# Japanese beetle

- URL: https://backyardgrapes.com/diseases/japanese-beetle/
- Scientific name: Popillia japonica
- Category: Insect / pest
- Affects: Leaves
- Severity: moderate
- Favored by: Adults active in warm early/mid summer; grubs develop in nearby turf.

**Summary:** Metallic beetles that skeletonise leaves, chewing the tissue between the veins into lace.

**What to look for:**
- Leaves chewed into lace — only the veins left ("skeletonised").
- Shiny metallic-green beetles with copper wing covers, feeding in groups on top of the canopy.
- Damage worst in early-to-mid summer, often on sun-exposed upper leaves.
- Heavy feeding on young vines can stunt growth; established vines usually tolerate it.

**Treatment — Cultural / prevention:**
- Hand-pick beetles into soapy water in the cool of early morning.
- Protect young vines with fine netting during peak flights.
- Avoid pheromone "beetle traps" near vines — they attract more than they catch.

**Treatment — Organic / low-toxicity:**
- Neem oil as a feeding deterrent; kaolin clay as a protective film on foliage.
- Encourage the mid-summer flight to pass — mature vines rarely need rescue.

**Treatment — Conventional (chemical):**
- Labelled contact insecticides for severe outbreaks on young or heavily hit vines.

Japanese beetles (*Popillia japonica*) are a leaf-eating pest rather than a disease.
The adults feed in groups on warm, sunny days and chew the soft tissue between leaf
veins, leaving a lacy skeleton. The larvae are white grubs that live in nearby lawns.

For most established vines the damage looks alarming but is cosmetic — the vine has
plenty of leaf area to spare and the beetles are only around for a few weeks.
Hand-picking in the early morning (when they are sluggish) is surprisingly effective
for a home grower, and young vines are worth protecting with netting during the peak.

**Image credits:**
- Japanese beetles feeding on a skeletonised grape leaf — [PlantVillage (Penn State)](https://plantvillage.psu.edu/posts/5119-grape-what-to-do-against-japanese-beetles-on-grapes)
- Japanese beetles feeding on grape leaves — [Purdue University Facts for Fancy Fruit](https://fff.hort.purdue.edu/article/japanese-beetles-on-grapes-and-berries/)
- Japanese beetles feeding on grape leaves — [Photo: Christelle Guédot, UW-Madison, Wisconsin Fruit (University of Wisconsin–Madison Extension)](https://fruit.wisc.edu/2020/07/09/managing-japanese-beetles/)

**Sources:**
- [How Do I Control Japanese Beetles on My Grapevines?](https://yardandgarden.extension.iastate.edu/faq/how-do-i-control-japanese-beetles-my-grapevines) — Iowa State University Extension and Outreach
- [Japanese Beetle, Popillia japonica Newman, on Grape](https://www.virginiafruit.ento.vt.edu/JBGrape.html) — Virginia Tech / Virginia Cooperative Extension
- [Japanese Beetle Management in Vineyards](https://viticulture.uga.edu/2017/06/japanese-beetle-management-in-vineyards/) — University of Georgia Extension Viticulture
- [Managing Japanese Beetle in Fruit Crops: Variety Preference in Raspberry and Wine Grapes](https://blog-fruit-vegetable-ipm.extension.umn.edu/2018/12/managing-japanese-beetle-in-fruit-crops.html) — University of Minnesota Extension