The Green June Beetle (Cotinis nitida) often causes alarm due to its large size and loud, buzzing flight, leading many people to worry about potential stings or property damage. This scarab beetle is common throughout the eastern United States and is frequently mistaken for a more aggressive pest or a stinging insect. Understanding its two life stages—the adult beetle and the larval grub—reveals that while they can be a nuisance, the danger is often exaggerated.
Identifying the Green June Beetle
The adult Green June Beetle is a large insect, typically measuring between three-quarters of an inch and one inch in length. Its body is distinctively colored, featuring a velvety green to dull brown upper surface with lengthwise stripes of green, while the underside often displays a shiny metallic green or gold sheen. The wing covers, or elytra, also frequently have yellow-orange margins.
A unique characteristic is its flight pattern, often described as clumsy or erratic. Unlike many beetles that fly with their wings extended below the elytra, the Green June Beetle flies with its wings exposed, resulting in a low, fast, and noticeably loud, buzzing sound. They are day-active fliers, commonly seen during mid-to-late summer. This helps distinguish them from other, more destructive grubs, such as those from the Japanese Beetle.
Harm Posed by Adult Beetles
The safety concern from the buzzing adult beetle is unfounded, as they are non-aggressive and lack the ability to sting. The loud noise they make while flying is sometimes compared to that of a bumblebee, contributing to the public’s perception of them as a threat. While they may occasionally bump into people due to their clumsy flight, they do not deliberately attack humans or pets.
Any physical contact is usually limited to a defensive pinch if they are handled, but their mouthparts are not strong enough to break human skin. The primary damage caused by adult beetles is to fruit, not foliage. They prefer to feed on overripe, fermenting fruits like peaches, figs, and grapes, or on tree sap flows.
Their mouthparts are blunt, meaning they are poor at chewing healthy, sound fruit. Instead, they often take advantage of fruit that is already damaged by other pests or natural splitting. This feeding habit can be a problem in orchards, but they are not considered a major threat to healthy lawns or garden plants.
Damage Caused by Larval Grubs
The larval stage, commonly known as a white grub, is where the potential for property damage lies. Green June Beetle grubs are large, growing up to two inches long, and are distinct because of their unique movement. They possess stiff hairs on their backs that allow them to crawl on their backs rather than using their small legs, resulting in a rapid, undulating motion.
Crucially, Green June Beetle grubs are primarily saprophagous, meaning they feed mainly on decaying organic matter, such as compost, mulch, and thatch. This is a significant distinction from truly destructive grubs, which are rhizophagous and feed directly on grass roots. Because they rarely consume enough turf roots to cause significant thinning of the lawn, they are classified mostly as nuisance pests.
The actual damage to lawns comes from their burrowing and tunneling behavior, which disrupts the turf. Grubs dig vertical tunnels, often six to twelve inches deep, pushing soil up to the surface at night and creating small, visible mounds. This activity loosens the soil and can dislodge plants, interfering with mowing and creating an unsightly appearance. Areas with high organic matter, such as those treated with compost or manure-based fertilizers, are particularly attractive to egg-laying females.
Managing Their Presence
Since the Green June Beetle’s impact is often more of a nuisance than a destructive force, management typically begins with cultural controls. Reducing the attractants for egg-laying females is a sensible first step. This includes managing excessive thatch layers and minimizing the use of manure-based fertilizers or compost topdressings in the spring and summer.
For adult beetles, simple physical removal can be effective. Removing overripe or damaged fruit from trees and the ground reduces the number of adults congregating in an area. For the grubs, if the infestation is severe enough to warrant intervention, targeted non-chemical methods like applying beneficial nematodes can control the population.
In cases of a heavy infestation, chemical controls are available, but timing is important. Curative insecticides, such as products containing carbaryl, are applied when grubs are actively feeding near the surface in late summer or early fall. Because the grubs come to the surface at night, contact-type insecticides should be left on the turf surface and not immediately watered in.