The common “June bug” is a general term used to describe various species of scarab beetles, predominantly those belonging to the genus Phyllophaga. These reddish-brown insects emerge from the soil in late spring and early summer. While their brief adult life above ground may seem like a minor nuisance, their full life cycle determines the extent of garden harm. The insect’s development stages present two distinct periods of potential damage: one minor and one that can cause significant destruction to lawns and plant root systems.
Identifying the Garden Threat
The adult June bug, sometimes called a May beetle, is a stout, oval-shaped insect typically measuring between one-half to one inch long. Its body is usually dull reddish-brown or mahogany. It is known for its clumsy, buzzing flight, especially around outdoor lights at night. Observing these beetles flying after dusk confirms the presence of the pest, though the adult stage is not the primary source of garden destruction.
The real threat comes from the larval form, commonly known as a white grub. These grubs are easily identified by their creamy white, soft body, a distinct brown head capsule, and the characteristic C-shape they assume when unearthed. A mature white grub can grow up to one and a half inches in length and resides underground, often just beneath the turf surface. Finding these larvae when digging is a definitive sign that the destructive life stage is active.
The Dual Threat: Life Cycle and Damage
The June bug life cycle is a multi-year process, with most of that time spent beneath the soil as a larva. Adult beetles emerge primarily to mate, and their feeding activity is minor, consisting of chewing small holes in the leaves and foliage of certain trees and shrubs. This adult feeding is considered cosmetic and rarely causes lasting harm to established plants.
The larval stage is responsible for the most significant garden injury because the grubs feed directly on plant roots. Once the eggs hatch in mid-to-late summer, the small grubs consume the fine roots of turfgrass and garden plants. This subterranean root-feeding prevents the plants from absorbing necessary water and nutrients, causing above-ground symptoms that mimic drought stress.
The most noticeable signs of severe grub infestation are irregular patches of yellowing or wilting grass that fail to green up after watering. In areas with high grub populations, the turf may feel spongy and can be rolled back like a carpet because the grubs have severed the root system entirely. This peak destructive feeding occurs in the late summer and fall when the grubs are actively growing, and again in the early spring before they pupate.
The larval stage typically lasts one to three years, depending on the species and regional climate, allowing the population to cause continuous damage. The grubs migrate deeper into the soil to overwinter, returning closer to the surface to feed as temperatures warm. This extended time spent underground as a root-feeder is why the June bug is considered a significant garden pest.
Targeted Management Strategies
Effective control requires targeting the specific life stage causing the problem, focusing management efforts underground against the grubs. Preventative chemical treatments typically involve insecticides containing active ingredients like imidacloprid or chlorantraniliprole. These products are most effective when applied in late spring or early summer, before the eggs hatch, to kill the newly hatched, smaller grubs.
Curative chemical applications, using fast-acting ingredients such as carbaryl or trichlorfon, are necessary when a large, active grub population is present. This type of insecticide works best when applied in late summer or early fall, when the grubs are actively feeding close to the soil surface. Proper timing is important for all chemical controls to ensure the active ingredient reaches the feeding zone.
Biological Controls
Biological controls offer a less toxic approach to managing grub populations. Beneficial nematodes, which are microscopic roundworms, can be applied to the soil to seek out and kill the grub larvae by releasing bacteria inside them. Another long-term biological option is milky spore, a naturally occurring bacterium that specifically targets certain grub species and builds up in the soil over several years.
Cultural Practices
Cultural practices aid in reducing the garden’s attractiveness to egg-laying adults and improve plant resilience. Maintaining a healthy lawn through proper irrigation and mowing at a slightly higher height encourages a robust root system that can withstand some feeding. Reducing outdoor lighting at night during the beetles’ flight period can also prevent adult females from being attracted to the area and laying eggs.