By Caroline Cox, 2006; Updated 2023
In dry parts of the Pacific Northwest residents are concerned about billbugs because this insect can cause dead spots in lawns as well as other damage. This page explains how to tell if billbugs are a problem in your lawn, and shares environmentally-friendly techniques to deal with billbugs if you need to take action.
Need expert advice for a tough pest problem? Get help here!
What Kinds of Damage Do Billbugs Cause?
Young billbug grubs cause grass stems to turn brown and die when they feed inside the stems.1 As they get older they damage grass roots. If you have a billbug problem in your lawn, you’ll see dry dead spots that are irregularly shaped.1 There are a variety of lawn problems that cause dead spots, so you’ll want to be sure that billbugs are actually your problem. When the lawn is damaged by billbugs, the grass becomes dry and loose; typically it can then be peeled back without much effort and the grubs will be visible.2
Serious billbug problems can happen in home lawns, and they can be very challenging for sod farms, golf courses and sports fields when they cause unattractive brown patches of grass.3
How to Prevent Billbug Problems
1. Resistant Grass Varieties
Probably the most straightforward way to prevent billbug problems is to grow varieties of grass that are not susceptible to billbugs. In general this means growing grasses with high levels of endophytic fungi. Endophytes are a type of fungus that naturally produce a compound that is toxic to billbugs. These natural chemicals kill many insect pests, including billbugs.3 Varieties of perennial rye grasses, fine fescues, and tall fescues with high levels of endophytes have been developed for home lawns.2 You can also fill in bare patches or protect your current grass from billbugs by overseeding with an endophytic grass variety.3 Certain Kentucky bluegrass varieties are resistant or tolerant to billbugs, including: ‘Park,' ‘Arista,' ‘NuDwarf,' ‘Delta,' ‘Kenblue', and ‘South Dakota Certified.'4
2. Modifying Your Lawn
Lawns that have been stressed by lack of water can be susceptible to billbug damage.1 Keep your lawn healthy by careful watering. For tips about how to water effectively and efficiently, see this article from NCAP.
Adult billbugs prefer lawns where they are protected from winter weather and predators. Lawns with thatch buildup, and lawns with nearby leaves, pine needles, or mulch provide protection for billbugs. You can remove these materials to make your lawn less attractive to billbugs.1
The adults also prefer to lay eggs near places that conserve heat in early spring: sidewalks, driveways, asphalt paths, and concrete or brick walls. The adults prefer sunny lawns for the same reason.2 If you have a persistent problem with billbugs you can think about modifying your landscape so you’re not growing grass near these warm areas.
3. Using Nematodes
A biological control that can be effective for controlling billbugs is using nematodes in the genera Steinernema (particularly Steinernema carpocapsae and Steinernema glaseri) and Heterorhabditis.4 Nematodes that prey on billbugs can be purchased from a number of commercial suppliers and can be used on a small scale. Check with local experts or the supplier about which species of nematode will work best in your area.4 Some tests have found that nematodes are more effective at killing billbugs than conventional insecticides, and golf courses in Japan have found that nematodes are more effective than other control measures.5
To make a nematode application effective, it is best to:
- Water the turf before applying the nematodes4
- Release nematodes late in the day to avoid direct sunlight4
- Water immediately after applying the nematodes, and keep the soil moist for the next 10 to 14 days4
- Handle the nematodes with care since they are living creatures, and check the expiration date on each package6
4. Using Fungus
Another method for managing billbugs is Beauveria bassiana, a fungus that causes disease and death in insects. The fungus is available commercially, but it has not been found to be very effective for large populations of billbugs (on a commercial scale).6
More Background Info On Billbugs
What Is a Billbug?
Billbugs are weevils in the family Curculionidae.4 The adult beetles have long snouts that point downwards. The adults are between 1/4 and 1/2 inch long4,6 and vary in color, from reddish brown to gray or black.2,6 They rarely fly, but they can crawl significant distances.4
Immature billbugs (larvae) are white or cream-colored, legless grubs with dark heads.4,6 They can grow to be 1/2 inch long.4 Young grubs feed inside grass stems, after they hatch from eggs inserted into the stems.4 When they are too large to feed inside stems, they move into root crowns or out into the soil, feeding on grass roots.4 You’ll probably notice “frass” (insect excrement) that looks like sawdust.4,6
Types of Billbugs
There are four kinds of billbugs that are most common in the Northwest U.S: bluegrass billbug (Sphenophorus parvulus), Denver billbug (Sphenophorus cicatristriatus), orchardgrass billbug (Sphenophorus venatus confluens), and Sphenophorus sayi (no common name).7 Management techniques apply to all of these species so you don’t need to know which kind of billbug is living in your lawn.
- Turfgrass entomology (billbugs). Lincoln, NE: University of Nebraska-Lincoln, Department of Entomology; undated [accessed 23 Jun 2023]. https://entomology.unl.edu/turfent/documnts/billbugs.shtml
- Salaiz T, Love SL, Bechinski EJ. Controlling billbug grubs in lawns, CIS 1204. Moscow, ID: University of Idaho Extension; Feb 2014 [accessed 23 Jun 2023]. https://www.uidaho.edu/-/media/UIdaho-Responsive/Files/Extension/publications/cis/cis1204.pdf?la=en
- Mertz L. New knowledge and a new tool to help control billbugs in turfgrass. Entomology Today; 2 May 2016 [accessed 23 Jun 2023]. https://entomologytoday.org/2016/05/02/new-knowledge-and-a-new-tool-billbugs-turfgrass/
- Shetlar DJ, Andon JE. Billbugs in turfgrass. Columbus, OH: Department of Entomology, The Ohio State University; 31 Jan 2012 [accessed 23 Jun 2023]. https://ohioline.osu.edu/factsheet/HYG-2502-12
- Prewal G. Using entomopathogenic nematodes for turfgrass pest management. Turfgrass Trends. May 2001;10(5):1-7. https://archive.lib.msu.edu/tic/tgtre/article/2001may1a.pdf
- McGraw B, Kline D. Billbugs. University Park, PA: PennState Extension; 5 May 2022 [accessed 23 Jun 2023]. https://extension.psu.edu/billbugs
- Kaur N, Donovan BC, Van Slambrook L, Walenta DL, Anderson NP. Understanding billbug species complex in grass seed production systems in western Oregon. Seed Production Research at Oregon State University. 2020; Ext/CrS 164:34-36. Accessed 27 Jun 2023. https://cropandsoil.oregonstate.edu/sites/agscid7/files/crop-soil/kaur_billbugs.pdf