# Grape berry moth

- URL: https://backyardgrapes.com/diseases/grape-berry-moth/
- Scientific name: Paralobesia viteana
- Category: Insect / pest
- Affects: Fruit clusters
- Severity: high
- Favored by: North America; overwinters as pupae in leaf litter; several generations per season.
- Easily confused with: European grapevine moth, Botrytis bunch rot (grey mould)

**Summary:** Caterpillars that web and bore into berries, opening the door to bunch rots.

**What to look for:**
- Small caterpillars webbing berries together within the cluster.
- Reddish-purple entry spots on green berries; hollowed or prematurely coloured fruit.
- Webbing and dark frass among the berries.
- Later broods tunnel ripening fruit, triggering Botrytis and sour rot.

**Treatment — Cultural / prevention:**
- Rake up and remove leaf litter in autumn, where pupae overwinter.
- Keep the canopy open; berry moth pressure is often worst on shaded vineyard edges near woods.
- Remove infested, webbed clusters to reduce the next generation.

**Treatment — Organic / low-toxicity:**
- Bacillus thuringiensis (Bt) or spinosad sprayed to coincide with egg hatch.
- Pheromone mating disruption where the vineyard is large enough.

**Treatment — Conventional (chemical):**
- Insecticides timed to egg hatch (trap/degree-day models) around bloom and for later broods.

Grape berry moth is the main cluster-feeding caterpillar of eastern North American vines.
The moths lay eggs on and around the clusters; the larvae web berries together and bore
inside, hollowing them out. Early broods hit the developing berries, and later broods
attack ripening fruit — and every entry hole is a doorway for Botrytis and sour rot, so
the caterpillar often causes more loss through the rots that follow than through its own
feeding.

Because it overwinters as pupae in fallen leaves, autumn clean-up along wooded edges helps.
For active infestations, the key is timing: Bt, spinosad, or a conventional insecticide
works best applied to coincide with egg hatch, which growers track with pheromone traps
and degree-day models. It's easy to confuse with the European grapevine moth, its
Old-World counterpart, which does much the same damage.

**Image credits:**
- Vine moth (Eupoecilia ambiguella) — [Koppert](https://www.koppert.com/plant-pests/caterpillars/grape-berry-moth/)
- Webbing and frass with discoloration of berries from grape berry moth larva — [Photo: Rufus Isaacs, Michigan State University IPM](https://www.canr.msu.edu/ipm/diseases/grape_berry_moth)

**Sources:**
- [Grape Berry Moth](https://extension.umd.edu/resource/grape-berry-moth) — University of Maryland Extension
- [Grape berry moth, Paralobesia viteana (Clemens)](https://www.virginiafruit.ento.vt.edu/GBM.html) — Virginia Tech / Virginia Cooperative Extension (Virginia Fruit Web Site)
- [ENTFACT-221: Grape Berry Moth](https://entomology.mgcafe.uky.edu/ef221) — University of Kentucky Entomology