Most people want lush, green lawns to adorn their homes. Unsightly brown patches can ruin the health and appearance of your lawn. There are many possible causes of brown patches in the lawn, everything from drought to over fertilizing. One of the most troublesome causes is the presence of grubs in the lawn. Diagnosing the problem requires a little observation before you can be sure those brown patches are the result of grubs.
How Do Grubs Create Brown Patches?
Grubs are the larval form of several types of beetles, including the Japanese beetle, European chafers and Oriental beetles. They live underground in the soil, where feed on the roots of grasses. Once they have ingested enough of the roots, the grass begins to wither and die, leaving unsightly brown patches in the lawn. Left unchecked, the grubs can destroy large areas in a matter of weeks, depending upon the density of the grub population. This type of damage usually shows up late in the summer.
Other Signs Grubs May Be Present
There are a number of animals that prefer to feed on grubs, and their presence should be noted as an indicator that your lawn may be providing their nourishment. Birds, particularly starling, dine on grubs. A number of starlings feeding in your lawn regularly may be an indicator of grubs. Raccoons, skunks and moles are also fond of grubs. Also, an abundance of beetles in May or June may be a good future indicator of potential grub problems.
Checking for Grubs
By the time you have noticed brown patches in the lawn, there is a good chance you have a grub infestation. Lift a section of the brown grass. If the grass does not lift away easily, indicating the roots are still intact, it may not be a grubs, but rather drought or another problem. If it comes away easily, it is a grub problem. Another way to check is to sample your lawn. Take 6-inch-by-6-inch samples across the lawn in a variety of places. Lift the grass away and check the soil and among the grass roots. If you have an average of three to 10 grubs in each sample, the lawn has a grub problem that requires treatment.
Milky Spore as Grub Control
Milky spore is a bacterium that lives in the soil. It is spread in a powdered form on the lawn by depositing 1 teaspoon every 4 feet in a checkerboard pattern. Once applied, water the lawn; this activates the bacteria and allows it to work down into the soil. The grub ingests the milky spore along with the soil and roots. The bacterium feeds on the grub, killing it within 7 to 21 days, and a new batch of the bacteria is released into the lawn. It can take up to 5 years to achieve full lawn coverage using milky spore.
Other Control Options
Chemical treatments such as liquid or dry formulations of trichiorfon, imidacloprid and halofenozide are effective; the first two are more useful as a preventative when used in June or July, and the latter once the grubs are present and feeding later in the summer. Nematodes such as heterorhabditis bacteriophoric are another organic treatment. They are worms that feed on grubs. They are mixed with water and applied with a sprayer to the lawn and provide a short-term but quick solution to a grub infestation.