Billbugs : Lawn Killers

  • by
cartoon billbug

Adult billbugs are approximately 1/5 to 3/4 inches long.  They are a type of beetle with a bill or long snout with strong mandibles or jaws, which the beetles use for chewing their food.  They range in color from jet black to reddish brown to clay yellow.  The beetles burrow into stems of grass at the soil’s surface.  They eat leaves of grass as well.  Several billbugs species cause damage to lawns.  The Hunting Billbug damages Zoysia grass, while the bluegrass billbug bothers bluegrass.

There are two forms of billbugs: larva (infant) and adult.  Adult billbugs resemble a small beetle.  They can be distinguished by their elephant-like bill protruding from their heads.  An adult billbug feeds on stems of grass above ground.  The larvae, or younger billbugs, have a legless, C-shaped form and look like pieces of wet white rice.  They feed on the roots of grass.

The most damage caused by billbugs occurs when they are at the larvae stage.  They can spread and end up destroying large grass areas if they are not killed or contained.

Common signs of a billbug problem are a lawn with dead spots that don’t come back after they have been watered.  Larva feeds on roots.  So another way you can tell is to pull up dead grass.  If it easily comes up by the roots, there might be a billbug problem.

Control Strategies

Billbugs are among the hardest turfgrass insects to get under control.  The armor-like bodies of the adult billbugs do not absorb insecticides readily.  Also, they don’t tend to ingest a lot of insecticides while feeding on grass stems.  It is also hard to control the larvae.  For most of their lives, they are burrowed inside grass stems.  Bluegrass billbugs appear to cluster inside neighborhoods, particularly when there is bluegrass management happening.

Cultural Controls – Neighborhoods that have established lawns with resistant varieties or mixed-grass lawns are not attacked as severely.  Smart managers of turf take the time to inspect all the grass in one area and look for the start of a billbug attack inside the neighborhood.  Bluegrass billbugs don’t fly too often.  However, they can spread rapidly across a neighborhood’s continuous lawns.

Biological Control with Fungal Diseases –  Billbug larvae and adults appear to be susceptible to Beauveria, an entomophagous fungus.  However, it is rare for the fungus to attack enough of the billbugs for it to significantly affect the population.  Currently, there are no Beauveria commercial preparations available to use on billbugs.

Biological Control with Parasitic Nematodes– There are several different entomophagous nematodes (Amazon link), including several Heterorhabditis, S. glaseri, and Steinernema carpocapsae that have been used for infecting larvae billbugs for small field trials and in the lab.  The nematodes appear to be promising for future use.  However, more studies need to be undertaken to discover what environmental conditions are necessary to get consistent results.

Chemical Control in Spring Adults – The strategy that is most commonly used.  Stomach or contact poisons are applied as adults come out of their hibernation and migrate to look for places to lay their eggs.  According to studies, adults become active after the temperature of the soil surface reaches 65 to 67 degrees F.

How To Repair Damage Caused By Billbugs

In June is when billbugs attack lawns made of bluegrass (and sometimes perennial ryegrass and tall fescue).  They feed on roots and plant crowns.  If there is enough rainfall in June and July, the lawns are often able to recover from billbug attacks.  If there isn’t any rain, we often think the browning of the lawn is due to dry conditions and heat and assume the lawn has gone dormant.  However, some of the lawn areas are dead due to an infestation of billbugs.  Late in the summer, renovation will be necessary.

How Can You Tell Whether Damage Has Been Caused By Billbugs Or is Related to Drought

Try the “tug test” to figure out whether the brown areas in the lawn are dead due to the infestation of billbugs.  Grab the brown grass with your hand and gently tug on it.  If the grass easily comes loose and there is sawdust-like material on the bases of the stems and blades, it is probably damage caused by billbugs.  If large areas of the grass have been damaged, it will be necessary to repair the lawn in the fall by re-sodding or reseeding.

There are varieties of grass that are resistant to billbugs.  When starting a new lawn, they should be considered for areas that have historically had problems with billbugs.  Maintaining moderate fertility levels and constant soil moisture during the fall and winter will help mask damage caused by low to moderate infestations.

Leave a Reply

Your email address will not be published. Required fields are marked *