How to Control Mealybugs

When it comes to dinner, mealybugs don't differentiate between garden and indoor plants. If it has stems, leaves and sap, the grayish, segmented insects arrive in droves to feed by piercing plants with their hollow, needle-sharp mouths. By the time they've finished, a plant may be drenched in their clear, sticky waste and covered in their white, waxy or cottony shed skins. Controlling large mealybug colonies is a challenge, so it's best to strike back as soon as they appear. Your control options include items from the garden shed or medicine cabinet and a friendly insect that devours mealybugs at an astonishing rate.

A garden hose with a nozzle set on sharp stream makes an excellent weapon against mealybugs. Turn it on your plants at close range, and targeting the undersides of the foliage where the pests love to feed. The concentrated blast of water, called syringing, removes up to 90 percent of an infestation, according to You Bet Your Garden host Mike McGrath. Syringing is especially useful on trees or tall shrubs with hard-to-reach branches. If the weather permits, move your houseplants outdoors for treatment. Spray for at least three consecutive days to eliminate newly hatched larvae. To limit your plants' risk of fungal infection, treat them in the morning so they dry quickly.

Eliminate mealybugs from small, lightly infested plants by dabbing each one with a soft toothbrush or cotton swab dipped in rubbing alcohol. It dissolves their waterproof, waxy covering and kills them. Be sure to reach mealybugs hiding in leaf crevices. On large plants or for serious infestations, use a homemade spray solution containing 1 cup of rubbing alcohol and 1 teaspoon of ready-to-use insecticidal soap in 1 quart of water. Thanks to the soap, it suffocates newly hatched larvae and eggs. At the first sign of the pests, spray thoroughly until all the plants' surfaces drip. Use it every one or two days until they’re gone.

The mealybug destroyer (Cryptolaemus montrouzieri) is a tiny, brown-and-orange lady bug with a ferocious appetite. In the larval stage, it's nearly indistinguishable from its prey and eats up to 250 of them before pupating. In addition to turning mealybugs into meals, the female adults deposit eggs in the pests' fluffy white egg sacs where their offspring get to work as soon as they hatch. Use the commercially available lady bugs on your outdoor plants when temperatures are consistently above 56 degrees Fahrenheit. After misting your infested plants in the evening, release between two and eight of them -- depending on the extent of the problem -- for each 10 square feet of soil.

Ants often appear on outdoor plants to feed on honeydew, the mealybugs' sugary waste. They defend this food source by attacking lady bugs, lacewings and other mealybug predators. Controlling them is crucial to your success. Prune tree and shrub branches touching the ground or nearby structures so they climb the trunks, and wrap the trunks with thick paper coated in petroleum jelly to trap them. Bolster these efforts by placing bait dispensers of low-toxicity, liquid boric acid products along the ant trails around your plants. They'll transport it back to their nests, where it will eliminate the colony in a few weeks. Put the bait where it won't endanger children or pets.