How to Control May and June Beetles

May and June beetles, also called June bugs, are lawn and garden scarab beetles known mostly for eating plants and ornamentals as adults and causing significant damage to turfgrass in their larval stage. Although they go by different names (May or June beetle), they actually make up a genus of about 300 species of beetles that are a part of the subfamily Melolonthinae (family Scarabaeidae, order Coleoptera). When most refer to the May or June beetle, they’re basically addressing the same beetle.

The May and June beetle are notorious pests located in the Northern Hemisphere. Often spotted in the late spring or early summer, the May and June beetle are named after the months they begin to appear. You may often see them flying across a light, or stuck in a window screen at night as they’re mostly nocturnal. They are clumsy flyers and can be heard flying into doors or windows.

What are May and June beetles?

As previously mentioned, the May or June beetle primarily belongs to the Scarabaeidae family along with chafers and Japanese beetles.

May and June beetles are known mostly for their larvae or damage to ornamentals and turfgrass. Adult May and June beetles eat plant leaves and ornamentals while their larvae, referred to as white grub worms, eat roots or other decaying plant material in the soil.

What does a May or June beetle look like?

May or June beetles aren’t the shiny green beetles you sometimes see around this time of year. Those are Japanese beetles. Although they’re closely related, the May or June beetle ranges from reddish-brown in color to almost black without any patterns like spots or stripes. 

They usually range from 0.5–1.0 inches in length and are slightly larger than the masked chafer, which is about 5/8–7/8 inches long. 

May and June beetle larvae, white grub worms, have the ability to completely destroy an entire lawn given the right amount of time if there are a significant number underneath the soil’s surface. Certain grub worm species live as a grub worm for only one year before becoming an adult beetle. Unfortunately, the May and June beetle’s larvae take about three years to complete their life cycle, wreaking havoc in lawns for a longer period of time.  

Their larvae are C-shaped, white or cream-colored worms with six legs located near the front of their bodies. They also have a brownish-red head.

Pictured above: A May/June beetle and its larvae.

What do May and June beetles look like?

These insects love eating plants. They are strictly herbivorous and eat ornamentals and tree and shrub leaves. This makes them a huge hazard for most gardens as the plants serve as a good source of nutrition.

May and June beetles also attract plenty of predators. These include snakes, skunks, moles and several others. 

What time of year to May and June beetles come out?

The May or June beetle emerges in late May and early June (hints its name). They tend to be active during the night and are attracted to lights. Once the adults mate, the females dig a few inches into the soil to deposit eggs.

There are different places where the female beetle can lay its eggs, but it mostly prefers doing this near a tree. These eggs then form grubs, which can dwell underground for 1–3 years as they pass through growth stages called “instars”. Each year, they become larger and more destructive.

Once they’ve reached their third year, the larvae starts to pupate in the soil around the late summer or fall. This is followed by their adult forms emerging the following spring and starting the cycle over. 

It’s not uncommon for overlapping generations to occur so that adults are spotted every year.

How do I identify a May or June beetle problem?

The best thing you can do to identify a May or June beetle is understand what they look like and symptoms of infestation. One of the easiest ways to determine if this insect is residing in your landscape is by digging up a small patch of dirt and visually spotting grub worms.

Another way to tell if grubs are present is by noticing brown patches of dead grass. The ground will often feel spongy and the grass will be easy to lift as if it were a piece of carpet. 

This does not always mean the grubs are specifically larvae of the May or June beetle though. 

Another idea could be to keep an eye on insect activity around any outdoor lights at night. You may be able to spot their adult forms.

Moreover, you should keep an eye for various predators like moles, skunks and snakes because all these creatures feed on the May and June beetle, indicating that your ground has them underneath the soil.

How do I treat a May or June beetle infestation?

Identifying and confirming May or June beetle presence is merely the first step towards a beetle-free lawn. You should clearly know where and how you can get rid of them. There are primarily two ways of clearing the beetle species from your lawn. These are as follows:

1. Cultural

2. Chemical

With either option, the key is to control the May or June beetle by attacking the grub before it becomes a serious issue. Try to end the infestation before the larvae turn into adult beetles and lay even more eggs. Although grub worms are more damaging, they’re easier to control. 

Cultural Treatment

Following are some cultural treatment options you can choose from:

• Use neem oil: Neem oil is a natural pesticide made from seeds of the neem tree. The primary active ingredient is known as Azadirachtin, and it’s a common choice for pesticide products. Neem oil works well against beetles as it can kill most of the adults. Follow application instructions found on product labels.
• Use beetle traps: Another option is to use high-quality beetle traps. However, beetle traps can also attract other species of beetles from outside your garden. This means that you may need to place several traps around your garden to distract intruders and stop them from making their way inside.

Some of the products listed below are labeled to trap Japanese beetles, however they work on May and June beetles as well.

Chemical Treatment

If cultural methods don’t seem to be working, chemical control may be more effective, however this should be used as a last result. As previously stated, the key to treating these beetles is to understand its life cycle.

To treat a currently existing May or June beetle problem, it’s best to make an insect control application when the grubs are feeding near the surface of the soil. If products are applied at any other times, they may be ineffective and serve as a waste of time and money. 

Grub worm feeding typically takes place in the spring starting in mid or late April through June. They also occur in the fall around August through October.

Some of the more effective products contain Chlorantraniliprole, Trichlorfon and Imidacloprid. Be wary of purchasing products labeled to treat grub worms that live for one year as these products may be ineffective on the species that live in the soil for multiple years. Dylox 6.2 is a great product to use on grubs as it will kill grubs in their second or third instar on contact. Scotts GrubEx contains Chlorantraniliprole, Dylox 6.2 contains Trichlorfon and both Merit 0.5 G and Merit 2F contain Imidacloprid. Click on the products below to learn more.

How do I prevent May or June beetles?

The best way to control May or June beetles is by killing them when they’re in their larval stage. With that being said, a great way to prevent them is by also preventing grub worms. 

Clemson University Entomologist, Dr. J.C. Chong says, “White grubs are much more effective to control by using preventative management meaning you want to apply a long residual insecticide in June or when scarab beetles start flying…if you make one application a year, you don’t have to worry about it for the rest of the year.”

May and June beetles are a huge concern for most U.S. homeowners. The adults damage ornamentals while the larva damages turfgrass. Now that you are more informed about the May and June beetle, you can begin coming up with effective prevention and treatment strategies in no time.

Sources:

• https://mdc.mo.gov/discover-nature/field-guide/may-beetles-june-bugs
• https://entomology.unl.edu/turfent/documnts/maybtls.shtml
• https://hort.extension.wisc.edu/articles/mayjune-beetles/
• https://extensionentomology.tamu.edu/insects/june-beetle/