The Japanese beetle spends about 10 months of the year in the ground, in the form of a white grub. Several other related scarab beetles have similar grub larvae. Often this feeding goes unnoticed until the plants fail to make proper growth, or die. When grubs are numerous, they can cause serious injury to turf. Adult Japanese beetles will feed on more than 275 different plants.
Damage varies from slight to severe.
Wild blackberry, grape, elderberry, smartweed, and roses often attract masses of adults. These plants often abound in or near sites optimal for oviposition and larval survival. The beetles often congregate and feed on flowers, foliage, and fruit of plants and trees exposed to bright sunlight. Beetles feeding on leaves usually chew out the tissue between the veins, leaving a lacey skeleton. A badly attacked tree or shrub may lose most of its leaves in a short time.