How To Tell if Lawn Grubs Are Actually a Problem for Your Lawn

As lawn pest control experts, we commonly hear from clients about their concerns with grubs on their lawn. We often have to tell them all the same thing – grubs are often not the root of your lawn’s problems. In our service area around College Station, lawn grubs are usually blamed for issues stemming from other pests or a lack of nutrients. One grub on your lawn is not something to be alarmed about, and keeping your lawn healthy can often be enough to keep them away.

However, if you think they could be the source of your problems, read on to see how to check for grubs and how to treat them.

Background on Grubs

Grubs are the larval stage of a variety of beetles. Beetles will find attractive lawns where they can lay their eggs during the summer. They look for lawns that are overwatered, thin, and generally weaker. When their eggs hatch, the grubs start to feed on the roots of grass during the late summer and fall. At first they are tiny, typically around 1/8 to 1/4 of an inch in length. Some types will overwinter when it gets cold and continue to feed in late spring. Once they mature into beetles, they start laying more eggs and continue the cycle.

Typically, grubs are a creamy white color, though they might be more yellowed or darker if they are older. They have brown heads and six distinct legs on their fleshy, C-shaped body. Different species of beetle larvae grow to different sizes. It is important when treating grubs to identify the species correctly, because some pest control measures will only work for certain species of grubs. Japanese Beetle grubs grow to about an inch in length. Southern Masked Chafers are a similar size. These two species are especially common around the Houston area. European Chafers tend to be slightly smaller than Japanese Beetle grubs while June Beetle grubs are larger – some types like Green June Beetles can grow up to 2 inches.

Image Source: University of Maryland

When Grubs Are Harmless

Insects that eat the roots of your grass understandably threaten your lawn. However, it’s important to try and gauge if they’re the root of problems before you take action. Generally the best way to check your lawn for grubs is to dig up the grass and check. With a shovel or garden spade, lift your turf in a one foot square where you suspect infestation and dig 2-4 inches deep. Check the soil and the roots of your grass and count the number of grubs that you see.

Image Source: Michigan State University

For some species of bugs or lawn fungus, the first sign of an issue should immediately prompt treatment. However, finding a grub or two on your lawn does not warrant the same level of concern. One grub would not be able to eat enough roots across your whole lawn to do significant damage. If you find less than 5 grubs in one square foot, it’s likely that using pesticide would do more harm to your lawn in the long run. Instead, if you’re concerned, you can take preventative measures to deter beetles from laying eggs on your lawn in the future. If your lawn is distressed with no signs of pests, look into your mowing, watering, or fertilization habits.

When Grubs Become a Problem

If you find 5-10 grubs or more in one square foot of your lawn, this might be a sign of a larger infestation. Not only is this a more significant number, but this shows that conditions are ideal for beetles to continue laying eggs across your lawn. If you reach this level of infestation, it’s worth it to look into treatment.

You can also seek out treatment if your lawn is showing signs of distress specific to grubs. Grub-infested lawns will have very loose sod because the roots of the grass are gone. You’ll be able to lift grass or roll it back like a carpet. When you check the lifted grass, the roots will be severed or gone completely. When you walk across these affected parts, it will feel spongy underfoot. You may also have irregular patches of yellowing or wilting grass that will not respond to watering. There might also be activity from larger pests, such as birds, raccoons, skunks, and even feral hogs that want to dig up your lawn and eat these grubs. Some of these symptoms might be the result of a different kind of pest. If you notice this on your lawn, regardless of the cause, it’s worth looking into treatment.

Image Source: Neil Sperry

How to Treat Lawn Grubs

When treating grubs, it’s important to distinguish between preventative pest control and pest control to treat a current infestation. Preventative pest control is worth looking into for a small number or grubs or to halt reinfestation, which is common. Here are some of the best ways to control or prevent grubs across your lawn.

Insecticide

For a current grub issue, insecticide is an effective way to quickly kill them off across your lawn. These should be applied during the late summer and fall, when it’s likely all eggs have hatched and when grubs are actively feeding. Make sure to look for non-toxic pesticides and to carefully apply across your lawn according to the pesticide instructions. Improper use might harm already-weakened lawns or deter beneficial birds and bugs that eat grubs. 

Preventative kinds of insecticide are best applied during the late spring and early summer right before eggs start to hatch. The main active ingredients should include imidacloprid, chlorantraniliprole, or thiamethoxam. Like with any insecticide, follow the instructions on the product and try to prevent overuse.

Nematodes

Image Source: Agriculture and Natural Resources, University of California

This treatment sold as pest control is a biological, environmentally-friendly solution that can be used to prevent or to treat infestation. Nematodes are microscopic, worm-like organisms that feed off of grubs. When grubs eat them, they produce toxins while in the digestive tract that kill off grubs in 1-2 days. Then, they feed and reproduce from the grub and spread throughout the soil without harming grass.

It’s best to apply nematodes when grubs would be feeding in late summer or early fall. The best time is during the evening or on a cloudy day when UV levels are lower. The soil should be watered before and after application. After watering, use a sprayer or watering can to apply the nematodes evenly across the lawn as instructed on the package.

Milky Spore

Image Source: Bugwood.org

Milky spore takes a few years to implement, but if you are worried about grubs on your lawn in the future it’s a good preventative measure. This is actually a specific disease that impacts grubs without harming your lawn or other insects. After it’s applied, it will grow in the soil and target grubs specifically. Grubs that eat the spores will die off as the bacteria reproduces, allowing the bacteria to be released back into the soil and spread. It takes a while to establish on your lawn, but once it does, it can help control the presence of grubs for years. 

When applying milky spore, make sure that you identified the type of grub that is infesting your lawn. Milky spore has many variants, and each kind targets a certain species of grub – for example, Bacillus popilliae will only specifically target Japanese beetle grubs. It usually comes in a powder form and should be spread across your lawn evenly in a grid pattern. After application and following any other package directions, water your lawn to help them thrive.

Lawn Treatment for Future Prevention

While these preventative methods can be important, the best way to prevent grub damage on your lawn is to keep it healthy and unappealing to pests. Looking out for your lawn’s health can also help your lawn heal after a grub infestation. A good tip to deter grubs is to avoid overwatering, as beetles try to lay their eggs in damp soil. Fertilization can help your turf to grow thicker and stronger, and aerating the lawn can help improve the soil structure and help roots regrow deeper than before. Regular maintenance can be one of the best ways to manage grubs. Checking regularly for grubs after an infestation is also helpful.

Review and Treatment from the Professionals

It sounds simple enough when written out, but performing accurate grub care on your own is difficult, especially for identifying different types of grubs. The professionals at The Fertilizer Guy have experience controlling grubs on lawns all across the College Station and Bryan area. We can treat a problem or give you advice on the root of your lawn’s issues. If you think you’d be interested in our services, contact us today for a consultation!