Billbugs in the lawn...
The adult billbug (weevils) measures from one-quarter to three-quarters of an inch long and the head of these larva are brown to near black in color. They are fairly easy to recognize since their snouts are long and their mandibles (jaws) are quite strong for their size. The distinctive snout is what gives the adult billbug its name. There are four species of billbugs found in the Boise Valley and its thought that there is perhaps a fifth one here now. Probably the one that causes the greatest amount of damage here in Idaho is the bluegrass billbug, although all of them do sufficient damage. Many of the lawns in the Boise valley are either bluegrass or a combination of bluegrass, ryegrass and perhaps a fescue blend. Billbugs typically attack bluegrass, so if you have ryegrass or a fescue, you probably are not going to be bothered with billbugs, although they sometimes attack these types of sod also.
Adult billbugs have a rather hard shell. They typically lay their eggs in May to June, depending on weather conditions. This beetle has a dull, gray coloration and measures about 1/4" to 1/2" in length. An adult billbug will survive the winter by burying deep into the soil and as the weather warms, they come out the soil and consume your sod. Female billbugs lay their eggs in the soil and when they hatch, they too start consuming the roots of sod. Adult billbugs lay their eggs in the stems of bluegrass. Unlike some insects such as the coddling moth, billbugs typically lay only one generation each year. Although the adult billbug can create havoc to a lawn, it’s the larva that most often causes devastation in lawns as they feed on the crown and roots of sod. Adult billbugs do damage above the soil and the larva does its damage to the root system. The billbug larva looks like what most people think of as grubs, however they are legless and much smaller (about three-eighths of an inch long) and are typically found rolled up in the lawn soil. The head of the larva is bright orange in color. Damage is often not recognized as a billbug problem. Many folks believe that the lawn is simply not getting enough water. What’s really happening is that the larva are eating the roots of the sod, making it difficult for sod to survive as the weather heats up.
Just a thought worth keeping in mind. Another insect, the chinch bug creates the same appearance as the billbug. This insect chews the sod off at or near soil level, thus creating the same appearance as the billbug, both often fooling the homeowner into thinking it’s a watering problem. A quick way to tell if either of these insects is causing damage to the lawn is by simply lifting up on the sod. If it pulls up easily, most likely you have either billbug, chinch bugs or both.
Billbugs become most active when soil temperatures reach about 65 degrees, but we have found billbug larva actively eating the roots of sod as early as March. To control billbugs, apply Hi-Yield ‘Grub-Free Zone III’ twice each year, once in mid-March and again in mid-June. The bag states that a bag will last all season. Some folk’s think that means all summer, but that’s not the case. There are four seasons, spring, summer, fall and winter! Now you know why it takes two applications. One application will last approximately 3 months and billbugs actively feed from early spring through mid to late fall. Hi-Yield ‘Grub-Free Zone III’ must be watered in before the product becomes active. This can occur either by a sprinkler or rainfall. By doing so, it places the insecticide in the area where the billbug larva is feeding. There are other products that state they control billbugs, however we have found over the years that the product listed above work far better than any other means of controlling this insect. We should also note that it’s important to always check the label of all chemicals before applying, first to make sure the product is listed for controlling the insect you identified and second, to make sure you are following all precautionary measures listed on the container. It should be safe to allow pets and children back on the lawn within a day or two after thoroughly watering the product into the soil.
Some folks rely on beneficial nematodes which can kill around 200 +/- damaging, soil dwelling insects. And beneficial nematodes won’t kill or damage good insects such as ladybugs. The soil temperature must be 52 degrees or better for this to be an effective option.
Billbugs are often found in soil conditions that have been neglected. Even in the best of conditions, they often get their start near a walkway or driveway where the sod tends to dry out the quickest. If billbug damage is allowed to go unchecked, repair to the sod may be needed. This can be accomplished by overseeding or re-sodding in the fall.
The Home & Garden Store has the products to control billbugs, chinch bugs and a host of other insects. Stop by and see us. We can help you with all your gardening questions. The general manager has been solving insect problems for over 46 years right here in the Treasure Valley.