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How to identify it
- Adult females are flat and oval, about 0.08 to 0.2 inch (2 to 5 mm) long, with pinkish gray bodies covered by long white wax filaments up to twice the body length.[1]
- Two rows of sparse wax along the back break up the filaments and give the look of stripes.[1]
- Nymphs and adult females have no wax filaments around the edge of the body and carry two broad white tails, which sets them apart from other mealybugs found on grapes.[1]
- Males are rarely seen: they are tiny, winged and have no wax. The orange crawlers look like those of other mealybugs.[1]
Look-alikes
| Look-alike | How to tell them apart |
|---|---|
| Grape mealybug and other vine mealybugs | Gill's mealybug is told apart by its abundance of glassy wax filaments, the lack of filaments around the sides of the body, and its two broad white tails.[1] |
Where it lives
Known as a pest in California: on wine grapes in the Sierra foothills (El Dorado County) and the North Coast (Lake County), and on pistachios across most of the state's pistachio-growing regions after it was first found near Tulare in the late 1990s. It has rarely been found in San Joaquin Valley vineyards or other California wine grape regions.[1][4]
Biology and life cycle
Females give birth to live crawlers, which stay under the mother for a short time before moving out to the leaves to feed. Nymphs molt through three stages, adding more wax each time.[1]
On grapes in the Sierra foothills it overwinters as nymphs under the bark of the trunk and cordons and completes two generations a year, with crawlers appearing in June to early July and again in late August to September.[1][2]
In a Tulare County pistachio orchard it overwintered as small nymphs and completed three generations a year; from June through September most of the population was in the nut clusters.[4]
Honeydew is most noticeable as numbers build in fall, and ants feeding on it can be a sign of an infestation.[1]
Damage and signs
- It contaminates grape clusters with its bodies and honeydew, making fruit unmarketable. In untreated vineyard plots, 7% to 29% of sampled clusters were rated unmarketable at harvest in the second year.[1]
- It transmits grapevine leafroll-associated viruses: in experiments it picked up four types and passed GLRaV-3 and GLRaV-4LV to healthy vines. These viruses can delay ripening and reduce fruit quality and yield.[3][1]
- Researchers describe it as a serious new pest of California pistachios, and it has also been recorded as a pest of almond and ornamental plants.[4][2]
Health risk
The sources describe it only as a crop pest; none mentions any risk to people or pets.[1][2]
Control
Prevention
It is hard to find, and no traps or pheromone lures exist. Look for it at the base of new shoots during shoot thinning in May to early June, flag infested vines, and break open clusters at harvest, focusing on vines with ants.[1]
Sanitation
Control ants, which disrupt biological control of mealybugs.[1]
Biological control
Lady beetles, green lacewings, praying mantises, damsel bugs, snakeflies, spiders and a parasitic wasp (Acerophagus) attack it. Natural enemies are usually too few to control it alone but help over time, especially combined with selective insecticides; leaving a few rows unsprayed gives them a refuge.[1][2]
Pesticides
Treatments are timed to one of the two crawler peaks, starting when crawlers emerge onto the leaves. Lightweight mineral oil smothers crawlers and young nymphs if it contacts them directly, but not the larger waxy stages. UC IPM's treatment table also lists acetamiprid, buprofezin, spirotetramat and thiamethoxam. There is no set treatment threshold.[1]
Common questions
- How do I recognize Gill's mealybug on grapes?
- Look for pinkish gray mealybugs covered in long glassy wax threads, with no filaments around the sides of the body and two broad white tails.[1]
- Does Gill's mealybug spread grapevine leafroll?
- Yes. In transmission experiments it passed GLRaV-3 and GLRaV-4LV to healthy grapevines.[3]
- When should Gill's mealybug be treated?
- When the crawlers are out on the leaves, which in the Sierra foothills happens from mid-June to early July and again from late August to September. Larger, waxy mealybugs are protected from oil sprays.[1]
Sources
- University of California Statewide IPM Program, “Gill's Mealybug, UC IPM Pest Management Guidelines: Grape.” ipm.ucanr.edu/agriculture/grape/gills-mealybug/ (accessed 2026-11-09)
- Entomological Society of America (Journal of Economic Entomology), “Seasonal biology of Ferrisia gilli (Hemiptera: Pseudococcidae) in California Sierra foothill vineyards (Wunderlich, Cooper and Daane 2013).” doi.org/10.1603/EC13046 (accessed 2026-11-09)
- Entomological Society of America (Journal of Economic Entomology), “Ferrisia gilli (Hemiptera: Pseudococcidae) transmits grapevine leafroll-associated viruses (Wistrom et al. 2016).” doi.org/10.1093/jee/tow124 (accessed 2026-11-09)
- Entomological Society of America (Journal of Economic Entomology), “Seasonal phenology of Ferrisia gilli (Hemiptera: Pseudococcidae) in commercial pistachios (Haviland, Beede and Daane 2012).” doi.org/10.1603/EC12070 (accessed 2026-11-09)
- iNaturalist, “Ferrisia gilli taxon page (order and family).” www.inaturalist.org/taxa/1480083 (accessed 2026-11-09)