The Green June Beetle (Cotinus nitida) is a large, stocky insect known for its distinct metallic green coloration and a buzzing flight pattern often heard during the summer months. This insect undergoes a complete metamorphosis, with its diet shifting drastically between the larval and adult stages. The adult beetle is active above ground, while the larval stage, commonly known as a white grub, spends nearly all its time feeding beneath the soil surface. Understanding the specific food sources consumed during each stage is helpful for identifying its presence.
The Diet of the Adult Beetle
Adult Green June Beetles are strongly attracted to sweet, readily accessible sources of nutrition, primarily seeking out sugary liquids. Their diet includes a variety of soft, ripe, or damaged fruits, such as peaches, figs, grapes, apples, and berries.
These beetles are sometimes called “fig-eaters” due to their particular fondness for that fruit when it is nearing maturity. They generally feed on fruit that has already been damaged or that is overripe, making the sugary pulp easily reachable.
Beyond fruit, adult beetles also consume other plant-based sweets, including tree sap and flower nectar. They may cluster around weeping wounds on trees, feeding on the fermenting exudate that flows out. They are also known to feed on flower pollen found on open blossoms. This preference for soft material and sweet fluids reflects their feeding apparatus, which is adapted for consuming easily processed food sources.
The Diet of the Larval Stage (Grubs)
The diet of the larval Green June Beetle, or grub, is distinctly different from that of the adult, focusing primarily on decaying organic matter within the soil. These grubs are important decomposers, feeding heavily on materials like rotting wood, compost, leaf mold, heavy thatch, and well-rotted manure. This dietary preference means the grubs thrive in areas with high organic content, such as mulched garden beds and pastures.
A key distinction between Green June Beetle grubs and other turf-damaging white grubs is their limited consumption of healthy, living grass roots. While some root feeding can occur, the majority of their diet consists of dead and decaying plant material. They are largely considered secondary pests in turfgrass because their primary role is processing organic debris.
Feeding Behavior and Resulting Damage
The feeding habits of the adult beetles often lead to visible damage to fruit harvests, especially in mid to late summer. Adults chew irregular holes into soft fruits, frequently entering through existing breaks in the skin. Multiple beetles may congregate on a single piece of fruit, sometimes burying themselves entirely within a ripe peach. Their feeding activity, combined with their excrement, can ruin fruit even if the physical damage is not extensive.
The grubs cause most of their damage through characteristic behavior and movement rather than direct feeding on live plants. The larvae are unique among common lawn grubs for crawling on their backs, using stiff hairs for traction. They actively move through the topsoil, constructing vertical tunnels that open to the surface. This tunneling and burrowing activity results in small mounds of soil, often called “turrets” or “castings,” which resemble earthworm mounds but are larger. The constant disruption of the soil and the tunneling can physically uproot small seedlings or loosen the turf, causing damage to lawns and gardens. This mechanical damage from their movement, rather than root consumption, is the primary reason the grubs are viewed as pests in manicured turf areas.