How Do I Control Mealybugs on My Plants?

Mealybugs are a fuzzy-looking white pest that sucks the sap from plants and causes malformation of leaves and flowers with a toxin in their saliva. Mealybugs are easy to detect visually, usually near the upper part of infested plants. They resemble white "cotton" and leave sticky sap spots. Mealybugs present a serious threat to worldwide agriculture, nurseries and the forestry industry. On a small scale, they can be controlled with physical removal. Wide scale infestations require management with a variety of powerful pesticides.

Identifying Mealybugs

Mealybugs are white, soft-bodied pests measuring 1/5 to 1/8 inch. Mealybugs, of the species Paracoccus marginatus, crawl from plant to plant, or are transported by humans and animals. Mealybugs live about 30 days and reproduce slowly so they are easier to eradicate than other types of pests. Mealybugs can infest tropical fruits, houseplants, ornamental plants and various other flora. There are a number of types of mealybugs, including the papaya mealybug and the pink hibiscus mealybug. Mealybugs live in most tropical areas of the world. All mealybugs feed from their host plants by piercing with their mouth parts and sucking out sap. Mealybugs flourish in warm, dry weather and thrive indoors, which makes them a threat to houseplants even in cold climates. The first line of defense against mealybugs is to prevent their transmission. Carefully check new plants for signs of the bugs before introducing them to a garden, yard or home. Destroy infested plants or isolate until mealybugs have been eradicated.

Control and Eradication

Mealybugs reproduce slowly, which helps in removing an infestation. On a single houseplant, or in a very isolated outdoor infestation, mealybugs can be killed with your fingers. A cotton swab soaked in rubbing alcohol will kill mealybugs that are hard to remove by hand. Mealybugs hide in the joints where leaves attach to stems, buds and new leaves, so clean these areas carefully. Misting plants with Safer's Ultra Fine Oil helps fight mealybug infestations. Repeat physical removal of mealybugs daily, until there is no more evidence of the pest.

Severe or large scale infestations are fought with chemical sprays. Chemical pesticides that are effective against mealybugs include the active ingredients malathion, carbaryl, acephate, diazinon, chlorpyrifos and dimethoate. White mineral oils may also kill mealybugs. Because mealybugs have thick, waxy outer skin, twice the normal dose of pesticides is usually required. Use of pesticides is problematic because the poisons may kill non-destructive bugs and pollute the environment. Biological control of mealybugs is an alternative. A commercially available insect, the mealybug destroyer, Cryptolaemus montrouzieri, is effective against mealybugs. Other natural enemies of mealybugs include lady beetles, lacewings, and hover flies.

References

• Denver Plants
• University of Florida
• United States Department of Agriculture