The short answer to whether June bugs eat plants is yes, but the type and severity of the damage depend on the insect’s life stage. The common name “June bug” is applied to several different species of beetles, which complicates the question of plant damage. Adult beetles consume foliage above ground, while their larvae, known as white grubs, cause far more significant harm by feeding on plant roots beneath the soil surface. Understanding this two-part life cycle is the first step toward protecting a garden or lawn.
Clarifying the Identity of “June Bugs”
The term “June Bug” most commonly refers to the May or June beetle, which belongs to the genus Phyllophaga and includes over 900 species of New World scarab beetles. These adult beetles are typically large, measuring between 12 and 35 millimeters, with a reddish-brown or blackish coloration and a robust appearance. Phyllophaga adults are nocturnal, often seen flying toward artificial lights on warm evenings, and they feed on plant leaves and flowers.
Another beetle frequently mistaken for the June bug is the Japanese beetle (Popillia japonica), which causes a different type of damage. The adult Japanese beetle is smaller, about 7/16-inch long, and easily recognized by its metallic green body and copper-brown wing covers. Unlike Phyllophaga species, Japanese beetles are active during the day and are highly aggressive feeders, leading to much more visible destruction in the garden.
Adult Feeding Habits and Plant Damage
Adult Phyllophaga beetles feed on plants, consuming the foliage of various trees and shrubs, including maples, oaks, and willows, generally at night. While large swarms can cause noticeable defoliation, this damage is often considered cosmetic. Healthy, mature trees can typically tolerate the feeding without long-term harm.
The adult Japanese beetle is far more destructive to above-ground plant parts. These beetles feed on over 300 plant species, including roses, grapes, and various fruit trees, during the day. Their feeding involves consuming the soft tissue between the leaf veins, leaving behind a lace-like, skeletonized appearance that can severely stress the plant. They are also known to devour flowers and fruits.
The Destructive Larval Stage
The most significant plant damage associated with the June bug life cycle comes from its larval stage, commonly called a white grub. These creamy-white, C-shaped larvae live entirely underground and grow up to 40 millimeters long, with a distinct reddish-brown head capsule. The grubs feed voraciously on the roots of grasses, small grains, and other garden plants, including potatoes and strawberries.
Grub feeding severs the root system, preventing the plant from absorbing necessary water and nutrients. In lawns, this root destruction first appears as patches of wilted or pale grass that resemble drought stress, often in mid-to-late summer. When feeding is severe, the turf loses its anchorage and can be rolled back like a piece of carpet, exposing the grubs beneath. For many Phyllophaga species, this larval stage requires two to four years in the soil before the beetle matures, meaning the damage can be a recurring problem.
Interrupting the Life Cycle to Reduce Damage
Managing June bug damage is most effectively achieved by targeting the destructive grub stage in the soil. The timing of intervention is important, as newly hatched grubs are more vulnerable to treatment than mature ones. Preventive insecticides containing active ingredients like imidacloprid are often applied in early to mid-summer to kill the young larvae soon after they hatch.
Biological controls offer an alternative method by introducing natural enemies into the soil environment. Beneficial nematodes, such as Heterorhabditis bacteriophora, are microscopic roundworms that parasitize and kill the grubs. Applying these nematodes in late summer or early fall, when grubs are actively feeding near the soil surface, is the optimal window for effectiveness. Cultural practices, like maintaining a healthy lawn with proper watering and mowing, can help the grass withstand moderate grub populations, which are tolerable up to 10 grubs per square foot.