# Grape mealybug

- URL: https://backyardgrapes.com/diseases/grape-mealybug/
- Scientific name: Pseudococcus maritimus
- Category: Insect / pest
- Affects: Leaves, Shoots & canes, Fruit clusters
- Severity: moderate
- Favored by: Overwinter as eggs/crawlers under bark; warm seasons; strongly ant-associated.
- Easily confused with: Spotted lanternfly, Grapevine leafroll

**Summary:** Soft, waxy sap-suckers that foul clusters with honeydew — and spread leafroll virus.

**What to look for:**
- White, cottony, waxy insects tucked under loose bark, in leaf axils, and inside clusters.
- Sticky honeydew on leaves and fruit that turns black with sooty mould.
- Ants running up and down the vine, tending the colonies.
- Contaminated, unmarketable clusters; the insects also transmit grapevine leafroll virus.

**Treatment — Cultural / prevention:**
- Control ants, which protect mealybugs from their natural enemies.
- Remove loose, shaggy bark where they shelter and lay eggs.
- Remove heavily infested clusters; avoid moving infested material to clean vines.

**Treatment — Organic / low-toxicity:**
- Horticultural oil or insecticidal soap aimed at exposed crawlers.
- Conserve or release natural enemies (the mealybug destroyer beetle, parasitic wasps).

**Treatment — Conventional (chemical):**
- Systemic insecticides timed to the vulnerable crawler stage where pressure is high.

Grape mealybugs are small, soft insects wrapped in white waxy fluff, usually found hiding
under bark, in leaf axils, and deep in the clusters. They suck sap and excrete sticky
honeydew that coats the fruit and grows black sooty mould, spoiling the crop even at
modest numbers. Ants love the honeydew and will actively defend the colonies, so an ant
problem and a mealybug problem tend to go together.

The bigger concern is that mealybugs transmit grapevine leafroll virus as they move and
feed, so a mealybug infestation can seed a lasting virus problem. Control works best when
it targets the exposed crawler stage, knocks back the tending ants, and removes the loose
bark the insects hide under — while protecting the beetles and parasitic wasps that keep
them in check.

**Image credits:**
- Vine mealybugs on a grapevine — [Center for Invasive Species Research (CISR), UC Riverside](https://cisr.ucr.edu/invasive-species/vine-mealybug)
- Grape mealybug — [Photo: Rufus Isaacs, MSU, Michigan State University Extension](https://www.canr.msu.edu/news/it-s-time-to-consider-grape-mealybug-control)

**Sources:**
- [Mealybugs (Pseudococcus) (Grape Pest Management Guidelines)](https://ipm.ucanr.edu/agriculture/grape/mealybugs-pseudococcus/) — UC IPM
- [Distribution and Monitoring of Grape Mealybug: A Key Vector of Grapevine Leafroll Disease in Oregon](https://extension.oregonstate.edu/catalog/em-9092-distribution-monitoring-grape-mealybug-key-vector-grapevine-leafroll-disease-oregon) — Oregon State University Extension Service
- [Grape-Mealybug](https://pnwhandbooks.org/insect/small-fruit/grape/grape-mealybug) — Pacific Northwest Pest Management Handbooks (OSU / WSU / U. Idaho)