Mealybugs

Garden pest · Pseudococcidae

Description

Mealybugs are small, sap-feeding insects in the family Pseudococcidae. They occur on many houseplants, ornamentals, fruit crops, and greenhouse plants. Most visible adults are soft-bodied, oval, and covered in a white, waxy coating that gives them a cottony appearance. They often gather where leaves join stems, along leaf veins, and in other sheltered crevices; some species feed on roots. Mealybugs weaken plants by removing sap. Their sugary waste, called honeydew, makes surfaces sticky and can support black sooty mold. Heavy infestations may cause yellowing leaves, distorted new growth, stunting, and leaf drop. Ants sometimes protect mealybugs while feeding on their honeydew, allowing populations to grow. Females may lay eggs in fluffy wax or, depending on the species, give birth to live young. The small, mobile young, known as crawlers, can spread between plants. Indoor and greenhouse infestations can persist year-round.

Symptoms

• Yellowing leaves
• Sticky residue on leaves
• Black sooty coating
• Curled or cupped leaves
• Distorted new growth
• Stunted growth
• Leaves dropping
• Insects visible on the plant

How to Identify

Look closely at leaf joints, undersides, growing tips, and other sheltered spots for clusters of oval insects with white, powdery wax and sometimes short wax filaments around their edges. They may leave cottony egg masses and sticky honeydew nearby. The tiny young can move across the plant. Root mealybugs appear as white, waxy insects among roots or around drainage holes. Unlike powdery mildew, the white material consists of individual insects or waxy clusters rather than a broadly spread coating on leaf surfaces. Whiteflies fly up when disturbed; mealybugs usually remain in place or crawl slowly. Some scale insects look similar, so check for the characteristic soft, segmented bodies.

Prevention

Inspect new plants carefully, especially leaf joints and undersides, and keep them separate from existing plants while watching for pests. Check established plants regularly so small colonies are found before they spread. Avoid crowding plants: leave enough room to inspect them and prevent leaves from touching where practical. Clean tools, pots, and growing areas, and remove fallen plant debris. Avoid excessive nitrogen fertilizer, which can encourage tender growth attractive to sap-feeding pests. Where ants are tending mealybugs, manage the ants with barriers or appropriate baits so natural enemies can reach the colony. Inspect roots when repotting plants that repeatedly become infested. In greenhouses or indoors, monitor nearby plants after finding mealybugs, since crawlers can spread beyond the first visibly affected plant.

Treatment

Isolate an infested potted plant. For a small outbreak, remove mealybugs with a cotton swab dampened with 70% isopropyl alcohol, testing a small area first because some plants are sensitive. Prune heavily infested growth if doing so will not seriously harm the plant, and discard the cuttings. Rinse sturdy plants to dislodge insects, taking care not to spread them to others. If pests persist, apply insecticidal soap or horticultural oil labeled for the plant, thoroughly covering leaf joints and undersides. Follow the label and repeat as directed to catch newly hatched crawlers; avoid spraying heat-stressed plants. Outdoors or in greenhouses, protect natural enemies such as lady beetles and lacewings, and control tending ants. For root mealybugs, discard infested potting mix, wash the pot, and repot after gently cleaning the roots. Check plants repeatedly over the following weeks; severely infested plants may be best discarded.

Plants Affected

Aloe Vera, Amaryllis, Anthurium, Banyan, Baobab, Bay Leaf, Bird of Paradise, Bougainvillea, Cassava, Christmas Cactus, Corpse Flower, Crown of Thorns, Curry Leaf, Desert Rose, Echeveria, Frangipani, Heliconia, Indian Rubber Tree, Jade Vine, Jasmine, Kadupul Flower, Orchid, Orchid Cactus, Palm, Pineapple, Plumeria, Sacred Fig, Sago Palm, Tamarind, Taxus, Weeping Fig, Yam, Yucca

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