, and this ladybug will feed on other garden pests like aphids or thrips when the mealybugs are gone.
As soft-bodied insect pests, mealybugs are susceptible to insect soap sprays. Sprays must be applied directly to the insects to disrupt their cell membrane and kill them. These sprays do not work as preventative agents. Insect soap is a short-acting spray, and you must reapply it weekly for as long as the pests are active.
The biggest drawback of insect soaps is their potential to burn or otherwise damage plants. To reduce damage to the plants, spray plants with the soap in the evening, then spray them with water in the morning. High temperatures and sunlight increase plant damage from insect soap.
What Causes Mealybugs
Mealybugs are attracted to many indoor and outdoor plants for food. In addition, any plant that has experienced high nitrogen levels from over-fertilization will be especially appealing to the pests. Watch out for mealybugs on the following plants:
- English ivy
- Gerbera daisy
Mealybugs and their nymphs thrive in greenhouses, so they're commonly found on new houseplants. To prevent bringing mealybugs into your home, isolate new houseplants for one week before placing them around other houseplants. During the isolation period, inspect the plants each day for signs of white mealybugs or their webbing, and kill any insects with a cotton swab dipped in rubbing alcohol.
Outdoor plants cannot reliably be protected from mealybugs because they're no way to limit the insects' movement. However, thriving populations of mealybug predators can help control their numbers.
Mealybugs vs. Aphids
Mealybugs are commonly grouped with or discussed alongside aphids because they attack many of the same plants and have similar effects on plants, and both insects can also be controlled with similar treatments. It's hard to spot aphids or mealybugs from a distance, so all discovery of their presence happens with close inspection. And that's where their similarities end.
Aphids like to occupy the undersides of leaves, and they are active movers, while mealybugs are often visible from above as well as below, and they like to stay put. Aphids are larger than mealybugs and can be one of several colors, including bright green, brown, black, yellow, gray, pink, or white. They can have a waxy, furry appearance, but they do not have the telltale cottony look of mealybugs.
Where Should I Look For Mealybugs?
Mealybugs can be found on any part of a plant, including the roots, flowers, and fruit as well as all foliage. They often collect around the axils or nodes of stems.
Can Mealybugs Fly?
Only male mealybugs have wings and are capable of flight. However, they are not capable of feeding; their primary purpose is to fertilize the females.
Can Mealybugs Survive Winter?
It is possible for some mealybugs to survive winter as nymphs and eggs, but generally they arrive as part of a new resurgence each spring. These insects cannot survive at temperatures under 47 degrees Fahrenheit. They survive best at 86 degrees Fahrenheit.
Mealybugs. University of California Agricultural & Natural Resources.
Least-Toxic Control Methods to Manage Indoor Plant Pests. University of Missouri Extension.
Bertin, A., et al. Temperature Thresholds and Thermal Requirements for Development and Survival of Dysmicoccus Brevipes (Hemiptera: Pseudococcidae) on Table Grapes. Neotropical Entomology, vol. 48, no. 1, 2019, pp. 71–77. doi:10.1007/s13744-018-0623-6