June bugs, commonly referred to as May beetles, are scarab beetles that emerge from the soil in late spring and early summer across North America. They are often announced by their noisy, clumsy flight patterns near outdoor lights. While the adult beetles are largely harmless to people, their life cycle includes a highly destructive underground stage that causes significant damage to lawns and gardens. Understanding the difference between the flying adult and the subterranean larva is the first step in managing their populations.
Identifying the June Bug
The adult June bug is a robust, stout-bodied beetle, measuring about one-half to one inch in length. They possess a hard, shiny exoskeleton that ranges from reddish-brown to a darker chestnut brown. Their name reflects their emergence in large numbers, usually beginning in May and peaking in June.
These beetles are nocturnal, spending their days burrowed in the soil or hidden in foliage and becoming active around dusk. They are strongly attracted to artificial light sources, often seen buzzing erratically and colliding with porch lights during summer evenings. Adult beetles are herbivores, feeding on the leaves of various deciduous trees and shrubs. While they can cause minor defoliation, adult feeding poses a much smaller threat to plant health than their offspring’s activities.
The Underground Life Cycle and Damage
The June bug life cycle is lengthy, with most of the time spent beneath the soil as a larva. After mating, females burrow into the soil to lay eggs near plant roots in late spring or early summer. These eggs hatch into the larval stage, known as white grubs, which are C-shaped with creamy-white bodies and brown head capsules.
The grubs are the damaging stage, feeding voraciously on the fibrous roots of grasses, vegetables, and ornamental plants. This root consumption prevents the lawn from absorbing water and nutrients, leading to irregular brown, wilting patches of grass. In severe infestations, the turf loses its anchoring root system, allowing affected areas to be rolled back easily like a carpet.
The most significant feeding damage occurs during late summer and early fall when the grubs are larger and active near the soil surface. A secondary problem arises because grubs are a food source for predators. Animals such as skunks, raccoons, and birds will dig up the lawn at night to consume the grubs, often causing more visible damage than the grubs themselves.
Effective Population Management
Managing the June bug population requires a dual approach that targets both the flying adults and the subterranean grubs. To reduce the number of egg-laying adults, minimize the use of bright outdoor lights during late spring and early summer evenings, as these lights attract the beetles for mating. For high-value trees or shrubs, physical barriers like fine netting can be placed over the foliage to prevent adult feeding and egg-laying.
The most effective long-term management focuses on the grub stage, and timing is paramount for success. Preventative chemical treatments should be applied in June or July to target the newly hatched, small grubs. Curative chemical applications are applied in September to kill the larger, actively feeding grubs before they burrow deeper for winter.
For a biological option, beneficial nematodes are microscopic worms that parasitize the grubs in the soil. These beneficial organisms should be applied to moist soil in late summer or early fall when the grubs are nearest the surface.
Maintaining a healthy, well-watered lawn and aerating the soil helps the grass tolerate minor grub populations. This cultural practice also makes the area less appealing for adult beetles to lay eggs.