Mealybugs
Also known as Citrus mealybug (Planococcus citri), Longtailed mealybug (Pseudococcus longispinus), Pseudococcidae
In short
Mealybugs are soft, oval insects coated in white powdery wax that cluster in leaf axils, sheaths and other sheltered spots. They suck sap, excrete honeydew and are among the hardest houseplant pests to eliminate, so checking plants before you buy them matters more than any spray.
How it looks
Oval, segmented, wingless females covered in white wax, with waxy filaments around the edge of the body. The longtailed mealybug has two tail filaments longer than its body; the citrus mealybug has short filaments of equal length and sometimes a faint dark stripe down the back. Eggs are laid in white, cottony sacs. Newly hatched crawlers are yellow-orange and at first have no wax. Males are tiny winged insects that are rarely seen. They gather in leaf axils, leaf sheaths, crowns, branch crotches, along veins and leaf undersides, at stem bases near the soil and wherever plant parts touch; on orchids they also hide in roots and potting media.
Signs
Fluffy white wax in sheltered places, sticky honeydew and black sooty mould, weak growth, wrinkled or yellowing leaves and, in heavy infestations, leaf drop. Ants often tend them.
Life cycle
A female lays 100–200 or more eggs over 10–20 days in a cottony sac. There are two to six generations a year, and indoors or in warm climates all life stages can be present year-round.
What favours it
Warm, sheltered conditions indoors or in the tropics allow continuous breeding. Excess nitrogen fertiliser encourages them, ants protect them from natural enemies, and their waxy coat and hiding places make sprays hard to get onto them.
Prevention
- Inspect plants before purchase, especially leaf axils, sheaths, crowns and roots.
- Quarantine new plants and keep checking them for several weeks.
- Avoid excess nitrogen fertiliser.
- Control ants, which shield mealybugs from predators.
Treatment
Start with the first step and move down only if the problem persists.
- Discard heavily infested plants; eradication is often not realistic.
- Pick off or wipe away mealybugs, and dab individuals with a cotton bud dipped in isopropyl alcohol (70% or less); test on a small area of sensitive plants such as cacti first.
- Wash them off sturdy plants with a firm spray of water.
- Release or protect natural enemies: the mealybug destroyer ladybird (Cryptolaemus montrouzieri), parasitoid wasps (such as Leptomastix and Coccophagus) and lacewings.
- Spray insecticidal soap, horticultural oil or neem oil with thorough coverage, repeating as directed; follow the product label.
- Systemic insecticides (neonicotinoid class) give inconsistent results and can harm natural enemies; use only as a last resort and follow the product label.
Pros and cons
Cons
- Honeydew and sooty mould soil leaves.
- Hidden egg sacs and crawlers make them hard to eradicate, and they spread easily to neighbouring plants.
Look-alikes
- Root mealybugs
- Live underground on roots, lack obvious filaments and are only found when the plant is unpotted.
- Mealybug destroyer larvae
- Beneficial: larvae grow to about 12 mm, have long wax filaments on the top and sides, visible legs, and move much faster.
- Soft scales
- Adult females are immobile bumps; some produce white waxy egg masses but the body itself is a smooth or waxy dome.
Affected plants
Houseplants of almost every kind, including cacti, succulents and orchids, as well as citrus and grapes.
Related
Sources
- Mealybugs — UC IPM Pest Notes
- Indoor plants: sap-feeding insects — RHS
- Orchid Insect and Mite Pests in South Florida (ENY2114) — UF/IFAS
- Insect pests of cacti and succulents grown as house plants — Missouri Botanical Garden
- Mealybug destroyer — UC IPM Natural Enemies Gallery
Written in our own words from these sources. Check a product label before using any treatment.