What Do Japanese Beetles Eat? Roses, Grapes and Lindens
What Do Japanese Beetles Eat? Adult Popillia japonica feed on the leaves, flowers, and fruit of more than 300 plant species, with roses, grapes, and linden trees among their top targets. The species was first found in the United States in August 1916, near a nursery outside Riverton, New Jersey, and has since spread across most of the Eastern and Central states.
What Adult Japanese Beetles Look Like
Adults measure about 1/2 inch long, with a metallic green body and copper or bronze wing covers. A row of small white tufts of hair lines each side of the abdomen, just below the wing covers, which separates them from similar-looking metallic beetles. Adults typically emerge from the soil in late June and stay active into August, with each beetle living roughly 30 to 45 days.
Four Life Stages, One Destructive One
Japanese beetles pass through egg, larva, pupa, and adult stages over roughly one year.
- Egg: Females burrow a few inches into turf soil during summer to lay eggs, often in the same lawns and fields where they fed as adults.
- Larva (grub): The C-shaped white grubs feed on turfgrass roots through fall, overwinter deeper in the soil, then resume feeding near the surface in spring.
- Pupa: Grubs pupate in the soil in late spring before emerging as adults.
- Adult: This is the only stage that damages foliage, flowers, and fruit above ground.
Foliage, Flowers, and Fruit They Target
Favorite Plants
Adults show a strong preference for:
- Roses
- Grapevines
- Linden trees
- Japanese maple and other maples
- Crabapple and apple
- Birch
- Cherry and other stone fruit
- Raspberries
Beyond foliage, beetles feed on flower petals and reproductive parts, and they’ll chew through the skin of ripening grapes, raspberries, peaches, and strawberries.
How the Damage Looks
Adult beetles eat the tissue between a leaf’s veins and leave the veins intact, a pattern called skeletonization that gives damaged foliage a lace-like appearance. Because beetles are drawn to plants where others are already feeding, they cluster in groups, which can strip a rosebush or grapevine of leaves within days. They favor the youngest, most sun-exposed leaves near the top of a plant, working downward as those leaves are consumed.
Why Diet Quality Matters to Females
Feeding is tied directly to reproduction. Females need the nutrients from leaf and flower tissue to develop viable eggs, plus the energy reserves that flight and mating require. Beetles are not indiscriminate: plant age, leaf chemistry, and how much a plant has already been damaged all influence which plants draw the largest groups.
How Feeding Shifts Over the Season
- Late June: Adults emerge and seek out early foliage and flowers, often starting on plants near where they pupated.
- July: Emergence peaks, beetle numbers are highest, and feeding pressure on roses, grapes, and shade trees is most intense.
- August: Numbers decline as the adult generation ages out, and feeding tapers off by month’s end.
What Sustained Feeding Does to Plants
A single beetle does limited harm, but large groups can defoliate a shrub or small tree in a matter of days. Repeated heavy defoliation over several seasons stresses woody plants by cutting off photosynthesis, which can stunt growth and, in already-weakened trees, contribute to dieback. Grape growers and rose nurseries often report the sharpest economic losses, since both fruit skin and flower petals show damage that lowers market value even when the plant itself survives.
Reducing Feeding Damage
Plant Choices
Red maple, boxwood, holly, and most conifers are rarely touched, so working them into a landscape reduces the food available near more vulnerable plants like roses and lindens.
Physical Removal
Handpicking beetles into a container of soapy water in the early morning, when cool temperatures make them sluggish, keeps small infestations from growing into large feeding aggregations.
Traps
Pheromone traps draw in more beetles than they capture, often increasing damage on nearby plants, so they work best placed well away from anything worth protecting rather than next to it.
Insecticides
Contact insecticides protect foliage during peak adult activity, while systemic products and grub-targeted treatments applied to turf address the larval stage before it becomes next year’s adult population.
Timing Control Around the Feeding Calendar
Because adults do all the plant damage and grubs do all the turf damage, control timing depends on the target: treat turf for grubs in late summer while they’re still feeding near the surface, and protect high-value plants with handpicking or contact insecticides during the July emergence peak when feeding pressure is highest.
