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How to identify it
- Look inside the shrub, around branch crotches and forks, for clusters of white mealybugs; they are hard to see without parting the dense foliage.[1][2][4]
- Adult females are covered in white powdery wax, with waxy filaments along the sides and a longer pair at the rear; the body underneath is red, and a crushed one leaves red fluid. UMass gives their length as about 0.16 inch.[1][2]
- Sticky honeydew and black sooty mold on the needles and branches are often the first thing noticed.[1][2][3]
Look-alikes
| Look-alike | How to tell them apart |
|---|---|
| Comstock mealybug | Sometimes found on yew too, but its body and fluid are brown rather than red, and it lays eggs in a cottony sac; the taxus mealybug produces no egg sac.[1] |
| Fletcher scale | Another yew pest that leaves honeydew and sooty mold, but it is a small, round, brown soft scale at the bases of the needles.[3] |
Where it lives
Thought to occur throughout the northeastern United States, including Massachusetts, New York, Connecticut, New Jersey, Pennsylvania and Ohio, and into the central states; it was likely introduced from Japan on yew around 1915.[1]
Biology and life cycle
Young nymphs overwinter in bark crevices and resume feeding in spring; by early summer they are adults, which give birth to live young rather than laying eggs.[1][2][4]
Few live mealybugs are seen in April and May, but numbers can build considerably by mid-June; adults are present from June to August and mostly gone by September.[1]
Sources differ on generations: UMass cites one a year from Connecticut northward and two or three from New Jersey southward, and the University of Kentucky says one to three, depending on the state.[1][2]
Damage and signs
Health risk
It feeds only on plants; none of the sources reports any harm to people or pets.[1][2]
Control
Prevention
Keep yews healthy and unstressed, and check them by parting the branches and looking inside around the crotches.[4][1]
Biological control
Parasitic wasps, lacewings, syrphid fly larvae and lady beetles attack it; controlling the ants that tend mealybugs for their honeydew helps those natural enemies.[4]
Pesticides
The waxy coating makes taxus mealybugs hard to control; UMass and Rutgers time crawler treatments for about 246 to 618 growing degree days (base 50°F), and UMass also lists a dormant-season window. Follow the label of any product you use.[1][4]
Common questions
- What are the white fuzzy bugs inside my yew?
- White, waxy insects clustered in the branch crotches of a thinning yew are most likely taxus mealybugs; a crushed one leaves red fluid.[1][2]
- Why are my yews sticky and black?
- Honeydew from sap-feeding insects such as the taxus mealybug and Fletcher scale coats the needles and grows black sooty mold.[1][3]
Sources
- UMass Extension Landscape, Nursery and Urban Forestry Program (Landscape Insect & Mite Guide), “Dysmicoccus wistariae, previously Pseudococcus cuspidatae (Taxus Mealybug).” www.umass.edu/agriculture-food-environment/landscape/publications-resources/insect-mite-guide/dysmicoccus-wistariae-previously-pseudococcus-cuspidatae (accessed 2026-10-17)
- University of Kentucky Entomology, “Common Insect Pests of Yew/Taxus (Tree Pest Guide).” uky.edu/Ag/Entomology/treepestguide/taxus.html (accessed 2026-10-17)
- University of Minnesota Extension (What's wrong with my plant?), “Yew: raised bumps on twigs or branches.” apps.extension.umn.edu/garden/diagnose/plant/evergreen/yew/branchesbumps.html (accessed 2026-10-17)
- Rutgers Cooperative Extension (Nursery IPM), “Taxus Mealybug (Nursery IPM).” sites.rutgers.edu/nursery-ipm/taxus-mealybug/ (accessed 2026-10-17)
- iNaturalist, “Dysmicoccus wistariae taxon page (order and family).” www.inaturalist.org/taxa/1328359 (accessed 2026-10-06)