Billbugs are funny-looking insects with a long snout and bent antennae. They may be funny looking, but it’s not funny when they start munching on your lawn. As with other lawn insects, there are a few simple and a few more involved ways to get rid of billbugs in your lawn. We’ve broken it down so you’ll know how to treat your lawn and make sure you get the last laugh.
What are billbugs?
Billbugs are a type of weevil (aka “snout beetle”) and are a member of the species Sphenophorus. At least eight of these weevils will damage turfgrass by munching on the crown and roots of your grass, making it a big concern for homeowners and grounds managers.
Here are a few common, grass-eating billbugs you may encounter, depending on where you live:
- Bluegrass billbug (Sphenophorus parvulus)
- Hunting billbug (Sphenophorus venatus)
- Lesser billbug (Sphenophorus minimus)
- Phoenix billbug (Sphenophorus phoeniciensis)
- Rocky Mountain billbug, aka Denver billbug (Sphenophorus cicatristriatus)
The good news is that no matter which species of billbug you have, the treatments are similar. The bluegrass and hunting billbugs are the most common in home lawns.
Fun fact: Billbugs are also called “snout beetles” because of a long, curved snout that extends from the front of the head.
Billbug life cycle
Adult billbugs lay eggs in the stems of grass in late spring/early summer. The larvae emerge a few days later and go through their five larval stages before they pupate (turn into a pupa) below the soil’s surface. In late summer, they emerge as adults, eat, and then overwinter in surface debris to emerge next spring and start the life cycle over again.
Most billbugs, including the common bluegrass billbug, produce one generation annually. Hunting billbugs produce one generation annually in the northern U.S., but up to two generations in some southern states.
Exception: There are some billbugs, such as the Rocky Mountain billbug, that overwinter as mature larvae or adults.
Lesser billbug: Various warm-season grasses, perennial ryegrass, fescues, and Kentucky bluegrass
Phoenix billbug: Bermuda, zoysia, fescues, ryegrass, Kentucky bluegrass
Rocky Mountain billbug (aka Denver billbug): Kentucky bluegrass (most common), perennial ryegrass, and sometimes other cool-season grasses
Size and appearance
Billbug adults range from gray to black in color. Their body is about ¼ to ½ inch long, and they have a long snout or beak with which they chew and two antennae that extend from their head. Larvae (the immature form) go through five larval stages and range from white to a cream color with a brown head. In their later larval stages, they can reach up to ½ inch long.
Billbug larvae and white grubs look very similar to the untrained eye, but they differ in appearance in a few ways.
|Billbug larvae||White grubs|
-Cream or white color with brown head
-Have no legs
-Body curves only slightly; look like “puffed rice”
-Gray in color with brown head
-Three pairs of legs
-Curl into a “C” shape
How to identify billbug damage in your lawn
Billbug damage mimics many other insect and disease issues, drought stress, and spring green-up:
- Grass is brown, tan, or yellow and appears to be dead
- Brown patches are long, round, or irregularly shaped
- Grass stems are hollow
- Grass is thinning
- Damage may be more pronounced at the edge of pavement, sidewalks, or driveways
Since billbug infestations can mimic damage from other turf problems, here are a few tests you can do to investigate further.
Do the tug test
Note: These next two tests (the tug test and digging into the soil) are best if you want to test for larvae.
A simple tug test can help you diagnose billbug damage in the lawn.
- Locate a damaged area of turf.
- Pull on a small section of the grass blades.
- If the grass pulls up easily with no roots attached, this could be billbugs. Also, look for sawdust-like material at the base of the grass. This is billbug frass (excrement).
Dig into the soil
If it looks like there is active feeding going on, you can dig into the soil (1-2 inches) to see if you find larvae to help confirm what the tug test has shown. Look for the white larvae right around the soil level and just below around the roots.
Note: The pavement crossing test, drench test, and pitfall traps are best for testing for adults.
Another fun way to “test” for the presence of billbugs in your lawn is to grab your lawn chair, sit in a shady area next to a paved surface, and wait. The adults will “cross over” from their overwintering sites across paved areas to the lawn once warm days arrive in late spring.
This “pavement crossing” will help you to determine if you need to treat the problem. If you spot at least two billbugs trotting over the pavement per minute, anticipate that you’ll see billbug damage in the lawn in about six weeks.
To test for adults in the lawn, use the drench test:
- Mark an area that is 1 square yard in size.
- Add 2-4 tablespoons of dishwashing soap to 1 gallon of water in a watering can.
- Pour the water evenly over the area. (If the soil is parched, use 2 gallons of water.)
- Wait 10 minutes.
- Count the number of billbugs that come to the surface.
- If you see as few as one billbug per square foot, it might be time to consider treatment options.
Go into the lawn at dusk in late spring and see if you can find adults scurrying on top of the grass. Or, use a pitfall trap to collect adults at night while they move around.
How to prevent billbug damage
If you’ve experienced billbugs biting on your grass in prior years, consider these options to minimize the damage going forward.
- Plant or overseed with endophyte-enhanced grass. Certain cultivars of fine fescue, perennial ryegrass, and tall fescue are endophyte-enhanced. These grasses harbor a fungus that is toxic to billbugs.
If you plant endophyte-enhanced grass, you won’t need to apply chemicals to the lawn. Or, if you overseed to the point where one-third of the grass is endophyte-enhanced, problems should be greatly reduced.
- Change your cultural practices. Overly managed lawns tend to have problems with insects or disease. To help control billbugs, fertilize and water regularly, but make sure you don’t overdo it.
Water deeply but infrequently, and reduce your fertilization to see if this makes a difference. Other common lawn maintenance chores, such as aeration and dethatching, also help create a healthy lawn that resists and discourages unwanted insects.
- Check sod before you install it. Check the roots, stems, and crowns on new sod for billbug activity.
How to get rid of billbugs
If you notice billbugs in the lawn or have a recurring problem that doesn’t respond to changes in watering or fertilization, consider these options.
- Beneficial nematodes can help homeowners manage billbug larvae in the lawn. Ohio State University reports that Heterorhabditis species, Steinernema carpocapsae and Steinernema glaseri have been used to control billbug larvae in small studies. Call a nematode supplier to inquire about which strains are best before you buy.
Timing is important. Beneficial nematodes should be applied when the larvae are young. Ask your local Extension Office for advice on correct timing in your area.
- Contact spraying is one option; however, the success rate is low. Adult beetles must be in the lawn when the insecticide is sprayed, or they have to eat the treated grass.
- Systemic insecticides, with active ingredients such as imidacloprid, are a more effective option. Systemic insecticides are taken up into the plant’s root system. As such, apply before the billbugs lay their eggs in late spring so that when hungry larvae emerge, the insecticide will protect the plant from being eaten.
Note: Imidacloprid and most systemic insecticides are toxic to beneficial insects, such as bees. Check the label or look up the main ingredients before you decide to spray to see what impact the chemical will have on local insects.
Remember, insecticides kill other insects and parasites that eat billbugs, so weigh these risks carefully. Insecticides, either contact or systemic, should be a last resort used only for heavy infestations after all other options have been exhausted.
If billbugs marching one by one across your lawn is more than you have time to handle, contact a Lawn Love lawn care pro. They have local knowledge and expertise to help control billbugs and other lawn pests in your area.