Cryptolaemus montrouzieri
Mealybug destroyer- Rate
- 2–10 /m² per release, or 5 per infested plant
- Temp
- Best 22–28 °C; slows below 16 °C
- Best for
- Less effective here: it lays its eggs among egg sacs, which this species lacks
Pest
Long-tailed mealybug
Pseudococcus longispinus
The short answer
The long-tailed mealybug is a soft, white, wax-covered insect with two tail filaments about as long as its body or longer. It is common on houseplants, orchids and tropical foliage plants. It gives birth to live young instead of laying cottony egg sacs, so there is no egg mass to find. Dab small colonies with diluted rubbing alcohol and check the plant weekly; a heavily infested plant is often better thrown away. The mealybug destroyer beetle works less well on this species than on citrus mealybug.
hero macro · adult, tail filaments visible
Long-tailed mealybug (Pseudococcus longispinus) female showing the two long tail filaments. Photo: pending.
Identification
Adult females are soft, oval and dusted with white powdery wax, with wax filaments round the edge and two long tail filaments. UConn puts the tails at three-quarters of the body length or more; UC describes them as almost as long as, or longer than, the body. Mealybug females are 2–5 mm long when full-grown. The males are rarely seen: tiny, two-winged insects.
The citrus mealybug, the commonest mealybug on indoor plants, has short filaments of equal length and often a dark stripe down its back, and it lays its eggs in cottony sacs. Root mealybugs live in the compost and have no obvious filaments. Cottony cushion scale, woolly aphids and some soft scales and whiteflies can look similar, so check the insect under the wax.
Easily confused with
- Mealybug destroyer larvaeBeneficial — leave itLarvae grow to 1/2 inch (12 mm), more than twice the size of an adult female mealybug, move faster and carry long wax filaments on the top and sides of the body.
- Citrus mealybugAlso a pestShort, equal-length wax filaments round the body and cottony egg masses; long-tailed mealybug has two tail filaments about as long as its body or longer and bears live young, so no egg sacs.
- Parasitised mealybugsBeneficial — leave itMummified mealybugs with an emergence hole, or parasite pupae among the colony, mean parasitic wasps are already at work.
Damage symptoms
Mealybugs suck phloem sap. A large colony slows growth, yellows the leaves and can cause leaf drop, although a healthy plant tolerates a few. They excrete honeydew, on which black sooty mould grows. They gather where leaves meet stems, in leaf sheaths and on leaf undersides, so a colony is usually well established by the time it is noticed.
- White waxy insects in leaf axils, leaf sheaths and under leaves
- Sticky honeydew and black sooty mould
- Yellowing leaves, stunting or wilting in heavy infestations
- Leaf drop on heavily infested plants
- No cottony egg masses — just insects of mixed sizes
Lifecycle & degree days
Most mealybugs lay 100–200 or more eggs in a cottony sac. The long-tailed mealybug keeps its eggs inside the body until they hatch, and females reproduce without mating. Indoors and under glass, all stages can be present all year. Mealybugs develop slowly for a greenhouse pest: about 60 days from egg to adult, depending on temperature and host plant. Outdoors in California this species has two to four overlapping generations a year.
- Reproduction
- Live young; no mating needed
- Egg to adult
- About 60 days (mealybugs generally, KSU)
- Generations
- 2–4 a year outdoors (California); continuous indoors
- Adult female
- 2–5 mm (mealybugs generally)
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Host crops
UC lists citrus, grapes, nursery stock and indoor ornamentals as hosts. UConn says many tropical foliage plants and houseplants are susceptible, and UMass notes it can be a major problem on cycads, orchids and ferns in conservatories.
Monitoring & action thresholds
Action threshold
None set — act on the first colony
No numeric threshold exists for mealybugs on houseplants. Colonies hide and build slowly, then seem to appear all at once, so KSU advises regular inspection of susceptible plants. UC advises checking new plants before they come indoors, and discarding any you cannot clean.
Mealybugs do not fly, apart from the short-lived males, so yellow sticky cards will not find them. Inspect by eye: leaf axils, stem tips, leaf undersides, the sheaths of orchids, and pots and stakes. In a larger collection, tag five to ten plants of each susceptible kind and check them regularly.
Beneficial
Biological control
Biological control is harder than for citrus mealybug. The mealybug destroyer lays its eggs in mealybug egg sacs, and this species makes none, so UMass rates it less effective on this species. UC Pest Notes and UMass say Leptomastix dactylopii kills only the citrus mealybug, and KSU (2011) says no parasitoid is sold for the long-tailed species. Outdoors in California, UC names three parasitic wasps (Acerophagus notativentris, Arhopoideus peregrinus, Anarhopus sydneyensis) and predators including green lacewing larvae and lady beetles, and says controlling ants makes numbers fall.
Cultural controls
On houseplants, physical removal and plant hygiene do more than any product. Every treatment misses some insects, so check again weekly.
- Dab small colonies with a cotton swab dipped in 70% or weaker rubbing alcohol; test it on a small part of the plant a day or two first
- Hose sturdy plants with a forceful spray of water, repeated every few days
- Inspect new plants before bringing them in; return or discard any you cannot clean
- Throw out old, heavily infested 'grandmother' plants
- Avoid heavy nitrogen feeding, which boosts mealybug numbers
- Keep ants off infested plants
Chemical, last resort
The wax repels most sprays; soaps and oils mainly suppress young nymphsCheck any product before it goes on. Open the compatibility matrix →
Rating: the effect on this pest's natural enemies if a spray hits them or they feed on treated plants. REI is the re-entry interval on farm and greenhouse labels; home labels usually give none, so follow the label.
Sources
UC IPM Pest Notes: Mealybugs, Pub. 74174 (M.L. Flint, 2016)
UC IPM Avocado Pest Management Guidelines — Longtailed mealybug (updated 2016)
UConn Extension — Managing Mealybugs in the Greenhouse (L. Pundt, rev. 2024)
UMass Extension — Mealybugs in Greenhouses
Kansas State Univ. MF3001 — Mealybug Management in Greenhouses and Interiorscapes (Cloyd, 2011)
RHS — Indoor plants: sap-feeding insects
Page status
Drafted from the sources below, then checked claim by claim against those sources on 23 September 2026.
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