What Causes Grubs in Your Lawn (+ How to Prevent Them)

Grubs are unavoidable if you have any sort of lawn or pasture. The problem is that they can cause or attract things that result in massive damage if their numbers get too high. Whether you have a grub infestation, just learned the signs of a lawn grub infestation, or you want to know what you can do to avoid every lawn problem possible, the following information can help you defend your lawn from an abundance of grubs.

Primary Causes of Grubs in a Lawn

What causes grubs in a lawn? The answer is, simply, ideal conditions for grubs to thrive. Sadly, most lawns fit that description. This is why most lawns have grubs. However, in most lawns, grubs are not and will likely never be a problem. Moist, well-aerated, rich soil with a healthy, light clay to loam consistency is the perfect climate for grubs. It’s also a best-case scenario for your lawn.

So what causes grubs to multiply and wreak havoc on some yards but not others?

Wet, Not Moist

Preventing lawn grubs can be as simple as not over-watering your lawn in the summer months. Grubs need quite a bit of moisture in the soil to thrive. Reducing the moisture that reaches the layer where the grubs live can reduce their numbers.

Short Grass = Short Roots

The roots of your grass will be about as long as the blades are allowed to grow. For example, if you cut your grass down to 2 inches every week, you’re likely to have roots of only 2 inches or less. If you allow your grass to grow up to 4 inches before cutting it down to 3 every few weeks, you’re likely to have roots of 4 inches in length.

Simply put, deeper roots mean that the grass is less damaged by grubs. But if you have shallow grass roots, it makes it easier for the grubs to live in the top 2 to 3 inches of soil, their preferred zone.

Aeration and Lack of Competition

Aeration is great for your lawn, but too many gaps without plant life can make it a little too easy for the beetles, grubs, and other insects to move around. It may also lead to overfeeding on the sparse plant life that does exist. The best thing to do in this scenario is to overseed each time you aerate. This helps introduce new, healthy competition and could discourage as many bugs from staying in a given area.

How to Prevent Lawn Grubs – Steps You Can Take

Preventing grubs isn’t easy. As it says above, nearly every lawn has a few grubs under it. The better strategy is to discourage grubs from thriving. This can take consistent effort over time, but it’s going to be a lot easier than ousting a full-on infestation and repairing the damage that infestation causes.

Prevent Egg Laying

The first thing you can do to prevent an infestation of grubs is to prevent the eggs that lead to grubs hatching on your property. The best way to do this is to discourage or kill any adult beetles around your yard. Fruit trees and trees that produce or excrete sweet sap will attract beetles. As will spilled sugar, soda, and beer.

There is one particular tried-and-true method to trap beetles of all kinds. A white 5-gallon bucket filled halfway up with water, plain or with some sugar or a few drops of dish soap added, will attract and eventually trap and drown dozens to hundreds of beetles in a day. Beetles may also be collected in the early morning, while they are sluggish or resting, and placed into the bucket to drown.

Use a Pesticide

While not an organic choice, pesticides that control grubs and grub eggs are highly effective. However, it’s important to keep in mind that these pesticides may also lower or eliminate your earthworm population. Use care when selecting and applying any pesticide to protect your health and that of your lawn.

Withhold Water

Grubs need moist or wet soil to thrive. By withholding water, the grubs will become dehydrated, lethargic, and eventually die of starvation or dehydration. It is much easier to withhold water for an extra day or two if you already follow an intermittent, deep watering schedule. A daily watering schedule is discouraged if you have any grub concerns.

Let Your Grass Grow Longer

Longer grass means longer grass roots and longer roots mean less damage and greater difficulty in moving around for grubs. The more gaps there are, the more likely a beetle is to lay eggs in the area. If there are no gaps and the roots of your grass are strong, it’s unlikely you will notice any grub damage.

Aerate and Overseed at the Same Time

As mentioned above, aeration can make it easier for grubs to move around and for beetles to lay eggs under your lawn. By overseeding in winter or spring after you aerate, you can fill gaps and provide new, strong plants to discourage grubs from moving into your yard.

Kill the Grubs, Not Your Lawn

It’s important to keep in mind that what your lawn needs and what beetles look for are often one and the same. Always give your lawn what it needs but keep an eye on your grub population. If your grub prevention plan requires you to restrict water, for example, only do so while your lawn looks lush and unstressed.

While restricting water can curb a grub population on the rise, fewer grubs won’t mean much if the lack of water results in a dry, dead lawn or just enough grass remaining for the surviving grubs to still do damage. This might seem like an unnecessary reminder, but it can be easy to focus too much on one goal when you’re facing a potential long-term problem like grubs.