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How to identify it
- Adult females are wingless, soft, oval and flattened, pink to dark purple under a coat of white, mealy wax, with a ring of waxy filaments around the body; the filaments at the rear are long and get shorter toward the head.[2][3]
- Eggs are yellow to orange and laid in white, cottony egg sacs. UC IPM describes the crawlers as yellow to orange-brown; the PNW handbook describes nymphs as purplish under a powdery wax coat that thickens as they grow.[1][2][3]
- Grape mealybug closely resembles obscure mealybug. Gently probe a female with a sharp point without piercing her: reddish orange defensive fluid suggests grape mealybug, clear fluid suggests obscure mealybug.[1]
- Because it rests in winter and its two generations do not overlap, usually only one or two life stages are present at a time.[1]
Look-alikes
| Look-alike | How to tell them apart |
|---|---|
| Obscure mealybug | Very similar, but it releases clear defensive fluid when probed, does not rest in winter, and has overlapping generations, so all life stages are present on the vine year round.[1] |
| Longtailed mealybug | Another Pseudococcus in vineyards; it gives birth to live crawlers instead of laying eggs in a sac, and it does not rest in winter.[1] |
| Vine mealybug | A different genus (Planococcus ficus) that can have many more generations a year, also overwinters on roots, and spreads more readily than grape mealybug.[2][1] |
Where it lives
It is found in all three Pacific Northwest states, where it is more common in vineyards than vine or Gill's mealybug, and it is a primary mealybug of concern in North Coast and San Joaquin Valley vineyards in California.[2][1]
Biology and life cycle
It spends the winter as eggs or first-stage crawlers in cottony egg sacs under loose bark, in bark cracks and in the cordons or upper trunk of grapevines.[1][3]
Crawlers emerge in spring as buds swell, feed at the bases of buds and spurs, and move onto new shoots and leaves when buds open. Once settled they become progressively harder to kill.[3][1]
In California vineyards, the overwintered brood matures from mid-May to early June; most females go back to the old wood to lay eggs, which hatch from mid-June to July, and the new crawlers move out to feed on fruit and foliage in late June or early July. In the Northwest, first-generation nymphs mature in late June and July.[1][3]
Adult males appear first, mate and die; females release a pheromone to attract them. Mated females move to sheltered spots, lay eggs and die in the egg sac.[3]
There are one or two generations a year, depending on location. Second-generation females appear in late summer and early fall; some lay eggs in fruit clusters, but most return to the old wood to lay the overwintering eggs. On pear, nymphs sometimes settle at the stem end or in the calyx of the fruit.[2][1][3]
Damage and signs
- In vineyards it contaminates grape clusters with cottony egg sacs, nymphs, adults and honeydew, often coated with black sooty mold, and can make fruit unsalable. Varieties whose clusters hang close to the base of the shoot, touching old wood, suffer most.[1][2]
- Grape and vine mealybugs can spread grapevine leafroll virus within and between vineyards, and the virus can reduce yield and fruit quality.[2][1]
- On pears, honeydew dripping onto fruit grows sooty mold that leaves a coarse black russet scattered over the skin, and mealybugs in the calyx can lead to rot in storage.[3]
Health risk
It is a plant pest; none of the sources mention any risk to people or pets.[1][2][3]
Control
Prevention
Train vines so clusters hang freely and do not touch the wood. To keep mealybugs and leafroll virus from spreading, restrict movement of fruit and handle grape pomace properly.[1][2]
Find infestations early: peel back thin bark on spurs and loose bark on canes in late winter to look for crawlers, check spur bases for mature females in late May and early June, and watch for honeydew, sooty mold and ants on the vines. Pheromone traps catch the males, which fly twice a year.[1][2]
Biological control
At least five species of parasitic wasps attack grape mealybug in California, and lady beetles such as the mealybug destroyer, predatory midges, lacewings, minute pirate bugs and spiders also help. Parasitized mealybugs show several tiny emergence holes under a hand lens. Avoid broad-spectrum and other disruptive insecticides that kill these natural enemies.[1][2]
Control honeydew-seeking ants, which protect mealybugs from their enemies. In vineyards, tillage, ant baits or a cover crop of common vetch, whose nectaries lure gray field ants off the vines, can reduce ant tending.[1]
Pesticides
Sprays work best on crawlers and young nymphs, so timing matters; once mealybugs are inside closed clusters, foliar sprays are not effective. For home grapes, the PNW handbook lists options including horticultural oil, insecticidal soap, neem oil, spinosad and pyrethrins.[1][2]
Common questions
- What is the cottony material on my grape clusters?
- It may be grape mealybug egg sacs mixed with the insects and their honeydew, often with black sooty mold growing on it.[1][2]
- How do I tell grape mealybug from obscure mealybug?
- Gently probe a female with a pin: reddish orange fluid points to grape mealybug, clear fluid to obscure mealybug. Seeing only one or two life stages at once also points to grape mealybug.[1]
- When should I spray?
- Target the crawlers: in late winter and spring as they leave the bark, or in summer soon after the next eggs hatch. Sprays do little once mealybugs are hidden in closed clusters.[1][2]
Sources
- University of California Statewide IPM Program, “Grape Pest Management Guidelines: Mealybugs (Pseudococcus).” ipm.ucanr.edu/agriculture/grape/mealybugs-pseudococcus/ (accessed 2026-11-09)
- Pacific Northwest Pest Management Handbooks (Oregon State University, Washington State University and University of Idaho Extension), “Grape-Mealybug (PNW Insect Management Handbook, small fruit).” pnwhandbooks.org/insect/small-fruit/grape/grape-mealybug (accessed 2026-11-09)
- Pacific Northwest Pest Management Handbooks (Oregon State University, Washington State University and University of Idaho Extension), “Pear-Grape mealybug (PNW Insect Management Handbook, tree fruit).” pnwhandbooks.org/insect/tree-fruit/pear/pear-grape-mealybug (accessed 2026-11-09)
- iNaturalist, “Pseudococcus maritimus taxon page (order and family).” www.inaturalist.org/taxa/967427 (accessed 2026-11-09)