Plant Problem Diagnosis Key / Pests
Japanese beetles
Popillia japonica
Metallic green beetles with copper wing covers that feed in groups in midsummer. The grubs live in turf and eat grass roots.
Signs
- Leaves eaten to a lace of veins.
- Beetles clustered on roses, grapes, beans, raspberries and linden.
- Five white patches of hair along each side of the abdomen.
What favors it
Lawns nearby (where the grubs live) and plants already being fed on, since feeding beetles release scents that draw more.
Prevention
- Treat grubs in nearby turf in late summer when they are young.
- Do not hang pheromone traps near the garden; they draw more beetles than they catch.
- Choose less preferred plants where pressure is heavy.
Crops it shows up on
Roses & ornamentals; Apple, pear & stone fruit; Beans & peas; Hemp & cannabis; Shade & ornamental trees.
Often confused with
Sources
- Japanese beetles in yards and gardensUniversity of Minnesota Extension
- Japanese Beetles on VegetablesUniversity of Maryland Extension
Treatment by crop
Cultural, biological and chemical options in the order to use them, and notes written for each crop.
Identification is free. Treatment is on the Home and Pro plans.
Questions in the key that lead here
- Look the plant over, leaf undersides included. Are insects, mites, slugs, eggs, webbing or droppings on it?
No, only damage or discoloration - Where is the problem?
Leaves - What does the leaf damage look like?
Holes, chewed edges or tunnels - What does the damage look like?
Leaf eaten to a lacy skeleton between the veins
Not a match? Start the key or describe what you see.
More photos
More from university Extension: search Extension pages on japanese beetles, or find a plant diagnostic lab through your state's Extension.
Other pests
- Aphids
- Bagworms
- Bark beetles of pine and spruce
- Broad mites and cyclamen mites
- Caterpillars
- Cicada and twig-cutting damage
- Colorado potato beetle
- Cucumber beetles
- Cutworms
- Elm leaf beetle
- Emerald ash borer
- Flea beetles
- Fungus gnats
- Galls on leaves and twigs
- Hemlock woolly adelgid
- Lace bugs
- Leafminers
- Mealybugs
- Pine sawflies
- Root aphids
- Root-knot nematodes
- Russet mites
- Sapsucker damage
- Scale insects
- Shore flies
- Slugs and snails
- Spider mites
- Spongy moth (gypsy moth)
- Spotted lanternfly
- Squash bugs and stink bugs
- Squash vine borer
- Tent caterpillars and fall webworm
- Thrips
- Whiteflies
- Wood borers