You're relaxing with a drink on your porch when, all of a sudden, you're hit by a large flying insect. You look down and see that the culprit was a beetle—more specifically, a June bug. These beetles are easily recognizable: 1/2- to 1-inch-long reddish-brown bugs with wings that form a hard shell when the insect isn't in flight. The beetles themselves don't do any harm to people, though the sticky legs can give you a shiver if the bug clings to you, and the sensation of stepping on one is decidedly unpleasant.
Harmless though the beetles are to people, it's a different matter when it comes to a lawn or landscape. June bugs (also known as June beetles or May bugs, in some areas) are the adult phase of the various species of insects in the Phyllophaga genus. The insect most associated with the common name of "June bug" is Phyllophaga longispina, although there are several other species also known by that name.
While the adult flying beetles do cause some damage to plants by feeding on the leaves and stems, the real problem lies in the immature larval phase of these insects. Known as white grubs, these larvae can wreak serious damage on the roots of lawn turfgrasses and other plants. In addition to P. longispina, a number of other common beetles produce white grubs in their larval stage, including Japanese beetles (Popillia japonica). Fortunately, all of these beetles can be handled in much the same way.
The Life Cycle of a June Bug
Adult June bugs lay 75 to 100 eggs underground in early to midsummer. After about 18 days, larvae emerge from the eggs. The larvae are legged worms about 1 inch long with brown heads, and it is during this phase that the insect can be extremely damaging. Depending on the species, the grubs can spend one to three years underground, chewing plant roots as they precede through three molt phases. During the overwinter periods, the grubs burrow deep into the soil and hibernate before becoming active again in the spring. At the final transformation of the larval stage, the grubs form pupae that will hatch into new adult beetles the following spring as the cycle repeats itself.
The annoying flying beetles you see on summer evenings, then, are only the tip of the iceberg. Where you see adult beetles, eggs and root-destroying grubs are soon to follow. Depending on the species, the time from egg to grub to pupa to adult can take one to three years. The real reason to rid your yard of June bugs is not just to make your evening recreation more pleasant but to save your lawn and garden from grubs.
Signs of June Bugs and Their Grubs
There are several red flags that indicate you may have a problem either with adult June bugs or their larvae:
- You witness large flying beetles on summer evenings after dark. June bugs are nocturnal insects, and they become active after the sun sets on summer evenings.
- You have spreading brown patches on your lawn. This is a sign that underground grubs are likely feeding on the roots of turfgrass plants. Large patches of dying grass may be so loosened from the severed roots that you can lift them up by hand.
- Small holes are being dug in your lawn overnight. These holes are often made by skunks, raccoons, or other carnivorous animals searching for grubs to eat. In some regions, armadillos are prodigious eaters of grubs.
- You have a mole problem. Moles also eat grubs, so, if you have an issue with moles, the source of it may be a grub problem.
- Plant leaves have ragged holes. The adult beetles will feed on above-ground plants. Japanese beetle damage can be especially harmful.
Monitor your landscape for such signs, and follow up upon their detection by confirming the presence of these insects. For confirmation that grubs are present, simply dig up some sod in your lawn, and inspect the soil for grayish-white, caterpillar-like bugs that curl up into a "C" shape when disturbed. For confirmation that the adults are present, walk your landscape faithfully, and inspect the leaves of your plants for beetles.
5 Ways to Get Rid of June Bugs
Trap Adult Insects
Not all June bug infestations are regarded as major enough to require serious remedies. Experts suggest that an otherwise healthy lawn can support as many as five to 10 grubs per square foot—the number of grubs will be evident if you dig up a 1-square-foot patch of turf.
This number of grubs indicates you will probably face a few adult beetles cruising around the nighttime landscape come the following summer, but these can be trapped with a mixture of 1/2 cup molasses and 1/2 cup water placed in a narrow-necked container. There is also a variety of commercial beetle traps available for purchase that do much the same thing: lure and trap beetles in a container holding a sweet concoction.
Trapping adults will stop the reproduction cycle. But if you have larger numbers of grubs, trapping adults won't be sufficient to control the population.
