The June bug, also known as the May beetle, belongs to the genus Phyllophaga, which encompasses over 250 species of scarab beetles across North America. The feeding habits of this common insect depend entirely on its stage of development, shifting dramatically between its time above and below ground. Understanding what these insects consume requires separating the diet of the winged adult from that of the subterranean larva.
Adult June Bug Feeding Habits
The adult June bug is the reddish-brown, clumsy beetle that emerges from the soil in late spring and early summer to mate and reproduce. These beetles are primarily nocturnal feeders, spending the daylight hours resting and often burrowing back into the soil before dusk. Their diet focuses on the foliage of various trees and shrubs, making them defoliators in their mature life stage.
Adults use their chewing mouthparts to consume leaves, resulting in ragged edges and skeletonized tissue where only the leaf veins remain. They favor soft, tender leaves over tougher, mature foliage. While large populations can cause visible damage, adult feeding rarely threatens the overall health of a mature plant, as their activity is focused on sustaining reproduction.
The Destructive Larval Diet
The most significant consumption phase occurs underground during the insect’s larval stage, where they are commonly known as white grubs. This C-shaped larva feeds voraciously on plant roots and decaying organic matter. The larval stage is extensive, often lasting between one and four years, with a three-year cycle being common for many species.
Grubs are particularly damaging to turf and lawns, as the fibrous root systems of grasses are a preferred food source. Their feeding severs the roots just below the soil surface, preventing the grass from absorbing water and nutrients. This root damage is often most intense during the second year of the grub’s development when the larvae are largest and require the most sustenance.
The visible effect of this below-ground consumption is the appearance of irregular brown patches of dead grass that resemble drought stress. In areas of severe infestation, the turf loses its anchor to the soil, allowing it to be rolled back like a rug due to the destruction of the root system. This damage is often compounded by mammals like raccoons and skunks digging up the lawn to feed on the protein-rich grubs.
Specific Plant Preferences and Damage
The feeding preferences of June bugs extend across a wide variety of plant life, with certain species being noticeably more vulnerable to damage. Adult beetles demonstrate a clear preference for the leaves of deciduous trees. Common targets include trees like oak, maple, hickory, basswood, elm, and willow.
While they are generalist feeders, adult June bugs will also consume the foliage of fruit trees, such as apple and cherry, and various garden shrubs. The specific species of Phyllophaga present in a region can influence which host plants are most heavily attacked.
The subterranean grubs cause the most concern in cultivated areas by targeting the roots of grasses and certain crops. Lawns planted with fine turf, like Kentucky bluegrass, are highly susceptible to grub damage. Beyond turf, the larvae feed on the roots of young ornamental plants, tree seedlings, and vegetable crops.
Grub Damage to Crops
Root vegetables and garden favorites can suffer significant damage from grubs tunneling and feeding on roots and tubers. These include:
- Potatoes
- Carrots
- Strawberries
- Lettuce