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Lawn grubs are the larval stage of adults insects like Japanese beetles, June beetles, or European chafers. They're small (up to about 1" in length), white, C-shaped creatures. They live just below the soil surface.
They're voracious little things. They feed on organic matter, primarily grass roots, and eventually causing brown or yellow patches of dying grass in your lawn.
Signs You Have Lawn Grubs
The telltale sign of grub damage is dead patches of grass. These areas may feel spongy or pull up easily like loose carpet. "Grab the brown spots with your hand," described Ace Hardware’s Home Expert, Lou Manfredini. "If you can lift it up like a toupee, then you have grubs."
Birds, raccoons, or skunks may have noticed the signs of grub activity before you do. (In their pursuit of a snack, they'll dig up your lawn.)
A healthy lawn can handle about five grubs per square foot, but you don't want it getting out of hand.
The best way to get a grip on grub activity is to use a chemical grub control product in the autumn. This is when grub feeding is at a high... which makes them much more susceptible to treatment.
Preventative vs. Curative Insecticides for Grubs
When it comes to lawn grub control, you’ll have two main options: preventative and curative insecticides.
- Preventative Insecticides: "The pre-emergent products help you to avoid a grub infestation in the first place," notes Manfredini. "Typically those go down in early June depending on where you live." Common active ingredients include imidacloprid and chlorantraniliprole. Preventative treatments are effective when timed correctly, before adult beetles lay new eggs. But they won’t help much if the white grubs are already actively feeding. "Sadly, once you have grubs, the damage is already done," he highlights.
- Curative Insecticides: "Using these types of insecticides can kill the active grubs and try and save some of the lawn from damage," shares Manfredini. Products with active ingredients like trichlorfon and carbaryl are best suited for curative applications. Keep in mind, curative treatments require immediate action once you notice the signs of damage.
How can I tell if the dead spots in my lawn are from grubs or something else?
Brown patches can come from drought, fungus, or pet urine, not just grubs. Try pulling up a small section of dead grass. If it lifts easily and you see C-shaped white grubs beneath, you'll know exactly who damaged the root system.
Do natural treatments work for grubs?
Natural grub treatments like biological controls can be effective under the right conditions, (i.e. sooner than later).
- Beneficial nematodes: microscopic worms are a pest control product that attacks grubs. (50 million?!)
- Milky spore: a bacterium that continues to kill Japanese beetle species grubs over time.
- And, overseeding: A natural preventive trick is to overseed in the late fall or early spring. It makes it harder for grubs to take hold of a lush lawn.
Keep in mind that natural solutions will take longer to get control of grubs and you'll risk more lawn damage the more time it takes.
Why to Control Grubs in the Fall
- Treatment is most effective. Combined with autumn rain, granular products will slowly seep into the soil, drawing out treatments and making them more effective.
- Less damage accumulates if you treat grubs before winter. Even moderate damage can make your lawn more vulnerable to weeds, disease, or drought stress.
- Fall treatments target larger grubs. This is when their appetites are highest and before they mature and produce more eggs.
- Prepares your lawn for winter dormancy, preventing weak spots where grubs have been feeding. You may want to over-seed the lawn to overcompensate for an existing grub population.
Do grubs come back every year?
Ugh, yes, those homebodies. Adult beetles usually return to lay new eggs in the same areas each summer. Keeping up with yearly prevention, like late-spring treatments and healthy lawn care, helps break the cycle.
Hire a Pro or DIY
Treatment of a grub infestation depends how severe it is.
If you have a minor problem and are willing to invest time in applying products correctly, DIY methods can be effective. This is especially true for preventive measures like general lawn care of introducing beneficial insects.
If you apply store-bought chemical lawn grub treatments, expect it to take 10-14 days after application for the grubs to die and longer still to see an improvement.
Lawn pest professionals obviously have more experience but also they often have access to stronger, more effective grub killer products.
What type of grass is most resistant to grub damage?
Thicker roots and faster growth can sometimes be more resilient to pest stress, but grubs aren't that picky when it comes to nutrition. "Grubs love those roots no matter what blend it is," joked Manfredini.
