Pests & diseases › Japanese Beetles
Japanese Beetles
Metallic green-and-copper beetles. Skeletonize leaves of beans, grapes, raspberries, basil and 300+ other plants.
Symptoms
- Lacy skeletonized leaves — only veins remaining
- Beetles in mating clusters on damaged leaves
- Feeding scars on fruit
- Worst in late June–August
Lifecycle
Adults active June–August. Larvae (white C-shaped grubs) feed on lawn roots, fly as adults the next year.
What to do
- Hand pick early morning — knock into soapy water bucket
- Milky spore (Paenibacillus popilliae) treatment of lawns kills the grubs — multi-year control
- Beneficial nematodes (Heterorhabditis bacteriophora) on lawns
- Neem oil deters feeding
If it's bad
- Carbaryl, pyrethrin (avoid spraying flowering plants where bees forage)
Stop it coming back
- AVOID pheromone traps — they attract more beetles than they catch unless placed far from your garden
- Resistant plants: lilac, magnolia, dogwood
- Treat lawn grubs in late summer with milky spore or nematodes
Crops it goes for
Plan the plot, track every sowing, cook the harvest
Sowing reminders and harvest forecasts for your own frost dates, the Seed Tin, Scan Centre for any label or packet, and the Potty Mouth Garden Club. Free to start.