One of the most misdiagnosed insect pests of cool season grasses is the Billbug Grub. They can be a serious pest of home lawns as well as golf courses, parks, athletic fields and just about anywhere turf-grass will grow.
There are 8 known species that will feed on various cool-season turf grasses. The grub itself is in the larva stage of an adult weevil. They do not have legs and are only about 1/8 – 3/8 of an inch long. They feed on the root systems of grasses just below the thatch layer. While the annual white grubs that cause so much damage to home lawns in the fall is much larger, sometimes reaching 2 inches in length and will have 6 legs.
The female lays her eggs in the stem of the grass plant near the crown. As the larva hatch, they will begin feeding on the grass blades at the base of the plant, but they quickly begin to feed down through the middle of the plant to get to the root systems. They will feed until mid-July. The adults will also feed on the grass blades, chewing notched-shaped holes in the middle of the blade or along the edges.
The damage they cause usually shows up in mid to late summer and is often confused with disease-damage or browning of a lawn that is often associated with summer dryness.
Try the “tug test” to determine if Billbugs are active:
- Look for grass that appears drought stressed, but with small brown patches.
- Grab the grass plant by the stem and give it a slight “tug”.
- If the plant pulls up easily, look at the base to see if there are small grains of sand-like material called frass, of insect droppings.
- If you search further you may actually find the small grub in the surrounding soil or even inside the stem of a grass plant.
Putting down an insect control would be the best thing to do if you find active Billbug Grubs in your lawn. There are several products labelled to control both the grubs and adults. It is best to check with your state’s Department of Agriculture Cooperative Extension Service for products that are labelled to control Bill Bugs in your state.
Depending on the extent of the damage, core aeration and overseeding may be necessary. This may be a task that is better suited for a professional lawn care company like Spring-Green. Contact your local Spring-Green to find a location nearest you.