Professional Lawn Care
 
 

Billbugs burrow into grass stems


Adult billbug illustration

Billbugs

(crown & thatch inhabitant)

Adult billbugs are about 1/5" — 3/4" long. They are beetles with long snouts, or bills, that carry to the tip a pair of strong jaws or mandibles with which the beetles chew their food. Clay yellow to reddish brown to jet black in color. The beetles burrow in the grass stems near the surface of the soil and also feed on the leaves. Several species of billbugs damage lawns. The bluegrass billbug is a bluegrass pest. The Hunting Billbug causes damage to Zoysia grass.

Bill Bugs are found in 2 forms: adult and larvae (infant). The adult Bill Bugs look like a small beetle and are distinguishable by the long elephant-like bill that protrudes from their head. Hence the name. The adult Bill Bug feeds on grass stems above the surface. The younger Bill Bugs, or larvae, look like C-shaped, legless, wet pieces of white-rice and feed on grass roots.

Bill bugs cause the most damage when they are larvae, and can spread and destroy large sections of grass if not contained or killed.

Common signs of Bill Bug problems are dead spots on your lawn that don't recover from watering. Since the larvae feeds on the roots, you can also tell by pulling-up on the dead grass and see if it comes up easily from the roots. If so, it could be Bill Bugs.

Control Strategies

Billbugs are some of the most difficult turfgrass insects to control because the adults' armor-like bodies do not readily absorb insecticides. They also do not ingest much insecticide when they penetrate a grass stem while feeding. The larvae are also difficult to control because they are boring inside grass stems for much of their lives. Bluegrass billbugs seem to cluster in neighborhoods, especially where intensive bluegrass management is occurring.

Cultural Controls

Neighborhoods with mixed-grass lawns or lawns established using resistant varieties are often less severely attacked. Wise turf managers take time to observe all the turf in an area and watch for the beginnings of billbug attack in a neighborhood. Although bluegrass billbugs rarely fly, they may rapidly spread through continuous lawns of a neighborhood.

Varieties of turf resistant to billbug damage are available and should be considered when establishing a new lawn in an area with a history of billbug problems. Maintaining constant soil moisture and moderate fertility levels during the fall months into winter helps mask damage by low-moderate infestations.

Biological Control: Fungal Diseases

Billbug adults and larvae seem susceptible to the entomophagous fungus, Beauveria. However, this fungus rarely attacks enough billbugs to have a significant affect on the population. No commercial preparations of Beauveria are currently available for use on billbugs.

Biological Control: Parasitic Nematodes

The entomophagous nematodes, Steinernema carpocapsae, S. glaseri and several Heterorhabditis, have been used to infect billbug larvae in the laboratory and in small field trials. These nematodes show promise for the future but additional studies are needed to find the environmental conditions needed for consistent results.

Chemical Control: Spring Adults

This is the most commonly used strategy. Contact or stomach poisons are applied when adults come out of hibernation and are migrating in search of sites to lay their eggs. Studies show that adults become active when the soil surface temperature approaches 65 — 68 degrees F.

Repairing billbug damage

Billbugs attack bluegrass lawns (and occasionally tall fescue and perennial ryegrass) in June and feed on plant crowns and roots. If rainfall is adequate in late June and July, lawns often recover from a billbug attack. If rains don't occur, as happened this season, then we often attribute the browning to heat and dry conditions and assume the lawn is dormant. If in fact areas of the lawn are dead from a billbug infestation, renovation will be needed late this summer.

How do you know if the damage is drought related or actual billbug damage?

Do the "tug test" to determine if brown areas were killed by a billbug infestation. Grab a handful of the brown grass and give a gentle tug. If the brown grass comes lose easily and you find sawdust-like material at the base of the blades/stems, it's likely billbug injury. If large areas are injured, it will need to be repaired in the fall via reseeding or resodding.

Threshold: 1 per sq. foot