Apply Beneficial Nematodes
Nematodes are microscopic soil worms that feed on the larvae of various insects. They are increasingly popular as a natural, non-toxic control for various damaging pests. There are many species of nematodes, but for lawn grubs, choose a species such as Heterorhabditis bacteriophora, which will also control Japanese beetle grubs. Nematodes should be applied when the grubs are active and present; in most regions, midsummer to late summer is the ideal time. Applied too early or too late, the application will be wasted.
Mix the nematodes with a garden sprayer, and then apply to a wet lawn in the evening. Immediately water the nematodes thoroughly so the solution drains down into the soil.
You may need several applications over a period of two or three years to fully control grubs and the subsequent June bugs, but, used correctly, nematodes are a very good control measure.
Apply Milky Spores
Another grub-control measure considered to be organic is milky spores, a bacterium that can be effective at controlling many types of grub beetles, including Japanese beetles. It depends on soil that is fairly warm, however, so it may not be the best choice for northern climates.
Fall is considered a good time for application since the grubs are usually fairly close to the surface at this time. Milky spores will not have much success if applied in the spring and summer or when the soil is too dry.
Milky spores are mixed with water, applied with a sprayer or as a granular powder, and then watered thoroughly. It may take several years of repeated treatment to bring severe infestations under control.
Apply a Curative Insecticide in September
Although it's always better to avoid chemical insecticides if possible, a serious grub and June bug infestation is one case in which insecticides may be necessary if you want to save your lawn. The most effective chemical remedy is to apply a product that contains carbaryl or trichlorfon in September. These are contact chemicals that will kill grubs and prevent them from pupating into adults. And, in September, the grubs are still close enough to the surface to be killed by the insecticide.
These are known as curative chemicals rather than preventative since they will kill the insects in all their life cycle phases. Applied in September, these insecticides will kill as many as 80 percent of the grubs, thereby greatly reducing the following year's June bug emergence.
Make sure to water in these chemicals thoroughly. Toxicity to humans and most animals is moderate but well documented. Carbaryl is toxic to fish, so avoid applying it where run-off to lakes and rivers is possible. Trichlorfon in large concentrations is a central nervous system stimulant and should be used cautiously. Immediate watering will remove the chemical from the surface and reduce the hazard.
Apply a Preventive Insecticide in June or July
Another option is to apply an insecticide containing imidacloprid, thiamethoxam, clothianidin, or chlorantraniliprole in early to midsummer. However, be aware that these are preventive insecticides that kill only the newly hatched grubs. They will not kill mature grubs, eggs, pupae, or burrowing beetles. Thus, timing is quite critical with these products; too early or too late, and their effectiveness is largely lost.
What Causes June Bugs?
June bugs will be more prevalent if your lawn has a heavy infestation of grubs, and the grubs themselves are more prevalent on lawns that are very thick with thatch. They can also be more prevalent in a landscape where lots of chemicals are used. The heavy use of surface pesticides can eliminate natural predators of June bugs and their larvae, and heavy applications of fertilizers make for very dense root systems that provide a banquet for grubs.
How to Prevent June Bugs
The easy answer is that preventing June bugs is largely a matter of controlling the larvae: the white grubs that dwell under the surface of lawns and gardens. Aside from the control measures described above, reducing your use of fertilizers and spray chemicals can help increase the number of natural predators that will kill grubs. Regular lawn dethatching may also help reduce lawn grub populations.
A landscape that is friendly to birds will also help, as larger birds will eat adult June beetles, and some species may dig up and eat the grubs. Large bats are nocturnal feeders that often consume June bugs. Finally, the presence of small predatory creatures such as toads and snakes can help control June bugs.
Do June Bugs Bite?
June bugs do not have the mouthparts necessary to bite humans or pets, though they do gnaw on plant parts. The legs of the insect are prickly and sticky, however, creating an unpleasant sensation when they land on your skin.
Are June Bugs Attracted to Light?
Light many night insects, June bugs are attracted to porch and yard lights. To reduce the number of insects, keep these light sources off during outdoor nighttime recreation.
Do June Bugs Eat Roses?
The common June bug, Phyllophaga longispina, does not feed on roses. However, the Japanese beetle, Popillia japonica, can seriously disfigure roses as well as many other ornamental and edible plants. Japanese beetles also produce grubs in their juvenile phase, which can be controlled in much the same way as common white grubs.
Japanese grubs, unlike June bugs, are highly active during the day. A common method of control is to pick them by hand and drown them in a container of water.